< draft-ietf-pkix-new-part1-02.txt   draft-ietf-pkix-new-part1-03.txt >
PKIX Working Group R. Housley (SPYRUS) PKIX Working Group R. Housley (SPYRUS)
Internet Draft W. Ford (VeriSign) Internet Draft W. Ford (VeriSign)
W. Polk (NIST) W. Polk (NIST)
D. Solo (Citigroup) D. Solo (Citigroup)
expires in six months July 14, 2000 expires in six months November, 2000
Internet X.509 Public Key Infrastructure Internet X.509 Public Key Infrastructure
Certificate and CRL Profile Certificate and CRL Profile
<draft-ietf-pkix-new-part1-02.txt> <draft-ietf-pkix-new-part1-03.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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3.4 Operational Protocols ..................................... 14 3.4 Operational Protocols ..................................... 14
3.5 Management Protocols ...................................... 14 3.5 Management Protocols ...................................... 14
4 Certificate and Certificate Extensions Profile .............. 15 4 Certificate and Certificate Extensions Profile .............. 15
4.1 Basic Certificate Fields .................................. 16 4.1 Basic Certificate Fields .................................. 16
4.1.1 Certificate Fields ...................................... 17 4.1.1 Certificate Fields ...................................... 17
4.1.1.1 tbsCertificate ........................................ 17 4.1.1.1 tbsCertificate ........................................ 17
4.1.1.2 signatureAlgorithm .................................... 17 4.1.1.2 signatureAlgorithm .................................... 17
4.1.1.3 signatureValue ........................................ 18 4.1.1.3 signatureValue ........................................ 18
4.1.2 TBSCertificate .......................................... 18 4.1.2 TBSCertificate .......................................... 18
4.1.2.1 Version ............................................... 18 4.1.2.1 Version ............................................... 18
4.1.2.2 Serial number ......................................... 18 4.1.2.2 Serial number ......................................... 19
4.1.2.3 Signature ............................................. 19 4.1.2.3 Signature ............................................. 19
4.1.2.4 Issuer ................................................ 19 4.1.2.4 Issuer ................................................ 19
4.1.2.5 Validity .............................................. 22 4.1.2.5 Validity .............................................. 23
4.1.2.5.1 UTCTime ............................................. 23 4.1.2.5.1 UTCTime ............................................. 23
4.1.2.5.2 GeneralizedTime ..................................... 23 4.1.2.5.2 GeneralizedTime ..................................... 23
4.1.2.6 Subject ............................................... 23 4.1.2.6 Subject ............................................... 24
4.1.2.7 Subject Public Key Info ............................... 24 4.1.2.7 Subject Public Key Info ............................... 25
4.1.2.8 Unique Identifiers .................................... 25 4.1.2.8 Unique Identifiers .................................... 25
4.1.2.9 Extensions ............................................. 25 4.1.2.9 Extensions ............................................. 25
4.2 Certificate Extensions .................................... 26 4.2 Certificate Extensions .................................... 26
4.2.1 Standard Extensions ..................................... 26 4.2.1 Standard Extensions ..................................... 26
4.2.1.1 Authority Key Identifier .............................. 26 4.2.1.1 Authority Key Identifier .............................. 27
4.2.1.2 Subject Key Identifier ................................ 27 4.2.1.2 Subject Key Identifier ................................ 27
4.2.1.3 Key Usage ............................................. 28 4.2.1.3 Key Usage ............................................. 28
4.2.1.4 Private Key Usage Period .............................. 30 4.2.1.4 Private Key Usage Period .............................. 30
4.2.1.5 Certificate Policies .................................. 30 4.2.1.5 Certificate Policies .................................. 31
4.2.1.6 Policy Mappings ....................................... 33 4.2.1.6 Policy Mappings ....................................... 33
4.2.1.7 Subject Alternative Name .............................. 33 4.2.1.7 Subject Alternative Name .............................. 34
4.2.1.8 Issuer Alternative Name ............................... 36 4.2.1.8 Issuer Alternative Name ............................... 36
4.2.1.9 Subject Directory Attributes .......................... 36 4.2.1.9 Subject Directory Attributes .......................... 37
4.2.1.10 Basic Constraints .................................... 36 4.2.1.10 Basic Constraints .................................... 37
4.2.1.11 Name Constraints ..................................... 37 4.2.1.11 Name Constraints ..................................... 38
4.2.1.12 Policy Constraints ................................... 39 4.2.1.12 Policy Constraints ................................... 40
4.2.1.13 Extended key usage field ............................. 40 4.2.1.13 Extended key usage field ............................. 41
4.2.1.14 CRL Distribution Points .............................. 41 4.2.1.14 CRL Distribution Points .............................. 42
4.2.1.15 Inhibit Any-Policy ................................... 42 4.2.1.15 Inhibit Any-Policy ................................... 43
4.2.1.16 Freshest CRL ......................................... 43 4.2.1.16 Freshest CRL ......................................... 43
4.2.2 Internet Certificate Extensions ......................... 43 4.2.2 Internet Certificate Extensions ......................... 44
4.2.2.1 Authority Information Access .......................... 43 4.2.2.1 Authority Information Access .......................... 44
5 CRL and CRL Extensions Profile .............................. 45 4.2.2.2 Subject Information Access ............................ 45
5.1 CRL Fields ................................................ 45 5 CRL and CRL Extensions Profile .............................. 47
5.1.1 CertificateList Fields .................................. 46 5.1 CRL Fields ................................................ 47
5.1.1.1 tbsCertList ........................................... 46 5.1.1 CertificateList Fields .................................. 48
5.1.1.2 signatureAlgorithm .................................... 46 5.1.1.1 tbsCertList ........................................... 48
5.1.1.3 signatureValue ........................................ 47 5.1.1.2 signatureAlgorithm .................................... 48
5.1.2 Certificate List "To Be Signed" ......................... 47 5.1.1.3 signatureValue ........................................ 49
5.1.2.1 Version ............................................... 47 5.1.2 Certificate List "To Be Signed" ......................... 49
5.1.2.2 Signature ............................................. 47 5.1.2.1 Version ............................................... 49
5.1.2.3 Issuer Name ........................................... 47 5.1.2.2 Signature ............................................. 49
5.1.2.4 This Update ........................................... 48 5.1.2.3 Issuer Name ........................................... 50
5.1.2.5 Next Update ........................................... 48 5.1.2.4 This Update ........................................... 50
5.1.2.6 Revoked Certificates .................................. 48 5.1.2.5 Next Update ........................................... 50
5.1.2.7 Extensions ............................................ 49 5.1.2.6 Revoked Certificates .................................. 51
5.2 CRL Extensions ............................................ 49 5.1.2.7 Extensions ............................................ 51
5.2.1 Authority Key Identifier ................................ 49 5.2 CRL Extensions ............................................ 51
5.2.2 Issuer Alternative Name ................................. 49 5.2.1 Authority Key Identifier ................................ 51
5.2.3 CRL Number .............................................. 50 5.2.2 Issuer Alternative Name ................................. 52
5.2.4 Delta CRL Indicator ..................................... 50 5.2.3 CRL Number .............................................. 52
5.2.5 Issuing Distribution Point .............................. 52 5.2.4 Delta CRL Indicator ..................................... 52
5.2.6 Freshest CRL ............................................ 53 5.2.5 Issuing Distribution Point .............................. 54
5.3 CRL Entry Extensions ...................................... 53 5.2.6 Freshest CRL ............................................ 55
5.3.1 Reason Code ............................................. 53 5.3 CRL Entry Extensions ...................................... 55
5.3.2 Hold Instruction Code ................................... 54 5.3.1 Reason Code ............................................. 56
5.3.3 Invalidity Date ......................................... 54 5.3.2 Hold Instruction Code ................................... 56
5.3.4 Certificate Issuer ...................................... 55 5.3.3 Invalidity Date ......................................... 57
6 Certificate Path Validation ................................. 55 5.3.4 Certificate Issuer ...................................... 57
6.1 Basic Path Validation ..................................... 56 6 Certificate Path Validation ................................. 58
6.1.1 Inputs ................................................... 58 6.1 Basic Path Validation ..................................... 58
6.1.2 Initialization ........................................... 59 6.1.1 Inputs ................................................... 61
6.1.3 Basic Certificate Processing ............................. 62 6.1.2 Initialization ........................................... 62
6.1.4 Preparation for Certificate i+1 .......................... 67 6.1.3 Basic Certificate Processing ............................. 65
6.1.5 Wrap-up procedure ........................................ 70 6.1.4 Preparation for Certificate i+1 .......................... 70
6.1.6 Outputs .................................................. 71 6.1.5 Wrap-up procedure ........................................ 73
6.2 Extending Path Validation ................................. 71 6.1.6 Outputs .................................................. 74
6.3 CRL Validation ............................................ 72 6.2 Extending Path Validation ................................. 75
6.3.1 Revocation Inputs ....................................... 72 6.3 CRL Validation ............................................ 75
6.3.2 Initialization and Revocation State Variables ........... 72 6.3.1 Revocation Inputs ....................................... 76
6.3.3 CRL Processing .......................................... 73 6.3.2 Initialization and Revocation State Variables ........... 76
7 References .................................................. 75 6.3.3 CRL Processing .......................................... 77
8 Intellectual Property Rights ................................ 77 7 References .................................................. 79
9 Security Considerations ..................................... 77 8 Intellectual Property Rights ................................ 81
Appendix A. ASN.1 Structures and OIDs ......................... 81 9 Security Considerations ..................................... 81
A.1 Explicitly Tagged Module, 1988 Syntax ...................... 81 Appendix A. ASN.1 Structures and OIDs ......................... 84
A.2 Implicitly Tagged Module, 1988 Syntax ...................... 94 A.1 Explicitly Tagged Module, 1988 Syntax ...................... 84
Appendix B. ASN.1 Notes ....................................... 101 A.2 Implicitly Tagged Module, 1988 Syntax ...................... 97
Appendix C. Examples .......................................... 102 Appendix B. ASN.1 Notes ....................................... 104
C.1 Certificate ............................................... 103 Appendix C. Examples .......................................... 105
C.2 Certificate ............................................... 106 C.1 Certificate ............................................... 106
C.3 End-Entity Certificate Using RSA .......................... 109 C.2 Certificate ............................................... 108
C.4 Certificate Revocation List ............................... 112 C.3 End-Entity Certificate Using RSA .......................... 112
Appendix D. Author Addresses .................................. 114 C.4 Certificate Revocation List ............................... 115
Appendix E. Full Copyright Statement .......................... 114 Appendix D. Author Addresses .................................. 117
Appendix E. Full Copyright Statement .......................... 117
1 Introduction 1 Introduction
This specification is one part of a family of standards for the X.509 This specification is one part of a family of standards for the X.509
Public Key Infrastructure (PKI) for the Internet. This specification Public Key Infrastructure (PKI) for the Internet. This specification
is a standalone document; implementations of this standard may is a standalone document; implementations of this standard may
proceed independent from the other parts. proceed independent from the other parts.
This specification profiles the format and semantics of certificates This specification profiles the format and semantics of certificates
and certificate revocation lists for the Internet PKI. Procedures and certificate revocation lists for the Internet PKI. Procedures
are described for processing of certification paths in the Internet are described for processing of certification paths in the Internet
environment. Encoding rules are provided for popular cryptographic environment. Encoding rules are provided for popular cryptographic
algorithms. Finally, ASN.1 modules are provided in the appendices algorithms. Finally, ASN.1 modules are provided in the appendices
for all data structures defined or referenced. for all data structures defined or referenced.
The specification describes the requirements which inspire the crea- The specification describes the requirements which inspire the
tion of this document and the assumptions which affect its scope in creation of this document and the assumptions which affect its scope
Section 2. Section 3 presents an architectural model and describes in Section 2. Section 3 presents an architectural model and
its relationship to previous IETF and ISO/IEC/ITU standards. In par- describes its relationship to previous IETF and ISO/IEC/ITU
ticular, this document's relationship with the IETF PEM specifica- standards. In particular, this document's relationship with the IETF
tions and the ISO/IEC/ITU X.509 documents are described. PEM specifications and the ISO/IEC/ITU X.509 documents are described.
The specification profiles the X.509 version 3 certificate in Section The specification profiles the X.509 version 3 certificate in Section
4, and the X.509 version 2 certificate revocation list (CRL) in Sec- 4, and the X.509 version 2 certificate revocation list (CRL) in
tion 5. The profiles include the identification of ISO/IEC/ITU and Section 5. The profiles include the identification of ISO/IEC/ITU
ANSI extensions which may be useful in the Internet PKI. The profiles and ANSI extensions which may be useful in the Internet PKI. The
are presented in the 1988 Abstract Syntax Notation One (ASN.1) rather profiles are presented in the 1988 Abstract Syntax Notation One
than the 1994 syntax used in the ISO/IEC/ITU standards. (ASN.1) rather than the 1994 syntax used in the ISO/IEC/ITU
standards.
This specification also includes path validation procedures in Sec- This specification also includes path validation procedures in
tion 6. These procedures are based upon the ISO/IEC/ITU definition, Section 6. These procedures are based upon the ISO/IEC/ITU
but the presentation assumes one or more self-signed trusted CA cer- definition, but the presentation assumes one or more self-signed
tificates. Implementations are required to derive the same results trusted CA certificates. Implementations are required to derive the
but are not required to use the specified procedures. same results but are not required to use the specified procedures.
Procedures for identification and encoding of public key materials Procedures for identification and encoding of public key materials
and digital signatures are defined in [PKIX ALGS]. Implementations of and digital signatures are defined in [PKIX ALGS]. Implementations of
this specification are not required to use any particular crypto- this specification are not required to use any particular
graphic algorithms. However, conforming implementations which use cryptographic algorithms. However, conforming implementations which
the algorithms identified in [PKIX ALGS] are required to identify and use the algorithms identified in [PKIX ALGS] are required to identify
encode the public key materials and digital signatures as described and encode the public key materials and digital signatures as
in that specification. described in that specification.
Finally, three appendices are provided to aid implementers. Appendix Finally, three appendices are provided to aid implementers. Appendix
A contains all ASN.1 structures defined or referenced within this A contains all ASN.1 structures defined or referenced within this
specification. As above, the material is presented in the 1988 specification. As above, the material is presented in the 1988
Abstract Syntax Notation One (ASN.1) rather than the 1994 syntax. Abstract Syntax Notation One (ASN.1) rather than the 1994 syntax.
Appendix B contains notes on less familiar features of the ASN.1 Appendix B contains notes on less familiar features of the ASN.1
notation used within this specification. Appendix C contains notation used within this specification. Appendix C contains
examples of a conforming certificate and a conforming CRL. examples of a conforming certificate and a conforming CRL.
2 Requirements and Assumptions 2 Requirements and Assumptions
The goal of this specification is to develop a profile to facilitate The goal of this specification is to develop a profile to facilitate
the use of X.509 certificates within Internet applications for those the use of X.509 certificates within Internet applications for those
communities wishing to make use of X.509 technology. Such applica- communities wishing to make use of X.509 technology. Such
tions may include WWW, electronic mail, user authentication, and applications may include WWW, electronic mail, user authentication,
IPsec. In order to relieve some of the obstacles to using X.509 cer- and IPsec. In order to relieve some of the obstacles to using X.509
tificates, this document defines a profile to promote the development certificates, this document defines a profile to promote the
of certificate management systems; development of application tools; development of certificate management systems; development of
and interoperability determined by policy. application tools; and interoperability determined by policy.
Some communities will need to supplement, or possibly replace, this Some communities will need to supplement, or possibly replace, this
profile in order to meet the requirements of specialized application profile in order to meet the requirements of specialized application
domains or environments with additional authorization, assurance, or domains or environments with additional authorization, assurance, or
operational requirements. However, for basic applications, common operational requirements. However, for basic applications, common
representations of frequently used attributes are defined so that representations of frequently used attributes are defined so that
application developers can obtain necessary information without application developers can obtain necessary information without
regard to the issuer of a particular certificate or certificate revo- regard to the issuer of a particular certificate or certificate
cation list (CRL). revocation list (CRL).
A certificate user should review the certificate policy generated by A certificate user should review the certificate policy generated by
the certification authority (CA) before relying on the authentication the certification authority (CA) before relying on the authentication
or non-repudiation services associated with the public key in a par- or non-repudiation services associated with the public key in a
ticular certificate. To this end, this standard does not prescribe particular certificate. To this end, this standard does not
legally binding rules or duties. prescribe legally binding rules or duties.
As supplemental authorization and attribute management tools emerge, As supplemental authorization and attribute management tools emerge,
such as attribute certificates, it may be appropriate to limit the such as attribute certificates, it may be appropriate to limit the
authenticated attributes that are included in a certificate. These authenticated attributes that are included in a certificate. These
other management tools may provide more appropriate methods of con- other management tools may provide more appropriate methods of
veying many authenticated attributes. conveying many authenticated attributes.
2.1 Communication and Topology 2.1 Communication and Topology
The users of certificates will operate in a wide range of environ- The users of certificates will operate in a wide range of
ments with respect to their communication topology, especially users environments with respect to their communication topology, especially
of secure electronic mail. This profile supports users without high users of secure electronic mail. This profile supports users without
bandwidth, real-time IP connectivity, or high connection availabil- high bandwidth, real-time IP connectivity, or high connection
ity. In addition, the profile allows for the presence of firewall or availability. In addition, the profile allows for the presence of
other filtered communication. firewall or other filtered communication.
This profile does not assume the deployment of an X.500 Directory This profile does not assume the deployment of an X.500 Directory
system. The profile does not prohibit the use of an X.500 Directory, system. The profile does not prohibit the use of an X.500 Directory,
but other means of distributing certificates and certificate revoca- but other means of distributing certificates and certificate
tion lists (CRLs) may be used. revocation lists (CRLs) may be used.
2.2 Acceptability Criteria 2.2 Acceptability Criteria
The goal of the Internet Public Key Infrastructure (PKI) is to meet The goal of the Internet Public Key Infrastructure (PKI) is to meet
the needs of deterministic, automated identification, authentication, the needs of deterministic, automated identification, authentication,
access control, and authorization functions. Support for these ser- access control, and authorization functions. Support for these
vices determines the attributes contained in the certificate as well services determines the attributes contained in the certificate as
as the ancillary control information in the certificate such as pol- well as the ancillary control information in the certificate such as
icy data and certification path constraints. policy data and certification path constraints.
2.3 User Expectations 2.3 User Expectations
Users of the Internet PKI are people and processes who use client Users of the Internet PKI are people and processes who use client
software and are the subjects named in certificates. These uses software and are the subjects named in certificates. These uses
include readers and writers of electronic mail, the clients for WWW include readers and writers of electronic mail, the clients for WWW
browsers, WWW servers, and the key manager for IPsec within a router. browsers, WWW servers, and the key manager for IPsec within a router.
This profile recognizes the limitations of the platforms these users This profile recognizes the limitations of the platforms these users
employ and the limitations in sophistication and attentiveness of the employ and the limitations in sophistication and attentiveness of the
users themselves. This manifests itself in minimal user configura- users themselves. This manifests itself in minimal user
tion responsibility (e.g., trusted CA keys, rules), explicit platform configuration responsibility (e.g., trusted CA keys, rules), explicit
usage constraints within the certificate, certification path con- platform usage constraints within the certificate, certification path
straints which shield the user from many malicious actions, and constraints which shield the user from many malicious actions, and
applications which sensibly automate validation functions. applications which sensibly automate validation functions.
2.4 Administrator Expectations 2.4 Administrator Expectations
As with user expectations, the Internet PKI profile is structured to As with user expectations, the Internet PKI profile is structured to
support the individuals who generally operate CAs. Providing support the individuals who generally operate CAs. Providing
administrators with unbounded choices increases the chances that a administrators with unbounded choices increases the chances that a
subtle CA administrator mistake will result in broad compromise. subtle CA administrator mistake will result in broad compromise.
Also, unbounded choices greatly complicate the software that shall Also, unbounded choices greatly complicate the software that shall
process and validate the certificates created by the CA. process and validate the certificates created by the CA.
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repository: a system or collection of distributed systems that repository: a system or collection of distributed systems that
store certificates and CRLs and serves as a means of store certificates and CRLs and serves as a means of
distributing these certificates and CRLs to end distributing these certificates and CRLs to end
entities. entities.
3.1 X.509 Version 3 Certificate 3.1 X.509 Version 3 Certificate
Users of a public key require confidence that the associated private Users of a public key require confidence that the associated private
key is owned by the correct remote subject (person or system) with key is owned by the correct remote subject (person or system) with
which an encryption or digital signature mechanism will be used. which an encryption or digital signature mechanism will be used.
This confidence is obtained through the use of public key certifi- This confidence is obtained through the use of public key
cates, which are data structures that bind public key values to sub- certificates, which are data structures that bind public key values
jects. The binding is asserted by having a trusted CA digitally sign to subjects. The binding is asserted by having a trusted CA
each certificate. The CA may base this assertion upon technical means digitally sign each certificate. The CA may base this assertion upon
(a.k.a., proof of posession through a challenge-response protocol), technical means (a.k.a., proof of posession through a challenge-
presentation of the private key, or on an assertion by the subject. response protocol), presentation of the private key, or on an
A certificate has a limited valid lifetime which is indicated in its assertion by the subject. A certificate has a limited valid lifetime
signed contents. Because a certificate's signature and timeliness which is indicated in its signed contents. Because a certificate's
can be independently checked by a certificate-using client, certifi- signature and timeliness can be independently checked by a
cates can be distributed via untrusted communications and server sys- certificate-using client, certificates can be distributed via
tems, and can be cached in unsecured storage in certificate-using untrusted communications and server systems, and can be cached in
systems. unsecured storage in certificate-using systems.
ITU-T X.509 (formerly CCITT X.509) or ISO/IEC/ITU 9594-8, which was ITU-T X.509 (formerly CCITT X.509) or ISO/IEC/ITU 9594-8, which was
first published in 1988 as part of the X.500 Directory recommenda- first published in 1988 as part of the X.500 Directory
tions, defines a standard certificate format [X.509]. The certificate recommendations, defines a standard certificate format [X.509]. The
format in the 1988 standard is called the version 1 (v1) format. certificate format in the 1988 standard is called the version 1 (v1)
When X.500 was revised in 1993, two more fields were added, resulting format. When X.500 was revised in 1993, two more fields were added,
in the version 2 (v2) format. resulting in the version 2 (v2) format.
The Internet Privacy Enhanced Mail (PEM) RFCs, published in 1993, The Internet Privacy Enhanced Mail (PEM) RFCs, published in 1993,
include specifications for a public key infrastructure based on X.509 include specifications for a public key infrastructure based on X.509
v1 certificates [RFC 1422]. The experience gained in attempts to v1 certificates [RFC 1422]. The experience gained in attempts to
deploy RFC 1422 made it clear that the v1 and v2 certificate formats deploy RFC 1422 made it clear that the v1 and v2 certificate formats
are deficient in several respects. Most importantly, more fields are deficient in several respects. Most importantly, more fields
were needed to carry information which PEM design and implementation were needed to carry information which PEM design and implementation
experience has proven necessary. In response to these new require- experience has proven necessary. In response to these new
ments, ISO/IEC/ITU and ANSI X9 developed the X.509 version 3 (v3) requirements, ISO/IEC/ITU and ANSI X9 developed the X.509 version 3
certificate format. The v3 format extends the v2 format by adding (v3) certificate format. The v3 format extends the v2 format by
provision for additional extension fields. Particular extension adding provision for additional extension fields. Particular
field types may be specified in standards or may be defined and extension field types may be specified in standards or may be defined
registered by any organization or community. In June 1996, standardi- and registered by any organization or community. In June 1996,
zation of the basic v3 format was completed [X.509]. standardization of the basic v3 format was completed [X.509].
ISO/IEC/ITU and ANSI X9 have also developed standard extensions for ISO/IEC/ITU and ANSI X9 have also developed standard extensions for
use in the v3 extensions field [X.509][X9.55]. These extensions can use in the v3 extensions field [X.509][X9.55]. These extensions can
convey such data as additional subject identification information, convey such data as additional subject identification information,
key attribute information, policy information, and certification path key attribute information, policy information, and certification path
constraints. constraints.
However, the ISO/IEC/ITU and ANSI X9 standard extensions are very However, the ISO/IEC/ITU and ANSI X9 standard extensions are very
broad in their applicability. In order to develop interoperable broad in their applicability. In order to develop interoperable
implementations of X.509 v3 systems for Internet use, it is necessary implementations of X.509 v3 systems for Internet use, it is necessary
to specify a profile for use of the X.509 v3 extensions tailored for to specify a profile for use of the X.509 v3 extensions tailored for
the Internet. It is one goal of this document to specify a profile the Internet. It is one goal of this document to specify a profile
for Internet WWW, electronic mail, and IPsec applications. Environ- for Internet WWW, electronic mail, and IPsec applications.
ments with additional requirements may build on this profile or may Environments with additional requirements may build on this profile
replace it. or may replace it.
3.2 Certification Paths and Trust 3.2 Certification Paths and Trust
A user of a security service requiring knowledge of a public key gen- A user of a security service requiring knowledge of a public key
erally needs to obtain and validate a certificate containing the generally needs to obtain and validate a certificate containing the
required public key. If the public-key user does not already hold an required public key. If the public-key user does not already hold an
assured copy of the public key of the CA that signed the certificate, assured copy of the public key of the CA that signed the certificate,
the CA's name, and related information (such as the validity period the CA's name, and related information (such as the validity period
or name constraints), then it might need an additional certificate to or name constraints), then it might need an additional certificate to
obtain that public key. In general, a chain of multiple certificates obtain that public key. In general, a chain of multiple certificates
may be needed, comprising a certificate of the public key owner (the may be needed, comprising a certificate of the public key owner (the
end entity) signed by one CA, and zero or more additional certifi- end entity) signed by one CA, and zero or more additional
cates of CAs signed by other CAs. Such chains, called certification certificates of CAs signed by other CAs. Such chains, called
paths, are required because a public key user is only initialized certification paths, are required because a public key user is only
with a limited number of assured CA public keys. initialized with a limited number of assured CA public keys.
There are different ways in which CAs might be configured in order There are different ways in which CAs might be configured in order
for public key users to be able to find certification paths. For for public key users to be able to find certification paths. For
PEM, RFC 1422 defined a rigid hierarchical structure of CAs. There PEM, RFC 1422 defined a rigid hierarchical structure of CAs. There
are three types of PEM certification authority: are three types of PEM certification authority:
(a) Internet Policy Registration Authority (IPRA): This author- (a) Internet Policy Registration Authority (IPRA): This
ity, operated under the auspices of the Internet Society, acts as authority, operated under the auspices of the Internet Society,
the root of the PEM certification hierarchy at level 1. It issues acts as the root of the PEM certification hierarchy at level 1.
certificates only for the next level of authorities, PCAs. All It issues certificates only for the next level of authorities,
certification paths start with the IPRA. PCAs. All certification paths start with the IPRA.
(b) Policy Certification Authorities (PCAs): PCAs are at level 2 (b) Policy Certification Authorities (PCAs): PCAs are at level 2
of the hierarchy, each PCA being certified by the IPRA. A PCA of the hierarchy, each PCA being certified by the IPRA. A PCA
shall establish and publish a statement of its policy with respect shall establish and publish a statement of its policy with respect
to certifying users or subordinate certification authorities. to certifying users or subordinate certification authorities.
Distinct PCAs aim to satisfy different user needs. For example, Distinct PCAs aim to satisfy different user needs. For example,
one PCA (an organizational PCA) might support the general elec- one PCA (an organizational PCA) might support the general
tronic mail needs of commercial organizations, and another PCA (a electronic mail needs of commercial organizations, and another PCA
high-assurance PCA) might have a more stringent policy designed (a high-assurance PCA) might have a more stringent policy designed
for satisfying legally binding digital signature requirements. for satisfying legally binding digital signature requirements.
(c) Certification Authorities (CAs): CAs are at level 3 of the (c) Certification Authorities (CAs): CAs are at level 3 of the
hierarchy and can also be at lower levels. Those at level 3 are hierarchy and can also be at lower levels. Those at level 3 are
certified by PCAs. CAs represent, for example, particular organi- certified by PCAs. CAs represent, for example, particular
zations, particular organizational units (e.g., departments, organizations, particular organizational units (e.g., departments,
groups, sections), or particular geographical areas. groups, sections), or particular geographical areas.
RFC 1422 furthermore has a name subordination rule which requires RFC 1422 furthermore has a name subordination rule which requires
that a CA can only issue certificates for entities whose names are that a CA can only issue certificates for entities whose names are
subordinate (in the X.500 naming tree) to the name of the CA itself. subordinate (in the X.500 naming tree) to the name of the CA itself.
The trust associated with a PEM certification path is implied by the The trust associated with a PEM certification path is implied by the
PCA name. The name subordination rule ensures that CAs below the PCA PCA name. The name subordination rule ensures that CAs below the PCA
are sensibly constrained as to the set of subordinate entities they are sensibly constrained as to the set of subordinate entities they
can certify (e.g., a CA for an organization can only certify entities can certify (e.g., a CA for an organization can only certify entities
in that organization's name tree). Certificate user systems are able in that organization's name tree). Certificate user systems are able
to mechanically check that the name subordination rule has been fol- to mechanically check that the name subordination rule has been
lowed. followed.
The RFC 1422 uses the X.509 v1 certificate formats. The limitations The RFC 1422 uses the X.509 v1 certificate formats. The limitations
of X.509 v1 required imposition of several structural restrictions to of X.509 v1 required imposition of several structural restrictions to
clearly associate policy information or restrict the utility of cer- clearly associate policy information or restrict the utility of
tificates. These restrictions included: certificates. These restrictions included:
(a) a pure top-down hierarchy, with all certification paths start- (a) a pure top-down hierarchy, with all certification paths
ing from IPRA; starting from IPRA;
(b) a naming subordination rule restricting the names of a CA's (b) a naming subordination rule restricting the names of a CA's
subjects; and subjects; and
(c) use of the PCA concept, which requires knowledge of individual (c) use of the PCA concept, which requires knowledge of individual
PCAs to be built into certificate chain verification logic. PCAs to be built into certificate chain verification logic.
Knowledge of individual PCAs was required to determine if a chain Knowledge of individual PCAs was required to determine if a chain
could be accepted. could be accepted.
With X.509 v3, most of the requirements addressed by RFC 1422 can be With X.509 v3, most of the requirements addressed by RFC 1422 can be
addressed using certificate extensions, without a need to restrict addressed using certificate extensions, without a need to restrict
the CA structures used. In particular, the certificate extensions the CA structures used. In particular, the certificate extensions
relating to certificate policies obviate the need for PCAs and the relating to certificate policies obviate the need for PCAs and the
constraint extensions obviate the need for the name subordination constraint extensions obviate the need for the name subordination
rule. As a result, this document supports a more flexible architec- rule. As a result, this document supports a more flexible
ture, including: architecture, including:
(a) Certification paths may start with a public key of a CA in a (a) Certification paths may start with a public key of a CA in a
user's own domain, or with the public key of the top of a hierar- user's own domain, or with the public key of the top of a
chy. Starting with the public key of a CA in a user's own domain hierarchy. Starting with the public key of a CA in a user's own
has certain advantages. In some environments, the local domain is domain has certain advantages. In some environments, the local
the most trusted. domain is the most trusted.
(b) Name constraints may be imposed through explicit inclusion of (b) Name constraints may be imposed through explicit inclusion of
a name constraints extension in a certificate, but are not a name constraints extension in a certificate, but are not
required. required.
