JOSE Working Group M. Jones Internet-Draft Microsoft Intended status: Standards Track May 12, 2012 Expires: November 13, 2012 JSON Web Key (JWK) draft-ietf-jose-json-web-key-02 Abstract A JSON Web Key (JWK) is a JSON data structure that represents a public key. This specification also defines a JSON Web Key Set (JWK Set) JSON data structure for representing a set of JWKs. Cryptographic algorithms and identifiers used with this specification are enumerated in the separate JSON Web Algorithms (JWA) specification. Requirements Language 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 [RFC2119]. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on November 13, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents Jones Expires November 13, 2012 [Page 1] Internet-Draft JWK May 2012 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Example JSON Web Key Set . . . . . . . . . . . . . . . . . . . 3 4. JSON Web Key (JWK) Format . . . . . . . . . . . . . . . . . . . 4 4.1. "alg" (Algorithm Family) Parameter . . . . . . . . . . . . 4 4.2. "use" (Key Use) Parameter . . . . . . . . . . . . . . . . . 5 4.3. "kid" (Key ID) Parameter . . . . . . . . . . . . . . . . . 5 5. JSON Web Key Set (JWK Set) Format . . . . . . . . . . . . . . . 5 5.1. "keys" (JSON Web Key Set) Parameter . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6.1. JSON Web Key Set Parameters Registry . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 8. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 7 Appendix B. Document History . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Jones Expires November 13, 2012 [Page 2] Internet-Draft JWK May 2012 1. Introduction A JSON Web Key (JWK) is a JSON data structure that represents a public key as a JSON object [RFC4627]. This specification also defines a JSON Web Key Set (JWK Set) JSON data structure for representing a set of JWKs. Cryptographic algorithms and identifiers used with this specification are enumerated in the separate JSON Web Algorithms (JWA) [JWA] specification. Non-goals for this specification include representing private keys, representing symmetric keys, representing certificate chains, representing certified keys, and replacing X.509 certificates. JWKs are used in the JSON Web Signature (JWS) [JWS] "jwk" (JSON Web Key) header parameter and the JSON Web Encryption (JWE) [JWE] "jwk" (JSON Web Key) and "epk" (Ephemeral Public Key) header parameters. The resources referenced by the JWS "jku" (JWK Set URL) and JWE "jku" (JWK Set URL) header parameters contain JWK Sets. 2. Terminology JSON Web Key (JWK) A JSON data structure that represents a public key. JSON Web Key Set (JWK Set) A JSON object that contains an array of JWKs as a member. Base64url Encoding For the purposes of this specification, this term always refers to the URL- and filename-safe Base64 encoding described in RFC 4648 [RFC4648], Section 5, with the (non URL- safe) '=' padding characters omitted, as permitted by Section 3.2. (See Appendix B of [JWS] for notes on implementing base64url encoding without padding.) 3. Example JSON Web Key Set The following example JWK Set contains two public keys represented as JWKs: one using an Elliptic Curve algorithm and a second one using an RSA algorithm. The first specifies that the key is to be used for encryption. Both provide a Key ID for key matching purposes. In both cases, integers are represented using the base64url encoding of their big endian representations. (Long lines are broken are for display purposes only.) Jones Expires November 13, 2012 [Page 3] Internet-Draft JWK May 2012 {"keys": [ {"alg":"EC", "crv":"P-256", "x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4", "y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM", "use":"enc", "kid":"1"}, {"alg":"RSA", "mod": "0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx 4cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMs tn64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2 QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbI SD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqb w0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw", "exp":"AQAB", "kid":"2011-04-29"} ] } 4. JSON Web Key (JWK) Format A JSON Web Key (JWK) is a JSON object containing specific members, as specified below. Those members that are common to all key types are defined below. JWKs also require members that are specific to the particular key algorithm family to represent the key parameters. These algorithm specific members are defined in Section 5 of the JSON Web Algorithms (JWA) [JWA] specification. The member names within a JWK MUST be unique; objects with duplicate member names MUST be rejected. Additional members MAY be present in the JWK. If present, they MUST be understood by implementations using them. Parameters for representing keys for additional algorithm families or additional key properties SHOULD either be defined in the IANA JSON Web Key Parameters registry [JWA] or be a URI that contains a collision resistant namespace. 