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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                        January 16, 2012
Expires: July 19, 2012


                           JSON Web Key (JWK)
                    draft-ietf-jose-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 July 19, 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
   (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



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   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 . . . . . . . . . . . . . . . . . . . 5
       4.2.1.  JWK Key Object Members for Elliptic Curve Keys  . . . . 5
       4.2.2.  JWK Key Object Members for RSA Keys . . . . . . . . . . 6
   5.  Base64url encoding as used by JWKs  . . . . . . . . . . . . . . 7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   8.  Open Issues and Things To Be Done (TBD) . . . . . . . . . . . . 7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . . . 8
   Appendix B.  Document History . . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8

























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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 Signature (JWS) [JWS] using the "jku" (JSON Key URL) header
   parameter and in JSON Web Encryption (JWE) [JWE] using the "jku"
   (JSON Key URL) and "epk" (Ephemeral Public Key) header parameters.


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 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.  JSON Web Key (JWK) Overview

   It is sometimes useful to be able to reference public key
   representations, for instance, in order to verify the digital
   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 Elliptic
   Curve or RSA families of algorithms.

3.1.  Example JWK

   The following example JWK contains two public keys: 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 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.)



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   {"jwk":
     [
       {"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.  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     |                                               |
   +--------+----------+-----------------------------------------------+
   | jwk    | array    | The "jwk" member value contains an array of   |
   |        |          | JWK 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.





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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:

   +--------+--------+-------------------------------------------------+
   | Member | JSON   | Key Object Member Semantics                     |
   | Name   | Value  |                                                 |
   |        | Type   |                                                 |
   +--------+--------+-------------------------------------------------+
   | alg    | string | The "alg" member identifies the cryptographic   |
   |        |        | algorithm family used with the key.  Values     |
   |        |        | defined by this specification are "EC" and      |
   |        |        | "RSA".  Specific additional members are         |
   |        |        | required to represent the key, depending upon   |
   |        |        | the "alg" value.  The "alg" value is case       |
   |        |        | sensitive.  This member is REQUIRED.            |
   | use    | string | The "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.  This member is OPTIONAL.       |
   | kid    | string | 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.  The "kid" value   |
   |        |        | MAY correspond to a JWS "kid" value.  The       |
   |        |        | interpretation of the "kid" 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 Elliptic Curve Keys

   JWKs can represent Elliptic Curve [FIPS.186-3] keys.  In this case,
   the "alg" member value MUST be "EC".  Furthermore, these additional
   members MUST be present:










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   +--------+--------+-------------------------------------------------+
   | Member | JSON   | Key Object Member Semantics                     |
   | Name   | Value  |                                                 |
   |        | Type   |                                                 |
   +--------+--------+-------------------------------------------------+
   | crv    | string | The "crv" member identifies the cryptographic   |
   |        |        | curve used with the key.  Values defined by     |
   |        |        | this specification are "P-256", "P-384" and     |
   |        |        | "P-521".  Additional "crv" values MAY be used,  |
   |        |        | provided they are understood by implementations |
   |        |        | using that Elliptic Curve key.  The "crv" value |
   |        |        | is case sensitive.                              |
   | 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 Elliptic Curve Keys

4.2.2.  JWK Key Object Members for RSA Keys

   JWKs can represent RSA [RFC3447] keys.  In this case, the "alg"
   member value MUST be "RSA".  Furthermore, these additional members
   MUST be present:

   +--------+--------+-------------------------------------------------+
   | Member | JSON   | Key Object Member Semantics                     |
   | Name   | Value  |                                                 |
   |        | Type   |                                                 |
   +--------+--------+-------------------------------------------------+
   | mod    | string | The "mod" member contains the modulus value for |
   |        |        | the RSA public key.  It is represented as the   |
   |        |        | base64url encoding of the value's big endian    |
   |        |        | representation.                                 |
   | exp    | string | The "exp" 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





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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.


7.  Security Considerations

   TBD


8.  Open Issues and Things To Be Done (TBD)

   The following items remain to be done in this draft:

   o  Write the Security Considerations section.


9.  References

9.1.  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.





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9.2.  Informative References

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", January 2012.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", January 2012.

   [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

   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/

















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