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Versions: 00

(No Working Group)                                           G. Amringer
Internet-Draft                                               Independent
Intended status: Informational                          November 7, 2018
Expires: May 11, 2019


  Chacha derived AEAD algorithms in JSON Object Signing and Encryption
                                 (JOSE)
                     draft-amringer-jose-chacha-00

Abstract

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

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 11, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notation and Conventions  . . . . . . . . . . . . . . . .   2
   2.  Key Management  . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   2
     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.  Content Encryption  . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Algorithms  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

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.arciszewski-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 Management

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.arciszewski-xchacha]).






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








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3.  Content Encryption

3.1.  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:

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

4.  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.arciszewski-xchacha]

   o Algorithm Name: "C20P"
   o Algorithm Description: ChaCha20-Poly1305
   o Algorithm Usage Location(s): "enc"
   o JOSE Implementation Requirements: Recommended



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   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.arciszewski-xchacha]

5.  Normative References

   [I-D.arciszewski-xchacha]
              Arciszewski, S., "XChaCha: eXtended-nonce ChaCha and
              AEAD_XChaCha20_Poly1305", draft-arciszewski-xchacha-02
              (work in progress), October 2018.

   [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>.

   [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>.

Author's Address

   Guillaume Amringer
   Independent
   Canada

   Email: g.amringer@gmail.com




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