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rfc:rfc4043

Network Working Group D. Pinkas Request for Comments: 4043 Bull Category: Standards Track T. Gindin

                                                                   IBM
                                                              May 2005
              Internet X.509 Public Key Infrastructure
                        Permanent Identifier

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).

Abstract

 This document defines a new form of name, called permanent
 identifier, that may be included in the subjectAltName extension of a
 public key certificate issued to an entity.
 The permanent identifier is an optional feature that may be used by a
 CA to indicate that two or more certificates relate to the same
 entity, even if they contain different subject name (DNs) or
 different names in the subjectAltName extension, or if the name or
 the affiliation of that entity stored in the subject or another name
 form in the subjectAltName extension has changed.
 The subject name, carried in the subject field, is only unique for
 each subject entity certified by the one CA as defined by the issuer
 name field.  However, the new name form can carry a name that is
 unique for each subject entity certified by a CA.

Pinkas & Gindin Standards Track [Page 1] RFC 4043 Permanent Identifier May 2005

Table of Contents

 1.  Introduction..................................................  2
 2.  Definition of a Permanent Identifier..........................  3
 3.  IANA Considerations...........................................  6
 4.  Security Considerations.......................................  6
 5.  References....................................................  7
     5.1.  Normative References....................................  7
     5.2.  Informative References..................................  8
 Appendix A. ASN.1 Syntax..........................................  9
     A.1.  1988 ASN.1 Module.......................................  9
     A.2.  1993 ASN.1 Module....................................... 10
 Appendix B. OID's for organizations............................... 11
     B.1.  Using IANA (Internet Assigned Numbers Authority)........ 11
     B.2.  Using an ISO Member Body................................ 12
     B.3.  Using an ICD (International Code Designator) From
           British Standards Institution to Specify a New or
           an Existing Identification Scheme....................... 12
 Authors' Addresses................................................ 14
 Full Copyright Statement.......................................... 15

1. Introduction

 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 [RFC2119].
 This specification is based on [RFC3280], which defines underlying
 certificate formats and semantics needed for a full implementation of
 this standard.
 The subject field of a public key certificate identifies the entity
 associated with the public key stored in the subject public key
 field.  Names and identities of a subject may be carried in the
 subject field and/or the subjectAltName extension.  Where subject
 field is non-empty, it MUST contain an X.500 distinguished name (DN).
 The DN MUST be unique for each subject entity certified by a single
 CA as defined by the issuer name field.
 The subject name changes whenever any of the components of that name
 gets changed.  There are several reasons for such a change to happen.
    For employees of a company or organization, the person may get a
    different position within the same company and thus will move from
    one organization unit to another one.  Including the organization
    unit in the name may however be very useful to allow the relying
    parties (RP's) using that certificate to identify the right
    individual.

Pinkas & Gindin Standards Track [Page 2] RFC 4043 Permanent Identifier May 2005

    For citizens, an individual may change their name by legal
    processes, especially as a result of marriage.
    Any certificate subject identified by geographical location may
    relocate and change at least some of the location attributes
    (e.g., country name, state or province, locality, or street).
 A permanent identifier consists of an identifier value assigned
 within a given naming space by the organization which is
 authoritative for that naming space.  The organization assigning the
 identifier value may be the CA that has issued the certificate or a
 different organization called an Assigner Authority.
 An Assigner Authority may be a government, a government agency, a
 corporation, or any other sort of organization.  It MUST have a
 unique identifier to distinguish it from any other such authority.
 In this standard, that identifier MUST be an object identifier.
 A permanent identifier may be useful in three contexts: access
 control, non-repudiation and audit records.
    For access control, the permanent identifier may be used in an ACL
    (Access Control List) instead of the DN or any other form of name
    and would not need to be changed, even if the subject name of the
    entity changes.  For non-repudiation, the permanent identifier may
    be used to link different transactions to the same entity, even
    when the subject name of the entity changes.
    For audit records, the permanent identifier may be used to link
    different audit records to the same entity, even when the subject
    name of the entity changes.
 For two certificates which have been both verified to be valid
 according to a given validation policy and which contain a permanent
 identifier, those certificates relate to the same entity if their
 permanent identifiers match, whatever the content of the DN or other
 subjectAltName components may be.
 Since the use of permanent identifiers may conflict with privacy, CAs
 SHOULD advertise to purchasers of certificates the use of permanent
 identifiers in certificates.

