JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                       December 27, 2012
Expires: June 30, 2013


                     JSON Private and Symmetric Key
           draft-jones-jose-json-private-and-symmetric-key-00

Abstract

   The JSON Private Key specification extends the JSON Web Key (JWK) and
   JSON Web Algorithms (JWA) specifications to define JavaScript Object
   Notation (JSON) representations of private keys and symmetric keys.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on June 30, 2013.

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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  JWK Parameters for Private Keys  . . . . . . . . . . . . . . .  3
     3.1.  JWK Parameters for Elliptic Curve Private Keys . . . . . .  3
       3.1.1.  "d" (ECC Private Key) Parameter  . . . . . . . . . . .  3
     3.2.  JWK Parameters for RSA Private Keys  . . . . . . . . . . .  3
       3.2.1.  "d" (Private Exponent) Parameter . . . . . . . . . . .  4
       3.2.2.  "p" (First Prime Factor) Parameter . . . . . . . . . .  4
       3.2.3.  "q" (Second Prime Factor) Parameter  . . . . . . . . .  4
       3.2.4.  "dp" (First Factor CRT Exponent) Parameter . . . . . .  4
       3.2.5.  "dq" (Second Factor CRT Exponent) Parameter  . . . . .  4
       3.2.6.  "qi" (First CRT Coefficient) Parameter . . . . . . . .  4
       3.2.7.  "oth" (Other Primes Info) Parameter  . . . . . . . . .  4
         3.2.7.1.  "r" (Prime Factor) . . . . . . . . . . . . . . . .  5
         3.2.7.2.  "d" (Factor CRT Exponent)  . . . . . . . . . . . .  5
         3.2.7.3.  "t" (Factor CRT Coefficient) . . . . . . . . . . .  5
   4.  JWK Parameters for Symmetric Keys  . . . . . . . . . . . . . .  5
     4.1.  "k" (Key Value) Parameter  . . . . . . . . . . . . . . . .  5
   5.  Example Private Keys . . . . . . . . . . . . . . . . . . . . .  5
   6.  Example Symmetric Keys . . . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
     7.1.  JSON Web Key Types Registration  . . . . . . . . . . . . .  7
       7.1.1.  Registry Contents  . . . . . . . . . . . . . . . . . .  7
     7.2.  JSON Web Key Parameters Registration . . . . . . . . . . .  7
       7.2.1.  Registry Contents  . . . . . . . . . . . . . . . . . .  7
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   9.  Normative References . . . . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . .  9
   Appendix B.  Document History  . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10


















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1.  Introduction

   The JSON Private Key specification extends the JSON Web Key (JWK)
   [JWK] and JSON Web Algorithms (JWA) [JWA] specifications to define
   JavaScript Object Notation (JSON) [RFC4627] representations of
   private and symmetric keys.

1.1.  Notational Conventions

   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 Key words for use in
   RFCs to Indicate Requirement Levels [RFC2119].


2.  Terminology

   This specification uses the same terminology as the JSON Web Key
   (JWK) [JWK] and JSON Web Algorithms (JWA) [JWA] specifications.


3.  JWK Parameters for Private Keys

   This section defines additional JSON Web Key parameters that enable
   JWKs to represent private keys.

3.1.  JWK Parameters for Elliptic Curve Private Keys

   When the JWK "kty" member value is "EC", the following member MAY be
   used to represent an Elliptic Curve private key:

3.1.1.  "d" (ECC Private Key) Parameter

   The "d" (ECC private key) member contains the Elliptic Curve private
   key value.  It is represented as the base64url encoding of the
   value's unsigned big endian representation as a byte array.  The
   array representation MUST not be shortened to omit any leading zero
   bytes.  For instance, when representing 521 bit integers, the byte
   array to be base64url encoded MUST contain 66 bytes, including any
   leading zero bytes.

3.2.  JWK Parameters for RSA Private Keys

   When the JWK "kty" member value is "RSA", the following member MAY be
   used to represent an RSA private key:






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3.2.1.  "d" (Private Exponent) Parameter

   The "d" (private exponent) member contains the private exponent value
   for the RSA private key.  It is represented as the base64url encoding
   of the value's unsigned big endian representation as a byte array.
   The array representation MUST not be shortened to omit any leading
   zero bytes.  For instance, when representing 2048 bit integers, the
   byte array to be base64url encoded MUST contain 256 bytes, including
   any leading zero bytes.

3.2.2.  "p" (First Prime Factor) Parameter

   The "p" (first prime factor) member contains the first prime factor,
   a positive integer.  It is represented as the base64url encoding of
   the value's unsigned big endian representation as a byte array.

3.2.3.  "q" (Second Prime Factor) Parameter

   The "q" (second prime factor) member contains the second prime
   factor, a positive integer.  It is represented as the base64url
   encoding of the value's unsigned big endian representation as a byte
   array.

3.2.4.  "dp" (First Factor CRT Exponent) Parameter

   The "dp" (first factor CRT exponent) member contains the Chinese
   Remainder Theorem (CRT) exponent of the first factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as a byte array.

