PKIX Working Group R. Housley (SPYRUS) Internet Draft W. Ford (VeriSign) W. Polk (NIST) D. Solo (Citigroup) expires in six months July 14, 2000 Internet X.509 Public Key Infrastructure Certificate and CRL Profile Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Copyright (C) The Internet Society (1998). All Rights Reserved. Abstract This is the first draft of a specification based upon RFC 2459. When complete, this specification will obsolete RFC 2459. This specification includes numerous edits and clarifications. The most notable departures from RFC 2459 are found in Section 6, Path Validation. In RFC 2459, the reader was expected to augment the path validation algorithm, which concentrated upon policy processing, with information embedded in earlier sections. For example, parameter inheritance is discussed in Section 7, Algorithm Support, and can certainly affect the validity of a certification path. However, parameter inheritance was omitted from the path validation algorithm Housley, Ford, Polk, & Solo [Page 1] INTERNET DRAFT July 14, 2000 in RFC 2459. In this draft, the path validation algorithm has a comprehensive and extremely detailed description. Details such as parameter inheritance are covered thoroughly. In addition, this draft anticipates certain corrections proposed in the X.509 standard for the policy processing aspects of path validation. A new section 6.3, CRL validation, has been added as well. This section provides a supplement to the path validation algorithm that determines if a particular CRL may be used to verify the status of a particular certificate. (The basic path validation algorithm is, by design, independent of the type and format of status information.) This memo profiles the X.509 v3 certificate and X.509 v2 CRL for use in the Internet. An overview of the approach and model are provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms (e.g., IP addresses). Standard certificate extensions are described and one new Internet-specific extension is defined. A required set of certificate extensions is specified. The X.509 v2 CRL format is described and a required extension set is defined as well. An algorithm for X.509 certificate path validation is described. Supplemental information is provided describing the format of public keys and digital signatures in X.509 certificates for common Internet public key encryption algorithms (i.e., RSA, DSA, and Diffie-Hellman). ASN.1 modules and examples are provided in the appendices. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Please send comments on this document to the ietf-pkix@imc.org mail list. Housley, Ford, Polk, & Solo [Page 2] INTERNET DRAFT July 14, 2000 Table of Contents 1 Introduction ................................................ 6 2 Requirements and Assumptions ................................ 7 2.1 Communication and Topology ................................ 7 2.2 Acceptability Criteria .................................... 8 2.3 User Expectations ......................................... 8 2.4 Administrator Expectations ................................ 8 3 Overview of Approach ........................................ 8 3.1 X.509 Version 3 Certificate ............................... 10 3.2 Certification Paths and Trust ............................. 11 3.3 Revocation ................................................ 13 3.4 Operational Protocols ..................................... 14 3.5 Management Protocols ...................................... 14 4 Certificate and Certificate Extensions Profile .............. 15 4.1 Basic Certificate Fields .................................. 16 4.1.1 Certificate Fields ...................................... 17 4.1.1.1 tbsCertificate ........................................ 17 4.1.1.2 signatureAlgorithm .................................... 17 4.1.1.3 signatureValue ........................................ 18 4.1.2 TBSCertificate .......................................... 18 4.1.2.1 Version ............................................... 18 4.1.2.2 Serial number ......................................... 18 4.1.2.3 Signature ............................................. 19 4.1.2.4 Issuer ................................................ 19 4.1.2.5 Validity .............................................. 22 4.1.2.5.1 UTCTime ............................................. 23 4.1.2.5.2 GeneralizedTime ..................................... 23 4.1.2.6 Subject ............................................... 23 4.1.2.7 Subject Public Key Info ............................... 24 4.1.2.8 Unique Identifiers .................................... 25 4.1.2.9 Extensions ............................................. 25 4.2 Certificate Extensions .................................... 26 4.2.1 Standard Extensions ..................................... 26 4.2.1.1 Authority Key Identifier .............................. 26 4.2.1.2 Subject Key Identifier ................................ 27 4.2.1.3 Key Usage ............................................. 28 4.2.1.4 Private Key Usage Period .............................. 30 4.2.1.5 Certificate Policies .................................. 30 4.2.1.6 Policy Mappings ....................................... 33 4.2.1.7 Subject Alternative Name .............................. 33 4.2.1.8 Issuer Alternative Name ............................... 36 4.2.1.9 Subject Directory Attributes .......................... 36 Housley, Ford, Polk, & Solo [Page 3] INTERNET DRAFT July 14, 2000 4.2.1.10 Basic Constraints .................................... 36 4.2.1.11 Name Constraints ..................................... 37 4.2.1.12 Policy Constraints ................................... 39 4.2.1.13 Extended key usage field ............................. 40 4.2.1.14 CRL Distribution Points .............................. 41 4.2.1.15 Inhibit Any-Policy ................................... 42 4.2.1.16 Freshest CRL ......................................... 43 4.2.2 Internet Certificate Extensions ......................... 43 4.2.2.1 Authority Information Access .......................... 43 5 CRL and CRL Extensions Profile .............................. 45 5.1 CRL Fields ................................................ 45 5.1.1 CertificateList Fields .................................. 46 5.1.1.1 tbsCertList ........................................... 46 5.1.1.2 signatureAlgorithm .................................... 46 5.1.1.3 signatureValue ........................................ 47 5.1.2 Certificate List "To Be Signed" ......................... 47 5.1.2.1 Version ............................................... 47 5.1.2.2 Signature ............................................. 47 5.1.2.3 Issuer Name ........................................... 47 5.1.2.4 This Update ........................................... 48 5.1.2.5 Next Update ........................................... 48 5.1.2.6 Revoked Certificates .................................. 48 5.1.2.7 Extensions ............................................ 49 5.2 CRL Extensions ............................................ 49 5.2.1 Authority Key Identifier ................................ 49 5.2.2 Issuer Alternative Name ................................. 49 5.2.3 CRL Number .............................................. 50 5.2.4 Delta CRL Indicator ..................................... 50 5.2.5 Issuing Distribution Point .............................. 52 5.2.6 Freshest CRL ............................................ 53 5.3 CRL Entry Extensions ...................................... 53 5.3.1 Reason Code ............................................. 53 5.3.2 Hold Instruction Code ................................... 54 5.3.3 Invalidity Date ......................................... 54 5.3.4 Certificate Issuer ...................................... 55 6 Certificate Path Validation ................................. 55 6.1 Basic Path Validation ..................................... 56 6.1.1 Inputs ................................................... 58 6.1.2 Initialization ........................................... 59 6.1.3 Basic Certificate Processing ............................. 62 6.1.4 Preparation for Certificate i+1 .......................... 67 6.1.5 Wrap-up procedure ........................................ 70 6.1.6 Outputs .................................................. 71 6.2 Extending Path Validation ................................. 71 6.3 CRL Validation ............................................ 72 6.3.1 Revocation Inputs ....................................... 72 6.3.2 Initialization and Revocation State Variables ........... 72 6.3.3 CRL Processing .......................................... 73 Housley, Ford, Polk, & Solo [Page 4] INTERNET DRAFT July 14, 2000 7 References .................................................. 75 8 Intellectual Property Rights ................................ 77 9 Security Considerations ..................................... 77 Appendix A. ASN.1 Structures and OIDs ......................... 81 A.1 Explicitly Tagged Module, 1988 Syntax ...................... 81 A.2 Implicitly Tagged Module, 1988 Syntax ...................... 94 Appendix B. ASN.1 Notes ....................................... 101 Appendix C. Examples .......................................... 102 C.1 Certificate ............................................... 103 C.2 Certificate ............................................... 106 C.3 End-Entity Certificate Using RSA .......................... 109 C.4 Certificate Revocation List ............................... 112 Appendix D. Author Addresses .................................. 114 Appendix E. Full Copyright Statement .......................... 114 Housley, Ford, Polk, & Solo [Page 5] INTERNET DRAFT July 14, 2000 1 Introduction This specification is one part of a family of standards for the X.509 Public Key Infrastructure (PKI) for the Internet. This specification is a standalone document; implementations of this standard may proceed independent from the other parts. This specification profiles the format and semantics of certificates and certificate revocation lists for the Internet PKI. Procedures are described for processing of certification paths in the Internet environment. Encoding rules are provided for popular cryptographic algorithms. Finally, ASN.1 modules are provided in the appendices for all data structures defined or referenced. The specification describes the requirements which inspire the crea- tion of this document and the assumptions which affect its scope in Section 2. Section 3 presents an architectural model and describes its relationship to previous IETF and ISO/IEC/ITU standards. In par- ticular, this document's relationship with the IETF PEM specifica- tions and the ISO/IEC/ITU X.509 documents are described. The specification profiles the X.509 version 3 certificate in Section 4, and the X.509 version 2 certificate revocation list (CRL) in Sec- tion 5. The profiles include the identification of ISO/IEC/ITU and ANSI extensions which may be useful in the Internet PKI. The profiles are presented in the 1988 Abstract Syntax Notation One (ASN.1) rather than the 1994 syntax used in the ISO/IEC/ITU standards. This specification also includes path validation procedures in Sec- tion 6. These procedures are based upon the ISO/IEC/ITU definition, but the presentation assumes one or more self-signed trusted CA cer- tificates. Implementations are required to derive the same results but are not required to use the specified procedures. Procedures for identification and encoding of public key materials and digital signatures are defined in [PKIX ALGS]. Implementations of this specification are not required to use any particular crypto- graphic algorithms. However, conforming implementations which use the algorithms identified in [PKIX ALGS] are required to identify and encode the public key materials and digital signatures as described in that specification. Finally, three appendices are provided to aid implementers. Appendix A contains all ASN.1 structures defined or referenced within this specification. As above, the material is presented in the 1988 Abstract Syntax Notation One (ASN.1) rather than the 1994 syntax. Appendix B contains notes on less familiar features of the ASN.1 notation used within this specification. Appendix C contains Housley, Ford, Polk, & Solo [Page 6] INTERNET DRAFT July 14, 2000 examples of a conforming certificate and a conforming CRL. 2 Requirements and Assumptions The goal of this specification is to develop a profile to facilitate the use of X.509 certificates within Internet applications for those communities wishing to make use of X.509 technology. Such applica- tions may include WWW, electronic mail, user authentication, and IPsec. In order to relieve some of the obstacles to using X.509 cer- tificates, this document defines a profile to promote the development of certificate management systems; development of application tools; and interoperability determined by policy. Some communities will need to supplement, or possibly replace, this profile in order to meet the requirements of specialized application domains or environments with additional authorization, assurance, or operational requirements. However, for basic applications, common representations of frequently used attributes are defined so that application developers can obtain necessary information without regard to the issuer of a particular certificate or certificate revo- cation list (CRL). A certificate user should review the certificate policy generated by the certification authority (CA) before relying on the authentication or non-repudiation services associated with the public key in a par- ticular certificate. To this end, this standard does not prescribe legally binding rules or duties. As supplemental authorization and attribute management tools emerge, such as attribute certificates, it may be appropriate to limit the authenticated attributes that are included in a certificate. These other management tools may provide more appropriate methods of con- veying many authenticated attributes. 2.1 Communication and Topology The users of certificates will operate in a wide range of environ- ments with respect to their communication topology, especially users of secure electronic mail. This profile supports users without high bandwidth, real-time IP connectivity, or high connection availabil- ity. In addition, the profile allows for the presence of firewall or other filtered communication. 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, but other means of distributing certificates and certificate revoca- tion lists (CRLs) may be used. Housley, Ford, Polk, & Solo [Page 7] INTERNET DRAFT July 14, 2000 2.2 Acceptability Criteria The goal of the Internet Public Key Infrastructure (PKI) is to meet the needs of deterministic, automated identification, authentication, access control, and authorization functions. Support for these ser- vices determines the attributes contained in the certificate as well as the ancillary control information in the certificate such as pol- icy data and certification path constraints. 2.3 User Expectations Users of the Internet PKI are people and processes who use client software and are the subjects named in certificates. These uses include readers and writers of electronic mail, the clients for WWW browsers, WWW servers, and the key manager for IPsec within a router. This profile recognizes the limitations of the platforms these users employ and the limitations in sophistication and attentiveness of the users themselves. This manifests itself in minimal user configura- tion responsibility (e.g., trusted CA keys, rules), explicit platform usage constraints within the certificate, certification path con- straints which shield the user from many malicious actions, and applications which sensibly automate validation functions. 2.4 Administrator Expectations As with user expectations, the Internet PKI profile is structured to support the individuals who generally operate CAs. Providing administrators with unbounded choices increases the chances that a subtle CA administrator mistake will result in broad compromise. Also, unbounded choices greatly complicate the software that shall process and validate the certificates created by the CA. 3 Overview of Approach Following is a simplified view of the architectural model assumed by the PKIX specifications. Housley, Ford, Polk, & Solo [Page 8] INTERNET DRAFT July 14, 2000 +---+ | C | +------------+ | e | <-------------------->| End entity | | r | Operational +------------+ | t | transactions ^ | | and management | Management | / | transactions | transactions | | | PKI users | C | v | R | -------------------+--+-----------+---------------- | L | ^ ^ | | | | PKI management | | v | entities | R | +------+ | | e | <---------------------| RA | <---+ | | p | Publish certificate +------+ | | | o | | | | s | | | | I | v v | t | +------------+ | o | <------------------------------| CA | | r | Publish certificate +------------+ | y | Publish CRL ^ | | | +---+ Management | transactions | v +------+ | CA | +------+ Figure 1 - PKI Entities The components in this model are: end entity: user of PKI certificates and/or end user system that is the subject of a certificate; CA: certification authority; RA: registration authority, i.e., an optional system to which a CA delegates certain management functions; repository: a system or collection of distributed systems that store certificates and CRLs and serves as a means of distributing these certificates and CRLs to end entities. Housley, Ford, Polk, & Solo [Page 9] INTERNET DRAFT July 14, 2000 3.1 X.509 Version 3 Certificate Users of a public key require confidence that the associated private key is owned by the correct remote subject (person or system) with which an encryption or digital signature mechanism will be used. This confidence is obtained through the use of public key certifi- cates, which are data structures that bind public key values to sub- jects. The binding is asserted by having a trusted CA digitally sign each certificate. The CA may base this assertion upon technical means (a.k.a., proof of posession through a challenge-response protocol), presentation of the private key, or on an assertion by the subject. A certificate has a limited valid lifetime which is indicated in its signed contents. Because a certificate's signature and timeliness can be independently checked by a certificate-using client, certifi- cates can be distributed via untrusted communications and server sys- tems, and can be cached in unsecured storage in certificate-using systems. 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- tions, defines a standard certificate format [X.509]. The certificate format in the 1988 standard is called the version 1 (v1) format. When X.500 was revised in 1993, two more fields were added, resulting in the version 2 (v2) format. The Internet Privacy Enhanced Mail (PEM) RFCs, published in 1993, include specifications for a public key infrastructure based on X.509 v1 certificates [RFC 1422]. The experience gained in attempts to deploy RFC 1422 made it clear that the v1 and v2 certificate formats are deficient in several respects. Most importantly, more fields were needed to carry information which PEM design and implementation experience has proven necessary. In response to these new require- ments, ISO/IEC/ITU and ANSI X9 developed the X.509 version 3 (v3) certificate format. The v3 format extends the v2 format by adding provision for additional extension fields. Particular extension field types may be specified in standards or may be defined and registered by any organization or community. In June 1996, standardi- zation of the basic v3 format was completed [X.509]. 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 convey such data as additional subject identification information, key attribute information, policy information, and certification path constraints. However, the ISO/IEC/ITU and ANSI X9 standard extensions are very broad in their applicability. In order to develop interoperable implementations of X.509 v3 systems for Internet use, it is necessary Housley, Ford, Polk, & Solo [Page 10] INTERNET DRAFT July 14, 2000 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 for Internet WWW, electronic mail, and IPsec applications. Environ- ments with additional requirements may build on this profile or may replace it. 3.2 Certification Paths and Trust A user of a security service requiring knowledge of a public key gen- erally needs to obtain and validate a certificate containing the 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, the CA's name, and related information (such as the validity period or name constraints), then it might need an additional certificate to obtain that public key. In general, a chain of multiple certificates may be needed, comprising a certificate of the public key owner (the end entity) signed by one CA, and zero or more additional certifi- cates of CAs signed by other CAs. Such chains, called certification paths, are required because a public key user is only initialized with a limited number of assured CA public keys. There are different ways in which CAs might be configured in order for public key users to be able to find certification paths. For PEM, RFC 1422 defined a rigid hierarchical structure of CAs. There are three types of PEM certification authority: (a) Internet Policy Registration Authority (IPRA): This author- ity, operated under the auspices of the Internet Society, acts as the root of the PEM certification hierarchy at level 1. It issues certificates only for the next level of authorities, PCAs. All certification paths start with the IPRA. (b) Policy Certification Authorities (PCAs): PCAs are at level 2 of the hierarchy, each PCA being certified by the IPRA. A PCA shall establish and publish a statement of its policy with respect to certifying users or subordinate certification authorities. Distinct PCAs aim to satisfy different user needs. For example, one PCA (an organizational PCA) might support the general elec- tronic mail needs of commercial organizations, and another PCA (a high-assurance PCA) might have a more stringent policy designed for satisfying legally binding digital signature requirements. (c) Certification Authorities (CAs): CAs are at level 3 of the hierarchy and can also be at lower levels. Those at level 3 are certified by PCAs. CAs represent, for example, particular organi- zations, particular organizational units (e.g., departments, groups, sections), or particular geographical areas. Housley, Ford, Polk, & Solo [Page 11] INTERNET DRAFT July 14, 2000 RFC 1422 furthermore has a name subordination rule which requires 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. The trust associated with a PEM certification path is implied by the PCA name. The name subordination rule ensures that CAs below the PCA are sensibly constrained as to the set of subordinate entities they can certify (e.g., a CA for an organization can only certify entities in that organization's name tree). Certificate user systems are able to mechanically check that the name subordination rule has been fol- lowed. The RFC 1422 uses the X.509 v1 certificate formats. The limitations of X.509 v1 required imposition of several structural restrictions to clearly associate policy information or restrict the utility of cer- tificates. These restrictions included: (a) a pure top-down hierarchy, with all certification paths start- ing from IPRA; (b) a naming subordination rule restricting the names of a CA's subjects; and (c) use of the PCA concept, which requires knowledge of individual PCAs to be built into certificate chain verification logic. Knowledge of individual PCAs was required to determine if a chain could be accepted. With X.509 v3, most of the requirements addressed by RFC 1422 can be addressed using certificate extensions, without a need to restrict the CA structures used. In particular, the certificate extensions relating to certificate policies obviate the need for PCAs and the constraint extensions obviate the need for the name subordination rule. As a result, this document supports a more flexible architec- ture, including: (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- chy. Starting with the public key of a CA in a user's own domain has certain advantages. In some environments, the local domain is the most trusted. (b) Name constraints may be imposed through explicit inclusion of a name constraints extension in a certificate, but are not required. (c) Policy extensions and policy mappings replace the PCA con- cept, which permits a greater degree of automation. The applica- tion can determine if the certification path is acceptable based Housley, Ford, Polk, & Solo [Page 12] INTERNET DRAFT July 14, 2000 on the contents of the certificates instead of a priori knowledge of PCAs. This permits automation of certificate chain processing. 