(c) Policy extensions and policy mappings replace the PCA con- (c) Policy extensions and policy mappings replace the PCA
cept, which permits a greater degree of automation. The applica- concept, which permits a greater degree of automation. The
tion can determine if the certification path is acceptable based application can determine if the certification path is acceptable
on the contents of the certificates instead of a priori knowledge based on the contents of the certificates instead of a priori
of PCAs. This permits automation of certificate chain processing. knowledge of PCAs. This permits automation of certificate chain
processing.
3.3 Revocation 3.3 Revocation
When a certificate is issued, it is expected to be in use for its When a certificate is issued, it is expected to be in use for its
entire validity period. However, various circumstances may cause a entire validity period. However, various circumstances may cause a
certificate to become invalid prior to the expiration of the validity certificate to become invalid prior to the expiration of the validity
period. Such circumstances include change of name, change of associa- period. Such circumstances include change of name, change of
tion between subject and CA (e.g., an employee terminates employment association between subject and CA (e.g., an employee terminates
with an organization), and compromise or suspected compromise of the employment with an organization), and compromise or suspected
corresponding private key. Under such circumstances, the CA needs to compromise of the corresponding private key. Under such
revoke the certificate. circumstances, the CA needs to revoke the certificate.
X.509 defines one method of certificate revocation. This method X.509 defines one method of certificate revocation. This method
involves each CA periodically issuing a signed data structure called involves each CA periodically issuing a signed data structure called
a certificate revocation list (CRL). A CRL is a time stamped list a certificate revocation list (CRL). A CRL is a time stamped list
identifying revoked certificates which is signed by a CA and made identifying revoked certificates which is signed by a CA and made
freely available in a public repository. Each revoked certificate is freely available in a public repository. Each revoked certificate is
identified in a CRL by its certificate serial number. When a identified in a CRL by its certificate serial number. When a
certificate-using system uses a certificate (e.g., for verifying a certificate-using system uses a certificate (e.g., for verifying a
remote user's digital signature), that system not only checks the remote user's digital signature), that system not only checks the
certificate signature and validity but also acquires a suitably- certificate signature and validity but also acquires a suitably-
recent CRL and checks that the certificate serial number is not on recent CRL and checks that the certificate serial number is not on
that CRL. The meaning of "suitably-recent" may vary with local pol- that CRL. The meaning of "suitably-recent" may vary with local
icy, but it usually means the most recently-issued CRL. A CA issues policy, but it usually means the most recently-issued CRL. A CA
a new CRL on a regular periodic basis (e.g., hourly, daily, or issues a new CRL on a regular periodic basis (e.g., hourly, daily, or
weekly). An entry is added to the CRL as part of the next update weekly). An entry is added to the CRL as part of the next update
following notification of revocation. An entry may be removed from following notification of revocation. An entry may be removed from
the CRL after appearing on one regularly scheduled CRL issued beyond the CRL after appearing on one regularly scheduled CRL issued beyond
the revoked certificate's validity period. the revoked certificate's validity period.
An advantage of this revocation method is that CRLs may be distri- An advantage of this revocation method is that CRLs may be
buted by exactly the same means as certificates themselves, namely, distributed by exactly the same means as certificates themselves,
via untrusted communications and server systems. namely, via untrusted communications and server systems.
One limitation of the CRL revocation method, using untrusted communi- One limitation of the CRL revocation method, using untrusted
cations and servers, is that the time granularity of revocation is communications and servers, is that the time granularity of
limited to the CRL issue period. For example, if a revocation is revocation is limited to the CRL issue period. For example, if a
reported now, that revocation will not be reliably notified to revocation is reported now, that revocation will not be reliably
certificate-using systems until the next periodic CRL is issued -- notified to certificate-using systems until the next periodic CRL is
this may be up to one hour, one day, or one week depending on the issued -- this may be up to one hour, one day, or one week depending
frequency that the CA issues CRLs. on the frequency that the CA issues CRLs.
As with the X.509 v3 certificate format, in order to facilitate As with the X.509 v3 certificate format, in order to facilitate
interoperable implementations from multiple vendors, the X.509 v2 CRL interoperable implementations from multiple vendors, the X.509 v2 CRL
format needs to be profiled for Internet use. It is one goal of this format needs to be profiled for Internet use. It is one goal of this
document to specify that profile. However, this profile does not document to specify that profile. However, this profile does not
require CAs to issue CRLs. Message formats and protocols supporting require CAs to issue CRLs. Message formats and protocols supporting
on-line revocation notification may be defined in other PKIX specifi- on-line revocation notification may be defined in other PKIX
cations. On-line methods of revocation notification may be applica- specifications. On-line methods of revocation notification may be
ble in some environments as an alternative to the X.509 CRL. On-line applicable in some environments as an alternative to the X.509 CRL.
revocation checking may significantly reduce the latency between a On-line revocation checking may significantly reduce the latency
revocation report and the distribution of the information to relying between a revocation report and the distribution of the information
parties. Once the CA accepts the report as authentic and valid, any to relying parties. Once the CA accepts the report as authentic and
query to the on-line service will correctly reflect the certificate valid, any query to the on-line service will correctly reflect the
validation impacts of the revocation. However, these methods impose certificate validation impacts of the revocation. However, these
new security requirements: the certificate validator needs to trust methods impose new security requirements: the certificate validator
the on-line validation service while the repository does not need to needs to trust the on-line validation service while the repository
be trusted. does not need to be trusted.
3.4 Operational Protocols 3.4 Operational Protocols
Operational protocols are required to deliver certificates and CRLs Operational protocols are required to deliver certificates and CRLs
(or status information) to certificate using client systems. Provi- (or status information) to certificate using client systems.
sion is needed for a variety of different means of certificate and Provision is needed for a variety of different means of certificate
CRL delivery, including distribution procedures based on LDAP, HTTP, and CRL delivery, including distribution procedures based on LDAP,
FTP, and X.500. Operational protocols supporting these functions are HTTP, FTP, and X.500. Operational protocols supporting these
defined in other PKIX specifications. These specifications may functions are defined in other PKIX specifications. These
include definitions of message formats and procedures for supporting specifications may include definitions of message formats and
all of the above operational environments, including definitions of procedures for supporting all of the above operational environments,
or references to appropriate MIME content types. including definitions of or references to appropriate MIME content
types.
3.5 Management Protocols 3.5 Management Protocols
Management protocols are required to support on-line interactions Management protocols are required to support on-line interactions
between PKI user and management entities. For example, a management between PKI user and management entities. For example, a management
protocol might be used between a CA and a client system with which a protocol might be used between a CA and a client system with which a
key pair is associated, or between two CAs which cross-certify each key pair is associated, or between two CAs which cross-certify each
other. The set of functions which potentially need to be supported other. The set of functions which potentially need to be supported
by management protocols include: by management protocols include:
(a) registration: This is the process whereby a user first makes (a) registration: This is the process whereby a user first makes
itself known to a CA (directly, or through an RA), prior to that itself known to a CA (directly, or through an RA), prior to that
CA issuing a certificate or certificates for that user. CA issuing a certificate or certificates for that user.
(b) initialization: Before a client system can operate securely (b) initialization: Before a client system can operate securely
it is necessary to install key materials which have the appropri- it is necessary to install key materials which have the
ate relationship with keys stored elsewhere in the infrastructure. appropriate relationship with keys stored elsewhere in the
For example, the client needs to be securely initialized with the infrastructure. For example, the client needs to be securely
public key and other assured information of the trusted CA(s), to initialized with the public key and other assured information of
be used in validating certificate paths. Furthermore, a client the trusted CA(s), to be used in validating certificate paths.
typically needs to be initialized with its own key pair(s). Furthermore, a client typically needs to be initialized with its
own key pair(s).
(c) certification: This is the process in which a CA issues a (c) certification: This is the process in which a CA issues a
certificate for a user's public key, and returns that certificate certificate for a user's public key, and returns that certificate
to the user's client system and/or posts that certificate in a to the user's client system and/or posts that certificate in a
repository. repository.
(d) key pair recovery: As an option, user client key materials (d) key pair recovery: As an option, user client key materials
(e.g., a user's private key used for encryption purposes) may be (e.g., a user's private key used for encryption purposes) may be
backed up by a CA or a key backup system. If a user needs to backed up by a CA or a key backup system. If a user needs to
recover these backed up key materials (e.g., as a result of a for- recover these backed up key materials (e.g., as a result of a
gotten password or a lost key chain file), an on-line protocol forgotten password or a lost key chain file), an on-line protocol
exchange may be needed to support such recovery. exchange may be needed to support such recovery.
(e) key pair update: All key pairs need to be updated regularly, (e) key pair update: All key pairs need to be updated regularly,
i.e., replaced with a new key pair, and new certificates issued. i.e., replaced with a new key pair, and new certificates issued.
(f) revocation request: An authorized person advises a CA of an (f) revocation request: An authorized person advises a CA of an
abnormal situation requiring certificate revocation. abnormal situation requiring certificate revocation.
(g) cross-certification: Two CAs exchange information used in (g) cross-certification: Two CAs exchange information used in
establishing a cross-certificate. A cross-certificate is a certi- establishing a cross-certificate. A cross-certificate is a
ficate issued by one CA to another CA which contains a CA signa- certificate issued by one CA to another CA which contains a CA
ture key used for issuing certificates. signature key used for issuing certificates.
Note that on-line protocols are not the only way of implementing the Note that on-line protocols are not the only way of implementing the
above functions. For all functions there are off-line methods of above functions. For all functions there are off-line methods of
achieving the same result, and this specification does not mandate achieving the same result, and this specification does not mandate
use of on-line protocols. For example, when hardware tokens are use of on-line protocols. For example, when hardware tokens are
used, many of the functions may be achieved as part of the physical used, many of the functions may be achieved as part of the physical
token delivery. Furthermore, some of the above functions may be com- token delivery. Furthermore, some of the above functions may be
bined into one protocol exchange. In particular, two or more of the combined into one protocol exchange. In particular, two or more of
registration, initialization, and certification functions can be com- the registration, initialization, and certification functions can be
bined into one protocol exchange. combined into one protocol exchange.
The PKIX series of specifications may define a set of standard mes- The PKIX series of specifications may define a set of standard
sage formats supporting the above functions in future specifications. message formats supporting the above functions in future
In that case, the protocols for conveying these messages in different specifications. In that case, the protocols for conveying these
environments (e.g., on-line, file transfer, e-mail, and WWW) will messages in different environments (e.g., on-line, file transfer, e-
also be described in those specifications. mail, and WWW) will also be described in those specifications.
4 Certificate and Certificate Extensions Profile 4 Certificate and Certificate Extensions Profile
This section presents a profile for public key certificates that will This section presents a profile for public key certificates that will
foster interoperability and a reusable PKI. This section is based foster interoperability and a reusable PKI. This section is based
upon the X.509 v3 certificate format and the standard certificate upon the X.509 v3 certificate format and the standard certificate
extensions defined in [X.509]. The ISO/IEC/ITU documents use the extensions defined in [X.509]. The ISO/IEC/ITU documents use the
1993 version of ASN.1; while this document uses the 1988 ASN.1 syn- 1993 version of ASN.1; while this document uses the 1988 ASN.1
tax, the encoded certificate and standard extensions are equivalent. syntax, the encoded certificate and standard extensions are
This section also defines private extensions required to support a equivalent. This section also defines private extensions required to
PKI for the Internet community. support a PKI for the Internet community.
Certificates may be used in a wide range of applications and environ- Certificates may be used in a wide range of applications and
ments covering a broad spectrum of interoperability goals and a environments covering a broad spectrum of interoperability goals and
broader spectrum of operational and assurance requirements. The goal a broader spectrum of operational and assurance requirements. The
of this document is to establish a common baseline for generic appli- goal of this document is to establish a common baseline for generic
cations requiring broad interoperability and limited special purpose applications requiring broad interoperability and limited special
requirements. In particular, the emphasis will be on supporting the purpose requirements. In particular, the emphasis will be on
use of X.509 v3 certificates for informal Internet electronic mail, supporting the use of X.509 v3 certificates for informal Internet
IPsec, and WWW applications. electronic mail, IPsec, and WWW applications.
4.1 Basic Certificate Fields 4.1 Basic Certificate Fields
The X.509 v3 certificate basic syntax is as follows. For signature The X.509 v3 certificate basic syntax is as follows. For signature
calculation, the certificate is encoded using the ASN.1 distinguished calculation, the certificate is encoded using the ASN.1 distinguished
encoding rules (DER) [X.208]. ASN.1 DER encoding is a tag, length, encoding rules (DER) [X.208]. ASN.1 DER encoding is a tag, length,
value encoding system for each element. value encoding system for each element.
Certificate ::= SEQUENCE { Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate, tbsCertificate TBSCertificate,
skipping to change at page 17, line 36 skipping to change at page 17, line 38
4.1.1.1 tbsCertificate 4.1.1.1 tbsCertificate
The field contains the names of the subject and issuer, a public key The field contains the names of the subject and issuer, a public key
associated with the subject, a validity period, and other associated associated with the subject, a validity period, and other associated
information. The fields are described in detail in section 4.1.2; information. The fields are described in detail in section 4.1.2;
the tbscertificate may also include extensions which are described in the tbscertificate may also include extensions which are described in
section 4.2. section 4.2.
4.1.1.2 signatureAlgorithm 4.1.1.2 signatureAlgorithm
The signatureAlgorithm field contains the identifier for the crypto- The signatureAlgorithm field contains the identifier for the
graphic algorithm used by the CA to sign this certificate. [PKIX cryptographic algorithm used by the CA to sign this certificate.
ALGS] lists the supported signature algorithms. [PKIX ALGS] lists the supported signature algorithms.
An algorithm identifier is defined by the following ASN.1 structure: An algorithm identifier is defined by the following ASN.1 structure:
AlgorithmIdentifier ::= SEQUENCE { AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER, algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL } parameters ANY DEFINED BY algorithm OPTIONAL }
The algorithm identifier is used to identify a cryptographic algo- The algorithm identifier is used to identify a cryptographic
rithm. The OBJECT IDENTIFIER component identifies the algorithm algorithm. The OBJECT IDENTIFIER component identifies the algorithm
(such as DSA with SHA-1). The contents of the optional parameters (such as DSA with SHA-1). The contents of the optional parameters
field will vary according to the algorithm identified. [PKIX ALGS] field will vary according to the algorithm identified. [PKIX ALGS]
lists the supported algorithms for this specification. lists the supported algorithms for this specification.
This field MUST contain the same algorithm identifier as the This field MUST contain the same algorithm identifier as the
signature field in the sequence tbsCertificate (see sec. 4.1.2.3). signature field in the sequence tbsCertificate (see sec. 4.1.2.3).
4.1.1.3 signatureValue 4.1.1.3 signatureValue
The signatureValue field contains a digital signature computed upon The signatureValue field contains a digital signature computed upon
the ASN.1 DER encoded tbsCertificate. The ASN.1 DER encoded tbsCer- the ASN.1 DER encoded tbsCertificate. The ASN.1 DER encoded
tificate is used as the input to the signature function. This signa- tbsCertificate is used as the input to the signature function. This
ture value is then ASN.1 encoded as a BIT STRING and included in the signature value is then ASN.1 encoded as a BIT STRING and included in
Certificate's signature field. The details of this process are speci- the Certificate's signature field. The details of this process are
fied for each of the supported algorithms in [PKIX ALGS]. specified for each of the supported algorithms in [PKIX ALGS].
By generating this signature, a CA certifies the validity of the By generating this signature, a CA certifies the validity of the
information in the tbsCertificate field. In particular, the CA cer- information in the tbsCertificate field. In particular, the CA
tifies the binding between the public key material and the subject of certifies the binding between the public key material and the subject
the certificate. of the certificate.
4.1.2 TBSCertificate 4.1.2 TBSCertificate
The sequence TBSCertificate contains information associated with the The sequence TBSCertificate contains information associated with the
subject of the certificate and the CA who issued it. Every TBSCerti- subject of the certificate and the CA who issued it. Every
ficate contains the names of the subject and issuer, a public key TBSCertificate contains the names of the subject and issuer, a public
associated with the subject, a validity period, a version number, and key associated with the subject, a validity period, a version number,
a serial number; some may contain optional unique identifier fields. and a serial number; some may contain optional unique identifier
The remainder of this section describes the syntax and semantics of fields. The remainder of this section describes the syntax and
these fields. A TBSCertificate may also include extensions. Exten- semantics of these fields. A TBSCertificate may also include
sions for the Internet PKI are described in Section 4.2. extensions. Extensions for the Internet PKI are described in Section
4.2.
4.1.2.1 Version 4.1.2.1 Version
This field describes the version of the encoded certificate. When This field describes the version of the encoded certificate. When
extensions are used, as expected in this profile, use X.509 version 3 extensions are used, as expected in this profile, use X.509 version 3
(value is 2). If no extensions are present, but a UniqueIdentifier (value is 2). If no extensions are present, but a UniqueIdentifier
is present, use version 2 (value is 1). If only basic fields are is present, use version 2 (value is 1). If only basic fields are
present, use version 1 (the value is omitted from the certificate as present, use version 1 (the value is omitted from the certificate as
the default value). the default value).
Implementations SHOULD be prepared to accept any version certificate. Implementations SHOULD be prepared to accept any version certificate.
At a minimum, conforming implementations MUST recognize version 3 At a minimum, conforming implementations MUST recognize version 3
certificates. certificates.
Generation of version 2 certificates is not expected by implementa- Generation of version 2 certificates is not expected by
tions based on this profile. implementations based on this profile.
4.1.2.2 Serial number 4.1.2.2 Serial number
The serial number is a positive integer assigned by the CA to each The serial number is a positive integer assigned by the CA to each
certificate. It MUST be unique for each certificate issued by a certificate. It MUST be unique for each certificate issued by a
given CA (i.e., the issuer name and serial number identify a unique given CA (i.e., the issuer name and serial number identify a unique
certificate). certificate). CAs MUST force the serialNumber to be a non-negative
integer.
Given the uniqueness requirements above serial numbers can be
expected to contain long integers. Certificate users MUST be able to
handle serialNumber values up to 20 octets. Conformant CAs MUST NOT
use serialNumber values longer than 20 octets.
Note: Non-conforming CAs may issue certificates with serial numbers
that are negative, or zero. Certificate users SHOULD be prepared to
handle such certificates.
4.1.2.3 Signature 4.1.2.3 Signature
This field contains the algorithm identifier for the algorithm used This field contains the algorithm identifier for the algorithm used
by the CA to sign the certificate. by the CA to sign the certificate.
This field MUST contain the same algorithm identifier as the signa- This field MUST contain the same algorithm identifier as the
tureAlgorithm field in the sequence Certificate (see sec. 4.1.1.2). signatureAlgorithm field in the sequence Certificate (see sec.
The contents of the optional parameters field will vary according to 4.1.1.2). The contents of the optional parameters field will vary
the algorithm identified. [PKIX ALGS] lists the supported signature according to the algorithm identified. [PKIX ALGS] lists the
algorithms. supported signature algorithms.
4.1.2.4 Issuer 4.1.2.4 Issuer
The issuer field identifies the entity who has signed and issued the The issuer field identifies the entity who has signed and issued the
certificate. The issuer field MUST contain a non-empty distinguished certificate. The issuer field MUST contain a non-empty distinguished
name (DN). The issuer field is defined as the X.501 type Name. name (DN). The issuer field is defined as the X.501 type Name.
[X.501] Name is defined by the following ASN.1 structures: [X.501] Name is defined by the following ASN.1 structures:
Name ::= CHOICE { Name ::= CHOICE {
RDNSequence } RDNSequence }
skipping to change at page 19, line 37 skipping to change at page 20, line 4
RDNSequence ::= SEQUENCE OF RelativeDistinguishedName RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
RelativeDistinguishedName ::= RelativeDistinguishedName ::=
SET OF AttributeTypeAndValue SET OF AttributeTypeAndValue
AttributeTypeAndValue ::= SEQUENCE { AttributeTypeAndValue ::= SEQUENCE {
type AttributeType, type AttributeType,
value AttributeValue } value AttributeValue }
AttributeType ::= OBJECT IDENTIFIER AttributeType ::= OBJECT IDENTIFIER
AttributeValue ::= ANY DEFINED BY AttributeType AttributeValue ::= ANY DEFINED BY AttributeType
DirectoryString ::= CHOICE { DirectoryString ::= CHOICE {
teletexString TeletexString (SIZE (1..MAX)), teletexString TeletexString (SIZE (1..MAX)),
printableString PrintableString (SIZE (1..MAX)), printableString PrintableString (SIZE (1..MAX)),
universalString UniversalString (SIZE (1..MAX)), universalString UniversalString (SIZE (1..MAX)),
utf8String UTF8String (SIZE (1.. MAX)), utf8String UTF8String (SIZE (1.. MAX)),
bmpString BMPString (SIZE (1..MAX)) } bmpString BMPString (SIZE (1..MAX)) }
The Name describes a hierarchical name composed of attributes, such The Name describes a hierarchical name composed of attributes, such
as country name, and corresponding values, such as US. The type of as country name, and corresponding values, such as US. The type of
the component AttributeValue is determined by the AttributeType; in the component AttributeValue is determined by the AttributeType; in
general it will be a DirectoryString. general it will be a DirectoryString.
The DirectoryString type is defined as a choice of PrintableString, The DirectoryString type is defined as a choice of PrintableString,
TeletexString, BMPString, UTF8String, and UniversalString. The TeletexString, BMPString, UTF8String, and UniversalString. The
UTF8String encoding is the preferred encoding, and all certificates UTF8String encoding is the preferred encoding, and all certificates
issued after December 31, 2003 MUST use the UTF8String encoding of issued after December 31, 2003 MUST use the UTF8String encoding of
DirectoryString (except as noted below). Until that date, conforming DirectoryString (except as noted below). Until that date, conforming
CAs MUST choose from the following options when creating a dis- CAs MUST choose from the following options when creating a
tinguished name, including their own: distinguished name, including their own:
(a) if the character set is sufficient, the string MAY be (a) if the character set is sufficient, the string MAY be
represented as a PrintableString; represented as a PrintableString;
(b) failing (a), if the BMPString character set is sufficient the (b) failing (a), if the BMPString character set is sufficient the
string MAY be represented as a BMPString; and string MAY be represented as a BMPString; and
(c) failing (a) and (b), the string MUST be represented as a (c) failing (a) and (b), the string MUST be represented as a
UTF8String. If (a) or (b) is satisfied, the CA MAY still choose UTF8String. If (a) or (b) is satisfied, the CA MAY still choose
to represent the string as a UTF8String. to represent the string as a UTF8String.
Exceptions to the December 31, 2003 UTF8 encoding requirements are as Exceptions to the December 31, 2003 UTF8 encoding requirements are as
follows: follows:
(a) CAs MAY issue "name rollover" certificates to support an ord- (a) CAs MAY issue "name rollover" certificates to support an
erly migration to UTF8String encoding. Such certificates would orderly migration to UTF8String encoding. Such certificates would
include the CA's UTF8String encoded name as issuer and and the old include the CA's UTF8String encoded name as issuer and and the old
name encoding as subject, or vice-versa. name encoding as subject, or vice-versa.
(b) As stated in section 4.1.2.6, the subject field MUST be popu- (b) As stated in section 4.1.2.6, the subject field MUST be
lated with a non-empty distinguished name matching the contents of populated with a non-empty distinguished name matching the
the issuer field in all certificates issued by the subject CA contents of the issuer field in all certificates issued by the
regardless of encoding. subject CA regardless of encoding.
The TeletexString and UniversalString are included for backward com- The TeletexString and UniversalString are included for backward
patibility, and should not be used for certificates for new subjects. compatibility, and should not be used for certificates for new
However, these types may be used in certificates where the name was subjects. However, these types may be used in certificates where the
previously established. Certificate users SHOULD be prepared to name was previously established. Certificate users SHOULD be
receive certificates with these types. prepared to receive certificates with these types.
In addition, many legacy implementations support names encoded in the In addition, many legacy implementations support names encoded in the
ISO 8859-1 character set (Latin1String) but tag them as Teletex- ISO 8859-1 character set (Latin1String) but tag them as
String. The Latin1String includes characters used in Western Euro- TeletexString. The Latin1String includes characters used in Western
pean countries which are not part of the TeletexString charcter set. European countries which are not part of the TeletexString charcter
Implementations that process TeletexString SHOULD be prepared to han- set. Implementations that process TeletexString SHOULD be prepared
dle the entire ISO 8859-1 character set.[ISO 8859-1] to handle the entire ISO 8859-1 character set.[ISO 8859-1]
As noted above, distinguished names are composed of attributes. This As noted above, distinguished names are composed of attributes. This
specification does not restrict the set of attribute types that may specification does not restrict the set of attribute types that may
appear in names. However, conforming implementations MUST be appear in names. However, conforming implementations MUST be
prepared to receive certificates with issuer names containing the set prepared to receive certificates with issuer names containing the set
of attribute types defined below. This specification also recommends of attribute types defined below. This specification also recommends
support for additional attribute types. support for additional attribute types.
Standard sets of attributes have been defined in the X.500 series of Standard sets of attributes have been defined in the X.500 series of
specifications.[X.520] Implementations of this specification MUST be specifications.[X.520] Implementations of this specification MUST be
skipping to change at page 21, line 21 skipping to change at page 21, line 36
* country, * country,
* organization, * organization,
* organizational-unit, * organizational-unit,
* distinguished name qualifier, * distinguished name qualifier,
* state or province name, * state or province name,
* common name (e.g., "Susan Housley"), and * common name (e.g., "Susan Housley"), and
* serial number. * serial number.
In addition, implementations of this specification SHOULD be prepared In addition, implementations of this specification SHOULD be prepared
to receive the following standard attribute types in issuer and sub- to receive the following standard attribute types in issuer and
ject names: subject names:
* locality, * locality,
* title, * title,
* surname, * surname,
* given name, * given name,
* initials, and * initials,
* pseudonym, and
* generation qualifier (e.g., "Jr.", "3rd", or "IV"). * generation qualifier (e.g., "Jr.", "3rd", or "IV").
The syntax and associated object identifiers (OIDs) for these attri- The syntax and associated object identifiers (OIDs) for these
bute types are provided in the ASN.1 modules in Appendices A and B. attribute types are provided in the ASN.1 modules in Appendices A and
B.
In addition, implementations of this specification MUST be prepared In addition, implementations of this specification MUST be prepared
to receive the domainComponent attribute, as defined in [RFC 2247]. to receive the domainComponent attribute, as defined in [RFC 2247].
The Domain (Nameserver) System (DNS) provides a hierarchical resource The Domain (Nameserver) System (DNS) provides a hierarchical resource
labeling system. This attribute provides is a convenient mechanism labeling system. This attribute provides is a convenient mechanism
for organizations that wish to use DNs that parallel their DNS names. for organizations that wish to use DNs that parallel their DNS names.
This is not a replacement for the dNSName component of the alterna- This is not a replacement for the dNSName component of the
tive name field. Implementations are not required to convert such alternative name field. Implementations are not required to convert
names into DNS names. The syntax and associated OID for this attri- such names into DNS names. The syntax and associated OID for this
bute type is provided in the ASN.1 modules in Appendices A and B. attribute type is provided in the ASN.1 modules in Appendices A and
B.
Certificate users MUST be prepared to process the issuer dis- Certificate users MUST be prepared to process the issuer
tinguished name and subject distinguished name (see sec. 4.1.2.6) distinguished name and subject distinguished name (see sec. 4.1.2.6)
fields to perform name chaining for certification path validation fields to perform name chaining for certification path validation
(see section 6). Name chaining is performed by matching the issuer (see section 6). Name chaining is performed by matching the issuer
distinguished name in one certificate with the subject name in a CA distinguished name in one certificate with the subject name in a CA
certificate. certificate.
This specification requires only a subset of the name comparison This specification requires only a subset of the name comparison
functionality specified in the X.500 series of specifications. The functionality specified in the X.500 series of specifications. The
requirements for conforming implementations are as follows: requirements for conforming implementations are as follows:
(a) attribute values encoded in different types (e.g., Printable- (a) attribute values encoded in different types (e.g.,
String and BMPString) may be assumed to represent different PrintableString and BMPString) may be assumed to represent
strings; different strings;
(b) attribute values in types other than PrintableString are case (b) attribute values in types other than PrintableString are case
sensitive (this permits matching of attribute values as binary sensitive (this permits matching of attribute values as binary
objects); objects);
(c) attribute values in PrintableString are not case sensitive (c) attribute values in PrintableString are not case sensitive
(e.g., "Marianne Swanson" is the same as "MARIANNE SWANSON"); and (e.g., "Marianne Swanson" is the same as "MARIANNE SWANSON"); and
(d) attribute values in PrintableString are compared after remov- (d) attribute values in PrintableString are compared after
ing leading and trailing white space and converting internal sub- removing leading and trailing white space and converting internal
strings of one or more consecutive white space characters to a substrings of one or more consecutive white space characters to a
single space. single space.
These name comparison rules permit a certificate user to validate These name comparison rules permit a certificate user to validate
certificates issued using languages or encodings unfamiliar to the certificates issued using languages or encodings unfamiliar to the
certificate user. certificate user.
In addition, implementations of this specification MAY use these com- In addition, implementations of this specification MAY use these
parison rules to process unfamiliar attribute types for name chain- comparison rules to process unfamiliar attribute types for name
ing. This allows implementations to process certificates with unfami- chaining. This allows implementations to process certificates with
liar attributes in the issuer name. unfamiliar attributes in the issuer name.
Note that the comparison rules defined in the X.500 series of specif- Note that the comparison rules defined in the X.500 series of
ications indicate that the character sets used to encode data in dis- specifications indicate that the character sets used to encode data
tinguished names are irrelevant. The characters themselves are com- in distinguished names are irrelevant. The characters themselves are
pared without regard to encoding. Implementations of the profile are compared without regard to encoding. Implementations of the profile
permitted to use the comparison algorithm defined in the X.500 are permitted to use the comparison algorithm defined in the X.500
series. Such an implementation will recognize a superset of name series. Such an implementation will recognize a superset of name
matches recognized by the algorithm specified above. matches recognized by the algorithm specified above.
4.1.2.5 Validity 4.1.2.5 Validity
The certificate validity period is the time interval during which the The certificate validity period is the time interval during which the
CA warrants that it will maintain information about the status of the CA warrants that it will maintain information about the status of the
certificate. The field is represented as a SEQUENCE of two dates: certificate. The field is represented as a SEQUENCE of two dates:
the date on which the certificate validity period begins (notBefore) the date on which the certificate validity period begins (notBefore)
and the date on which the certificate validity period ends and the date on which the certificate validity period ends
(notAfter). Both notBefore and notAfter may be encoded as UTCTime or (notAfter). Both notBefore and notAfter may be encoded as UTCTime or
GeneralizedTime. GeneralizedTime.
CAs conforming to this profile MUST always encode certificate vali- CAs conforming to this profile MUST always encode certificate
dity dates through the year 2049 as UTCTime; certificate validity validity dates through the year 2049 as UTCTime; certificate validity
dates in 2050 or later MUST be encoded as GeneralizedTime. dates in 2050 or later MUST be encoded as GeneralizedTime.
The validity period for a certificate is the period of time from The validity period for a certificate is the period of time from
notBefore through notAfter, inclusive. notBefore through notAfter, inclusive.
