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PKIX Working Group                                      D. Pinkas (Bull)
INTERNET-DRAFT                                           T. Gindin (IBM)
Expires: January 2005                                          July 2004
Target category: Standard Track



                 Internet X.509 Public Key Infrastructure
                          Permanent Identifier

                       <draft-ietf-pkix-pi-10.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of [RFC 2026].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
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   Copyright (C) The Internet Society (2002). All Rights Reserved.

   Please send comments on this document to the ietf-pkix@imc.org
   mailing list.

Abstract

   This document define 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                                                  [Page 1]

Permanent Identifier                                           July 2004

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 RFC 2119.

   This specification is based on RFC 3280, 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.

         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.

Pinkas, Gindin                                                  [Page 2]

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         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.

   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 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
}

   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 serialNumber
   attribute from the subject DN is the value to be taken for the
   identifierValue. In such a case, there MUST NOT more than one
   serialNumber attribute in the subject DN, otherwise the
   PermanentIdentifier SHALL NOT be used.



Pinkas, Gindin                                                  [Page 3]

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The assigner field is optional.

   When the assigner field is present, then it is an OID which
   identifies both the Assigner Authority and the type of that field.
   In such a case, the identifierValue field MUST be present.
   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.

Only the following three combinations are allowed :

1- Both the assigner and the identifierValue fields are present:

   The assigner field identifies the Assigner Authority and the type
   of permanent identifier being identified. The identifierValue is
   the value for that type of identifier. The permanent identifier is
   globally unique among all CAs. In such a case, two permanent
   identifiers of this type match if and only if the contents of the
   identifierValue field in the two permanent identifiers consist of
   the same Unicode code points presented in the same order and the
   assigner field match.

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:

    The value of the single serialNumber attribute included in the
    subject DN SHALL be considered as the identifier value assigned
    within the naming space of the certificate issuer. 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.

The following combination is NOT allowed:
    The assigner field is present and the identifierValue field is
    absent.



Pinkas, Gindin                                                  [Page 4]

Permanent Identifier                                           July 2004

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. 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. identifierType is not
   present), then two certificates from the same CA can be compared.


   When they contain two 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.
   identifierType 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.

   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. These names 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 a identifierType 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.

Pinkas, Gindin                                                  [Page 5]

Permanent Identifier                                           July 2004

   When the above checks fail, the permanents 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 RFC 2630
   section 5.3 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.

4. References

4.1. Normative

   [RFC 2026] S. Bradner, "The Internet Standards Process - Revision 3"
   November 1996.

   [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
   Requirement Levels", March 1997.

   [RFC 3280] R. Housley, W. Ford, W. Polk, and D. Solo, "Internet X.509
   Public Key Infrastructure: Certificate and CRL Profile", April 2002.

   [Unicode] The Unicode Consortium, "The Unicode Standard, Version
   3.2.0" is defined by "The Unicode Standard, Version 3.0"
   (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5), as amended
   by the "Unicode Standard Annex #27: Unicode 3.1"
   (http://www.unicode.org/reports/tr27/) and by the "Unicode Standard
   Annex #28: Unicode 3.2" (http://www.unicode.org/reports/tr28/).

   [ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
   Architecture and Basic Multilingual Plane, ISO/IEC 10646-1: 1993.

   [UTF-8] RFC 2279. F. Yergeau. UTF-8, a transformation format of
   ISO 10646, January 1998.

4.2. Informative

   [X.501]  ITU-T Recommendation X.501 (1997 E): Information Technology
   - Open Systems Interconnection - The Directory: Models, June 1997.

   [X.509]  ITU-T Recommendation X.509 (1997 E): Information Technology
   - Open Systems Interconnection - The Directory: Authentication
   Framework, June 1997.




Pinkas, Gindin                                                  [Page 6]

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   [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.

5. Author's Addresses

   Denis Pinkas
   Bull
   Rue Jean-Jaurˆs. 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

6. Intellectual Property Rights

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to

   pertain 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.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.






Pinkas, Gindin                                                  [Page 7]

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APPENDIX A

ASN.1 definitions

   As in RFC 3280, 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 by an 1993 ASN.1-parser by removing the
   UTF8String choice from the definition of IdentifierValue in the
   module. Appendix A.2 may be parsed "as is" by an 1997 ASN.1 parser.

   In case of discrepancies between these modules, the 1988 module is
   the normative one.



























Pinkas, Gindin                                                  [Page 8]

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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

   -- EXPORTS ALL --

   IMPORTS

-- UTF8String, / move hyphens before slash if UTF8String does not
-- resolve with your compiler
-- The content of this type conforms to RFC 2279.

        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 [RFC 3280]


   -- Object Identifiers

-- Externally defined OIDs

   -- Arc for other name forms
   id-on   OBJECT IDENTIFIER ::= { id-pkix 8 }

   -- permanent identifier

   id-on-permanentIdentifier   OBJECT IDENTIFIER ::= { id-on 3 }
   id-mod-perm-id-88           OBJECT IDENTIFIER ::= { id-mod 28 }


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






Pinkas, Gindin                                                  [Page 9]

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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

   -- 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 [RFC 3280]

   -- Object Identifiers

-- Externally defined OIDs

   -- Arc for other name forms
   id-on   OBJECT IDENTIFIER ::= { id-pkix 8 }

-- Locally defined OIDs
id-on-permanentIdentifier     OBJECT IDENTIFIER ::= { id-on 3 }
id-mod-perm-id-93             OBJECT IDENTIFIER ::= { id-mod 29 }

   -- 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






Pinkas, Gindin                                                 [Page 10]

Permanent Identifier                                           July 2004


APPENDIX B. OID's for organizations

In order to obtain an OID for an identifier type, organizations need
first to have a registered OID for themselves (or must use a permanent
URI). 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.

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:
ftp://ftp.isi.edu/in-notes/iana/assignments/enterprise-numbers

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)}



Pinkas, Gindin                                                 [Page 11]

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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:

   - the ICD value: The International Code Designator issued to the
     identification scheme makes the identifier worldwide unique
     (up to 4 digits),

   - the Organization, usually a company or governmental body
     (up to 35 characters),

   - 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).

Example:

The ICD 0012 was allocated to European Computer Manufacturers
Association : ECMA. Thus the OID is 1(iso). 3(identified organization).
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



Pinkas, Gindin                                                 [Page 12]

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Full Copyright Statement

   Copyright (C) The Internet Society (2004). All Rights Reserved.

   This document and translations of it may be copied and furnished to
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   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
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   The limited permissions granted above are perpetual and will not be
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Pinkas, Gindin                                                 [Page 13]


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