3.3 Revocation When a certificate is issued, it is expected to be in use for its entire validity period. However, various circumstances may cause a certificate to become invalid prior to the expiration of the validity period. Such circumstances include change of name, change of associa- tion between subject and CA (e.g., an employee terminates employment with an organization), and compromise or suspected compromise of the corresponding private key. Under such circumstances, the CA needs to revoke the certificate. X.509 defines one method of certificate revocation. This method involves each CA periodically issuing a signed data structure called a certificate revocation list (CRL). A CRL is a time stamped list identifying revoked certificates which is signed by a CA and made freely available in a public repository. Each revoked certificate is identified in a CRL by its certificate serial number. When a certificate-using system uses a certificate (e.g., for verifying a remote user's digital signature), that system not only checks the certificate signature and validity but also acquires a suitably- recent CRL and checks that the certificate serial number is not on that CRL. The meaning of "suitably-recent" may vary with local pol- icy, but it usually means the most recently-issued CRL. A CA 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 following notification of revocation. An entry may be removed from the CRL after appearing on one regularly scheduled CRL issued beyond the revoked certificate's validity period. An advantage of this revocation method is that CRLs may be distri- buted by exactly the same means as certificates themselves, namely, via untrusted communications and server systems. One limitation of the CRL revocation method, using untrusted communi- cations and servers, is that the time granularity of revocation is limited to the CRL issue period. For example, if a revocation is reported now, that revocation will not be reliably notified to certificate-using systems until the next periodic CRL is issued -- this may be up to one hour, one day, or one week depending on the frequency that the CA issues CRLs. As with the X.509 v3 certificate format, in order to facilitate interoperable implementations from multiple vendors, the X.509 v2 CRL format needs to be profiled for Internet use. It is one goal of this document to specify that profile. However, this profile does not Housley, Ford, Polk, & Solo [Page 13] INTERNET DRAFT July 14, 2000 require CAs to issue CRLs. Message formats and protocols supporting on-line revocation notification may be defined in other PKIX specifi- cations. On-line methods of revocation notification may be applica- ble in some environments as an alternative to the X.509 CRL. On-line revocation checking may significantly reduce the latency between a revocation report and the distribution of the information to relying parties. Once the CA accepts the report as authentic and valid, any query to the on-line service will correctly reflect the certificate validation impacts of the revocation. However, these methods impose new security requirements: the certificate validator needs to trust the on-line validation service while the repository does not need to be trusted. 3.4 Operational Protocols Operational protocols are required to deliver certificates and CRLs (or status information) to certificate using client systems. Provi- sion is needed for a variety of different means of certificate and CRL delivery, including distribution procedures based on LDAP, HTTP, FTP, and X.500. Operational protocols supporting these functions are defined in other PKIX specifications. These specifications may include definitions of message formats and procedures for supporting all of the above operational environments, including definitions of or references to appropriate MIME content types. 3.5 Management Protocols Management protocols are required to support on-line interactions between PKI user and management entities. For example, a management 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 other. The set of functions which potentially need to be supported by management protocols include: (a) registration: This is the process whereby a user first makes itself known to a CA (directly, or through an RA), prior to that CA issuing a certificate or certificates for that user. (b) initialization: Before a client system can operate securely it is necessary to install key materials which have the appropri- ate relationship with keys stored elsewhere in the infrastructure. For example, the client needs to be securely initialized with the public key and other assured information of the trusted CA(s), to be used in validating certificate paths. 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 certificate for a user's public key, and returns that certificate Housley, Ford, Polk, & Solo [Page 14] INTERNET DRAFT July 14, 2000 to the user's client system and/or posts that certificate in a repository. (d) key pair recovery: As an option, user client key materials (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 recover these backed up key materials (e.g., as a result of a for- gotten password or a lost key chain file), an on-line protocol exchange may be needed to support such recovery. (e) key pair update: All key pairs need to be updated regularly, i.e., replaced with a new key pair, and new certificates issued. (f) revocation request: An authorized person advises a CA of an abnormal situation requiring certificate revocation. (g) cross-certification: Two CAs exchange information used in establishing a cross-certificate. A cross-certificate is a certi- ficate issued by one CA to another CA which contains a CA signa- ture key used for issuing certificates. Note that on-line protocols are not the only way of implementing the above functions. For all functions there are off-line methods of achieving the same result, and this specification does not mandate use of on-line protocols. For example, when hardware tokens are used, many of the functions may be achieved as part of the physical token delivery. Furthermore, some of the above functions may be com- bined into one protocol exchange. In particular, two or more of the registration, initialization, and certification functions can be com- bined into one protocol exchange. The PKIX series of specifications may define a set of standard mes- sage formats supporting the above functions in future specifications. In that case, the protocols for conveying these messages in different environments (e.g., on-line, file transfer, e-mail, and WWW) will also be described in those specifications. 4 Certificate and Certificate Extensions Profile This section presents a profile for public key certificates that will foster interoperability and a reusable PKI. This section is based upon the X.509 v3 certificate format and the standard certificate 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- tax, the encoded certificate and standard extensions are equivalent. This section also defines private extensions required to support a PKI for the Internet community. Housley, Ford, Polk, & Solo [Page 15] INTERNET DRAFT July 14, 2000 Certificates may be used in a wide range of applications and environ- ments covering a broad spectrum of interoperability goals and a broader spectrum of operational and assurance requirements. The goal of this document is to establish a common baseline for generic appli- cations requiring broad interoperability and limited special purpose requirements. In particular, the emphasis will be on supporting the use of X.509 v3 certificates for informal Internet electronic mail, IPsec, and WWW applications. 4.1 Basic Certificate Fields The X.509 v3 certificate basic syntax is as follows. For signature calculation, the certificate is encoded using the ASN.1 distinguished encoding rules (DER) [X.208]. ASN.1 DER encoding is a tag, length, value encoding system for each element. Certificate ::= SEQUENCE { tbsCertificate TBSCertificate, signatureAlgorithm AlgorithmIdentifier, signatureValue BIT STRING } TBSCertificate ::= SEQUENCE { version [0] EXPLICIT Version DEFAULT v1, serialNumber CertificateSerialNumber, signature AlgorithmIdentifier, issuer Name, validity Validity, subject Name, subjectPublicKeyInfo SubjectPublicKeyInfo, issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL, -- If present, version shall be v2 or v3 subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL, -- If present, version shall be v2 or v3 extensions [3] EXPLICIT Extensions OPTIONAL -- If present, version shall be v3 } Version ::= INTEGER { v1(0), v2(1), v3(2) } CertificateSerialNumber ::= INTEGER Validity ::= SEQUENCE { notBefore Time, notAfter Time } Time ::= CHOICE { utcTime UTCTime, generalTime GeneralizedTime } Housley, Ford, Polk, & Solo [Page 16] INTERNET DRAFT July 14, 2000 UniqueIdentifier ::= BIT STRING SubjectPublicKeyInfo ::= SEQUENCE { algorithm AlgorithmIdentifier, subjectPublicKey BIT STRING } Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension Extension ::= SEQUENCE { extnID OBJECT IDENTIFIER, critical BOOLEAN DEFAULT FALSE, extnValue OCTET STRING } The following items describe the X.509 v3 certificate for use in the Internet. 4.1.1 Certificate Fields The Certificate is a SEQUENCE of three required fields. The fields are described in detail in the following subsections. 4.1.1.1 tbsCertificate The field contains the names of the subject and issuer, a public key associated with the subject, a validity period, and other associated information. The fields are described in detail in section 4.1.2; the tbscertificate may also include extensions which are described in section 4.2. 4.1.1.2 signatureAlgorithm The signatureAlgorithm field contains the identifier for the crypto- graphic algorithm used by the CA to sign this certificate. [PKIX ALGS] lists the supported signature algorithms. An algorithm identifier is defined by the following ASN.1 structure: AlgorithmIdentifier ::= SEQUENCE { algorithm OBJECT IDENTIFIER, parameters ANY DEFINED BY algorithm OPTIONAL } The algorithm identifier is used to identify a cryptographic algo- rithm. The OBJECT IDENTIFIER component identifies the algorithm (such as DSA with SHA-1). The contents of the optional parameters field will vary according to the algorithm identified. [PKIX ALGS] lists the supported algorithms for this specification. This field MUST contain the same algorithm identifier as the Housley, Ford, Polk, & Solo [Page 17] INTERNET DRAFT July 14, 2000 signature field in the sequence tbsCertificate (see sec. 4.1.2.3). 4.1.1.3 signatureValue The signatureValue field contains a digital signature computed upon the ASN.1 DER encoded tbsCertificate. The ASN.1 DER encoded tbsCer- tificate is used as the input to the signature function. This signa- ture value is then ASN.1 encoded as a BIT STRING and included in the Certificate's signature field. The details of this process are speci- fied for each of the supported algorithms in [PKIX ALGS]. By generating this signature, a CA certifies the validity of the information in the tbsCertificate field. In particular, the CA cer- tifies the binding between the public key material and the subject of the certificate. 4.1.2 TBSCertificate The sequence TBSCertificate contains information associated with the subject of the certificate and the CA who issued it. Every TBSCerti- ficate contains the names of the subject and issuer, a public key associated with the subject, a validity period, a version number, and a serial number; some may contain optional unique identifier fields. The remainder of this section describes the syntax and semantics of these fields. A TBSCertificate may also include extensions. Exten- sions for the Internet PKI are described in Section 4.2. 4.1.2.1 Version This field describes the version of the encoded certificate. When extensions are used, as expected in this profile, use X.509 version 3 (value is 2). If no extensions are present, but a UniqueIdentifier 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 the default value). Implementations SHOULD be prepared to accept any version certificate. At a minimum, conforming implementations MUST recognize version 3 certificates. Generation of version 2 certificates is not expected by implementa- tions based on this profile. 4.1.2.2 Serial number The serial number is a positive integer assigned by the CA to each certificate. It MUST be unique for each certificate issued by a given CA (i.e., the issuer name and serial number identify a unique Housley, Ford, Polk, & Solo [Page 18] INTERNET DRAFT July 14, 2000 certificate). 4.1.2.3 Signature This field contains the algorithm identifier for the algorithm used by the CA to sign the certificate. This field MUST contain the same algorithm identifier as the signa- tureAlgorithm field in the sequence Certificate (see sec. 4.1.1.2). The contents of the optional parameters field will vary according to the algorithm identified. [PKIX ALGS] lists the supported signature algorithms. 4.1.2.4 Issuer The issuer field identifies the entity who has signed and issued the certificate. The issuer field MUST contain a non-empty distinguished name (DN). The issuer field is defined as the X.501 type Name. [X.501] Name is defined by the following ASN.1 structures: Name ::= CHOICE { RDNSequence } RDNSequence ::= SEQUENCE OF RelativeDistinguishedName RelativeDistinguishedName ::= SET OF AttributeTypeAndValue AttributeTypeAndValue ::= SEQUENCE { type AttributeType, value AttributeValue } AttributeType ::= OBJECT IDENTIFIER AttributeValue ::= ANY DEFINED BY AttributeType DirectoryString ::= CHOICE { teletexString TeletexString (SIZE (1..MAX)), printableString PrintableString (SIZE (1..MAX)), universalString UniversalString (SIZE (1..MAX)), utf8String UTF8String (SIZE (1.. MAX)), bmpString BMPString (SIZE (1..MAX)) } The Name describes a hierarchical name composed of attributes, such as country name, and corresponding values, such as US. The type of the component AttributeValue is determined by the AttributeType; in general it will be a DirectoryString. Housley, Ford, Polk, & Solo [Page 19] INTERNET DRAFT July 14, 2000 The DirectoryString type is defined as a choice of PrintableString, TeletexString, BMPString, UTF8String, and UniversalString. The UTF8String encoding is the preferred encoding, and all certificates issued after December 31, 2003 MUST use the UTF8String encoding of DirectoryString (except as noted below). Until that date, conforming CAs MUST choose from the following options when creating a dis- tinguished name, including their own: (a) if the character set is sufficient, the string MAY be represented as a PrintableString; (b) failing (a), if the BMPString character set is sufficient the string MAY be represented as a BMPString; and (c) failing (a) and (b), the string MUST be represented as a UTF8String. If (a) or (b) is satisfied, the CA MAY still choose to represent the string as a UTF8String. Exceptions to the December 31, 2003 UTF8 encoding requirements are as follows: (a) CAs MAY issue "name rollover" certificates to support an ord- erly migration to UTF8String encoding. Such certificates would include the CA's UTF8String encoded name as issuer and and the old name encoding as subject, or vice-versa. (b) As stated in section 4.1.2.6, the subject field MUST be popu- lated with a non-empty distinguished name matching the contents of the issuer field in all certificates issued by the subject CA regardless of encoding. The TeletexString and UniversalString are included for backward com- patibility, and should not be used for certificates for new subjects. However, these types may be used in certificates where the name was previously established. Certificate users SHOULD be prepared to receive certificates with these types. In addition, many legacy implementations support names encoded in the ISO 8859-1 character set (Latin1String) but tag them as Teletex- String. The Latin1String includes characters used in Western Euro- pean countries which are not part of the TeletexString charcter set. Implementations that process TeletexString SHOULD be prepared to han- dle the entire ISO 8859-1 character set.[ISO 8859-1] As noted above, distinguished names are composed of attributes. This specification does not restrict the set of attribute types that may appear in names. However, conforming implementations MUST be prepared to receive certificates with issuer names containing the set Housley, Ford, Polk, & Solo [Page 20] INTERNET DRAFT July 14, 2000 of attribute types defined below. This specification also recommends support for additional attribute types. Standard sets of attributes have been defined in the X.500 series of specifications.[X.520] Implementations of this specification MUST be prepared to receive the following standard attribute types in issuer and subject (see 4.1.2.6) names: * country, * organization, * organizational-unit, * distinguished name qualifier, * state or province name, * common name (e.g., "Susan Housley"), and * serial number. In addition, implementations of this specification SHOULD be prepared to receive the following standard attribute types in issuer and sub- ject names: * locality, * title, * surname, * given name, * initials, and * generation qualifier (e.g., "Jr.", "3rd", or "IV"). The syntax and associated object identifiers (OIDs) for these attri- bute types are provided in the ASN.1 modules in Appendices A and B. In addition, implementations of this specification MUST be prepared to receive the domainComponent attribute, as defined in [RFC 2247]. The Domain (Nameserver) System (DNS) provides a hierarchical resource labeling system. This attribute provides is a convenient mechanism for organizations that wish to use DNs that parallel their DNS names. This is not a replacement for the dNSName component of the alterna- tive name field. Implementations are not required to convert such names into DNS names. The syntax and associated OID for this attri- bute type is provided in the ASN.1 modules in Appendices A and B. Certificate users MUST be prepared to process the issuer dis- tinguished name and subject distinguished name (see sec. 4.1.2.6) fields to perform name chaining for certification path validation (see section 6). Name chaining is performed by matching the issuer distinguished name in one certificate with the subject name in a CA certificate. This specification requires only a subset of the name comparison Housley, Ford, Polk, & Solo [Page 21] INTERNET DRAFT July 14, 2000 functionality specified in the X.500 series of specifications. The requirements for conforming implementations are as follows: (a) attribute values encoded in different types (e.g., Printable- String and BMPString) may be assumed to represent different strings; (b) attribute values in types other than PrintableString are case sensitive (this permits matching of attribute values as binary objects); (c) attribute values in PrintableString are not case sensitive (e.g., "Marianne Swanson" is the same as "MARIANNE SWANSON"); and (d) attribute values in PrintableString are compared after remov- ing leading and trailing white space and converting internal sub- strings of one or more consecutive white space characters to a single space. These name comparison rules permit a certificate user to validate certificates issued using languages or encodings unfamiliar to the certificate user. In addition, implementations of this specification MAY use these com- parison rules to process unfamiliar attribute types for name chain- ing. This allows implementations to process certificates with unfami- liar attributes in the issuer name. Note that the comparison rules defined in the X.500 series of specif- ications indicate that the character sets used to encode data in dis- tinguished names are irrelevant. The characters themselves are com- pared without regard to encoding. Implementations of the profile are permitted to use the comparison algorithm defined in the X.500 series. Such an implementation will recognize a superset of name matches recognized by the algorithm specified above. 4.1.2.5 Validity The certificate validity period is the time interval during which the CA warrants that it will maintain information about the status of the certificate. The field is represented as a SEQUENCE of two dates: the date on which the certificate validity period begins (notBefore) and the date on which the certificate validity period ends (notAfter). Both notBefore and notAfter may be encoded as UTCTime or GeneralizedTime. CAs conforming to this profile MUST always encode certificate vali- dity dates through the year 2049 as UTCTime; certificate validity Housley, Ford, Polk, & Solo [Page 22] INTERNET DRAFT July 14, 2000 dates in 2050 or later MUST be encoded as GeneralizedTime. The validity period for a certificate is the period of time from notBefore through notAfter, inclusive. 4.1.2.5.1 UTCTime The universal time type, UTCTime, is a standard ASN.1 type intended for representation of dates and time. UTCTime specifies the year through the two low order digits and time is specified to the preci- sion of one minute or one second. UTCTime includes either Z (for Zulu, or Greenwich Mean Time) or a time differential. For the purposes of this profile, UTCTime values MUST be expressed Greenwich Mean Time (Zulu) and MUST include seconds (i.e., times are YYMMDDHHMMSSZ), even where the number of seconds is zero. Conforming systems MUST interpret the year field (YY) as follows: Where YY is greater than or equal to 50, the year shall be inter- preted as 19YY; and Where YY is less than 50, the year shall be interpreted as 20YY. 4.1.2.5.2 GeneralizedTime The generalized time type, GeneralizedTime, is a standard ASN.1 type for variable precision representation of time. Optionally, the Gen- eralizedTime field can include a representation of the time differen- tial between local and Greenwich Mean Time. For the purposes of this profile, GeneralizedTime values MUST be expressed Greenwich Mean Time (Zulu) and MUST include seconds (i.e., times are YYYYMMDDHHMMSSZ), even where the number of seconds is zero. GeneralizedTime values MUST NOT include fractional seconds. 4.1.2.6 Subject The subject field identifies the entity associated with the public key stored in the subject public key field. The subject name may be carried in the subject field and/or the subjectAltName extension. If the subject is a CA (e.g., the basic constraints extension, as dis- cussed in 4.2.1.10, is present and the value of cA is TRUE,) then the subject field MUST be populated with a non-empty distinguished name matching the contents of the issuer field (see sec. 4.1.2.4) in all certificates issued by the subject CA. If subject naming information is present only in the subjectAltName extension (e.g., a key bound only to an email address or URI), then the subject name MUST be an empty sequence and the subjectAltName extension MUST be critical. Housley, Ford, Polk, & Solo [Page 23] INTERNET DRAFT July 14, 2000 Where it is non-empty, the subject field MUST contain an X.500 dis- tinguished name (DN). 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 certificate with the same DN to the same subject entity. The subject name field is defined as the X.501 type Name. Implemen- tation requirements for this field are those defined for the issuer field (see sec. 4.1.2.4). When encoding attribute values of type DirectoryString, the encoding rules for the issuer field MUST be implemented. Implementations of this specification MUST be prepared to receive subject names containing the attribute types required for the issuer field. Implementations of this specification SHOULD be prepared to receive subject names containing the recommended attri- bute types for the issuer field. The syntax and associated object identifiers (OIDs) for these attribute types are provided in the ASN.1 modules in Appendices A and B. Implementations of this specif- ication MAY use these comparison rules to process unfamiliar attri- bute types (i.e., for name chaining). This allows implementations to process certificates with unfamiliar attributes in the subject name. In addition, legacy implementations exist where an RFC 822 name is embedded in the subject distinguished name as an EmailAddress attri- bute. The attribute value for EmailAddress is of type IA5String to permit inclusion of the character '@', which is not part of the PrintableString character set. EmailAddress attribute values are not case sensitive (e.g., "fanfeedback@redsox.com" is the same as "FANFEEDBACK@REDSOX.COM"). Conforming implementations generating new certificates with elec- tronic mail addresses MUST use the rfc822Name in the subject alterna- tive name field (see sec. 4.2.1.7) to describe such identities. Simultaneous inclusion of the EmailAddress attribute in the subject distinguished name to support legacy implementations is deprecated but permitted. 4.1.2.7 Subject Public Key Info 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 AlgorithmIdentifier structure specified in section 4.1.1.2. The object identifiers for the supported algorithms and the methods for encoding the public key materials (public key and parameters) are specified in [PKIX ALGS]. Housley, Ford, Polk, & Solo [Page 24] INTERNET DRAFT July 14, 2000 4.1.2.8 Unique Identifiers 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 the certificate to handle the possibility of reuse of subject and/or issuer names over time. This profile recommends that names not be reused for different entities and that Internet certificates not make use of unique identifiers. CAs conforming to this profile SHOULD NOT generate certificates with unique identifiers. Applications conform- ing to this profile SHOULD be capable of parsing unique identifiers and making comparisons. 4.1.2.9 Extensions 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 extensions. The format and content of certificate extensions in the Internet PKI is defined in section 4.2. 