draft-ietf-cose-msg-05.txt   draft-ietf-cose-msg-06.txt 
COSE Working Group J. Schaad COSE Working Group J. Schaad
Internet-Draft August Cellars Internet-Draft August Cellars
Intended status: Informational B. Campbell Intended status: Informational October 17, 2015
Expires: March 24, 2016 Ping Identity Expires: April 19, 2016
September 21, 2015
CBOR Encoded Message Syntax CBOR Encoded Message Syntax
draft-ietf-cose-msg-05 draft-ietf-cose-msg-06
Abstract Abstract
Concise Binary Object Representation (CBOR) is data format designed Concise Binary Object Representation (CBOR) is data format designed
for small code size and small message size. There is a need for the 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 ability to have the basic security services defined for this data
format. This document specifies how to do signatures, message format. This document specifies how to do signatures, message
authentication codes and encryption using this data format. authentication codes and encryption using this data format.
Contributing to this document Contributing to this document
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 24, 2016. This Internet-Draft will expire on April 19, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Design changes from JOSE . . . . . . . . . . . . . . . . 5 1.1. Design changes from JOSE . . . . . . . . . . . . . . . . 5
1.2. Requirements Terminology . . . . . . . . . . . . . . . . 5 1.2. Requirements Terminology . . . . . . . . . . . . . . . . 5
1.3. CBOR Grammar . . . . . . . . . . . . . . . . . . . . . . 6 1.3. CBOR Grammar . . . . . . . . . . . . . . . . . . . . . . 6
1.4. CBOR Related Terminology . . . . . . . . . . . . . . . . 6 1.4. CBOR Related Terminology . . . . . . . . . . . . . . . . 6
1.5. Document Terminology . . . . . . . . . . . . . . . . . . 7 1.5. Document Terminology . . . . . . . . . . . . . . . . . . 7
1.6. Mandatory to Implement Algorithms . . . . . . . . . . . . 7 1.6. Mandatory to Implement Algorithms . . . . . . . . . . . . 7
2. The COSE_MSG structure . . . . . . . . . . . . . . . . . . . 8 2. Basic COSE Structure . . . . . . . . . . . . . . . . . . . . 8
3. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 9 3. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Common COSE Headers Parameters . . . . . . . . . . . . . 11 3.1. Common COSE Headers Parameters . . . . . . . . . . . . . 10
4. Signing Structure . . . . . . . . . . . . . . . . . . . . . . 14 4. Signing Structure . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Externally Supplied Data . . . . . . . . . . . . . . . . 16 4.1. Externally Supplied Data . . . . . . . . . . . . . . . . 15
4.2. Signing and Verification Process . . . . . . . . . . . . 16 4.2. Signing and Verification Process . . . . . . . . . . . . 15
4.3. Computing Counter Signatures . . . . . . . . . . . . . . 18 4.3. Computing Counter Signatures . . . . . . . . . . . . . . 17
5. Encryption objects . . . . . . . . . . . . . . . . . . . . . 19 5. Encryption objects . . . . . . . . . . . . . . . . . . . . . 18
5.1. Enveloped COSE structure . . . . . . . . . . . . . . . . 19 5.1. Enveloped COSE structure . . . . . . . . . . . . . . . . 18
5.1.1. Recipient Algorithm Classes . . . . . . . . . . . . . 20 5.1.1. Recipient Algorithm Classes . . . . . . . . . . . . . 19
5.2. Encrypted COSE structure . . . . . . . . . . . . . . . . 21 5.2. Encrypted COSE structure . . . . . . . . . . . . . . . . 20
5.3. Encryption Algorithm for AEAD algorithms . . . . . . . . 21 5.3. Encryption Algorithm for AEAD algorithms . . . . . . . . 20
5.4. Encryption algorithm for AE algorithms . . . . . . . . . 22 5.4. Encryption algorithm for AE algorithms . . . . . . . . . 21
6. MAC objects . . . . . . . . . . . . . . . . . . . . . . . . . 23 6. MAC objects . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.1. How to compute a MAC . . . . . . . . . . . . . . . . . . 24 6.1. How to compute a MAC . . . . . . . . . . . . . . . . . . 23
7. Key Structure . . . . . . . . . . . . . . . . . . . . . . . . 25 7. Key Structure . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1. COSE Key Common Parameters . . . . . . . . . . . . . . . 25 7.1. COSE Key Common Parameters . . . . . . . . . . . . . . . 24
8. Signature Algorithms . . . . . . . . . . . . . . . . . . . . 28 8. Signature Algorithms . . . . . . . . . . . . . . . . . . . . 27
8.1. ECDSA . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.1. ECDSA . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.1.1. Security Considerations . . . . . . . . . . . . . . . 30 8.1.1. Security Considerations . . . . . . . . . . . . . . . 29
8.2. RSASSA-PSS . . . . . . . . . . . . . . . . . . . . . . . 31 9. Message Authentication (MAC) Algorithms . . . . . . . . . . . 30
8.2.1. Security Considerations . . . . . . . . . . . . . . . 31 9.1. Hash-based Message Authentication Codes (HMAC) . . . . . 30
9. Message Authentication (MAC) Algorithms . . . . . . . . . . . 32 9.1.1. Security Considerations . . . . . . . . . . . . . . . 31
9.1. Hash-based Message Authentication Codes (HMAC) . . . . . 32 9.2. AES Message Authentication Code (AES-CBC-MAC) . . . . . . 32
9.1.1. Security Considerations . . . . . . . . . . . . . . . 33 9.2.1. Security Considerations . . . . . . . . . . . . . . . 32
9.2. AES Message Authentication Code (AES-CBC-MAC) . . . . . . 34 10. Content Encryption Algorithms . . . . . . . . . . . . . . . . 33
9.2.1. Security Considerations . . . . . . . . . . . . . . . 34 10.1. AES GCM . . . . . . . . . . . . . . . . . . . . . . . . 33
10. Content Encryption Algorithms . . . . . . . . . . . . . . . . 35 10.1.1. Security Considerations . . . . . . . . . . . . . . 34
10.1. AES GCM . . . . . . . . . . . . . . . . . . . . . . . . 35 10.2. AES CCM . . . . . . . . . . . . . . . . . . . . . . . . 34
10.1.1. Security Considerations . . . . . . . . . . . . . . 36 10.2.1. Security Considerations . . . . . . . . . . . . . . 37
10.2. AES CCM . . . . . . . . . . . . . . . . . . . . . . . . 36 10.3. ChaCha20 and Poly1305 . . . . . . . . . . . . . . . . . 37
10.2.1. Security Considerations . . . . . . . . . . . . . . 39 10.3.1. Security Considerations . . . . . . . . . . . . . . 38
10.3. ChaCha20 and Poly1305 . . . . . . . . . . . . . . . . . 39 11. Key Derivation Functions (KDF) . . . . . . . . . . . . . . . 38
10.3.1. Security Considerations . . . . . . . . . . . . . . 40
11. Key Derivation Functions (KDF) . . . . . . . . . . . . . . . 40
11.1. HMAC-based Extract-and-Expand Key Derivation Function 11.1. HMAC-based Extract-and-Expand Key Derivation Function
(HKDF) . . . . . . . . . . . . . . . . . . . . . . . . . 41 (HKDF) . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.2. Context Information Structure . . . . . . . . . . . . . 42 11.2. Context Information Structure . . . . . . . . . . . . . 40
12. Recipient Algorithm Classes . . . . . . . . . . . . . . . . . 46 12. Recipient Algorithm Classes . . . . . . . . . . . . . . . . . 44
12.1. Direct Encryption . . . . . . . . . . . . . . . . . . . 46 12.1. Direct Encryption . . . . . . . . . . . . . . . . . . . 44
12.1.1. Direct Key . . . . . . . . . . . . . . . . . . . . . 47 12.1.1. Direct Key . . . . . . . . . . . . . . . . . . . . . 45
12.1.2. Direct Key with KDF . . . . . . . . . . . . . . . . 47 12.1.2. Direct Key with KDF . . . . . . . . . . . . . . . . 45
12.2. Key Wrapping . . . . . . . . . . . . . . . . . . . . . . 49 12.2. Key Wrapping . . . . . . . . . . . . . . . . . . . . . . 47
12.2.1. AES Key Wrapping . . . . . . . . . . . . . . . . . . 49 12.2.1. AES Key Wrapping . . . . . . . . . . . . . . . . . . 47
12.3. Key Encryption . . . . . . . . . . . . . . . . . . . . . 50 12.3. Key Encryption . . . . . . . . . . . . . . . . . . . . . 48
12.3.1. RSAES-OAEP . . . . . . . . . . . . . . . . . . . . . 50 12.4. Direct Key Agreement . . . . . . . . . . . . . . . . . . 48