3.2.5.  "dq" (Second Factor CRT Exponent) Parameter

   The "dq" (second factor CRT exponent) member contains the Chinese
   Remainder Theorem (CRT) exponent of the second factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as a byte array.

3.2.6.  "qi" (First CRT Coefficient) Parameter

   The "dp" (first CRT coefficient) member contains the Chinese
   Remainder Theorem (CRT) coefficient of the second factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as a byte array.

3.2.7.  "oth" (Other Primes Info) Parameter

   The "oth" (other primes info) member contains an array of information
   about any third and subsequent primes, should they exist.  When only



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   two primes have been used (the normal case), this parameter MUST be
   omitted.  When three or more primes have been used, the number of
   array elements MUST be the number of primes used minus two.  Each
   array element MUST be an object with the following members:

3.2.7.1.  "r" (Prime Factor)

   The "r" (prime factor) parameter within an "oth" array member
   represents the value of a subsequent prime factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as a byte array.

3.2.7.2.  "d" (Factor CRT Exponent)

   The "d" (Factor CRT Exponent) parameter within an "oth" array member
   represents the CRT exponent of the corresponding prime factor, a
   positive integer.  It is represented as the base64url encoding of the
   value's unsigned big endian representation as a byte array.

3.2.7.3.  "t" (Factor CRT Coefficient)

   The "t" (factor CRT coefficient) parameter within an "oth" array
   member represents the CRT coefficient of the corresponding prime
   factor, a positive integer.  It is represented as the base64url
   encoding of the value's unsigned big endian representation as a byte
   array.


4.  JWK Parameters for Symmetric Keys

   When the JWK "kty" member value is "oct" (octet sequence), the
   following member MAY be used to represent a symmetric key (or another
   key whose value is a single octet sequence):

4.1.  "k" (Key Value) Parameter

   The "k" (key value) member contains the value of the symmetric (or
   other single-valued) key.  It is represented as the base64url
   encoding of the octet sequence containing the key value.


5.  Example Private Keys

   The following example JWK Set contains two keys represented as JWKs
   containing both public and private key values: one using an Elliptic
   Curve algorithm and a second one using an RSA algorithm.  This
   example extends the example in Section 3 of [JWK], adding private key
   values.  (Line breaks are for display purposes only.)



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     {"keys":
       [
         {"kty":"EC",
          "crv":"P-256",
          "x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4",
          "y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM",
          "d":"870MB6gfuTJ4HtUnUvYMyJpr5eUZNP4Bk43bVdj3eAE",
          "use":"enc",
          "kid":"1"},

         {"kty":"RSA",
          "n":"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4
     cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMst
     n64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2Q
     vzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbIS
     D08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqbw
     0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw",
          "e":"AQAB",
          "d":"X4cTteJY_gn4FYPsXB8rdXix5vwsg1FLN5E3EaG6RJoVH-HLLKD9
     M7dx5oo7GURknchnrRweUkC7hT5fJLM0WbFAKNLWY2vv7B6NqXSzUvxT0_YSfqij
     wp3RTzlBaCxWp4doFk5N2o8Gy_nHNKroADIkJ46pRUohsXywbReAdYaMwFs9tv8d
     _cPVY3i07a3t8MN6TNwm0dSawm9v47UiCl3Sk5ZiG7xojPLu4sbg1U2jx4IBTNBz
     nbJSzFHK66jT8bgkuqsk0GjskDJk19Z4qwjwbsnn4j2WBii3RL-Us2lGVkY8fkFz
     me1z0HbIkfz0Y6mqnOYtqc0X4jfcKoAC8Q",
          "p":"83i-7IvMGXoMXCskv73TKr8637FiO7Z27zv8oj6pbWUQyLPQBQxtPV
     nwD20R-60eTDmD2ujnMt5PoqMrm8RfmNhVWDtjjMmCMjOpSXicFHj7XOuVIYQyqV
     WlWEh6dN36GVZYk93N8Bc9vY41xy8B9RzzOGVQzXvNEvn7O0nVbfs",
          "q":"3dfOR9cuYq-0S-mkFLzgItgMEfFzB2q3hWehMuG0oCuqnb3vobLyum
     qjVZQO1dIrdwgTnCdpYzBcOfW5r370AFXjiWft_NGEiovonizhKpo9VVS78TzFgx
     kIdrecRezsZ-1kYd_s1qDbxtkDEgfAITAG9LUnADun4vIcb6yelxk",
          "dp":"G4sPXkc6Ya9y8oJW9_ILj4xuppu0lzi_H7VTkS8xj5SdX3coE0oim
     YwxIi2emTAue0UOa5dpgFGyBJ4c8tQ2VF402XRugKDTP8akYhFo5tAA77Qe_Nmtu
     YZc3C3m3I24G2GvR5sSDxUyAN2zq8Lfn9EUms6rY3Ob8YeiKkTiBj0",
          "dq":"s9lAH9fggBsoFR8Oac2R_E2gw282rT2kGOAhvIllETE1efrA6huUU
     vMfBcMpn8lqeW6vzznYY5SSQF7pMdC_agI3nG8Ibp1BUb0JUiraRNqUfLhcQb_d9
     GF4Dh7e74WbRsobRonujTYN1xCaP6TO61jvWrX-L18txXw494Q_cgk",
          "qi":"GyM_p6JrXySiz1toFgKbWV-JdI3jQ4ypu9rbMWx3rQJBfmt0FoYzg
     UIZEVFEcOqwemRN81zoDAaa-Bk0KWNGDjJHZDdDmFhW3AN7lI-puxk_mHZGJ11rx
     yR8O55XLSe3SPmRfKwZI6yU24ZxvQKFYItdldUKGzO6Ia6zTKhAVRU",
          "alg":"RS256",
          "kid":"2011-04-29"}
       ]
     }