4.2 Standard Certificate Extensions The extensions defined for X.509 v3 certificates provide methods for associating additional attributes with users or public keys and for managing the certification hierarchy. The X.509 v3 certificate for- mat also allows communities to define private extensions to carry information unique to those communities. Each extension in a certi- ficate may be designated as critical or non-critical. A certificate using system MUST reject the certificate if it encounters a critical extension it does not recognize; however, a non-critical extension may be ignored if it is not recognized. The following sections present recommended extensions used within Internet certificates and standard locations for information. Communities may elect to use additional extensions; however, caution should be exercised in adopt- ing any critical extensions in certificates which might prevent use in a general context. Each extension includes an OID and an ASN.1 structure. When an extension appears in a certificate, the OID appears as the field extnID and the corresponding ASN.1 encoded structure is the value of the octet string extnValue. Only one instance of a particular exten- sion may appear in a particular certificate. For example, a certifi- cate may contain only one authority key identifier extension (see sec. 4.2.1.1). An extension includes the boolean critical, with a default value of FALSE. The text for each extension specifies the acceptable values for the critical field. 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. Housley, Ford, Polk, & Solo [Page 25] INTERNET DRAFT July 14, 2000 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 field, the CA MUST support the subject alternative name extension (see sec. 4.2.1.7). Support for the remaining extensions is OPTIONAL. Conforming CAs may support extensions that are not identi- fied within this specification; certificate issuers are cautioned that marking such extensions as critical may inhibit interoperabil- ity. At a minimum, applications conforming to this profile MUST recognize 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. 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 extended key usage (see sec. 4.2.1.13). 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), and inhibit any-policy (see sec. 4.2.1.15) extensions. 4.2.1 Standard Extensions This section identifies standard certificate extensions defined in [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 arc, which is defined by the following: id-ce OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29} 4.2.1.1 Authority Key Identifier The authority key identifier extension provides a means of identify- ing the public key corresponding to the private key used to sign a certificate. This extension is used where an issuer has multiple signing keys (either due to multiple concurrent key pairs or due to changeover). The identification may be based on either the key iden- tifier (the subject key identifier in the issuer's certificate) or on the issuer name and serial number. The keyIdentifier field of the authorityKeyIdentifier extension MUST be included in all certificates generated by conforming CAs to facil- itate chain building. There is one exception; where a CA distributes its public key in the form of a "self-signed" certificate, the authority key identifier may be omitted. In this case, the subject and authority key identifiers would be identical. The value of the keyIdentifier field SHOULD be derived from the pub- lic key used to verify the certificate's signature or a method that Housley, Ford, Polk, & Solo [Page 26] INTERNET DRAFT July 14, 2000 generates unique values. Two common methods for generating key iden- tifiers from the public key are described in (sec. 4.2.1.2). One com- mon method for generating unique values is described in (sec. 4.2.1.2). Where a key identifier has not been previously esta- blished, this specification recommends use of one of these methods for generating keyIdentifiers. This profile recommends support for the key identifier method by all certificate users. This extension MUST NOT be marked critical. id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 35 } AuthorityKeyIdentifier ::= SEQUENCE { keyIdentifier [0] KeyIdentifier OPTIONAL, authorityCertIssuer [1] GeneralNames OPTIONAL, authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL } KeyIdentifier ::= OCTET STRING 4.2.1.2 Subject Key Identifier The subject key identifier extension provides a means of identifying certificates that contain a particular public key. To facilitate chain building, this extension MUST appear in all con- forming CA certificates, that is, all certificates including the basic constraints extension (see sec. 4.2.1.10) where the value of cA is TRUE. The value of the subject key identifier MUST be the value placed in the key identifier field of the Authority Key Identifier extension (see sec. 4.2.1.1) of certificates issued by the subject of this certificate. For CA certificates, subject key identifiers SHOULD be derived from the public key or a method that generates unique values. Two common methods for generating key identifiers from the public key are: (1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the value of the BIT STRING subjectPublicKey (excluding the tag, length, and number of unused bits). (2) The keyIdentifier is composed of a four bit type field with the value 0100 followed by the least significant 60 bits of the SHA-1 hash of the value of the BIT STRING subjectPublicKey. One common method for generating unique values is a monotomically increasing sequence of integers. Housley, Ford, Polk, & Solo [Page 27] INTERNET DRAFT July 14, 2000 For end entity certificates, the subject key identifier extension provides a means for identifying certificates containing the particu- lar public key used in an application. Where an end entity has obtained multiple certificates, especially from multiple CAs, the subject key identifier provides a means to quickly identify the set of certificates containing a particular public key. To assist appli- cations in identificiation the appropriate end entity certificate, this extension SHOULD be included in all end entity certificates. For end entity certificates, subject key identifiers SHOULD be derived from the public key. Two common methods for generating key identifiers from the public key are identifed above. Where a key identifier has not been previously established, this specification recommends use of one of these methods for generating keyIdentifiers. This extension MUST NOT be marked critical. id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 14 } SubjectKeyIdentifier ::= KeyIdentifier 4.2.1.3 Key Usage The key usage extension defines the purpose (e.g., encipherment, sig- nature, certificate signing) of the key contained in the certificate. The usage restriction might be employed when a key that could be used for more than one operation is to be restricted. For example, when an RSA key should be used only for signing, the digitalSignature and/or nonRepudiation bits would be asserted. Likewise, when an RSA key should be used only for key management, the keyEncipherment bit would be asserted. When used, this extension SHOULD be marked criti- cal. id-ce-keyUsage OBJECT IDENTIFIER ::= { id-ce 15 } KeyUsage ::= BIT STRING { digitalSignature (0), nonRepudiation (1), keyEncipherment (2), dataEncipherment (3), keyAgreement (4), keyCertSign (5), cRLSign (6), encipherOnly (7), decipherOnly (8) } Housley, Ford, Polk, & Solo [Page 28] INTERNET DRAFT July 14, 2000 Bits in the KeyUsage type are used as follows: The digitalSignature bit is asserted when the subject public key is used with a digital signature mechanism to support security services other than non-repudiation (bit 1), certificate signing (bit 5), or revocation information signing (bit 6). Digital signa- ture mechanisms are often used for entity authentication and data origin authentication with integrity. The nonRepudiation bit is asserted when the subject public key is used to verify digital signatures used to provide a non- repudiation service which protects against the signing entity falsely denying some action, excluding certificate or CRL signing. In the case of later conflict, a reliable third party may deter- mine the authenticity of the signed data. Further distinctions between the digitalSignature and nonRepudia- tion bits may be provided in specific certificate policies. 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 management, then this bit shall asserted. The dataEncipherment bit is asserted when the subject public key is used for enciphering user data, other than cryptographic keys. The keyAgreement bit is asserted when the subject public key is used for key agreement. For example, when a Diffie-Hellman key is to be used for key management, then this bit shall asserted. The keyCertSign bit is asserted when the subject public key is used for verifying a signature on certificates. This bit may only be asserted in CA certificates. If the keyCertSign bit is asserted, then the cA bit in the basic constraints extension (see 4.2.1.10) MUST also be asserted. If the keyCertSign bit is not asserted, then the cA bit in the basic constraints extension MUST NOT be asserted. The cRLSign bit is asserted when the subject public key is used for verifying a signature on revocation information (e.g., a CRL). The meaning of the encipherOnly bit is undefined in the absence of the keyAgreement bit. When the encipherOnly bit is asserted and the keyAgreement bit is also set, the subject public key may be used only for enciphering data while performing key agreement. The meaning of the decipherOnly bit is undefined in the absence of the keyAgreement bit. When the decipherOnly bit is asserted and Housley, Ford, Polk, & Solo [Page 29] INTERNET DRAFT July 14, 2000 the keyAgreement bit is also set, the subject public key may be used only for deciphering data while performing key agreement. This profile does not restrict the combinations of bits that may be set in an instantiation of the keyUsage extension. However, appropriate values for keyUsage extensions for particular algorithms are specified in [PKIX ALGS]. 4.2.1.4 Private Key Usage Period This profile recommends against the use of this extension. CAs con- forming to this profile MUST NOT generate certificates with critical private key usage period extensions. The private key usage period extension allows the certificate issuer to specify a different validity period for the private key than the certificate. This extension is intended for use with digital signa- ture keys. This extension consists of two optional components, notBefore and notAfter. The private key associated with the certifi- cate should not be used to sign objects before or after the times specified by the two components, respectively. CAs conforming to this profile MUST NOT generate certificates with private key usage period extensions unless at least one of the two components is present. Where used, notBefore and notAfter are represented as GeneralizedTime and MUST be specified and interpreted as defined in section 4.1.2.5.2. id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= { id-ce 16 } PrivateKeyUsagePeriod ::= SEQUENCE { notBefore [0] GeneralizedTime OPTIONAL, notAfter [1] GeneralizedTime OPTIONAL } 4.2.1.5 Certificate Policies The certificate policies extension contains a sequence of one or more policy information terms, each of which consists of an object iden- tifier (OID) and optional qualifiers. Optional qualifiers, which may be present, are not expected to change the definition of the policy. In an end-entity certificate, these policy information terms indicate the policy under which the certificate has been issued and the pur- poses for which the certificate may be used. In a CA certificate, these policy information terms limit the set of policies for certifi- cation paths which include this certificate. When a CA does not wish to limit the set of policies for certification paths which include this certificate, they may assert the special policy anyPolicy, with Housley, Ford, Polk, & Solo [Page 30] INTERNET DRAFT July 14, 2000 a value of {2 5 29 32 0}. Applications with specific policy requirements are expected to have a list of those policies which they will accept and to compare the pol- icy OIDs in the certificate to that list. If this extension is crit- ical, the path validation software MUST be able to interpret this extension (including the optional qualifier), or MUST reject the cer- tificate. To promote interoperability, this profile RECOMMENDS that policy information terms consist of only an OID. Where an OID alone is insufficient, this profile strongly recommends that use of qualifiers be limited to those identified in this section. When qualifiers are used with the special policy anyPolicy, they MUST be limited to the qualifers identified in this section. This specification defines two policy qualifier types for use by cer- tificate policy writers and certificate issuers. The qualifier types are the CPS Pointer and User Notice qualifiers. The CPS Pointer qualifier contains a pointer to a Certification Prac- tice Statement (CPS) published by the CA. The pointer is in the form of a URI. User notice is intended for display to a relying party when a certi- ficate is used. The application software SHOULD display all user notices in all certificates of the certification path used, except that if a notice is duplicated only one copy need be displayed. To prevent such duplication, this qualifier SHOULD only be present in end-entity certificates and CA certificates issued to other organiza- tions. The user notice has two optional fields: the noticeRef field and the explicitText field. The noticeRef field, if used, names an organization and identi- fies, by number, a particular textual statement prepared by that organization. For example, it might identify the organization "CertsRUs" and notice number 1. In a typical implementation, the application software will have a notice file containing the current set of notices for CertsRUs; the application will extract the notice text from the file and display it. Messages may be multilingual, allowing the software to select the particular language message for its own environment. An explicitText field includes the textual statement directly in the certificate. The explicitText field is a string with a max- imum size of 200 characters. Housley, Ford, Polk, & Solo [Page 31] INTERNET DRAFT July 14, 2000 If both the noticeRef and explicitText options are included in the one qualifier and if the application software can locate the notice text indicated by the noticeRef option then that text should be displayed; otherwise, the explicitText string should be displayed. id-ce-certificatePolicies OBJECT IDENTIFIER ::= { id-ce 32 } anyPolicy OBJECT IDENTIFIER ::= {id-ce-certificate-policies 0} certificatePolicies ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation PolicyInformation ::= SEQUENCE { policyIdentifier CertPolicyId, policyQualifiers SEQUENCE SIZE (1..MAX) OF PolicyQualifierInfo OPTIONAL } CertPolicyId ::= OBJECT IDENTIFIER PolicyQualifierInfo ::= SEQUENCE { policyQualifierId PolicyQualifierId, qualifier ANY DEFINED BY policyQualifierId } -- policyQualifierIds for Internet policy qualifiers id-qt OBJECT IDENTIFIER ::= { id-pkix 2 } id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 } id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 } PolicyQualifierId ::= OBJECT IDENTIFIER ( id-qt-cps | id-qt-unotice ) Qualifier ::= CHOICE { cPSuri CPSuri, userNotice UserNotice } CPSuri ::= IA5String UserNotice ::= SEQUENCE { noticeRef NoticeReference OPTIONAL, explicitText DisplayText OPTIONAL} NoticeReference ::= SEQUENCE { organization DisplayText, noticeNumbers SEQUENCE OF INTEGER } DisplayText ::= CHOICE { ia5String IA5String (SIZE (1..200)), visibleString VisibleString (SIZE (1..200)), Housley, Ford, Polk, & Solo [Page 32] INTERNET DRAFT July 14, 2000 bmpString BMPString (SIZE (1..200)), utf8String UTF8String (SIZE (1..200)) } 4.2.1.6 Policy Mappings This extension is used in CA certificates. It lists one or more pairs of OIDs; each pair includes an issuerDomainPolicy and a sub- jectDomainPolicy. The pairing indicates the issuing CA considers its issuerDomainPolicy equivalent to the subject CA's subjectDomainPol- icy. The issuing CA's users may accept an issuerDomainPolicy for certain applications. The policy mapping tells the issuing CA's users which policies associated with the subject CA are comparable to the policy they accept. 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 MUST be non-critical. id-ce-policyMappings OBJECT IDENTIFIER ::= { id-ce 33 } PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE { issuerDomainPolicy CertPolicyId, subjectDomainPolicy CertPolicyId } 4.2.1.7 Subject Alternative Name The subject alternative names extension allows additional identities to be bound to the subject of the certificate. Defined options include an Internet electronic mail address, a DNS name, an IP address, and a uniform resource identifier (URI). Other options exist, including completely local definitions. Multiple name forms, and multiple instances of each name form, may be included. Whenever such identities are to be bound into a certificate, the subject alternative name (or issuer alternative name) extension MUST be used. Because the subject alternative name is considered to be definitively bound to the public key, all parts of the subject alternative name MUST be verified by the CA. Further, if the only subject identity included in the certificate is an alternative name form (e.g., an electronic mail address), then the subject distinguished name MUST be empty (an empty sequence), and the subjectAltName extension MUST be present. If the subject field con- tains an empty sequence, the subjectAltName extension MUST be marked Housley, Ford, Polk, & Solo [Page 33] INTERNET DRAFT July 14, 2000 critical. When the subjectAltName extension contains an Internet mail address, 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 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 surrounded in parentheses) after it, and is not surrounded by "<" and ">". Note that while upper and lower case letters are allowed in an RFC 822 addr-spec, no significance is attached to the case. When the subjectAltName extension contains a iPAddress, the address MUST be stored in the octet string in "network byte order," as speci- fied in RFC 791 [RFC 791]. The least significant bit (LSB) of each octet is the LSB of the corresponding byte in the network address. For IP Version 4, as specified in RFC 791, the octet string MUST con- tain exactly four octets. For IP Version 6, as specified in RFC 1883, the octet string MUST contain exactly sixteen octets [RFC 1883]. When the subjectAltName extension contains a domain name service 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 1034 [RFC 1034]. Note that while upper and lower case letters are allowed in domain names, no signifigance is attached to the case. In addition, while the string " " is a legal domain name, subjectAltName extensions with a dNSName " " are not permitted. Finally, the use of the DNS representation for Internet mail addresses (wpolk.nist.gov instead of wpolk@nist.gov) is not permitted; such identities are to be encoded as rfc822Name. Note: work is currently underway to specify domain names in interna- tional character sets. This names will likely not be accomodated by IA5String. Once this work is complete, this profile will be revisited and the appropriate functionality will be added. When the subjectAltName extension contains a URI, the name MUST be stored in the uniformResourceIdentifier (an IA5String). The name MUST 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 (e.g., "http" or "ftp") and a scheme-specific-part. The scheme- specific-part must include a fully qualified domain name or IP address as the host. As specified in [RFC 1738], the scheme name is not case-sensitive (e.g., "http" is equivalent to "HTTP"). The host part is also not case-sensitive, but other components of the scheme-specific-part may be case-sensitive. When comparing URIs, conforming implementations Housley, Ford, Polk, & Solo [Page 34] INTERNET DRAFT July 14, 2000 MUST compare the scheme and host without regard to case, but assume the remainder of the scheme-specific-part is case sensitive. When the subjectAltName extension contains a DN in the directoryName, 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 certificate with the same DN to the same subject entity. The subjectAltName may carry additional name types through the use of the otherName field. The format and semantics of the name are indi- cated through the OBJECT IDENTIFIER in the type-id field. The name itself is conveyed as value field in otherName. For example, Ker- beros [RFC 1510] format names can be encoded into the otherName, using the krb5PrincipalName OID and the KerberosName syntax as defined in [PKINIT]. Subject alternative names may be constrained in the same manner as subject distinguished names using the name constraints extension as described in section 4.2.1.11. If the subjectAltName extension is present, the sequence MUST contain at least one entry. Unlike the subject field, conforming CAs MUST NOT issue certificates with subjectAltNames containing empty General- Name fields. For example, an rfc822Name is represented as an IA5String. While an empty string is a valid IA5String, such an rfc822Name is not permitted by this profile. The behavior of clients that encounter such a certificate when processing a certificication path is not defined by this profile. Finally, the semantics of subject alternative names that include wildcard characters (e.g., as a placeholder for a set of names) are not addressed by this specification. Applications with specific requirements may use such names but shall define the semantics. id-ce-subjectAltName OBJECT IDENTIFIER ::= { id-ce 17 } SubjectAltName ::= GeneralNames GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName GeneralName ::= CHOICE { otherName [0] OtherName, rfc822Name [1] IA5String, dNSName [2] IA5String, x400Address [3] ORAddress, directoryName [4] Name, ediPartyName [5] EDIPartyName, Housley, Ford, Polk, & Solo [Page 35] INTERNET DRAFT July 14, 2000 uniformResourceIdentifier [6] IA5String, iPAddress [7] OCTET STRING, registeredID [8] OBJECT IDENTIFIER} OtherName ::= SEQUENCE { type-id OBJECT IDENTIFIER, value [0] EXPLICIT ANY DEFINED BY type-id } EDIPartyName ::= SEQUENCE { nameAssigner [0] DirectoryString OPTIONAL, partyName [1] DirectoryString } 4.2.1.8 Issuer Alternative Names As with 4.2.1.7, this extension is used to associate Internet style identities with the certificate issuer. Issuer alternative names MUST be encoded as in 4.2.1.7. Where present, this extension SHOULD NOT be marked critical. id-ce-issuerAltName OBJECT IDENTIFIER ::= { id-ce 18 } IssuerAltName ::= GeneralNames 4.2.1.9 Subject Directory Attributes The subject directory attributes extension is not recommended as an essential part of this profile, but it may be used in local environ- ments. This extension MUST be non-critical. id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= { id-ce 9 } SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute 4.2.1.10 Basic Constraints The basic constraints extension identifies whether the subject of the certificate is a CA and how deep a certification path may exist through that CA. The cA bit indicates if the certified public key may be used to ver- ify signatures on other certificates. If the cA bit is asserted, then the keyCertSign bit in the key usage extension (see 4.2.1.3) MUST also be asserted. If the cA bit is not asserted, then the keyCertSign bit in the key usage extension MUST NOT be asserted. 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 Housley, Ford, Polk, & Solo [Page 36] INTERNET DRAFT July 14, 2000 follow this certificate in a certification path. (Note: One end- entity certificate will follow the final CA certificate in the path. The last certificate in a path is considered an end-entity certifi- cate, whether the subject of the certificate is a CA or not.) A pathLenConstrinat of zero indicates that only an end-entity certifi- cate may follow in the path. Where it appears, the pathLenConstraint field MUST be greater than or equal to zero. Where pathLenConstraint does not appear, there is no limit to the allowed length of the cer- tification path. This extension MUST appear as a critical extension in all CA certifi- cates. This extension MAY appear as a critical or non-critical extension in end entity certificates. id-ce-basicConstraints OBJECT IDENTIFIER ::= { id-ce 19 } BasicConstraints ::= SEQUENCE { cA BOOLEAN DEFAULT FALSE, pathLenConstraint INTEGER (0..MAX) OPTIONAL } 4.2.1.11 Name Constraints The name constraints extension, which MUST be used only in a CA cer- tificate, indicates a name space within which all subject names in subsequent certificates in a certification path shall be located. Restrictions may apply to the subject distinguished name or subject alternative names. Restrictions apply only when the specified name form is present. If no name of the type is in the certificate, the certificate is acceptable. Name constraints are not applied to certificates whose issuer and subject are identical. (This could prevent CAs that utilize name constraints from issuing self-signed certificates to implement key rollover.) Restrictions are defined in terms of permitted or excluded name sub- trees. Any name matching a restriction in the excludedSubtrees field is invalid regardless of information appearing in the permittedSub- trees. This extension MUST be critical. Within this profile, the minimum and maximum fields are not used with any name forms, thus minimum is always zero, and maximum is always absent. For URIs, the constraint applies to the host part of the name. The constraint may specify a host or a domain. Examples would be "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, Housley, Ford, Polk, & Solo [Page 37] INTERNET DRAFT July 14, 2000 the constraint ".xyz.com" is satisfied by both abc.xyz.com and 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 specifies a host. A name constraint for Internat mail addresses may specify a particu- lar mailbox, all addresses at a particular host, or all mailboxes in a domain. To indicate a particular mailbox, the constraint is the complete mail address. For example, "root@xyz.com" indicates the root mailbox on the host "xyz.com". To indicate all Internet mail addresses on a particular host, the constraint is specified as the host name. For example, the constraint "xyz.com" is satisfied by any mail address at the host "xyz.com". To specify any address within a domain, the constraint is specified with a leading period (as with URIs). For example, ".xyz.com" indicates all the Internet mail addresses in the domain "xyz.com", but not Internet mail addresses on the host "xyz.com". 