4.1.2.5.1 UTCTime 4.1.2.5.1 UTCTime
The universal time type, UTCTime, is a standard ASN.1 type intended The universal time type, UTCTime, is a standard ASN.1 type intended
for representation of dates and time. UTCTime specifies the year for representation of dates and time. UTCTime specifies the year
through the two low order digits and time is specified to the preci- through the two low order digits and time is specified to the
sion of one minute or one second. UTCTime includes either Z (for precision of one minute or one second. UTCTime includes either Z
Zulu, or Greenwich Mean Time) or a time differential. (for Zulu, or Greenwich Mean Time) or a time differential.
For the purposes of this profile, UTCTime values MUST be expressed For the purposes of this profile, UTCTime values MUST be expressed
Greenwich Mean Time (Zulu) and MUST include seconds (i.e., times are Greenwich Mean Time (Zulu) and MUST include seconds (i.e., times are
YYMMDDHHMMSSZ), even where the number of seconds is zero. Conforming YYMMDDHHMMSSZ), even where the number of seconds is zero. Conforming
systems MUST interpret the year field (YY) as follows: systems MUST interpret the year field (YY) as follows:
Where YY is greater than or equal to 50, the year shall be inter- Where YY is greater than or equal to 50, the year shall be
preted as 19YY; and interpreted as 19YY; and
Where YY is less than 50, the year shall be interpreted as 20YY. Where YY is less than 50, the year shall be interpreted as 20YY.
4.1.2.5.2 GeneralizedTime 4.1.2.5.2 GeneralizedTime
The generalized time type, GeneralizedTime, is a standard ASN.1 type The generalized time type, GeneralizedTime, is a standard ASN.1 type
for variable precision representation of time. Optionally, the Gen- for variable precision representation of time. Optionally, the
eralizedTime field can include a representation of the time differen- GeneralizedTime field can include a representation of the time
tial between local and Greenwich Mean Time. differential between local and Greenwich Mean Time.
For the purposes of this profile, GeneralizedTime values MUST be For the purposes of this profile, GeneralizedTime values MUST be
expressed Greenwich Mean Time (Zulu) and MUST include seconds (i.e., expressed Greenwich Mean Time (Zulu) and MUST include seconds (i.e.,
times are YYYYMMDDHHMMSSZ), even where the number of seconds is zero. times are YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
GeneralizedTime values MUST NOT include fractional seconds. GeneralizedTime values MUST NOT include fractional seconds.
4.1.2.6 Subject 4.1.2.6 Subject
The subject field identifies the entity associated with the public The subject field identifies the entity associated with the public
key stored in the subject public key field. The subject name may be key stored in the subject public key field. The subject name may be
carried in the subject field and/or the subjectAltName extension. If carried in the subject field and/or the subjectAltName extension. If
the subject is a CA (e.g., the basic constraints extension, as dis- the subject is a CA (e.g., the basic constraints extension, as
cussed in 4.2.1.10, is present and the value of cA is TRUE,) then the discussed in 4.2.1.10, is present and the value of cA is TRUE,) then
subject field MUST be populated with a non-empty distinguished name the subject field MUST be populated with a non-empty distinguished
matching the contents of the issuer field (see sec. 4.1.2.4) in all name matching the contents of the issuer field (see sec. 4.1.2.4) in
certificates issued by the subject CA. If subject naming information all certificates issued by the subject CA. If subject naming
is present only in the subjectAltName extension (e.g., a key bound information is present only in the subjectAltName extension (e.g., a
only to an email address or URI), then the subject name MUST be an key bound only to an email address or URI), then the subject name
empty sequence and the subjectAltName extension MUST be critical. MUST be an empty sequence and the subjectAltName extension MUST be
critical.
Where it is non-empty, the subject field MUST contain an X.500 dis- Where it is non-empty, the subject field MUST contain an X.500
tinguished name (DN). The DN MUST be unique for each subject entity distinguished name (DN). The DN MUST be unique for each subject
certified by the one CA as defined by the issuer name field. A CA may entity certified by the one CA as defined by the issuer name field. A
issue more than one certificate with the same DN to the same subject CA may issue more than one certificate with the same DN to the same
entity. subject entity.
The subject name field is defined as the X.501 type Name. Implemen- The subject name field is defined as the X.501 type Name.
tation requirements for this field are those defined for the issuer Implementation requirements for this field are those defined for the
field (see sec. 4.1.2.4). When encoding attribute values of type issuer field (see sec. 4.1.2.4). When encoding attribute values of
DirectoryString, the encoding rules for the issuer field MUST be type DirectoryString, the encoding rules for the issuer field MUST be
implemented. Implementations of this specification MUST be prepared implemented. Implementations of this specification MUST be prepared
to receive subject names containing the attribute types required for to receive subject names containing the attribute types required for
the issuer field. Implementations of this specification SHOULD be the issuer field. Implementations of this specification SHOULD be
prepared to receive subject names containing the recommended attri- prepared to receive subject names containing the recommended
bute types for the issuer field. The syntax and associated object attribute types for the issuer field. The syntax and associated
identifiers (OIDs) for these attribute types are provided in the object identifiers (OIDs) for these attribute types are provided in
ASN.1 modules in Appendices A and B. Implementations of this specif- the ASN.1 modules in Appendices A and B. Implementations of this
ication MAY use these comparison rules to process unfamiliar attri- specification MAY use these comparison rules to process unfamiliar
bute types (i.e., for name chaining). This allows implementations to attribute types (i.e., for name chaining). This allows
process certificates with unfamiliar attributes in the subject name. implementations to process certificates with unfamiliar attributes in
the subject name.
In addition, legacy implementations exist where an RFC 822 name is In addition, legacy implementations exist where an RFC 822 name is
embedded in the subject distinguished name as an EmailAddress attri- embedded in the subject distinguished name as an EmailAddress
bute. The attribute value for EmailAddress is of type IA5String to attribute. The attribute value for EmailAddress is of type IA5String
permit inclusion of the character '@', which is not part of the to permit inclusion of the character '@', which is not part of the
PrintableString character set. EmailAddress attribute values are not PrintableString character set. EmailAddress attribute values are not
case sensitive (e.g., "fanfeedback@redsox.com" is the same as case sensitive (e.g., "fanfeedback@redsox.com" is the same as
"FANFEEDBACK@REDSOX.COM"). "FANFEEDBACK@REDSOX.COM").
Conforming implementations generating new certificates with elec- Conforming implementations generating new certificates with
tronic mail addresses MUST use the rfc822Name in the subject alterna- electronic mail addresses MUST use the rfc822Name in the subject
tive name field (see sec. 4.2.1.7) to describe such identities. alternative name field (see sec. 4.2.1.7) to describe such
Simultaneous inclusion of the EmailAddress attribute in the subject identities. Simultaneous inclusion of the EmailAddress attribute in
distinguished name to support legacy implementations is deprecated the subject distinguished name to support legacy implementations is
but permitted. deprecated but permitted.
4.1.2.7 Subject Public Key Info 4.1.2.7 Subject Public Key Info
This field is used to carry the public key and identify the algorithm This field is used to carry the public key and identify the algorithm
with which the key is used. The algorithm is identified using the with which the key is used. The algorithm is identified using the
AlgorithmIdentifier structure specified in section 4.1.1.2. The AlgorithmIdentifier structure specified in section 4.1.1.2. The
object identifiers for the supported algorithms and the methods for object identifiers for the supported algorithms and the methods for
encoding the public key materials (public key and parameters) are encoding the public key materials (public key and parameters) are
specified in [PKIX ALGS]. specified in [PKIX ALGS].
4.1.2.8 Unique Identifiers 4.1.2.8 Unique Identifiers
These fields may only appear if the version is 2 or 3 (see sec. These fields may only appear if the version is 2 or 3 (see sec.
4.1.2.1). The subject and issuer unique identifiers are present in 4.1.2.1). The subject and issuer unique identifiers are present in
the certificate to handle the possibility of reuse of subject and/or the certificate to handle the possibility of reuse of subject and/or
issuer names over time. This profile recommends that names not be issuer names over time. This profile recommends that names not be
reused for different entities and that Internet certificates not make reused for different entities and that Internet certificates not make
use of unique identifiers. CAs conforming to this profile SHOULD NOT use of unique identifiers. CAs conforming to this profile SHOULD NOT
generate certificates with unique identifiers. Applications conform- generate certificates with unique identifiers. Applications
ing to this profile SHOULD be capable of parsing unique identifiers conforming to this profile SHOULD be capable of parsing unique
and making comparisons. identifiers and making comparisons.
4.1.2.9 Extensions 4.1.2.9 Extensions
This field may only appear if the version is 3 (see sec. 4.1.2.1). This field may only appear if the version is 3 (see sec. 4.1.2.1).
If present, this field is a SEQUENCE of one or more certificate If present, this field is a SEQUENCE of one or more certificate
extensions. The format and content of certificate extensions in the extensions. The format and content of certificate extensions in the
Internet PKI is defined in section 4.2. Internet PKI is defined in section 4.2.
4.2 Standard Certificate Extensions 4.2 Standard Certificate Extensions
The extensions defined for X.509 v3 certificates provide methods for The extensions defined for X.509 v3 certificates provide methods for
associating additional attributes with users or public keys and for associating additional attributes with users or public keys and for
managing the certification hierarchy. The X.509 v3 certificate for- managing the certification hierarchy. The X.509 v3 certificate
mat also allows communities to define private extensions to carry format also allows communities to define private extensions to carry
information unique to those communities. Each extension in a certi- information unique to those communities. Each extension in a
ficate may be designated as critical or non-critical. A certificate certificate may be designated as critical or non-critical. A
using system MUST reject the certificate if it encounters a critical certificate using system MUST reject the certificate if it encounters
extension it does not recognize; however, a non-critical extension a critical extension it does not recognize; however, a non-critical
may be ignored if it is not recognized. The following sections extension may be ignored if it is not recognized. The following
present recommended extensions used within Internet certificates and sections present recommended extensions used within Internet
standard locations for information. Communities may elect to use certificates and standard locations for information. Communities may
additional extensions; however, caution should be exercised in adopt- elect to use additional extensions; however, caution should be
ing any critical extensions in certificates which might prevent use exercised in adopting any critical extensions in certificates which
in a general context. might prevent use in a general context.
Each extension includes an OID and an ASN.1 structure. When an Each extension includes an OID and an ASN.1 structure. When an
extension appears in a certificate, the OID appears as the field extension appears in a certificate, the OID appears as the field
extnID and the corresponding ASN.1 encoded structure is the value of extnID and the corresponding ASN.1 encoded structure is the value of
the octet string extnValue. Only one instance of a particular exten- the octet string extnValue. Only one instance of a particular
sion may appear in a particular certificate. For example, a certifi- extension may appear in a particular certificate. For example, a
cate may contain only one authority key identifier extension (see certificate may contain only one authority key identifier extension
sec. 4.2.1.1). An extension includes the boolean critical, with a (see sec. 4.2.1.1). An extension includes the boolean critical, with
default value of FALSE. The text for each extension specifies the a default value of FALSE. The text for each extension specifies the
acceptable values for the critical field. acceptable values for the critical field.
Conforming CAs MUST support key identifiers (see sec. 4.2.1.1 and Conforming CAs MUST support key identifiers (see sec. 4.2.1.1 and
4.2.1.2), basic constraints (see sec. 4.2.1.10), key usage (see sec. 4.2.1.2), basic constraints (see sec. 4.2.1.10), key usage (see sec.
4.2.1.3), and certificate policies (see sec. 4.2.1.5) extensions. If 4.2.1.3), and certificate policies (see sec. 4.2.1.5) extensions. If
the CA issues certificates with an empty sequence for the subject the CA issues certificates with an empty sequence for the subject
field, the CA MUST support the subject alternative name extension field, the CA MUST support the subject alternative name extension
(see sec. 4.2.1.7). Support for the remaining extensions is (see sec. 4.2.1.7). Support for the remaining extensions is
OPTIONAL. Conforming CAs may support extensions that are not identi- OPTIONAL. Conforming CAs may support extensions that are not
fied within this specification; certificate issuers are cautioned identified within this specification; certificate issuers are
that marking such extensions as critical may inhibit interoperabil- cautioned that marking such extensions as critical may inhibit
ity. interoperability.
At a minimum, applications conforming to this profile MUST recognize At a minimum, applications conforming to this profile MUST recognize
the following extensions: key usage (see sec. 4.2.1.3), certificate the following extensions: key usage (see sec. 4.2.1.3), certificate
policies (see sec. 4.2.1.5), the subject alternative name (see sec. policies (see sec. 4.2.1.5), the subject alternative name (see sec.
4.2.1.7), basic constraints (see sec. 4.2.1.10), name constraints 4.2.1.7), basic constraints (see sec. 4.2.1.10), name constraints
(see sec. 4.2.1.11), policy constraints (see sec. 4.2.1.12), and (see sec. 4.2.1.11), policy constraints (see sec. 4.2.1.12), extended
extended key usage (see sec. 4.2.1.13). key usage (see sec. 4.2.1.13), and inhibit any-policy (see sec.
4.2.1.15).
In addition, this profile RECOMMENDS application support for the In addition, this profile RECOMMENDS application support for the
authority and subject key identifier (see sec. 4.2.1.1 and 4.2.1.2), authority and subject key identifier (see sec. 4.2.1.1 and 4.2.1.2),
and inhibit any-policy (see sec. 4.2.1.15) extensions. and policy mapping (see sec. 4.2.1.6) extensions.
4.2.1 Standard Extensions 4.2.1 Standard Extensions
This section identifies standard certificate extensions defined in This section identifies standard certificate extensions defined in
[X.509] for use in the Internet PKI. Each extension is associated [X.509] for use in the Internet PKI. Each extension is associated
with an OID defined in [X.509]. These OIDs are members of the id-ce with an OID defined in [X.509]. These OIDs are members of the id-ce
arc, which is defined by the following: arc, which is defined by the following:
id-ce OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29} id-ce OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29}
4.2.1.1 Authority Key Identifier 4.2.1.1 Authority Key Identifier
The authority key identifier extension provides a means of identify- The authority key identifier extension provides a means of
ing the public key corresponding to the private key used to sign a identifying the public key corresponding to the private key used to
certificate. This extension is used where an issuer has multiple sign a certificate. This extension is used where an issuer has
signing keys (either due to multiple concurrent key pairs or due to multiple signing keys (either due to multiple concurrent key pairs or
changeover). The identification may be based on either the key iden- due to changeover). The identification may be based on either the
tifier (the subject key identifier in the issuer's certificate) or on key identifier (the subject key identifier in the issuer's
the issuer name and serial number. certificate) or on the issuer name and serial number.
The keyIdentifier field of the authorityKeyIdentifier extension MUST The keyIdentifier field of the authorityKeyIdentifier extension MUST
be included in all certificates generated by conforming CAs to facil- be included in all certificates generated by conforming CAs to
itate chain building. There is one exception; where a CA distributes facilitate chain building. There is one exception; where a CA
its public key in the form of a "self-signed" certificate, the distributes its public key in the form of a "self-signed"
authority key identifier may be omitted. In this case, the subject certificate, the authority key identifier may be omitted. In this
and authority key identifiers would be identical. case, the subject and authority key identifiers would be identical.
The value of the keyIdentifier field SHOULD be derived from the pub- The value of the keyIdentifier field SHOULD be derived from the
lic key used to verify the certificate's signature or a method that public key used to verify the certificate's signature or a method
generates unique values. Two common methods for generating key iden- that generates unique values. Two common methods for generating key
tifiers from the public key are described in (sec. 4.2.1.2). One com- identifiers from the public key are described in (sec. 4.2.1.2). One
mon method for generating unique values is described in (sec. common method for generating unique values is described in (sec.
4.2.1.2). Where a key identifier has not been previously esta- 4.2.1.2). Where a key identifier has not been previously
blished, this specification recommends use of one of these methods established, this specification recommends use of one of these
for generating keyIdentifiers. methods for generating keyIdentifiers.
This profile recommends support for the key identifier method by all This profile recommends support for the key identifier method by all
certificate users. certificate users.
This extension MUST NOT be marked critical. This extension MUST NOT be marked critical.
id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 35 } id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 35 }
AuthorityKeyIdentifier ::= SEQUENCE { AuthorityKeyIdentifier ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL, keyIdentifier [0] KeyIdentifier OPTIONAL,
skipping to change at page 27, line 50 skipping to change at page 28, line 21
methods for generating key identifiers from the public key are: methods for generating key identifiers from the public key are:
(1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the (1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the
value of the BIT STRING subjectPublicKey (excluding the tag, value of the BIT STRING subjectPublicKey (excluding the tag,
length, and number of unused bits). length, and number of unused bits).
(2) The keyIdentifier is composed of a four bit type field with (2) The keyIdentifier is composed of a four bit type field with
the value 0100 followed by the least significant 60 bits of the the value 0100 followed by the least significant 60 bits of the
SHA-1 hash of the value of the BIT STRING subjectPublicKey. SHA-1 hash of the value of the BIT STRING subjectPublicKey.
One common method for generating unique values is a monotomically One common method for generating unique values is a monotonically
increasing sequence of integers. increasing sequence of integers.
For end entity certificates, the subject key identifier extension For end entity certificates, the subject key identifier extension
provides a means for identifying certificates containing the particu- provides a means for identifying certificates containing the
lar public key used in an application. Where an end entity has particular public key used in an application. Where an end entity has
obtained multiple certificates, especially from multiple CAs, the obtained multiple certificates, especially from multiple CAs, the
subject key identifier provides a means to quickly identify the set subject key identifier provides a means to quickly identify the set
of certificates containing a particular public key. To assist appli- of certificates containing a particular public key. To assist
cations in identificiation the appropriate end entity certificate, applications in identifying the appropriate end entity certificate,
this extension SHOULD be included in all end entity certificates. this extension SHOULD be included in all end entity certificates.
For end entity certificates, subject key identifiers SHOULD be For end entity certificates, subject key identifiers SHOULD be
derived from the public key. Two common methods for generating key derived from the public key. Two common methods for generating key
identifiers from the public key are identifed above. identifiers from the public key are identifed above.
Where a key identifier has not been previously established, this Where a key identifier has not been previously established, this
specification recommends use of one of these methods for generating specification recommends use of one of these methods for generating
keyIdentifiers. keyIdentifiers.
This extension MUST NOT be marked critical. This extension MUST NOT be marked critical.
id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 14 } id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 14 }
SubjectKeyIdentifier ::= KeyIdentifier SubjectKeyIdentifier ::= KeyIdentifier
4.2.1.3 Key Usage 4.2.1.3 Key Usage
The key usage extension defines the purpose (e.g., encipherment, sig- The key usage extension defines the purpose (e.g., encipherment,
nature, certificate signing) of the key contained in the certificate. signature, certificate signing) of the key contained in the
The usage restriction might be employed when a key that could be used certificate. The usage restriction might be employed when a key that
for more than one operation is to be restricted. For example, when could be used for more than one operation is to be restricted. For
an RSA key should be used only for signing, the digitalSignature example, when an RSA key should be used only for signing, the
and/or nonRepudiation bits would be asserted. Likewise, when an RSA digitalSignature and/or nonRepudiation bits would be asserted.
key should be used only for key management, the keyEncipherment bit Likewise, when an RSA key should be used only for key management, the
would be asserted. When used, this extension SHOULD be marked criti- keyEncipherment bit would be asserted. When used, this extension
cal. SHOULD be marked critical.
id-ce-keyUsage OBJECT IDENTIFIER ::= { id-ce 15 } id-ce-keyUsage OBJECT IDENTIFIER ::= { id-ce 15 }
KeyUsage ::= BIT STRING { KeyUsage ::= BIT STRING {
digitalSignature (0), digitalSignature (0),
nonRepudiation (1), nonRepudiation (1),
keyEncipherment (2), keyEncipherment (2),
dataEncipherment (3), dataEncipherment (3),
keyAgreement (4), keyAgreement (4),
keyCertSign (5), keyCertSign (5),
cRLSign (6), cRLSign (6),
encipherOnly (7), encipherOnly (7),
decipherOnly (8) } decipherOnly (8) }
Bits in the KeyUsage type are used as follows: Bits in the KeyUsage type are used as follows:
The digitalSignature bit is asserted when the subject public key The digitalSignature bit is asserted when the subject public key
is used with a digital signature mechanism to support security is used with a digital signature mechanism to support security
services other than non-repudiation (bit 1), certificate signing services other than non-repudiation (bit 1), certificate signing
(bit 5), or revocation information signing (bit 6). Digital signa- (bit 5), or revocation information signing (bit 6). Digital
ture mechanisms are often used for entity authentication and data signature mechanisms are often used for entity authentication and
origin authentication with integrity. data origin authentication with integrity.
The nonRepudiation bit is asserted when the subject public key is The nonRepudiation bit is asserted when the subject public key is
used to verify digital signatures used to provide a non- used to verify digital signatures used to provide a non-
repudiation service which protects against the signing entity repudiation service which protects against the signing entity
falsely denying some action, excluding certificate or CRL signing. falsely denying some action, excluding certificate or CRL signing.
In the case of later conflict, a reliable third party may deter- In the case of later conflict, a reliable third party may
mine the authenticity of the signed data. determine the authenticity of the signed data.
Further distinctions between the digitalSignature and nonRepudia- Further distinctions between the digitalSignature and
tion bits may be provided in specific certificate policies. nonRepudiation bits may be provided in specific certificate
policies.
The keyEncipherment bit is asserted when the subject public key is The keyEncipherment bit is asserted when the subject public key is
used for key transport. For example, when an RSA key is to be used for key transport. For example, when an RSA key is to be
used for key management, then this bit shall asserted. used for key management, then this bit shall asserted.
The dataEncipherment bit is asserted when the subject public key The dataEncipherment bit is asserted when the subject public key
is used for enciphering user data, other than cryptographic keys. is used for enciphering user data, other than cryptographic keys.
The keyAgreement bit is asserted when the subject public key is The keyAgreement bit is asserted when the subject public key is
used for key agreement. For example, when a Diffie-Hellman key is used for key agreement. For example, when a Diffie-Hellman key is
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the keyAgreement bit is also set, the subject public key may be the keyAgreement bit is also set, the subject public key may be
used only for deciphering data while performing key agreement. used only for deciphering data while performing key agreement.
This profile does not restrict the combinations of bits that may be This profile does not restrict the combinations of bits that may be
set in an instantiation of the keyUsage extension. However, set in an instantiation of the keyUsage extension. However,
appropriate values for keyUsage extensions for particular algorithms appropriate values for keyUsage extensions for particular algorithms
are specified in [PKIX ALGS]. are specified in [PKIX ALGS].
4.2.1.4 Private Key Usage Period 4.2.1.4 Private Key Usage Period
This profile recommends against the use of this extension. CAs con- This profile recommends against the use of this extension. CAs
forming to this profile MUST NOT generate certificates with critical conforming to this profile MUST NOT generate certificates with
private key usage period extensions. critical private key usage period extensions.
The private key usage period extension allows the certificate issuer The private key usage period extension allows the certificate issuer
to specify a different validity period for the private key than the to specify a different validity period for the private key than the
certificate. This extension is intended for use with digital signa- certificate. This extension is intended for use with digital
ture keys. This extension consists of two optional components, signature keys. This extension consists of two optional components,
notBefore and notAfter. The private key associated with the certifi- notBefore and notAfter. The private key associated with the
cate should not be used to sign objects before or after the times certificate should not be used to sign objects before or after the
specified by the two components, respectively. CAs conforming to this times specified by the two components, respectively. CAs conforming
profile MUST NOT generate certificates with private key usage period to this profile MUST NOT generate certificates with private key usage
extensions unless at least one of the two components is present. period extensions unless at least one of the two components is
present.
Where used, notBefore and notAfter are represented as GeneralizedTime Where used, notBefore and notAfter are represented as GeneralizedTime
and MUST be specified and interpreted as defined in section and MUST be specified and interpreted as defined in section
4.1.2.5.2. 4.1.2.5.2.
id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= { id-ce 16 } id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= { id-ce 16 }
PrivateKeyUsagePeriod ::= SEQUENCE { PrivateKeyUsagePeriod ::= SEQUENCE {
notBefore [0] GeneralizedTime OPTIONAL, notBefore [0] GeneralizedTime OPTIONAL,
notAfter [1] GeneralizedTime OPTIONAL } notAfter [1] GeneralizedTime OPTIONAL }
4.2.1.5 Certificate Policies 4.2.1.5 Certificate Policies
The certificate policies extension contains a sequence of one or more The certificate policies extension contains a sequence of one or more
policy information terms, each of which consists of an object iden- policy information terms, each of which consists of an object
tifier (OID) and optional qualifiers. Optional qualifiers, which may identifier (OID) and optional qualifiers. Optional qualifiers, which
be present, are not expected to change the definition of the policy. may be present, are not expected to change the definition of the
policy.
In an end-entity certificate, these policy information terms indicate In an end-entity certificate, these policy information terms indicate
the policy under which the certificate has been issued and the pur- the policy under which the certificate has been issued and the
poses for which the certificate may be used. In a CA certificate, purposes for which the certificate may be used. In a CA certificate,
these policy information terms limit the set of policies for certifi- these policy information terms limit the set of policies for
cation paths which include this certificate. When a CA does not wish certification paths which include this certificate. When a CA does
to limit the set of policies for certification paths which include not wish to limit the set of policies for certification paths which
this certificate, they may assert the special policy anyPolicy, with include this certificate, they may assert the special policy
a value of {2 5 29 32 0}. anyPolicy, with a value of {2 5 29 32 0}.
Applications with specific policy requirements are expected to have a Applications with specific policy requirements are expected to have a
list of those policies which they will accept and to compare the pol- list of those policies which they will accept and to compare the
icy OIDs in the certificate to that list. If this extension is crit- policy OIDs in the certificate to that list. If this extension is
ical, the path validation software MUST be able to interpret this critical, the path validation software MUST be able to interpret this
extension (including the optional qualifier), or MUST reject the cer- extension (including the optional qualifier), or MUST reject the
tificate. certificate.
To promote interoperability, this profile RECOMMENDS that policy To promote interoperability, this profile RECOMMENDS that policy
information terms consist of only an OID. Where an OID alone is information terms consist of only an OID. Where an OID alone is
insufficient, this profile strongly recommends that use of qualifiers insufficient, this profile strongly recommends that use of qualifiers
be limited to those identified in this section. When qualifiers are be limited to those identified in this section. When qualifiers are
used with the special policy anyPolicy, they MUST be limited to the used with the special policy anyPolicy, they MUST be limited to the
qualifers identified in this section. qualifers identified in this section.
This specification defines two policy qualifier types for use by cer- This specification defines two policy qualifier types for use by
tificate policy writers and certificate issuers. The qualifier types certificate policy writers and certificate issuers. The qualifier
are the CPS Pointer and User Notice qualifiers. types are the CPS Pointer and User Notice qualifiers.
The CPS Pointer qualifier contains a pointer to a Certification Prac- The CPS Pointer qualifier contains a pointer to a Certification
tice Statement (CPS) published by the CA. The pointer is in the form Practice Statement (CPS) published by the CA. The pointer is in the
of a URI. form of a URI. Processing requirements for this qualifier are a
local matter. No action is mandated by this specification regardless
of the criticality value asserted for the extension.
User notice is intended for display to a relying party when a certi- User notice is intended for display to a relying party when a
ficate is used. The application software SHOULD display all user certificate is used. The application software SHOULD display all
notices in all certificates of the certification path used, except user notices in all certificates of the certification path used,
that if a notice is duplicated only one copy need be displayed. To except that if a notice is duplicated only one copy need be
prevent such duplication, this qualifier SHOULD only be present in displayed. To prevent such duplication, this qualifier SHOULD only
end-entity certificates and CA certificates issued to other organiza- be present in end-entity certificates and CA certificates issued to
tions. other organizations.
The user notice has two optional fields: the noticeRef field and the The user notice has two optional fields: the noticeRef field and the
explicitText field. explicitText field.
The noticeRef field, if used, names an organization and identi- The noticeRef field, if used, names an organization and
fies, by number, a particular textual statement prepared by that identifies, by number, a particular textual statement prepared by
organization. For example, it might identify the organization that organization. For example, it might identify the
"CertsRUs" and notice number 1. In a typical implementation, the organization "CertsRUs" and notice number 1. In a typical
application software will have a notice file containing the implementation, the application software will have a notice file
current set of notices for CertsRUs; the application will extract containing the current set of notices for CertsRUs; the
the notice text from the file and display it. Messages may be application will extract the notice text from the file and display
multilingual, allowing the software to select the particular it. Messages may be multilingual, allowing the software to select
language message for its own environment. the particular language message for its own environment.
An explicitText field includes the textual statement directly in An explicitText field includes the textual statement directly in
the certificate. The explicitText field is a string with a max- the certificate. The explicitText field is a string with a
imum size of 200 characters. maximum size of 200 characters.
If both the noticeRef and explicitText options are included in the If both the noticeRef and explicitText options are included in the
one qualifier and if the application software can locate the notice one qualifier and if the application software can locate the notice
text indicated by the noticeRef option then that text should be text indicated by the noticeRef option then that text should be
displayed; otherwise, the explicitText string should be displayed. displayed; otherwise, the explicitText string should be displayed.
id-ce-certificatePolicies OBJECT IDENTIFIER ::= { id-ce 32 } id-ce-certificatePolicies OBJECT IDENTIFIER ::= { id-ce 32 }
anyPolicy OBJECT IDENTIFIER ::= {id-ce-certificate-policies 0} anyPolicy OBJECT IDENTIFIER ::= {id-ce-certificate-policies 0}
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DisplayText ::= CHOICE { DisplayText ::= CHOICE {
ia5String IA5String (SIZE (1..200)), ia5String IA5String (SIZE (1..200)),
visibleString VisibleString (SIZE (1..200)), visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)), bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200)) } utf8String UTF8String (SIZE (1..200)) }
4.2.1.6 Policy Mappings 4.2.1.6 Policy Mappings
This extension is used in CA certificates. It lists one or more This extension is used in CA certificates. It lists one or more
pairs of OIDs; each pair includes an issuerDomainPolicy and a sub- pairs of OIDs; each pair includes an issuerDomainPolicy and a
jectDomainPolicy. The pairing indicates the issuing CA considers its subjectDomainPolicy. The pairing indicates the issuing CA considers
issuerDomainPolicy equivalent to the subject CA's subjectDomainPol- its issuerDomainPolicy equivalent to the subject CA's
icy. subjectDomainPolicy.
The issuing CA's users may accept an issuerDomainPolicy for certain The issuing CA's users may accept an issuerDomainPolicy for certain
applications. The policy mapping tells the issuing CA's users which applications. The policy mapping tells the issuing CA's users which
policies associated with the subject CA are comparable to the policy policies associated with the subject CA are comparable to the policy
they accept. they accept.
Policies should not be mapped either to or from the special value Each issuerDomainPolicy named in the the policy mapping extension
anyPolicy. (see 4.2.1.5 certificate policies). should also be asserted in a certificate policies extension in the
same certificate. Policies should not be mapped either to or from
the special value anyPolicy. (See 4.2.1.5 certificate policies).
This extension may be supported by CAs and/or applications, and it This extension may be supported by CAs and/or applications, and it
MUST be non-critical. MUST be non-critical.
id-ce-policyMappings OBJECT IDENTIFIER ::= { id-ce 33 } id-ce-policyMappings OBJECT IDENTIFIER ::= { id-ce 33 }
PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE { PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
issuerDomainPolicy CertPolicyId, issuerDomainPolicy CertPolicyId,
subjectDomainPolicy CertPolicyId } subjectDomainPolicy CertPolicyId }
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such identities are to be bound into a certificate, the subject such identities are to be bound into a certificate, the subject
alternative name (or issuer alternative name) extension MUST be used. alternative name (or issuer alternative name) extension MUST be used.
