CBOR Encoded Message Syntax
draft-ietf-cose-msg-06
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COSE Working Group J. Schaad
Internet-Draft August Cellars
Intended status: Informational October 17, 2015
Expires: April 19, 2016
CBOR Encoded Message Syntax
draft-ietf-cose-msg-06
Abstract
Concise Binary Object Representation (CBOR) is data format designed
for small code size and small message size. There is a need for the
ability to have the basic security services defined for this data
format. This document specifies how to do signatures, message
authentication codes and encryption using this data format.
Contributing to this document
The source for this draft is being maintained in GitHub. Suggested
changes should be submitted as pull requests at <https://github.com/
cose-wg/cose-spec>. Instructions are on that page as well.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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 April 19, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
Schaad Expires April 19, 2016 [Page 1]
Internet-Draft CBOR Encoded Message Syntax October 2015
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Design changes from JOSE . . . . . . . . . . . . . . . . 5
1.2. Requirements Terminology . . . . . . . . . . . . . . . . 5
1.3. CBOR Grammar . . . . . . . . . . . . . . . . . . . . . . 6
1.4. CBOR Related Terminology . . . . . . . . . . . . . . . . 6
1.5. Document Terminology . . . . . . . . . . . . . . . . . . 7
1.6. Mandatory to Implement Algorithms . . . . . . . . . . . . 7
2. Basic COSE Structure . . . . . . . . . . . . . . . . . . . . 8
3. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Common COSE Headers Parameters . . . . . . . . . . . . . 10
4. Signing Structure . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Externally Supplied Data . . . . . . . . . . . . . . . . 15
4.2. Signing and Verification Process . . . . . . . . . . . . 15
4.3. Computing Counter Signatures . . . . . . . . . . . . . . 17
5. Encryption objects . . . . . . . . . . . . . . . . . . . . . 18
5.1. Enveloped COSE structure . . . . . . . . . . . . . . . . 18
5.1.1. Recipient Algorithm Classes . . . . . . . . . . . . . 19
5.2. Encrypted COSE structure . . . . . . . . . . . . . . . . 20
5.3. Encryption Algorithm for AEAD algorithms . . . . . . . . 20
5.4. Encryption algorithm for AE algorithms . . . . . . . . . 21
6. MAC objects . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.1. How to compute a MAC . . . . . . . . . . . . . . . . . . 23
7. Key Structure . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1. COSE Key Common Parameters . . . . . . . . . . . . . . . 24
8. Signature Algorithms . . . . . . . . . . . . . . . . . . . . 27
8.1. ECDSA . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.1.1. Security Considerations . . . . . . . . . . . . . . . 29
9. Message Authentication (MAC) Algorithms . . . . . . . . . . . 30
9.1. Hash-based Message Authentication Codes (HMAC) . . . . . 30
9.1.1. Security Considerations . . . . . . . . . . . . . . . 31
9.2. AES Message Authentication Code (AES-CBC-MAC) . . . . . . 32
9.2.1. Security Considerations . . . . . . . . . . . . . . . 32
10. Content Encryption Algorithms . . . . . . . . . . . . . . . . 33
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