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 satisfies the name constraint. For example, www.foo.bar.com would satisfy the constraint but foo1.bar.com would not. Legacy implementations exist where an RFC 822 name is embedded in the subject distinguished name in an attribute of type EmailAddress (see sec. 4.1.2.6). When rfc822 names are constrained, but the certificate does not include a subject alternative name, the rfc822 name con- straint MUST be applied to the attribute of type EmailAddress in the subject distinguished name. The ASN.1 syntax for EmailAddress and the corresponding OID are supplied in Appendix A and B. Restrictions of the form directoryName MUST be applied to the subject field in the certificate and to the subjectAltName extensions of type directoryName. Restrictions of the form x400Address MUST be applied to subjectAltName extensions of type x400Address. When applying restrictions of the form directoryName, an implementa- tion MUST compare DN attributes. At a minimum, implementations MUST perform the DN comparison rules specified in Section 4.1.2.4. CAs issuing certificates with a restriction of the form directoryName SHOULD NOT rely on implementation of the full ISO DN name comparison algorithm. This implies name restrictions shall be stated identi- cally to the encoding used in the subject field or subjectAltName extension. The syntax of iPAddress MUST be as described in section 4.2.1.7 with the following additions specifically for Name Constraints. For IPv4 addresses, the ipAddress field of generalName MUST contain eight (8) Housley, Ford, Polk, & Solo [Page 38] INTERNET DRAFT July 14, 2000 octets, encoded in the style of RFC 1519 (CIDR) to represent an address range.[RFC 1519] For IPv6 addresses, the ipAddress field MUST contain 32 octets similarly encoded. For example, a name con- straint 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 10.9.8.0/255.255.255.0. The syntax and semantics for name constraints for otherName, ediPar- tyName, and registeredID are not defined by this specification. id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 } NameConstraints ::= SEQUENCE { permittedSubtrees [0] GeneralSubtrees OPTIONAL, excludedSubtrees [1] GeneralSubtrees OPTIONAL } GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree GeneralSubtree ::= SEQUENCE { base GeneralName, minimum [0] BaseDistance DEFAULT 0, maximum [1] BaseDistance OPTIONAL } BaseDistance ::= INTEGER (0..MAX) 4.2.1.12 Policy Constraints The policy constraints extension can be used in certificates issued to CAs. The policy constraints extension constrains path validation in two ways. It can be used to prohibit policy mapping or require that each certificate in a path contain an acceptable policy identif- ier. If the inhibitPolicyMapping field is present, the value indicates the number of additional certificates that may appear in the path before policy mapping is no longer permitted. For example, a value of one indicates that policy mapping may be processed in certificates issued by the subject of this certificate, but not in additional certifi- cates in the path. If the requireExplicitPolicy field is present, subsequent certifi- cates shall include an acceptable policy identifier. The value of requireExplicitPolicy indicates the number of additional certificates that may appear in the path before an explicit policy is required. An acceptable policy identifier is the identifier of a policy required by the user of the certification path or the identifier of a policy which has been declared equivalent through policy mapping. Housley, Ford, Polk, & Solo [Page 39] INTERNET DRAFT July 14, 2000 Conforming CAs MUST NOT issue certificates where policy constraints is a null sequence. That is, at least one of the inhibitPolicyMapping field or the requireExplicitPolicy field MUST be present. The behavior of clients that encounter a null policy constraints field is not addressed in this profile. This extension may be critical or non-critical. id-ce-policyConstraints OBJECT IDENTIFIER ::= { id-ce 36 } PolicyConstraints ::= SEQUENCE { requireExplicitPolicy [0] SkipCerts OPTIONAL, inhibitPolicyMapping [1] SkipCerts OPTIONAL } SkipCerts ::= INTEGER (0..MAX) 4.2.1.13 Extended key usage field 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- poses indicated in the key usage extension field. This field is defined as follows: id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37} ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId KeyPurposeId ::= OBJECT IDENTIFIER Key purposes may be defined by any organization with a need. Object identifiers used to identify key purposes shall be assigned in accor- dance with IANA or ITU-T Rec. X.660 | ISO/IEC/ITU 9834-1. This extension may, at the option of the certificate issuer, be either critical or non-critical. If the extension is flagged critical, then the certificate MUST be used only for one of the purposes indicated. If the extension is flagged non-critical, then it indicates the intended purpose or purposes of the key, and may be used in finding the correct key/certificate of an entity that has multiple keys/certificates. It is an advisory field and does not imply that usage of the key is restricted by the certification authority to the purpose indicated. Certificate using applications may nevertheless require that a particular purpose be indicated in order for the cer- tificate to be acceptable to that application. Housley, Ford, Polk, & Solo [Page 40] INTERNET DRAFT July 14, 2000 If a certificate contains both a critical key usage field and a crit- ical extended key usage field, then both fields MUST be processed independently and the certificate MUST only be used for a purpose consistent with both fields. If there is no purpose consistent with both fields, then the certificate MUST NOT be used for any purpose. The following key usage purposes are defined by this profile: id-kp OBJECT IDENTIFIER ::= { id-pkix 3 } id-kp-serverAuth OBJECT IDENTIFIER ::= {id-kp 1} -- TLS Web server authentication -- Key usage bits that may be consistent: digitalSignature, -- keyEncipherment or keyAgreement -- id-kp-clientAuth OBJECT IDENTIFIER ::= {id-kp 2} -- TLS Web client authentication -- Key usage bits that may be consistent: digitalSignature and/or -- keyAgreement -- id-kp-codeSigning OBJECT IDENTIFIER ::= {id-kp 3} -- Signing of downloadable executable code -- Key usage bits that may be consistent: digitalSignature -- id-kp-emailProtection OBJECT IDENTIFIER ::= {id-kp 4} -- E-mail protection -- Key usage bits that may be consistent: digitalSignature, -- nonRepudiation, and/or (keyEncipherment -- or keyAgreement) -- id-kp-timeStamping OBJECT IDENTIFIER ::= { id-kp 8 } -- Binding the hash of an object to a time from an agreed-upon time -- source. Key usage bits that may be consistent: digitalSignature, -- nonRepudiation 4.2.1.14 CRL Distribution Points The CRL distribution points extension identifies how CRL information is obtained. The extension SHOULD be non-critical, but this profile recommends support for this extension by CAs and applications. Further discussion of CRL management is contained in section 5. The cRLDistributionPoints extension is a SEQUENCE of Distribution- Point. A DistributionPoint consists of three fields, each of which is optional: the name of the DistributionPoint, ReasonsFlags, and the cRLIssuer. While each component is optional, a DistributionPoint MUST NOT consist of only the ReasonsFlags field. If the distribution- Point omits cRLIssuer, the CRL MUST be issued by the CA that issued Housley, Ford, Polk, & Solo [Page 41] INTERNET DRAFT July 14, 2000 the certificate. If the distributionPointName is absent, cRLIssuer MUST be present and include a Name corresponding to an X.500 or LDAP directory entry where the CRL is located. If the cRLDistributionPoints extension contains a Distribution- PointName of type URI, the following semantics MUST be assumed: the URI is a pointer to the current CRL for the associated reasons and will be issued by the associated cRLIssuer. The expected values for the URI are those defined in 4.2.1.7. Processing rules for other values are not defined by this specification. If the distribution- Point omits reasons, the CRL MUST include revocations for all rea- sons. id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= { id-ce 31 } CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint DistributionPoint ::= SEQUENCE { distributionPoint [0] DistributionPointName OPTIONAL, reasons [1] ReasonFlags OPTIONAL, cRLIssuer [2] GeneralNames OPTIONAL } DistributionPointName ::= CHOICE { fullName [0] GeneralNames, nameRelativeToCRLIssuer [1] RelativeDistinguishedName } ReasonFlags ::= BIT STRING { unused (0), keyCompromise (1), cACompromise (2), affiliationChanged (3), superseded (4), cessationOfOperation (5), certificateHold (6) } 4.2.1.15 Inhibit Any-Policy The inhibit any-policy extension can be used in certificates issued 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 match for other certificate policies. The value indicates the number of additional certificates that may appear in the path before any- policy is no longer permitted. For example, a value of one indicates that any-policy may be processed in certificates issued by the sub- ject of this certificate, but not in additional certificates in the path. This extension MUST be critical. Housley, Ford, Polk, & Solo [Page 42] INTERNET DRAFT July 14, 2000 id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= { id-ce 54 } InhibitAnyPolicy ::= SkipCerts SkipCerts ::= INTEGER (0..MAX) 4.2.1.16 Freshest CRL (a.k.a. Delta CRL Distribution Point) The freshest CRL extension identifies how delta-CRL information is obtained. The extension MUST be non-critical. Further discussion of CRL management is contained in section 5. The same syntax is used for this extension and the cRLDistribution- Points extension, and is described in section 4.2.1.14. The same conventions apply to both extensions. id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 } FreshestCRL ::= CRLDistributionPoints 4.2.2 Private Internet Extensions This section defines one new extension for use in the Internet Public Key Infrastructure. This extension may be used to direct applica- tions to identify an on-line validation service supporting the issu- ing CA. As the information may be available in multiple forms, each extension is a sequence of IA5String values, each of which represents a URI. The URI implicitly specifies the location and format of the information and the method for obtaining the information. An object identifier is defined for the private extension. The object identifier associated with the private extension is defined under the arc id-pe within the id-pkix name space. Any future exten- sions defined for the Internet PKI will also be defined under the arc id-pe. id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) } id-pe OBJECT IDENTIFIER ::= { id-pkix 1 } 4.2.2.1 Authority Information Access The authority information access extension indicates how to access CA information and services for the issuer of the certificate in which the extension appears. Information and services may include on-line Housley, Ford, Polk, & Solo [Page 43] INTERNET DRAFT July 14, 2000 validation services and CA policy data. (The location of CRLs is not specified in this extension; that information is provided by the cRLDistributionPoints extension.) This extension may be included in subject or CA certificates, and it MUST be non-critical. id-pe-authorityInfoAccess OBJECT IDENTIFIER ::= { id-pe 1 } AuthorityInfoAccessSyntax ::= SEQUENCE SIZE (1..MAX) OF AccessDescription AccessDescription ::= SEQUENCE { accessMethod OBJECT IDENTIFIER, accessLocation GeneralName } id-ad OBJECT IDENTIFIER ::= { id-pkix 48 } id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 } Each entry in the sequence AuthorityInfoAccessSyntax describes the format and location of additional information provided by the CA who issued 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 OID for accessMethod. The id-ad-caIssuers OID is used when the additional information lists CAs that have issued certificates superior to the CA that issued the certificate containing this extension. The referenced CA Issuers description is intended to aid certificate users in the selection of a certification path that terminates at a point trusted by the certificate user. When id-ad-caIssuers appears as accessInfoType, the accessLocation field describes the referenced description server and the access pro- tocol to obtain the referenced description. 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 accessLocation (when accessMethod is id-ad-caIssuers) are not defined by this specification. The information [RFC 2560] defines the access descriptor for the Online Certificate Status Protocol. Additional access descriptors may be defined in other PKIX specifications. Housley, Ford, Polk, & Solo [Page 44] INTERNET DRAFT July 14, 2000 5 CRL and CRL Extensions Profile As described above, one goal of this X.509 v2 CRL profile is to foster the creation of an interoperable and reusable Internet PKI. To achieve this goal, guidelines for the use of extensions are speci- fied, and some assumptions are made about the nature of information included in the CRL. CRLs may be used in a wide range of applications and environments covering a broad spectrum of interoperability goals and an even broader spectrum of operational and assurance requirements. This profile establishes a common baseline for generic applications requiring broad interoperability. The profile defines a baseline set of information that can be expected in every CRL. Also, the profile defines common locations within the CRL for frequently used attri- butes as well as common representations for these attributes. This profile does not define any private Internet CRL extensions or CRL entry extensions. Environments with additional or special purpose requirements may build on this profile or may replace it. Conforming CAs are not required to issue CRLs if other revocation or certificate status mechanisms are provided. Conforming CAs that 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 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 applications are required to process version 1 and 2 CRLs. 5.1 CRL Fields 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- ing is a tag, length, value encoding system for each element. CertificateList ::= SEQUENCE { tbsCertList TBSCertList, signatureAlgorithm AlgorithmIdentifier, signatureValue BIT STRING } TBSCertList ::= SEQUENCE { version Version OPTIONAL, -- if present, shall be v2 signature AlgorithmIdentifier, issuer Name, thisUpdate Time, Housley, Ford, Polk, & Solo [Page 45] INTERNET DRAFT July 14, 2000 nextUpdate Time OPTIONAL, revokedCertificates SEQUENCE OF SEQUENCE { userCertificate CertificateSerialNumber, revocationDate Time, crlEntryExtensions Extensions OPTIONAL -- if present, shall be v2 } OPTIONAL, crlExtensions [0] EXPLICIT Extensions OPTIONAL -- if present, shall be v2 } -- Version, Time, CertificateSerialNumber, and Extensions -- are all defined in the ASN.1 in section 4.1 -- AlgorithmIdentifier is defined in section 4.1.1.2 The following items describe the use of the X.509 v2 CRL in the Internet PKI. 5.1.1 CertificateList Fields The CertificateList is a SEQUENCE of three required fields. The fields are described in detail in the following subsections. 5.1.1.1 tbsCertList The first field in the sequence is the tbsCertList. This field is itself a sequence containing the name of the issuer, issue date, issue date of the next list, the optional list of revoked certifi- cates, and optional CRL extensions. When there are no revoked certi- ficates, the revoked certificates list is absent. When one or more certificates are revoked, each entry on the revoked certificate list is defined by a sequence of user certificate serial number, revoca- tion date, and optional CRL entry extensions. 5.1.1.2 signatureAlgorithm The signatureAlgorithm field contains the algorithm identifier for 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. [PKIX ALGS] lists the supported algorithms for this specification. Conforming CAs MUST use the algorithm identifiers presented in [PKIX ALGS] when signing with a supported signature algorithm. This field MUST contain the same algorithm identifier as the signa- ture field in the sequence tbsCertList (see sec. 5.1.2.2). Housley, Ford, Polk, & Solo [Page 46] INTERNET DRAFT July 14, 2000 5.1.1.3 signatureValue The signatureValue field contains a digital signature computed upon 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 then ASN.1 encoded as a BIT STRING and included in the CRL's sig- natureValue field. The details of this process are specified for each of the supported algorithms in [PKIX ALGS]. 5.1.2 Certificate List "To Be Signed" The certificate list to be signed, or TBSCertList, is a SEQUENCE of required and optional fields. The required fields identify 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 CRL. Optional fields include lists of revoked certificates and CRL exten- sions. The revoked certificate list is optional to support the case where a CA has not revoked any unexpired certificates that it has issued. The profile requires conforming CAs to use the CRL extension cRLNumber in all CRLs issued. 5.1.2.1 Version This optional field describes the version of the encoded CRL. When extensions are used, as required by this profile, this field MUST be present and MUST specify version 2 (the integer value is 1). 5.1.2.2 Signature This field contains the algorithm identifier for the algorithm used to sign the CRL. [PKIX ALGS] lists OIDs for the most popular signa- ture algorithms used in the Internet PKI. This field MUST contain the same algorithm identifier as the signa- tureAlgorithm field in the sequence CertificateList (see section 5.1.1.2). 5.1.2.3 Issuer Name The issuer name identifies the entity who has signed and issued the CRL. The issuer identity is carried in the issuer name field. Alter- native name forms may also appear in the issuerAltName extension (see sec. 5.2.2). The issuer name field MUST contain an X.500 dis- tinguished name (DN). The issuer name field is defined as the X.501 type Name, and MUST follow the encoding rules for the issuer name field in the certificate (see sec. 4.1.2.4). Housley, Ford, Polk, & Solo [Page 47] INTERNET DRAFT July 14, 2000 5.1.2.4 This Update This field indicates the issue date of this CRL. ThisUpdate may be encoded as UTCTime or GeneralizedTime. CAs conforming to this profile that issue CRLs MUST encode thisUpdate as UTCTime for dates through the year 2049. CAs conforming to this profile that issue CRLs MUST encode thisUpdate as GeneralizedTime for dates in the year 2050 or later. Where encoded as UTCTime, thisUpdate MUST be specified and inter- preted as defined in section 4.1.2.5.1. Where encoded as General- izedTime, thisUpdate MUST be specified and interpreted as defined in section 4.1.2.5.2. 5.1.2.5 Next Update 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 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. nextUpdate may be encoded as UTCTime or GeneralizedTime. This profile requires inclusion of nextUpdate in all CRLs issued by conforming CAs. Note that the ASN.1 syntax of TBSCertList describes this field as OPTIONAL, which is consistent with the ASN.1 structure defined in [X.509]. The behavior of clients processing CRLs which omit nextUpdate is not specified by this profile. CAs conforming to this profile that issue CRLs MUST encode nextUpdate as UTCTime for dates through the year 2049. CAs conforming to this profile that issue CRLs MUST encode nextUpdate as GeneralizedTime for dates in the year 2050 or later. Where encoded as UTCTime, nextUpdate MUST be specified and inter- preted as defined in section 4.1.2.5.1. Where encoded as General- izedTime, nextUpdate MUST be specified and interpreted as defined in section 4.1.2.5.2. 5.1.2.6 Revoked Certificates When there are no revoked certificates, the revoked certificates list is absent. Otherwise, revoked certificates are listed by their serial numbers. Certificates revoked by the CA are uniquely identi- fied by the certificate serial number. The date on which the revoca- tion occurred is specified. The time for revocationDate MUST be expressed as described in section 5.1.2.4. Additional information may be supplied in CRL entry extensions; CRL entry extensions are Housley, Ford, Polk, & Solo [Page 48] INTERNET DRAFT July 14, 2000 discussed in section 5.3. 5.1.2.7 Extensions 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. CRL extensions are discussed in section 5.2. 5.2 CRL Extensions 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 with CRLs. The X.509 v2 CRL format also allows communities to define private extensions to carry information unique to those communities. Each extension in a CRL may be designated as critical or non- critical. A CRL validation MUST fail if it encounters a critical extension which it does not know how to process. However, an unrecognized non-critical extension may be ignored. The following subsections present those extensions used within Internet CRLs. Com- munities may elect to include extensions in CRLs which are not defined in this specification. However, caution should be exercised in adopting any critical extensions in CRLs which might be used in a general context. 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) extensions in all CRLs issued. 5.2.1 Authority Key Identifier The authority key identifier extension provides a means of identify- ing the public key corresponding to the private key used to sign a CRL. The identification can be based on either the key identifier (the subject key identifier in the CRL signer's certificate) or on the issuer name and serial number. This extension is especially use- ful where an issuer has more than one signing key, either due to mul- tiple concurrent key pairs or due to changeover. Conforming CAs MUST use the key identifier method, and MUST include this extension in all CRLs issued. The syntax for this CRL extension is defined in section 4.2.1.1. 5.2.2 Issuer Alternative Name The issuer alternative names extension allows additional identities to be associated with the issuer of the CRL. Defined options include an rfc822 name (electronic mail address), a DNS name, an IP address, Housley, Ford, Polk, & Solo [Page 49] INTERNET DRAFT July 14, 2000 and a URI. Multiple instances of a name and multiple name forms may be included. Whenever such identities are used, the issuer alterna- tive name extension MUST be used. The issuerAltName extension SHOULD NOT be marked critical. The OID and syntax for this CRL extension are defined in section 4.2.1.8. 