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

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Copyright Notice

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Table of Contents

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

1.  Introduction

This specification defines how to encrypt (wrap) keys with the AES GCM algorithm [AES] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” 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,” December 2001.) for JSON Web Encryption (JWE) [JWE] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” July 2013.) 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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

2.  Terminology

This specification uses the same terminology as the JSON Web Encryption (JWE) [JWE] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” July 2013.) and JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” July 2013.) 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] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” 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,” December 2001.) 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.

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 (Key Encryption with AES GCM) in the JSON Web Signature and Encryption Algorithms registry [JWA] (Jones, M., “JSON Web Algorithms (JWA),” July 2013.).

4.1.1.  Registry Contents

• Algorithm Name: A128GCMKW
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3 (Key Encryption with AES GCM) of [[ this document ]]

• Algorithm Name: A256GCMKW
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3 (Key Encryption with AES GCM) of [[ this document ]]

4.2.  Registration of JWE Header Parameter Names

This specification registers the Header Parameter Names defined in Section 3.1 (Header Parameters Used for AES GCM Key Encryption) in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” July 2013.).

4.2.1.  Registry Contents

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

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

5.  Security Considerations

The security considerations in [AES] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) and [NIST.800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.) also apply to this specification.

6. Normative References

Appendix A.  Document History

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

-01

• 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

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

Author's Address