]> X.509 Certificate Extended Key Usage (EKU) for Instant Messaging URIs Rohan Mahy Consulting Services
rohan.ietf@gmail.com
SEC lamps x.509 certificate extended key usage eku instant messaging im URI mimi URL RFC 5280 specifies several extended key purpose identifiers (KeyPurposeIds) for X.509 certificates. This document defines an Instant Messaging (IM) identity KeyPurposeId for inclusion in the Extended Key Usage (EKU) extension of X.509 v3 public key certificates
Introduction Instant Messaging (IM) systems using the Messaging Layer Security (MLS) protocol can incorporate per-client identity certificate credentials. A subjectAltName in these certificates can be an IM URI or Extensible Messaging and Presence Protocol (XMPP) URI , for example. Organizations may be unwilling to issue certificates for an IM client using a general KeyPurposeId, such as id-kp-serverAuth or id-kp-clientAuth, because of the risk that such certificates could be abused in a cross-protocol attack. An explanation of MLS credentials as they apply to IM is described in . These credentials are expected to be heavily used in the More Instant Messaging Interoperability (MIMI) Working Group.
Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.
The IM URI EKU This specification defines the KeyPurposeId id-kp-imUri, which may be included in certificates used to prove the identity of an IM client. This EKU extension MAY, at the option of the certificate issuer, be either critical or non-critical.
Security Considerations The security considerations of are applicable to this document. The id-kp-imUri extended key purpose does not introduce new security risks but instead reduces existing security risks by providing means to identify if the certificate is generated to sign IM identity credentials. Issuers SHOULD NOT set the id-kp-imUri extended key purpose and an id-kp-clientAuth or id-kp-serverAuth extended key purpose: that would defeat the improved specificity offered by having an id-kp-imUri extended key purpose.
IANA Considerations IANA has registered the following OID in the "SMI Security for PKIX Extended Key Purpose" registry (1.3.6.1.5.5.7.3). This OID is defined in .
Decimal Description References
40 id-kp-imUri RFC 9734
IANA has also registered the following ASN.1 module OID in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0). This OID is defined in .
Decimal Description References
113 id-mod-im-eku RFC 9734
References Normative References Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER) ITU-T Information Technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation ITU-T Informative References
ASN.1 Module The following module adheres to ASN.1 specifications and . IM-EKU { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-im-eku (113) } DEFINITIONS IMPLICIT TAGS ::= BEGIN -- OID Arc id-kp OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) kp(3) } -- Extended Key Usage Values id-kp-imUri OBJECT IDENTIFIER ::= { id-kp 40 } END ]]>
Acknowledgments Thanks to and for reviews, suggestions, corrections, and encouragement.