5.2.3 CRL Number The CRL number is a non-critical CRL extension which conveys a mono- tonically increasing sequence number for each CRL issued by a CA. This extension allows users to easily determine when a particular CRL supersedes another CRL. CAs conforming to this profile MUST include this extension in all CRLs. id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 } cRLNumber ::= INTEGER (0..MAX) 5.2.4 Delta CRL Indicator The delta CRL indicator is a critical CRL extension that identifies a CRL as being a delta CRL. Delta CRLs contain updates to revocation information previously distributed, rather than all the information that would appear in a complete CRL. The use of delta CRLs can sig- nificantly reduce network load and processing time in some environ- ments. Delta CRLs are generally smaller than the CRLs they update, so applications that obtain delta CRLs consume less network bandwidth than applications that obtain the corresponding complete CRLs. Applications which store revocation information in a format other than the CRL structure can add new revocation information to the local database without reprocessing information. The delta CRL indicator extension contains a single value of type BaseCRLNumber. This value identifies the CRL number of the base 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 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 indicator extension contains all updates to the certificate revoca- tion status for that same scope. The combination of a CRL containing the delta CRL indicator extension plus the CRL referenced in the BaseCRLNumber component of this extension is equivalent to a full CRL, for the applicable scope, at the time of publication of the delta CRL. Housley, Ford, Polk, & Solo [Page 50] INTERNET DRAFT July 14, 2000 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 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 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 covered by the base CRL it references. An application can construct a CRL that is complete for a given 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 that has a cRLNumber greater than or equal to the cRLNumber of the base CRL referenced in the delta CRL; or (b) by retrieving the current delta CRL for that scope and combin- ing 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 extension found in the delta CRL used in its construction. CAs must ensure that application of a delta CRL to the referenced base revocation information accurately reflects the current status of revocation. If a CA supports the certificateHold revocation reason the following rules must be applied when generating delta CRLs: (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- plete for a given scope), whose cRLNumber is n, and the hold is subsequently released, the certificate must be included in all 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- ficate must be listed with revocation reason removeFromCRL unless the certificate is subsequently revoked again for one of the revo- cation reasons covered by the delta CRL, in which case the certi- ficate must be listed with the revocation reason appropriate for the subsequent revocation. (b) If the certificate was not removed from hold, but was per- manently revoked, then it must be listed on all subsequent delta CRLs where the cRLNumber of the referenced base CRL is less than the cRLNumber of the CRL (either a delta CRL or a CRL that is com- plete for the given scope) on which the permanent revocation notice first appeared. id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 } Housley, Ford, Polk, & Solo [Page 51] INTERNET DRAFT July 14, 2000 deltaCRLIndicator EXTENSION ::= { SYNTAX BaseCRLNumber IDENTIFIED BY id-ce-deltaCRLIndicator } BaseCRLNumber ::= CRLNumber 5.2.5 Issuing Distribution Point The issuing distribution point is a critical CRL extension that iden- tifies the CRL distribution point for a particular CRL, and it indi- cates whether the CRL covers revocation for end entity certificates only, CA certificates only, or a limited set of reason codes. Although the extension is critical, conforming implementations are not required to support this extension. 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 X.500 Directory, it is stored in the Directory entry corresponding to the CRL distribution point, which may be different than the Directory entry of the CA. The reason codes associated with a distribution point shall be speci- fied in onlySomeReasons. If onlySomeReasons does not appear, the dis- tribution point shall contain revocations for all reason codes. CAs may use CRL distribution points to partition the CRL on the basis of compromise and routine revocation. In this case, the revocations with reason code keyCompromise (1) and cACompromise (2) appear in one distribution point, and the revocations with other reason codes appear in another distribution point. Where the issuingDistributionPoint extension contains a URL, the fol- lowing semantics MUST be assumed: the object is a pointer to the most current CRL issued by this CA. The URI schemes ftp, http, mailto [RFC1738] and ldap [RFC1778] are defined for this purpose. The URI MUST be an absolute, not relative, pathname and MUST specify the host. id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 } issuingDistributionPoint ::= SEQUENCE { distributionPoint [0] DistributionPointName OPTIONAL, onlyContainsUserCerts [1] BOOLEAN DEFAULT FALSE, onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE, onlySomeReasons [3] ReasonFlags OPTIONAL, indirectCRL [4] BOOLEAN DEFAULT FALSE } Housley, Ford, Polk, & Solo [Page 52] INTERNET DRAFT July 14, 2000 5.2.6 Freshest CRL (a.k.a. Delta CRL Distribution Point) The freshest CRL extension identifies how delta-CRL information for this CRL is obtained. The extension MUST be non-critical. The same syntax is used for this extension as the cRLDistribution- Points certificate extension, and is described in section 4.2.1.14. The same conventions apply to both extensions. id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 } FreshestCRL ::= CRLDistributionPoints 5.3 CRL Entry Extensions The CRL entry extensions already defined by ANSI X9 and ISO/IEC/ITU for X.509 v2 CRLs provide methods for associating additional attri- butes with CRL entries [X.509] [X9.55]. The X.509 v2 CRL format also allows communities to define private CRL entry extensions to carry information unique to those communities. Each extension in a CRL entry may be designated as critical or non-critical. A CRL valida- tion MUST fail if it encounters a critical CRL entry extension which it does not know how to process. However, an unrecognized non- critical CRL entry extension may be ignored. The following subsec- tions present recommended extensions used within Internet CRL entries and standard locations for information. Communities may elect to use additional CRL entry extensions; however, caution should be exercised in adopting any critical extensions in CRL entries which might be used in a general context. All CRL entry extensions used in this specification are non-critical. Support for these extensions is optional for conforming CAs and applications. However, CAs that issue CRLs SHOULD include reason codes (see sec. 5.3.1) and invalidity dates (see sec. 5.3.3) whenever this information is available. 5.3.1 Reason Code The reasonCode is a non-critical CRL entry extension that identifies the reason for the certificate revocation. CAs are strongly encouraged to include meaningful reason codes in CRL entries; how- ever, the reason code CRL entry extension SHOULD be absent instead of using the unspecified (0) reasonCode value. id-ce-cRLReason OBJECT IDENTIFIER ::= { id-ce 21 } -- reasonCode ::= { CRLReason } Housley, Ford, Polk, & Solo [Page 53] INTERNET DRAFT July 14, 2000 CRLReason ::= ENUMERATED { unspecified (0), keyCompromise (1), cACompromise (2), affiliationChanged (3), superseded (4), cessationOfOperation (5), certificateHold (6), removeFromCRL (8) } 5.3.2 Hold Instruction Code The hold instruction code is a non-critical CRL entry extension that provides a registered instruction identifier which indicates the action to be taken after encountering a certificate that has been placed on hold. id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 } holdInstructionCode ::= OBJECT IDENTIFIER The following instruction codes have been defined. Conforming appli- cations that process this extension MUST recognize the following instruction codes. holdInstruction OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) x9-57(10040) 2 } id-holdinstruction-none OBJECT IDENTIFIER ::= {holdInstruction 1} id-holdinstruction-callissuer OBJECT IDENTIFIER ::= {holdInstruction 2} id-holdinstruction-reject OBJECT IDENTIFIER ::= {holdInstruction 3} Conforming applications which encounter an id-holdinstruction- callissuer MUST call the certificate issuer or reject the certifi- cate. Conforming applications which encounter an id- holdinstruction-reject MUST reject the certificate. The hold instruc- tion id-holdinstruction-none is semantically equivalent to the absence of a holdInstructionCode, and its use is strongly deprecated for the Internet PKI. 5.3.3 Invalidity Date The invalidity date is a non-critical CRL entry extension that pro- vides the date on which it is known or suspected that the private key was compromised or that the certificate otherwise became invalid. 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 Housley, Ford, Polk, & Solo [Page 54] INTERNET DRAFT July 14, 2000 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 SHOULD NOT precede the date of issue of earlier CRLs. Whenever this information is available, CAs are strongly encouraged to share it with CRL users. The GeneralizedTime values included in this field MUST be expressed in Greenwich Mean Time (Zulu), and MUST be specified and interpreted as defined in section 4.1.2.5.2. id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 } invalidityDate ::= GeneralizedTime 5.3.4 Certificate Issuer This CRL entry extension identifies the certificate issuer associated with an entry in an indirect CRL, i.e. a CRL that has the indirectCRL indicator set in its issuing distribution point extension. If this extension is not present on the first entry in an indirect CRL, the certificate issuer defaults to the CRL issuer. On subsequent entries 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. This field is defined as follows: id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 } certificateIssuer ::= GeneralNames If used by conforming CAs that issue CRLs, this extension is always critical. If an implementation ignored this extension it could not correctly attribute CRL entries to certificates. This specification RECOMMENDS that implementations recognize this extension. 6 Certification Path Validation Certification path validation procedures for the Internet PKI are based on section 12.4.3 of [X.509]. Certification path processing verifies the binding between the subject distinguished name and/or subject alternative name and subject public key. The binding is lim- ited by constraints which are specified in the certificates which comprise the path. The basic constraints and policy constraints extensions allow the certification path processing logic to automate the decision making process. This section describes an algorithm for validating certification paths. Conforming implementations of this specification are not required to implement this algorithm, but MUST be functionally Housley, Ford, Polk, & Solo [Page 55] INTERNET DRAFT July 14, 2000 equivalent to the external behavior resulting from this procedure. Any algorithm may be used by a particular implementation so long as it derives the correct result. In section 6.1, the text describes basic path validation. This text assumes that all valid paths begin with certificates issued by a sin- gle "most-trusted CA". The algorithm requires the public key of the CA, the CA's name, the validity period of the public key, and any 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 a hierarchical PKI; the CA that issued the verifier's own certificate(s); or any other CA in a network PKI. The path valida- tion procedure is the same regardless of the choice of "most-trusted CA." section 6.2 describes extensions to the basic path validation algo- rithm. Two specific cases are discussed: the case where paths may begin with one of several trusted CAs; and where compatibility with the PEM architecture is required. 6.1 Basic Path Validation This text describes an algorithm for X.509 path processing. A con- formant implementation MUST include an X.509 path processing pro- cedure that is functionally equivalent to the external behavior of this algorithm. This text assumes that there is a single trust anchor for certifica- tion path processing, which simplifies the description of the path processing procedure. This procedure can be extended to address mul- tiple trust anchors, as discussed further in Section 6.2. The primary goal of path validation is to verify the binding between a subject distinguished name or subject alternative name and subject public key, as represented in the end entity certificate, based on the public key of the trust anchor. This requires obtaining a sequence of certificates that support that binding. The procedure performed to obtain this sequence of certificates is outside the scope of this section. To meet this goal, the path validation process verifies, among other things, that a prospective certification path (a sequence of n certi- ficates) satisfies the following conditions: (i) for all x in {1, ..., n-1}, the subject of certificate x is the issuer of certificate x+1; (ii) certificate 1 is issued by the trust anchor; Housley, Ford, Polk, & Solo [Page 56] INTERNET DRAFT July 14, 2000 (iii) certificate n is the end entity certificate; and (iv) for all x in {1, ..., n}, the certificate was valid at the time in question. A particular certification path may not, however, be appropriate for all applications. The path validation process also determines the set of certificate policies that are valid for this path, based on the certificate policies extension, policy mapping extension, policy constraints extension, and inhibit any-policy extension. To achieve this, the path validation algorithm constructs a "valid policy tree." 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, otherwise the result will be a NULL valid policy tree. This section presents the algorithm in four basic steps: (1) initial- ization, (2) basic certificate processing, (3) preparation for the next certificate, and (4) wrap-up. Steps (1) and (4) are performed exactly once. Step (2) is performed for all certificates in the path. Step (3) is performed for all certificates in the path except the final certificate. Figure 2 provides a high-level flowchart of this algorithm. Housley, Ford, Polk, & Solo [Page 57] INTERNET DRAFT July 14, 2000 +-------+ | START | +-------+ | V +----------------+ | Initialization | +----------------+ | +<--------------------+ | | V | +----------------+ | | Process Cert | | +----------------+ | | | V | +================+ | | IF Last Cert | | | in Path | | +================+ | | | | THEN | | ELSE | V V | +----------------+ +----------------+ | | Wrap up | | Prepare for | | +----------------+ | Next Cert | | | +----------------+ | V | | +-------+ +--------------+ | STOP | +-------+ Figure 2. Path Processing Flowchart 6.1.1 Inputs This algorithm assumes the following seven inputs are provided to the path processing logic: (a) a prospective certification path of length n; (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 the past. (c) user_initial_policy_set: A set of certificate policy identif- iers naming the policies that are acceptable to the certificate Housley, Ford, Polk, & Solo [Page 58] INTERNET DRAFT July 14, 2000 user. The user_initial_policy_set has the special value "any- policy" if the user is not concerned about certificate policy. (d) trust anchor information, describing a CA that serves as a trust anchor for the certification path. The trust anchor infor- mation includes: (1) the trusted issuer name, (2) optionally, the trusted issuer unique identifier, (3) the trusted public key algorithm, (4) the trusted public key, and (5) optionally, the trusted public key parameters associated with the public key. The trust anchor information may be provided to the path process- ing procedure in the form of a self-signed certificate. The trusted anchor information is trusted because it was delivered to the path processing procedure by some trustworthy "out-of-band" procedure. If the trusted public key algorithm requires parame- ters, then the parameters are provided along with the trusted pub- lic key. (e) initial-policy-mapping-inhibit, which indicates if policy map- ping is allowed in the certification path. (f) initial-explicit-policy, which indicates if the path must be valid for at least one of the certificate policies in the user_initial_policy_set. (g) initial-any-policy-inhibit, which indicates whether the any- policy OID should be processed if it is included in a certificate. 6.1.2 Initialization The initialization phase establishes twelve state variables based upon the seven inputs: (a) valid_policy_tree: A tree of certificate policies with their optional qualifiers; each of the leaves of the tree represents a valid policy at this stage in the certification path validation. If valid policies exist at this stage in the certification path validation, the depth of the tree is equal to the number of certi- ficates in the chain that have been processed. If valid policies do not exist at this stage in the certification path validation, the tree is set to NULL. Once the tree is set to NULL, policy pro- cessing ceases. Each node in the valid_policy_tree includes four data objects: the valid policy, a set of associated policy qualifiers, a set of one Housley, Ford, Polk, & Solo [Page 59] INTERNET DRAFT July 14, 2000 or more expected policy values, and a criticality indicator. If the node is at depth x, the components of the node have the fol- lowing semantics: (i) The valid_policy is a single policy OID representing a valid policy for the path of length x. (ii) The qualifier_set is a set of policy qualifiers associated 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. (iv) The expected_policy_set contains one or more policy OIDs that would satisfy this policy in the certificate x+1. The initial value of the valid_policy_tree is a single node with valid_policy "any-policy", an empty qualifier_set, an expected_policy_set with the single value "any-policy", and a criticality_indicator of FALSE. This node is considered to be at depth zero. Figure 3 is a graphic representation of the initial state of the valid_policy_tree. Additional figures will use this format to describe changes in the valid_policy_tree during path processing. +-----------------+ | "any-policy" | <---- valid_policy +-----------------+ | {} | <---- qualifier_set +-----------------+ | FALSE | <---- criticality_indicator +-----------------+ | {"any-policy"} | <---- expected_policy_set +-----------------+ Figure 3. Initial value of the valid_policy_tree state variable (b) permitted_subtrees: A set of root names for each name type (e.g., X.500 distinguished names, email addresses, or ip addresses) defining a set of subtrees within which all subject names in subsequent certificates in the certification path shall 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- tinguished names; the initial value for the set of RFC822 names is the set of all RFC822 names, etc. (c) excluded_subtrees: A set of root names for each name type (e.g., X.500 distinguished names, email addresses, or ip addresses) defining a set of subtrees within which no subject name in subsequent certificates in the certification path may fall. This variable includes a set for each name type, and the initial Housley, Ford, Polk, & Solo [Page 60] INTERNET DRAFT July 14, 2000 value for each set is "empty". (d) explicit_policy: an integer which indicates if a non-NULL valid_policy_tree is required. The integer indicates the number of non-self-issued certificates to be processed before this require- ment is imposed. Once set, this variable may be decreased, but may not be increased. That is, if a certificate in the path requires a non-NULL valid_policy_tree, a later certificate can not remove this requirement. If initial-explicit-policy is set, then the ini- tial value is 0, otherwise the initial value is n+1. (e) inhibit_any-policy: an integer which indicates whether the "any-policy" policy identifier is considered a match. The integer indicates the number of non-self-issued certificates to be pro- cessed before the "any-policy" OID, if asserted in a certificate, is ignored. Once set, this variable may be decreased, but may not be increased. That is, if a certificate in the path inhibits pro- cessing of "any-policy", a later certificate can not permit it. If initial-any-policy-inhibit is set, then the initial value is 0, otherwise the initial value is n+1. (f) policy_mapping: an integer which indicates if policy mapping is permitted. The integer indicates the number of non-self-issued certificates to be processed before policy mapping is inhibited. Once set, this variable may be decreased, but may not be increased. That is, if a certificate in the path specifies policy mapping is not permitted, it can not be overridden by a later cer- tificate. If initial-policy-mapping-inhibit is set, then the ini- tial value is 0, otherwise the initial value is n+1. (g) working_public_key_algorithm: the digital signature algorithm used to verify the signature of a certificate. The working_public_key_algorithm is initialized from the trusted pub- lic key algorithm provided in the trust anchor information. (h) working_public_key: the public key used to verify the signa- ture of a certificate. The working_public_key is initialized from the trusted public key provided in the trust anchor information. (i) working_public_key_parameters: parameters associated with the current public key, that may required to verify a signature (depending upon the algorithm). The working_public_key_parameters variable is initialized from the trusted public key parameters provided in the trust anchor information. (j) working_issuer_name: the issuer distinguished name expected in the next certificate in the chain. The working_issuer_name is initialized to the trusted issuer provided in the trust anchor Housley, Ford, Polk, & Solo [Page 61] INTERNET DRAFT July 14, 2000 information. (k) working_issuer_UID: a distinguished name may be associated with an optional unique identifier. The working_issuer_UID is the unique identifier that is expected in the next certificate, or the 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- ficate processing steps specified in 6.1.3. 6.1.3 Basic Certificate Processing The basic path processing actions to be performed for certificate i are listed below. (a) Verify the basic certificate information. The certificate must satisfy each of the following: (1) The certificate was signed with the working_public_key_algorithm using the working_public_key and the working_public_key_parameters. (2) The certificate validity period includes time T. (3) At time T, the certificate is not revoked and is not on hold status. This may be determined by obtaining the appropri- ate CRL (see section 6.3), status information, or by out-of- band mechanisms. (4) The certificate issuer name is the working_issuer_name. (5) The certificate issuer unique identifier is the working_issuer_UID, meaning: (i) working_issuer_UID is non-null and matches the value in the issuerUID field, or (ii) working_issuer_UID is null and the issuerUID field is not present. (b) If certificate i is not self-issued, verify that the subject name is within one of the permitted_subtrees for X.500 dis- tinguished names, and verify that each of the alternative names in the subjectAltName extension (critical or non-critical) is within Housley, Ford, Polk, & Solo [Page 62] INTERNET DRAFT July 14, 2000 one of the permitted_subtrees for that name type. (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- tinguished names, and verify that each of the alternative names in the subjectAltName extension (critical or non-critical) is not within one of the excluded_subtrees for that name type. (d) If the certificate policies extension is present in the certi- ficiate and the valid_policy_tree is not NULL, process the policy information by performing the following steps in order: (1) For each policy P not equal to "any-policy" in the certifi- cate policies extension, let P-OID denote the OID in policy P and P-Q denote the qualifier set for policy P. Perform the following steps in order: (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 node as follows: set the valid_policy to OID- P; set the qualifier_set to P-Q, and set the expected_policy_set to {P-OID}. For example, consider a valid_policy_tree with a node of depth i-1 where the expected_policy_set is {Gold, White}. Assume the certificate policies Gold and Silver appear in the certificate policies extension of certificate i. The Gold policy is matched but the Silver policy is not. This rule will generate a child node of depth i for the Gold pol- icy. The result is shown as Figure 4. Housley, Ford, Polk, & Solo [Page 63] INTERNET DRAFT July 14, 2000 |-----------------| | Red | |-----------------| | {} | |-----------------| node of depth i-1 | FALSE | |-----------------| | {Gold, White} | |-----------------| | | | V |-----------------| | Gold | |-----------------| | {} | |-----------------| node of depth i | uninitialized | |-----------------| | {Gold} | |-----------------| Figure 4. Processing an exact match (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 "any-policy", generate a child node with the following values: set the valid_policy to P-OID; set the qualifier_set to P-Q, and set the expected_policy_set to {P-OID}. For example, consider a valid_policy_tree with a node of depth i-1 where the valid_policy is "any-policy". Assume the certificate policies Gold and Silver appear in the certifi- cate policies extension of certificate i. The Gold policy does not have a qualifier, but the Silver policy has the qualifier Q-Silver. If Gold and Silver were not matched in (i) above, this rule will generate two child nodes of depth i, one for each policy. The result is shown as Figure 5. Housley, Ford, Polk, & Solo [Page 64] INTERNET DRAFT July 14, 2000 |-----------------| | "any-policy" | |-----------------| | {} | |-----------------| node of depth i-1 | FALSE | |-----------------| | {"any-policy"} | |-----------------| / \ / \ / \ / \ |-----------------| |-----------------| | Gold | | Silver | |-----------------| |-----------------| | {} | | {Q-Silver} | |-----------------| nodes of |-----------------| | uninitialized | depth i | uninitialized | |-----------------| |-----------------| | {Gold} | | {Silver} | |-----------------| |-----------------| Figure 5. Processing unmatched policies when a leaf node specifies "any-policy" (2) If the certificate policies extension includes the pol- icy "any-policy" with the qualifier set AP-Q and inhibit_any-policy is greater than 0, then: For each node in the valid_policy_tree of depth i-1, for each value in the expected_policy_set (including "any- policy") that does not appear in a child node, create a child node with the following values: set the valid_policy to the value from the expected_policy_set in the parent node; set the qualifier_set to AP-Q, and set the expected_policy_set to the value in the valid_policy from this node. For example, consider a valid_policy_tree with a node of depth i-1 where the expected_policy_set = {Gold, Silver}. Assume "any-policy" appears in the certificate policies extension of certificate i, but Gold and Silver do not. This rule will generate two child nodes of depth i, one for each policy. The result is shown below as Figure 6. Housley, Ford, Polk, & Solo [Page 65] INTERNET DRAFT July 14, 2000 |-----------------| | Red | |-----------------| | {} | |-----------------| node of depth i-1 | FALSE | |-----------------| | {Gold, Silver} | |-----------------| / \ / \ / \ / \ |-----------------| |-----------------| | Gold | | Silver | |-----------------| |-----------------| | {} | | {} | |-----------------| nodes of |-----------------| | uninitialized | depth i | uninitialized | |-----------------| |-----------------| | {Gold} | | {Silver} | |-----------------| |-----------------| Figure 6. Processing unmatched policies when the certificate policies extension specifies "any-policy" (3) If there is a node in the valid_policy_tree of depth i-1 or less without any child nodes, delete that node. Repeat this step until there are no nodes of depth i-1 or less without children. For example, consider the valid_policy_tree shown in Figure 7 below. The two nodes at depth i-1 that are marked with an to the resulting tree will cause the node at depth i-2 that is marked with an 'Y' to be deleted. The following applica- tion of the rule does not cause any nodes to be deleted, and this step is complete. Housley, Ford, Polk, & Solo [Page 66] INTERNET DRAFT July 14, 2000 +-----------+ | | node of depth i-3 +-----------+ / | \ / | \ / | \ / | \ +-----------+ +-----------+ +-----------+ | | | | | Y | nodes of +-----------+ +-----------+ +-----------+ depth i-2 / \ \ \ / \ \ \ +-----------+ +-----------+ +-----------+ +-----------+ nodes of | | | X | | | | X | depth +-----------+ +-----------+ +-----------+ +-----------+ i-1 | / | \ | / | \ | / | \ +-----------+ +-----------+ +-----------+ +-----------+ nodes of | | | | | | | | depth +-----------+ +-----------+ +-----------+ +-----------+ i Figure 7. Pruning the valid_policy_tree (4) If the certificate policies extension was marked as criti- cal, set the criticality_indicator in all nodes of depth i to TRUE. If the certificate policies extension was not marked critical, set the criticality_indicator in all nodes of depth i to FALSE. (e) If the certificate policies extension is not present, set the valid_policy_tree to NULL. (f) verify that either explicit_policy is greater than 0 or the valid_policy_tree is not equal to NULL; If any of steps (a), (b), (c), or (f) fails, the procedure ter- minates, returning a failure indication and an appropriate reason. 