2. Definition of a Permanent Identifier

 This Permanent Identifier is a name defined as a form of otherName
 from the GeneralName structure in SubjectAltName, as defined in
 [X.509] and [RFC3280].

Pinkas & Gindin Standards Track [Page 3] RFC 4043 Permanent Identifier May 2005

 A CA which includes a permanent identifier in a certificate is
 certifying that any public key certificate containing the same values
 for that identifier refers to the same entity.
 The use of a permanent identifier is OPTIONAL.  The permanent
 identifier is defined as follows:
    id-on-permanentIdentifier   OBJECT IDENTIFIER ::= { id-on 3 }
      PermanentIdentifier ::=     SEQUENCE {
         identifierValue    UTF8String             OPTIONAL,
                         -- if absent, use a serialNumber attribute,
                         -- if there is such an attribute present
                         -- in the subject DN
         assigner           OBJECT IDENTIFIER      OPTIONAL
                         -- if absent, the assigner is
                         -- the certificate issuer
 }
 The identifierValue field is optional.
    When the identifierValue field is present, then the
    identifierValue supports one syntax: UTF8String.
    When the identifierValue field is absent, then the value of the
    serialNumber attribute (as defined in section 5.2.9 of [X.520])
    from the deepest RDN of the subject DN is the value to be taken
    for the identifierValue.  In such a case, there MUST be at least
    one serialNumber attribute in the subject DN, otherwise the
    PermanentIdentifier SHALL NOT be used.
 The assigner field is optional.
    When the assigner field is present, then it is an OID which
    identifies a naming space, i.e., both an Assigner Authority and
    the type of that field.  Characteristically, the prefix of the OID
    identifies the Assigner Authority, and a suffix is used to
    identify the type of permanent identifier.
    When the assigner field is absent, then the permanent identifier
    is locally unique to the CA.
 The various combinations are detailed below:
 1. Both the assigner and the identifierValue fields are present:
    The identifierValue is the value for that type of identifier.  The
    assigner field identifies the Assigner Authority and the type of
    permanent identifier being identified.

Pinkas & Gindin Standards Track [Page 4] RFC 4043 Permanent Identifier May 2005

    The permanent identifier is globally unique among all CAs.  In
    such a case, two permanent identifiers of this type match if and
    only if their assigner fields match and the contents of the
    identifierValue field in the two permanent identifiers consist of
    the same Unicode code points presented in the same order.
 2. The assigner field is absent and the identifierValue field is
    present:
    The Assigner Authority is the CA that has issued the certificate.
    The identifierValue is given by the CA and the permanent
    identifier is only local to the CA that has issued the
    certificate.
    In such a case, two permanent identifiers of this type match if
    and only if the issuer DN's in the certificates which contain them
    match using the distinguishedNameMatch rule, as defined in X.501,
    and the two values of the identifierValue field consist of the
    same Unicode code points presented in the same order.
 3. Both the assigner and the identifierValue fields are absent:
    If there are one or more RDNs containing a serialNumber attribute
    (alone or accompanied by other attributes), then the value
    contained in the serialNumber of the deepest such RDN SHALL be
    used as the identifierValue; otherwise, the Permanent Identifier
    definition is invalid and the Permanent Identifier SHALL NOT be
    used.
    The permanent identifier is only local to the CA that has issued
    the certificate.  In such a case, two permanent identifiers of
    this type match if and only if the issuer DN's in the certificates
    which contain them match and the serialNumber attributes within
    the subject DN's of those same certificates also match using the
    caseIgnoreMatch rule.
 4. The assigner field is present and the identifierValue field is
    absent:
    If there are one or more RDNs containing a serialNumber attribute
    (alone or accompanied by other attributes), then the value
    contained in the serialNumber of the deepest such RDN SHALL be
    used as the identifierValue; otherwise, the Permanent Identifier
    definition is invalid and the Permanent Identifier SHALL NOT be
    used.
    The assigner field identifies the Assigner Authority and the type
    of permanent identifier being identified.

