Chacha derived AEAD algorithms in JSON Object Signing and Encryption (JOSE)
draft-amringer-jose-chacha-01

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(No Working Group)                                           G. Amringer
Internet-Draft                                             July 23, 2019
Intended status: Informational
Expires: January 24, 2020

  Chacha derived AEAD algorithms in JSON Object Signing and Encryption
                                 (JOSE)
                     draft-amringer-jose-chacha-01

Abstract

   This document defines how to use the AEAD algorithms
   "AEAD_XCHACHA20_POLY1305" and "AEAD_CHACHA20_POLY1305" from [RFC8439]
   and [I-D.irtf-cfrg-xchacha] in JSON Object Signing and Encryption
   (JOSE).

Status of This Memo

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   This Internet-Draft will expire on January 24, 2020.

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notation and Conventions  . . . . . . . . . . . . . . . .   2
   2.  Key Encryption  . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Header Parameters Used for Key Encryption . . . . . . . .   3
       2.2.1.  "iv" (Initialization Vector) Header Parameter . . . .   3
       2.2.2.  "tag" (Authentication Tag) Header Parameter . . . . .   3
   3.  Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral
       Static  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Content Encryption  . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Internet Research Task Force (IRTF) Crypto Forum Research Group
   (CFRG) defined the ChaCha20 and Poly1305 algorithms to be used in
   IETF protocols both independantly and as an AEAD construction
   ([RFC8439]).  It has also been presented with a definition of an
   eXtended-nonce variant ([I-D.irtf-cfrg-xchacha]) for use in stateless
   contexts.  This document defines how to use those algorithms in JOSE
   in an interoperable manner.

   This document defines the conventions to use in the context of
   [RFC7516], and [RFC7517].

1.1.  Notation and 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 [RFC2119].

   The JOSE key format ("JSON Web Key (JWK)") is defined by [RFC7517]
   and thumbprints for it ("JSON Web Key (JWK) Thumbprint") in
   [RFC7638].

2.  Key Encryption

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2.1.  Algorithms

   This section defines the specifics of encrypting a JWE Content
   Encryption Key (CEK) with AEAD_CHACHA20_POLY1305 [RFC8439] and
   AEAD_XCHACHA20_POLY1305 [I-D.irtf-cfrg-xchacha].

   Use of an Initialization Vector (IV) is REQUIRED with this algorithm.
   The IV 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 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.

   The following "alg" (algorithm) Header Parameter values are used to
   indicate that the JWE Encrypted Key is the result of encrypting the
   CEK using the corresponding algorithm and IV size:

           +-------------------------+----------+-------------+
           |        Algorithm        | IV size  | "alg" value |
           +-------------------------+----------+-------------+
           |  AEAD_CHACHA20_POLY1305 | 96 bits  |    C20PKW   |
           | AEAD_XCHACHA20_POLY1305 | 192 bits |   XC20PKW   |
           +-------------------------+----------+-------------+

2.2.  Header Parameters Used for Key Encryption

   The following Header Parameters are used for both algorithms defined
   for key encryption.

2.2.1.  "iv" (Initialization Vector) Header Parameter

   The "iv" (initialization vector) Header Parameter value is the
   base64url-encoded representation of the 96-bit or 192-bit IV value
   used for the key encryption operation.  This Header Parameter MUST be
   present and MUST be understood and processed by implementations when
   these algorithms are used.

2.2.2.  "tag" (Authentication Tag) Header Parameter

   The "tag" (authentication tag) Header Parameter value is the
   base64url-encoded representation of the 128-bit Authentication Tag
   value resulting from the key encryption operation.  This Header

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   Parameter MUST be present and MUST be understood and processed by
   implementations when these algorithms are used.

3.  Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static

   This section defines the specifics of key agreement with Elliptic
   Curve Diffie-Hellman Ephemeral Static [RFC6090], in combination with
   the Concat KDF, as defined in Section 5.8.2.1 of NIST.800-56A [1] for
   use as a symmetric key to wrap the CEK with the "C20PKW", or
   "XC20PKW" algorithms, in the Key Agreement with Key Wrapping mode.

   This mode is used exactly as defined in Section 4.6 of RFC7518 [2],
   except that the combined key wrapping algorithms are the ones
   indicated in this document.  All headers pertaining to both the ECDH-
   ES and key wrapping components ("iv",' "tag", "epk", "apu", "apv")
   have the same meaning and requirement as in their original
   definitions.