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 6.1.5. 6.1.4 Preparation for Certificate i+1 To prepare for processing of certificate i+1, perform the following Housley, Ford, Polk, & Solo [Page 67] INTERNET DRAFT July 14, 2000 steps for certificate i: (a) If a policy mapping extension is present, verify that the spe- cial value "any-policy" does not appear as an issuerDomainPolicy or a subjectDomainPolicy. (b) If a policy mapping extension is present, then for each issuerDomainPolicy ID-P in the policy mapping extension: (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 valid_policy, set expected_policy_set to the set of sub- jectDomainPolicy values that are specified as equivalent to ID-P by the policy mapping extension. (2) If the policy_mapping variable is equal to 0: (i) delete each node of depth i in the valid_policy_tree where ID-P is the valid_policy. (ii) If there is a node in the valid_policy_tree of depth i-1 or less without any child nodes, delete that node. Repeat this step until there are no nodes of depth i-1 or less without children. (c) Assign the certificate subject name to working_issuer_name. (d) Assign the certificate subjectPublicKey to working_public_key. (e) If the subjectPublicKeyInfo field of the certificate contains an algorithm field with non-null parameters, assign the parameters to the working_public_key_parameters variable. If the subjectPublicKeyInfo field of the certificate contains an algorithm field with null parameters or parameters are omitted, compare the certificate subjectPublicKey algorithm to the working_public_key_algorithm. If the certificate subjectPublicKey algorithm and the working_public_key_algorithm are different, set the working_public_key_parameters to null. (f) Assign the certificate subjectPublicKey algorithm to the working_public_key_algorithm variable. (g) If a name constraints extension is included in the certifi- cate, modify the permitted_subtrees and excluded_subtrees state variables as follows: (1) If permittedSubtrees is present in the certificate, set the permitted_subtrees state variable to the intersection of its Housley, Ford, Polk, & Solo [Page 68] INTERNET DRAFT July 14, 2000 previous value and the value indicated in the extension field. If permittedSubtrees does not include a particular name type, the permitted_subtrees state variable is unchanged for that name type. (2) If excludedSubtrees is present in the certificate, set the excluded_subtrees state variable to the union of its previous value and the value indicated in the extension field. If exclu- dedSubtrees does not include a particular name type, the excluded_subtrees state variable is unchanged for that name type. (h) If the issuer and subject names are not identical: (1) If explicit_policy is not 0, decrement explicit_policy 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- icy by 1. (i) If a policy constraints extension is included in the certifi- cate, modify the explicit_policy and policy_mapping state vari- ables as follows: (1) If requireExplicitPolicy is present and is less than explicit_policy, set explicit_policy to the value of requireEx- plicitPolicy. (2) If inhibitPolicyMapping is present and is less than policy_mapping, set policy_mapping to the value of inhibitPoli- cyMapping. (j) If the inhibitAnyPolicy extension is included in the certifi- cate and is less than inhibit_any-policy, set inhibit_any- policy to the value of inhibitAnyPolicy. (k) Verify that the certificate is a CA certificate (as specified in a basicConstraints extension or as verified out-of-band). (l) If the certificate was not self-issued, verify that max_path_length is greater than zero and decrement max_path_length by 1. (m) If pathLengthConstraint is present in the certificate and is less than max_path_length, set max_path_length to the value of pathLengthConstraint. (n) If a key usage extension is present and marked critical, Housley, Ford, Polk, & Solo [Page 69] INTERNET DRAFT July 14, 2000 verify that the keyCertSign bit is set. (o) Recognize and process any other critical extension present in the certificate. If check (a), (k), (l), (n) or (o) fails, the procedure terminates, returning a failure indication and an appropriate reason. If (a), (k), (l), (n) and (o) have completed successfully, increment i and perform the basic certificate processing specified in 6.1.2. 6.1.5 Wrap-up procedure To complete the processing of the end entity certificate, perform the following steps for certificate n: (a) If certificate n was not self-issued and explicit_policy is not 0, decrement explicit_policy by 1. (b) If a policy constraints extension is included in the certifi- cate and requireExplicitPolicy is present and has a value of 0, set the explicit_policy state variable to 0. (c) Assign the certificate subjectPublicKey to working_public_key. (d) If the subjectPublicKeyInfo field of the certificate contains an algorithm field with non-null parameters, assign the parameters to the working_public_key_parameters variable. If the subjectPublicKeyInfo field of the certificate contains an algorithm field with null parameters or parameters are omitted, compare the certificate subjectPublicKey algorithm to the working_public_key_algorithm. If the certificate subjectPublicKey algorithm and the working_public_key_algorithm are different, set the working_public_key_parameters to null. (e) Assign the certificate subjectPublicKey algorithm to the working_public_key_algorithm variable. (f) Recognize and process any other critical extension present in the certificate n. (g) Calculate the intersection of the valid_policy_tree and the user_initial_policy_set, as follows: (i) If the valid_policy_tree is NULL, the intersection is NULL. (ii) If the valid_policy_tree is not NULL and the Housley, Ford, Polk, & Solo [Page 70] INTERNET DRAFT July 14, 2000 user_initial_policy_set is "any-policy", the intersection is the 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: 1. Determine the set of policy nodes whose parent nodes have a valid_policy of "any-policy". This is the valid_policy_node_set. 2. If the valid_policy of any node in the valid_policy_node_set is not in the user_initial_policy_set and is not "any-policy", delete this node and all its chil- dren. 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 this step until there are no nodes of depth n-1 or less without children. Upon completion of all steps, path processing has succeeded if the value of explicit_policy variable is greater than zero, or the valid_policy_tree is not NULL. 6.1.6 Outputs If path processing succeeds, the procedure terminates, returning a success indication together with final value of the valid_policy_tree, the working_public_key, the working_public_key_algorithm, and the working_public_key_parameters. 6.2 Extending Path Validation The path validation algorithm presented in 6.1 is based on several simplifying assumptions (e.g., a single trusted CA that starts all valid paths). This algorithm may be extended for cases where the assumptions do not hold. This procedure may be extended for multiple trusted CAs by providing a set of self-signed certificates to the validation module. In this case, a valid path could begin with any one of the self-signed certi- ficates. Limitations in the trust paths for any particular key may be incorporated into the self-signed certificate's extensions. In this way, the self-signed certificates permit the path validation module to automatically incorporate local security policy and requirements. It is also possible to specify an extended version of the above cer- tification path processing procedure which results in default Housley, Ford, Polk, & Solo [Page 71] INTERNET DRAFT July 14, 2000 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 Policy Certification Authorities (PCAs) names and an indicator of the position in the certification path where the PCA is expected. At the nominated PCA position, the CA name is compared against this list. If a recognized PCA name is found, then a constraint of Subordina- teToCA is implicitly assumed for the remainder of the certification path and processing continues. If no valid PCA name is found, and if the certification path cannot be validated on the basis of identified policies, then the certification path is considered invalid. 6.3 CRL Validation This section describes the steps necessary to determine if a certifi- cate is revoked or on hold status when CRLs are the revocation mechanism used by the certificate issuer. Conforming implementations of this specification are not required to implement this algorithm, but MUST be functionally equivalent to the external behavior result- ing from this procedure. Any algorithm may be used by a particular implementation so long as it derives the correct result. This algorithm defines a set of inputs, a set of state variables, and processing steps that are performed for each certificate in the path. 6.3.1 Revocation Inputs To support revocation processing, the algorithm requires two inputs: (a) certificate: the algorithm requires the certificate serial number and issuer name to determine if a certificate is on a par- ticular CRL. The basicConstraints extension is used to determine whether the supplied certificate is associated with a CA or an end-entity. If present, the algorithm may use the cRLDistribu- tionsPoint and freshestCRL extensions to determine revocation status. (b) use-deltas: This boolean input determines if the delta needs to be checked if the CRL is still valid Note that implementations supporting legacy PKIs, such as RFC 1422 and X.509 version 1, will need an additional input indicating whether the supplied certificate is associated with a CA or an end-entity. 6.3.2 Initialization and Revocation State Variables To support CRL processing, the algorithm requires the following state variables: Housley, Ford, Polk, & Solo [Page 72] INTERNET DRAFT July 14, 2000 (a) reasons_mask: This variable contains the set of revocation reasons supported by the CRLs and delta CRLs processed so far. The legal members of the set are the possible values for reasonflags: unspecified; keyCompromise; caCompromise; affiliationChanged; superseded; cessationOfOperation; and certificateHold. The spe- cial value "all-reasons" is used to denote the set of all legal members. This variable is initialized to the empty set. (b) cert_status: This variable contains the status of the certifi- cate. Legal values are unspecified; keyCompromise; caCompromise; affiliationChanged; superseded; cessationOfOperation; and certifi- cateHold, the special value "UNREVOKED", or the special value "UNDETERMINED". This variable is initialized to the special value "UNREVOKED". (c) interim_reasons_mask: This contains the set of revocation rea- sons supported by the CRL or delta CRL currently being processed. Note: In some environments, it is not necessary to check all reason codes. For example, some envornments only are concerned with caCompromise and keyCompromise for CA certificates. This algorithnm checks all reason codes. Additional processing and state variables may be necessary to limit the checking to a subset of the reason codes. 6.3.3 CRL Processing This algorithm begins by assuming the certificate is not revoked. The algorithm checks one or more CRLs until either the certificate status is determined to be revoked or sufficent CRLs have been checked to cover all reason codes. For each distribution point (DP) in the crl distribution points extension while ((reasons_mask is not "all-reasons") and (cert_status is UNREVOKED)) (1) locate the corresponding CRL in CRL cache, and perform the following verifications: (a) compute the interim_reasons_mask for this CRL as follows: 1. if the CRL includes reasons and the DP includes reasons, then set interim_reasons_mask to the intersection of of rea- sons in the DP and reasons in CRL reasons extension. 2. if the CRL includes reasons but the DP omits reasons, then set interim_reasons_mask to the value of CRL reasons. Housley, Ford, Polk, & Solo [Page 73] INTERNET DRAFT July 14, 2000 3. if the CRL omits reasons but the DP includes reasons, then set interim_reasons_mask to the value of DP reasons. 4. if the CRL omits reasons and the DP omits reasons, then set interim_reasons_mask to the special value "all-reasons". Verify that interim_reasons_mask includes one or more reasons that is not included in the reasons_mask. (b) Verify the issuer of the CRL as follows: if the DP includes cRLIssuer, then verify that the CRL issuer matches cRLIssuer else verify that the CRL issuer matches the certificate issuer. (c) obtain and validate the certification path for the CRL issuer. (d) validate the signature on the CRL. (2) If each of the verifications (a) through (d) succeeds, then perform the following steps: (a) If the value of next update field is before the current- time, otain an appropriate delta CRL or discard the CRL. (b) If the user wants freshest available info AND the freshest CRL extension is present, check for a corresponding delta for this base. (c) If a delta was obtained in (a) or (b), verify that the delta CRL addresses the same set of certificates and the same set of reasons as the CRL. (d) Perform the checks in step 1 (b) and (c): 1. obtain and validate the certification path for the delta issuer 2. validate the signature on the delta CRL (e) If a delta CRL was obtained in (a) or (b), and the verifications (c) and (d) suceeded, combine the base and delta to form a complete CRL. (3) If steps and (1) and (2) succeed, then set reasons_mask to the union of reasons_mask and interim_reasons_mask Housley, Ford, Polk, & Solo [Page 74] INTERNET DRAFT July 14, 2000 (4) Search for the certificate on the CRL (a) search for the serial number on the CRL (b) if (a) succeeds, verify that (1) the CRL entry extension Certificate issuer is not present or (2) the issuer identified in the CRL entry extension Certificate issuer is the issuer of the certificate. (c) if (a) and (b) succeeded, set the cert_status variable as appropriate: 1. if the reasons extension is present, set the cert_status variable to the value of the reasons extension 2. if the reasons extension is not present, set the cert_status variable to the special value "not specified" if ((reasons_mask is "all-reasons") OR (if cert_status is not UNREVOKED) return cert_status If all CRLs named in the crl distribution points extension have been exhausted, and the reasons_mask is not "all-reasons" and the cert_status is still UNREVOKED, the verifier must obtain addi- tional CRLs. If the The verifier must repeat the process above with the additional CRLs not specified in a distribution point. If all CRLs are exhausted and the reasons_mask is not "all rea- sons" return the cert_status UNDETERMINED. 7 References [RFC 791] J. Postel, "Internet Protocol", September 1981. [RFC 822] D. Crocker, "Standard for the format of ARPA Internet text messages", August 1982. [RFC 1034] P.V. Mockapetris, "Domain names - concepts and facilities", November 1987. [RFC 1422] Kent, S., "Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management," RFC 1422, BBN Communications, February 1993. [RFC 1423] Balenson, D., "Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers," Housley, Ford, Polk, & Solo [Page 75] INTERNET DRAFT July 14, 2000 RFC 1423, Trusted Information Systems, February 1993. [RFC 1510] Kohl, J., and C. Neuman, "The Kerberos Network Authentication Service (V5)," RFC 1510, September 1993. [RFC 1519] V. Fuller, T. Li, J. Yu, and K. Varadhan. "Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy", September 1993. [RFC 1738] Berners-Lee, T., Masinter L., and M. McCahill. "Uniform Resource Locators (URL)", RFC 1738, December 1994. [RFC 1778] Howes, T., Kille S., Yeong, W. and C. Robbins. "The String Representation of Standard Attribute Syntaxes," RFC 1778, March 1995. [RFC 1883] S. Deering and R. Hinden. "Internet Protocol, Version 6 (IPv6) Specification", December 1995. [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [RFC 2247] Kille, S., Wahl, M., Grimstad, A., Huber, R. and S. Sataluri. "Using Domains in LDAP/X.500 Distinguished Names", RFC 2247, January 1998. [RFC 2277] H. Alvestrand, "IETF Policy on Character Sets and Languages", January 1998. [RFC 2279] F. Yergeau, "UTF-8, a transformation format of ISO 10646", January 1998. [RFC 2560] Myers, M., Ankney R., Malpani A., Galperin S., and C. Adams, "Online Certificate Status Protocal - OCSP", June 1999. [SDN.701] SDN.701, "Message Security Protocol 4.0", Revision A 1997-02-06. [X.208] CCITT Recommendation X.208: Specification of Abstract Syntax Notation One (ASN.1), 1988. [X.501] ITU-T Recommendation X.501: Information Technology - Open Systems Interconnection - The Directory: Models, 1993. [X.509] ITU-T Recommendation X.509 (1997 E): Information Technology - Open Systems Interconnection - The Housley, Ford, Polk, & Solo [Page 76] INTERNET DRAFT July 14, 2000 Directory: Authentication Framework, June 1997. [X.520] ITU-T Recommendation X.520: Information Technology - Open Systems Interconnection - The Directory: Selected Attribute Types, 1993. [X9.55] ANSI X9.55-1995, Public Key Cryptography For The Financial Services Industry: Extensions To Public Key Certificates And Certificate Revocation Lists, 8 December, 1995. [PKINIT] Tung, B., Neuman C., Hur M., Medvinsky A., Medvinsky S., Wray J., and J. Trostle, "Public Key Cryptography for Initial Authentciaion in Kerberos," draft-ietf-cat-kerberos-pk-init-11.txt, March 15, 2000. [PKIX ALGS] Bassham, L., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Representation of Public Keys and Digital Signatures," draft-ietf-pkix-ipki-pkalgs-00.txt, July 14, 2000. 8 Intellectual Property Rights The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this docu- ment. For more information consult the online list of claimed rights. The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to per- tain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards- related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. 9 Security Considerations The majority of this specification is devoted to the format and con- tent of certificates and CRLs. Since certificates and CRLs are digi- tally signed, no additional integrity service is necessary. Neither certificates nor CRLs need be kept secret, and unrestricted and anonymous access to certificates and CRLs has no security Housley, Ford, Polk, & Solo [Page 77] INTERNET DRAFT July 14, 2000 implications. However, security factors outside the scope of this specification will affect the assurance provided to certificate users. This sec- tion highlights critical issues that should be considered by imple- mentors, administrators, and users. The procedures performed by CAs and RAs to validate the binding of the subject's identity of their public key greatly affect the assurance that should be placed in the certificate. Relying parties may wish to review the CA's certificate practice statement. This may be particularly important when issuing certificates to other CAs. 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 management provides several benefits to the users. The ramifications associated with loss or disclosure of a signature key are different from loss or disclosure of a key management key. Using separate key pairs permits a balanced and flexible response. Similarly, different validity periods or key lengths for each key pair may be appropriate in some application environments. Unfortunately, some legacy applica- tions (e.g., SSL) use a single key pair for signature and key manage- ment. The protection afforded private keys is a critical factor in main- taining security. On a small scale, failure of users to protect their private keys will permit an attacker to masquerade as them, or decrypt their personal information. On a larger scale, compromise of a CA's private signing key may have a catastrophic effect. If an attacker obtains the private key unnoticed, the attacker may issue bogus certificates and CRLs. Existence of bogus certificates and CRLs will undermine confidence in the system. If the compromise is detected, all certificates issued to the CA shall be revoked, preventing services between its users and users of other CAs. Rebuilding after such a compromise will be problematic, so CAs are advised to implement a combination of strong technical measures (e.g., tamper-resistant cryptographic modules) and appropriate management procedures (e.g., separation of duties) to avoid such an incident. 