Network Working Group M. Jones Internet-Draft Microsoft Intended status: Standards Track April 29, 2011 Expires: October 31, 2011 JSON Web Key (JWK) draft-jones-json-web-key-00 Abstract A JSON Web Key (JWK) is a JSON data structure that represents a set of public keys. 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 October 31, 2011. Copyright Notice Copyright (c) 2011 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 (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 Jones Expires October 31, 2011 [Page 1] Internet-Draft JSON Web Key (JWK) April 2011 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. JSON Web Key (JWK) Overview . . . . . . . . . . . . . . . . . . 3 3.1. Example JWK . . . . . . . . . . . . . . . . . . . . . . . . 3 4. JWK Format . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. JWK Container Object Format . . . . . . . . . . . . . . . . 4 4.2. JWK Key Object Format . . . . . . . . . . . . . . . . . . . 4 4.2.1. JWK Key Object Members for ECDSA Keys . . . . . . . . . 5 4.2.2. JWK Key Object Members for RSA Keys . . . . . . . . . . 6 5. Base64url encoding as used by JWKs . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 7 Appendix B. Document History . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Jones Expires October 31, 2011 [Page 2] Internet-Draft JSON Web Key (JWK) April 2011 1. Introduction A JSON Web Key (JWK) is a JSON data structure that represents a set of public keys as a JSON object [RFC4627]. The JWK format is used to represent bare keys; representing certificate chains is an explicit non-goal of this specification. JSON Web Keys are referenced in JSON Web Signatures (JWSs) [JWS] using the "jku" (JSON Key URL) header parameter. 2. Terminology JSON Web Key (JWK) A JSON data structure that represents a set of public keys. A JWK consists of a single JWK Container Object that contains an array of JWK Key Objects. JWK Container Object A JSON object that contains an array of JWK Key Objects as a member. JWK Key Object A JSON object that represents a single public key. Base64url Encoding For the purposes of this specification, this term always refers to the he URL- and filename-safe Base64 encoding described in RFC 4648 [RFC4648], Section 5, with the '=' padding characters omitted, as permitted by Section 3.2. 3. JSON Web Key (JWK) Overview It is sometimes useful to be able to reference public key representations, for instance, in order to verify the signature on content signed with the corresponding private key. The JSON Web Key (JWK) data structure provides a convenient JSON representation for sets of public keys utilizing either the ECDSA or RSA families of algorithms. 3.1. Example JWK The following example JWK contains two public keys: one using the ECDSA algorithm and a second one using the RSA algorithm. In both cases, integers are represented using the base64url encoding of their big endian representations. Jones Expires October 31, 2011 [Page 3] Internet-Draft JSON Web Key (JWK) April 2011 {"keyvalues": [ {"algorithm":"ECDSA", "curve":"P-256", "x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4", "y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM", "keyid":"1"}, {"algorithm":"RSA", "modulus": "0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw", "exponent":"AQAB", "keyid":"2011-04-29"} ] } 4. JWK Format A JWK consists of a JWK Container Object, which is a JSON object that contains an array of JWK Key Objects as a member. This section specifies the format of these objects. 4.1. JWK Container Object Format A JWK Container Object is a JSON object containing a specific member. This member is: +-----------+----------+--------------------------------------------+ | Member | JSON | Container Object Member Semantics | | Name | Value | | | | Type | | +-----------+----------+--------------------------------------------+ | keyvalues | array | The "keyvalues" member value contains an | | | | array of JWT Key Objects. This member is | | | | REQUIRED. | +-----------+----------+--------------------------------------------+ JWK Container Object Member Additional members MAY be present in the JWK Container Object. If present, they MUST be understood by implementations using that JWK. 4.2. JWK Key Object Format A JWK Key Object is a JSON object containing specific members. Those members that are common to all key types are as follows: Jones Expires October 31, 2011 [Page 4] Internet-Draft JSON Web Key (JWK) April 2011 +-----------+--------+----------------------------------------------+ | Member | JSON | Key Object Member Semantics | | Name | Value | | | | Type | | +-----------+--------+----------------------------------------------+ | algorithm | string | The "algorithm" member identifies the | | | | cryptographic algorithm used with the key. | | | | Values defined by this specification are | | | | "ECDSA" and "RSA". Specific additional | | | | members are required to represent the key, | | | | depending upon the "algorithm" value. The | | | | "algorithm" value is case sensitive. This | | | | member is REQUIRED. | | keyid | string | The "keyid" (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. The | | | | "keyid" value MAY correspond to a JWS "kid" | | | | value. The interpretation of the "keyid" | | | | value is unspecified. This member is | | | | OPTIONAL. | +-----------+--------+----------------------------------------------+ JWK Key Object Members Additional members MAY be present in the JWK Key Object. If present, they MUST be understood by implementations using that key. 4.2.1. JWK Key Object Members for ECDSA Keys JWKs can represent Elliptic Curve Digital Signature Algorithm (ECDSA) [FIPS.186-3] keys. In this case, the "algorithm" member value MUST be "ECDSA". Furthermore, these additional members MUST be present: +--------+--------+-------------------------------------------------+ | Member | JSON | Key Object Member Semantics | | Name | Value | | | | Type | | +--------+--------+-------------------------------------------------+ | curve | string | The "curve" member identifies the cryptographic | | | | curve used with the key. Values defined by | | | | this specification are "P-256", "P-384" and | | | | "P-521". Additional "curve" values MAY be | | | | used, provided they are understood by | | | | implementations using that ECDSA key. The | | | | "curve" value is case sensitive. | Jones Expires October 31, 2011 [Page 5] Internet-Draft JSON Web Key (JWK) April 2011 | x | string | The "x" member contains the x coordinate for | | | | the elliptic curve point. It is represented as | | | | the base64url encoding of the coordinate's big | | | | endian representation. | | y | string | The "y" member contains the y coordinate for | | | | the elliptic curve point. It is represented as | | | | the base64url encoding of the coordinate's big | | | | endian representation. | +--------+--------+-------------------------------------------------+ Members for ECDSA Keys 4.2.2. JWK Key Object Members for RSA Keys JWKs can represent RSA [RFC3447] keys. In this case, the "algorithm" member value MUST be "RSA". Furthermore, these additional members MUST be present: +----------+--------+-----------------------------------------------+ | Member | JSON | Key Object Member Semantics | | Name | Value | | | | Type | | +----------+--------+-----------------------------------------------+ | modulus | string | The "modulus" member contains the modulus | | | | value for the RSA public key. It is | | | | represented as the base64url encoding of the | | | | value's big endian representation. | | exponent | string | The "exponent" member contains the exponent | | | | value for the RSA public key. It is | | | | represented as the base64url encoding of the | | | | value's big endian representation. | +----------+--------+-----------------------------------------------+ Members for RSA Keys 5. Base64url encoding as used by JWKs JWKs make use of the base64url encoding as defined in RFC 4648 [RFC4648]. As allowed by Section 3.2 of the RFC, this specification mandates that base64url encoding when used with JWKs MUST NOT use padding. Notes on implementing base64url encoding can be found in the JWS [JWS] specification. 6. IANA Considerations No IANA actions are required by this specification. Jones Expires October 31, 2011 [Page 6] Internet-Draft JSON Web Key (JWK) April 2011 7. Security Considerations TBD 8. References 8.1. Normative References [FIPS.186-3] National Institute of Standards and Technology, "Digital Signature Standard (DSS)", FIPS PUB 186-3, June 2009. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC 3447, February 2003. [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. 8.2. Informative References [JWS] Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer, J., Sakimura, N., and P. Tarjan, "JSON Web Signature (JWS)", April 2011. [MagicSignatures] Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic Signatures", August 2010. Appendix A. Acknowledgements A JSON representation for RSA public keys was previously introduced in Magic Signatures [MagicSignatures]. Appendix B. Document History -00 Jones Expires October 31, 2011 [Page 7] Internet-Draft JSON Web Key (JWK) April 2011 o Created first version based upon decisions made at the Internet Identity Workshop (IIW), as documented at http://self-issued.info/?p=390. Author's Address Michael B. Jones Microsoft Email: mbj@microsoft.com URI: http://self-issued.info/ Jones Expires October 31, 2011 [Page 8]