Use of the SHAKE One-Way Hash Functions in the Cryptographic Message Syntax (CMS)
RFC 8702

Document Type RFC - Proposed Standard (January 2020; No errata)
Updates RFC 3370
Last updated 2020-01-31
Replaces draft-dang-lamps-cms-shakes-hash
Stream IETF
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Document shepherd Russ Housley
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IESG IESG state RFC 8702 (Proposed Standard)
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Internet Engineering Task Force (IETF)                     P. Kampanakis
Request for Comments: 8702                                 Cisco Systems
Updates: 3370                                                    Q. Dang
Category: Standards Track                                           NIST
ISSN: 2070-1721                                             January 2020

  Use of the SHAKE One-Way Hash Functions in the Cryptographic Message
                              Syntax (CMS)


   This document updates the "Cryptographic Message Syntax (CMS)
   Algorithms" (RFC 3370) and describes the conventions for using the
   SHAKE family of hash functions in the Cryptographic Message Syntax as
   one-way hash functions with the RSA Probabilistic Signature Scheme
   (RSASSA-PSS) and Elliptic Curve Digital Signature Algorithm (ECDSA).
   The conventions for the associated signer public keys in CMS are also

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2020 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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   ( in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
     1.1.  Terminology
   2.  Identifiers
   3.  Use in CMS
     3.1.  Message Digests
     3.2.  Signatures
       3.2.1.  RSASSA-PSS Signatures
       3.2.2.  ECDSA Signatures
     3.3.  Public Keys
     3.4.  Message Authentication Codes
   4.  IANA Considerations
   5.  Security Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Appendix A.  ASN.1 Module
   Authors' Addresses

1.  Introduction

   "Cryptographic Message Syntax (CMS)" [RFC5652] describes syntax used
   to digitally sign, digest, authenticate, or encrypt arbitrary message
   contents.  "Cryptographic Message Syntax (CMS) Algorithms" [RFC3370]
   defines the use of common cryptographic algorithms with CMS.  This
   specification updates RFC 3370 and describes the use of the SHAKE128
   and SHAKE256 specified in [SHA3] as new hash functions in CMS.  In
   addition, it describes the use of these functions with the RSA
   Probabilistic Signature Scheme (RSASSA-PSS) signature algorithm
   [RFC8017] and the Elliptic Curve Digital Signature Algorithm (ECDSA)
   [X9.62] with the CMS signed-data content type.

   In the SHA-3 family, two extendable-output functions (SHAKEs),
   SHAKE128 and SHAKE256, are defined.  Four other hash function
   instances (SHA3-224, SHA3-256, SHA3-384, and SHA3-512) are also
   defined but are out of scope for this document.  A SHAKE is a
   variable-length hash function defined as SHAKE(M, d) where the output
   is a d-bit-long digest of message M.  The corresponding collision and
   second-preimage-resistance strengths for SHAKE128 are min(d/2,128)
   and min(d,128) bits, respectively (see Appendix A.1 of [SHA3]).  And
   the corresponding collision and second-preimage-resistance strengths
   for SHAKE256 are min(d/2,256) and min(d,256) bits, respectively.  In
   this specification, we use d=256 (for SHAKE128) and d=512 (for

   A SHAKE can be used in CMS as the message digest function (to hash
   the message to be signed) in RSASSA-PSS and ECDSA, as the message
   authentication code, and as the mask generation function (MGF) in
   RSASSA-PSS.  This specification describes the identifiers for SHAKEs
   to be used in CMS and their meanings.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Identifiers

   This section identifies eight new object identifiers (OIDs) for using
   SHAKE128 and SHAKE256 in CMS.

   Two object identifiers for SHAKE128 and SHAKE256 hash functions are
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