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. CAs are advised to maintain secure backup for signing keys. The security of the key backup procedures is a critical factor in avoid- ing key compromise. The availability and freshness of revocation information will affect the degree of assurance that should be placed in a certificate. Housley, Ford, Polk, & Solo [Page 78] INTERNET DRAFT July 14, 2000 While certificates expire naturally, events may occur during its natural lifetime which negate the binding between the subject and public key. If revocation information is untimely or unavailable, the assurance associated with the binding is clearly reduced. Simi- larly, implementations of the Path Validation mechanism described in section 6 that omit revocation checking provide less assurance than those that support it. The path validation algorithm depends on the certain knowledge of the public keys (and other information) about one or more trusted CAs. The decision to trust a CA is an important decision as it ultimately determines the trust afforded a certificate. The authenticated dis- tribution of trusted CA public keys (usually in the form of a "self- signed" certificate) is a security critical out of band process that is beyond the scope of this specification. In addition, where a key compromise or CA failure occurs for a trusted CA, the user will need to modify the information provided to the path validation routine. Selection of too many trusted CAs will make the trusted CA information difficult to maintain. On the other hand, selection of only one trusted CA may limit users to a closed community of users until a global PKI emerges. The quality of implementations that process certificates may also affect the degree of assurance provided. The path validation algo- rithm described in section 6 relies upon the integrity of the trusted CA information, and especially the integrity of the public keys asso- ciated with the trusted CAs. By substituting public keys for which an attacker has the private key, an attacker could trick the user into accepting false certificates. The binding between a key and certificate subject cannot be stronger than the cryptographic module implementation and algorithms used to generate the signature. Short key lengths or weak hash algorithms will limit the utility of a certificate. CAs are encouraged to note advances in cryptology so they can employ strong cryptographic tech- niques. In addition, CAs should decline to issue certificates to CAs or end entities that generate weak signatures. Inconsistent application of name comparison rules may result in acceptance of invalid X.509 certification paths, or rejection of valid ones. The X.500 series of specifications defines rules for comparing distinguished names require comparison of strings without regard to case, character set, multi-character white space substring, or leading and trailing white space. This specification relaxes these requirements, requiring support for binary comparison at a minimum. Housley, Ford, Polk, & Solo [Page 79] INTERNET DRAFT July 14, 2000 CAs shall encode the distinguished name in the subject field of a CA certificate identically to the distinguished name in the issuer field in certificates issued by the latter CA. If CAs use different encod- ings, implementations of this specification may fail to recognize name chains for paths that include this certificate. As a conse- quence, valid paths could be rejected. In addition, name constraints for distinguished names shall be stated identically to the encoding used in the subject field or subjectAlt- Name extension. If not, (1) name constraints stated as excludedSub- Trees will not match and invalid paths will be accepted and (2) name constraints expressed as permittedSubtrees will not match and valid paths will be rejected. To avoid acceptance of invalid paths, CAs should state name constraints for distinguished names as permit- tedSubtrees where ever possible. Housley, Ford, Polk, & Solo [Page 80] INTERNET DRAFT July 14, 2000 Appendix A. Psuedo-ASN.1 Structures and OIDs 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 1993 ASN.1 syntaxes. The 1988 ASN.1 syntax is augmented with 1993 UNIVERSAL Types UniversalString, BMPString and UTF8String. 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 new UNIVERSAL types in modules using the 1988 syntax. As a result, this module does not conform to either version of the ASN.1 standard. This appendix may be converted into 1988 ASN.1 by replacing the defintions for the UNIVERSAL Types with the 1988 catch-all "ANY". A.1 Explicitly Tagged Module, 1988 Syntax PKIX1Explicit88 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit-88(1)} DEFINITIONS EXPLICIT TAGS ::= BEGIN -- EXPORTS ALL -- -- IMPORTS NONE -- -- UNIVERSAL Types defined in '93 and '98 ASN.1 -- but required by this specification UniversalString ::= [UNIVERSAL 28] IMPLICIT OCTET STRING -- UniversalString is defined in ASN.1:1993 BMPString ::= [UNIVERSAL 30] IMPLICIT OCTET STRING -- BMPString is the subtype of UniversalString and models -- the Basic Multilingual Plane of ISO/IEC/ITU 10646-1 UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING -- The content of this type conforms to RFC 2279. -- -- PKIX specific OIDs id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) Housley, Ford, Polk, & Solo [Page 81] INTERNET DRAFT July 14, 2000 security(5) mechanisms(5) pkix(7) } -- PKIX arcs id-pe OBJECT IDENTIFIER ::= { id-pkix 1 } -- arc for private certificate extensions id-qt OBJECT IDENTIFIER ::= { id-pkix 2 } -- arc for policy qualifier types id-kp OBJECT IDENTIFIER ::= { id-pkix 3 } -- arc for extended key purpose OIDS id-ad OBJECT IDENTIFIER ::= { id-pkix 48 } -- arc for access descriptors -- policyQualifierIds for Internet policy qualifiers id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 } -- OID for CPS qualifier id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 } -- OID for user notice qualifier -- access descriptor definitions id-ad-ocsp OBJECT IDENTIFIER ::= { id-ad 1 } id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 } -- attribute data types -- Attribute ::= SEQUENCE { type AttributeType, values SET OF AttributeValue -- at least one value is required -- } AttributeType ::= OBJECT IDENTIFIER AttributeValue ::= ANY AttributeTypeAndValue ::= SEQUENCE { type AttributeType, value AttributeValue } -- suggested naming attributes: Definition of the following -- information object set may be augmented to meet local -- requirements. Note that deleting members of the set may -- prevent interoperability with conforming implementations. -- presented in pairs: the AttributeType followed by the -- type definition for the corresponding AttributeValue --Arc for standard naming attributes id-at OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 4} Housley, Ford, Polk, & Solo [Page 82] INTERNET DRAFT July 14, 2000 -- Attributes of type NameDirectoryString id-at-name AttributeType ::= {id-at 41} id-at-surname AttributeType ::= {id-at 4} id-at-givenName AttributeType ::= {id-at 42} id-at-initials AttributeType ::= {id-at 43} id-at-generationQualifier AttributeType ::= {id-at 44} X520name ::= CHOICE { teletexString TeletexString (SIZE (1..ub-name)), printableString PrintableString (SIZE (1..ub-name)), universalString UniversalString (SIZE (1..ub-name)), utf8String UTF8String (SIZE (1..ub-name)), bmpString BMPString (SIZE(1..ub-name)) } -- id-at-commonName AttributeType ::= {id-at 3} X520CommonName ::= CHOICE { teletexString TeletexString (SIZE (1..ub-common-name)), printableString PrintableString (SIZE (1..ub-common-name)), universalString UniversalString (SIZE (1..ub-common-name)), utf8String UTF8String (SIZE (1..ub-common-name)), bmpString BMPString (SIZE(1..ub-common-name)) } -- id-at-localityName AttributeType ::= {id-at 7} X520LocalityName ::= CHOICE { teletexString TeletexString (SIZE (1..ub-locality-name)), printableString PrintableString (SIZE (1..ub-locality-name)), universalString UniversalString (SIZE (1..ub-locality-name)), utf8String UTF8String (SIZE (1..ub-locality-name)), bmpString BMPString (SIZE(1..ub-locality-name)) } -- id-at-stateOrProvinceName AttributeType ::= {id-at 8} X520StateOrProvinceName ::= CHOICE { teletexString TeletexString (SIZE (1..ub-state-name)), printableString PrintableString (SIZE (1..ub-state-name)), universalString UniversalString (SIZE (1..ub-state-name)), utf8String UTF8String (SIZE (1..ub-state-name)), bmpString BMPString (SIZE(1..ub-state-name)) } Housley, Ford, Polk, & Solo [Page 83] INTERNET DRAFT July 14, 2000 -- id-at-organizationName AttributeType ::= {id-at 10} X520OrganizationName ::= CHOICE { teletexString TeletexString (SIZE (1..ub-organization-name)), printableString PrintableString (SIZE (1..ub-organization-name)), universalString UniversalString (SIZE (1..ub-organization-name)), utf8String UTF8String (SIZE (1..ub-organization-name)), bmpString BMPString (SIZE(1..ub-organization-name)) } -- id-at-organizationalUnitName AttributeType ::= {id-at 11} X520OrganizationalUnitName ::= CHOICE { teletexString TeletexString (SIZE (1..ub-organizational-unit-name)), printableString PrintableString (SIZE (1..ub-organizational-unit-name)), universalString UniversalString (SIZE (1..ub-organizational-unit-name)), utf8String UTF8String (SIZE (1..ub-organizational-unit-name)), bmpString BMPString (SIZE(1..ub-organizational-unit-name)) } -- id-at-title AttributeType ::= {id-at 12} X520Title ::= CHOICE { teletexString TeletexString (SIZE (1..ub-title)), printableString PrintableString (SIZE (1..ub-title)), universalString UniversalString (SIZE (1..ub-title)), utf8String UTF8String (SIZE (1..ub-title)), bmpString BMPString (SIZE(1..ub-title)) } -- id-at-dnQualifier AttributeType ::= {id-at 46} X520dnQualifier ::= PrintableString id-at-countryName AttributeType ::= {id-at 6} X520countryName ::= PrintableString (SIZE (2)) -- IS 3166 codes id-at-serialNumber AttributeType ::= { id-at 5 } X520SerialNumber PrintableString (SIZE (1..ub-serial-number)) -- domaincomponent and identifier from RFC 2247 Housley, Ford, Polk, & Solo [Page 84] INTERNET DRAFT July 14, 2000 id-domainComponent OBJECT IDENTIFIER := { 0 9 2342 19200300 100 1 25 } id-domainComponent AttributeType ::= id-domainComponent domainComponent ::= IA5String -- Legacy attributes pkcs-9 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 9 } emailAddress AttributeType ::= { pkcs-9 1 } Pkcs9email ::= IA5String (SIZE (1..ub-emailaddress-length)) -- naming data types -- Name ::= CHOICE { -- only one possibility for now -- rdnSequence RDNSequence } RDNSequence ::= SEQUENCE OF RelativeDistinguishedName DistinguishedName ::= RDNSequence RelativeDistinguishedName ::= SET SIZE (1 .. MAX) OF AttributeTypeAndValue -- Directory string type -- DirectoryString ::= CHOICE { teletexString TeletexString (SIZE (1..MAX)), printableString PrintableString (SIZE (1..MAX)), universalString UniversalString (SIZE (1..MAX)), utf8String UTF8String (SIZE (1..MAX)), bmpString BMPString (SIZE(1..MAX)) } -- certificate and CRL specific structures begin here Certificate ::= SEQUENCE { tbsCertificate TBSCertificate, signatureAlgorithm AlgorithmIdentifier, signature BIT STRING } TBSCertificate ::= SEQUENCE { version [0] Version DEFAULT v1, serialNumber CertificateSerialNumber, signature AlgorithmIdentifier, issuer Name, Housley, Ford, Polk, & Solo [Page 85] INTERNET DRAFT July 14, 2000 validity Validity, subject Name, subjectPublicKeyInfo SubjectPublicKeyInfo, issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL, -- If present, version shall be v2 or v3 subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL, -- If present, version shall be v2 or v3 extensions [3] Extensions OPTIONAL -- If present, version shall be v3 -- } Version ::= INTEGER { v1(0), v2(1), v3(2) } CertificateSerialNumber ::= INTEGER Validity ::= SEQUENCE { notBefore Time, notAfter Time } Time ::= CHOICE { utcTime UTCTime, generalTime GeneralizedTime } UniqueIdentifier ::= BIT STRING SubjectPublicKeyInfo ::= SEQUENCE { algorithm AlgorithmIdentifier, subjectPublicKey BIT STRING } Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension Extension ::= SEQUENCE { extnID OBJECT IDENTIFIER, critical BOOLEAN DEFAULT FALSE, extnValue OCTET STRING } -- CRL structures CertificateList ::= SEQUENCE { tbsCertList TBSCertList, signatureAlgorithm AlgorithmIdentifier, signature BIT STRING } TBSCertList ::= SEQUENCE { version Version OPTIONAL, -- if present, shall be v2 signature AlgorithmIdentifier, issuer Name, thisUpdate Time, Housley, Ford, Polk, & Solo [Page 86] INTERNET DRAFT July 14, 2000 nextUpdate Time OPTIONAL, revokedCertificates SEQUENCE OF SEQUENCE { userCertificate CertificateSerialNumber, revocationDate Time, crlEntryExtensions Extensions OPTIONAL -- if present, shall be v2 } OPTIONAL, crlExtensions [0] Extensions OPTIONAL -- if present, shall be v2 -- } -- Version, Time, CertificateSerialNumber, and Extensions were -- defined earlier for use in the certificate structure AlgorithmIdentifier ::= SEQUENCE { algorithm OBJECT IDENTIFIER, parameters ANY DEFINED BY algorithm OPTIONAL } -- contains a value of the type -- registered for use with the -- algorithm object identifier value -- x400 address syntax starts here -- OR Names ORAddress ::= SEQUENCE { built-in-standard-attributes BuiltInStandardAttributes, built-in-domain-defined-attributes BuiltInDomainDefinedAttributes OPTIONAL, -- see also teletex-domain-defined-attributes extension-attributes ExtensionAttributes OPTIONAL } -- The OR-address is semantically absent from the OR-name if the -- built-in-standard-attribute sequence is empty and the -- built-in-domain-defined-attributes and extension-attributes are -- both omitted. -- Built-in Standard Attributes BuiltInStandardAttributes ::= SEQUENCE { country-name CountryName OPTIONAL, administration-domain-name AdministrationDomainName OPTIONAL, network-address [0] NetworkAddress OPTIONAL, -- see also extended-network-address terminal-identifier [1] TerminalIdentifier OPTIONAL, private-domain-name [2] PrivateDomainName OPTIONAL, organization-name [3] OrganizationName OPTIONAL, -- see also teletex-organization-name numeric-user-identifier [4] NumericUserIdentifier OPTIONAL, personal-name [5] PersonalName OPTIONAL, -- see also teletex-personal-name Housley, Ford, Polk, & Solo [Page 87] INTERNET DRAFT July 14, 2000 organizational-unit-names [6] OrganizationalUnitNames OPTIONAL -- see also teletex-organizational-unit-names -- } CountryName ::= [APPLICATION 1] CHOICE { x121-dcc-code NumericString (SIZE (ub-country-name-numeric-length)), iso-3166-alpha2-code PrintableString (SIZE (ub-country-name-alpha-length)) } AdministrationDomainName ::= [APPLICATION 2] CHOICE { numeric NumericString (SIZE (0..ub-domain-name-length)), printable PrintableString (SIZE (0..ub-domain-name-length)) } NetworkAddress ::= X121Address -- see also extended-network-address X121Address ::= NumericString (SIZE (1..ub-x121-address-length)) TerminalIdentifier ::= PrintableString (SIZE (1..ub-terminal-id-length)) PrivateDomainName ::= CHOICE { numeric NumericString (SIZE (1..ub-domain-name-length)), printable PrintableString (SIZE (1..ub-domain-name-length)) } OrganizationName ::= PrintableString (SIZE (1..ub-organization-name-length)) -- see also teletex-organization-name NumericUserIdentifier ::= NumericString (SIZE (1..ub-numeric-user-id-length)) PersonalName ::= SET { surname [0] PrintableString (SIZE (1..ub-surname-length)), given-name [1] PrintableString (SIZE (1..ub-given-name-length)) OPTIONAL, initials [2] PrintableString (SIZE (1..ub-initials-length)) OPTIONAL, generation-qualifier [3] PrintableString (SIZE (1..ub-generation-qualifier-length)) OPTIONAL } -- see also teletex-personal-name OrganizationalUnitNames ::= SEQUENCE SIZE (1..ub-organizational-units) OF OrganizationalUnitName -- see also teletex-organizational-unit-names OrganizationalUnitName ::= PrintableString (SIZE (1..ub-organizational-unit-name-length)) -- Built-in Domain-defined Attributes Housley, Ford, Polk, & Solo [Page 88] INTERNET DRAFT July 14, 2000 BuiltInDomainDefinedAttributes ::= SEQUENCE SIZE (1..ub-domain-defined-attributes) OF BuiltInDomainDefinedAttribute BuiltInDomainDefinedAttribute ::= SEQUENCE { type PrintableString (SIZE (1..ub-domain-defined-attribute-type-length)), value PrintableString (SIZE (1..ub-domain-defined-attribute-value-length))} -- Extension Attributes ExtensionAttributes ::= SET SIZE (1..ub-extension-attributes) OF ExtensionAttribute ExtensionAttribute ::= SEQUENCE { extension-attribute-type [0] INTEGER (0..ub-extension-attributes), extension-attribute-value [1] ANY DEFINED BY extension-attribute-type } -- Extension types and attribute values -- common-name INTEGER ::= 1 CommonName ::= PrintableString (SIZE (1..ub-common-name-length)) teletex-common-name INTEGER ::= 2 TeletexCommonName ::= TeletexString (SIZE (1..ub-common-name-length)) teletex-organization-name INTEGER ::= 3 TeletexOrganizationName ::= TeletexString (SIZE (1..ub-organization-name-length)) teletex-personal-name INTEGER ::= 4 TeletexPersonalName ::= SET { surname [0] TeletexString (SIZE (1..ub-surname-length)), given-name [1] TeletexString (SIZE (1..ub-given-name-length)) OPTIONAL, initials [2] TeletexString (SIZE (1..ub-initials-length)) OPTIONAL, generation-qualifier [3] TeletexString (SIZE (1..ub-generation-qualifier-length)) OPTIONAL } teletex-organizational-unit-names INTEGER ::= 5 Housley, Ford, Polk, & Solo [Page 89] INTERNET DRAFT July 14, 2000 TeletexOrganizationalUnitNames ::= SEQUENCE SIZE (1..ub-organizational-units) OF TeletexOrganizationalUnitName TeletexOrganizationalUnitName ::= TeletexString (SIZE (1..ub-organizational-unit-name-length)) pds-name INTEGER ::= 7 PDSName ::= PrintableString (SIZE (1..ub-pds-name-length)) physical-delivery-country-name INTEGER ::= 8 PhysicalDeliveryCountryName ::= CHOICE { x121-dcc-code NumericString (SIZE (ub-country-name-numeric-length)), iso-3166-alpha2-code PrintableString (SIZE (ub-country-name-alpha-length)) } postal-code INTEGER ::= 9 PostalCode ::= CHOICE { numeric-code NumericString (SIZE (1..ub-postal-code-length)), printable-code PrintableString (SIZE (1..ub-postal-code-length)) } physical-delivery-office-name INTEGER ::= 10 PhysicalDeliveryOfficeName ::= PDSParameter physical-delivery-office-number INTEGER ::= 11 PhysicalDeliveryOfficeNumber ::= PDSParameter extension-OR-address-components INTEGER ::= 12 ExtensionORAddressComponents ::= PDSParameter physical-delivery-personal-name INTEGER ::= 13 PhysicalDeliveryPersonalName ::= PDSParameter physical-delivery-organization-name INTEGER ::= 14 PhysicalDeliveryOrganizationName ::= PDSParameter extension-physical-delivery-address-components INTEGER ::= 15 ExtensionPhysicalDeliveryAddressComponents ::= PDSParameter unformatted-postal-address INTEGER ::= 16 Housley, Ford, Polk, & Solo [Page 90] INTERNET DRAFT July 14, 2000 UnformattedPostalAddress ::= SET { printable-address SEQUENCE SIZE (1..ub-pds-physical-address-lines) OF PrintableString (SIZE (1..ub-pds-parameter-length)) OPTIONAL, teletex-string TeletexString (SIZE (1..ub-unformatted-address-length)) OPTIONAL } street-address INTEGER ::= 17 StreetAddress ::= PDSParameter post-office-box-address INTEGER ::= 18 PostOfficeBoxAddress ::= PDSParameter poste-restante-address INTEGER ::= 19 PosteRestanteAddress ::= PDSParameter unique-postal-name INTEGER ::= 20 UniquePostalName ::= PDSParameter local-postal-attributes INTEGER ::= 21 LocalPostalAttributes ::= PDSParameter PDSParameter ::= SET { printable-string PrintableString (SIZE(1..ub-pds-parameter-length)) OPTIONAL, teletex-string TeletexString (SIZE(1..ub-pds-parameter-length)) OPTIONAL } extended-network-address INTEGER ::= 22 ExtendedNetworkAddress ::= CHOICE { e163-4-address SEQUENCE { number [0] NumericString (SIZE (1..ub-e163-4-number-length)), sub-address [1] NumericString (SIZE (1..ub-e163-4-sub-address-length)) OPTIONAL }, psap-address [0] PresentationAddress } PresentationAddress ::= SEQUENCE { pSelector [0] EXPLICIT OCTET STRING OPTIONAL, sSelector [1] EXPLICIT OCTET STRING OPTIONAL, tSelector [2] EXPLICIT OCTET STRING OPTIONAL, nAddresses [3] EXPLICIT SET SIZE (1..MAX) OF OCTET STRING } terminal-type INTEGER ::= 23 Housley, Ford, Polk, & Solo [Page 91] INTERNET DRAFT July 14, 2000 TerminalType ::= INTEGER { telex (3), teletex (4), g3-facsimile (5), g4-facsimile (6), ia5-terminal (7), videotex (8) } (0..ub-integer-options) -- Extension Domain-defined Attributes teletex-domain-defined-attributes INTEGER ::= 6 TeletexDomainDefinedAttributes ::= SEQUENCE SIZE (1..ub-domain-defined-attributes) OF TeletexDomainDefinedAttribute TeletexDomainDefinedAttribute ::= SEQUENCE { type TeletexString (SIZE (1..ub-domain-defined-attribute-type-length)), value TeletexString (SIZE (1..ub-domain-defined-attribute-value-length)) } -- specifications of Upper Bounds shall be regarded as mandatory -- from Annex B of ITU-T X.411 Reference Definition of MTS Parameter -- Upper Bounds -- Upper Bounds ub-name INTEGER ::= 32768 ub-common-name INTEGER ::= 64 ub-locality-name INTEGER ::= 128 ub-state-name INTEGER ::= 128 ub-organization-name INTEGER ::= 64 ub-organizational-unit-name INTEGER ::= 64 ub-title INTEGER ::= 64 ub-serialNumber INTEGER ::= 64 ub-match INTEGER ::= 128 ub-emailaddress-length INTEGER ::= 128 ub-common-name-length INTEGER ::= 64 ub-country-name-alpha-length INTEGER ::= 2 ub-country-name-numeric-length INTEGER ::= 3 ub-domain-defined-attributes INTEGER ::= 4 ub-domain-defined-attribute-type-length INTEGER ::= 8 ub-domain-defined-attribute-value-length INTEGER ::= 128 ub-domain-name-length INTEGER ::= 16 ub-extension-attributes INTEGER ::= 256 ub-e163-4-number-length INTEGER ::= 15 ub-e163-4-sub-address-length INTEGER ::= 40 Housley, Ford, Polk, & Solo [Page 92] INTERNET DRAFT July 14, 2000 ub-generation-qualifier-length INTEGER ::= 3 ub-given-name-length INTEGER ::= 16 ub-initials-length INTEGER ::= 5 ub-integer-options INTEGER ::= 256 ub-numeric-user-id-length INTEGER ::= 32 ub-organization-name-length INTEGER ::= 64 ub-organizational-unit-name-length INTEGER ::= 32 ub-organizational-units INTEGER ::= 4 ub-pds-name-length INTEGER ::= 16 ub-pds-parameter-length INTEGER ::= 30 ub-pds-physical-address-lines INTEGER ::= 6 ub-postal-code-length INTEGER ::= 16 ub-surname-length INTEGER ::= 40 ub-terminal-id-length INTEGER ::= 24 ub-unformatted-address-length INTEGER ::= 180 ub-x121-address-length INTEGER ::= 16 -- Note - upper bounds on string types, such as TeletexString, are -- measured in characters. Excepting PrintableString or IA5String, a -- significantly greater number of octets will be required to hold -- such a value. As a minimum, 16 octets, or twice the specified upper -- bound, whichever is the larger, should be allowed for TeletexString. -- For UTF8String or UniversalString at least four times the upper -- bound should be allowed. END Housley, Ford, Polk, & Solo [Page 93] INTERNET DRAFT July 14, 2000 A.2 Implicitly Tagged Module, 1988 Syntax PKIX1Implicit88 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-implicit-88(2)} DEFINITIONS IMPLICIT TAGS ::= BEGIN -- EXPORTS ALL -- IMPORTS id-pkix, id-pe, id-qt, id-kp, id-qt-unotice, id-qt-cps, id-ad, id-ad-ocsp, id-ad-caIssuers, -- delete following line if "new" types are supported -- BMPString, UniversalString, UTF8String, -- end "new" types ORAddress, Name, RelativeDistinguishedName, CertificateSerialNumber, CertificateList, AlgorithmIdentifier, ub-name, Attribute, DirectoryString FROM PKIX1Explicit88 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit(1)}; -- ISO arc for standard certificate and CRL extensions id-ce OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 29} -- authority key identifier OID and syntax id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 35 } AuthorityKeyIdentifier ::= SEQUENCE { keyIdentifier [0] KeyIdentifier OPTIONAL, authorityCertIssuer [1] GeneralNames OPTIONAL, authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL } -- authorityCertIssuer and authorityCertSerialNumber shall both -- be present or both be absent KeyIdentifier ::= OCTET STRING -- subject key identifier OID and syntax id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::= { id-ce 14 } SubjectKeyIdentifier ::= KeyIdentifier Housley, Ford, Polk, & Solo [Page 94] INTERNET DRAFT July 14, 2000 -- key usage extension OID and syntax id-ce-keyUsage OBJECT IDENTIFIER ::= { id-ce 15 } KeyUsage ::= BIT STRING { digitalSignature (0), nonRepudiation (1), keyEncipherment (2), dataEncipherment (3), keyAgreement (4), keyCertSign (5), cRLSign (6), encipherOnly (7), decipherOnly (8) } -- private key usage period extension OID and syntax id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::= { id-ce 16 } PrivateKeyUsagePeriod ::= SEQUENCE { notBefore [0] GeneralizedTime OPTIONAL, notAfter [1] GeneralizedTime OPTIONAL } -- either notBefore or notAfter shall be present -- certificate policies extension OID and syntax id-ce-certificatePolicies OBJECT IDENTIFIER ::= { id-ce 32 } anyPolicy OBJECT IDENTIFIER ::= {id-ce-certificate-policies 0} CertificatePolicies ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation PolicyInformation ::= SEQUENCE { policyIdentifier CertPolicyId, policyQualifiers SEQUENCE SIZE (1..MAX) OF PolicyQualifierInfo OPTIONAL } CertPolicyId ::= OBJECT IDENTIFIER PolicyQualifierInfo ::= SEQUENCE { policyQualifierId PolicyQualifierId, qualifier ANY DEFINED BY policyQualifierId } -- Implementations that recognize additional policy qualifiers shall -- augment the following definition for PolicyQualifierId PolicyQualifierId ::= OBJECT IDENTIFIER ( id-qt-cps | id-qt-unotice ) Housley, Ford, Polk, & Solo [Page 95] INTERNET DRAFT July 14, 2000 -- CPS pointer qualifier CPSuri ::= IA5String -- user notice qualifier UserNotice ::= SEQUENCE { noticeRef NoticeReference OPTIONAL, explicitText DisplayText OPTIONAL} NoticeReference ::= SEQUENCE { organization DisplayText, noticeNumbers SEQUENCE OF INTEGER } DisplayText ::= CHOICE { ia5String IA5String (SIZE (1..200)), visibleString VisibleString (SIZE (1..200)), bmpString BMPString (SIZE (1..200)), utf8String UTF8String (SIZE (1..200)) } -- policy mapping extension OID and syntax id-ce-policyMappings OBJECT IDENTIFIER ::= { id-ce 33 } PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE { issuerDomainPolicy CertPolicyId, subjectDomainPolicy CertPolicyId } -- subject alternative name extension OID and syntax id-ce-subjectAltName OBJECT IDENTIFIER ::= { id-ce 17 } SubjectAltName ::= GeneralNames GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName GeneralName ::= CHOICE { otherName [0] AnotherName, rfc822Name [1] IA5String, dNSName [2] IA5String, x400Address [3] ORAddress, directoryName [4] Name, ediPartyName [5] EDIPartyName, uniformResourceIdentifier [6] IA5String, iPAddress [7] OCTET STRING, registeredID [8] OBJECT IDENTIFIER } -- AnotherName replaces OTHER-NAME ::= TYPE-IDENTIFIER, as Housley, Ford, Polk, & Solo [Page 96] INTERNET DRAFT July 14, 2000 -- TYPE-IDENTIFIER is not supported in the '88 ASN.1 syntax AnotherName ::= SEQUENCE { type-id OBJECT IDENTIFIER, value [0] EXPLICIT ANY DEFINED BY type-id } EDIPartyName ::= SEQUENCE { nameAssigner [0] DirectoryString OPTIONAL, partyName [1] DirectoryString } -- issuer alternative