< draft-ietf-stir-certificates-ocsp-00.txt   draft-ietf-stir-certificates-ocsp-01.txt >
Network Working Group J. Peterson Network Working Group J. Peterson
Internet-Draft Neustar Internet-Draft Neustar
Intended status: Standards Track S. Turner Intended status: Standards Track S. Turner
Expires: September 14, 2017 sn3rd Expires: 23 October 2022 sn3rd
March 13, 2017 21 April 2022
OCSP Usage for Secure Telephone Identity Certificates OCSP Usage for Secure Telephone Identity Certificates
draft-ietf-stir-certificates-ocsp-00.txt draft-ietf-stir-certificates-ocsp-01
Abstract Abstract
When certificates are used as credentials to attest the assignment or When certificates are used as credentials to attest the assignment or
ownership of telephone numbers, some mechanism is required to convey ownership of telephone numbers, some mechanism is required to convey
certificate freshness to relying parties. This document specifies certificate freshness to relying parties. Certififcate Revocation
the use of the Online Certificate Status Protocol (OCSP) as a means Lists (CRLs) are commonly used for this purpose, but for certain
of retrieving real-time status information about such certificates, classes of certificates, including delegate certificates conveying
defining new extensions to compensate for the dynamism of telephone their scope of authority by-reference in Secure Telephone Identity
number assignments. Revisited (STIR) systems, they may not be aligned with the needs of
relying parties. This document specifies the use of the Online
Certificate Status Protocol (OCSP) as a means of retrieving real-time
status information about such certificates, defining new extensions
to compensate for the dynamism of telephone number assignments.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 14, 2017. This Internet-Draft will expire on 23 October 2022.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Certificate Verification Methods . . . . . . . . . . . . . . 3 3. Certificate Verification Methods . . . . . . . . . . . . . . 3
3.1. Using OCSP with TN Auth List . . . . . . . . . . . . . . 4 3.1. Using OCSP with TN Auth List . . . . . . . . . . . . . . 4
3.1.1. OCSP Extension Specification . . . . . . . . . . . . 5 3.1.1. OCSP Extension Specification . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 7 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 10 Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The STIR problem statement [RFC7340] discusses many attacks on the The STIR problem statement [RFC7340] discusses many attacks on the
telephone network that are enabled by impersonation, including telephone network that are enabled by impersonation, including
various forms of robocalling, voicemail hacking, and swatting. One various forms of robocalling, voicemail hacking, and swatting. One
of the most important components of a system to prevent impersonation of the most important components of a system to prevent impersonation
is the implementation of credentials which identify the parties who is the implementation of credentials which identify the parties who
control telephone numbers. The STIR certificates control telephone numbers. The STIR certificates [RFC8226]
[I-D.ietf-stir-certificates] specification describes a credential specification describes a credential system based on [X.509] version
system based on [X.509] version 3 certificates in accordance with 3 certificates in accordance with [RFC5280] for that purpose. Those
[RFC5280] for that purpose. Those credentials can then be used by credentials can then be used by STIR authentication services
STIR authentication services [I-D.ietf-stir-rfc4474bis] to sign [RFC8224] to sign PASSporT objects [RFC8225] carried in a SIP
PASSporT objects [I-D.ietf-stir-passport] carried in a SIP [RFC3261] [RFC3261] request. No specific recommendation is made in the STIR
request. certificates document for a means of determining the freshness of
certificates with a TN Authorization List. This document explores
approaches to real-time status information for such certificates, and
recommends an approach.
The STIR certificates document specifies an extension to X.509 that The STIR certificates document specifies an extension to X.509 that
defines a Telephony Number (TN) Authorization List that may be defines a Telephony Number (TN) Authorization List that may be
included by certificate authorities in certificates. This extension included by certificate authorities in certificates. This extension
provides additional information that relying parties can use when provides additional information that relying parties can use when
validating transactions with the certificate. When a SIP request, validating transactions with the certificate. When a SIP request,
for example, arrives at a terminating administrative domain, the for example, arrives at a terminating administrative domain, the
calling number attested by the SIP request can be compared to the TN calling number attested by the SIP request can be compared to the TN
Authorization List of the certificate that signed the request to Authorization List of the certificate that signed the request to
determine if the caller is authorized to use that calling number in determine if the caller is authorized to use that calling number in
SIP. SIP.