12.4. Direct Key Agreement . . . . . . . . . . . . . . . . . . 51 12.4.1. ECDH . . . . . . . . . . . . . . . . . . . . . . . . 49
12.4.1. ECDH . . . . . . . . . . . . . . . . . . . . . . . . 52 12.5. Key Agreement with KDF . . . . . . . . . . . . . . . . . 53
12.5. Key Agreement with KDF . . . . . . . . . . . . . . . . . 56 12.5.1. ECDH . . . . . . . . . . . . . . . . . . . . . . . . 53
12.5.1. ECDH . . . . . . . . . . . . . . . . . . . . . . . . 56 13. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
13. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 13.1. Elliptic Curve Keys . . . . . . . . . . . . . . . . . . 54
13.1. Elliptic Curve Keys . . . . . . . . . . . . . . . . . . 57 13.1.1. Double Coordinate Curves . . . . . . . . . . . . . . 54
13.1.1. Single Coordinate Curves . . . . . . . . . . . . . . 58 13.2. Symmetric Keys . . . . . . . . . . . . . . . . . . . . . 55
13.1.2. Double Coordinate Curves . . . . . . . . . . . . . . 58 14. CBOR Encoder Restrictions . . . . . . . . . . . . . . . . . . 56
13.2. RSA Keys . . . . . . . . . . . . . . . . . . . . . . . . 60 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56
13.3. Symmetric Keys . . . . . . . . . . . . . . . . . . . . . 61 15.1. CBOR Tag assignment . . . . . . . . . . . . . . . . . . 56
14. CBOR Encoder Restrictions . . . . . . . . . . . . . . . . . . 62 15.2. COSE Header Parameter Registry . . . . . . . . . . . . . 57
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 62 15.3. COSE Header Algorithm Label Table . . . . . . . . . . . 58
15.1. CBOR Tag assignment . . . . . . . . . . . . . . . . . . 62 15.4. COSE Algorithm Registry . . . . . . . . . . . . . . . . 58
15.2. COSE Header Parameter Registry . . . . . . . . . . . . . 62 15.5. COSE Key Common Parameter Registry . . . . . . . . . . . 59
15.3. COSE Header Algorithm Label Table . . . . . . . . . . . 63 15.6. COSE Key Type Parameter Registry . . . . . . . . . . . . 60
15.4. COSE Algorithm Registry . . . . . . . . . . . . . . . . 64 15.7. COSE Elliptic Curve Registry . . . . . . . . . . . . . . 60
15.5. COSE Key Common Parameter Registry . . . . . . . . . . . 65 15.8. Media Type Registrations . . . . . . . . . . . . . . . . 61
15.6. COSE Key Type Parameter Registry . . . . . . . . . . . . 65 15.8.1. COSE Security Message . . . . . . . . . . . . . . . 61
15.7. COSE Elliptic Curve Registry . . . . . . . . . . . . . . 66 15.8.2. COSE Key media type . . . . . . . . . . . . . . . . 63
15.8. Media Type Registration . . . . . . . . . . . . . . . . 67 15.9. CoAP Content Format Registrations . . . . . . . . . . . 65
15.8.1. COSE Security Message . . . . . . . . . . . . . . . 67 16. Security Considerations . . . . . . . . . . . . . . . . . . . 65
15.8.2. COSE Key media type . . . . . . . . . . . . . . . . 69 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 66
16. Security Considerations . . . . . . . . . . . . . . . . . . . 70 17.1. Normative References . . . . . . . . . . . . . . . . . . 66
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 71 17.2. Informative References . . . . . . . . . . . . . . . . . 66
17.1. Normative References . . . . . . . . . . . . . . . . . . 71 Appendix A. CDDL Grammar . . . . . . . . . . . . . . . . . . . . 68
17.2. Informative References . . . . . . . . . . . . . . . . . 71 Appendix B. Three Levels of Recipient Information . . . . . . . 69
Appendix A. CDDL Grammar . . . . . . . . . . . . . . . . . . . . 74 Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 70
Appendix B. Three Levels of Recipient Information . . . . . . . 74 C.1. Examples of MAC messages . . . . . . . . . . . . . . . . 71
Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 76 C.1.1. Shared Secret Direct MAC . . . . . . . . . . . . . . 71
C.1. Examples of MAC messages . . . . . . . . . . . . . . . . 76 C.1.2. ECDH Direct MAC . . . . . . . . . . . . . . . . . . . 72
C.1.1. Shared Secret Direct MAC . . . . . . . . . . . . . . 76 C.1.3. Wrapped MAC . . . . . . . . . . . . . . . . . . . . . 73
C.1.2. ECDH Direct MAC . . . . . . . . . . . . . . . . . . . 77 C.1.4. Multi-recipient MAC message . . . . . . . . . . . . . 74
C.1.3. Wrapped MAC . . . . . . . . . . . . . . . . . . . . . 78 C.2. Examples of Encrypted Messages . . . . . . . . . . . . . 75
C.1.4. Multi-recipient MAC message . . . . . . . . . . . . . 79 C.2.1. Direct ECDH . . . . . . . . . . . . . . . . . . . . . 75
C.2. Examples of Encrypted Messages . . . . . . . . . . . . . 81 C.2.2. Direct plus Key Derivation . . . . . . . . . . . . . 76
C.2.1. Direct ECDH . . . . . . . . . . . . . . . . . . . . . 81 C.3. Examples of Signed Message . . . . . . . . . . . . . . . 77
C.2.2. Direct plus Key Derivation . . . . . . . . . . . . . 81 C.3.1. Single Signature . . . . . . . . . . . . . . . . . . 77
C.3. Examples of Signed Message . . . . . . . . . . . . . . . 82 C.3.2. Multiple Signers . . . . . . . . . . . . . . . . . . 78
C.3.1. Single Signature . . . . . . . . . . . . . . . . . . 82 C.4. COSE Keys . . . . . . . . . . . . . . . . . . . . . . . . 78
C.3.2. Multiple Signers . . . . . . . . . . . . . . . . . . 83 C.4.1. Public Keys . . . . . . . . . . . . . . . . . . . . . 78
C.4. COSE Keys . . . . . . . . . . . . . . . . . . . . . . . . 84 C.4.2. Private Keys . . . . . . . . . . . . . . . . . . . . 81
C.4.1. Public Keys . . . . . . . . . . . . . . . . . . . . . 84 Appendix D. Document Updates . . . . . . . . . . . . . . . . . . 82
C.4.2. Private Keys . . . . . . . . . . . . . . . . . . . . 86 D.1. Version -05 to -06 . . . . . . . . . . . . . . . . . . . 82
Appendix D. Document Updates . . . . . . . . . . . . . . . . . . 88 D.2. Version -04 to -05 . . . . . . . . . . . . . . . . . . . 83
D.1. Version -04 to -05 . . . . . . . . . . . . . . . . . . . 89 D.3. Version -03 to -04 . . . . . . . . . . . . . . . . . . . 83
D.2. Version -03 to -04 . . . . . . . . . . . . . . . . . . . 89 D.4. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 83
D.3. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 89 D.5. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 83
D.4. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 89 D.6. Version -01 to -2 . . . . . . . . . . . . . . . . . . . . 84
D.5. Version -01 to -2 . . . . . . . . . . . . . . . . . . . . 90 D.7. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 84
D.6. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 90 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 85
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 92
1. Introduction 1. Introduction
There has been an increased focus on the small, constrained devices There has been an increased focus on the small, constrained devices
that make up the Internet of Things (IOT). One of the standards that that make up the Internet of Things (IOT). One of the standards that
has come of of this process is the Concise Binary Object has come out of this process is the Concise Binary Object
Representation (CBOR). CBOR extended the data model of the Representation (CBOR). CBOR extended the data model of the
JavaScript Object Notation (JSON) by allowing for binary data among JavaScript Object Notation (JSON) by allowing for binary data among
other changes. CBOR is being adopted by several of the IETF working other changes. CBOR is being adopted by several of the IETF working
groups dealing with the IOT world as their encoding of data groups dealing with the IOT world as their encoding of data
structures. CBOR was designed specifically to be both small in terms structures. CBOR was designed specifically to be both small in terms
of messages transport and implementation size as well having a schema of messages transport and implementation size as well having a schema
free decoder. A need exists to provide basic message security free decoder. A need exists to provide basic message security
services for IOT and using CBOR as the message encoding format makes services for IOT and using CBOR as the message encoding format makes
sense. sense.