name extension OID and syntax id-ce-issuerAltName OBJECT IDENTIFIER ::= { id-ce 18 } IssuerAltName ::= GeneralNames id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::= { id-ce 9 } SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute -- basic constraints extension OID and syntax id-ce-basicConstraints OBJECT IDENTIFIER ::= { id-ce 19 } BasicConstraints ::= SEQUENCE { cA BOOLEAN DEFAULT FALSE, pathLenConstraint INTEGER (0..MAX) OPTIONAL } -- name constraints extension OID and syntax id-ce-nameConstraints OBJECT IDENTIFIER ::= { id-ce 30 } NameConstraints ::= SEQUENCE { permittedSubtrees [0] GeneralSubtrees OPTIONAL, excludedSubtrees [1] GeneralSubtrees OPTIONAL } GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree GeneralSubtree ::= SEQUENCE { base GeneralName, minimum [0] BaseDistance DEFAULT 0, maximum [1] BaseDistance OPTIONAL } BaseDistance ::= INTEGER (0..MAX) -- policy constraints extension OID and syntax id-ce-policyConstraints OBJECT IDENTIFIER ::= { id-ce 36 } Housley, Ford, Polk, & Solo [Page 97] INTERNET DRAFT July 14, 2000 PolicyConstraints ::= SEQUENCE { requireExplicitPolicy [0] SkipCerts OPTIONAL, inhibitPolicyMapping [1] SkipCerts OPTIONAL } SkipCerts ::= INTEGER (0..MAX) -- CRL distribution points extension OID and syntax id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::= {id-ce 31} CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint DistributionPoint ::= SEQUENCE { distributionPoint [0] DistributionPointName OPTIONAL, reasons [1] ReasonFlags OPTIONAL, cRLIssuer [2] GeneralNames OPTIONAL } DistributionPointName ::= CHOICE { fullName [0] GeneralNames, nameRelativeToCRLIssuer [1] RelativeDistinguishedName } ReasonFlags ::= BIT STRING { unused (0), keyCompromise (1), cACompromise (2), affiliationChanged (3), superseded (4), cessationOfOperation (5), certificateHold (6) } -- extended key usage extension OID and syntax id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37} ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId KeyPurposeId ::= OBJECT IDENTIFIER -- extended key purpose OIDs id-kp-serverAuth OBJECT IDENTIFIER ::= { id-kp 1 } id-kp-clientAuth OBJECT IDENTIFIER ::= { id-kp 2 } id-kp-codeSigning OBJECT IDENTIFIER ::= { id-kp 3 } id-kp-emailProtection OBJECT IDENTIFIER ::= { id-kp 4 } id-kp-ipsecEndSystem OBJECT IDENTIFIER ::= { id-kp 5 } id-kp-ipsecTunnel OBJECT IDENTIFIER ::= { id-kp 6 } id-kp-ipsecUser OBJECT IDENTIFIER ::= { id-kp 7 } id-kp-timeStamping OBJECT IDENTIFIER ::= { id-kp 8 } Housley, Ford, Polk, & Solo [Page 98] INTERNET DRAFT July 14, 2000 -- inhibit any policy OID and syntax id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::= { id-ce 54 } InhibitAnyPolicy ::= SkipCerts -- freshest (delta-)CRL extension OID and syntax id-ce-freshestCRL OBJECT IDENTIFIER ::= { id-ce 46 } FreshestCRL ::= CRLDistributionPoints -- authority info access id-pe-authorityInfoAccess OBJECT IDENTIFIER ::= { id-pe 1 } AuthorityInfoAccessSyntax ::= SEQUENCE SIZE (1..MAX) OF AccessDescription AccessDescription ::= SEQUENCE { accessMethod OBJECT IDENTIFIER, accessLocation GeneralName } -- CRL number extension OID and syntax id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 } CRLNumber ::= INTEGER (0..MAX) -- issuing distribution point extension OID and syntax id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 } IssuingDistributionPoint ::= SEQUENCE { distributionPoint [0] DistributionPointName OPTIONAL, onlyContainsUserCerts [1] BOOLEAN DEFAULT FALSE, onlyContainsCACerts [2] BOOLEAN DEFAULT FALSE, onlySomeReasons [3] ReasonFlags OPTIONAL, indirectCRL [4] BOOLEAN DEFAULT FALSE } id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 } -- deltaCRLIndicator ::= BaseCRLNumber BaseCRLNumber ::= CRLNumber -- CRL reasons extension OID and syntax Housley, Ford, Polk, & Solo [Page 99] INTERNET DRAFT July 14, 2000 id-ce-cRLReasons OBJECT IDENTIFIER ::= { id-ce 21 } CRLReason ::= ENUMERATED { unspecified (0), keyCompromise (1), cACompromise (2), affiliationChanged (3), superseded (4), cessationOfOperation (5), certificateHold (6), removeFromCRL (8) } -- certificate issuer CRL entry extension OID and syntax id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 } CertificateIssuer ::= GeneralNames -- hold instruction extension OID and syntax id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 } HoldInstructionCode ::= OBJECT IDENTIFIER -- ANSI x9 holdinstructions -- ANSI x9 arc holdinstruction arc holdInstruction OBJECT IDENTIFIER ::= {joint-iso-itu-t(2) member-body(2) us(840) x9cm(10040) 2} -- ANSI X9 holdinstructions referenced by this standard id-holdinstruction-none OBJECT IDENTIFIER ::= {holdInstruction 1} -- deprecated id-holdinstruction-callissuer OBJECT IDENTIFIER ::= {holdInstruction 2} id-holdinstruction-reject OBJECT IDENTIFIER ::= {holdInstruction 3} -- invalidity date CRL entry extension OID and syntax id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 } InvalidityDate ::= GeneralizedTime END Housley, Ford, Polk, & Solo [Page 100] INTERNET DRAFT July 14, 2000 Appendix B. ASN.1 Notes CAs MUST force the serialNumber to be a positive integer, that is, the sign bit in the DER encoding of the INTEGER value MUST be zero - this can be done by adding a leading (leftmost) `00'H octet if neces- sary. This removes a potential ambiguity in mapping between a string of octets and an integer value. Given the uniqueness requirements above serial numbers can be expected to contain long integers. Certificate users MUST be able to handle serialNumber values longer than 32 bits. Conformant CAs MUST NOT use serialNumber values longer than 20 octets. The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1 constructs. A valid ASN.1 sequence will have zero or more entries. The SIZE (1..MAX) construct constrains the sequence to have at least one entry. MAX indicates the upper bound is unspecified. Implementa- tions are free to choose an upper bound that suits their environment. The construct "positiveInt ::= INTEGER (0..MAX)" defines positiveInt as a subtype of INTEGER containing integers greater than or equal to zero. The upper bound is unspecified. Implementations are free to select an upper bound that suits their environment. The character string type PrintableString supports a very basic Latin character set: the lower case letters 'a' through 'z', upper case letters 'A' through 'Z', the digits '0' through '9', eleven special characters ' " ( ) + , - . / : ? and space. The character string type TeletexString is a superset of Printable- String. TeletexString supports a fairly standard (ascii-like) Latin character set, Latin characters with non-spacing accents and Japanese characters. The character string type UniversalString supports any of the charac- ters allowed by ISO 10646-1. ISO 10646 is the Universal multiple- octet coded Character Set (UCS). ISO 10646-1 specifes the architec- ture and the "basic multilingual plane" - a large standard character set which includes all major world character standards. The character string type UTF8String will be introduced in the 1998 version of ASN.1. UTF8String is a universal type and has been 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 10646." ISO is expected to formally add UTF8String to the list of choices for DirectoryString in 1998 as well. In anticipation of these changes, and in conformance with IETF Best Housley, Ford, Polk, & Solo [Page 101] INTERNET DRAFT July 14, 2000 Practices codified in RFC 2277, IETF Policy on Character Sets and Languages, this document includes UTF8String as a choice in Directo- ryString and the CPS qualifier extensions. Implementers should note that the DER encoding of the SET OF values requires ordering of the encodings of the values. In particular, this issue arises with respect to distinguished names. Object Identifiers (OIDs) are used throught this specification to identify certificate policies, public key and signature algorithms, certificate extensions, etc. There is no maximum size for OIDs. 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 268,435,455 inclusive. This allows each arc element to be represented within a single 32 bit word. Implementations MUST also support OIDs where the length of the dotted decimal (see [LDAP], section 4.1.2) string representation can be up to 100 bytes (inclusive). Implementa- tions MUST be able to handle OIDs with up to 20 elements (inclusive). CAs SHOULD NOT issue certificates which contain OIDs that breach these requirements. Appendix C. Examples This section contains four examples: three certificates and a CRL. The first two certificates and the CRL comprise a minimal certifica- tion path. Section C.1 contains an annotated hex dump of a "self-signed" certi- ficate issued by a CA whose distinguished name is cn=us,o=gov,ou=nist. The certificate contains a DSA public key with parameters, and is signed by the corresponding DSA private key. Section C.2 contains an annotated hex dump of an end-entity certifi- cate. The end entity certificate contains a DSA public key, and is signed by the private key corresponding to the "self-signed" certifi- cate in section C.1. Section C.3 contains a dump of an end entity certificate which con- tains an RSA public key and is signed with RSA and MD5. This certi- ficate is not part of the minimal certification path. 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 the list of revoked certificates includes the end entity certificate presented in C.2. The certificates were processed using Peter Gutman's dumpasn1 utility to generate the output. The source for the dumpasn1 utility is Housley, Ford, Polk, & Solo [Page 102] INTERNET DRAFT July 14, 2000 available at . The binaries for the certificates and CRLs are available at . C.1 Certificate This section contains an annotated hex dump of a 699 byte version 3 certificate. The certificate contains the following information: (a) the serial number is 23 (17 hex); (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 (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 December 31, 1997; (f) the certificate contains a 1024 bit DSA public key with parame- ters; (g) the certificate contains a subject key identifier extension; and (h) the certificate is a CA certificate (as indicated through the basic constraints extension.) 0 30 701: SEQUENCE { 4 30 637: SEQUENCE { 8 A0 3: [0] { 10 02 1: INTEGER 2 : } 13 02 1: INTEGER 23 16 30 9: SEQUENCE { 18 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3) : } 27 30 42: SEQUENCE { 29 31 11: SET { 31 30 9: SEQUENCE { 33 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 38 13 2: PrintableString 'US' : } : } 42 31 12: SET { 44 30 10: SEQUENCE { 46 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 51 13 3: PrintableString 'gov' : } : } 56 31 13: SET { 58 30 11: SEQUENCE { 60 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) 65 13 4: PrintableString 'NIST' Housley, Ford, Polk, & Solo [Page 103] INTERNET DRAFT July 14, 2000 : } : } : } 71 30 30: SEQUENCE { 73 17 13: UTCTime '970630000000Z' 88 17 13: UTCTime '971231000000Z' : } 103 30 42: SEQUENCE { 105 31 11: SET { 107 30 9: SEQUENCE { 109 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 114 13 2: PrintableString 'US' : } : } 118 31 12: SET { 120 30 10: SEQUENCE { 122 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 127 13 3: PrintableString 'gov' : } : } 132 31 13: SET { 134 30 11: SEQUENCE { 136 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) 141 13 4: PrintableString 'NIST' : } : } : } 147 30 440: SEQUENCE { 151 30 300: SEQUENCE { 155 06 7: OBJECT IDENTIFIER dsa (1 2 840 10040 4 1) 164 30 287: SEQUENCE { 168 02 129: INTEGER : 00 B6 8B 0F 94 2B 9A CE A5 25 C6 F2 ED FC FB 95 : 32 AC 01 12 33 B9 E0 1C AD 90 9B BC 48 54 9E F3 : 94 77 3C 2C 71 35 55 E6 FE 4F 22 CB D5 D8 3E 89 : 93 33 4D FC BD 4F 41 64 3E A2 98 70 EC 31 B4 50 : DE EB F1 98 28 0A C9 3E 44 B3 FD 22 97 96 83 D0 : 18 A3 E3 BD 35 5B FF EE A3 21 72 6A 7B 96 DA B9 : 3F 1E 5A 90 AF 24 D6 20 F0 0D 21 A7 D4 02 B9 1A : FC AC 21 FB 9E 94 9E 4B 42 45 9E 6A B2 48 63 FE : 43 300 02 21: INTEGER : 00 B2 0D B0 B1 01 DF 0C 66 24 FC 13 92 BA 55 F7 : 7D 57 74 81 E5 323 02 129: INTEGER : 00 9A BF 46 B1 F5 3F 44 3D C9 A5 65 FB 91 C0 8E : 47 F1 0A C3 01 47 C2 44 42 36 A9 92 81 DE 57 C5 Housley, Ford, Polk, & Solo [Page 104] INTERNET DRAFT July 14, 2000 : E0 68 86 58 00 7B 1F F9 9B 77 A1 C5 10 A5 80 91 : 78 51 51 3C F6 FC FC CC 46 C6 81 78 92 84 3D F4 : 93 3D 0C 38 7E 1A 5B 99 4E AB 14 64 F6 0C 21 22 : 4E 28 08 9C 92 B9 66 9F 40 E8 95 F6 D5 31 2A EF : 39 A2 62 C7 B2 6D 9E 58 C4 3A A8 11 81 84 6D AF : F8 B4 19 B4 C2 11 AE D0 22 3B AA 20 7F EE 1E 57 : 18 : } : } 455 03 133: BIT STRING 0 unused bits : 02 81 81 00 B5 9E 1F 49 04 47 D1 DB F5 3A DD CA : 04 75 E8 DD 75 F6 9B 8A B1 97 D6 59 69 82 D3 03 : 4D FD 3B 36 5F 4A F2 D1 4E C1 07 F5 D1 2A D3 78 : 77 63 56 EA 96 61 4D 42 0B 7A 1D FB AB 91 A4 CE : DE EF 77 C8 E5 EF 20 AE A6 28 48 AF BE 69 C3 6A : A5 30 F2 C2 B9 D9 82 2B 7D D9 C4 84 1F DE 0D E8 : 54 D7 1B 99 2E B3 D0 88 F6 D6 63 9B A7 E2 0E 82 : D4 3B 8A 68 1B 06 56 31 59 0B 49 EB 99 A5 D5 81 : 41 7B C9 55 : } 591 A3 52: [3] { 593 30 50: SEQUENCE { 595 30 31: SEQUENCE { 597 06 3: OBJECT IDENTIFIER subjectKeyIdentifier (2 5 29 14) 602 04 24: OCTET STRING : 04 16 04 14 E7 26 C5 54 CD 5B A3 6F 35 68 95 AA : D5 FF 1C 21 E4 22 75 D6 : } 628 30 15: SEQUENCE { 630 06 3: OBJECT IDENTIFIER basicConstraints (2 5 29 19) 635 01 1: BOOLEAN TRUE 638 04 5: OCTET STRING : 30 03 01 01 FF : } : } : } : } 645 30 9: SEQUENCE { 647 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3) : } 656 03 47: BIT STRING 0 unused bits : 30 2C 02 14 6A F9 3F 72 30 7F 45 DC E5 50 C1 5E : 94 A0 6D C7 92 4C E5 E1 02 14 6F 61 B8 65 F7 AA : DF 46 1B F7 39 0D 0D 88 9E FE B6 83 F7 1A : } Housley, Ford, Polk, & Solo [Page 105] INTERNET DRAFT July 14, 2000 C.2 Certificate This section contains an annotated hex dump of a 730 byte version 3 certificate. The certificate contains the following information: (a) the serial number is 18 (12 hex); (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 (d) and the subject's distinguished name is CN=Tim Polk; OU=nist; O=gov; C=US (e) the certificate was valid from July 30, 1997 through December 1, 1997; (f) the certificate contains a 1024 bit DSA public key; (g) the certificate is an end entity certificate, as the basic con- straints extension is not present; (h) the certificate contains an authority key identifier extension; and (i) the certificate includes one alternative name - an RFC 822 address. 0 30 734: SEQUENCE { 4 30 669: SEQUENCE { 8 A0 3: [0] { 10 02 1: INTEGER 2 : } 13 02 1: INTEGER 18 16 30 9: SEQUENCE { 18 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3) : } 27 30 42: SEQUENCE { 29 31 11: SET { 31 30 9: SEQUENCE { 33 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 38 13 2: PrintableString 'US' : } : } 42 31 12: SET { 44 30 10: SEQUENCE { 46 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 51 13 3: PrintableString 'gov' : } : } 56 31 13: SET { 58 30 11: SEQUENCE { 60 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) 65 13 4: PrintableString 'NIST' : } : } Housley, Ford, Polk, & Solo [Page 106] INTERNET DRAFT July 14, 2000 : } 71 30 30: SEQUENCE { 73 17 13: UTCTime '970730000000Z' 88 17 13: UTCTime '971201000000Z' : } 103 30 61: SEQUENCE { 105 31 11: SET { 107 30 9: SEQUENCE { 109 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 114 13 2: PrintableString 'US' : } : } 118 31 12: SET { 120 30 10: SEQUENCE { 122 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 127 13 3: PrintableString 'gov' : } : } 132 31 13: SET { 134 30 11: SEQUENCE { 136 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) 141 13 4: PrintableString 'NIST' : } : } 147 31 17: SET { 149 30 15: SEQUENCE { 151 06 3: OBJECT IDENTIFIER commonName (2 5 4 3) 156 13 8: PrintableString 'Tim Polk' : } : } : } 166 30 439: SEQUENCE { 170 30 300: SEQUENCE { 174 06 7: OBJECT IDENTIFIER dsa (1 2 840 10040 4 1) 183 30 287: SEQUENCE { 187 02 129: INTEGER : 00 B6 8B 0F 94 2B 9A CE A5 25 C6 F2 ED FC FB 95 : 32 AC 01 12 33 B9 E0 1C AD 90 9B BC 48 54 9E F3 : 94 77 3C 2C 71 35 55 E6 FE 4F 22 CB D5 D8 3E 89 : 93 33 4D FC BD 4F 41 64 3E A2 98 70 EC 31 B4 50 : DE EB F1 98 28 0A C9 3E 44 B3 FD 22 97 96 83 D0 : 18 A3 E3 BD 35 5B FF EE A3 21 72 6A 7B 96 DA B9 : 3F 1E 5A 90 AF 24 D6 20 F0 0D 21 A7 D4 02 B9 1A : FC AC 21 FB 9E 94 9E 4B 42 45 9E 6A B2 48 63 FE : 43 319 02 21: INTEGER : 00 B2 0D B0 B1 01 DF 0C 66 24 FC 13 92 BA 55 F7 Housley, Ford, Polk, & Solo [Page 107] INTERNET DRAFT July 14, 2000 : 7D 57 74 81 E5 342 02 129: INTEGER : 00 9A BF 46 B1 F5 3F 44 3D C9 A5 65 FB 91 C0 8E : 47 F1 0A C3 01 47 C2 44 42 36 A9 92 81 DE 57 C5 : E0 68 86 58 00 7B 1F F9 9B 77 A1 C5 10 A5 80 91 : 78 51 51 3C F6 FC FC CC 46 C6 81 78 92 84 3D F4 : 93 3D 0C 38 7E 1A 5B 99 4E AB 14 64 F6 0C 21 22 : 4E 28 08 9C 92 B9 66 9F 40 E8 95 F6 D5 31 2A EF : 39 A2 62 C7 B2 6D 9E 58 C4 3A A8 11 81 84 6D AF : F8 B4 19 B4 C2 11 AE D0 22 3B AA 20 7F EE 1E 57 : 18 : } : } 474 03 132: BIT STRING 0 unused bits : 02 81 80 30 B6 75 F7 7C 20 31 AE 38 BB 7E 0D 2B : AB A0 9C 4B DF 20 D5 24 13 3C CD 98 E5 5F 6C B7 : C1 BA 4A BA A9 95 80 53 F0 0D 72 DC 33 37 F4 01 : 0B F5 04 1F 9D 2E 1F 62 D8 84 3A 9B 25 09 5A 2D : C8 46 8E 2B D4 F5 0D 3B C7 2D C6 6C B9 98 C1 25 : 3A 44 4E 8E CA 95 61 35 7C CE 15 31 5C 23 13 1E : A2 05 D1 7A 24 1C CB D3 72 09 90 FF 9B 9D 28 C0 : A1 0A EC 46 9F 0D B8 D0 DC D0 18 A6 2B 5E F9 8F : B5 95 BE : } 609 A3 66: [3] { 611 30 64: SEQUENCE { 613 30 25: SEQUENCE { 615 06 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17) 620 04 18: OCTET STRING : 30 10 81 0E 77 70 6F 6C 6B 40 6E 69 73 74 2E 67 : 6F 76 : } 640 30 35: SEQUENCE { 642 06 3: OBJECT IDENTIFIER authorityKeyIdentifier (2 5 29 35) 647 04 28: OCTET STRING : 30 1A 80 18 04 16 04 14 E7 26 C5 54 CD 5B A3 6F : 35 68 95 AA D5 FF 1C 21 E4 22 75 D6 : } : } : } : } 677 30 9: SEQUENCE { 679 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3) : } 688 03 48: BIT STRING 0 unused bits : 30 2D 02 14 37 FC 44 BF 7F 8D 18 1F 40 04 2F CF : EA CC 22 B2 16 01 FF 13 02 15 00 97 D0 24 96 0F Housley, Ford, Polk, & Solo [Page 108] INTERNET DRAFT July 14, 2000 : 64 8A C3 8D 41 B2 0E B9 26 D5 31 D1 A0 F1 BC : } C.3 End-Entity Certificate Using RSA This section contains an annotated hex dump of a 675 byte version 3 certificate. The certificate contains the following information: (a) the serial number is 256; (b) the certificate is signed with RSA and the MD2 hash algorithm; (c) the issuer's distinguished name is OU=Dept. Arquitectura de Com- putadors; O=Universitat Politecnica de Catalunya; C=ES (d) and the subject's distinguished name is CN=Francisco Jordan; OU=Dept. Arquitectura de Computadors; O=Universitat Politecnica de Catalunya; C=ES (e) the certificate was issued on May 21, 1996 and expired on May 21, 1997; (f) the certificate contains a 768 bit RSA public key; (g) the certificate is an end entity certificate (not a CA certifi- cate); (h) the certificate includes an alternative subject name and an alternative issuer name - bothe are URLs; (i) the certificate include an authority key identifier and certifi- cate policies extensions; and (j) the certificate includes a critical key usage extension specify- ing the public is intended for generation of digital signatures. 0 30 654: SEQUENCE { 4 30 503: SEQUENCE { 8 A0 3: [0] { 10 02 1: INTEGER 2 : } 13 02 2: INTEGER 256 17 30 13: SEQUENCE { 19 06 9: OBJECT IDENTIFIER : sha1withRSAEncryption (1 2 840 113549 1 1 5) 30 05 0: NULL : } 32 30 42: SEQUENCE { 34 31 11: SET { 36 30 9: SEQUENCE { 38 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 43 13 2: PrintableString 'US' : } : } 47 31 12: SET { 49 30 10: SEQUENCE { 51 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) Housley, Ford, Polk, & Solo [Page 109] INTERNET DRAFT July 14, 2000 56 13 3: PrintableString 'gov' : } : } 61 31 13: SET { 63 30 11: SEQUENCE { 65 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 70 13 4: PrintableString 'NIST' : } : } : } 76 30 30: SEQUENCE { 78 17 13: UTCTime '960521095826Z' 93 17 13: UTCTime '970521095826Z' : } 108 30 61: SEQUENCE { 110 31 11: SET { 112 30 9: SEQUENCE { 114 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 119 13 2: PrintableString 'US' : } : } 123 31 12: SET { 125 30 10: SEQUENCE { 127 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) 132 13 3: PrintableString 'gov' : } : } 137 31 13: SET { 139 30 11: SEQUENCE { 141 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 146 13 4: PrintableString 'NIST' : } : } 152 31 17: SET { 154 30 15: SEQUENCE { 156 06 3: OBJECT IDENTIFIER commonName (2 5 4 3) 161 13 8: PrintableString 'Tim Polk' : } : } : } 171 30 159: SEQUENCE { 174 30 13: SEQUENCE { 176 06 9: OBJECT IDENTIFIER rsaEncryption (1 2 840 113549 1 1 1) 187 05 0: NULL : } 189 03 141: BIT STRING 0 unused bits Housley, Ford, Polk, & Solo [Page 110] INTERNET DRAFT July 14, 2000 : 30 81 89 02 81 81 00 E1 CE 06 C9 D7 00 DF 65 27 : 45 1E 63 6A 09 A0 A0 10 4B AF DF 9D 36 1D 44 1F : B7 07 5D 36 92 09 6A 1A 96 C7 4E D9 86 0D 0F 77 : 94 F5 82 62 68 9A F2 D7 76 F5 9A 35 C7 B3 7F 4F : BE 64 CF A3 0C B3 84 32 80 F5 CA 77 29 C9 76 0B : 4C 38 19 EE 61 6F BA 68 E0 03 85 46 34 AB 84 64 : 7F 43 69 02 C0 20 86 BD B1 D4 AD 21 A9 1A 8F CF : 96 83 86 92 57 5B 43 09 28 4C F2 5A 04 AD E5 DE : 9E 4F E8 38 3C F0 89 02 03 01 00 01 : } 333 A3 175: [3] { 336 30 172: SEQUENCE { 339 30 63: SEQUENCE { 341 06 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17) 346 04 56: OCTET STRING : 30 36 86 34 68 74 74 70 3A 2F 2F 77 77 77 2E 69 : 74 6C 2E 6E 69 73 74 2E 67 6F 76 2F 64 69 76 38 : 39 33 2F 73 74 61 66 66 2F 70 6F 6C 6B 2F 69 6E : 64 65 78 2E 68 74 6D 6C : } 404 30 31: SEQUENCE { 406 06 3: OBJECT IDENTIFIER issuerAltName (2 5 29 18) 411 04 24: OCTET STRING : 30 16 86 14 68 74 74 70 3A 2F 2F 77 77 77 2E 6E : 69 73 74 2E 67 6F 76 2F : } 437 30 31: SEQUENCE { 439 06 3: OBJECT IDENTIFIER authorityKeyIdentifier (2 5 29 35) 444 04 24: OCTET STRING : 30 16 80 14 30 12 80 10 0E 6B 3A BF 04 EA 04 C3 : 0E 6B 3A BF 04 EA 04 C3 : } 470 30 23: SEQUENCE { 472 06 3: OBJECT IDENTIFIER certificatePolicies (2 5 29 32) 477 04 16: OCTET STRING : 30 0E 30 0C 06 0A 60 86 48 01 65 03 02 01 30 09 : } 495 30 14: SEQUENCE { 497 06 3: OBJECT IDENTIFIER keyUsage (2 5 29 15) 502 01 1: BOOLEAN TRUE 505 04 4: OCTET STRING : 03 02 07 80 : } : } : } : } Housley, Ford, Polk, & Solo [Page 111] INTERNET DRAFT July 14, 2000 511 30 13: SEQUENCE { 513 06 9: OBJECT IDENTIFIER : sha1withRSAEncryption (1 2 840 113549 1 1 5) 524 05 0: NULL : } 526 03 129: BIT STRING 0 unused bits : C1 25 6F AB 72 C0 5D DA E4 2F D5 E1 B0 25 D8 B4 : F1 82 95 D6 0D A5 4E 4F A1 23 E1 13 A4 9C 3D C5 : 7F FD 05 EC 75 06 30 66 97 75 A6 5D 8F 97 BA B4 : EC A9 43 19 8D B7 54 FD E9 AD 43 B8 3C 8B D3 9E : C7 C7 27 E3 1A AD D3 79 AC 65 5A 52 78 C4 D0 43 : 81 50 F7 8A BA E2 30 1A 6D D0 78 A0 4E AE 2E 79 : 37 0C 93 05 5C D1 9C 1B B2 62 73 D1 EA 50 B7 84 : 29 92 74 34 CF BA AA 2C 4D 43 59 EF 98 0C 41 6C : } C.4 Certificate Revocation List This section contains an annotated hex dump of a version 2 CRL with one extension (cRLNumber). The CRL was issued by OU=nist;O=gov;C=us on July 7, 1996; the next scheduled issuance was August 7, 1996. The CRL includes one revoked certificates: serial number 18 (12 hex). The CRL itself is number 18, and it was signed with DSA and SHA-1. 0 30 203: SEQUENCE { 3 30 140: SEQUENCE { 6 02 1: INTEGER 1 9 30 9: SEQUENCE { 11 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3) : } 20 30 42: SEQUENCE { 22 31 11: SET { 24 30 9: SEQUENCE { 26 06 3: OBJECT IDENTIFIER countryName (2 5 4 6) 31 13 2: PrintableString 'US' : } : } 35 31 12: SET { 37 30 10: SEQUENCE { 39 06 3: OBJECT IDENTIFIER organizationName (2 5 4 10) 44 13 3: PrintableString 'gov' : } : } 49 31 13: SET { 51 30 11: SEQUENCE { 53 06 3: OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) 58 13 4: PrintableString 'NIST' Housley, Ford, Polk, & Solo [Page 112] INTERNET DRAFT July 14, 2000 : } : } : } 64 17 13: UTCTime '970807000000Z' 79 17 13: UTCTime '970907000000Z' 94 30 34: SEQUENCE { 96 30 32: SEQUENCE { 98 02 1: INTEGER 18 101 17 13: UTCTime '970731000000Z' 116 30 12: SEQUENCE { 118 30 10: SEQUENCE { 120 06 3: OBJECT IDENTIFIER cRLReason (2 5 29 21) 125 04 3: OCTET STRING : 0A 01 01 : } : } : } : } 130 A0 14: [0] { 132 30 12: SEQUENCE { 134 30 10: SEQUENCE { 136 06 3: OBJECT IDENTIFIER cRLNumber (2 5 29 20) 141 04 3: OCTET STRING : 02 01 12 : } : } : } : } 146 30 9: SEQUENCE { 148 06 7: OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3) : } 157 03 47: BIT STRING 0 unused bits : 30 2C 02 14 79 1F F6 93 0B 84 06 D6 A0 7C 8D 68 : A7 52 2E 5F 3F 89 9B 4B 02 14 66 D4 B5 2A 68 36 : 9B 72 88 58 E3 89 19 AD 81 89 2E 96 BB CC : } Housley, Ford, Polk, & Solo [Page 113] INTERNET DRAFT July 14, 2000 Appendix D. Author Addresses: Russell Housley SPYRUS 381 Elden Street Suite 1120 Herndon, VA 20170 USA housley@spyrus.com Warwick Ford VeriSign, Inc. One Alewife Center Cambridge, MA 02140 USA wford@verisign.com Tim Polk NIST Building 820, Room 426 Gaithersburg, MD 20899 USA wpolk@nist.gov David Solo Citicorp 666 Fifth Ave, 3rd Floor New York, NY 10103 USA david.solo@citicorp.com Appendix E. Full Copyright Statement Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are 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 in part without inclusion of the copyright notice. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of develop- ing Internet standards in which case the procedures for copyrights defined in the Internet Standards process shall be followed, or as Housley, Ford, Polk, & Solo [Page 114] INTERNET DRAFT July 14, 2000 required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Housley, Ford, Polk, & Solo [Page 115]