However, there is significant dynamism in telephone number However, there is significant dynamism in telephone number
assignment, and due to practices like number portability, information assignment, and due to practices like number portability, information
about number assignment can suddenly become stale. This problem is about number assignment can suddenly become stale. This problem is
especially pronounced when a TN Authorization List extension especially pronounced when a TN Authorization List extension
associates a large block of telephone numbers with a certificate, as associates a large block of telephone numbers with a certificate, as
relying parties need a way to learn if any one of those telephone relying parties need a way to learn if any one of those telephone
numbers has been ported to a different administrative entity. numbers has been ported to a different administrative entity. To
facilitate this, [RFC8226] Section 10.1 specifies a way that the TN
No specific recommendation is made in the STIR certificates document Authorization List can be shared by-reference in a certificate, via a
for a means of determining the freshness of certificates with a TN URL in the Authority Information Access extension, so that a more
Authorization List. This document explores approaches to real-time dynamic list can be maintained without continually reissuing the
status information for such certificates, and recommends an approach. certificate. For very large and/or complex TN Authorization Lists,
however, this could require relying parties to redownload the entire
list virtually every time they process a call. Moreover, some
certificate holders may be reluctant to share the entire list of
telephone numbers associated with a certificate in cases where a
relying party only needs to know, effectively, whether a single
number (the calling party number for a particular call) is in the
scope of authority for a certificate or not.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC "OPTIONAL" in this document are to be interpreted as described in BCP
2119 [RFC2119]. 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Certificate Verification Methods 3. Certificate Verification Methods
For traditional certificate status information, there are three For traditional certificate status information, there are three
common certificate verification mechanisms employed by CAs: common certificate verification mechanisms employed by CAs:
1. Certificate Revocation Lists (CRLs) [RFC5280] (and [RFC6818]) 1. Certificate Revocation Lists (CRLs) [RFC5280] (and [RFC6818])
2. Online Certificate Status Protocol (OCSP) [RFC6960], and 2. Online Certificate Status Protocol (OCSP) [RFC6960], and
skipping to change at page 3, line 47 skipping to change at page 4, line 16
status information - but before that can happen, the verifier needs status information - but before that can happen, the verifier needs
to know where to locate it. Placing the location of the status to know where to locate it. Placing the location of the status
information in the certificate makes the certificate larger, but it information in the certificate makes the certificate larger, but it
eases the client workload. The CRL Distribution Point certificate eases the client workload. The CRL Distribution Point certificate
extension includes the location of the CRL and the Authority extension includes the location of the CRL and the Authority
Information Access certificate extension includes the location of Information Access certificate extension includes the location of
OCSP and/or SCVP servers; both of these extensions are defined in OCSP and/or SCVP servers; both of these extensions are defined in
[RFC5280]. In all cases, the status information location is provided [RFC5280]. In all cases, the status information location is provided
in the form of an URI. in the form of an URI.
CRLs are an attractive solution because they are supported by every CRLs are an attractive solution because they are supported the
CA. CRLs have a reputation of being quite large (10s of MBytes), tradition web PKI environments. CRLs hhave a reputation of being
because CAs maintain and issue one monolithic CRL with all of their quite large (10s of MBytes), because CAs maintain and issue one
revoked certificates, but CRLs do support a variety of mechanisms to monolithic CRL with all of their revoked certificates, but CRLs do
scope the size of the CRLs based on revocation reasons (e.g., key support a variety of mechanisms to scope the size of the CRLs based
compromise vs CA compromise), user certificates only, and CA on revocation reasons (e.g., key compromise vs CA compromise), user
certificates only as well as just operationally deciding to keep the certificates only, and CA certificates only as well as just
CRLs small. However, scoping the CRL introduces other issues (i.e., operationally deciding to keep the CRLs small. However, scoping the
does the RP have all of the CRL partitions). CRL introduces other issues (i.e., does the relying party have all of
the CRL partitions). In practice, CRLs are widely used in STIR
environments, often through a federated approach where a community of
trusted CAs pool their CRLs for distribution from a central point.