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The document was developed by first working on the grammar and then The document was developed by first working on the grammar and then
developing the prose to go with it. An artifact of this is that the developing the prose to go with it. An artifact of this is that the
prose was written using the primitive type strings defined by early prose was written using the primitive type strings defined by early
versions CDDL. In this specification the following primitive types versions CDDL. In this specification the following primitive types
are used: are used:
bstr - byte string (major type 2). bstr - byte string (major type 2).
int - an unsigned integer or a negative integer. int - an unsigned integer or a negative integer.
nil - a null value (tag 7.22). nil - a null value (major type 7, value 22).
nint - a negative integer (major type 1). nint - a negative integer (major type 1).
tstr - a UTF-8 text string (major type 3). tstr - a UTF-8 text string (major type 3).
uint - an unsigned integer (major type 0). uint - an unsigned integer (major type 0).
Text from here to start of next section to be removed Text from here to start of next section to be removed
NOTE: For the purposes of review, we are currently interlacing the NOTE: For the purposes of review, we are currently interlacing the
CDLL grammar into the text of document. This is being done for CDDL grammar into the text of document. This is being done for
simplicity of comparision of the grammar againist the prose. The simplicity of comparison of the grammar against the prose. The
grammar will be removed to an appendix during WGLC. grammar will be removed to an appendix during WGLC.
start = COSE_MSG / COSE_Tagged_MSG / COSE_Key / COSE_KeySet start = COSE_Untagged_Message / COSE_Tagged_Message /
COSE_Key / COSE_KeySet
1.4. CBOR Related Terminology 1.4. CBOR Related Terminology
In JSON, maps are called objects and only have one kind of map key: a In JSON, maps are called objects and only have one kind of map key: a
string. In COSE, we use both strings and integers (both negative and string. In COSE, we use both strings and integers (both negative and
non-negative integers) as map keys, as well as data items to identify non-negative integers) as map keys, as well as data items to identify
specific choices. The integers (both positive and negative) are used specific choices. The integers (both positive and negative) are used
for compactness of encoding and easy comparison. (Generally, in this for compactness of encoding and easy comparison. (Generally, in this
document the value zero is going to be reserved and not used.) Since document the value zero is going to be reserved and not used.) Since
the work "key" is mainly used in its other meaning, as a the work "key" is mainly used in its other meaning, as a
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One of the issues that needs to be addressed is a requirement that a One of the issues that needs to be addressed is a requirement that a
standard specify a set of algorithms that are required to be standard specify a set of algorithms that are required to be
implemented. [CREF3] This is done to promote interoperability as it implemented. [CREF3] This is done to promote interoperability as it
provides a minimal set of algorithms that all devices can be sure provides a minimal set of algorithms that all devices can be sure
will exist at both ends. However, we have elected not to specify a will exist at both ends. However, we have elected not to specify a
set of mandatory algorithms in this document. set of mandatory algorithms in this document.
It is expected that COSE is going to be used in a wide variety of It is expected that COSE is going to be used in a wide variety of
applications and on a wide variety of devices. Many of the applications and on a wide variety of devices. Many of the
constrained devices are going to be setup to used a small fixed set constrained devices are going to be setup to use a small fixed set of
of algorithms, and this set of algorithms may not match those algorithms, and this set of algorithms may not match those available
available on a device. We therefore have deferred to the application on a device. We therefore have deferred to the application protocols
protocols the decision of what to specify for mandatory algorithms. the decision of what to specify for mandatory algorithms.
Since the set of algorithms in an environment of constrained devices Since the set of algorithms in an environment of constrained devices
may depend on what the set of devices are and how long they have been may depend on what the set of devices are and how long they have been
in operation, we want to highlight that application protocols will in operation, we want to highlight that application protocols will
need to specify some type of discovery method of algorithm need to specify some type of discovery method of algorithm
capabilities. The discovery method may be as simple as requiring capabilities. The discovery method may be as simple as requiring
preconfiguration of the set of algorithms to providing a discovery preconfiguration of the set of algorithms to providing a discovery
method built into the protocol. S/MIME provided a number of method built into the protocol. S/MIME provided a number of
different ways to approach the problem: different ways to approach the problem:
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in operation, we want to highlight that application protocols will in operation, we want to highlight that application protocols will
need to specify some type of discovery method of algorithm need to specify some type of discovery method of algorithm
capabilities. The discovery method may be as simple as requiring capabilities. The discovery method may be as simple as requiring
preconfiguration of the set of algorithms to providing a discovery preconfiguration of the set of algorithms to providing a discovery
method built into the protocol. S/MIME provided a number of method built into the protocol. S/MIME provided a number of
different ways to approach the problem: different ways to approach the problem:
o Advertising in the message (S/MIME capabilities) [RFC5751]. o Advertising in the message (S/MIME capabilities) [RFC5751].
o Advertising in the certificate (capabilities extension) [RFC4262] o Advertising in the certificate (capabilities extension) [RFC4262]
o Minimum requirements for the S/MIME which have been updated over o Minimum requirements for the S/MIME which have been updated over
time [RFC2633][RFC5751] time [RFC2633][RFC5751]
2. The COSE_MSG structure 2. Basic COSE Structure
The COSE_MSG structure is a top level CBOR object that corresponds to
the DataContent type in the Cryptographic Message Syntax (CMS)
[RFC5652]. [CREF4] This structure allows for a top level message to
be sent that could be any of the different security services. The
security service is identified within the message.