   The following "alg" (algorithm) Header Parameter values are used to
   indicate that the JWE Encrypted Key is the result of encrypting the
   CEK using the corresponding algorithm:

   +-----------------+-------------------------------------------------+
   |   "alg" value   |             Key Management Algorithm            |
   +-----------------+-------------------------------------------------+
   |  ECDH-ES+C20PKW |  ECDH-ES using Concat KDF and CEK wrapped with  |
   |                 |                      C20PKW                     |
   | ECDH-ES+XC20PKW |  ECDH-ES using Concat KDF and CEK wrapped with  |
   |                 |                     XC20PKW                     |
   +-----------------+-------------------------------------------------+

4.  Content Encryption

4.1.  Algorithms

   This section defines the specifics of performing authenticated
   encryption with ChaCha20-Poly1305.

   The CEK is used as the encryption key.

   Use of an IV is REQUIRED with this algorithm.

   The following "enc" (encryption algorithm) Header Parameter values
   are used to indicate that the JWE Ciphertext and JWE Authentication
   Tag values have been computed using the corresponding algorithm and
   IV size:

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           +-------------------------+----------+-------------+
           |        Algorithm        | IV size  | "alg" value |
           +-------------------------+----------+-------------+
           |  AEAD_CHACHA20_POLY1305 | 96 bits  |     C20P    |
           | AEAD_XCHACHA20_POLY1305 | 192 bits |    XC20P    |
           +-------------------------+----------+-------------+

5.  IANA Considerations

   The following is added to the "JSON Web Signature and Encryption
   Algorithms" registry:

   o Algorithm Name: "C20PKW" o Algorithm Description: Key wrapping with
   ChaCha20-Poly1305 o Algorithm Usage Location(s): "alg" o JOSE
   Implementation Requirements: Recommended o Change Controller: IESG o
   Specification Document(s): Section 2 of [RFC-THIS] o Algorithm
   Analysis Documents(s): [RFC8439]

   o Algorithm Name: "XC20PKW" o Algorithm Description: Key wrapping
   with XChaCha20-Poly1305 o Algorithm Usage Location(s): "alg" o JOSE
   Implementation Requirements: Recommended o Change Controller: IESG o
   Specification Document(s): Section 2 of [RFC-THIS] o Algorithm
   Analysis Documents(s): [I-D.irtf-cfrg-xchacha]

   o Algorithm Name: "C20P" o Algorithm Description: ChaCha20-Poly1305 o
   Algorithm Usage Location(s): "enc" o JOSE Implementation
   Requirements: Recommended o Change Controller: IESG o Specification
   Document(s): Section 3 of [RFC-THIS] o Algorithm Analysis
   Documents(s): [RFC8439]

   o Algorithm Name: "XC20P" o Algorithm Description: ChaCha20-Poly1305
   o Algorithm Usage Location(s): "enc" o JOSE Implementation
   Requirements: Recommended o Change Controller: IESG o Specification
   Document(s): Section 3 of [RFC-THIS] o Algorithm Analysis
   Documents(s): [I-D.irtf-cfrg-xchacha]

6.  References

6.1.  Normative References

   [I-D.irtf-cfrg-xchacha]
              Arciszewski, S., "XChaCha: eXtended-nonce ChaCha and
              AEAD_XChaCha20_Poly1305", draft-irtf-cfrg-xchacha-01 (work
              in progress), July 2019.

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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
              Curve Cryptography Algorithms", RFC 6090,
              DOI 10.17487/RFC6090, February 2011,
              <https://www.rfc-editor.org/info/rfc6090>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <https://www.rfc-editor.org/info/rfc7516>.

   [RFC7517]  Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015,
              <https://www.rfc-editor.org/info/rfc7517>.

   [RFC7638]  Jones, M. and N. Sakimura, "JSON Web Key (JWK)
              Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
              2015, <https://www.rfc-editor.org/info/rfc7638>.

   [RFC8439]  Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
              Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018,
              <https://www.rfc-editor.org/info/rfc8439>.

6.2.  URIs

   [1] https://csrc.nist.gov/publications/detail/sp/800-56a/rev-3/final

   [2] https://tools.ietf.org/html/rfc7518#section-4.6

Author's Address

   Guillaume Amringer
   Canada

   Email: g.amringer@gmail.com

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