CBOR Object Signing and Encryption (COSE): Hash Algorithms
draft-ietf-cose-hash-algs-02
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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Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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
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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
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