The COSE_Tagged_MSG CBOR type takes the COSE_MSG and prepends a CBOR
tag of TBD1 to the encoding of COSE_MSG. By having both a tagged and
untagged version of the COSE_MSG structure, it becomes easy to either
use COSE_MSG as a top level object or embedded in another object.
The tagged version allows for a method of placing the COSE_MSG
structure into a choice, using a consistent tag value to determine
that this is a COSE object.
The existence of the COSE_MSG and COSE_Tagged_MSG CBOR data types are
not intended to prevent protocols from using the individual security
primitives directly. Where only a single service is required, that
structure can be used directly.
Each of the top-level security objects use a CBOR array as the base
structure. For each of the top-level security objects, the first
field is a 'msg_type'. The CBOR type for a 'msg_type' is 'int'. The
'msg_type' is defined to distinguish between the different structures
when they appear as part of a COSE_MSG object. [CREF5] [CREF6]
[CREF7]
The message types defined in this document are:
0 - Reserved.
1 - Signed Message.
2 - Enveloped Message The COSE Message structure is designed so that there can be a large
amount of common code when parsing and processing the different
security messages. All of the message structures are built on a CBOR
array type. The first three elements of the array contains the same
basic information. The first element is a set of protected header
information. The second element is a set of unprotected header
information. The third element is the content of the message (either
as plain text or encrypted). Elements after this point are dependent
on the specific message type.
3 - Authenticated Message (MACed message) Identification of which message is present is done by one of two
methods:
4 - Encrypted Message o The specific message type is known from the context in which it is
placed. This may be defined by a marker in the containing
structure or by restrictions specified by the application
protocol.
Implementations MUST be prepared to find an integer in this field o The message type is identified by a CBOR tag. This document
that does not correspond to the values 1 to 3. If a message type is defines a CBOR tag for each of the message structures.
found then the client does not support the associated security
object, the client MUST stop attempting to process the structure and
fail. The value of 0 is reserved and not assigned to a security
object. If the value of 0 is found, then clients MUST fail
processing the structure. Implementations need to recognize that the
set of values might be extended at a later date, but they should not
provide a security service based on guesses of what the security
object might be.
Text from here to start of next section to be removed Text from here to start of next section to be removed
COSE_MSG = COSE_Sign / COSE_Untagged_Message = COSE_Sign /
COSE_enveloped / COSE_enveloped /
COSE_encryptData / COSE_encryptData /
COSE_mac COSE_Mac
COSE_Tagged_MSG = #6.999(COSE_MSG) ; Replace 999 with TBD1
; msg_type values COSE_Tagged_Message = COSE_Sign_Tagged /
msg_type_reserved=0 COSE_Enveloped_Tagged /
msg_type_signed=1 COSE_EncryptedData_Tagged /
msg_type_enveloped=2 COSE_Mac_Tagged
msg_type_mac=3
msg_type_encryptData=4
3. Header Parameters 3. Header Parameters
The structure of COSE has been designed to have two buckets of The structure of COSE has been designed to have two buckets of
information that are not considered to be part of the payload itself, information that are not considered to be part of the payload itself,
but are used for holding information about content, algorithms, keys, but are used for holding information about content, algorithms, keys,
or evaluation hints for the processing of the layer. These two or evaluation hints for the processing of the layer. These two
buckets are available for use in all of the structures in this buckets are available for use in all of the structures in this
document except for keys. While these buckets can be present, they document except for keys. While these buckets can be present, they
may not all be usable in all instances. For example, while the may not all be usable in all instances. For example, while the
skipping to change at page 9, line 50 skipping to change at page 9, line 21
Both buckets are implemented as CBOR maps. The map key is a 'label' Both buckets are implemented as CBOR maps. The map key is a 'label'
(Section 1.4). The value portion is dependent on the definition for (Section 1.4). The value portion is dependent on the definition for
the label. Both maps use the same set of label/value pairs. The the label. Both maps use the same set of label/value pairs. The
integer and string values for labels has been divided into several integer and string values for labels has been divided into several
sections with a standard range, a private range, and a range that is sections with a standard range, a private range, and a range that is
dependent on the algorithm selected. The defined labels can be found dependent on the algorithm selected. The defined labels can be found
in the 'COSE Header Parameters' IANA registry (Section 15.2). in the 'COSE Header Parameters' IANA registry (Section 15.2).
Two buckets are provided for each layer: Two buckets are provided for each layer:
protected contains parameters about the current layer that are to be protected: Contains parameters about the current layer that are to
cryptographically protected. This bucket MUST be empty if it is be cryptographically protected. This bucket MUST be empty if it
not going to be included in a cryptographic computation. This is not going to be included in a cryptographic computation. This
bucket is encoded in the message as a binary object. This value bucket is encoded in the message as a binary object. This value
is obtained by CBOR encoding the protected map and wrapping it in is obtained by CBOR encoding the protected map and wrapping it in
a bstr object. Senders SHOULD encode an empty protected map as a a bstr object. Senders SHOULD encode an empty protected map as a
zero length binary object (it is shorter). Recipients MUST accept zero length binary object (it is shorter). Recipients MUST accept
both a zero length binary value and a zero length map encoded in both a zero length binary value and a zero length map encoded in
the binary value. The wrapping allows for the encoding of the the binary value. The wrapping allows for the encoding of the
protected map to be transported with a greater chance that it will protected map to be transported with a greater chance that it will
not be altered in transit. (Badly behaved intermediates could not be altered in transit. (Badly behaved intermediates could
decode and re-encode, but this will result in a failure to verify decode and re-encode, but this will result in a failure to verify
unless the re-encoded byte string is identical to the decoded byte unless the re-encoded byte string is identical to the decoded byte
string.) This finesses the problem of all parties needing to be string.) This finesses the problem of all parties needing to be
able to do a common canonical encoding. able to do a common canonical encoding.
unprotected contains parameters about the current layer that are not unprotected: Contains parameters about the current layer that are
cryptographically protected. not cryptographically protected.
Only parameters that deal with the current layer are to be placed at Only parameters that deal with the current layer are to be placed at
that layer. As an example of this, the parameter 'content type' that layer. As an example of this, the parameter 'content type'
describes the content of the message being carried in the message. describes the content of the message being carried in the message.
As such this parameter is placed only the the content layer and is As such this parameter is placed only in the content layer and is not
not placed in the recipient or signature layers. In principle, one placed in the recipient or signature layers. In principle, one
should be able to process any given layer without reference to any should be able to process any given layer without reference to any
other layer. (The only data that should need to cross layers is the other layer. (The only data that should need to cross layers is the
cryptographic key.) cryptographic key.)
The buckets are present in all of the security objects defined in The buckets are present in all of the security objects defined in
this document. The fields in order are the 'protected' bucket (as a this document. The fields in order are the 'protected' bucket (as a
CBOR 'bstr' type) and then the 'unprotected' bucket (as a CBOR 'map' CBOR 'bstr' type) and then the 'unprotected' bucket (as a CBOR 'map'
type). The presence of both buckets is required. The parameters type). The presence of both buckets is required. The parameters
that go into the buckets come from the IANA "COSE Header Parameters" that go into the buckets come from the IANA "COSE Header Parameters"
(Section 15.2). Some common parameters are defined in the next (Section 15.2). Some common parameters are defined in the next
section, but a number of parameters are defined throughout this section, but a number of parameters are defined throughout this
document. document.
