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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                           July 14, 2013
Expires: January 15, 2014


                   Key Wrapping with AES GCM for JWE
                  draft-jones-jose-aes-gcm-key-wrap-01

Abstract

   This specification defines how to encrypt (wrap) keys with the AES
   GCM algorithm for JSON Web Encryption (JWE) objects.

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 January 15, 2014.

Copyright Notice

   Copyright (c) 2013 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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   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.  Key Encryption with AES GCM . . . . . . . . . . . . . . . . . . 3
     3.1.  Header Parameters Used for AES GCM Key Encryption . . . . . 4
       3.1.1.  "iv" (Initialization Vector) Header Parameter . . . . . 4
       3.1.2.  "tag" (Authentication Tag) Header Parameter . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  JSON Web Signature and Encryption Algorithms
           Registration  . . . . . . . . . . . . . . . . . . . . . . . 4
       4.1.1.  Registry Contents . . . . . . . . . . . . . . . . . . . 4
     4.2.  Registration of JWE Header Parameter Names  . . . . . . . . 4
       4.2.1.  Registry Contents . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Document History . . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6
































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1.  Introduction

   This specification defines how to encrypt (wrap) keys with the AES
   GCM algorithm [AES] [NIST.800-38D] for JSON Web Encryption (JWE)
   [JWE] objects.

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
   Encryption (JWE) [JWE] and JSON Web Algorithms (JWA) [JWA]
   specifications.


3.  Key Encryption with AES GCM

   This section defines the specifics of encrypting a JWE Content
   Encryption Key (CEK) with Advanced Encryption Standard (AES) in
   Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 or 256 bit
   keys.  The "alg" header parameter values "A128GCMKW" or "A256GCMKW"
   are respectively used in this case.

   Use of an Initialization Vector of size 96 bits is REQUIRED with this
   algorithm.  The Initialization Vector is represented in base64url
   encoded form as the "iv" (initialization vector) header parameter
   value.

   The Additional Authenticated Data value used is the empty octet
   string.

   The requested size of the Authentication Tag output MUST be 128 bits,
   regardless of the key size.

   The JWE Encrypted Key value is the Ciphertext output.

   The Authentication Tag output is represented in base64url encoded
   form as the "tag" (authentication tag) header parameter value.







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3.1.  Header Parameters Used for AES GCM Key Encryption

   The following Header Parameter Names are used for AES GCM key
   encryption.  They MAY also be used by other algorithms if so
   specified by those algorithm parameter definitions.

3.1.1.  "iv" (Initialization Vector) Header Parameter

   The "iv" (initialization vector) header parameter value is the
   base64url encoded representation of the Initialization Vector value
   used for the key encryption operation.  This Header Parameter is
   REQUIRED and MUST be understood and processed by implementations when
   these algorithms are used.

3.1.2.  "tag" (Authentication Tag) Header Parameter

   The "tag" (authentication tag) header parameter value is the
   base64url encoded representation of the Authentication Tag value
   resulting from the key encryption operation.  This Header Parameter
   is REQUIRED and MUST be understood and processed by implementations
   when these algorithms are used.


4.  IANA Considerations

4.1.  JSON Web Signature and Encryption Algorithms Registration

   This specification registers the algorithms defined in Section 3 in
   the JSON Web Signature and Encryption Algorithms registry [JWA].

4.1.1.  Registry Contents

   o  Algorithm Name: "A128GCMKW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3 of [[ this document ]]

   o  Algorithm Name: "A256GCMKW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3 of [[ this document ]]

4.2.  Registration of JWE Header Parameter Names

   This specification registers the Header Parameter Names defined in
   Section 3.1 in the IANA JSON Web Signature and Encryption Header



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   Parameters registry [JWS].

4.2.1.  Registry Contents

   o  Header Parameter Name: "iv"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1.1 of [[ this document ]]

   o  Header Parameter Name: "tag"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1.2 of [[ this document ]]


5.  Security Considerations

   The security considerations in [AES] and [NIST.800-38D] also apply to
   this specification.


6.  Normative References

   [AES]      National Institute of Standards and Technology (NIST),
              "Advanced Encryption Standard (AES)", FIPS PUB 197,
              November 2001.

   [JWA]      Jones, M., "JSON Web Algorithms (JWA)",
              draft-ietf-jose-json-web-algorithms (work in progress),
              July 2013.

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", draft-ietf-jose-json-web-encryption
              (work in progress), July 2013.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", draft-ietf-jose-json-web-signature (work
              in progress), July 2013.

   [NIST.800-38D]
              National Institute of Standards and Technology (NIST),
              "Recommendation for Block Cipher Modes of Operation:
              Galois/Counter Mode (GCM) and GMAC", NIST PUB 800-38D,
              December 2001.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.




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Appendix A.  Document History

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

   -01

   o  Represented Initialization Vector and Authentication Tag values
      used as header parameter values so as to be more parallel with
      their treatment when using AES GCM for content encryption, per
      working group request.

   -00

   o  Created draft-jones-jose-aes-gcm-key-wrap.


Author's Address

   Michael B. Jones
   Microsoft

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




























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