CAs in the STIR architecture will likely all create CRLs for audit CAs in the STIR architecture thus have already implemented CRLs,
purposes, but probably not for real-time status information. Any largely for audit purposes rather than real-time status information.
such CRLs used MUST be signed with the same algorithm as the The need for these CRLs is not likely to go away, especially for the
certificate. We thus anticipate that one of the two "online" options case of service providers whose certificates are based on Service
is preferred. Between the two, OCSP is much more widely deployed and Provider Codes (SPCs). For delegate STIR certificates ([RFC9060]),
this document therefore RECOMMENDS the use of OCSP in high-volume however, especially those with TN Authorization Lists based on
environments (HVE) for validating the freshness of certificates, telephone numbers, OCSP may provide an important optimizations.
based on [RFC6960], incorporating some (but not all) of the Between the OCSP and SCVP, OCSP is much more widely deployed and this
optimizations of [RFC5019]. document therefore RECOMMENDS the use of OCSP in high-volume
environments (HVE) for validating the freshness of telephone-number
based certificates, based on [RFC6960], incorporating some (but not
all) of the optimizations of [RFC5019].
3.1. Using OCSP with TN Auth List 3.1. Using OCSP with TN Auth List
Certificates compliant with this specification SHOULD include a URL Certificates compliant with this specification SHOULD include a URL
[RFC3986] pointing to an OCSP service in the Authority Information [RFC3986] pointing to an OCSP service in the Authority Information
Access (AIA) certificate extension, via the "id-ad-ocsp" accessMethod Access (AIA) certificate extension, via the "id-ad-ocsp" accessMethod
specified in [RFC5280]. It is RECOMMENDED that entities that issue specified in [RFC5280]. This can appear in addition to, or as an
certificates with the Telephone Number Authorization List certificate alternative to, the "id-ad-stirTNList" accessMethod specified in
extension run an OCSP server for this purpose. Baseline OCSP however [RFC8226]. It is RECOMMENDED that entities that issue certificates
supports only three possible response values: good, revoked, or with the Telephone Number Authorization List certificate extension
unknown. Without some extension, OCSP would not indicate whether the run an OCSP server for this purpose. Baseline OCSP however supports
only three possible response values: good, revoked, or unknown.
Without some extension, OCSP would not indicate whether the
certificate is authorized for a particular telephone number that the certificate is authorized for a particular telephone number that the
verifier is validating. verifier is validating.
At a high level, there are two ways that a client might pose this At a high level, there are two ways that a client might pose this
authorization question: authorization question:
For this certificate, is the following number currently in its For this certificate, is the following number currently in its
scope of validity? scope of validity?
What are all the telephone numbers associated with this What are all the telephone numbers associated with this
certificate, or this certificate subject? certificate, or this certificate subject?
Only the former lends itself to piggybacking on the OCSP status Only the former lends itself to piggybacking on the OCSP status
mechanism; since the verifier is already asking an authority about mechanism; since the verifier is already asking an authority about
the certificate's status, that mechanism can be reused instead of the certificate's status, that mechanism can be reused instead of
creating a new service that requires additional round trips? Like creating a new service that requires additional round trips? Like
most PKIX-developed protocols, OCSP is extensible; OCSP supports most PKIX-developed protocols, OCSP is extensible; OCSP supports
request extensions (including sending multiple requests at once) and request extensions (including sending multiple requests at once) and
per-request extensions. It seems unlikely that the verifier will be per-request extensions. As the relying party in STIR is validating a
requesting authorization checks on multiple telephone numbers in one PASSporT associated with a telephone call, it is unlikely that the
request, so a per-request extension is what is needed. verifier will request authorization checks on multiple telephone
numbers in one request, so a per-request extension is what is needed.
The requirement to consult OCSP in real time results in a network Consulting OCSP in real time results in a network round-trip delay,
round-trip delay, which is something to consider because it will add which is something to consider because it will add to the call setup
to the call setup time. OCSP server implementations commonly pre- time. OCSP server implementations commonly pre-generate responses,
generate responses, and to speed up HTTPS connections, servers often and to speed up HTTPS connections, servers often provide OCSP
provide OCSP responses for each certificate in their hierarchy. If responses for each certificate in their hierarchy. If possible, both
possible, both of these OCSP concepts should be adopted for use with of these OCSP concepts should be adopted for use with STIR. Future
STIR. work may also explore ways that OCSP stapling [RFC6961] could be
accommodated by STIR.