Text from here to start of next section to be removed [CREF8] Text from here to start of next section to be removed [CREF4]
header_map = {+ label => any } header_map = {+ label => any }
Headers = ( Headers = (
protected : bstr, ; Contains a header_map protected : bstr, ; Contains a header_map
unprotected : header_map unprotected : header_map
) )
3.1. Common COSE Headers Parameters 3.1. Common COSE Headers Parameters
skipping to change at page 13, line 5 skipping to change at page 11, line 44
counter signature This parameter holds a counter signature value. counter signature This parameter holds a counter signature value.
Counter signatures provide a method of having a second party sign Counter signatures provide a method of having a second party sign
some data, the counter signature can occur as an unprotected some data, the counter signature can occur as an unprotected
attribute in any of the following structures: COSE_Sign, attribute in any of the following structures: COSE_Sign,
COSE_signature, COSE_enveloped, COSE_recipient, COSE_signature, COSE_enveloped, COSE_recipient,
COSE_encryptedData, COSE_mac. These structures all have the same COSE_encryptedData, COSE_mac. These structures all have the same
basic structure so that a consistent calculation of the counter basic structure so that a consistent calculation of the counter
signature can be computed. Details on computing counter signature can be computed. Details on computing counter
signatures are found in Section 4.3. signatures are found in Section 4.3.
creation time This parameter provides the time the content was
created. For signatures and recipient structures, this would be
the time that the signature or recipient key object was created.
For content structures, this would be the time that the content
was created. The unsigned integer value is the number of seconds,
excluding leap seconds; after midnight UTC, January 1, 1970.
sequence number This parameter provides a counter field. The use of
this parameter is application specific.
+----------+-------+---------------+----------------+---------------+ +----------+-------+---------------+----------------+---------------+
| name | label | value type | value registry | description | | name | label | value type | value registry | description |
+----------+-------+---------------+----------------+---------------+ +----------+-------+---------------+----------------+---------------+
| alg | 1 | int / tstr | COSE Algorithm | Integers are | | alg | 1 | int / tstr | COSE Algorithm | Integers are |
| | | | Registry | taken from | | | | | Registry | taken from |
| | | | | table --POINT | | | | | | table --POINT |
| | | | | TO REGISTRY-- | | | | | | TO REGISTRY-- |
| | | | | | | | | | | |
| crit | 2 | [+ label] | COSE Header | integer | | crit | 2 | [+ label] | COSE Header | integer |
| | | | Label Registry | values are | | | | | Label Registry | values are |
skipping to change at page 13, line 39 skipping to change at page 12, line 39
| | | | | identifier | | | | | | identifier |
| | | | | | | | | | | |
| nonce | 5 | bstr | | Nonce or Init | | nonce | 5 | bstr | | Nonce or Init |
| | | | | ialization | | | | | | ialization |
| | | | | Vector (IV) | | | | | | Vector (IV) |
| | | | | | | | | | | |
| counter | 6 | COSE_signatur | | CBOR encoded | | counter | 6 | COSE_signatur | | CBOR encoded |
| signatur | | e | | signature | | signatur | | e | | signature |
| e | | | | structure | | e | | | | structure |
| | | | | | | | | | | |
| zip | * | int / tstr | | Integers are | | creation | * | uint | | Time the |
| | | | | taken from | | time | | | | content was |
| | | | | the table | | | | | | created |
| | | | | --POINT TO | | | | | | |
| | | | | REGISTRY-- | | sequence | * | uint | | Application |
| number | | | | specific |
| | | | | Integer value |
+----------+-------+---------------+----------------+---------------+ +----------+-------+---------------+----------------+---------------+
Table 1: Common Header Parameters Table 1: Common Header Parameters
OPEN ISSUES: OPEN ISSUES:
1. Do we want to have a zip/compression header standardized in this 1. I am currently torn on the question "Should epk and iv/nonce be
document?
2. I am currently torn on the question "Should epk and iv/nonce be
algorithm specific or generic headers?" They are really specific algorithm specific or generic headers?" They are really specific
to an algorithm and can potentially be defined in different ways to an algorithm and can potentially be defined in different ways
for different algorithms. As an example, it would make sense to for different algorithms. As an example, it would make sense to
defined nonce for CCM and GCM modes that can have the leading defined nonce for CCM and GCM modes that can have the leading
zero bytes stripped, while for other algorithms this might be zero bytes stripped, while for other algorithms this might be
undesirable. undesirable.
3. We might want to define some additional items. What are they? A 2. We might want to define some additional items. What are they? A
possible example would be a sequence number as this might be possible example would be a sequence number as this might be
common. On the other hand, this is the type of things that is common. On the other hand, this is the type of things that is
frequently used as the nonce in some places and thus should not frequently used as the nonce in some places and thus should not
be used in the same way. Other items might be challenge/response be used in the same way. Other items might be challenge/response
fields for freshness as these are likely to be common. fields for freshness as these are likely to be common.
4. Signing Structure 4. Signing Structure
The signature structure allows for one or more signatures to be The signature structure allows for one or more signatures to be
applied to a message payload. There are provisions for parameters applied to a message payload. There are provisions for parameters
about the content and parameters about the signature to be carried about the content and parameters about the signature to be carried
along with the signature itself. These parameters may be along with the signature itself. These parameters may be
authenticated by the signature, or just present. Examples of authenticated by the signature, or just present. Examples of
parameters about the content would be the type of content, when the parameters about the content would be the type of content, when the
content was created, and who created the content. Examples of content was created, and who created the content. [CREF5] Examples
parameters about the signature would be the algorithm and key used to of parameters about the signature would be the algorithm and key used
create the signature, when the signature was created, and counter- to create the signature, when the signature was created, and counter-
signatures. signatures.
When more than one signature is present, the successful validation of When more than one signature is present, the successful validation of
one signature associated with a given signer is usually treated as a one signature associated with a given signer is usually treated as a
successful signature by that signer. However, there are some successful signature by that signer. However, there are some
application environments where other rules are needed. An application environments where other rules are needed. An
application that employs a rule other than one valid signature for application that employs a rule other than one valid signature for
each signer must specify those rules. Also, where simple matching of each signer must specify those rules. Also, where simple matching of
the signer identifier is not sufficient to determine whether the the signer identifier is not sufficient to determine whether the
signatures were generated by the same signer, the application signatures were generated by the same signer, the application
skipping to change at page 15, line 8 skipping to change at page 14, line 8
include signatures generated with the RSA signature algorithm and include signatures generated with the RSA signature algorithm and
with the Elliptic Curve Digital Signature Algorithm (ECDSA) signature with the Elliptic Curve Digital Signature Algorithm (ECDSA) signature
algorithm. This allows recipients to verify the signature associated algorithm. This allows recipients to verify the signature associated
with one algorithm or the other. (The original source of this text with one algorithm or the other. (The original source of this text
is [RFC5652].) More detailed information on multiple signature is [RFC5652].) More detailed information on multiple signature
evaluation can be found in [RFC5752]. evaluation can be found in [RFC5752].
The COSE_Sign structure is a CBOR array. The fields of the array in The COSE_Sign structure is a CBOR array. The fields of the array in
order are: order are:
msg_type identifies this as providing the signed security service.
The value MUST be msg_type_signed (1).
protected is described in Section 3. protected is described in Section 3.
unprotected is described in Section 3. unprotected is described in Section 3.
payload contains the serialized content to be signed. If the payload contains the serialized content to be signed. If the
payload is not present in the message, the application is required payload is not present in the message, the application is required
to supply the payload separately. The payload is wrapped in a to supply the payload separately. The payload is wrapped in a
bstr to ensure that it is transported without changes. If the bstr to ensure that it is transported without changes. If the
payload is transported separately, then a nil CBOR object is payload is transported separately, then a nil CBOR object is
placed in this location and it is the responsibility of the placed in this location and it is the responsibility of the
skipping to change at page 15, line 38 skipping to change at page 14, line 35
protected is described in Section 3. protected is described in Section 3.
unprotected is described in Section 3. unprotected is described in Section 3.
signature contains the computed signature value. The type of the signature contains the computed signature value. The type of the
field is a bstr. field is a bstr.
