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Versions: 00 01                                                         
JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                           June 13, 2013
Expires: December 15, 2013


                   Key Wrapping with AES GCM for JWE
                  draft-jones-jose-aes-gcm-key-wrap-00

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 December 15, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  JSON Web Signature and Encryption Algorithms
           Registration  . . . . . . . . . . . . . . . . . . . . . . . 4
       4.1.1.  Registry Contents . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4
   Appendix A.  Document History . . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 5





































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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 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.

   Let JWE Encrypted Key value be the concatenation of the
   Initialization Vector value, the Ciphertext output, and the
   Authentication Tag output.

   During key decryption, the JWE Encrypted Key value is split into
   three inputs to the AES GCM decryption algorithm: the first 96 bits
   are the Initialization Vector value, the last 128 bits are the
   Authentication Tag value, and the remaining bits in between are the
   Ciphertext value.




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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 ]]


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),
              May 2013.

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




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


Appendix A.  Document History

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

   -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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