3.1.1. OCSP Extension Specification 3.1.1. OCSP Extension Specification
The extension mechanism for OCSP follows X.509 v3 certificate The extension mechanism for OCSP follows X.509 v3 certificate
extensions, and thus requires an OID, a criticality flag, and ASN.1 extensions, and thus requires an OID, a criticality flag, and ASN.1
syntax as defined by the OID. The criticality specified here is syntax as defined by the OID. The criticality specified here is
optional: per [RFC6960] Section 4.4, support for all OCSP extensions optional: per [RFC6960] Section 4.4, support for all OCSP extensions
is optional. If the OCSP server does not understand the requested is optional. If the OCSP server does not understand the requested
extension, it will still provide the baseline validation of the extension, it will still provide the baseline validation of the
certificate itself. Moreover, in practical STIR deployments, the certificate itself. Moreover, in practical STIR deployments, the
issuer of the certificate will set the accessLocation for the OCSP issuer of the certificate will set the accessLocation for the OCSP
AIA extension to point to an OCSP service that supports this AIA extension to point to an OCSP service that supports this
extension, so the risk of interoperability failure due to lack of extension, so the risk of interoperability failure due to lack of
support for this extension is minimal. support for this extension is minimal.
The OCSP TNQuery extension is included as one of the request's The OCSP TNQuery extension is included as one of the request's
singleRequestExtensions. It may also appear in the response's singleRequestExtensions; it carries the telephone number for which
singleExtensions. When an OCSP server includes a number in the the query is being performed, typically the telephone number in the
response's singleExtensions, this informs the client that the "orig" field of a PASSporT being validated. The TNQuery extension
certificate is still valid for the number that appears in the TNQuery may also appear in the response's singleExtensions; when an OCSP
extension field. If the TNQuery is absent from a response to a query server includes a telephone number in the response's
singleExtensions, this informs the client that the certificate is
still valid for the number that appears in the TNQuery extension
field. If the TNQuery is absent from a response to a query
containing a TNQuery in its singleRequestExtension, then the server containing a TNQuery in its singleRequestExtension, then the server
is not able to validate that the number is still in the scope of is not able to validate that the number is still in the scope of
authority of the certificate. authority of the certificate.
id-pkix-ocsp-stir-tn OBJECT IDENTIFIER ::= { id-pkix-ocsp 10 } id-pkix-ocsp-stir-tn OBJECT IDENTIFIER ::= { id-pkix-ocsp 10 }
TNQuery ::= E164Number TNQuery ::= E164Number
The HVE OCSP profile [RFC5019] prohibits the use of per-request The HVE OCSP profile [RFC5019] prohibits the use of per-request
extensions. As it is anticipated that STIR will use OCSP in a high- extensions. As it is anticipated that STIR will use OCSP in a high-
volume environment, many of the optimizations recommended by HVE are volume environment, many of the optimizations recommended by HVE are
desirable for the STIR environment. This document therefore uses the desirable for the STIR environment. This document therefore uses the
HVE optimizations augmented as follows: HVE optimizations augmented as follows:
o Implementations MUST use SHA-256 as the hashing algorithm for the * Implementations MUST use SHA-256 as the hashing algorithm for the
CertID.issuerNameHash and the CertID.issuerKeyHash values. That CertID.issuerNameHash and the CertID.issuerKeyHash values. That
is CertID.hashAlgorithm is id-sha256 [RFC4055] and the values are is CertID.hashAlgorithm is id-sha256 [RFC4055] and the values are
truncated to 160-bits as specified Option 1 in Section 2 of truncated to 160-bits as specified Option 1 in Section 2 of
[RFC7093]. [RFC7093].
o Clients MUST include the OCSP TNQuery extension in requests' * Clients MUST include the OCSP TNQuery extension in requests'
singleRequestExtensions. singleRequestExtensions.
o Servers MUST include the OCSP TNQuery extension in responses' * Servers MUST include the OCSP TNQuery extension in responses'
singleExtensions. singleExtensions.
o Servers SHOULD return responses that would otherwise have been * Servers SHOULD return responses that would otherwise have been
"unknown" as "not good" (i.e., return only "good" and "not good" "unknown" as "not good" (i.e., return only "good" and "not good"
responses). responses).
o Clients MUST treat returned "unknown" responses as "not good". * Clients MUST treat returned "unknown" responses as "not good".
o If the server uses ResponderID, it MUST generate the KeyHash using * If the server uses ResponderID, it MUST generate the KeyHash using
SHA-256 and truncate the value to 160-bits as specified in Option SHA-256 and truncate the value to 160-bits as specified in Option
1 in Section 2 of [RFC7093]. 1 in Section 2 of [RFC7093].
o Implementations MUST support ECDSA using P-256 and SHA-256. Note * Implementations MUST support ECDSA using P-256 and SHA-256. Note
that [RFC6960] requires RSA with SHA-256 be supported. that [RFC6960] requires RSA with SHA-256 be supported.
o This removes the requirement to support SHA-1, RSA with SHA-1, or * This removes the requirement to support SHA-1, RSA with SHA-1, or
DSA with SHA-1. DSA with SHA-1.