Text from here to start of next section to be removed Text from here to start of next section to be removed
COSE_Sign_Tagged = #6.999(COSE_Sign) ; Replace 999 with TBD1
COSE_Sign = [ COSE_Sign = [
msg_type: msg_type_signed,
Headers, Headers,
payload : bstr / nil, payload : bstr / nil,
signatures : [+ COSE_signature] signatures : [+ COSE_signature]
] ]
COSE_signature = [ COSE_signature = [
Headers, Headers,
signature : bstr signature : bstr
] ]
4.1. Externally Supplied Data 4.1. Externally Supplied Data
One of the features that we supply in the COSE document is the One of the features that we supply in the COSE document is the
ability for applications to provide additional data to be ability for applications to provide additional data to be
authenticated as part of the security, but that is not carried as authenticated as part of the security, but that is not carried as
part of the COSE object. The primary reason for supporting this can part of the COSE object. The primary reason for supporting this can
be seen by looking at the CoAP message struture [RFC7252] where the be seen by looking at the CoAP message structure [RFC7252] where the
facility exists for options to be carried before the payload. An facility exists for options to be carried before the payload. An
example of data that can be placed in this location would be example of data that can be placed in this location would be
transaction ids and nonces to check for replay protection. If the transaction ids and nonces to check for replay protection. If the
data is in the options section, then it is available for routers to data is in the options section, then it is available for routers to
help in performing the replay detection and prevention. However, it help in performing the replay detection and prevention. However, it
may also be desired to protect these values so that they cannot be may also be desired to protect these values so that they cannot be
modified in transit. This is the purpose of the externally supplied modified in transit. This is the purpose of the externally supplied
data field. data field.
This document describes the process for using a byte array of This document describes the process for using a byte array of
skipping to change at page 17, line 16 skipping to change at page 16, line 16
containing the protected attributes external to the containing the protected attributes external to the
COSE_Signature structure. COSE_Signature structure.
4. The payload to be signed. The payload is encoded in a bstr. The 4. The payload to be signed. The payload is encoded in a bstr. The
payload is placed here independent of how it is transported. payload is placed here independent of how it is transported.
How to compute a signature: How to compute a signature:
1. Create a CBOR array and populate it with the appropriate fields. 1. Create a CBOR array and populate it with the appropriate fields.
For body_protected and sign_protected, if the fields are not For body_protected and sign_protected, if the fields are not
present in their corresponding maps, an bstr of length zero is present in their corresponding maps, a bstr of length zero is
used. used.
2. If the application has supplied external additional authenticated 2. If the application has supplied external additional authenticated
data to be included in the computation, then it is placed in the data to be included in the computation, then it is placed in the
third field. If no data was supplied, then a zero length binary third field. If no data was supplied, then a zero length binary
value is used. value is used.
3. Create the value ToBeSigned by encoding the Sig_structure to a 3. Create the value ToBeSigned by encoding the Sig_structure to a
byte string. byte string.
skipping to change at page 17, line 38 skipping to change at page 16, line 38
sign with), alg (the algorithm to sign with) and ToBeSigned (the sign with), alg (the algorithm to sign with) and ToBeSigned (the
value to sign). value to sign).
5. Place the resulting signature value in the 'signature' field of 5. Place the resulting signature value in the 'signature' field of
the map. the map.
How to verify a signature: How to verify a signature:
1. Create a Sig_structure object and populate it with the 1. Create a Sig_structure object and populate it with the
appropriate fields. For body_protected and sign_protected, if appropriate fields. For body_protected and sign_protected, if
the fields are not present in their corresponding maps, an bstr the fields are not present in their corresponding maps, a bstr of
of length zero is used. length zero is used.
2. If the application has supplied external additional authenticated 2. If the application has supplied external additional authenticated
data to be included in the computation, then it is placed in the data to be included in the computation, then it is placed in the
third field. If no data was supplied, then a zero length binary third field. If no data was supplied, then a zero length binary
value is used. value is used.
3. Create the value ToBeSigned by encoding the Sig_structure to a 3. Create the value ToBeSigned by encoding the Sig_structure to a
byte string. byte string.
4. Call the signature verification algorithm passing in K (the key 4. Call the signature verification algorithm passing in K (the key
skipping to change at page 18, line 29 skipping to change at page 17, line 29
payload: bstr payload: bstr
] ]
4.3. Computing Counter Signatures 4.3. Computing Counter Signatures
Counter signatures provide a method of having a different signature Counter signatures provide a method of having a different signature
occur on some piece of content. This is normally used to provide a occur on some piece of content. This is normally used to provide a
signature on a signature allowing for a proof that a signature signature on a signature allowing for a proof that a signature
existed at a given time. In this document we allow for counter existed at a given time. In this document we allow for counter
signatures to exist in a greater number of environments. A counter signatures to exist in a greater number of environments. A counter
signature can exist, for example, on a COSE_encyptedData object and signature can exist, for example, on a COSE_encryptedData object and
allow for a signature to be present on the encrypted content of a allow for a signature to be present on the encrypted content of a
message. message.
The creation and validation of counter signatures over the different The creation and validation of counter signatures over the different
items relies on the fact that the structure all of our objects have items relies on the fact that the structure all of our objects have
the same structure. The first element may be a message type, this is the same structure. The first element may be a message type, this is
followed by a set of protected attributes, a set of unprotected followed by a set of protected attributes, a set of unprotected
attributes and a body in that order. This means that the attributes and a body in that order. This means that the
Sig_structure can be used for in a uniform manner to get the byte Sig_structure can be used for in a uniform manner to get the byte
stream for processing a signature. If the counter signature is going stream for processing a signature. If the counter signature is going
skipping to change at page 19, line 8 skipping to change at page 18, line 8
While one can create a counter signature for a COSE_Sign structure, While one can create a counter signature for a COSE_Sign structure,
there is not much of a point to doing so. It is equivalent to create there is not much of a point to doing so. It is equivalent to create
a new COSE_signature structure and placing it in the signatures a new COSE_signature structure and placing it in the signatures
array. It is strongly suggested that it not be done, but it is not array. It is strongly suggested that it not be done, but it is not
banned. banned.
5. Encryption objects 5. Encryption objects
COSE supports two different encryption structures. OOSE_enveloped is COSE supports two different encryption structures. OOSE_enveloped is
used when the key needs to be explicilty identified. This structure used when the key needs to be explicitly identified. This structure
supports the use of recipient structures to allow for random content supports the use of recipient structures to allow for random content
encryption keys to be used.. COSE_encrypted is used when the a encryption keys to be used. COSE_encrypted is used when a recipient
recipient structure is not needed because the key to be used is known structure is not needed because the key to be used is known
implicitly. implicitly.
5.1. Enveloped COSE structure 5.1. Enveloped COSE structure
The enveloped structure allows for one or more recipients of a The enveloped structure allows for one or more recipients of a
message. There are provisions for parameters about the content and message. There are provisions for parameters about the content and
parameters about the recipient information to be carried in the parameters about the recipient information to be carried in the
message. The parameters associated with the content can be message. The parameters associated with the content can be
authenticated by the content encryption algorithm. The parameters authenticated by the content encryption algorithm. The parameters
associated with the recipient can be authenticated by the recipient associated with the recipient can be authenticated by the recipient
algorithm (when the algorithm supports it). Examples of parameters algorithm (when the algorithm supports it). Examples of parameters
about the content are the type of the content, when the content was about the content are the type of the content, when the content was
created, and the content encryption algorithm. Examples of created, and the content encryption algorithm. Examples of
parameters about the recipient are the recipients key identifier, the parameters about the recipient are the recipient's key identifier,
recipient encryption algorithm. the recipient encryption algorithm.