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6.  Example Symmetric Keys

   The following example JWK Set contains two symmetric keys represented
   as JWKs: one designated as being for use with the AES Key Wrap
   algorithm and a second one that is an HMAC key.  (Line breaks are for
   display purposes only.)

     {"keys":
       [
         {"kty":"oct",
          "alg":"A128KW",
          "k":"GawgguFyGrWKav7AX4VKUg"},

         {"kty":"oct",
          "k":"AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75
     aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow",
          "kid":"HMAC key used in JWS A.1 example"}
       ]
     }


7.  IANA Considerations

7.1.  JSON Web Key Types Registration

   This specification registers the key type defined in Section 4 in the
   IANA JSON Web Key Types registry [JWA].

7.1.1.  Registry Contents

   o  "kty" Parameter Value: "oct"
   o  Implementation Requirements: RECOMMENDED+
   o  Change Controller: IETF
   o  Specification Document(s): Section 4 of [[ this document ]]

7.2.  JSON Web Key Parameters Registration

   This specification registers the parameter names defined in
   Section 3.1, Section 3.2, and Section 4 in the IANA JSON Web Key
   Parameters registry [JWK].

7.2.1.  Registry Contents

   o  Parameter Name: "d"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1.1 of [[ this document ]]





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   o  Parameter Name: "d"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.1 of [[ this document ]]

   o  Parameter Name: "p"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.2 of [[ this document ]]

   o  Parameter Name: "q"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.3 of [[ this document ]]

   o  Parameter Name: "dp"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.4 of [[ this document ]]

   o  Parameter Name: "dq"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.5 of [[ this document ]]

   o  Parameter Name: "qi"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.6 of [[ this document ]]

   o  Parameter Name: "oth"
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.2.7 of [[ this document ]]

   o  Parameter Name: "k"
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]


8.  Security Considerations

   All of the security issues faced by any cryptographic application
   must be faced by a JWS/JWE/JWK agent.  Among these issues are
   protecting the user's private and symmetric keys, preventing various
   attacks, and helping the user avoid mistakes such as inadvertently
   encrypting a message for the wrong recipient.  The entire list of
   security considerations is beyond the scope of this document.

   Private and symmetric keys must be protected from disclosure to
   unintended parties.  One recommended means of doing so is to encrypt
   JWKs or JWK Sets containing them by using the JWK or JWK Set value as
   the plaintext of a JWE.

   A key is no more trustworthy than the method by which it was



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   received.

   The security considerations in RFC 3447 [RFC3447] and RFC 6030
   [RFC6030] about protecting private and symmetric keys also apply to
   this specification.


9.  Normative References

   [JWA]      Jones, M., "JSON Web Algorithms (JWA)",
              draft-ietf-jose-json-web-algorithms (work in progress),
              December 2012.

   [JWK]      Jones, M., "JSON Web Key (JWK)",
              draft-ietf-jose-json-web-key (work in progress),
              December 2012.

   [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.

   [RFC6030]  Hoyer, P., Pei, M., and S. Machani, "Portable Symmetric
              Key Container (PSKC)", RFC 6030, October 2010.


Appendix A.  Acknowledgements

   John Bradley and James Manger contributed to the contents of this
   specification.


Appendix B.  Document History

   [[ to be removed by the RFC editor before publication as an RFC ]]

   -00

   o  Created draft-jones-jose-json-private-and-symmetric-key from
      draft-jones-jose-json-private-key, adding a representation for
      symmetric keys.





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   o  Tracked parameter changes and additions in the JWK spec.

   o  Recommend encryption of JWKs and JWK Sets containing private or
      symmetric keys as JWEs.

   o  Added seriesInfo information to Internet Draft references.

   draft-jones-jose-json-private-key-01

   o  Changed the names of the RSA key parameters so that the
      identifiers are the same as those used in RFC 3447.

   o  Added the RSA private key fields enabling Chinese Remainder
      Theorem (CRT) calculations, based upon their use in RFC 3447.

   draft-jones-jose-json-private-key-00

   o  Created draft-jones-jose-json-private-key to facilitate discussion
      of the question from the W3C WebCrypto WG to the IETF JOSE WG of
      whether JOSE plans to support a format for representing private
      keys.


Author's Address

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/





















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