Because the subject alternative name is considered to be definitively Because the subject alternative name is considered to be definitively
bound to the public key, all parts of the subject alternative name bound to the public key, all parts of the subject alternative name
MUST be verified by the CA. MUST be verified by the CA.
Further, if the only subject identity included in the certificate is Further, if the only subject identity included in the certificate is
an alternative name form (e.g., an electronic mail address), then the an alternative name form (e.g., an electronic mail address), then the
subject distinguished name MUST be empty (an empty sequence), and the subject distinguished name MUST be empty (an empty sequence), and the
subjectAltName extension MUST be present. If the subject field con- subjectAltName extension MUST be present. If the subject field
tains an empty sequence, the subjectAltName extension MUST be marked contains an empty sequence, the subjectAltName extension MUST be
critical. marked critical.
When the subjectAltName extension contains an Internet mail address, When the subjectAltName extension contains an Internet mail address,
the address MUST be included as an rfc822Name. The format of an the address MUST be included as an rfc822Name. The format of an
rfc822Name is an "addr-spec" as defined in RFC 822 [RFC 822]. An rfc822Name is an "addr-spec" as defined in RFC 822 [RFC 822]. An
addr-spec has the form "local-part@domain". Note that an addr-spec addr-spec has the form "local-part@domain". Note that an addr-spec
has no phrase (such as a common name) before it, has no comment (text has no phrase (such as a common name) before it, has no comment (text
surrounded in parentheses) after it, and is not surrounded by "<" and surrounded in parentheses) after it, and is not surrounded by "<" and
">". Note that while upper and lower case letters are allowed in an ">". Note that while upper and lower case letters are allowed in an
RFC 822 addr-spec, no significance is attached to the case. RFC 822 addr-spec, no significance is attached to the case.
When the subjectAltName extension contains a iPAddress, the address When the subjectAltName extension contains a iPAddress, the address
MUST be stored in the octet string in "network byte order," as speci- MUST be stored in the octet string in "network byte order," as
fied in RFC 791 [RFC 791]. The least significant bit (LSB) of each specified in RFC 791 [RFC 791]. The least significant bit (LSB) of
octet is the LSB of the corresponding byte in the network address. each octet is the LSB of the corresponding byte in the network
For IP Version 4, as specified in RFC 791, the octet string MUST con- address. For IP Version 4, as specified in RFC 791, the octet string
tain exactly four octets. For IP Version 6, as specified in RFC MUST contain exactly four octets. For IP Version 6, as specified in
1883, the octet string MUST contain exactly sixteen octets [RFC RFC 1883, the octet string MUST contain exactly sixteen octets [RFC
1883]. 1883].
When the subjectAltName extension contains a domain name service When the subjectAltName extension contains a domain name service
label, the domain name MUST be stored in the dNSName (an IA5String). label, the domain name MUST be stored in the dNSName (an IA5String).
The name MUST be in the "preferred name syntax," as specified by RFC The name MUST be in the "preferred name syntax," as specified by RFC
1034 [RFC 1034]. Note that while upper and lower case letters are 1034 [RFC 1034]. Note that while upper and lower case letters are
allowed in domain names, no signifigance is attached to the case. In allowed in domain names, no signifigance is attached to the case. In
addition, while the string " " is a legal domain name, subjectAltName addition, while the string " " is a legal domain name, subjectAltName
extensions with a dNSName " " are not permitted. Finally, the use of extensions with a dNSName " " are not permitted. Finally, the use of
the DNS representation for Internet mail addresses (wpolk.nist.gov the DNS representation for Internet mail addresses (wpolk.nist.gov
instead of wpolk@nist.gov) is not permitted; such identities are to instead of wpolk@nist.gov) MUST NOT be used; such identities are to
be encoded as rfc822Name. be encoded as rfc822Name.
Note: work is currently underway to specify domain names in interna- Note: work is currently underway to specify domain names in
tional character sets. This names will likely not be accomodated by international character sets. This names will likely not be
IA5String. Once this work is complete, this profile will be accomodated by IA5String. Once this work is complete, this profile
revisited and the appropriate functionality will be added. will be revisited and the appropriate functionality will be added.
When the subjectAltName extension contains a URI, the name MUST be When the subjectAltName extension contains a URI, the name MUST be
stored in the uniformResourceIdentifier (an IA5String). The name MUST stored in the uniformResourceIdentifier (an IA5String). The name MUST
be a non-relative URL, and MUST follow the URL syntax and encoding be a non-relative URL, and MUST follow the URL syntax and encoding
rules specified in [RFC 1738]. The name must include both a scheme rules specified in [RFC 1738]. The name must include both a scheme
(e.g., "http" or "ftp") and a scheme-specific-part. The scheme- (e.g., "http" or "ftp") and a scheme-specific-part. The scheme-
specific-part must include a fully qualified domain name or IP specific-part must include a fully qualified domain name or IP
address as the host. address as the host.
As specified in [RFC 1738], the scheme name is not case-sensitive As specified in [RFC 1738], the scheme name is not case-sensitive
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be case-sensitive. When comparing URIs, conforming implementations be case-sensitive. When comparing URIs, conforming implementations
MUST compare the scheme and host without regard to case, but assume MUST compare the scheme and host without regard to case, but assume
the remainder of the scheme-specific-part is case sensitive. the remainder of the scheme-specific-part is case sensitive.
When the subjectAltName extension contains a DN in the directoryName, When the subjectAltName extension contains a DN in the directoryName,
the DN MUST be unique for each subject entity certified by the one CA the DN MUST be unique for each subject entity certified by the one CA
as defined by the issuer name field. A CA may issue more than one as defined by the issuer name field. A CA may issue more than one
certificate with the same DN to the same subject entity. certificate with the same DN to the same subject entity.
The subjectAltName may carry additional name types through the use of The subjectAltName may carry additional name types through the use of
the otherName field. The format and semantics of the name are indi- the otherName field. The format and semantics of the name are
cated through the OBJECT IDENTIFIER in the type-id field. The name indicated through the OBJECT IDENTIFIER in the type-id field. The
itself is conveyed as value field in otherName. For example, Ker- name itself is conveyed as value field in otherName. For example,
beros [RFC 1510] format names can be encoded into the otherName, Kerberos [RFC 1510] format names can be encoded into the otherName,
using the krb5PrincipalName OID and the KerberosName syntax as using the krb5PrincipalName OID and the KerberosName syntax as
defined in [PKINIT]. defined in [PKINIT].
Subject alternative names may be constrained in the same manner as Subject alternative names may be constrained in the same manner as
subject distinguished names using the name constraints extension as subject distinguished names using the name constraints extension as
described in section 4.2.1.11. described in section 4.2.1.11.
If the subjectAltName extension is present, the sequence MUST contain If the subjectAltName extension is present, the sequence MUST contain
at least one entry. Unlike the subject field, conforming CAs MUST at least one entry. Unlike the subject field, conforming CAs MUST
NOT issue certificates with subjectAltNames containing empty General- NOT issue certificates with subjectAltNames containing empty
Name fields. For example, an rfc822Name is represented as an GeneralName fields. For example, an rfc822Name is represented as an
IA5String. While an empty string is a valid IA5String, such an IA5String. While an empty string is a valid IA5String, such an
rfc822Name is not permitted by this profile. The behavior of clients rfc822Name is not permitted by this profile. The behavior of clients
that encounter such a certificate when processing a certificication that encounter such a certificate when processing a certificication
path is not defined by this profile. path is not defined by this profile.
Finally, the semantics of subject alternative names that include Finally, the semantics of subject alternative names that include
wildcard characters (e.g., as a placeholder for a set of names) are wildcard characters (e.g., as a placeholder for a set of names) are
not addressed by this specification. Applications with specific not addressed by this specification. Applications with specific
requirements may use such names but shall define the semantics. requirements may use such names but shall define the semantics.
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be encoded as in 4.2.1.7. be encoded as in 4.2.1.7.
Where present, this extension SHOULD NOT be marked critical. Where present, this extension SHOULD NOT be marked critical.
id-ce-issuerAltName OBJECT IDENTIFIER ::= { id-ce 18 } id-ce-issuerAltName OBJECT IDENTIFIER ::= { id-ce 18 }
IssuerAltName ::= GeneralNames IssuerAltName ::= GeneralNames
4.2.1.9 Subject Directory Attributes 4.2.1.9 Subject Directory Attributes
The subject directory attributes extension is not recommended as an The subject directory attributes extension is used to convey
essential part of this profile, but it may be used in local environ- identification attributes (e.g.,nationality) of the subject. The
ments. This extension MUST be non-critical. extension is defined as a sequence of one or more attributes. This
extension MUST be non-critical.
id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= { id-ce 9 } id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= { id-ce 9 }
SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute
4.2.1.10 Basic Constraints 4.2.1.10 Basic Constraints
The basic constraints extension identifies whether the subject of the The basic constraints extension identifies whether the subject of the
certificate is a CA and how deep a certification path may exist certificate is a CA and how deep a certification path may exist
through that CA. through that CA.
The cA bit indicates if the certified public key may be used to ver- The cA bit indicates if the certified public key may be used to
ify signatures on other certificates. If the cA bit is asserted, then verify signatures on other certificates. If the cA bit is asserted,
the keyCertSign bit in the key usage extension (see 4.2.1.3) MUST then the keyCertSign bit in the key usage extension (see 4.2.1.3)
also be asserted. If the cA bit is not asserted, then the keyCertSign MUST also be asserted. If the cA bit is not asserted, then the
bit in the key usage extension MUST NOT be asserted. keyCertSign bit in the key usage extension MUST NOT be asserted.
The pathLenConstraint field is meaningful only if cA is set to TRUE. The pathLenConstraint field is meaningful only if cA is set to TRUE.
In this case, it gives the maximum number of CA certificates that may In this case, it gives the maximum number of CA certificates that may
follow this certificate in a certification path. (Note: One end- follow this certificate in a certification path. (Note: One end-
entity certificate will follow the final CA certificate in the path. entity certificate will follow the final CA certificate in the path.
The last certificate in a path is considered an end-entity certifi- The last certificate in a path is considered an end-entity
cate, whether the subject of the certificate is a CA or not.) A certificate, whether the subject of the certificate is a CA or not.)
pathLenConstrinat of zero indicates that only an end-entity certifi- A pathLenConstrinat of zero indicates that only an end-entity
cate may follow in the path. Where it appears, the pathLenConstraint certificate may follow in the path. Where it appears, the
field MUST be greater than or equal to zero. Where pathLenConstraint pathLenConstraint field MUST be greater than or equal to zero. Where
does not appear, there is no limit to the allowed length of the cer- pathLenConstraint does not appear, there is no limit to the allowed
tification path. length of the certification path.
This extension MUST appear as a critical extension in all CA certifi- This extension MUST appear as a critical extension in all CA
cates. This extension MAY appear as a critical or non-critical certificates. This extension MAY appear as a critical or non-
extension in end entity certificates. critical extension in end entity certificates.
id-ce-basicConstraints OBJECT IDENTIFIER ::= { id-ce 19 } id-ce-basicConstraints OBJECT IDENTIFIER ::= { id-ce 19 }
BasicConstraints ::= SEQUENCE { BasicConstraints ::= SEQUENCE {
cA BOOLEAN DEFAULT FALSE, cA BOOLEAN DEFAULT FALSE,
pathLenConstraint INTEGER (0..MAX) OPTIONAL } pathLenConstraint INTEGER (0..MAX) OPTIONAL }
4.2.1.11 Name Constraints 4.2.1.11 Name Constraints
The name constraints extension, which MUST be used only in a CA cer- The name constraints extension, which MUST be used only in a CA
tificate, indicates a name space within which all subject names in certificate, indicates a name space within which all subject names in
subsequent certificates in a certification path shall be located. subsequent certificates in a certification path shall be located.
Restrictions may apply to the subject distinguished name or subject Restrictions may apply to the subject distinguished name or subject
alternative names. Restrictions apply only when the specified name alternative names. Restrictions apply only when the specified name
form is present. If no name of the type is in the certificate, the form is present. If no name of the type is in the certificate, the
certificate is acceptable. certificate is acceptable.
Name constraints are not applied to certificates whose issuer and Name constraints are not applied to certificates whose issuer and
subject are identical. (This could prevent CAs that utilize name subject are identical. (This could prevent CAs that use name
constraints from issuing self-signed certificates to implement key constraints from issuing self-signed certificates to implement key
rollover.) rollover.)
Restrictions are defined in terms of permitted or excluded name sub- Restrictions are defined in terms of permitted or excluded name
trees. Any name matching a restriction in the excludedSubtrees field subtrees. Any name matching a restriction in the excludedSubtrees
is invalid regardless of information appearing in the permittedSub- field is invalid regardless of information appearing in the
trees. This extension MUST be critical. permittedSubtrees. This extension MUST be critical.
Within this profile, the minimum and maximum fields are not used with Within this profile, the minimum and maximum fields are not used with
any name forms, thus minimum is always zero, and maximum is always any name forms, thus minimum is always zero, and maximum is always
absent. absent.
For URIs, the constraint applies to the host part of the name. The For URIs, the constraint applies to the host part of the name. The
constraint may specify a host or a domain. Examples would be constraint may specify a host or a domain. Examples would be
"foo.bar.com"; and ".xyz.com". When the the constraint begins with "foo.bar.com"; and ".xyz.com". When the the constraint begins with
a period, it may be expanded with one or more subdomains. That is, a period, it may be expanded with one or more subdomains. That is,
the constraint ".xyz.com" is satisfied by both abc.xyz.com and the constraint ".xyz.com" is satisfied by both abc.xyz.com and
abc.def.xyz.com. However, the constraint ".xyz.com" is not satisfied abc.def.xyz.com. However, the constraint ".xyz.com" is not satisfied
by "xyz.com". When the constraint does not begin with a period, it by "xyz.com". When the constraint does not begin with a period, it
specifies a host. specifies a host.
A name constraint for Internat mail addresses may specify a particu- A name constraint for Internet mail addresses may specify a
lar mailbox, all addresses at a particular host, or all mailboxes in particular mailbox, all addresses at a particular host, or all
a domain. To indicate a particular mailbox, the constraint is the mailboxes in a domain. To indicate a particular mailbox, the
complete mail address. For example, "root@xyz.com" indicates the constraint is the complete mail address. For example, "root@xyz.com"
root mailbox on the host "xyz.com". To indicate all Internet mail indicates the root mailbox on the host "xyz.com". To indicate all
addresses on a particular host, the constraint is specified as the Internet mail addresses on a particular host, the constraint is
host name. For example, the constraint "xyz.com" is satisfied by any specified as the host name. For example, the constraint "xyz.com" is
mail address at the host "xyz.com". To specify any address within a satisfied by any mail address at the host "xyz.com". To specify any
domain, the constraint is specified with a leading period (as with address within a domain, the constraint is specified with a leading
URIs). For example, ".xyz.com" indicates all the Internet mail period (as with URIs). For example, ".xyz.com" indicates all the
addresses in the domain "xyz.com", but not Internet mail addresses on Internet mail addresses in the domain "xyz.com", but not Internet
the host "xyz.com". mail addresses on the host "xyz.com".
DNS name restrictions are expressed as foo.bar.com. Any DNS name that DNS name restrictions are expressed as foo.bar.com. Any DNS name that
can be constructed by simply adding to the left hand side of the name can be constructed by simply adding to the left hand side of the name
satisfies the name constraint. For example, www.foo.bar.com would satisfies the name constraint. For example, www.foo.bar.com would
satisfy the constraint but foo1.bar.com would not. satisfy the constraint but foo1.bar.com would not.
Legacy implementations exist where an RFC 822 name is embedded in the Legacy implementations exist where an RFC 822 name is embedded in the
subject distinguished name in an attribute of type EmailAddress (see subject distinguished name in an attribute of type EmailAddress (see
sec. 4.1.2.6). When rfc822 names are constrained, but the certificate sec. 4.1.2.6). When rfc822 names are constrained, but the certificate
does not include a subject alternative name, the rfc822 name con- does not include a subject alternative name, the rfc822 name
straint MUST be applied to the attribute of type EmailAddress in the constraint MUST be applied to the attribute of type EmailAddress in
subject distinguished name. The ASN.1 syntax for EmailAddress and the subject distinguished name. The ASN.1 syntax for EmailAddress
the corresponding OID are supplied in Appendix A and B. and the corresponding OID are supplied in Appendix A and B.
Restrictions of the form directoryName MUST be applied to the subject Restrictions of the form directoryName MUST be applied to the subject
field in the certificate and to the subjectAltName extensions of type field in the certificate and to the subjectAltName extensions of type
directoryName. Restrictions of the form x400Address MUST be applied directoryName. Restrictions of the form x400Address MUST be applied
to subjectAltName extensions of type x400Address. to subjectAltName extensions of type x400Address.
When applying restrictions of the form directoryName, an implementa- When applying restrictions of the form directoryName, an
tion MUST compare DN attributes. At a minimum, implementations MUST implementation MUST compare DN attributes. At a minimum,
perform the DN comparison rules specified in Section 4.1.2.4. CAs implementations MUST perform the DN comparison rules specified in
issuing certificates with a restriction of the form directoryName Section 4.1.2.4. CAs issuing certificates with a restriction of the
SHOULD NOT rely on implementation of the full ISO DN name comparison form directoryName SHOULD NOT rely on implementation of the full ISO
algorithm. This implies name restrictions shall be stated identi- DN name comparison algorithm. This implies name restrictions shall
cally to the encoding used in the subject field or subjectAltName be stated identically to the encoding used in the subject field or
extension. subjectAltName extension.
The syntax of iPAddress MUST be as described in section 4.2.1.7 with The syntax of iPAddress MUST be as described in section 4.2.1.7 with
the following additions specifically for Name Constraints. For IPv4 the following additions specifically for Name Constraints. For IPv4
addresses, the ipAddress field of generalName MUST contain eight (8) addresses, the ipAddress field of generalName MUST contain eight (8)
octets, encoded in the style of RFC 1519 (CIDR) to represent an octets, encoded in the style of RFC 1519 (CIDR) to represent an
address range.[RFC 1519] For IPv6 addresses, the ipAddress field address range.[RFC 1519] For IPv6 addresses, the ipAddress field
MUST contain 32 octets similarly encoded. For example, a name con- MUST contain 32 octets similarly encoded. For example, a name
straint for "class C" subnet 10.9.8.0 shall be represented as the constraint for "class C" subnet 10.9.8.0 shall be represented as the
octets 0A 09 08 00 FF FF FF 00, representing the CIDR notation octets 0A 09 08 00 FF FF FF 00, representing the CIDR notation
10.9.8.0/255.255.255.0. 10.9.8.0/255.255.255.0.
The syntax and semantics for name constraints for otherName, ediPar- The syntax and semantics for name constraints for otherName,
tyName, and registeredID are not defined by this specification. ediPartyName, and registeredID are not defined by this specification.
id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 } id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 }
NameConstraints ::= SEQUENCE { NameConstraints ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL, permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL } excludedSubtrees [1] GeneralSubtrees OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE { GeneralSubtree ::= SEQUENCE {
skipping to change at page 39, line 34 skipping to change at page 40, line 14
minimum [0] BaseDistance DEFAULT 0, minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL } maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX) BaseDistance ::= INTEGER (0..MAX)
4.2.1.12 Policy Constraints 4.2.1.12 Policy Constraints
The policy constraints extension can be used in certificates issued The policy constraints extension can be used in certificates issued
to CAs. The policy constraints extension constrains path validation to CAs. The policy constraints extension constrains path validation
in two ways. It can be used to prohibit policy mapping or require in two ways. It can be used to prohibit policy mapping or require
that each certificate in a path contain an acceptable policy identif- that each certificate in a path contain an acceptable policy
ier. identifier.
If the inhibitPolicyMapping field is present, the value indicates the If the inhibitPolicyMapping field is present, the value indicates the
number of additional certificates that may appear in the path before number of additional certificates that may appear in the path before
policy mapping is no longer permitted. For example, a value of one policy mapping is no longer permitted. For example, a value of one
indicates that policy mapping may be processed in certificates issued indicates that policy mapping may be processed in certificates issued
by the subject of this certificate, but not in additional certifi- by the subject of this certificate, but not in additional
cates in the path. certificates in the path.
If the requireExplicitPolicy field is present, subsequent certifi- If the requireExplicitPolicy field is present, subsequent
cates shall include an acceptable policy identifier. The value of certificates shall include an acceptable policy identifier. The value
requireExplicitPolicy indicates the number of additional certificates of requireExplicitPolicy indicates the number of additional
that may appear in the path before an explicit policy is required. certificates that may appear in the path before an explicit policy is
An acceptable policy identifier is the identifier of a policy required. An acceptable policy identifier is the identifier of a
required by the user of the certification path or the identifier of a policy required by the user of the certification path or the
policy which has been declared equivalent through policy mapping. identifier of a policy which has been declared equivalent through
policy mapping.
Conforming CAs MUST NOT issue certificates where policy constraints Conforming CAs MUST NOT issue certificates where policy constraints
is a null sequence. That is, at least one of the inhibitPolicyMapping is a null sequence. That is, at least one of the inhibitPolicyMapping
field or the requireExplicitPolicy field MUST be present. The field or the requireExplicitPolicy field MUST be present. The
behavior of clients that encounter a null policy constraints field is behavior of clients that encounter a null policy constraints field is
not addressed in this profile. not addressed in this profile.
This extension may be critical or non-critical. This extension may be critical or non-critical.
id-ce-policyConstraints OBJECT IDENTIFIER ::= { id-ce 36 } id-ce-policyConstraints OBJECT IDENTIFIER ::= { id-ce 36 }
PolicyConstraints ::= SEQUENCE { PolicyConstraints ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL, requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL } inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX) SkipCerts ::= INTEGER (0..MAX)
4.2.1.13 Extended key usage field 4.2.1.13 Extended key usage field
This field indicates one or more purposes for which the certified This field indicates one or more purposes for which the certified
public key may be used, in addition to or in place of the basic pur- public key may be used, in addition to or in place of the basic
poses indicated in the key usage extension field. This field is purposes indicated in the key usage extension field. This field is
defined as follows: defined as follows:
id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37} id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37}
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
KeyPurposeId ::= OBJECT IDENTIFIER KeyPurposeId ::= OBJECT IDENTIFIER
Key purposes may be defined by any organization with a need. Object Key purposes may be defined by any organization with a need. Object
identifiers used to identify key purposes shall be assigned in accor- identifiers used to identify key purposes shall be assigned in
dance with IANA or ITU-T Rec. X.660 | ISO/IEC/ITU 9834-1. accordance with IANA or ITU-T Rec. X.660 | ISO/IEC/ITU 9834-1.
This extension may, at the option of the certificate issuer, be This extension may, at the option of the certificate issuer, be
either critical or non-critical. either critical or non-critical.
If the extension is flagged critical, then the certificate MUST be If the extension is flagged critical, then the certificate MUST only
used only for one of the purposes indicated. be used for one of the purposes indicated. If multiple purposes are
indicated the application need not recognize all purposes indicated,
as long as the intended purpose is present and recognized.
If the extension is flagged non-critical, then it indicates the If the extension is flagged non-critical, then it indicates the
intended purpose or purposes of the key, and may be used in finding intended purpose or purposes of the key, and may be used in finding
the correct key/certificate of an entity that has multiple the correct key/certificate of an entity that has multiple
keys/certificates. It is an advisory field and does not imply that keys/certificates. It is an advisory field and does not imply that
usage of the key is restricted by the certification authority to the usage of the key is restricted by the certification authority to the
purpose indicated. Certificate using applications may nevertheless purpose indicated. Certificate using applications may nevertheless
require that a particular purpose be indicated in order for the cer- require that a particular purpose be indicated in order for the
tificate to be acceptable to that application. certificate to be acceptable to that application.
If a certificate contains both a critical key usage field and a crit- If a certificate contains both a critical key usage field and a
ical extended key usage field, then both fields MUST be processed critical extended key usage field, then both fields MUST be processed
independently and the certificate MUST only be used for a purpose independently and the certificate MUST only be used for a purpose
consistent with both fields. If there is no purpose consistent with consistent with both fields. If there is no purpose consistent with
both fields, then the certificate MUST NOT be used for any purpose. both fields, then the certificate MUST NOT be used for any purpose.
The following key usage purposes are defined by this profile: The following key usage purposes are defined by this profile:
id-kp OBJECT IDENTIFIER ::= { id-pkix 3 } id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
id-kp-serverAuth OBJECT IDENTIFIER ::= {id-kp 1} id-kp-serverAuth OBJECT IDENTIFIER ::= {id-kp 1}
-- TLS Web server authentication -- TLS Web server authentication
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-- source. Key usage bits that may be consistent: digitalSignature, -- source. Key usage bits that may be consistent: digitalSignature,
-- nonRepudiation -- nonRepudiation
4.2.1.14 CRL Distribution Points 4.2.1.14 CRL Distribution Points
The CRL distribution points extension identifies how CRL information The CRL distribution points extension identifies how CRL information
is obtained. The extension SHOULD be non-critical, but this profile is obtained. The extension SHOULD be non-critical, but this profile
recommends support for this extension by CAs and applications. recommends support for this extension by CAs and applications.
Further discussion of CRL management is contained in section 5. Further discussion of CRL management is contained in section 5.
The cRLDistributionPoints extension is a SEQUENCE of Distribution- The cRLDistributionPoints extension is a SEQUENCE of
Point. A DistributionPoint consists of three fields, each of which DistributionPoint. A DistributionPoint consists of three fields,
is optional: the name of the DistributionPoint, ReasonsFlags, and the each of which is optional: the name of the DistributionPoint,
cRLIssuer. While each component is optional, a DistributionPoint ReasonsFlags, and the cRLIssuer. While each component is optional, a
MUST NOT consist of only the ReasonsFlags field. If the distribution- DistributionPoint MUST NOT consist of only the ReasonsFlags field. If
Point omits cRLIssuer, the CRL MUST be issued by the CA that issued the distributionPoint omits cRLIssuer, the CRL MUST be issued by the
the certificate. If the distributionPointName is absent, cRLIssuer CA that issued the certificate. If the distributionPointName is
MUST be present and include a Name corresponding to an X.500 or LDAP absent, cRLIssuer MUST be present and include a Name corresponding to
directory entry where the CRL is located. an X.500 or LDAP directory entry where the CRL is located.
If the cRLDistributionPoints extension contains a Distribution- If the cRLDistributionPoints extension contains a
PointName of type URI, the following semantics MUST be assumed: the DistributionPointName of type URI, the following semantics MUST be
URI is a pointer to the current CRL for the associated reasons and assumed: the URI is a pointer to the current CRL for the associated
will be issued by the associated cRLIssuer. The expected values for reasons and will be issued by the associated cRLIssuer. The expected
the URI are those defined in 4.2.1.7. Processing rules for other values for the URI are those defined in 4.2.1.7. Processing rules for
values are not defined by this specification. If the distribution- other values are not defined by this specification. If the
Point omits reasons, the CRL MUST include revocations for all rea- distributionPoint omits reasons, the CRL MUST include revocations for
sons. all reasons.
id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= { id-ce 31 } id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= { id-ce 31 }
CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint
DistributionPoint ::= SEQUENCE { DistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL, distributionPoint [0] DistributionPointName OPTIONAL,
reasons [1] ReasonFlags OPTIONAL, reasons [1] ReasonFlags OPTIONAL,
cRLIssuer [2] GeneralNames OPTIONAL } cRLIssuer [2] GeneralNames OPTIONAL }
DistributionPointName ::= CHOICE { DistributionPointName ::= CHOICE {
fullName [0] GeneralNames, fullName [0] GeneralNames,
nameRelativeToCRLIssuer [1] RelativeDistinguishedName } nameRelativeToCRLIssuer [1] RelativeDistinguishedName }
skipping to change at page 42, line 47 skipping to change at page 43, line 32
certificateHold (6) } certificateHold (6) }
4.2.1.15 Inhibit Any-Policy 4.2.1.15 Inhibit Any-Policy
The inhibit any-policy extension can be used in certificates issued The inhibit any-policy extension can be used in certificates issued
to CAs. The inhibit any-policy indicates that the special any-policy to CAs. The inhibit any-policy indicates that the special any-policy
OID, with the value {2 5 29 32 0}, is not considered an explicit OID, with the value {2 5 29 32 0}, is not considered an explicit
match for other certificate policies. The value indicates the number match for other certificate policies. The value indicates the number
of additional certificates that may appear in the path before any- of additional certificates that may appear in the path before any-
policy is no longer permitted. For example, a value of one indicates policy is no longer permitted. For example, a value of one indicates
that any-policy may be processed in certificates issued by the sub- that any-policy may be processed in certificates issued by the
ject of this certificate, but not in additional certificates in the subject of this certificate, but not in additional certificates in
path. the path.
This extension MUST be critical. This extension MUST be critical.
id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= { id-ce 54 } id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= { id-ce 54 }
InhibitAnyPolicy ::= SkipCerts InhibitAnyPolicy ::= SkipCerts
SkipCerts ::= INTEGER (0..MAX) SkipCerts ::= INTEGER (0..MAX)
4.2.1.16 Freshest CRL (a.k.a. Delta CRL Distribution Point) 4.2.1.16 Freshest CRL (a.k.a. Delta CRL Distribution Point)
The freshest CRL extension identifies how delta-CRL information is The freshest CRL extension identifies how delta-CRL information is
obtained. The extension MUST be non-critical. Further discussion of obtained. The extension MUST be non-critical. Further discussion of
CRL management is contained in section 5. CRL management is contained in section 5.
The same syntax is used for this extension and the cRLDistribution- The same syntax is used for this extension and the
Points extension, and is described in section 4.2.1.14. The same cRLDistributionPoints extension, and is described in section
conventions apply to both extensions. 4.2.1.14. The same conventions apply to both extensions.
id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 } id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 }
FreshestCRL ::= CRLDistributionPoints FreshestCRL ::= CRLDistributionPoints
4.2.2 Private Internet Extensions 4.2.2 Private Internet Extensions
This section defines one new extension for use in the Internet Public This section defines one new extension for use in the Internet Public
Key Infrastructure. This extension may be used to direct applica- Key Infrastructure. This extension may be used to direct
tions to identify an on-line validation service supporting the issu- applications to identify an on-line validation service supporting the
ing CA. As the information may be available in multiple forms, each issuing CA. As the information may be available in multiple forms,
extension is a sequence of IA5String values, each of which represents each extension is a sequence of IA5String values, each of which
a URI. The URI implicitly specifies the location and format of the represents a URI. The URI implicitly specifies the location and
information and the method for obtaining the information. format of the information and the method for obtaining the
information.
An object identifier is defined for the private extension. The An object identifier is defined for the private extension. The
object identifier associated with the private extension is defined object identifier associated with the private extension is defined
under the arc id-pe within the id-pkix name space. Any future exten- under the arc id-pe within the id-pkix name space. Any future
sions defined for the Internet PKI will also be defined under the arc extensions defined for the Internet PKI will also be defined under
id-pe. the arc id-pe.
id-pkix OBJECT IDENTIFIER ::= id-pkix OBJECT IDENTIFIER ::=
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) } security(5) mechanisms(5) pkix(7) }
id-pe OBJECT IDENTIFIER ::= { id-pkix 1 } id-pe OBJECT IDENTIFIER ::= { id-pkix 1 }
4.2.2.1 Authority Information Access 4.2.2.1 Authority Information Access
The authority information access extension indicates how to access CA The authority information access extension indicates how to access CA
skipping to change at page 44, line 38 skipping to change at page 45, line 25
by accessLocation. by accessLocation.