Pinkas & Gindin Standards Track [Page 5] RFC 4043 Permanent Identifier May 2005

    The permanent identifier is globally unique among all CAs.  In
    such a case, two permanent identifiers of this type match if and
    only if their assigner fields match and the contents of the
    serialNumber attributes within the subject DN's of those same
    certificates match using the caseIgnoreMatch rule.
 Note: The full arc of the object identifier used to identify the
       permanent identifier name form is derived using:
    id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
       dod(6) internet(1) security(5) mechanisms(5) pkix(7) }
    id-on OBJECT IDENTIFIER ::= { id-pkix 8 }   -- other name forms

3. IANA Considerations

 No IANA actions are necessary.  However, a Private Enterprise Number
 may be used to construct an OID for the assigner field (see Annex
 B.1.).

4. Security Considerations

 A given entity may have at an instant of time or at different
 instants of time multiple forms of identities.  If the permanent
 identifier is locally unique to the CA (i.e., the assigner field is
 not present), then two certificates from the same CA can be compared.
 When two certificates contain identical permanent identifiers, then a
 relying party may determine that they refer to the same entity.
 If the permanent identifier is globally unique among all CAs (i.e.,
 the assigner field is present), then two certificates from different
 CAs can be compared.  When they contain two identical permanent
 identifiers, then a relying party may determine that they refer to
 the same entity.  It is the responsibility of the CA to verify that
 the permanent identifier being included in the certificate refers to
 the subject being certified.
 The permanent identifier identifies the entity, irrespective of any
 attribute extension.  When a public key certificate contains
 attribute extensions, the permanent identifier, if present, should
 not be used for access control purposes but only for audit purposes.
 The reason is that since these attributes may change, access could be
 granted on attributes that were originally present in a certificate
 issued to that entity but are no longer present in the current
 certificate.

Pinkas & Gindin Standards Track [Page 6] RFC 4043 Permanent Identifier May 2005

 Subject names in certificates are chosen by the issuing CA and are
 mandated to be unique for each CA; so there can be no name collision
 between subject names from the same CA.  Such a name may be an end-
 entity name when the certificate is a leaf certificate, or a CA name,
 when it is a CA certificate.
 Since a name is only unique towards its superior CA, unless some
 naming constraints are being used, a name would only be guaranteed to
 be globally unique when considered to include a sequence of all the
 names of the superior CAs.  Thus, two certificates that are issued
 under the same issuer DN and which contain the same permanent
 identifier extension without an assigner field do not necessarily
 refer to the same entity.
 Additional checks need to be done, e.g., to check if the public key
 values of the two CAs which have issued the certificates to be
 compared are identical or if the sequence of CA names in the
 certification path from the trust anchor to the CA are identical.
 When the above checks fail, the permanent identifiers may still match
 if there has been a CA key rollover.  In such a case the checking is
 more complicated.
 The certification of different CAs with the same DN by different CAs
 has other negative consequences in various parts of the PKI, notably
 rendering the IssuerAndSerialNumber structure in [RFC3852] section
 10.2.4 ambiguous.
 The permanent identifier allows organizations to create links between
 different certificates associated with an entity issued with or
 without overlapping validity periods.  This ability to link different
 certificates may conflict with privacy.  It is therefore important
 that a CA clearly disclose any plans to issue certificates which
 include a permanent identifier to potential subjects of those
 certificates.

5. References

5.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3280]  Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
            X.509 Public Key Infrastructure Certificate and
            Certificate Revocation List (CRL) Profile", RFC 3280,
            April 2002.

Pinkas & Gindin Standards Track [Page 7] RFC 4043 Permanent Identifier May 2005

 [UTF-8]    Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, November 2003.
 [X.501]    ITU-T Rec X.501 | ISO 9594-2: 2001: Information technology
            - Open Systems Interconnection - The Directory: Models,
            February 2001.

5.2. Informative References

 [RFC3852]  Housley, R., "Cryptographic Message Syntax (CMS)", RFC
            3852, July 2004.
 [X.509]    ITU-T Recommendation X.509 (1997 E): Information
            Technology - Open Systems Interconnection - The Directory:
            Authentication Framework, June 1997.
 [X.520]    ITU-T Recommendation X.520: Information Technology - Open
            Systems Interconnection - The Directory: Selected
            Attribute Types, June 1997.
 [X.660]    ITU-T Recommendation X.660: Information Technology - Open
            Systems Interconnection - Procedures for the Operation of
            OSI Registration Authorities: General Procedures, 1992.
 [X.680]    ITU-T Recommendation X.680: Information Technology -
            Abstract Syntax Notation One, 1997.

