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.

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

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Table of Contents

• 1. Introduction
• 1.1. Notational Conventions
• 2. Terminology
• 3. Key Encryption with AES GCM
• 4. IANA Considerations
• 4.1. JSON Web Signature and Encryption Algorithms Registration
• 4.1.1. 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] [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

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

• Algorithm Name: A256GCMKW
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• 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

Appendix A. Document History

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

-00

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

Author's Address