This profile defines one OID for accessMethod. The id-ad-caIssuers This profile defines one OID for accessMethod. The id-ad-caIssuers
OID is used when the additional information lists CAs that have OID is used when the additional information lists CAs that have
issued certificates superior to the CA that issued the certificate issued certificates superior to the CA that issued the certificate
containing this extension. The referenced CA Issuers description is containing this extension. The referenced CA Issuers description is
intended to aid certificate users in the selection of a certification intended to aid certificate users in the selection of a certification
path that terminates at a point trusted by the certificate user. path that terminates at a point trusted by the certificate user.
When id-ad-caIssuers appears as accessInfoType, the accessLocation When id-ad-caIssuers appears as accessInfoType, the accessLocation
field describes the referenced description server and the access pro- field describes the referenced description server and the access
tocol to obtain the referenced description. The accessLocation field protocol to obtain the referenced description. The accessLocation
is defined as a GeneralName, which can take several forms. Where the field is defined as a GeneralName, which can take several forms.
information is available via http, ftp, or ldap, accessLocation MUST Where the information is available via http, ftp, or ldap,
be a uniformResourceIdentifier. Where the information is available accessLocation MUST be a uniformResourceIdentifier. Where the
via the directory access protocol (dap), accessLocation MUST be a information is available via the directory access protocol (dap),
directoryName. When the information is available via electronic mail, accessLocation MUST be a directoryName. When the information is
accessLocation MUST be an rfc822Name. The semantics of other name available via electronic mail, accessLocation MUST be an rfc822Name.
forms of accessLocation (when accessMethod is id-ad-caIssuers) are The semantics of other name forms of accessLocation (when
not defined by this specification. The information accessMethod is id-ad-caIssuers) are not defined by this
specification.
[RFC 2560] defines the access descriptor for the Online Certificate [RFC 2560] defines the access descriptor for the Online Certificate
Status Protocol. Additional access descriptors may be defined in Status Protocol. When this access descriptor appears in the
authority information access extension, this indicates the issuer
provides revocation information for this certificate through the
named OCSP service. Additional access descriptors may be defined in
other PKIX specifications. other PKIX specifications.
4.2.2.2 Subject Information Access
The subject information access extension indicates how to access
information and services for the subject of the certificate in which
the extension appears. When the subject is a CA, information and
services may include certificate validation services and CA policy
data. When the subject is an end entity, the information describes
the type of services offered and how to access them. In this case,
the contents of this extension are defined in the protocol
specifications for the suported services. This extension may be
included in subject or CA certificates, and it MUST be non-critical.
id-pe-subjectInfoAccess OBJECT IDENTIFIER ::= { id-pe 11 }
SubjectInfoAccessSyntax ::=
SEQUENCE SIZE (1..MAX) OF AccessDescription
AccessDescription ::= SEQUENCE {
accessMethod OBJECT IDENTIFIER,
accessLocation GeneralName }
Each entry in the sequence SubjectInfoAccessSyntax describes the
format and location of additional information provided by the subject
of the certificate in which this extension appears. The type and
format of the information is specified by the accessMethod field; the
accessLocation field specifies the location of the information. The
retrieval mechanism may be implied by the accessMethod or specified
by accessLocation.
This profile defines one accessMethod to be used when the subject is
a CA, and one access mehod to be used when the subject is an end
entity. Additional access methods may be defined in the future in
the protocol specifications for other services.
The id-ad-caRepository OID is used when the subject is a CA, and
publishes its certificates and CRLs (if issued) in a repository. The
accessLocation field is defined as a GeneralName, which can take
several forms. Where the information is available via http, ftp, or
ldap, accessLocation MUST be a uniformResourceIdentifier. Where the
information is available via the directory access protocol (dap),
accessLocation MUST be a directoryName. When the information is
available via electronic mail, accessLocation MUST be an rfc822Name.
The semantics of other name forms of of accessLocation (when
accessMethod is id-ad-caRepository) are not defined by this
specification.
The id-ad-timeStamping OID is used when the subject offers
timestamping services using the Time STamp Protocol defined in [PKIX
TSA]. Where the timestamping services are available via http or ftp,
accessLocation MUST be a uniformResourceIdentifier. Where the
timestamping services are available via electronic mail,
accessLocation MUST be an rfc822Name. Where timestamping services
are available using TCP/IP, the dNSName and ipAddress name forms may
be used. The semantics of other name forms of accessLocation (when
accessMethod is id-ad-timeStamping) are not defined by this
specification.
Additional access descriptors may be defined in other PKIX
specifications.
id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }
id-ad-caRepository OBJECT IDENTIFIER ::= { id-ad 5 }
id-ad-timeStamping OBJECT IDENTIFIER ::= { id-ad 3 }
5 CRL and CRL Extensions Profile 5 CRL and CRL Extensions Profile
As described above, one goal of this X.509 v2 CRL profile is to As described above, one goal of this X.509 v2 CRL profile is to
foster the creation of an interoperable and reusable Internet PKI. foster the creation of an interoperable and reusable Internet PKI.
To achieve this goal, guidelines for the use of extensions are speci- To achieve this goal, guidelines for the use of extensions are
fied, and some assumptions are made about the nature of information specified, and some assumptions are made about the nature of
included in the CRL. information included in the CRL.
CRLs may be used in a wide range of applications and environments CRLs may be used in a wide range of applications and environments
covering a broad spectrum of interoperability goals and an even covering a broad spectrum of interoperability goals and an even
broader spectrum of operational and assurance requirements. This broader spectrum of operational and assurance requirements. This
profile establishes a common baseline for generic applications profile establishes a common baseline for generic applications
requiring broad interoperability. The profile defines a baseline set requiring broad interoperability. The profile defines a baseline set
of information that can be expected in every CRL. Also, the profile of information that can be expected in every CRL. Also, the profile
defines common locations within the CRL for frequently used attri- defines common locations within the CRL for frequently used
butes as well as common representations for these attributes. attributes as well as common representations for these attributes.
This profile does not define any private Internet CRL extensions or This profile does not define any private Internet CRL extensions or
CRL entry extensions. CRL entry extensions.
Environments with additional or special purpose requirements may Environments with additional or special purpose requirements may
build on this profile or may replace it. build on this profile or may replace it.
Conforming CAs are not required to issue CRLs if other revocation or Conforming CAs are not required to issue CRLs if other revocation or
certificate status mechanisms are provided. Conforming CAs that certificate status mechanisms are provided. Conforming CAs that
issue CRLs MUST issue version 2 CRLs, and CAs MUST include the date issue CRLs MUST issue version 2 CRLs, and CAs MUST include the date
by which the next CRL will be issued in the nextUpdate field (see by which the next CRL will be issued in the nextUpdate field (see
sec. 5.1.2.5), the CRL number extension (see sec. 5.2.3) and the sec. 5.1.2.5), the CRL number extension (see sec. 5.2.3) and the
authority key identifier extension (see sec. 5.2.1). Conforming authority key identifier extension (see sec. 5.2.1). Conforming
applications are required to process version 1 and 2 CRLs. applications are required to process version 1 and 2 CRLs.
5.1 CRL Fields 5.1 CRL Fields
The X.509 v2 CRL syntax is as follows. For signature calculation, The X.509 v2 CRL syntax is as follows. For signature calculation,
the data that is to be signed is ASN.1 DER encoded. ASN.1 DER encod- the data that is to be signed is ASN.1 DER encoded. ASN.1 DER
ing is a tag, length, value encoding system for each element. encoding is a tag, length, value encoding system for each element.
CertificateList ::= SEQUENCE { CertificateList ::= SEQUENCE {
tbsCertList TBSCertList, tbsCertList TBSCertList,
signatureAlgorithm AlgorithmIdentifier, signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING } signatureValue BIT STRING }
TBSCertList ::= SEQUENCE { TBSCertList ::= SEQUENCE {
version Version OPTIONAL, version Version OPTIONAL,
-- if present, shall be v2 -- if present, shall be v2
signature AlgorithmIdentifier, signature AlgorithmIdentifier,
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5.1.1 CertificateList Fields 5.1.1 CertificateList Fields
The CertificateList is a SEQUENCE of three required fields. The The CertificateList is a SEQUENCE of three required fields. The
fields are described in detail in the following subsections. fields are described in detail in the following subsections.
5.1.1.1 tbsCertList 5.1.1.1 tbsCertList
The first field in the sequence is the tbsCertList. This field is The first field in the sequence is the tbsCertList. This field is
itself a sequence containing the name of the issuer, issue date, itself a sequence containing the name of the issuer, issue date,
issue date of the next list, the optional list of revoked certifi- issue date of the next list, the optional list of revoked
cates, and optional CRL extensions. When there are no revoked certi- certificates, and optional CRL extensions. When there are no revoked
ficates, the revoked certificates list is absent. When one or more certificates, the revoked certificates list is absent. When one or
certificates are revoked, each entry on the revoked certificate list more certificates are revoked, each entry on the revoked certificate
is defined by a sequence of user certificate serial number, revoca- list is defined by a sequence of user certificate serial number,
tion date, and optional CRL entry extensions. revocation date, and optional CRL entry extensions.
5.1.1.2 signatureAlgorithm 5.1.1.2 signatureAlgorithm
The signatureAlgorithm field contains the algorithm identifier for The signatureAlgorithm field contains the algorithm identifier for
the algorithm used by the CA to sign the CertificateList. The field the algorithm used by the CA to sign the CertificateList. The field
is of type AlgorithmIdentifier, which is defined in section 4.1.1.2. is of type AlgorithmIdentifier, which is defined in section 4.1.1.2.
[PKIX ALGS] lists the supported algorithms for this specification. [PKIX ALGS] lists the supported algorithms for this specification.
Conforming CAs MUST use the algorithm identifiers presented in [PKIX Conforming CAs MUST use the algorithm identifiers presented in [PKIX
ALGS] when signing with a supported signature algorithm. ALGS] when signing with a supported signature algorithm.
This field MUST contain the same algorithm identifier as the signa- This field MUST contain the same algorithm identifier as the
ture field in the sequence tbsCertList (see sec. 5.1.2.2). signature field in the sequence tbsCertList (see sec. 5.1.2.2).
5.1.1.3 signatureValue 5.1.1.3 signatureValue
The signatureValue field contains a digital signature computed upon The signatureValue field contains a digital signature computed upon
the ASN.1 DER encoded tbsCertList. The ASN.1 DER encoded tbsCertList the ASN.1 DER encoded tbsCertList. The ASN.1 DER encoded tbsCertList
is used as the input to the signature function. This signature value is used as the input to the signature function. This signature value
is then ASN.1 encoded as a BIT STRING and included in the CRL's sig- is then ASN.1 encoded as a BIT STRING and included in the CRL's
natureValue field. The details of this process are specified for each signatureValue field. The details of this process are specified for
of the supported algorithms in [PKIX ALGS]. each of the supported algorithms in [PKIX ALGS].
5.1.2 Certificate List "To Be Signed" 5.1.2 Certificate List "To Be Signed"
The certificate list to be signed, or TBSCertList, is a SEQUENCE of The certificate list to be signed, or TBSCertList, is a SEQUENCE of
required and optional fields. The required fields identify the CRL required and optional fields. The required fields identify the CRL
issuer, the algorithm used to sign the CRL, the date and time the CRL issuer, the algorithm used to sign the CRL, the date and time the CRL
was issued, and the date and time by which the CA will issue the next was issued, and the date and time by which the CA will issue the next
CRL. CRL.
Optional fields include lists of revoked certificates and CRL exten- Optional fields include lists of revoked certificates and CRL
sions. The revoked certificate list is optional to support the case extensions. The revoked certificate list is optional to support the
where a CA has not revoked any unexpired certificates that it has case where a CA has not revoked any unexpired certificates that it
issued. The profile requires conforming CAs to use the CRL extension has issued. The profile requires conforming CAs to use the CRL
cRLNumber in all CRLs issued. extension cRLNumber in all CRLs issued.
5.1.2.1 Version 5.1.2.1 Version
This optional field describes the version of the encoded CRL. When This optional field describes the version of the encoded CRL. When
extensions are used, as required by this profile, this field MUST be extensions are used, as required by this profile, this field MUST be
present and MUST specify version 2 (the integer value is 1). present and MUST specify version 2 (the integer value is 1).
5.1.2.2 Signature 5.1.2.2 Signature
This field contains the algorithm identifier for the algorithm used This field contains the algorithm identifier for the algorithm used
to sign the CRL. [PKIX ALGS] lists OIDs for the most popular signa- to sign the CRL. [PKIX ALGS] lists OIDs for the most popular
ture algorithms used in the Internet PKI. signature algorithms used in the Internet PKI.
This field MUST contain the same algorithm identifier as the signa- This field MUST contain the same algorithm identifier as the
tureAlgorithm field in the sequence CertificateList (see section signatureAlgorithm field in the sequence CertificateList (see section
5.1.1.2). 5.1.1.2).
5.1.2.3 Issuer Name 5.1.2.3 Issuer Name
The issuer name identifies the entity who has signed and issued the The issuer name identifies the entity who has signed and issued the
CRL. The issuer identity is carried in the issuer name field. Alter- CRL. The issuer identity is carried in the issuer name field.
native name forms may also appear in the issuerAltName extension (see Alternative name forms may also appear in the issuerAltName extension
sec. 5.2.2). The issuer name field MUST contain an X.500 dis- (see sec. 5.2.2). The issuer name field MUST contain an X.500
tinguished name (DN). The issuer name field is defined as the X.501 distinguished name (DN). The issuer name field is defined as the
type Name, and MUST follow the encoding rules for the issuer name X.501 type Name, and MUST follow the encoding rules for the issuer
field in the certificate (see sec. 4.1.2.4). name field in the certificate (see sec. 4.1.2.4).
5.1.2.4 This Update 5.1.2.4 This Update
This field indicates the issue date of this CRL. ThisUpdate may be This field indicates the issue date of this CRL. ThisUpdate may be
encoded as UTCTime or GeneralizedTime. encoded as UTCTime or GeneralizedTime.
CAs conforming to this profile that issue CRLs MUST encode thisUpdate CAs conforming to this profile that issue CRLs MUST encode thisUpdate
as UTCTime for dates through the year 2049. CAs conforming to this as UTCTime for dates through the year 2049. CAs conforming to this
profile that issue CRLs MUST encode thisUpdate as GeneralizedTime for profile that issue CRLs MUST encode thisUpdate as GeneralizedTime for
dates in the year 2050 or later. dates in the year 2050 or later.
Where encoded as UTCTime, thisUpdate MUST be specified and inter- Where encoded as UTCTime, thisUpdate MUST be specified and
preted as defined in section 4.1.2.5.1. Where encoded as General- interpreted as defined in section 4.1.2.5.1. Where encoded as
izedTime, thisUpdate MUST be specified and interpreted as defined in GeneralizedTime, thisUpdate MUST be specified and interpreted as
section 4.1.2.5.2. defined in section 4.1.2.5.2.
5.1.2.5 Next Update 5.1.2.5 Next Update
This field indicates the date by which the next CRL will be issued. This field indicates the date by which the next CRL will be issued.
The next CRL could be issued before the indicated date, but it will The next CRL could be issued before the indicated date, but it will
not be issued any later than the indicated date. CAs SHOULD issue not be issued any later than the indicated date. CAs SHOULD issue
CRLs with a nextUpdate time equal to or later than all previous CRLs. CRLs with a nextUpdate time equal to or later than all previous CRLs.
nextUpdate may be encoded as UTCTime or GeneralizedTime. nextUpdate may be encoded as UTCTime or GeneralizedTime.
This profile requires inclusion of nextUpdate in all CRLs issued by This profile requires inclusion of nextUpdate in all CRLs issued by
conforming CAs. Note that the ASN.1 syntax of TBSCertList describes conforming CAs. Note that the ASN.1 syntax of TBSCertList describes
this field as OPTIONAL, which is consistent with the ASN.1 structure this field as OPTIONAL, which is consistent with the ASN.1 structure
defined in [X.509]. The behavior of clients processing CRLs which defined in [X.509]. The behavior of clients processing CRLs which
omit nextUpdate is not specified by this profile. omit nextUpdate is not specified by this profile.
CAs conforming to this profile that issue CRLs MUST encode nextUpdate CAs conforming to this profile that issue CRLs MUST encode nextUpdate
as UTCTime for dates through the year 2049. CAs conforming to this as UTCTime for dates through the year 2049. CAs conforming to this
profile that issue CRLs MUST encode nextUpdate as GeneralizedTime for profile that issue CRLs MUST encode nextUpdate as GeneralizedTime for
dates in the year 2050 or later. dates in the year 2050 or later.
Where encoded as UTCTime, nextUpdate MUST be specified and inter- Where encoded as UTCTime, nextUpdate MUST be specified and
preted as defined in section 4.1.2.5.1. Where encoded as General- interpreted as defined in section 4.1.2.5.1. Where encoded as
izedTime, nextUpdate MUST be specified and interpreted as defined in GeneralizedTime, nextUpdate MUST be specified and interpreted as
section 4.1.2.5.2. defined in section 4.1.2.5.2.
5.1.2.6 Revoked Certificates 5.1.2.6 Revoked Certificates
When there are no revoked certificates, the revoked certificates list When there are no revoked certificates, the revoked certificates list
is absent. Otherwise, revoked certificates are listed by their is absent. Otherwise, revoked certificates are listed by their
serial numbers. Certificates revoked by the CA are uniquely identi- serial numbers. Certificates revoked by the CA are uniquely
fied by the certificate serial number. The date on which the revoca- identified by the certificate serial number. The date on which the
tion occurred is specified. The time for revocationDate MUST be revocation occurred is specified. The time for revocationDate MUST
expressed as described in section 5.1.2.4. Additional information may be expressed as described in section 5.1.2.4. Additional information
be supplied in CRL entry extensions; CRL entry extensions are may be supplied in CRL entry extensions; CRL entry extensions are
discussed in section 5.3. discussed in section 5.3.
5.1.2.7 Extensions 5.1.2.7 Extensions
This field may only appear if the version is 2 (see sec. 5.1.2.1). This field may only appear if the version is 2 (see sec. 5.1.2.1).
If present, this field is a SEQUENCE of one or more CRL extensions. If present, this field is a SEQUENCE of one or more CRL extensions.
CRL extensions are discussed in section 5.2. CRL extensions are discussed in section 5.2.
5.2 CRL Extensions 5.2 CRL Extensions
The extensions defined by ANSI X9 and ISO/IEC/ITU for X.509 v2 CRLs The extensions defined by ANSI X9 and ISO/IEC/ITU for X.509 v2 CRLs
[X.509] [X9.55] provide methods for associating additional attributes [X.509] [X9.55] provide methods for associating additional attributes
with CRLs. The X.509 v2 CRL format also allows communities to define with CRLs. The X.509 v2 CRL format also allows communities to define
private extensions to carry information unique to those communities. private extensions to carry information unique to those communities.
Each extension in a CRL may be designated as critical or non- Each extension in a CRL may be designated as critical or non-
critical. A CRL validation MUST fail if it encounters a critical critical. A CRL validation MUST fail if it encounters a critical
extension which it does not know how to process. However, an extension which it does not know how to process. However, an
unrecognized non-critical extension may be ignored. The following unrecognized non-critical extension may be ignored. The following
subsections present those extensions used within Internet CRLs. Com- subsections present those extensions used within Internet CRLs.
munities may elect to include extensions in CRLs which are not Communities may elect to include extensions in CRLs which are not
defined in this specification. However, caution should be exercised defined in this specification. However, caution should be exercised
in adopting any critical extensions in CRLs which might be used in a in adopting any critical extensions in CRLs which might be used in a
general context. general context.
Conforming CAs that issue CRLs are required to include the authority Conforming CAs that issue CRLs are required to include the authority
key identifier (see sec. 5.2.1) and the CRL number (see sec. 5.2.3) key identifier (see sec. 5.2.1) and the CRL number (see sec. 5.2.3)
extensions in all CRLs issued. extensions in all CRLs issued.
5.2.1 Authority Key Identifier 5.2.1 Authority Key Identifier
The authority key identifier extension provides a means of identify- The authority key identifier extension provides a means of
ing the public key corresponding to the private key used to sign a identifying the public key corresponding to the private key used to
CRL. The identification can be based on either the key identifier sign a CRL. The identification can be based on either the key
(the subject key identifier in the CRL signer's certificate) or on identifier (the subject key identifier in the CRL signer's
the issuer name and serial number. This extension is especially use- certificate) or on the issuer name and serial number. This extension
ful where an issuer has more than one signing key, either due to mul- is especially useful where an issuer has more than one signing key,
tiple concurrent key pairs or due to changeover. either due to multiple concurrent key pairs or due to changeover.
Conforming CAs MUST use the key identifier method, and MUST include Conforming CAs MUST use the key identifier method, and MUST include
this extension in all CRLs issued. this extension in all CRLs issued.
The syntax for this CRL extension is defined in section 4.2.1.1. The syntax for this CRL extension is defined in section 4.2.1.1.
5.2.2 Issuer Alternative Name 5.2.2 Issuer Alternative Name
The issuer alternative names extension allows additional identities The issuer alternative names extension allows additional identities
to be associated with the issuer of the CRL. Defined options include to be associated with the issuer of the CRL. Defined options include
an rfc822 name (electronic mail address), a DNS name, an IP address, an rfc822 name (electronic mail address), a DNS name, an IP address,
and a URI. Multiple instances of a name and multiple name forms may and a URI. Multiple instances of a name and multiple name forms may
be included. Whenever such identities are used, the issuer alterna- be included. Whenever such identities are used, the issuer
tive name extension MUST be used. alternative name extension MUST be used.
The issuerAltName extension SHOULD NOT be marked critical. The issuerAltName extension SHOULD NOT be marked critical.
The OID and syntax for this CRL extension are defined in section The OID and syntax for this CRL extension are defined in section
4.2.1.8. 4.2.1.8.
5.2.3 CRL Number 5.2.3 CRL Number
The CRL number is a non-critical CRL extension which conveys a mono- The CRL number is a non-critical CRL extension which conveys a
tonically increasing sequence number for each CRL issued by a CA. monotonically increasing sequence number for each CRL issued by a CA.
This extension allows users to easily determine when a particular CRL This extension allows users to easily determine when a particular CRL
supersedes another CRL. CAs conforming to this profile MUST include supersedes another CRL. CAs conforming to this profile MUST include
this extension in all CRLs. this extension in all CRLs.
id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 } id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 }
cRLNumber ::= INTEGER (0..MAX) cRLNumber ::= INTEGER (0..MAX)
5.2.4 Delta CRL Indicator 5.2.4 Delta CRL Indicator
The delta CRL indicator is a critical CRL extension that identifies a The delta CRL indicator is a critical CRL extension that identifies a
CRL as being a delta CRL. Delta CRLs contain updates to revocation CRL as being a delta CRL. Delta CRLs contain updates to revocation
information previously distributed, rather than all the information information previously distributed, rather than all the information
that would appear in a complete CRL. The use of delta CRLs can sig- that would appear in a complete CRL. The use of delta CRLs can
nificantly reduce network load and processing time in some environ- significantly reduce network load and processing time in some
ments. Delta CRLs are generally smaller than the CRLs they update, environments. Delta CRLs are generally smaller than the CRLs they
so applications that obtain delta CRLs consume less network bandwidth update, so applications that obtain delta CRLs consume less network
than applications that obtain the corresponding complete CRLs. bandwidth than applications that obtain the corresponding complete
Applications which store revocation information in a format other CRLs. Applications which store revocation information in a format
than the CRL structure can add new revocation information to the other than the CRL structure can add new revocation information to
local database without reprocessing information. the local database without reprocessing information.
The delta CRL indicator extension contains a single value of type The delta CRL indicator extension contains a single value of type
BaseCRLNumber. This value identifies the CRL number of the base CRL BaseCRLNumber. This value identifies the CRL number of the base CRL
that was used as the foundation in the generation of this delta CRL. that was used as the foundation in the generation of this delta CRL.
The referenced base CRL is a CRL that was explicitly issued as a CRL The referenced base CRL is a CRL that was explicitly issued as a CRL
that is complete for a given scope (e.g., a set of revocation reasons that is complete for a given scope (e.g., a set of revocation reasons
or a particular distribution point.) The CRL containing the delta CRL or a particular distribution point.) The CRL containing the delta CRL
indicator extension contains all updates to the certificate revoca- indicator extension contains all updates to the certificate
tion status for that same scope. The combination of a CRL containing revocation status for that same scope. The combination of a CRL
the delta CRL indicator extension plus the CRL referenced in the containing the delta CRL indicator extension plus the CRL referenced
BaseCRLNumber component of this extension is equivalent to a full in the BaseCRLNumber component of this extension is equivalent to a
CRL, for the applicable scope, at the time of publication of the full CRL, for the applicable scope, at the time of publication of the
delta CRL. delta CRL.
When a conforming CA issues a delta CRL, the CA MUST also issue a CRL When a conforming CA issues a delta CRL, the CA MUST also issue a CRL
that is complete for the given scope. Both the delta CRL and the that is complete for the given scope. Both the delta CRL and the
complete CRL MUST include the CRL number extension (see sec. 5.2.3). complete CRL MUST include the CRL number extension (see sec. 5.2.3).
The CRL number extension in the delta CRL and the complete CRL MUST The CRL number extension in the delta CRL and the complete CRL MUST
contain the same value. When a delta CRL is issued, it MUST cover contain the same value. When a delta CRL is issued, it MUST cover
the same set of reasons and same set of certificates that were the same set of reasons and same set of certificates that were
covered by the base CRL it references. covered by the base CRL it references.
An application can construct a CRL that is complete for a given An application can construct a CRL that is complete for a given
scope, at the current time, in either of the following ways: scope, at the current time, in either of the following ways:
(a) by retrieving the current delta CRL for that scope, and com-
bining it with an issued CRL that is complete for that scope and (a) by retrieving the current delta CRL for that scope, and
that has a cRLNumber greater than or equal to the cRLNumber of the combining it with an issued CRL that is complete for that scope
base CRL referenced in the delta CRL; or and that has a cRLNumber greater than or equal to the cRLNumber of
(b) by retrieving the current delta CRL for that scope and combin- the base CRL referenced in the delta CRL; or
ing it with a locally constructed CRL whose cRLNumber is greater
than or equal to the cRLNumber of the base CRL referenced in the (b) by retrieving the current delta CRL for that scope and
current delta CRL. combining it with a locally constructed CRL whose cRLNumber is
greater than or equal to the cRLNumber of the base CRL referenced
in the current delta CRL.
The constructed CRL has the CRL number specified in the CRL number The constructed CRL has the CRL number specified in the CRL number
extension found in the delta CRL used in its construction. extension found in the delta CRL used in its construction.
CAs must ensure that application of a delta CRL to the referenced CAs must ensure that application of a delta CRL to the referenced
base revocation information accurately reflects the current status of base revocation information accurately reflects the current status of
revocation. If a CA supports the certificateHold revocation reason revocation. If a CA supports the certificateHold revocation reason
the following rules must be applied when generating delta CRLs: the following rules must be applied when generating delta CRLs:
(a) If a certificate was listed as revoked with revocation reason (a) If a certificate was listed as revoked with revocation reason
certificateHold on a CRL (either a delta CRL or a CRL that is com- certificateHold on a CRL (either a delta CRL or a CRL that is
plete for a given scope), whose cRLNumber is n, and the hold is complete for a given scope), whose cRLNumber is n, and the hold is
subsequently released, the certificate must be included in all subsequently released, the certificate must be included in all
delta CRLs issued after the hold is released where the cRLNumber delta CRLs issued after the hold is released where the cRLNumber
of the referenced base CRL is less than or equal to n. The certi- of the referenced base CRL is less than or equal to n. The
ficate must be listed with revocation reason removeFromCRL unless certificate must be listed with revocation reason removeFromCRL
the certificate is subsequently revoked again for one of the revo- unless the certificate is subsequently revoked again for one of
cation reasons covered by the delta CRL, in which case the certi- the revocation reasons covered by the delta CRL, in which case the
ficate must be listed with the revocation reason appropriate for certificate must be listed with the revocation reason appropriate
the subsequent revocation. for the subsequent revocation.
(b) If the certificate was not removed from hold, but was per- (b) If the certificate was not removed from hold, but was
manently revoked, then it must be listed on all subsequent delta permanently revoked, then it must be listed on all subsequent
CRLs where the cRLNumber of the referenced base CRL is less than delta CRLs where the cRLNumber of the referenced base CRL is less
the cRLNumber of the CRL (either a delta CRL or a CRL that is com- than the cRLNumber of the CRL (either a delta CRL or a CRL that is
plete for the given scope) on which the permanent revocation complete for the given scope) on which the permanent revocation
notice first appeared. notice first appeared.
id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 } id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 }
deltaCRLIndicator EXTENSION ::= { deltaCRLIndicator EXTENSION ::= {
SYNTAX BaseCRLNumber SYNTAX BaseCRLNumber
IDENTIFIED BY id-ce-deltaCRLIndicator } IDENTIFIED BY id-ce-deltaCRLIndicator }
BaseCRLNumber ::= CRLNumber BaseCRLNumber ::= CRLNumber
5.2.5 Issuing Distribution Point 5.2.5 Issuing Distribution Point
The issuing distribution point is a critical CRL extension that iden- The issuing distribution point is a critical CRL extension that
tifies the CRL distribution point for a particular CRL, and it indi- identifies the CRL distribution point for a particular CRL, and it
cates whether the CRL covers revocation for end entity certificates indicates whether the CRL covers revocation for end entity
only, CA certificates only, or a limited set of reason codes. certificates only, CA certificates only, or a limited set of reason
Although the extension is critical, conforming implementations are codes. Although the extension is critical, conforming
not required to support this extension. implementations are not required to support this extension.
The CRL is signed using the CA's private key. CRL Distribution The CRL is signed using the CA's private key. CRL Distribution
Points do not have their own key pairs. If the CRL is stored in the Points do not have their own key pairs. If the CRL is stored in the
X.500 Directory, it is stored in the Directory entry corresponding to X.500 Directory, it is stored in the Directory entry corresponding to
the CRL distribution point, which may be different than the Directory the CRL distribution point, which may be different than the Directory
entry of the CA. entry of the CA.
The reason codes associated with a distribution point shall be speci- The reason codes associated with a distribution point shall be
fied in onlySomeReasons. If onlySomeReasons does not appear, the dis- specified in onlySomeReasons. If onlySomeReasons does not appear, the
tribution point shall contain revocations for all reason codes. CAs distribution point shall contain revocations for all reason codes.
may use CRL distribution points to partition the CRL on the basis of CAs may use CRL distribution points to partition the CRL on the basis
compromise and routine revocation. In this case, the revocations of compromise and routine revocation. In this case, the revocations
with reason code keyCompromise (1) and cACompromise (2) appear in one with reason code keyCompromise (1) and cACompromise (2) appear in one
distribution point, and the revocations with other reason codes distribution point, and the revocations with other reason codes
appear in another distribution point. appear in another distribution point.
Where the issuingDistributionPoint extension contains a URL, the fol- Where the issuingDistributionPoint extension contains a URL, the
lowing semantics MUST be assumed: the object is a pointer to the most following semantics MUST be assumed: the object is a pointer to the
current CRL issued by this CA. The URI schemes ftp, http, mailto most current CRL issued by this CA. The URI schemes ftp, http,
[RFC1738] and ldap [RFC1778] are defined for this purpose. The URI mailto [RFC1738] and ldap [RFC1778] are defined for this purpose.