Pinkas & Gindin Standards Track [Page 8] RFC 4043 Permanent Identifier May 2005

Appendix A. ASN.1 Syntax

 As in RFC 2459, ASN.1 modules are supplied in two different variants
 of the ASN.1 syntax.
 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
 the UNIVERSAL Type 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.
 Appendix A.1 may be parsed by an 1988 ASN.1-parser by replacing the
 definitions for the UNIVERSAL Types with the 1988 catch-all "ANY".
 Appendix A.2 may be parsed "as is" by an 1997-compliant ASN.1 parser.
 In case of discrepancies between these modules, the 1988 module is
 the normative one.

Appendix A.1. 1988 ASN.1 Module

PKIXpermanentidentifier88 {iso(1) identified-organization(3) dod(6)
       internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
       id-mod-perm-id-88(28) }
DEFINITIONS EXPLICIT TAGS ::=
   BEGIN
  1. - EXPORTS ALL –
   IMPORTS
  1. - UTF8String, / move hyphens before slash if UTF8String does not
  2. - resolve with your compiler
  3. - The content of this type conforms to [UTF-8].
        id-pkix
              FROM PKIX1Explicit88 { iso(1) identified-organization(3)
              dod(6) internet(1) security(5) mechanisms(5) pkix(7)
              id-mod(0) id-pkix1-explicit(18) } ;
              -- from [RFC3280]

Pinkas & Gindin Standards Track [Page 9] RFC 4043 Permanent Identifier May 2005

  1. - Permanent identifier Object Identifier and Syntax
   id-on   OBJECT IDENTIFIER ::= { id-pkix 8 }
   id-on-permanentIdentifier   OBJECT IDENTIFIER ::= { id-on 3 }
   PermanentIdentifier ::= SEQUENCE {
        identifierValue    UTF8String             OPTIONAL,
                        -- if absent, use the serialNumber attribute
                        -- if there is a single such attribute present
                        -- in the subject DN
        assigner           OBJECT IDENTIFIER      OPTIONAL
                        -- if absent, the assigner is
                        -- the certificate issuer
}
END

Appendix A.2. 1993 ASN.1 Module

PKIXpermanentidentifier93 {iso(1) identified-organization(3) dod(6)

     internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
     id-mod-perm-id-93(29) }
 DEFINITIONS EXPLICIT TAGS ::=
 BEGIN
  1. - EXPORTS ALL –
 IMPORTS
      id-pkix
            FROM PKIX1Explicit88 { iso(1) identified-organization(3)
            dod(6) internet(1) security(5) mechanisms(5) pkix(7)
            id-mod(0) id-pkix1-explicit(18) }
             -- from [RFC3280]
      ATTRIBUTE
            FROM InformationFramework {joint-iso-itu-t ds(5) module(1)
            informationFramework(1) 4};
             -- from [X.501]
  1. - Permanent identifier Object Identifiers
 id-on   OBJECT IDENTIFIER ::= { id-pkix 8 }
 id-on-permanentIdentifier   OBJECT IDENTIFIER ::= { id-on 3 }

Pinkas & Gindin Standards Track [Page 10] RFC 4043 Permanent Identifier May 2005

  1. - Permanent Identifier
 permanentIdentifier ATTRIBUTE ::= {
        WITH SYNTAX     PermanentIdentifier
        ID              id-on-permanentIdentifier }
 PermanentIdentifier ::= SEQUENCE {
      identifierValue    UTF8String             OPTIONAL,
                      -- if absent, use the serialNumber attribute
                      -- if there is a single such attribute present
                      -- in the subject DN
      assigner           OBJECT IDENTIFIER      OPTIONAL
                      -- if absent, the assigner is
                      -- the certificate issuer

}

END

Appendix B. OID's for Organizations

 In order to construct an OID for the assigner field, organizations
 need first to have a registered OID for themselves.  Such an OID must
 be obtained from a registration authority following [X.660].  In some
 cases, OID's are provided for free.  In other cases a one-time fee is
 required.  The main difference lies in the nature of the information
 that is collected at the time of registration and how this
 information is verified for its accuracy.

