JOSE Working Group M.B. Jones
Internet-Draft Microsoft
Intended status: Standards Track June 14, 2013
Expires: December 16, 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

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This Internet-Draft will expire on December 16, 2013.

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Table of Contents

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.

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

5. Security Considerations

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

6. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[JWE] Jones, M.B., Rescorla, E. and J. Hildebrand, "JSON Web Encryption (JWE)", Internet-Draft draft-ietf-jose-json-web-encryption, May 2013.
[JWA] Jones, M.B., "JSON Web Algorithms (JWA)", Internet-Draft draft-ietf-jose-json-web-algorithms, May 2013.
[AES] National Institute of Standards and Technology (NIST) , "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001.
[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.

Appendix A. Document History

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

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Author's Address

Michael B. Jones Microsoft EMail: mbj@microsoft.com URI: http://self-issued.info/