PKIX Working Group D. Pinkas (Bull) INTERNET-DRAFT T. Gindin (IBM) Expires: December 2002 June 2002 Target category: Standard Track Internet X.509 Public Key Infrastructure Permanent Identifier 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 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. 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 the certificate relates to the same entity even 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. Also, 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 Document Expiration: December 2002 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 one part of a family of standards for the X.509 Public Key Infrastructure (PKI) for the Internet. It 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 women 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 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. Pinkas, Gindin [ Page 2] Permanent Identifier Document Expiration: December 2002 When two certificates from different CA's contain both the same permanent identifier value and the same type of permanent identifier from a given Assigner Authority, then these certificates relate to the same entity, whatever the content of the DN or other subjectAltName components may be. 2. Definition of a Permanent Identifier A CA which includes a permanent identifier in a certificate is certifying that any public key certificate containing that identifier refers to the same entity, whatever the content of the DN or other subjectAltName components may be. The use of a permanent identifier is OPTIONAL. This name is defined as a form of otherName from the GeneralName structure in SubjectAltName. The permanent identifier is defined as follows: id-on-permanentIdentifier OBJECT IDENTIFIER ::= { id-on 3 } PermanentIdentifier ::= SEQUENCE { identifierValue IdentifierValue, identifierType IdentifierType OPTIONAL, matchingRule [0] IMPLICIT OBJECT IDENTIFIER OPTIONAL } IdentifierValue ::= CHOICE { iA5String IA5String, uTF8String UTF8String } IdentifierType ::= CHOICE { registeredOID OBJECT IDENTIFIER, uri IA5String } The IdentifierValue supports two syntaxes: IA5String or UTF8String. IA5String is variable length data of ASCII octets. UTF8String is variable length data of octets. UTF-8 is an ASCII-preserving encoding method for Unicode (ISO 10646), the Universal Character Set (UCS). The UCS allows to support most of the world's writing systems using a single character set. The IdentifierType field, when present, identifies both the organization responsible for assigning the content of the identifier field and the type of that field. When the IdentifierType field is missing, then it is assumed that the organization responsible for assigning the content of the identifier field is the CA itself and that there is only one type of such identifier for the CA. Pinkas, Gindin [ Page 3] Permanent Identifier Document Expiration: December 2002 The IdentifierType field may contain either: a) an Object Identifier (i.e. an OID), or b) a permanent URI using IA5String. Characteristically, when an OID is used, the prefix of the OID identifies the organization, and a suffix is used to identify the type of permanent identifier being identified. Essentially the same thing is true of URI's. 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 If identifierType is missing, then the permanent identifier is locally unique to the CA. If identifierType is present, then the permanent identifier is globally unique among all CAs. The matchingRule is an OID. When the OID is missing the following matching rule SHALL be used: The Alphanumeric Identifier Match rule compares for equality a presented value with an attribute value of type UTF8String or IA5String, which is interpreted as a series of alphanumeric characters. The rules for matching are that a working comparison value is constructed from each of the two values by including only the digits and alphabetic characters appearing in the value; and then the two comparison values are compared using CaseIgnoreMatch. This rule is intended for use only with identifiers in variants of the Latin, Greek, and Cyrillic scripts. Note: other matching rules can be used (see in chapter 6 of X.520). Two such examples are: caseIgnoreMatch {2 5 13 2} defined in section 6.1.1 of X.520, and caseExactMatch {2 5 13 5} defined in section 6.1.4 of X.520. 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. Pinkas, Gindin [ Page 4] Permanent Identifier Document Expiration: December 2002 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. 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 more present in the current certificate. The content and the format of the IdentifierValue is defined by the Assigner Authority. An Assigner Authority who wishes to permit IdentifierValues to be matched using a matching rule different from the one specified in this document would be required to specify a matching rule. Many such matching rules are specified in ITU-T X.520. 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 which contain a permanent identifier extension without a identifierType may have their permanent identifier extensions compared for equality either by comparing the public key values of the two CAs which have issued these two certificates or by comparing the sequence of CA names in the certification path from the trust anchor to the CA, inclusive. 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. 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. Pinkas, Gindin [ Page 5] Permanent Identifier Document Expiration: December 2002 [RFC 3280] R. Housley, W. Ford, W. Polk, and D. Solo, "Internet X.509 Public Key Infrastructure: Certificate and CRL Profile", April 2002. 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. [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 68, Route de Versailles 78434 Louveciennes Cedex 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. Pinkas, Gindin [ Page 6] Permanent Identifier Document Expiration: December 2002 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] Permanent Identifier Document Expiration: December 2002 APPENDIX ASN.1 definitions 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-permanent-identifier-88(14) } DEFINITIONS EXPLICIT TAGS ::= BEGIN -- EXPORTS ALL -- IMPORTS id-pkix, AttributeType, FROM PKIX1Explicit88 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit-88(1)} -- 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 } PermanentIdentifier ::= SEQUENCE { identifierValue IdentifierValue, identifierType IdentifierType OPTIONAL, matchingRule [0] IMPLICIT OBJECT IDENTIFIER OPTIONAL } IdentifierValue ::= CHOICE { iA5String IA5String, uTF8String UTF8String } IdentifierType ::= CHOICE { registeredOID OBJECT IDENTIFIER, uri IA5String } END Pinkas, Gindin [ Page 8] Permanent Identifier Document Expiration: December 2002 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-permanent-identifier-93(15) } DEFINITIONS EXPLICIT TAGS ::= BEGIN -- EXPORTS ALL -- IMPORTS id-pkix, ATTRIBUTE FROM PKIX1Explicit93 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit-93(3)}; -- 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 } -- permanent identifier permanentIdentifier ATTRIBUTE ::= { WITH SYNTAX PermanentIdentifier ID id-on-permanentIdentifier } PermanentIdentifier ::= SEQUENCE { identifierValue IdentifierValue, identifierType IdentifierType OPTIONAL, matchingRule [0] IMPLICIT OBJECT IDENTIFIER OPTIONAL } IdentifierValue ::= CHOICE { iA5String IA5String, uTF8String UTF8String } IdentifierType ::= CHOICE { registeredOID OBJECT IDENTIFIER, uri IA5String, } END Pinkas, Gindin [ Page 9] Permanent Identifier Document Expiration: December 2002 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 10] Permanent Identifier Document Expiration: December 2002 C. Full Copyright Statement Copyright (C) The Internet Society (2002). 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 developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process shall be followed, or as 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. Pinkas, Gindin [ Page 11]