Appendix B.1. Using IANA (Internet Assigned Numbers Authority)

 The application form for a Private Enterprise Number in the IANA's
 OID list is: http://www.iana.org/cgi-bin/enterprise.pl.
 Currently, IANA assigns numbers for free.  The IANA-registered
 Private Enterprises prefix is:
 iso.org.dod.internet.private.enterprise (1.3.6.1.4.1)
 These numbers are used, among other things, for defining private SNMP
 MIBs.
 The official assignments under this OID are stored in the IANA file
 "enterprise-numbers" available at:
 http://www.iana.org/assignments/enterprise-numbers

Pinkas & Gindin Standards Track [Page 11] RFC 4043 Permanent Identifier May 2005

Appendix B.2. Using an ISO Member Body

 ISO has defined the OID structure in a such a way so that every ISO
 member-body has its own unique OID.  Then every ISO member-body is
 free to allocate its own arc space below.
 Organizations and enterprises may contact the ISO member-body where
 their organization or enterprise is established to obtain an
 organization/enterprise OID.
 Currently, ISO members do not assign organization/enterprise OID's
 for free.
 Most of them do not publish registries of such OID's which they have
 assigned, sometimes restricting the access to registered
 organizations or preferring to charge inquirers for the assignee of
 an OID on a per-inquiry basis.  The use of OID's from an ISO member
 organization which does not publish such a registry may impose extra
 costs on the CA that needs to make sure that the OID corresponds to
 the registered organization.
 As an example, AFNOR (Association Francaise de Normalisation - the
 French organization that is a member of ISO) has defined an arc to
 allocate OID's for companies:
 {iso (1) member-body (2) fr (250) type-org (1) organisation (n)}

Appendix B.3. Using an ICD (International Code Designator) From British

             Standards Institution to Specify a New or an Existing
             Identification Scheme
 The International Code Designator (ICD) is used to uniquely identify
 an ISO 6523 compliant organization identification scheme.  ISO 6523
 is a standard that defines the proper structure of an identifier and
 the registration procedure for an ICD.  The conjunction of the ICD
 with an identifier issued by the registration authority is worldwide
 unique.
 The basic structure of the code contains the following components:
  1. the ICD value: The International Code Designator issued to the

identification scheme makes the identifier worldwide unique (up to

    4 digits),
  1. the Organization, usually a company or governmental body (up to 35

characters),

Pinkas & Gindin Standards Track [Page 12] RFC 4043 Permanent Identifier May 2005

  1. an Organization Part (OPI - Organization Part Identifier). An

identifier allocated to a particular Organization Part (optional,

    up to 35 characters)
 The ICD is also equivalent to an object identifier (OID) under the
 arc {1(iso).  3(identified organization)}.
 On behalf of ISO, British Standards Institution (BSI) is the
 Registration Authority for organizations under the arc {iso (1)
 org(3)}.  This means BSI registers code issuing authorities
 (organizations) by ICD values which are equivalent to OIDs of the
 form {iso (1) org(3) icd(xxxx)}.  The corresponding IdentifierValue
 is the code value of the scheme identified by icd(xxxx).
 As an example, the ICD 0012 was allocated to European Computer
 Manufacturers Association: ECMA.  Thus the OID for ECMA is {iso(1)
 org(3) ecma(12)}.
 For registration with BSI, a "Sponsoring Authority" has to vouch for
 the Applying organization.  Registration is not free.  Recognized
 "Sponsoring Authorities" are: ISO Technical Committees or
 (Sub)Committees, Member Bodies of ISO or International Organizations
 having a liaison status with ISO or with any of its Technical
 (Sub)Committees.
 An example of a Sponsoring Authority is the EDIRA Association (EDI/EC
 Registration Authority, web: http://www.edira.org,
 email:info@edira.org).
 The numerical list of all ICDs that have been issued is posted on its
 webpage: http://www.edira.org/documents.htm#icd-List
 Note: IANA owns ICD code 0090, but (presumably) it isn't intending to
 use it for the present purpose.

Pinkas & Gindin Standards Track [Page 13] RFC 4043 Permanent Identifier May 2005

Authors' Addresses

 Denis Pinkas
 Bull
 Rue Jean-Jaures BP 68
 78340 Les Clayes-sous-Bois
 FRANCE
 EMail: Denis.Pinkas@bull.net
 Thomas Gindin
 IBM Corporation
 6710 Rockledge Drive
 Bethesda, MD 20817
 USA
 EMail: tgindin@us.ibm.com

Pinkas & Gindin Standards Track [Page 14] RFC 4043 Permanent Identifier May 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM 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.

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 The IETF invites any interested party to bring to its attention any
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Pinkas & Gindin Standards Track [Page 15]

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