In COSE, the same techniques and structures for encrypting both the In COSE, the same techniques and structures for encrypting both the
plain text and the keys used to protect the text. This is different plain text and the keys used to protect the text. This is different
from the approach used by both [RFC5652] and [RFC7516] where from the approach used by both [RFC5652] and [RFC7516] where
different structures are used for the content layer and for the different structures are used for the content layer and for the
recipient layer. recipient layer.
The COSE_encrypt structure is a CBOR array. The fields of the array The COSE_encrypt structure is a CBOR array. The fields of the array
in order are: in order are:
msg_type identifies this as providing the encrypted security
service. The value MUST be msg_type_encrypted (2).
protected is described in Section 3. protected is described in Section 3.
unprotected is described in Section 3. unprotected is described in Section 3.
ciphertext contains the encrypted plain text encoded as a bstr. If ciphertext contains the encrypted plain text encoded as a bstr. If
the ciphertext is to be transported independently of the control the ciphertext is to be transported independently of the control
information about the encryption process (i.e. detached content) information about the encryption process (i.e. detached content)
then the field is encoded as a null object. then the field is encoded as a null object.
recipients contains an array of recipient information structures. recipients contains an array of recipient information structures.
skipping to change at page 20, line 22 skipping to change at page 19, line 19
ciphertext contains the encrypted key encoded as a bstr. If there ciphertext contains the encrypted key encoded as a bstr. If there
is not an encrypted key, then this field is encoded as a nil type. is not an encrypted key, then this field is encoded as a nil type.
recipients contains an array of recipient information structures. recipients contains an array of recipient information structures.
The type for the recipient information structure is a The type for the recipient information structure is a
COSE_recipient. If there are no recipient information structures, COSE_recipient. If there are no recipient information structures,
this element is absent. this element is absent.
Text from here to start of next section to be removed Text from here to start of next section to be removed
COSE_enveloped = [ COSE_Enveloped_Tagged = #6.998(COSE_enveloped) ; Replace 998 with TBD32
msg_type: msg_type_enveloped,
COSE_encrypt_fields
recipients: [+COSE_recipient]
]
COSE_encrypt_fields = ( COSE_enveloped = [
Headers, COSE_encrypt_fields
ciphertext: bstr / nil, recipients: [+COSE_recipient]
) ]
COSE_recipient = [ COSE_encrypt_fields = (
COSE_encrypt_fields Headers,
? recipients: [+COSE_recipient] ciphertext: bstr / nil,
] )
COSE_recipient = [
COSE_encrypt_fields
? recipients: [+COSE_recipient]
]
5.1.1. Recipient Algorithm Classes 5.1.1. Recipient Algorithm Classes
A typical encrypted message consists of an encrypted content and an A typical encrypted message consists of an encrypted content and an
encrypted CEK for one or more recipients. The content-encryption key encrypted CEK for one or more recipients. The content-encryption key
is encrypted for each recipient, using a key specific to that is encrypted for each recipient, using a key specific to that
recipient. The details of this encryption depends on which class the recipient. The details of this encryption depends on which class the
recipient algorithm falls into. Specific details on each of the recipient algorithm falls into. Specific details on each of the
classes can be found in Section 12. A short summary of the six classes can be found in Section 12. A short summary of the six
recipient algorithm classes is: recipient algorithm classes is:
none: The CEK is the same as as the identified previously none: The CEK is the same as the identified previously distributed
distributed symmetric key or derived from a previously distributed symmetric key or derived from a previously distributed secret.
secret.
symmetric key-encryption keys: The CEK is encrypted using a symmetric key-encryption keys: The CEK is encrypted using a
previously distributed symmetric key-encryption key. previously distributed symmetric key-encryption key.
key agreement: the recipient's public key and a sender's private key key agreement: the recipient's public key and a sender's private key
are used to generate a pairwise secret, a KDF is applied to derive are used to generate a pairwise secret, a KDF is applied to derive
a key, and then the CEK is either the derived key or encrypted by a key, and then the CEK is either the derived key or encrypted by
the derived key. the derived key.
key transport: the CEK is encrypted in the recipient's public key key transport: the CEK is encrypted in the recipient's public key
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5.2. Encrypted COSE structure 5.2. Encrypted COSE structure
The encrypted structure does not have the ability to specify The encrypted structure does not have the ability to specify
recipients of the message. The structure assumes that the recipient recipients of the message. The structure assumes that the recipient
of the object will already know the identity of the key to be used in of the object will already know the identity of the key to be used in
order to decrypt the message. If a key needs to be identified to the order to decrypt the message. If a key needs to be identified to the
recipient, the enveloped structure is used. recipient, the enveloped structure is used.
The CDDL grammar structure for encrypted data is: The CDDL grammar structure for encrypted data is:
COSE_encryptData = [ COSE_EncryptedData_Tagged = #6.997(COSE_encryptData) ; Replace 997 with TBD3
msg_type: msg_type_encryptData,
COSE_encrypt_fields COSE_encryptData = [
] COSE_encrypt_fields
]
The COSE_encryptedData structure is a CBOR array. The fields of the The COSE_encryptedData structure is a CBOR array. The fields of the
array in order are: array in order are:
msg_type identifies this as providing the encrypted data security
service. This value MUST be mg_type_encrypted (4).
protected is described in Section 3. protected is described in Section 3.
unprotected is described in Section 3. unprotected is described in Section 3.
ciphertext contains the encrypted plain text. If the ciphertext is ciphertext contains the encrypted plain text. If the ciphertext is
to be transported independently of the control information about to be transported independently of the control information about
the encryption process (i.e. detached content) then the field is the encryption process (i.e. detached content) then the field is
encoded as a null object. encoded as a null object.
5.3. Encryption Algorithm for AEAD algorithms 5.3. Encryption Algorithm for AEAD algorithms
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can be used for this purpose. The second mode is to both check that can be used for this purpose. The second mode is to both check that
the content has not been changed since the MAC was computed, and to the content has not been changed since the MAC was computed, and to
use recipient algorithm to verify who sent it. The classes of use recipient algorithm to verify who sent it. The classes of
recipient algorithms that support this are those that use a pre- recipient algorithms that support this are those that use a pre-
shared secret or do static-static key agreement (without the key wrap shared secret or do static-static key agreement (without the key wrap
step). In both of these cases the entity MACing the message can be step). In both of these cases the entity MACing the message can be
validated by a key binding. (The binding of identity assumes that validated by a key binding. (The binding of identity assumes that
there are only two parties involved and you did not send the message there are only two parties involved and you did not send the message
yourself.) yourself.)
