CBOR Object Signing and Encryption (COSE): Hash Algorithms
draft-ietf-cose-hash-algs-02

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Network Working Group                                          J. Schaad
Internet-Draft                                            August Cellars
Intended status: Informational                           4 November 2019
Expires: 7 May 2020

       CBOR Object Signing and Encryption (COSE): Hash Algorithms
                      draft-ietf-cose-hash-algs-02

Abstract

   The CBOR Object Signing and Encryption (COSE) syntax
   [I-D.ietf-cose-rfc8152bis-struct] does not define any direct methods
   for using hash algorithms.  There are however circumstances where
   hash algorithms are used: Indirect signatures where the hash of one
   or more contents are signed.  X.509 certificate or other object
   identification by the use of a thumbprint.  This document defines a
   set of hash algorithms that are identified by COSE Algorithm
   Identifiers.

Contributing to this document

   This note is to be removed before publishing as an RFC.

   The source for this draft is being maintained in GitHub.  Suggested
   changes should be submitted as pull requests at https://github.com/
   cose-wg/X509 Editorial changes can be managed in GitHub, but any
   substantial issues need to be discussed on the COSE mailing list.

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
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on 7 May 2020.

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Copyright Notice

   Copyright (c) 2019 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
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     1.2.  Open Issues . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Hash Algorithm Usage  . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Example CBOR hash structure . . . . . . . . . . . . . . .   4
   3.  Hash Algorithm Identifiers  . . . . . . . . . . . . . . . . .   5
     3.1.  SHA-1 Hash Algorithm  . . . . . . . . . . . . . . . . . .   5
     3.2.  SHA-2 Hash Algorithms . . . . . . . . . . . . . . . . . .   6
     3.3.  SHAKE Algorithms  . . . . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  COSE Algorithm Registry . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The CBOR Object Signing and Encryption (COSE) syntax does not define
   any direct methods for the use of hash algorithms.  It also does not
   define a structure syntax that is used to encode a digested object
   structure along the lines of the DigestedData ASN.1 structure in
   [CMS].  This omission was intentional as a structure consisting of
   just a digest identifier, the content, and a digest value does not by
   itself provide any strong security service.  Additionally, an
   application is going to be better off defining this type of structure
   so that it can include any additional data that needs to be hashed,
   as well as methods of obtaining the data.

   While the above is true, there are some cases where having some
   standard hash algorithms defined for COSE with a common identifier

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   makes a great deal of sense.  Two of the cases where these are going
   to be used are:

   *  Indirect signing of content, and