MUST be an absolute, not relative, pathname and MUST specify the The URI MUST be an absolute, not relative, pathname and MUST specify
host. the host.
id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 } id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 }
issuingDistributionPoint ::= SEQUENCE { issuingDistributionPoint ::= SEQUENCE {
distributionPoint [0] DistributionPointName OPTIONAL, distributionPoint [0] DistributionPointName OPTIONAL,
onlyContainsUserCerts [1] BOOLEAN DEFAULT FALSE, onlyContainsUserCerts [1] BOOLEAN DEFAULT FALSE,
onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE, onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE,
onlySomeReasons [3] ReasonFlags OPTIONAL, onlySomeReasons [3] ReasonFlags OPTIONAL,
indirectCRL [4] BOOLEAN DEFAULT FALSE } indirectCRL [4] BOOLEAN DEFAULT FALSE }
5.2.6 Freshest CRL (a.k.a. Delta CRL Distribution Point) 5.2.6 Freshest CRL (a.k.a. Delta CRL Distribution Point)
The freshest CRL extension identifies how delta-CRL information for The freshest CRL extension identifies how delta-CRL information for
this CRL is obtained. The extension MUST be non-critical. this CRL is obtained. The extension MUST be non-critical.
The same syntax is used for this extension as the cRLDistribution- The same syntax is used for this extension as the
Points certificate extension, and is described in section 4.2.1.14. cRLDistributionPoints certificate extension, and is described in
The same conventions apply to both extensions. section 4.2.1.14. The same conventions apply to both extensions.
id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 } id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 }
FreshestCRL ::= CRLDistributionPoints FreshestCRL ::= CRLDistributionPoints
5.3 CRL Entry Extensions 5.3 CRL Entry Extensions
The CRL entry extensions already defined by ANSI X9 and ISO/IEC/ITU The CRL entry extensions already defined by ANSI X9 and ISO/IEC/ITU
for X.509 v2 CRLs provide methods for associating additional attri- for X.509 v2 CRLs provide methods for associating additional
butes with CRL entries [X.509] [X9.55]. The X.509 v2 CRL format also attributes with CRL entries [X.509] [X9.55]. The X.509 v2 CRL format
allows communities to define private CRL entry extensions to carry also allows communities to define private CRL entry extensions to
information unique to those communities. Each extension in a CRL carry information unique to those communities. Each extension in a
entry may be designated as critical or non-critical. A CRL valida- CRL entry may be designated as critical or non-critical. A CRL
tion MUST fail if it encounters a critical CRL entry extension which validation MUST fail if it encounters a critical CRL entry extension
it does not know how to process. However, an unrecognized non- which it does not know how to process. However, an unrecognized
critical CRL entry extension may be ignored. The following subsec- non-critical CRL entry extension may be ignored. The following
tions present recommended extensions used within Internet CRL entries subsections present recommended extensions used within Internet CRL
and standard locations for information. Communities may elect to use entries and standard locations for information. Communities may
additional CRL entry extensions; however, caution should be exercised elect to use additional CRL entry extensions; however, caution should
in adopting any critical extensions in CRL entries which might be be exercised in adopting any critical extensions in CRL entries which
used in a general context. might be used in a general context.
All CRL entry extensions used in this specification are non-critical. All CRL entry extensions used in this specification are non-critical.
Support for these extensions is optional for conforming CAs and Support for these extensions is optional for conforming CAs and
applications. However, CAs that issue CRLs SHOULD include reason applications. However, CAs that issue CRLs SHOULD include reason
codes (see sec. 5.3.1) and invalidity dates (see sec. 5.3.3) whenever codes (see sec. 5.3.1) and invalidity dates (see sec. 5.3.3) whenever
this information is available. this information is available.
5.3.1 Reason Code 5.3.1 Reason Code
The reasonCode is a non-critical CRL entry extension that identifies The reasonCode is a non-critical CRL entry extension that identifies
the reason for the certificate revocation. CAs are strongly the reason for the certificate revocation. CAs are strongly
encouraged to include meaningful reason codes in CRL entries; how- encouraged to include meaningful reason codes in CRL entries;
ever, the reason code CRL entry extension SHOULD be absent instead of however, the reason code CRL entry extension SHOULD be absent instead
using the unspecified (0) reasonCode value. of using the unspecified (0) reasonCode value.
id-ce-cRLReason OBJECT IDENTIFIER ::= { id-ce 21 } id-ce-cRLReason OBJECT IDENTIFIER ::= { id-ce 21 }
-- reasonCode ::= { CRLReason } -- reasonCode ::= { CRLReason }
CRLReason ::= ENUMERATED { CRLReason ::= ENUMERATED {
unspecified (0), unspecified (0),
keyCompromise (1), keyCompromise (1),
cACompromise (2), cACompromise (2),
affiliationChanged (3), affiliationChanged (3),
superseded (4), superseded (4),
cessationOfOperation (5), cessationOfOperation (5),
certificateHold (6), certificateHold (6),
removeFromCRL (8) } removeFromCRL (8) }
skipping to change at page 54, line 25 skipping to change at page 56, line 38
The hold instruction code is a non-critical CRL entry extension that The hold instruction code is a non-critical CRL entry extension that
provides a registered instruction identifier which indicates the provides a registered instruction identifier which indicates the
action to be taken after encountering a certificate that has been action to be taken after encountering a certificate that has been
placed on hold. placed on hold.
id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 } id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 }
holdInstructionCode ::= OBJECT IDENTIFIER holdInstructionCode ::= OBJECT IDENTIFIER
The following instruction codes have been defined. Conforming appli- The following instruction codes have been defined. Conforming
cations that process this extension MUST recognize the following applications that process this extension MUST recognize the following
instruction codes. instruction codes.
holdInstruction OBJECT IDENTIFIER ::= holdInstruction OBJECT IDENTIFIER ::=
{ iso(1) member-body(2) us(840) x9-57(10040) 2 } { iso(1) member-body(2) us(840) x9-57(10040) 2 }
id-holdinstruction-none OBJECT IDENTIFIER ::= {holdInstruction 1} id-holdinstruction-none OBJECT IDENTIFIER ::= {holdInstruction 1}
id-holdinstruction-callissuer id-holdinstruction-callissuer
OBJECT IDENTIFIER ::= {holdInstruction 2} OBJECT IDENTIFIER ::= {holdInstruction 2}
id-holdinstruction-reject OBJECT IDENTIFIER ::= {holdInstruction 3} id-holdinstruction-reject OBJECT IDENTIFIER ::= {holdInstruction 3}
Conforming applications which encounter an id-holdinstruction- Conforming applications which encounter an id-holdinstruction-
callissuer MUST call the certificate issuer or reject the certifi- callissuer MUST call the certificate issuer or reject the
cate. Conforming applications which encounter an id- certificate. Conforming applications which encounter an id-
holdinstruction-reject MUST reject the certificate. The hold instruc- holdinstruction-reject MUST reject the certificate. The hold
tion id-holdinstruction-none is semantically equivalent to the instruction id-holdinstruction-none is semantically equivalent to the
absence of a holdInstructionCode, and its use is strongly deprecated absence of a holdInstructionCode, and its use is strongly deprecated
for the Internet PKI. for the Internet PKI.
5.3.3 Invalidity Date 5.3.3 Invalidity Date
The invalidity date is a non-critical CRL entry extension that pro- The invalidity date is a non-critical CRL entry extension that
vides the date on which it is known or suspected that the private key provides the date on which it is known or suspected that the private
was compromised or that the certificate otherwise became invalid. key was compromised or that the certificate otherwise became invalid.
This date may be earlier than the revocation date in the CRL entry, This date may be earlier than the revocation date in the CRL entry,
which is the date at which the CA processed the revocation. When a which is the date at which the CA processed the revocation. When a
revocation is first posted by a CA in a CRL, the invalidity date may revocation is first posted by a CA in a CRL, the invalidity date may
precede the date of issue of earlier CRLs, but the revocation date precede the date of issue of earlier CRLs, but the revocation date
SHOULD NOT precede the date of issue of earlier CRLs. Whenever this SHOULD NOT precede the date of issue of earlier CRLs. Whenever this
information is available, CAs are strongly encouraged to share it information is available, CAs are strongly encouraged to share it
with CRL users. with CRL users.
The GeneralizedTime values included in this field MUST be expressed The GeneralizedTime values included in this field MUST be expressed
in Greenwich Mean Time (Zulu), and MUST be specified and interpreted in Greenwich Mean Time (Zulu), and MUST be specified and interpreted
skipping to change at page 55, line 33 skipping to change at page 57, line 45
extension is not present on the first entry in an indirect CRL, the extension is not present on the first entry in an indirect CRL, the
certificate issuer defaults to the CRL issuer. On subsequent entries certificate issuer defaults to the CRL issuer. On subsequent entries
in an indirect CRL, if this extension is not present, the certificate in an indirect CRL, if this extension is not present, the certificate
issuer for the entry is the same as that for the preceding entry. issuer for the entry is the same as that for the preceding entry.
This field is defined as follows: This field is defined as follows:
id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 } id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 }
certificateIssuer ::= GeneralNames certificateIssuer ::= GeneralNames
If used by conforming CAs that issue CRLs, this extension is always If used by conforming CAs that issue CRLs, this extension MUST always
critical. If an implementation ignored this extension it could not be critical. If an implementation ignored this extension it could
correctly attribute CRL entries to certificates. This specification not correctly attribute CRL entries to certificates. This
RECOMMENDS that implementations recognize this extension. specification RECOMMENDS that implementations recognize this
extension.
6 Certification Path Validation 6 Certification Path Validation
Certification path validation procedures for the Internet PKI are Certification path validation procedures for the Internet PKI are
based on section 12.4.3 of [X.509]. Certification path processing based on the algorithm supplied in [X.509]. Certification path
verifies the binding between the subject distinguished name and/or processing verifies the binding between the subject distinguished
subject alternative name and subject public key. The binding is lim- name and/or subject alternative name and subject public key. The
ited by constraints which are specified in the certificates which binding is limited by constraints which are specified in the
comprise the path. The basic constraints and policy constraints certificates which comprise the path and the initial state variables
extensions allow the certification path processing logic to automate which are specified by the relying party. The basic constraints and
the decision making process. policy constraints extensions allow the certification path processing
logic to automate the decision making process.
This section describes an algorithm for validating certification This section describes an algorithm for validating certification
paths. Conforming implementations of this specification are not paths. Conforming implementations of this specification are not
required to implement this algorithm, but MUST be functionally required to implement this algorithm, but MUST provide functionality
equivalent to the external behavior resulting from this procedure. equivalent to the external behavior resulting from this procedure.
Any algorithm may be used by a particular implementation so long as Any algorithm may be used by a particular implementation so long as
it derives the correct result. it derives the correct result.
In section 6.1, the text describes basic path validation. This text In section 6.1, the text describes basic path validation. Valid paths
assumes that all valid paths begin with certificates issued by a sin- begin with certificates issued by a "most-trusted CA". The algorithm
gle "most-trusted CA". The algorithm requires the public key of the requires the public key of the CA, the CA's name, and any constraints
CA, the CA's name, the validity period of the public key, and any upon the set of paths which may be validated using this key.
constraints upon the set of paths which may be validated using this
key.
The "most-trusted CA" is a matter of policy: it could be a root CA in The selection of a "most-trusted CA" is a matter of policy: it could
a hierarchical PKI; the CA that issued the verifier's own be the top CA in a hierarchical PKI; the CA that issued the
certificate(s); or any other CA in a network PKI. The path valida- verifier's own certificate(s); or any other CA in a network PKI. The
tion procedure is the same regardless of the choice of "most-trusted path validation procedure is the same regardless of the choice of
CA." "most-trusted CA." In addition, different applications may rely on
different "most-trusted CA", or may accept paths that begin with any
of a set of "most-trusted CAs."
section 6.2 describes extensions to the basic path validation algo- Section 6.2 describes methods for using the path validation algorithm
rithm. Two specific cases are discussed: the case where paths may in specific implementations. Two specific cases are discussed: the
begin with one of several trusted CAs; and where compatibility with case where paths may begin with one of several trusted CAs; and where
the PEM architecture is required. compatibility with the PEM architecture is required.
Section 6.3 describes the steps necessary to determine if a
certificate is revoked or on hold status when CRLs are the revocation
mechanism used by the certificate issuer.
6.1 Basic Path Validation 6.1 Basic Path Validation
This text describes an algorithm for X.509 path processing. A con- This text describes an algorithm for X.509 path processing. A
formant implementation MUST include an X.509 path processing pro- conformant implementation MUST include an X.509 path processing
cedure that is functionally equivalent to the external behavior of procedure that is functionally equivalent to the external behavior of
this algorithm. this algorithm. However, some of the certificate fields processed in
this algorithm are optional for compliant implementations. Clients
that do not support these fields may omit the corresponding steps in
the path validation algorithm.
This text assumes that there is a single trust anchor for certifica- For example, clients are not required to support the policy mapping
tion path processing, which simplifies the description of the path extension. Clients that do not support this extension may omit the
processing procedure. This procedure can be extended to address mul- path validation steps where policy mappings are processed. Note that
tiple trust anchors, as discussed further in Section 6.2. clients MUST reject the certificate if it contains critical
extensions that are not supported.
This text describes the trust anchor as an input to the algorithm.
There is no requirement that the same trust anchor be used to
validate all certification paths. Different trust anchors may be
used to validate different paths, as discussed further in Section
6.2.
The primary goal of path validation is to verify the binding between The primary goal of path validation is to verify the binding between
a subject distinguished name or subject alternative name and subject a subject distinguished name or subject alternative name and subject
public key, as represented in the end entity certificate, based on public key, as represented in the end entity certificate, based on
the public key of the trust anchor. This requires obtaining a the public key of the trust anchor. This requires obtaining a
sequence of certificates that support that binding. The procedure sequence of certificates that support that binding. The procedure
performed to obtain this sequence of certificates is outside the performed to obtain this sequence of certificates is outside the
scope of this section. scope of this section.
To meet this goal, the path validation process verifies, among other To meet this goal, the path validation process verifies, among other
things, that a prospective certification path (a sequence of n certi- things, that a prospective certification path (a sequence of n
ficates) satisfies the following conditions: certificates) satisfies the following conditions:
(i) for all x in {1, ..., n-1}, the subject of certificate x is
(a) for all x in {1, ..., n-1}, the subject of certificate x is
the issuer of certificate x+1; the issuer of certificate x+1;
(ii) certificate 1 is issued by the trust anchor;
(iii) certificate n is the end entity certificate; and (b) certificate 1 is issued by the trust anchor;
(iv) for all x in {1, ..., n}, the certificate was valid at the
(c) certificate n is the end entity certificate; and
(d) for all x in {1, ..., n}, the certificate was valid at the
time in question. time in question.
A particular certification path may not, however, be appropriate for A particular certification path may not, however, be appropriate for
all applications. The path validation process also determines the all applications. The path validation process also determines the
set of certificate policies that are valid for this path, based on set of certificate policies that are valid for this path, based on
the certificate policies extension, policy mapping extension, policy the certificate policies extension, policy mapping extension, policy
constraints extension, and inhibit any-policy extension. To achieve constraints extension, and inhibit any-policy extension. To achieve
this, the path validation algorithm constructs a "valid policy tree." this, the path validation algorithm constructs a valid policy tree.
If the set of certificate policies that are valid for this path is If the set of certificate policies that are valid for this path is
not empty, then the result will be a valid policy tree of depth n, not empty, then the result will be a valid policy tree of depth n,
otherwise the result will be a NULL valid policy tree. otherwise the result will be a NULL valid policy tree.
This section presents the algorithm in four basic steps: (1) initial- This section presents the algorithm in four basic steps: (1)
ization, (2) basic certificate processing, (3) preparation for the initialization, (2) basic certificate processing, (3) preparation for
next certificate, and (4) wrap-up. Steps (1) and (4) are performed the next certificate, and (4) wrap-up. Steps (1) and (4) are
exactly once. Step (2) is performed for all certificates in the performed exactly once. Step (2) is performed for all certificates
path. Step (3) is performed for all certificates in the path except in the path. Step (3) is performed for all certificates in the path
the final certificate. Figure 2 provides a high-level flowchart of except the final certificate. Figure 2 provides a high-level
this algorithm. flowchart of this algorithm.
+-------+ +-------+
| START | | START |
+-------+ +-------+
| |
V V
+----------------+ +----------------+
| Initialization | | Initialization |
+----------------+ +----------------+
| |
skipping to change at page 58, line 51 skipping to change at page 61, line 51
This algorithm assumes the following seven inputs are provided to the This algorithm assumes the following seven inputs are provided to the
path processing logic: path processing logic:
(a) a prospective certification path of length n; (a) a prospective certification path of length n;
(b) the time, T, for which the validity of the path should be (b) the time, T, for which the validity of the path should be
determined. This may be the current date/time, or some point in determined. This may be the current date/time, or some point in
the past. the past.
(c) user_initial_policy_set: A set of certificate policy identif- (c) user-initial-policy-set: A set of certificate policy
iers naming the policies that are acceptable to the certificate identifiers naming the policies that are acceptable to the
user. The user_initial_policy_set has the special value "any- certificate user. The user-initial-policy-set contains the special
policy" if the user is not concerned about certificate policy. value any-policy if the user is not concerned about certificate
policy.
(d) trust anchor information, describing a CA that serves as a (d) trust anchor information, describing a CA that serves as a
trust anchor for the certification path. The trust anchor infor- trust anchor for the certification path. The trust anchor
mation includes: information includes:
(1) the trusted issuer name, (1) the trusted issuer name,
(2) optionally, the trusted issuer unique identifier,
(3) the trusted public key algorithm, (2) the trusted public key algorithm,
(4) the trusted public key, and
(5) optionally, the trusted public key parameters associated (3) the trusted public key, and
(4) optionally, the trusted public key parameters associated
with the public key. with the public key.
The trust anchor information may be provided to the path process- The trust anchor information may be provided to the path
ing procedure in the form of a self-signed certificate. The processing procedure in the form of a self-signed certificate. The
trusted anchor information is trusted because it was delivered to trusted anchor information is trusted because it was delivered to
the path processing procedure by some trustworthy "out-of-band" the path processing procedure by some trustworthy out-of-band
procedure. If the trusted public key algorithm requires parame- procedure. If the trusted public key algorithm requires
ters, then the parameters are provided along with the trusted pub- parameters, then the parameters are provided along with the
lic key. trusted public key.
(e) initial-policy-mapping-inhibit, which indicates if policy map- (e) initial-policy-mapping-inhibit, which indicates if policy
ping is allowed in the certification path. mapping is allowed in the certification path.
(f) initial-explicit-policy, which indicates if the path must be (f) initial-explicit-policy, which indicates if the path must be
valid for at least one of the certificate policies in the valid for at least one of the certificate policies in the user-
user_initial_policy_set. initial-policy-set.
(g) initial-any-policy-inhibit, which indicates whether the any- (g) initial-any-policy-inhibit, which indicates whether the any-
policy OID should be processed if it is included in a certificate. policy OID should be processed if it is included in a certificate.
6.1.2 Initialization 6.1.2 Initialization
The initialization phase establishes twelve state variables based The initialization phase establishes eleven state variables based
upon the seven inputs: upon the seven inputs:
(a) valid_policy_tree: A tree of certificate policies with their (a) valid_policy_tree: A tree of certificate policies with their
optional qualifiers; each of the leaves of the tree represents a optional qualifiers; each of the leaves of the tree represents a
valid policy at this stage in the certification path validation. valid policy at this stage in the certification path validation.
If valid policies exist at this stage in the certification path If valid policies exist at this stage in the certification path
validation, the depth of the tree is equal to the number of certi- validation, the depth of the tree is equal to the number of
ficates in the chain that have been processed. If valid policies certificates in the chain that have been processed. If valid
do not exist at this stage in the certification path validation, policies do not exist at this stage in the certification path
the tree is set to NULL. Once the tree is set to NULL, policy pro- validation, the tree is set to NULL. Once the tree is set to NULL,
cessing ceases. policy processing ceases.
Each node in the valid_policy_tree includes four data objects: the Each node in the valid_policy_tree includes four data objects: the
valid policy, a set of associated policy qualifiers, a set of one valid policy, a set of associated policy qualifiers, a set of one
or more expected policy values, and a criticality indicator. If or more expected policy values, and a criticality indicator. If
the node is at depth x, the components of the node have the fol- the node is at depth x, the components of the node have the
lowing semantics: following semantics:
(i) The valid_policy is a single policy OID representing a
(1) The valid_policy is a single policy OID representing a
valid policy for the path of length x. valid policy for the path of length x.
(ii) The qualifier_set is a set of policy qualifiers associated
(2) The qualifier_set is a set of policy qualifiers associated
with the valid policy in certificate x. with the valid policy in certificate x.
(iii) The criticality_indicator indicates whether the certifi-
cate policy extension in certificate x was marked as critical. (3) The criticality_indicator indicates whether the certificate
(iv) The expected_policy_set contains one or more policy OIDs policy extension in certificate x was marked as critical.
(4) The expected_policy_set contains one or more policy OIDs
that would satisfy this policy in the certificate x+1. that would satisfy this policy in the certificate x+1.
The initial value of the valid_policy_tree is a single node with The initial value of the valid_policy_tree is a single node with
valid_policy "any-policy", an empty qualifier_set, an valid_policy any-policy, an empty qualifier_set, an
expected_policy_set with the single value "any-policy", and a expected_policy_set with the single value any-policy, and a
criticality_indicator of FALSE. This node is considered to be at criticality_indicator of FALSE. This node is considered to be at
depth zero. depth zero.
Figure 3 is a graphic representation of the initial state of the Figure 3 is a graphic representation of the initial state of the
valid_policy_tree. Additional figures will use this format to valid_policy_tree. Additional figures will use this format to
describe changes in the valid_policy_tree during path processing. describe changes in the valid_policy_tree during path processing.
+-----------------+ +----------------+
| "any-policy" | <---- valid_policy | any-policy | <---- valid_policy
+-----------------+ +----------------+
| {} | <---- qualifier_set | {} | <---- qualifier_set
+-----------------+ +----------------+
| FALSE | <---- criticality_indicator | FALSE | <---- criticality_indicator
+-----------------+ +----------------+
| {"any-policy"} | <---- expected_policy_set | {any-policy} | <---- expected_policy_set
+-----------------+ +----------------+
Figure 3. Initial value of the valid_policy_tree state variable Figure 3. Initial value of the valid_policy_tree state variable
(b) permitted_subtrees: A set of root names for each name type (b) permitted_subtrees: A set of root names for each name type
(e.g., X.500 distinguished names, email addresses, or ip (e.g., X.500 distinguished names, email addresses, or ip
addresses) defining a set of subtrees within which all subject addresses) defining a set of subtrees within which all subject
names in subsequent certificates in the certification path shall names in subsequent certificates in the certification path shall
fall. This variable includes a set for each name type: the initial fall. This variable includes a set for each name type: the initial
value for the set for Distinguished Names is the set of all Dis- value for the set for Distinguished Names is the set of all
tinguished names; the initial value for the set of RFC822 names is Distinguished names; the initial value for the set of RFC822 names
the set of all RFC822 names, etc. is the set of all RFC822 names, etc.
(c) excluded_subtrees: A set of root names for each name type (c) excluded_subtrees: A set of root names for each name type
(e.g., X.500 distinguished names, email addresses, or ip (e.g., X.500 distinguished names, email addresses, or ip
addresses) defining a set of subtrees within which no subject name addresses) defining a set of subtrees within which no subject name
in subsequent certificates in the certification path may fall. in subsequent certificates in the certification path may fall.
This variable includes a set for each name type, and the initial This variable includes a set for each name type, and the initial
value for each set is "empty". value for each set is empty.
(d) explicit_policy: an integer which indicates if a non-NULL (d) explicit_policy: an integer which indicates if a non-NULL
valid_policy_tree is required. The integer indicates the number of valid_policy_tree is required. The integer indicates the number of
non-self-issued certificates to be processed before this require- non-self-issued certificates to be processed before this
ment is imposed. Once set, this variable may be decreased, but may requirement is imposed. Once set, this variable may be decreased,
not be increased. That is, if a certificate in the path requires a but may not be increased. That is, if a certificate in the path
non-NULL valid_policy_tree, a later certificate can not remove requires a non-NULL valid_policy_tree, a later certificate can not
this requirement. If initial-explicit-policy is set, then the ini- remove this requirement. If initial-explicit-policy is set, then
tial value is 0, otherwise the initial value is n+1. the initial value is 0, otherwise the initial value is n+1.
(e) inhibit_any-policy: an integer which indicates whether the (e) inhibit_any-policy: an integer which indicates whether the
"any-policy" policy identifier is considered a match. The integer any-policy policy identifier is considered a match. The integer
indicates the number of non-self-issued certificates to be pro- indicates the number of non-self-issued certificates to be
cessed before the "any-policy" OID, if asserted in a certificate, processed before the any-policy OID, if asserted in a certificate,
is ignored. Once set, this variable may be decreased, but may not is ignored. Once set, this variable may be decreased, but may not
be increased. That is, if a certificate in the path inhibits pro- be increased. That is, if a certificate in the path inhibits
cessing of "any-policy", a later certificate can not permit it. If processing of any-policy, a later certificate can not permit it.
initial-any-policy-inhibit is set, then the initial value is 0, If initial-any-policy-inhibit is set, then the initial value is 0,
otherwise the initial value is n+1. otherwise the initial value is n+1.
(f) policy_mapping: an integer which indicates if policy mapping (f) policy_mapping: an integer which indicates if policy mapping
is permitted. The integer indicates the number of non-self-issued is permitted. The integer indicates the number of non-self-issued
certificates to be processed before policy mapping is inhibited. certificates to be processed before policy mapping is inhibited.
Once set, this variable may be decreased, but may not be Once set, this variable may be decreased, but may not be
increased. That is, if a certificate in the path specifies policy increased. That is, if a certificate in the path specifies policy
mapping is not permitted, it can not be overridden by a later cer- mapping is not permitted, it can not be overridden by a later
tificate. If initial-policy-mapping-inhibit is set, then the ini- certificate. If initial-policy-mapping-inhibit is set, then the
tial value is 0, otherwise the initial value is n+1. initial value is 0, otherwise the initial value is n+1.
(g) working_public_key_algorithm: the digital signature algorithm (g) working_public_key_algorithm: the digital signature algorithm
used to verify the signature of a certificate. The used to verify the signature of a certificate. The
working_public_key_algorithm is initialized from the trusted pub- working_public_key_algorithm is initialized from the trusted
lic key algorithm provided in the trust anchor information. public key algorithm provided in the trust anchor information.
(h) working_public_key: the public key used to verify the signa- (h) working_public_key: the public key used to verify the
ture of a certificate. The working_public_key is initialized from signature of a certificate. The working_public_key is initialized
the trusted public key provided in the trust anchor information. from the trusted public key provided in the trust anchor
information.
(i) working_public_key_parameters: parameters associated with the (i) working_public_key_parameters: parameters associated with the
current public key, that may required to verify a signature current public key, that may required to verify a signature
(depending upon the algorithm). The working_public_key_parameters (depending upon the algorithm). The working_public_key_parameters
variable is initialized from the trusted public key parameters variable is initialized from the trusted public key parameters
provided in the trust anchor information. provided in the trust anchor information.
(j) working_issuer_name: the issuer distinguished name expected (j) working_issuer_name: the issuer distinguished name expected
in the next certificate in the chain. The working_issuer_name is in the next certificate in the chain. The working_issuer_name is
initialized to the trusted issuer provided in the trust anchor initialized to the trusted issuer provided in the trust anchor
information. information.
(k) working_issuer_UID: a distinguished name may be associated (k) max_path_length: this integer is initialized to n, and is
with an optional unique identifier. The working_issuer_UID is the reset by the path length constraint field within the basic
unique identifier that is expected in the next certificate, or the constraints extension of a CA certificate.
value NULL. The working_issuer_UID is initialized to the trusted
issuer's unique identifier provided in the trust anchor informa-
tion.
(l) max_path_length: this integer is initialized to n, and is
reset by the path length constraint field within the basic con-
straints extension of a CA certificate.
Upon completion of the initialization steps, perform the basic certi- Upon completion of the initialization steps, perform the basic
ficate processing steps specified in 6.1.3. certificate processing steps specified in 6.1.3.
6.1.3 Basic Certificate Processing 6.1.3 Basic Certificate Processing
The basic path processing actions to be performed for certificate i The basic path processing actions to be performed for certificate i
are listed below. are listed below.
(a) Verify the basic certificate information. The certificate (a) Verify the basic certificate information. The certificate
must satisfy each of the following: must satisfy each of the following:
(1) The certificate was signed with the (1) The certificate was signed with the
working_public_key_algorithm using the working_public_key and working_public_key_algorithm using the working_public_key and
the working_public_key_parameters. the working_public_key_parameters.
(2) The certificate validity period includes time T. (2) The certificate validity period includes time T.
(3) At time T, the certificate is not revoked and is not on (3) At time T, the certificate is not revoked and is not on
hold status. This may be determined by obtaining the appropri- hold status. This may be determined by obtaining the
ate CRL (see section 6.3), status information, or by out-of- appropriate CRL (see section 6.3), status information, or by
band mechanisms. out-of-band mechanisms.
(4) The certificate issuer name is the working_issuer_name. (4) The certificate issuer name is the working_issuer_name.
(5) The certificate issuer unique identifier is the (5) The certificate issuer unique identifier is the
working_issuer_UID, meaning: working_issuer_UID, meaning:
(i) working_issuer_UID is non-null and matches the value in (i) working_issuer_UID is non-null and matches the value in
the issuerUID field, or the issuerUID field, or
(ii) working_issuer_UID is null and the issuerUID field is (ii) working_issuer_UID is null and the issuerUID field is
not present. not present.
(b) If certificate i is not self-issued, verify that the subject (b) If certificate i is not self-issued, verify that the subject
name is within one of the permitted_subtrees for X.500 dis- name is within one of the permitted_subtrees for X.500
tinguished names, and verify that each of the alternative names in distinguished names, and verify that each of the alternative names
the subjectAltName extension (critical or non-critical) is within in the subjectAltName extension (critical or non-critical) is
one of the permitted_subtrees for that name type. within one of the permitted_subtrees for that name type.
(c) If certificate i is not self-issued, verify that the subject (c) If certificate i is not self-issued, verify that the subject
name is not within one of the excluded_subtrees for X.500 dis- name is not within one of the excluded_subtrees for X.500
tinguished names, and verify that each of the alternative names in distinguished names, and verify that each of the alternative names
the subjectAltName extension (critical or non-critical) is not in the subjectAltName extension (critical or non-critical) is not
within one of the excluded_subtrees for that name type. within one of the excluded_subtrees for that name type.
(d) If the certificate policies extension is present in the certi- (d) If the certificate policies extension is present in the
ficiate and the valid_policy_tree is not NULL, process the policy certificiate and the valid_policy_tree is not NULL, process the
information by performing the following steps in order: policy information by performing the following steps in order:
(1) For each policy P not equal to "any-policy" in the certifi- (1) For each policy P not equal to any-policy in the
cate policies extension, let P-OID denote the OID in policy P certificate policies extension, let P-OID denote the OID in
and P-Q denote the qualifier set for policy P. Perform the policy P and P-Q denote the qualifier set for policy P.
following steps in order: Perform the following steps in order:
(i) If the valid_policy_tree includes a node of depth i-1 (i) If the valid_policy_tree includes a node of depth i-1
where P-OID is in the expected_policy_set, create a child where P-OID is in the expected_policy_set, create a child
node as follows: set the valid_policy to OID- P; set the node as follows: set the valid_policy to OID- P; set the
qualifier_set to P-Q, and set the expected_policy_set to qualifier_set to P-Q, and set the expected_policy_set to
{P-OID}. {P-OID}.
