CBOR Object Signing and Encryption (COSE): Hash Algorithms
draft-schaad-cose-hash-algs-00

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Network Working Group                                          J. Schaad
Internet-Draft                                            August Cellars
Intended status: Informational                         February 15, 2019
Expires: August 19, 2019

       CBOR Object Signing and Encryption (COSE): Hash Algorithms
                     draft-schaad-cose-hash-algs-00

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.

Note

   The source for this draft is being maintained in GitHub.  Suggested
   changes should be submitted as pull requests at TBD.  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.

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   This Internet-Draft will expire on August 19, 2019.

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Copyright Notice

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Table of Contents

   1.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.

   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
   [RFC5652].  This omission was intentional as a structure consisting
   of jut a digest identifier, the content, and a digest value does not
   by itself provide any strong security service.  Additional, an
   application is going to be better off defining this type of structure
   so that it can add 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
   makes a great deal of sense.  Two of the cases where these are going
   to be used are:

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   Indirect signing of content is a paradigm where the content is not
   directly signed, but instead a hash of the content is computed and
   that hash value, along with the hash algorithm, is included in the
   content that will be signed.  Doing indirect signing allows for the a
   signature to be validated without first downloading all of the
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