OCSP responses MUST be signed using the same algorithm as the OCSP responses MUST be signed using the same algorithm as the
certificate being checked. certificate being checked.
To facilitate matching the authority key identifier values found in To facilitate matching the authority key identifier values found in
CA certificates with the KeyHash used in the OCSP response, CA certificates with the KeyHash used in the OCSP response,
certificates compliant with this specification MUST generate certificates compliant with this specification MUST generate
authority key identifiers and subject key identifiers using the authority key identifiers and subject key identifiers using the
SHA-256 and truncate the value to 160-bits as specified in Option 1 SHA-256 and truncate the value to 160-bits as specified in Option 1
skipping to change at page 8, line 4 skipping to change at page 8, line 33
Security Considerations. For OCSP-related security considerations Security Considerations. For OCSP-related security considerations
see [RFC6960] and [RFC5019]. see [RFC6960] and [RFC5019].
7. Acknowledgments 7. Acknowledgments
Stephen Farrell provided key input to the discussions leading to this Stephen Farrell provided key input to the discussions leading to this
document. Russ Housley provided some direct assistance and text document. Russ Housley provided some direct assistance and text
surrounding the ASN.1 module. surrounding the ASN.1 module.
8. References 8. References
8.1. Normative References
[I-D.ietf-stir-certificates]
Peterson, J. and S. Turner, "Secure Telephone Identity
Credentials: Certificates", draft-ietf-stir-
certificates-11 (work in progress), October 2016.
[I-D.ietf-stir-passport]
Wendt, C. and J. Peterson, "Personal Assertion Token
(PASSporT)", draft-ietf-stir-passport-11 (work in
progress), February 2017.
[I-D.ietf-stir-rfc4474bis] 8.1. Normative References
Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
"Authenticated Identity Management in the Session
Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-16
(work in progress), February 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055, and Certificate Revocation List (CRL) Profile", RFC 4055,
DOI 10.17487/RFC4055, June 2005, DOI 10.17487/RFC4055, June 2005,
<http://www.rfc-editor.org/info/rfc4055>. <https://www.rfc-editor.org/info/rfc4055>.
[RFC5019] Deacon, A. and R. Hurst, "The Lightweight Online [RFC5019] Deacon, A. and R. Hurst, "The Lightweight Online
Certificate Status Protocol (OCSP) Profile for High-Volume Certificate Status Protocol (OCSP) Profile for High-Volume
Environments", RFC 5019, DOI 10.17487/RFC5019, September Environments", RFC 5019, DOI 10.17487/RFC5019, September
2007, <http://www.rfc-editor.org/info/rfc5019>. 2007, <https://www.rfc-editor.org/info/rfc5019>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the [RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)", RFC 5912, Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
DOI 10.17487/RFC5912, June 2010, DOI 10.17487/RFC5912, June 2010,
<http://www.rfc-editor.org/info/rfc5912>. <https://www.rfc-editor.org/info/rfc5912>.
[RFC6818] Yee, P., "Updates to the Internet X.509 Public Key [RFC6818] Yee, P., "Updates to the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 6818, DOI 10.17487/RFC6818, January (CRL) Profile", RFC 6818, DOI 10.17487/RFC6818, January
2013, <http://www.rfc-editor.org/info/rfc6818>. 2013, <https://www.rfc-editor.org/info/rfc6818>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., [RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP", Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013, RFC 6960, DOI 10.17487/RFC6960, June 2013,
<http://www.rfc-editor.org/info/rfc6960>. <https://www.rfc-editor.org/info/rfc6960>.