For example, consider a valid_policy_tree with a node of For example, consider a valid_policy_tree with a node of
depth i-1 where the expected_policy_set is {Gold, White}. depth i-1 where the expected_policy_set is {Gold, White}.
Assume the certificate policies Gold and Silver appear in Assume the certificate policies Gold and Silver appear in
the certificate policies extension of certificate i. The the certificate policies extension of certificate i. The
Gold policy is matched but the Silver policy is not. This Gold policy is matched but the Silver policy is not. This
rule will generate a child node of depth i for the Gold pol- rule will generate a child node of depth i for the Gold
icy. The result is shown as Figure 4. policy. The result is shown as Figure 4.
|-----------------| |-----------------|
| Red | | Red |
|-----------------| |-----------------|
| {} | | {} |
|-----------------| node of depth i-1 |-----------------| node of depth i-1
| FALSE | | FALSE |
|-----------------| |-----------------|
| {Gold, White} | | {Gold, White} |
|-----------------| |-----------------|
skipping to change at page 64, line 32 skipping to change at page 67, line 32
|-----------------| node of depth i |-----------------| node of depth i
| uninitialized | | uninitialized |
|-----------------| |-----------------|
| {Gold} | | {Gold} |
|-----------------| |-----------------|
Figure 4. Processing an exact match Figure 4. Processing an exact match
(ii) If there was no match in step (i) and the (ii) If there was no match in step (i) and the
valid_policy_tree includes a node of depth i-1 with the valid_policy_tree includes a node of depth i-1 with the
valid policy "any-policy", generate a child node with the valid policy any-policy, generate a child node with the
following values: set the valid_policy to P-OID; set the following values: set the valid_policy to P-OID; set the
qualifier_set to P-Q, and set the expected_policy_set to qualifier_set to P-Q, and set the expected_policy_set to
{P-OID}. {P-OID}.
For example, consider a valid_policy_tree with a node of For example, consider a valid_policy_tree with a node of
depth i-1 where the valid_policy is "any-policy". Assume the depth i-1 where the valid_policy is any-policy. Assume the
certificate policies Gold and Silver appear in the certifi- certificate policies Gold and Silver appear in the
cate policies extension of certificate i. The Gold policy certificate policies extension of certificate i. The Gold
does not have a qualifier, but the Silver policy has the policy does not have a qualifier, but the Silver policy has
qualifier Q-Silver. If Gold and Silver were not matched in the qualifier Q-Silver. If Gold and Silver were not matched
(i) above, this rule will generate two child nodes of depth in (i) above, this rule will generate two child nodes of
i, one for each policy. The result is shown as Figure 5. depth i, one for each policy. The result is shown as Figure
5.
|-----------------| |-----------------|
| "any-policy" | | any-policy |
|-----------------| |-----------------|
| {} | | {} |
|-----------------| node of depth i-1 |-----------------| node of depth i-1
| FALSE | | FALSE |
|-----------------| |-----------------|
| {"any-policy"} | | {any-policy} |
|-----------------| |-----------------|
/ \ / \
/ \ / \
/ \ / \
/ \ / \
|-----------------| |-----------------| |-----------------| |-----------------|
| Gold | | Silver | | Gold | | Silver |
|-----------------| |-----------------| |-----------------| |-----------------|
| {} | | {Q-Silver} | | {} | | {Q-Silver} |
|-----------------| nodes of |-----------------| |-----------------| nodes of |-----------------|
| uninitialized | depth i | uninitialized | | uninitialized | depth i | uninitialized |
|-----------------| |-----------------| |-----------------| |-----------------|
| {Gold} | | {Silver} | | {Gold} | | {Silver} |
|-----------------| |-----------------| |-----------------| |-----------------|
Figure 5. Processing unmatched policies when a leaf node Figure 5. Processing unmatched policies when a leaf node
specifies "any-policy" specifies any-policy
(2) If the certificate policies extension includes the pol- (2) If the certificate policies extension includes the policy
icy "any-policy" with the qualifier set AP-Q and any-policy with the qualifier set AP-Q and inhibit_any-policy
inhibit_any-policy is greater than 0, then: is greater than 0, then:
For each node in the valid_policy_tree of depth i-1, for For each node in the valid_policy_tree of depth i-1, for each
each value in the expected_policy_set (including "any- value in the expected_policy_set (including any-policy) that
policy") that does not appear in a child node, create a does not appear in a child node, create a child node with the
child node with the following values: set the valid_policy following values: set the valid_policy to the value from the
to the value from the expected_policy_set in the parent expected_policy_set in the parent node; set the qualifier_set
node; set the qualifier_set to AP-Q, and set the to AP-Q, and set the expected_policy_set to the value in the
expected_policy_set to the value in the valid_policy from valid_policy from this node.
this node.
For example, consider a valid_policy_tree with a node of For example, consider a valid_policy_tree with a node of depth
depth i-1 where the expected_policy_set = {Gold, Silver}. i-1 where the expected_policy_set = {Gold, Silver}. Assume
Assume "any-policy" appears in the certificate policies any-policy appears in the certificate policies extension of
extension of certificate i, but Gold and Silver do not. certificate i, but Gold and Silver do not. This rule will
This rule will generate two child nodes of depth i, one for generate two child nodes of depth i, one for each policy. The
each policy. The result is shown below as Figure 6. result is shown below as Figure 6.
|-----------------| |-----------------|
| Red | | Red |
|-----------------| |-----------------|
| {} | | {} |
|-----------------| node of depth i-1 |-----------------| node of depth i-1
| FALSE | | FALSE |
|-----------------| |-----------------|
| {Gold, Silver} | | {Gold, Silver} |
|-----------------| |-----------------|
/ \ / \
/ \ / \
/ \ / \
/ \ / \
|-----------------| |-----------------| |-----------------| |-----------------|
| Gold | | Silver | | Gold | | Silver |
|-----------------| |-----------------| |-----------------| |-----------------|
| {} | | {} | | {} | | {} |
|-----------------| nodes of |-----------------| |-----------------| nodes of |-----------------|
| uninitialized | depth i | uninitialized | | uninitialized | depth i | uninitialized |
|-----------------| |-----------------| |-----------------| |-----------------|
| {Gold} | | {Silver} | | {Gold} | | {Silver} |
|-----------------| |-----------------| |-----------------| |-----------------|
Figure 6. Processing unmatched policies when the certificate Figure 6. Processing unmatched policies when the certificate
policies extension specifies "any-policy" policies extension specifies any-policy
(3) If there is a node in the valid_policy_tree of depth i-1 (3) If there is a node in the valid_policy_tree of depth i-1 or
or less without any child nodes, delete that node. Repeat less without any child nodes, delete that node. Repeat this
this step until there are no nodes of depth i-1 or less step until there are no nodes of depth i-1 or less without
without children. children.
For example, consider the valid_policy_tree shown in Figure For example, consider the valid_policy_tree shown in Figure 7
7 below. The two nodes at depth i-1 that are marked with an below. The two nodes at depth i-1 that are marked with an to
to the resulting tree will cause the node at depth i-2 that the resulting tree will cause the node at depth i-2 that is
is marked with an 'Y' to be deleted. The following applica- marked with an 'Y' to be deleted. The following application of
tion of the rule does not cause any nodes to be deleted, and the rule does not cause any nodes to be deleted, and this step
this step is complete. is complete.
+-----------+ +-----------+
| | node of depth i-3 | | node of depth i-3
+-----------+ +-----------+
/ | \ / | \
/ | \ / | \
/ | \ / | \
/ | \ +-----------+ +-----------+ +-----------+
+-----------+ +-----------+ +-----------+ | | | | | Y | nodes of
| | | | | Y | nodes of +-----------+ +-----------+ +-----------+ depth i-2
+-----------+ +-----------+ +-----------+ depth i-2 / \ || ||
/ \ \ \ / \ || ||
/ \ \ \ / \ || ||
+-----------+ +-----------+ +-----------+ +-----------+ nodes of +-----------+ +-----------+ +-----------+ +-----------+ nodes of
| | | X | | | | X | depth | | | X | | | | X | depth
+-----------+ +-----------+ +-----------+ +-----------+ i-1 +-----------+ +-----------+ +-----------+ +-----------+ i-1
| / | \ | / | \
| / | \ | / | \
| / | \ | / | \
+-----------+ +-----------+ +-----------+ +-----------+ nodes of +-----------+ +-----------+ +-----------+ +-----------+ nodes of
| | | | | | | | depth | | | | | | | | depth
+-----------+ +-----------+ +-----------+ +-----------+ i +-----------+ +-----------+ +-----------+ +-----------+ i
Figure 7. Pruning the valid_policy_tree Figure 7. Pruning the valid_policy_tree
(4) If the certificate policies extension was marked as criti- (4) If the certificate policies extension was marked as
cal, set the criticality_indicator in all nodes of depth i to critical, set the criticality_indicator in all nodes of depth i
TRUE. If the certificate policies extension was not marked to TRUE. If the certificate policies extension was not marked
critical, set the criticality_indicator in all nodes of depth i critical, set the criticality_indicator in all nodes of depth i
to FALSE. to FALSE.
(e) If the certificate policies extension is not present, set the (e) If the certificate policies extension is not present, set the
valid_policy_tree to NULL. valid_policy_tree to NULL.
(f) verify that either explicit_policy is greater than 0 or the (f) verify that either explicit_policy is greater than 0 or the
valid_policy_tree is not equal to NULL; valid_policy_tree is not equal to NULL;
If any of steps (a), (b), (c), or (f) fails, the procedure ter- If any of steps (a), (b), (c), or (f) fails, the procedure
minates, returning a failure indication and an appropriate reason. terminates, returning a failure indication and an appropriate reason.
If i is not equal to n, continue by performing the preparatory steps If i is not equal to n, continue by performing the preparatory steps
listed in 6.1.4. If i is equal to n, perform the wrap-up steps listed in 6.1.4. If i is equal to n, perform the wrap-up steps
listed in 6.1.5. listed in 6.1.5.
6.1.4 Preparation for Certificate i+1 6.1.4 Preparation for Certificate i+1
To prepare for processing of certificate i+1, perform the following To prepare for processing of certificate i+1, perform the following
steps for certificate i: steps for certificate i:
(a) If a policy mapping extension is present, verify that the spe- (a) If a policy mapping extension is present, verify that the
cial value "any-policy" does not appear as an issuerDomainPolicy special value any-policy does not appear as an issuerDomainPolicy
or a subjectDomainPolicy. or a subjectDomainPolicy.
(b) If a policy mapping extension is present, then for each (b) If a policy mapping extension is present, then for each
issuerDomainPolicy ID-P in the policy mapping extension: issuerDomainPolicy ID-P in the policy mapping extension:
(1) If the policy_mapping variable is greater than 0, for each (1) If the policy_mapping variable is greater than 0, for each
node in the valid_policy_tree of depth i where ID-P is the node in the valid_policy_tree of depth i where ID-P is the
valid_policy, set expected_policy_set to the set of sub- valid_policy, set expected_policy_set to the set of
jectDomainPolicy values that are specified as equivalent to subjectDomainPolicy values that are specified as equivalent to
ID-P by the policy mapping extension. ID-P by the policy mapping extension.
If no node of depth i in the valid_policy_tree has a
valid_policy of ID-P but there is a node of depth i with a
valid_policy of any-policy, then generate a child node of the
node of depth i-1 that has a valid_policy of any-policy as
follows:
(i) set the valid_policy to ID-P;
(ii) set the qualifier_set to the qualifier set of the
policy any-policy in the certificate policies extension of
certificate i;
(iii) set the criticality_indicator to the criticality of
the certificate policies extension of certificate i;
(iv) and set the expected_policy_set to the set of
subjectDomainPolicy values that are specified as equivalent
to ID-P by the policy mappings extension.
(2) If the policy_mapping variable is equal to 0: (2) If the policy_mapping variable is equal to 0:
(i) delete each node of depth i in the valid_policy_tree (i) delete each node of depth i in the valid_policy_tree
where ID-P is the valid_policy. where ID-P is the valid_policy.
(ii) If there is a node in the valid_policy_tree of depth (ii) If there is a node in the valid_policy_tree of depth
i-1 or less without any child nodes, delete that node. i-1 or less without any child nodes, delete that node.
Repeat this step until there are no nodes of depth i-1 or Repeat this step until there are no nodes of depth i-1 or
less without children. less without children.
(c) Assign the certificate subject name to working_issuer_name. (c) Assign the certificate subject name to working_issuer_name.
(d) Assign the certificate subjectPublicKey to working_public_key. (d) Assign the certificate subjectPublicKey to working_public_key.
(e) If the subjectPublicKeyInfo field of the certificate contains (e) If the subjectPublicKeyInfo field of the certificate contains
skipping to change at page 68, line 46 skipping to change at page 72, line 16
If the subjectPublicKeyInfo field of the certificate contains an If the subjectPublicKeyInfo field of the certificate contains an
algorithm field with null parameters or parameters are omitted, algorithm field with null parameters or parameters are omitted,
compare the certificate subjectPublicKey algorithm to the compare the certificate subjectPublicKey algorithm to the
working_public_key_algorithm. If the certificate subjectPublicKey working_public_key_algorithm. If the certificate subjectPublicKey
algorithm and the working_public_key_algorithm are different, set algorithm and the working_public_key_algorithm are different, set
the working_public_key_parameters to null. the working_public_key_parameters to null.
(f) Assign the certificate subjectPublicKey algorithm to the (f) Assign the certificate subjectPublicKey algorithm to the
working_public_key_algorithm variable. working_public_key_algorithm variable.
(g) If a name constraints extension is included in the certifi- (g) If a name constraints extension is included in the
cate, modify the permitted_subtrees and excluded_subtrees state certificate, modify the permitted_subtrees and excluded_subtrees
variables as follows: state variables as follows:
(1) If permittedSubtrees is present in the certificate, set the (1) If permittedSubtrees is present in the certificate, set the
permitted_subtrees state variable to the intersection of its permitted_subtrees state variable to the intersection of its
previous value and the value indicated in the extension field. If previous value and the value indicated in the extension field.
permittedSubtrees does not include a particular name type, the If permittedSubtrees does not include a particular name type,
permitted_subtrees state variable is unchanged for that name type. the permitted_subtrees state variable is unchanged for that
name type.
(2) If excludedSubtrees is present in the certificate, set the (2) If excludedSubtrees is present in the certificate, set the
excluded_subtrees state variable to the union of its previous excluded_subtrees state variable to the union of its previous
value and the value indicated in the extension field. If exclu- value and the value indicated in the extension field. If
dedSubtrees does not include a particular name type, the excludedSubtrees does not include a particular name type, the
excluded_subtrees state variable is unchanged for that name type. excluded_subtrees state variable is unchanged for that name
type.
(h) If the issuer and subject names are not identical: (h) If the issuer and subject names are not identical:
(1) If explicit_policy is not 0, decrement explicit_policy by (1) If explicit_policy is not 0, decrement explicit_policy by
1. 1.
(2) If policy_mapping is not 0, decrement policy_mapping by 1. (2) If policy_mapping is not 0, decrement policy_mapping by 1.
(3) If inhibit_any-policy is not 0, decrement inhibit_any- pol- (3) If inhibit_any-policy is not 0, decrement inhibit_any-
icy by 1. policy by 1.
(i) If a policy constraints extension is included in the certifi- (i) If a policy constraints extension is included in the
cate, modify the explicit_policy and policy_mapping state vari- certificate, modify the explicit_policy and policy_mapping state
ables as follows: variables as follows:
(1) If requireExplicitPolicy is present and is less than (1) If requireExplicitPolicy is present and is less than
explicit_policy, set explicit_policy to the value of requireEx- explicit_policy, set explicit_policy to the value of
plicitPolicy. requireExplicitPolicy.
(2) If inhibitPolicyMapping is present and is less than (2) If inhibitPolicyMapping is present and is less than
policy_mapping, set policy_mapping to the value of inhibitPoli- policy_mapping, set policy_mapping to the value of
cyMapping. inhibitPolicyMapping.
(j) If the inhibitAnyPolicy extension is included in the certifi- (j) If the inhibitAnyPolicy extension is included in the
cate and is less than inhibit_any-policy, set inhibit_any- policy certificate and is less than inhibit_any-policy, set inhibit_any-
to the value of inhibitAnyPolicy. policy to the value of inhibitAnyPolicy.
(k) Verify that the certificate is a CA certificate (as specified (k) Verify that the certificate is a CA certificate (as specified
in a basicConstraints extension or as verified out-of-band). in a basicConstraints extension or as verified out-of-band).
(l) If the certificate was not self-issued, verify that (l) If the certificate was not self-issued, verify that
max_path_length is greater than zero and decrement max_path_length max_path_length is greater than zero and decrement max_path_length
by 1. by 1.
(m) If pathLengthConstraint is present in the certificate and is (m) If pathLengthConstraint is present in the certificate and is
less than max_path_length, set max_path_length to the value of less than max_path_length, set max_path_length to the value of
skipping to change at page 70, line 23 skipping to change at page 73, line 44
i and perform the basic certificate processing specified in 6.1.2. i and perform the basic certificate processing specified in 6.1.2.
6.1.5 Wrap-up procedure 6.1.5 Wrap-up procedure
To complete the processing of the end entity certificate, perform the To complete the processing of the end entity certificate, perform the
following steps for certificate n: following steps for certificate n:
(a) If certificate n was not self-issued and explicit_policy is (a) If certificate n was not self-issued and explicit_policy is
not 0, decrement explicit_policy by 1. not 0, decrement explicit_policy by 1.
(b) If a policy constraints extension is included in the certifi- (b) If a policy constraints extension is included in the
cate and requireExplicitPolicy is present and has a value of 0, certificate and requireExplicitPolicy is present and has a value
set the explicit_policy state variable to 0. of 0, set the explicit_policy state variable to 0.
(c) Assign the certificate subjectPublicKey to working_public_key. (c) Assign the certificate subjectPublicKey to working_public_key.
(d) If the subjectPublicKeyInfo field of the certificate contains (d) If the subjectPublicKeyInfo field of the certificate contains
an algorithm field with non-null parameters, assign the parameters an algorithm field with non-null parameters, assign the parameters
to the working_public_key_parameters variable. to the working_public_key_parameters variable.
If the subjectPublicKeyInfo field of the certificate contains an If the subjectPublicKeyInfo field of the certificate contains an
algorithm field with null parameters or parameters are omitted, algorithm field with null parameters or parameters are omitted,
compare the certificate subjectPublicKey algorithm to the compare the certificate subjectPublicKey algorithm to the
skipping to change at page 70, line 47 skipping to change at page 74, line 19
algorithm and the working_public_key_algorithm are different, set algorithm and the working_public_key_algorithm are different, set
the working_public_key_parameters to null. the working_public_key_parameters to null.
(e) Assign the certificate subjectPublicKey algorithm to the (e) Assign the certificate subjectPublicKey algorithm to the
working_public_key_algorithm variable. working_public_key_algorithm variable.
(f) Recognize and process any other critical extension present in (f) Recognize and process any other critical extension present in
the certificate n. the certificate n.
(g) Calculate the intersection of the valid_policy_tree and the (g) Calculate the intersection of the valid_policy_tree and the
user_initial_policy_set, as follows: user-initial-policy-set, as follows:
(i) If the valid_policy_tree is NULL, the intersection is NULL. (i) If the valid_policy_tree is NULL, the intersection is NULL.
(ii) If the valid_policy_tree is not NULL and the (ii) If the valid_policy_tree is not NULL and the user-
user_initial_policy_set is "any-policy", the intersection is initial-policy-set is any-policy, the intersection is the
the entire valid_policy_tree. entire valid_policy_tree.
(iii) If the valid_policy_tree is not NULL and the user-
initial-policy-set is not any-policy, calculate the
intersection of the valid_policy_tree and the user-initial-
policy-set as follows:
(iii) If the valid_policy_tree is not NULL and the
user_initial_policy_set is not "any-policy", calculate the
intersection of the valid_policy_tree and the
user_initial_policy_set as follows:
1. Determine the set of policy nodes whose parent nodes have 1. Determine the set of policy nodes whose parent nodes have
a valid_policy of "any-policy". This is the a valid_policy of any-policy. This is the
valid_policy_node_set. valid_policy_node_set.
2. If the valid_policy of any node in the 2. If the valid_policy of any node in the
valid_policy_node_set is not in the user_initial_policy_set valid_policy_node_set is not in the user-initial-policy-set
and is not "any-policy", delete this node and all its chil- and is not any-policy, delete this node and all its
dren. children.
3. If there is a node in the valid_policy_tree of depth n-1 3. If there is a node in the valid_policy_tree of depth n-1
or less without any child nodes, delete that node. Repeat or less without any child nodes, delete that node. Repeat
this step until there are no nodes of depth n-1 or less this step until there are no nodes of depth n-1 or less
without children. without children.
Upon completion of all steps, path processing has succeeded if the Upon completion of all steps, path processing has succeeded if the
value of explicit_policy variable is greater than zero, or the value of explicit_policy variable is greater than zero, or the
valid_policy_tree is not NULL. valid_policy_tree is not NULL.
6.1.6 Outputs 6.1.6 Outputs
If path processing succeeds, the procedure terminates, returning a If path processing succeeds, the procedure terminates, returning a
success indication together with final value of the success indication together with final value of the
valid_policy_tree, the working_public_key, the valid_policy_tree, the working_public_key, the
working_public_key_algorithm, and the working_public_key_parameters. working_public_key_algorithm, and the working_public_key_parameters.
6.2 Extending Path Validation 6.2 Using the Path Validation Algorithm
The path validation algorithm presented in 6.1 is based on several The path validation algorithm describes the process of validating a
simplifying assumptions (e.g., a single trusted CA that starts all single certification path. While each path begins with a specific
valid paths). This algorithm may be extended for cases where the trust anchor, there is no requirement that all paths validated by a
assumptions do not hold. particular system share a single trust anchor.
This procedure may be extended for multiple trusted CAs by providing The selection of one or more trusted CAs is a local decision. A
a set of self-signed certificates to the validation module. In this system may provide any one of its trusted CAs as the trust anchor for
case, a valid path could begin with any one of the self-signed certi- a particular path. The inputs to the path validation algorithm may
ficates. Limitations in the trust paths for any particular key may be different for each path. The inputs used to process a path may
be incorporated into the self-signed certificate's extensions. In reflect application-specific requirements or limitations in the trust
this way, the self-signed certificates permit the path validation accorded a particular trust anchor. For example, a trusted CA may
module to automatically incorporate local security policy and only be trusted for a particular certificate policy. This
requirements. restriction can be expressed through the inputs to the path
validation procedure.
It is also possible to specify an extended version of the above cer- It is also possible to specify an extended version of the above
tification path processing procedure which results in default certification path processing procedure which results in default
behavior identical to the rules of PEM [RFC 1422]. In this extended behavior identical to the rules of PEM [RFC 1422]. In this extended
version, additional inputs to the procedure are a list of one or more version, additional inputs to the procedure are a list of one or more
Policy Certification Authorities (PCAs) names and an indicator of the Policy Certification Authorities (PCAs) names and an indicator of the
position in the certification path where the PCA is expected. At the position in the certification path where the PCA is expected. At the
nominated PCA position, the CA name is compared against this list. nominated PCA position, the CA name is compared against this list.
If a recognized PCA name is found, then a constraint of Subordina- If a recognized PCA name is found, then a constraint of
teToCA is implicitly assumed for the remainder of the certification SubordinateToCA is implicitly assumed for the remainder of the
path and processing continues. If no valid PCA name is found, and if certification path and processing continues. If no valid PCA name is
the certification path cannot be validated on the basis of identified found, and if the certification path cannot be validated on the basis
policies, then the certification path is considered invalid. of identified policies, then the certification path is considered
invalid.
6.3 CRL Validation 6.3 CRL Validation
This section describes the steps necessary to determine if a certifi- This section describes the steps necessary to determine if a
cate is revoked or on hold status when CRLs are the revocation certificate is revoked or on hold status when CRLs are the revocation
mechanism used by the certificate issuer. Conforming implementations mechanism used by the certificate issuer. Conforming implementations
of this specification are not required to implement this algorithm, of this specification are not required to implement this algorithm,
but MUST be functionally equivalent to the external behavior result- but MUST be functionally equivalent to the external behavior
ing from this procedure. Any algorithm may be used by a particular resulting from this procedure. Any algorithm may be used by a
implementation so long as it derives the correct result. particular implementation so long as it derives the correct result.
This algorithm defines a set of inputs, a set of state variables, and This algorithm defines a set of inputs, a set of state variables, and
processing steps that are performed for each certificate in the path. processing steps that are performed for each certificate in the path.
6.3.1 Revocation Inputs 6.3.1 Revocation Inputs
To support revocation processing, the algorithm requires two inputs: To support revocation processing, the algorithm requires two inputs:
(a) certificate: the algorithm requires the certificate serial (a) certificate: the algorithm requires the certificate serial
number and issuer name to determine if a certificate is on a par- number and issuer name to determine if a certificate is on a
ticular CRL. The basicConstraints extension is used to determine particular CRL. The basicConstraints extension is used to
whether the supplied certificate is associated with a CA or an determine whether the supplied certificate is associated with a CA
end-entity. If present, the algorithm may use the cRLDistribu- or an end-entity. If present, the algorithm may use the
tionsPoint and freshestCRL extensions to determine revocation cRLDistributionsPoint and freshestCRL extensions to determine
status. revocation status.
(b) use-deltas: This boolean input determines if the delta needs (b) use-deltas: This boolean input determines if the delta needs
to be checked if the CRL is still valid to be checked if the CRL is still valid.
Note that implementations supporting legacy PKIs, such as RFC 1422 Note that implementations supporting legacy PKIs, such as RFC 1422
and X.509 version 1, will need an additional input indicating and X.509 version 1, will need an additional input indicating
whether the supplied certificate is associated with a CA or an whether the supplied certificate is associated with a CA or an
end-entity. end-entity.
6.3.2 Initialization and Revocation State Variables 6.3.2 Initialization and Revocation State Variables
To support CRL processing, the algorithm requires the following state To support CRL processing, the algorithm requires the following state
variables: variables:
(a) reasons_mask: This variable contains the set of revocation (a) reasons_mask: This variable contains the set of revocation
reasons supported by the CRLs and delta CRLs processed so far. The reasons supported by the CRLs and delta CRLs processed so far. The
legal members of the set are the possible values for reasonflags: legal members of the set are the possible values for reasonflags:
unspecified; keyCompromise; caCompromise; affiliationChanged; unspecified; keyCompromise; caCompromise; affiliationChanged;
superseded; cessationOfOperation; and certificateHold. The spe- superseded; cessationOfOperation; and certificateHold. The
cial value "all-reasons" is used to denote the set of all legal special value all-reasons is used to denote the set of all legal
members. This variable is initialized to the empty set. members. This variable is initialized to the empty set.
(b) cert_status: This variable contains the status of the certifi- (b) cert_status: This variable contains the status of the
cate. Legal values are unspecified; keyCompromise; caCompromise; certificate. Legal values are unspecified; keyCompromise;
affiliationChanged; superseded; cessationOfOperation; and certifi- caCompromise; affiliationChanged; superseded;
cateHold, the special value "UNREVOKED", or the special value cessationOfOperation; and certificateHold, the special value
"UNDETERMINED". This variable is initialized to the special value UNREVOKED, or the special value UNDETERMINED. This variable is
"UNREVOKED". initialized to the special value UNREVOKED.
(c) interim_reasons_mask: This contains the set of revocation rea- (c) interim_reasons_mask: This contains the set of revocation
sons supported by the CRL or delta CRL currently being processed. reasons supported by the CRL or delta CRL currently being
processed.
Note: In some environments, it is not necessary to check all reason Note: In some environments, it is not necessary to check all reason
codes. For example, some envornments only are concerned with codes. For example, some envornments only are concerned with
caCompromise and keyCompromise for CA certificates. This algorithnm caCompromise and keyCompromise for CA certificates. This algorithnm
checks all reason codes. Additional processing and state variables checks all reason codes. Additional processing and state variables
may be necessary to limit the checking to a subset of the reason may be necessary to limit the checking to a subset of the reason
codes. codes.
6.3.3 CRL Processing 6.3.3 CRL Processing
This algorithm begins by assuming the certificate is not revoked. This algorithm begins by assuming the certificate is not revoked.
The algorithm checks one or more CRLs until either the certificate The algorithm checks one or more CRLs until either the certificate
status is determined to be revoked or sufficent CRLs have been status is determined to be revoked or sufficent CRLs have been
checked to cover all reason codes. checked to cover all reason codes.
For each distribution point (DP) in the crl distribution points For each distribution point (DP) in the crl distribution points
extension while ((reasons_mask is not "all-reasons") and (cert_status extension while ((reasons_mask is not all-reasons) and (cert_status
is UNREVOKED)) is UNREVOKED))
(1) locate the corresponding CRL in CRL cache, and perform the (1) locate the corresponding CRL in CRL cache, and perform the
following verifications: following verifications:
(a) compute the interim_reasons_mask for this CRL as follows: (a) compute the interim_reasons_mask for this CRL as follows:
1. if the CRL includes reasons and the DP includes reasons, 1. if the CRL includes reasons and the DP includes reasons,
then set interim_reasons_mask to the intersection of of rea- then set interim_reasons_mask to the intersection of of
sons in the DP and reasons in CRL reasons extension. reasons in the DP and reasons in CRL reasons extension.
2. if the CRL includes reasons but the DP omits reasons, 2. if the CRL includes reasons but the DP omits reasons,
then set interim_reasons_mask to the value of CRL reasons. then set interim_reasons_mask to the value of CRL reasons.
3. if the CRL omits reasons but the DP includes reasons, 3. if the CRL omits reasons but the DP includes reasons,
then set interim_reasons_mask to the value of DP reasons. then set interim_reasons_mask to the value of DP reasons.
4. if the CRL omits reasons and the DP omits reasons, then 4. if the CRL omits reasons and the DP omits reasons, then
set interim_reasons_mask to the special value "all-reasons". set interim_reasons_mask to the special value all-reasons.
Verify that interim_reasons_mask includes one or more reasons Verify that interim_reasons_mask includes one or more reasons
that is not included in the reasons_mask. that is not included in the reasons_mask.
(b) Verify the issuer of the CRL as follows: (b) Verify the issuer of the CRL as follows:
if the DP includes cRLIssuer, then verify that the CRL if the DP includes cRLIssuer, then verify that the CRL
issuer matches cRLIssuer else verify that the CRL issuer issuer matches cRLIssuer else verify that the CRL issuer
matches the certificate issuer. matches the certificate issuer.
skipping to change at page 75, line 4 skipping to change at page 78, line 29
issuer issuer
2. validate the signature on the delta CRL 2. validate the signature on the delta CRL
(e) If a delta CRL was obtained in (a) or (b), and the (e) If a delta CRL was obtained in (a) or (b), and the
verifications (c) and (d) suceeded, combine the base and verifications (c) and (d) suceeded, combine the base and
delta to form a complete CRL. delta to form a complete CRL.
(3) If steps and (1) and (2) succeed, then set reasons_mask to the (3) If steps and (1) and (2) succeed, then set reasons_mask to the
union of reasons_mask and interim_reasons_mask union of reasons_mask and interim_reasons_mask
(4) Search for the certificate on the CRL (4) Search for the certificate on the CRL
(a) search for the serial number on the CRL (a) search for the serial number on the CRL
(b) if (a) succeeds, verify that (1) the CRL entry extension (b) if (a) succeeds, verify that (1) the CRL entry extension
Certificate issuer is not present or (2) the issuer identified Certificate issuer is not present or (2) the issuer identified
in the CRL entry extension Certificate issuer is the issuer of in the CRL entry extension Certificate issuer is the issuer of
the certificate. the certificate.