4.1. "alg" (Algorithm Family) Parameter The "alg" (algorithm family) member identifies the cryptographic algorithm family used with the key. A list of defined "alg" values is presented in Section 5.1 of the JSON Web Algorithms (JWA) [JWA] Jones Expires November 13, 2012 [Page 4] Internet-Draft JWK May 2012 specification. Specific additional members are required to represent the key, depending upon the algorithm family. These members are specified in Section 5 of the JSON Web Algorithms (JWA) [JWA] specification. The "alg" value is case sensitive. Its value MUST be a string. "alg" values SHOULD either be defined in the IANA JSON Web Key Algorithm Families registry [JWA] or be a URI that contains a collision resistant namespace. 4.2. "use" (Key Use) Parameter The "use" (key use) member identifies the intended use of the key. Values defined by this specification are "sig" (signature) and "enc" (encryption). Other values MAY be used. The "use" value is case sensitive. Its value MUST be a string. This member is OPTIONAL. 4.3. "kid" (Key ID) Parameter The "kid" (key ID) member can be used to match a specific key. This can be used, for instance, to choose among a set of keys within the JWK during key rollover. When used with JWS or JWE, the "kid" value MAY be used to match a JWS or JWE "kid" header parameter value. The interpretation of the "kid" value is unspecified. Its value MUST be a string. This member is OPTIONAL. 5. JSON Web Key Set (JWK Set) Format A JSON Web Key Set (JWK Set) is a JSON object that contains an array of JSON Web Key values as the value of its "keys" member. The member names within a JWK Set MUST be unique; objects with duplicate member names MUST be rejected. Additional members MAY be present in the JWK Set. If present, they MUST be understood by implementations using them. Parameters for representing additional properties of JWK Sets SHOULD either be defined in the IANA JSON Web Key Set Parameters registry Section 6.1 or be a URI that contains a collision resistant namespace. 5.1. "keys" (JSON Web Key Set) Parameter The value of the "keys" (JSON Web Key Set) member is an array of JSON Web Key (JWK) values. This member is REQUIRED. Jones Expires November 13, 2012 [Page 5] Internet-Draft JWK May 2012 6. IANA Considerations 6.1. JSON Web Key Set Parameters Registry This specification establishes the IANA JSON Web Key Set Parameters registry for reserved JWK Set parameter names. Inclusion in the registry is RFC Required in the RFC 5226 [RFC5226] sense. The registry records the reserved parameter name and a reference to the RFC that defines it. This specification registers the parameter names defined in Section 5. 7. Security Considerations A key is no more trustworthy than the method by which it was received. The security considerations in XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124], about public key representations also apply to this specification, other than those that are XML specific. 8. Open Issues and Things To Be Done (TBD) The following items remain to be done in this draft: o (None at present) 9. References 9.1. Normative References [JWA] Jones, M., "JSON Web Algorithms (JWA)", May 2012. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4627] Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, July 2006. [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, October 2006. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Jones Expires November 13, 2012 [Page 6] Internet-Draft JWK May 2012 9.2. Informative References [JWE] Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web Encryption (JWE)", May 2012. [JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", May 2012. [MagicSignatures] Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic Signatures", January 2011. [W3C.CR-xmldsig-core2-20120124] Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P., Hirsch, F., Cantor, S., and T. Roessler, "XML Signature Syntax and Processing Version 2.0", World Wide Web Consortium CR CR-xmldsig-core2-20120124, January 2012, . Appendix A. Acknowledgements A JSON representation for RSA public keys was previously introduced in Magic Signatures [MagicSignatures]. Appendix B. Document History -02 o Simplified JWK terminology to get replace the "JWK Key Object" and "JWK Container Object" terms with simply "JSON Web Key (JWK)" and "JSON Web Key Set (JWK Set)" and to eliminate potential confusion between single keys and sets of keys. As part of this change, the top-level member name for a set of keys was changed from "jwk" to "keys". o Clarified that values with duplicate member names MUST be rejected. o Established JSON Web Key Set Parameters registry. o Explicitly listed non-goals in the introduction. o Moved algorithm-specific definitions from JWK to JWA. o Reformatted to give each member definition its own section heading. Jones Expires November 13, 2012 [Page 7] Internet-Draft JWK May 2012 -01 o Corrected the Magic Signatures reference. -00 o Created the initial IETF draft based upon draft-jones-json-web-key-03 with no normative changes. Author's Address Michael B. Jones Microsoft Email: mbj@microsoft.com URI: http://self-issued.info/ Jones Expires November 13, 2012 [Page 8]