[RFC7093] Turner, S., Kent, S., and J. Manger, "Additional Methods [RFC7093] Turner, S., Kent, S., and J. Manger, "Additional Methods
for Generating Key Identifiers Values", RFC 7093, for Generating Key Identifiers Values", RFC 7093,
DOI 10.17487/RFC7093, December 2013, DOI 10.17487/RFC7093, December 2013,
<http://www.rfc-editor.org/info/rfc7093>. <https://www.rfc-editor.org/info/rfc7093>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8224] Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
"Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 8224,
DOI 10.17487/RFC8224, February 2018,
<https://www.rfc-editor.org/info/rfc8224>.
[RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<https://www.rfc-editor.org/info/rfc8225>.
[RFC8226] Peterson, J. and S. Turner, "Secure Telephone Identity
Credentials: Certificates", RFC 8226,
DOI 10.17487/RFC8226, February 2018,
<https://www.rfc-editor.org/info/rfc8226>.
[RFC9060] Peterson, J., "Secure Telephone Identity Revisited (STIR)
Certificate Delegation", RFC 9060, DOI 10.17487/RFC9060,
September 2021, <https://www.rfc-editor.org/info/rfc9060>.
[X.509] ITU-T Recommendation X.509 (10/2012) | ISO/IEC 9594-8, [X.509] ITU-T Recommendation X.509 (10/2012) | ISO/IEC 9594-8,
"Information technology - Open Systems Interconnection - "Information technology - Open Systems Interconnection -
The Directory: Public-key and attribute certificate The Directory: Public-key and attribute certificate
frameworks", 2012. frameworks", 2012.
[X.680] ITU-T Recommendation X.680 (08/2015) | ISO/IEC 8824-1, [X.680] ITU-T Recommendation X.680 (08/2015) | ISO/IEC 8824-1,
"Information Technology - Abstract Syntax Notation One: "Information Technology - Abstract Syntax Notation One:
Specification of basic notation". Specification of basic notation".
skipping to change at page 10, line 10 skipping to change at page 10, line 44
[X.683] ITU-T Recommendation X.683 (08/2015) | ISO/IEC 8824-3, [X.683] ITU-T Recommendation X.683 (08/2015) | ISO/IEC 8824-3,
"Information Technology - Abstract Syntax Notation One: "Information Technology - Abstract Syntax Notation One:
Parameterization of ASN.1 Specifications". Parameterization of ASN.1 Specifications".
8.2. Informative References 8.2. Informative References
[RFC5055] Freeman, T., Housley, R., Malpani, A., Cooper, D., and W. [RFC5055] Freeman, T., Housley, R., Malpani, A., Cooper, D., and W.
Polk, "Server-Based Certificate Validation Protocol Polk, "Server-Based Certificate Validation Protocol
(SCVP)", RFC 5055, DOI 10.17487/RFC5055, December 2007, (SCVP)", RFC 5055, DOI 10.17487/RFC5055, December 2007,
<http://www.rfc-editor.org/info/rfc5055>. <https://www.rfc-editor.org/info/rfc5055>.
[RFC6961] Pettersen, Y., "The Transport Layer Security (TLS) [RFC6961] Pettersen, Y., "The Transport Layer Security (TLS)
Multiple Certificate Status Request Extension", RFC 6961, Multiple Certificate Status Request Extension", RFC 6961,
DOI 10.17487/RFC6961, June 2013, DOI 10.17487/RFC6961, June 2013,
<http://www.rfc-editor.org/info/rfc6961>. <https://www.rfc-editor.org/info/rfc6961>.
[RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure [RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
Telephone Identity Problem Statement and Requirements", Telephone Identity Problem Statement and Requirements",
RFC 7340, DOI 10.17487/RFC7340, September 2014, RFC 7340, DOI 10.17487/RFC7340, September 2014,
<http://www.rfc-editor.org/info/rfc7340>. <https://www.rfc-editor.org/info/rfc7340>.
Appendix A. ASN.1 Module Appendix A. ASN.1 Module
This appendix provides the normative ASN.1 [X.680] definitions for This appendix provides the normative ASN.1 [X.680] definitions for
the structures described in this specification using ASN.1, as the structures described in this specification using ASN.1, as
defined in [X.680] through [X.683]. defined in [X.680] through [X.683].
The modules defined in this document are compatible with the most The modules defined in this document are compatible with the most
current ASN.1 specification published in 2015 (see [X.680], [X.681], current ASN.1 specification published in 2015 (see [X.680], [X.681],
[X.682], [X.683]). None of the newly defined tokens in the 2008 [X.682], [X.683]). None of the newly defined tokens in the 2008
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