(c) if (a) and (b) succeeded, set the cert_status variable as (c) if (a) and (b) succeeded, set the cert_status variable as
appropriate: appropriate:
1. if the reasons extension is present, set the cert_status 1. if the reasons extension is present, set the cert_status
variable to the value of the reasons extension variable to the value of the reasons extension
2. if the reasons extension is not present, set the 2. if the reasons extension is not present, set the
cert_status variable to the special value "not specified" cert_status variable to the special value not-specified.
if ((reasons_mask is "all-reasons") OR (if cert_status is not if ((reasons_mask is all-reasons) OR (if cert_status is not
UNREVOKED) return cert_status UNREVOKED) return cert_status
If all CRLs named in the crl distribution points extension have If all CRLs named in the crl distribution points extension have
been exhausted, and the reasons_mask is not "all-reasons" and the been exhausted, and the reasons_mask is not all-reasons and the
cert_status is still UNREVOKED, the verifier must obtain addi- cert_status is still UNREVOKED, the verifier must obtain
tional CRLs. If the additional CRLs. If the
The verifier must repeat the process above with the additional The verifier must repeat the process above with the additional
CRLs not specified in a distribution point. CRLs not specified in a distribution point.
If all CRLs are exhausted and the reasons_mask is not "all rea- If all CRLs are exhausted and the reasons_mask is not all-reasons
sons" return the cert_status UNDETERMINED. return the cert_status UNDETERMINED.
7 References 7 References
[RFC 791] J. Postel, "Internet Protocol", September 1981. [RFC 791] J. Postel, "Internet Protocol", September 1981.
[RFC 822] D. Crocker, "Standard for the format of ARPA Internet text [RFC 822] D. Crocker, "Standard for the format of ARPA Internet text
messages", August 1982. messages", August 1982.
[RFC 1034] P.V. Mockapetris, "Domain names - concepts and [RFC 1034] P.V. Mockapetris, "Domain names - concepts and
facilities", November 1987. facilities", November 1987.
skipping to change at page 77, line 24 skipping to change at page 80, line 50
[PKINIT] Tung, B., Neuman C., Hur M., Medvinsky A., Medvinsky S., [PKINIT] Tung, B., Neuman C., Hur M., Medvinsky A., Medvinsky S.,
Wray J., and J. Trostle, "Public Key Cryptography for Wray J., and J. Trostle, "Public Key Cryptography for
Initial Authentciaion in Kerberos," Initial Authentciaion in Kerberos,"
draft-ietf-cat-kerberos-pk-init-11.txt, March 15, 2000. draft-ietf-cat-kerberos-pk-init-11.txt, March 15, 2000.
[PKIX ALGS] Bassham, L., Housley, R., and W. Polk, "Internet X.509 [PKIX ALGS] Bassham, L., Housley, R., and W. Polk, "Internet X.509
Public Key Infrastructure Representation of Public Keys Public Key Infrastructure Representation of Public Keys
and Digital Signatures," and Digital Signatures,"
draft-ietf-pkix-ipki-pkalgs-00.txt, July 14, 2000. draft-ietf-pkix-ipki-pkalgs-00.txt, July 14, 2000.
[PKIX TSA] Cain, P., Pinkas, D., and R. Zuccherato, "Internet X.509
Public Key Infrastructure Time Stamp Protocol,"
draft-ietf-pkix-time-stamp-12.txt, November, 2000.
8 Intellectual Property Rights 8 Intellectual Property Rights
The IETF has been notified of intellectual property rights claimed in The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this docu- regard to some or all of the specification contained in this
ment. For more information consult the online list of claimed document. For more information consult the online list of claimed
rights. rights.
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to per- intellectual property or other rights that might be claimed to
tain to the implementation or use of the technology described in this pertain to the implementation or use of the technology described in
document or the extent to which any license under such rights might this document or the extent to which any license under such rights
or might not be available; neither does it represent that it has made might or might not be available; neither does it represent that it
any effort to identify any such rights. Information on the IETF's has made any effort to identify any such rights. Information on the
procedures with respect to rights in standards-track and standards- IETF's procedures with respect to rights in standards-track and
related documentation can be found in BCP-11. Copies of claims of standards-related documentation can be found in BCP-11. Copies of
rights made available for publication and any assurances of licenses claims of rights made available for publication and any assurances of
to be made available, or the result of an attempt made to obtain a licenses to be made available, or the result of an attempt made to
general license or permission for the use of such proprietary rights obtain a general license or permission for the use of such
by implementors or users of this specification can be obtained from proprietary rights by implementors or users of this specification can
the IETF Secretariat. be obtained from the IETF Secretariat.
9 Security Considerations 9 Security Considerations
The majority of this specification is devoted to the format and con- The majority of this specification is devoted to the format and
tent of certificates and CRLs. Since certificates and CRLs are digi- content of certificates and CRLs. Since certificates and CRLs are
tally signed, no additional integrity service is necessary. Neither digitally signed, no additional integrity service is necessary.
certificates nor CRLs need be kept secret, and unrestricted and Neither certificates nor CRLs need be kept secret, and unrestricted
anonymous access to certificates and CRLs has no security and anonymous access to certificates and CRLs has no security
implications. implications.
However, security factors outside the scope of this specification However, security factors outside the scope of this specification
will affect the assurance provided to certificate users. This sec- will affect the assurance provided to certificate users. This
tion highlights critical issues that should be considered by imple- section highlights critical issues that should be considered by
mentors, administrators, and users. implementors, administrators, and users.
The procedures performed by CAs and RAs to validate the binding of The procedures performed by CAs and RAs to validate the binding of
the subject's identity of their public key greatly affect the the subject's identity of their public key greatly affect the
assurance that should be placed in the certificate. Relying parties assurance that should be placed in the certificate. Relying parties
may wish to review the CA's certificate practice statement. This may may wish to review the CA's certificate practice statement. This may
be particularly important when issuing certificates to other CAs. be particularly important when issuing certificates to other CAs.
The use of a single key pair for both signature and other purposes is The use of a single key pair for both signature and other purposes is
strongly discouraged. Use of separate key pairs for signature and key strongly discouraged. Use of separate key pairs for signature and key
management provides several benefits to the users. The ramifications management provides several benefits to the users. The ramifications
associated with loss or disclosure of a signature key are different associated with loss or disclosure of a signature key are different
from loss or disclosure of a key management key. Using separate key from loss or disclosure of a key management key. Using separate key
pairs permits a balanced and flexible response. Similarly, different pairs permits a balanced and flexible response. Similarly, different
validity periods or key lengths for each key pair may be appropriate validity periods or key lengths for each key pair may be appropriate
in some application environments. Unfortunately, some legacy applica- in some application environments. Unfortunately, some legacy
tions (e.g., SSL) use a single key pair for signature and key manage- applications (e.g., SSL) use a single key pair for signature and key
ment. management.
The protection afforded private keys is a critical factor in main- The protection afforded private keys is a critical factor in
taining security. On a small scale, failure of users to protect maintaining security. On a small scale, failure of users to protect
their private keys will permit an attacker to masquerade as them, or their private keys will permit an attacker to masquerade as them, or
decrypt their personal information. On a larger scale, compromise of decrypt their personal information. On a larger scale, compromise of
a CA's private signing key may have a catastrophic effect. If an a CA's private signing key may have a catastrophic effect. If an
attacker obtains the private key unnoticed, the attacker may issue attacker obtains the private key unnoticed, the attacker may issue
bogus certificates and CRLs. Existence of bogus certificates and bogus certificates and CRLs. Existence of bogus certificates and
CRLs will undermine confidence in the system. If the compromise is CRLs will undermine confidence in the system. If the compromise is
detected, all certificates issued to the CA shall be revoked, detected, all certificates issued to the CA shall be revoked,
preventing services between its users and users of other CAs. preventing services between its users and users of other CAs.
Rebuilding after such a compromise will be problematic, so CAs are Rebuilding after such a compromise will be problematic, so CAs are
advised to implement a combination of strong technical measures advised to implement a combination of strong technical measures
(e.g., tamper-resistant cryptographic modules) and appropriate (e.g., tamper-resistant cryptographic modules) and appropriate
management procedures (e.g., separation of duties) to avoid such an management procedures (e.g., separation of duties) to avoid such an
incident. incident.
Loss of a CA's private signing key may also be problematic. The CA Loss of a CA's private signing key may also be problematic. The CA
would not be able to produce CRLs or perform normal key rollover. would not be able to produce CRLs or perform normal key rollover.
CAs are advised to maintain secure backup for signing keys. The CAs are advised to maintain secure backup for signing keys. The
security of the key backup procedures is a critical factor in avoid- security of the key backup procedures is a critical factor in
ing key compromise. avoiding key compromise.
The availability and freshness of revocation information will affect The availability and freshness of revocation information will affect
the degree of assurance that should be placed in a certificate. the degree of assurance that should be placed in a certificate.
While certificates expire naturally, events may occur during its While certificates expire naturally, events may occur during its
natural lifetime which negate the binding between the subject and natural lifetime which negate the binding between the subject and
public key. If revocation information is untimely or unavailable, public key. If revocation information is untimely or unavailable,
the assurance associated with the binding is clearly reduced. Simi- the assurance associated with the binding is clearly reduced.
larly, implementations of the Path Validation mechanism described in Similarly, implementations of the Path Validation mechanism described
section 6 that omit revocation checking provide less assurance than in section 6 that omit revocation checking provide less assurance
those that support it. than those that support it.
The path validation algorithm depends on the certain knowledge of the The path validation algorithm depends on the certain knowledge of the
public keys (and other information) about one or more trusted CAs. public keys (and other information) about one or more trusted CAs.
The decision to trust a CA is an important decision as it ultimately The decision to trust a CA is an important decision as it ultimately
determines the trust afforded a certificate. The authenticated dis- determines the trust afforded a certificate. The authenticated
tribution of trusted CA public keys (usually in the form of a "self- distribution of trusted CA public keys (usually in the form of a
signed" certificate) is a security critical out of band process that "self-signed" certificate) is a security critical out of band process
is beyond the scope of this specification. that is beyond the scope of this specification.
In addition, where a key compromise or CA failure occurs for a In addition, where a key compromise or CA failure occurs for a
trusted CA, the user will need to modify the information provided to trusted CA, the user will need to modify the information provided to
the path validation routine. Selection of too many trusted CAs will the path validation routine. Selection of too many trusted CAs will
make the trusted CA information difficult to maintain. On the other make the trusted CA information difficult to maintain. On the other
hand, selection of only one trusted CA may limit users to a closed hand, selection of only one trusted CA may limit users to a closed
community of users until a global PKI emerges. community of users until a global PKI emerges.
The quality of implementations that process certificates may also The quality of implementations that process certificates may also
affect the degree of assurance provided. The path validation algo- affect the degree of assurance provided. The path validation
rithm described in section 6 relies upon the integrity of the trusted algorithm described in section 6 relies upon the integrity of the
CA information, and especially the integrity of the public keys asso- trusted CA information, and especially the integrity of the public
ciated with the trusted CAs. By substituting public keys for which keys associated with the trusted CAs. By substituting public keys
an attacker has the private key, an attacker could trick the user for which an attacker has the private key, an attacker could trick
into accepting false certificates. the user into accepting false certificates.
The binding between a key and certificate subject cannot be stronger The binding between a key and certificate subject cannot be stronger
than the cryptographic module implementation and algorithms used to than the cryptographic module implementation and algorithms used to
generate the signature. Short key lengths or weak hash algorithms generate the signature. Short key lengths or weak hash algorithms
will limit the utility of a certificate. CAs are encouraged to note will limit the utility of a certificate. CAs are encouraged to note
advances in cryptology so they can employ strong cryptographic tech- advances in cryptology so they can employ strong cryptographic
niques. In addition, CAs should decline to issue certificates to CAs techniques. In addition, CAs should decline to issue certificates to
or end entities that generate weak signatures. CAs or end entities that generate weak signatures.
Inconsistent application of name comparison rules may result in Inconsistent application of name comparison rules may result in
acceptance of invalid X.509 certification paths, or rejection of acceptance of invalid X.509 certification paths, or rejection of
valid ones. The X.500 series of specifications defines rules for valid ones. The X.500 series of specifications defines rules for
comparing distinguished names require comparison of strings without comparing distinguished names require comparison of strings without
regard to case, character set, multi-character white space substring, regard to case, character set, multi-character white space substring,
or leading and trailing white space. This specification relaxes or leading and trailing white space. This specification relaxes
these requirements, requiring support for binary comparison at a these requirements, requiring support for binary comparison at a
minimum. minimum.
CAs shall encode the distinguished name in the subject field of a CA CAs shall encode the distinguished name in the subject field of a CA
certificate identically to the distinguished name in the issuer field certificate identically to the distinguished name in the issuer field
in certificates issued by the latter CA. If CAs use different encod- in certificates issued by the latter CA. If CAs use different
ings, implementations of this specification may fail to recognize encodings, implementations of this specification may fail to
name chains for paths that include this certificate. As a conse- recognize name chains for paths that include this certificate. As a
quence, valid paths could be rejected. consequence, valid paths could be rejected.
In addition, name constraints for distinguished names shall be stated In addition, name constraints for distinguished names shall be stated
identically to the encoding used in the subject field or subjectAlt- identically to the encoding used in the subject field or
Name extension. If not, (1) name constraints stated as excludedSub- subjectAltName extension. If not, (1) name constraints stated as
Trees will not match and invalid paths will be accepted and (2) name excludedSubTrees will not match and invalid paths will be accepted
constraints expressed as permittedSubtrees will not match and valid and (2) name constraints expressed as permittedSubtrees will not
paths will be rejected. To avoid acceptance of invalid paths, CAs match and valid paths will be rejected. To avoid acceptance of
should state name constraints for distinguished names as permit- invalid paths, CAs should state name constraints for distinguished
tedSubtrees where ever possible. names as permittedSubtrees where ever possible.
Appendix A. Psuedo-ASN.1 Structures and OIDs Appendix A. Psuedo-ASN.1 Structures and OIDs
This section describes data objects used by conforming PKI components This section describes data objects used by conforming PKI components
in an "ASN.1-like" syntax. This syntax is a hybrid of the 1988 and in an "ASN.1-like" syntax. This syntax is a hybrid of the 1988 and
1993 ASN.1 syntaxes. The 1988 ASN.1 syntax is augmented with 1993 1993 ASN.1 syntaxes. The 1988 ASN.1 syntax is augmented with 1993
UNIVERSAL Types UniversalString, BMPString and UTF8String. UNIVERSAL Types UniversalString, BMPString and UTF8String.
The ASN.1 syntax does not permit the inclusion of type statements in The ASN.1 syntax does not permit the inclusion of type statements in
the ASN.1 module, and the 1993 ASN.1 standard does not permit use of the ASN.1 module, and the 1993 ASN.1 standard does not permit use of
skipping to change at page 82, line 27 skipping to change at page 85, line 27
id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 } id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 }
-- OID for CPS qualifier -- OID for CPS qualifier
id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 } id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 }
-- OID for user notice qualifier -- OID for user notice qualifier
-- access descriptor definitions -- access descriptor definitions
id-ad-ocsp OBJECT IDENTIFIER ::= { id-ad 1 } id-ad-ocsp OBJECT IDENTIFIER ::= { id-ad 1 }
id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 } id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 }
id-ad-timeStamping OBJECT IDENTIFIER ::= { id-ad 3 }
id-ad-caRepository OBJECT IDENTIFIER ::= { id-ad 5 }
-- attribute data types -- -- attribute data types --
Attribute ::= SEQUENCE { Attribute ::= SEQUENCE {
type AttributeType, type AttributeType,
values SET OF AttributeValue values SET OF AttributeValue
-- at least one value is required -- } -- at least one value is required -- }
AttributeType ::= OBJECT IDENTIFIER AttributeType ::= OBJECT IDENTIFIER
skipping to change at page 101, line 6 skipping to change at page 104, line 6
-- invalidity date CRL entry extension OID and syntax -- invalidity date CRL entry extension OID and syntax
id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 } id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 }
InvalidityDate ::= GeneralizedTime InvalidityDate ::= GeneralizedTime
END END
Appendix B. ASN.1 Notes Appendix B. ASN.1 Notes
CAs MUST force the serialNumber to be a positive integer, that is, CAs MUST force the serialNumber to be a non-negative integer, that
the sign bit in the DER encoding of the INTEGER value MUST be zero - is, the sign bit in the DER encoding of the INTEGER value MUST be
this can be done by adding a leading (leftmost) `00'H octet if neces- zero - this can be done by adding a leading (leftmost) `00'H octet if
sary. This removes a potential ambiguity in mapping between a string necessary. This removes a potential ambiguity in mapping between a
of octets and an integer value. string of octets and an integer value.
Given the uniqueness requirements above serial numbers can be As noted in section 4.1.2.2, serial numbers can be expected to
expected to contain long integers. Certificate users MUST be able to contain long integers. Certificate users MUST be able to handle
handle serialNumber values longer than 32 bits. Conformant CAs MUST serialNumber values up to 20 octets in length. Conformant CAs MUST
NOT use serialNumber values longer than 20 octets. NOT use serialNumber values longer than 20 octets.
The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1 The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1
constructs. A valid ASN.1 sequence will have zero or more entries. constructs. A valid ASN.1 sequence will have zero or more entries.
The SIZE (1..MAX) construct constrains the sequence to have at least The SIZE (1..MAX) construct constrains the sequence to have at least
one entry. MAX indicates the upper bound is unspecified. Implementa- one entry. MAX indicates the upper bound is unspecified.
tions are free to choose an upper bound that suits their environment. Implementations are free to choose an upper bound that suits their
environment.
The construct "positiveInt ::= INTEGER (0..MAX)" defines positiveInt The construct "positiveInt ::= INTEGER (0..MAX)" defines positiveInt
as a subtype of INTEGER containing integers greater than or equal to as a subtype of INTEGER containing integers greater than or equal to
zero. The upper bound is unspecified. Implementations are free to zero. The upper bound is unspecified. Implementations are free to
select an upper bound that suits their environment. select an upper bound that suits their environment.
The character string type PrintableString supports a very basic Latin The character string type PrintableString supports a very basic Latin
character set: the lower case letters 'a' through 'z', upper case character set: the lower case letters 'a' through 'z', upper case
letters 'A' through 'Z', the digits '0' through '9', eleven special letters 'A' through 'Z', the digits '0' through '9', eleven special
characters ' " ( ) + , - . / : ? and space. characters ' " ( ) + , - . / : ? and space.
The character string type TeletexString is a superset of Printable- The character string type TeletexString is a superset of
String. TeletexString supports a fairly standard (ascii-like) Latin PrintableString. TeletexString supports a fairly standard (ascii-
character set, Latin characters with non-spacing accents and Japanese like) Latin character set, Latin characters with non-spacing accents
characters. and Japanese characters.
The character string type UniversalString supports any of the charac- The character string type UniversalString supports any of the
ters allowed by ISO 10646-1. ISO 10646 is the Universal multiple- characters allowed by ISO 10646-1. ISO 10646 is the Universal
octet coded Character Set (UCS). ISO 10646-1 specifes the architec- multiple-octet coded Character Set (UCS). ISO 10646-1 specifes the
ture and the "basic multilingual plane" - a large standard character architecture and the "basic multilingual plane" - a large standard
set which includes all major world character standards. character set which includes all major world character standards.
The character string type UTF8String will be introduced in the 1998 The character string type UTF8String will be introduced in the 1998
version of ASN.1. UTF8String is a universal type and has been version of ASN.1. UTF8String is a universal type and has been
assigned tag number 12. The content of UTF8String was defined by RFC assigned tag number 12. The content of UTF8String was defined by RFC
2044 and updated in RFC 2279, "UTF-8, a transformation Format of ISO 2044 and updated in RFC 2279, "UTF-8, a transformation Format of ISO
10646." ISO is expected to formally add UTF8String to the list of 10646." ISO is expected to formally add UTF8String to the list of
choices for DirectoryString in 1998 as well. choices for DirectoryString in 1998 as well.
In anticipation of these changes, and in conformance with IETF Best In anticipation of these changes, and in conformance with IETF Best
Practices codified in RFC 2277, IETF Policy on Character Sets and Practices codified in RFC 2277, IETF Policy on Character Sets and
Languages, this document includes UTF8String as a choice in Directo- Languages, this document includes UTF8String as a choice in
ryString and the CPS qualifier extensions. DirectoryString and the CPS qualifier extensions.
Implementers should note that the DER encoding of the SET OF values Implementers should note that the DER encoding of the SET OF values
requires ordering of the encodings of the values. In particular, this requires ordering of the encodings of the values. In particular, this
issue arises with respect to distinguished names. issue arises with respect to distinguished names.
Object Identifiers (OIDs) are used throught this specification to Object Identifiers (OIDs) are used throught this specification to
identify certificate policies, public key and signature algorithms, identify certificate policies, public key and signature algorithms,
certificate extensions, etc. There is no maximum size for OIDs. certificate extensions, etc. There is no maximum size for OIDs.
This specification mandates support for OIDs which have arc elements This specification mandates support for OIDs which have arc elements
with values that are less than 2^28, i.e. they MUST be between 0 and with values that are less than 2^28, i.e. they MUST be between 0 and
268,435,455 inclusive. This allows each arc element to be represented 268,435,455 inclusive. This allows each arc element to be represented
within a single 32 bit word. Implementations MUST also support OIDs within a single 32 bit word. Implementations MUST also support OIDs
where the length of the dotted decimal (see [LDAP], section 4.1.2) where the length of the dotted decimal (see [LDAP], section 4.1.2)
string representation can be up to 100 bytes (inclusive). Implementa- string representation can be up to 100 bytes (inclusive).
tions MUST be able to handle OIDs with up to 20 elements (inclusive). Implementations MUST be able to handle OIDs with up to 20 elements
CAs SHOULD NOT issue certificates which contain OIDs that breach (inclusive). CAs SHOULD NOT issue certificates which contain OIDs
these requirements. that breach these requirements.
Appendix C. Examples Appendix C. Examples
This section contains four examples: three certificates and a CRL. This section contains four examples: three certificates and a CRL.
The first two certificates and the CRL comprise a minimal certifica- The first two certificates and the CRL comprise a minimal
tion path. certification path.
Section C.1 contains an annotated hex dump of a "self-signed" certi- Section C.1 contains an annotated hex dump of a "self-signed"
ficate issued by a CA whose distinguished name is certificate issued by a CA whose distinguished name is
cn=us,o=gov,ou=nist. The certificate contains a DSA public key with cn=us,o=gov,ou=nist. The certificate contains a DSA public key with
parameters, and is signed by the corresponding DSA private key. parameters, and is signed by the corresponding DSA private key.
Section C.2 contains an annotated hex dump of an end-entity certifi- Section C.2 contains an annotated hex dump of an end-entity
cate. The end entity certificate contains a DSA public key, and is certificate. The end entity certificate contains a DSA public key,
signed by the private key corresponding to the "self-signed" certifi- and is signed by the private key corresponding to the "self-signed"
cate in section C.1. certificate in section C.1.
Section C.3 contains a dump of an end entity certificate which con- Section C.3 contains a dump of an end entity certificate which
tains an RSA public key and is signed with RSA and MD5. This certi- contains an RSA public key and is signed with RSA and MD5. This
ficate is not part of the minimal certification path. certificate is not part of the minimal certification path.
Section C.4 contains an annotated hex dump of a CRL. The CRL is Section C.4 contains an annotated hex dump of a CRL. The CRL is
issued by the CA whose distinguished name is cn=us,o=gov,ou=nist and issued by the CA whose distinguished name is cn=us,o=gov,ou=nist and
the list of revoked certificates includes the end entity certificate the list of revoked certificates includes the end entity certificate
presented in C.2. presented in C.2.
The certificates were processed using Peter Gutman's dumpasn1 utility The certificates were processed using Peter Gutman's dumpasn1 utility
to generate the output. The source for the dumpasn1 utility is to generate the output. The source for the dumpasn1 utility is
available at <http://www.cs.auckland.ac.nz/~pgut001/dumpasn1.c>. The available at <http://www.cs.auckland.ac.nz/~pgut001/dumpasn1.c>. The
binaries for the certificates and CRLs are available at binaries for the certificates and CRLs are available at
skipping to change at page 103, line 18 skipping to change at page 106, line 19
C.1 Certificate C.1 Certificate
This section contains an annotated hex dump of a 699 byte version 3 This section contains an annotated hex dump of a 699 byte version 3
certificate. The certificate contains the following information: certificate. The certificate contains the following information:
(a) the serial number is 23 (17 hex); (a) the serial number is 23 (17 hex);
(b) the certificate is signed with DSA and the SHA-1 hash algorithm; (b) the certificate is signed with DSA and the SHA-1 hash algorithm;
(c) the issuer's distinguished name is OU=NIST; O=gov; C=US (c) the issuer's distinguished name is OU=NIST; O=gov; C=US
(d) and the subject's distinguished name is OU=NIST; O=gov; C=US (d) and the subject's distinguished name is OU=NIST; O=gov; C=US
(e) the certificate was issued on June 30, 1997 and will expire on (e) the certificate was issued on June 30, 1997 and will expire on
December 31, 1997; December 31, 1997;
(f) the certificate contains a 1024 bit DSA public key with parame- (f) the certificate contains a 1024 bit DSA public key with
ters; parameters;
(g) the certificate contains a subject key identifier extension; and (g) the certificate contains a subject key identifier extension; and
(h) the certificate is a CA certificate (as indicated through the (h) the certificate is a CA certificate (as indicated through the
basic constraints extension.) basic constraints extension.)
0 30 701: SEQUENCE { 0 30 701: SEQUENCE {
4 30 637: SEQUENCE { 4 30 637: SEQUENCE {
8 A0 3: [0] { 8 A0 3: [0] {
10 02 1: INTEGER 2 10 02 1: INTEGER 2
: } : }
13 02 1: INTEGER 23 13 02 1: INTEGER 23
skipping to change at page 106, line 17 skipping to change at page 109, line 17
This section contains an annotated hex dump of a 730 byte version 3 This section contains an annotated hex dump of a 730 byte version 3
certificate. The certificate contains the following information: certificate. The certificate contains the following information:
(a) the serial number is 18 (12 hex); (a) the serial number is 18 (12 hex);
(b) the certificate is signed with DSA and the SHA-1 hash algorithm; (b) the certificate is signed with DSA and the SHA-1 hash algorithm;
(c) the issuer's distinguished name is OU=nist; O=gov; C=US (c) the issuer's distinguished name is OU=nist; O=gov; C=US
(d) and the subject's distinguished name is CN=Tim Polk; OU=nist; (d) and the subject's distinguished name is CN=Tim Polk; OU=nist;
O=gov; C=US O=gov; C=US
(e) the certificate was valid from July 30, 1997 through December 1, (e) the certificate was valid from July 30, 1997 through December 1,
1997; 1997;
(f) the certificate contains a 1024 bit DSA public key; (f) the certificate contains a 1024 bit DSA public key;
(g) the certificate is an end entity certificate, as the basic con- (g) the certificate is an end entity certificate, as the basic
straints extension is not present; constraints extension is not present;
(h) the certificate contains an authority key identifier extension; (h) the certificate contains an authority key identifier extension;
and and
(i) the certificate includes one alternative name - an RFC 822 (i) the certificate includes one alternative name - an RFC 822
address. address.
0 30 734: SEQUENCE { 0 30 734: SEQUENCE {
4 30 669: SEQUENCE { 4 30 669: SEQUENCE {
8 A0 3: [0] { 8 A0 3: [0] {
10 02 1: INTEGER 2 10 02 1: INTEGER 2
: } : }
skipping to change at page 109, line 13 skipping to change at page 112, line 13
: EA CC 22 B2 16 01 FF 13 02 15 00 97 D0 24 96 0F : EA CC 22 B2 16 01 FF 13 02 15 00 97 D0 24 96 0F
: 64 8A C3 8D 41 B2 0E B9 26 D5 31 D1 A0 F1 BC : 64 8A C3 8D 41 B2 0E B9 26 D5 31 D1 A0 F1 BC
: } : }
C.3 End-Entity Certificate Using RSA C.3 End-Entity Certificate Using RSA
This section contains an annotated hex dump of a 675 byte version 3 This section contains an annotated hex dump of a 675 byte version 3
certificate. The certificate contains the following information: certificate. The certificate contains the following information:
(a) the serial number is 256; (a) the serial number is 256;
(b) the certificate is signed with RSA and the MD2 hash algorithm; (b) the certificate is signed with RSA and the MD2 hash algorithm;
(c) the issuer's distinguished name is OU=Dept. Arquitectura de Com- (c) the issuer's distinguished name is OU=Dept. Arquitectura de
putadors; O=Universitat Politecnica de Catalunya; C=ES Computadors; O=Universitat Politecnica de Catalunya; C=ES
(d) and the subject's distinguished name is CN=Francisco Jordan; (d) and the subject's distinguished name is CN=Francisco Jordan;
OU=Dept. Arquitectura de Computadors; O=Universitat Politecnica de OU=Dept. Arquitectura de Computadors; O=Universitat Politecnica de
Catalunya; C=ES Catalunya; C=ES
(e) the certificate was issued on May 21, 1996 and expired on May 21, (e) the certificate was issued on May 21, 1996 and expired on May 21,
1997; 1997;
(f) the certificate contains a 768 bit RSA public key; (f) the certificate contains a 768 bit RSA public key;
(g) the certificate is an end entity certificate (not a CA certifi- (g) the certificate is an end entity certificate (not a CA
cate); certificate);
(h) the certificate includes an alternative subject name and an (h) the certificate includes an alternative subject name and an
alternative issuer name - bothe are URLs; alternative issuer name - bothe are URLs;
(i) the certificate include an authority key identifier and certifi- (i) the certificate include an authority key identifier and
cate policies extensions; and certificate policies extensions; and
(j) the certificate includes a critical key usage extension specify- (j) the certificate includes a critical key usage extension
ing the public is intended for generation of digital signatures. specifying the public is intended for generation of digital
signatures.
0 30 654: SEQUENCE { 0 30 654: SEQUENCE {
4 30 503: SEQUENCE { 4 30 503: SEQUENCE {
8 A0 3: [0] { 8 A0 3: [0] {
10 02 1: INTEGER 2 10 02 1: INTEGER 2
: } : }
13 02 2: INTEGER 256 13 02 2: INTEGER 256
17 30 13: SEQUENCE { 17 30 13: SEQUENCE {
19 06 9: OBJECT IDENTIFIER 19 06 9: OBJECT IDENTIFIER
: sha1withRSAEncryption (1 2 840 113549 1 1 5) : sha1withRSAEncryption (1 2 840 113549 1 1 5)
skipping to change at page 114, line 50 skipping to change at page 117, line 50
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. In addition, the included on all such copies and derivative works. In addition, the
ASN.1 modules presented in Appendices A and B may be used in whole or ASN.1 modules presented in Appendices A and B may be used in whole or
in part without inclusion of the copyright notice. However, this in part without inclusion of the copyright notice. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of develop- Internet organizations, except as needed for the purpose of
ing Internet standards in which case the procedures for copyrights developing Internet standards in which case the procedures for
defined in the Internet Standards process shall be followed, or as copyrights defined in the Internet Standards process shall be
required to translate it into languages other than English. followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. This revoked by the Internet Society or its successors or assigns. This
document and the information contained herein is provided on an "AS document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
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