The COSE_encrypt structure is a CBOR array. The fields of the array The COSE_Mac structure is a CBOR array. The fields of the array in
in order are: order are:
msg_type identifies this as providing the encrypted security
service. The value MUST be msg_type_mac (3).
protected is described in Section 3. protected is described in Section 3.
unprotected is described in Section 3. unprotected is described in Section 3.
payload contains the serialized content to be MACed. If the payload payload contains the serialized content to be MACed. If the payload
is not present in the message, the application is required to is not present in the message, the application is required to
supply the payload separately. The payload is wrapped in a bstr supply the payload separately. The payload is wrapped in a bstr
to ensure that it is transported without changes. If the payload to ensure that it is transported without changes. If the payload
is transported separately, then a null CBOR object is placed in is transported separately, then a null CBOR object is placed in
this location and it is the responsibility of the application to this location and it is the responsibility of the application to
ensure that it will be transported without changes. ensure that it will be transported without changes.
tag contains the MAC value. tag contains the MAC value.
recipients contains the recipient information. See the description recipients contains the recipient information. See the description
under COSE_Encryption for more info. under COSE_Encryption for more info.
Text from here to start of next section to be removed Text from here to start of next section to be removed
COSE_mac = [ COSE_Mac_Tagged = #6.996(COSE_Mac) ; Replace 996 with TBD4
msg_type: msg_type_mac,
Headers, COSE_Mac = [
payload: bstr / nil, Headers,
tag: bstr, payload: bstr / nil,
recipients: [+COSE_recipient] tag: bstr,
] recipients: [+COSE_recipient]
]
6.1. How to compute a MAC 6.1. How to compute a MAC
How to compute a MAC: How to compute a MAC:
1. Create a MAC_structure and copy the protected and payload fields 1. Create a MAC_structure and copy the protected and payload fields
from the COSE_mac structure. from the COSE_Mac structure.
2. If the application has supplied external authenticated data, 2. If the application has supplied external authenticated data,
encode it as a binary value and place in the MAC_structure. If encode it as a binary value and place in the MAC_structure. If
there is no external authenticated data, then use a zero length there is no external authenticated data, then use a zero length
'bstr'. (See Section 4.1 for application guidance on 'bstr'. (See Section 4.1 for application guidance on
constructing this field.) constructing this field.)
3. Encode the MAC_structure using a canonical CBOR encoder. The 3. Encode the MAC_structure using a canonical CBOR encoder. The
resulting bytes is the value to compute the MAC on. resulting bytes is the value to compute the MAC on.
4. Compute the MAC and place the result in the 'tag' field of the 4. Compute the MAC and place the result in the 'tag' field of the
COSE_mac structure. COSE_Mac structure.
5. Encrypt and encode the MAC key for each recipient of the message. 5. Encrypt and encode the MAC key for each recipient of the message.
Text from here to start of next section to be removed Text from here to start of next section to be removed
MAC_structure = [ MAC_structure = [
protected: bstr, protected: bstr,
external_aad: bstr, external_aad: bstr,
payload: bstr payload: bstr
] ]
7. Key Structure 7. Key Structure
A COSE Key structure is built on a CBOR map object. The set of A COSE Key structure is built on a CBOR map object. The set of
common parameters that can appear in a COSE Key can be found in the common parameters that can appear in a COSE Key can be found in the
skipping to change at page 25, line 21 skipping to change at page 24, line 18
] ]
7. Key Structure 7. Key Structure
A COSE Key structure is built on a CBOR map object. The set of A COSE Key structure is built on a CBOR map object. The set of
common parameters that can appear in a COSE Key can be found in the common parameters that can appear in a COSE Key can be found in the
IANA registry 'COSE Key Common Parameter Registry' (Section 15.5). IANA registry 'COSE Key Common Parameter Registry' (Section 15.5).
Additional parameters defined for specific key types can be found in Additional parameters defined for specific key types can be found in
the IANA registry 'COSE Key Type Parameters' (Section 15.6). the IANA registry 'COSE Key Type Parameters' (Section 15.6).
A COSE Key Set uses a CBOR array object as it's underlying type. The A COSE Key Set uses a CBOR array object as its underlying type. The
values of the array elements are COSE Keys. A Key Set MUST have at values of the array elements are COSE Keys. A Key Set MUST have at
least one element in the array. [CREF9] least one element in the array.
The element "kty" is a required element in a COSE_Key map. The element "kty" is a required element in a COSE_Key map.
Text from here to start of next section to be removed Text from here to start of next section to be removed
The CDDL grammar describing a COSE_Key and COSE_KeySet is: [CREF10] The CDDL grammar describing a COSE_Key and COSE_KeySet is: [CREF6]
COSE_Key = { COSE_Key = {
key_kty => tstr / int, key_kty => tstr / int,
? key_ops => [+ (tstr / int) ], ? key_ops => [+ (tstr / int) ],
? key_alg => tstr / int, ? key_alg => tstr / int,
? key_kid => bstr, ? key_kid => bstr,
* label => values * label => values
} }
COSE_KeySet = [+COSE_Key] COSE_KeySet = [+COSE_Key]
skipping to change at page 26, line 32 skipping to change at page 25, line 32
| | | | | kid in message | | | | | | kid in message |
| | | | | | | | | | | |
| use | * | tstr | | deprecated - don't | | use | * | tstr | | deprecated - don't |
| | | | | use | | | | | | use |
+---------+-------+-------------+-------------+---------------------+ +---------+-------+-------------+-------------+---------------------+
Table 2: Key Map Labels Table 2: Key Map Labels
kty: This parameter is used to identify the family of keys for this kty: This parameter is used to identify the family of keys for this
structure, and thus the set of key type specific parameters to be structure, and thus the set of key type specific parameters to be
found. The set of values can be found in Table 20. This found. The set of values can be found in Table 18. This
parameter MUST be present in a key object. Implementations MUST parameter MUST be present in a key object. Implementations MUST
verify that the key type is appropriate for the algorithm being verify that the key type is appropriate for the algorithm being
processed. The key type MUST be included as part of a trust processed. The key type MUST be included as part of a trust
decision process. decision process.
alg: This parameter is used to restrict the algorithms that are to alg: This parameter is used to restrict the algorithms that are to
be used with this key. If this parameter is present in the key be used with this key. If this parameter is present in the key
structure, the application MUST verify that this algorithm matches structure, the application MUST verify that this algorithm matches
the algorithm for which the key is being used. If the algorthms the algorithm for which the key is being used. If the algorithms
do not match, then this key object MUST NOT be used to perform the do not match, then this key object MUST NOT be used to perform the
cryptographic operation. Note that the same key can be in a cryptographic operation. Note that the same key can be in a
different key structure with a different or no algorithm different key structure with a different or no algorithm
specified, however this is considered to be a poor security specified, however this is considered to be a poor security
practice. practice.
kid: This parameter is used to give an identifier for a key. The kid: This parameter is used to give an identifier for a key. The
identifier is not structured and can be anything from a user identifier is not structured and can be anything from a user
provided string to a value computed on the public portion of the provided string to a value computed on the public portion of the
key. This field is intended for matching against a 'kid' key. This field is intended for matching against a 'kid'
skipping to change at page 28, line 40 skipping to change at page 27, line 40
signature = Sign(message content, key) signature = Sign(message content, key)
valid = Verification(message content, key, signature) valid = Verification(message content, key, signature)
The second is a signature with message recovery. (An example of such The second is a signature with message recovery. (An example of such
an algorithm is [PVSig].) In this structure, the message content is an algorithm is [PVSig].) In this structure, the message content is
processed, but part of is included in the signature. Moving bytes of processed, but part of is included in the signature. Moving bytes of
the message content into the signature allows for an effectively the message content into the signature allows for an effectively
smaller signature, the signature size is still potentially large, but smaller signature, the signature size is still potentially large, but
the message content is shrunk. This has implications for systems the message content is shrunk. This has implications for systems
implementing these algoritms and for applications that use them. The implementing these algorithms and for applications that use them.
first is that the message content is not fully available until after The first is that the message content is not fully available until
a signature has been validated. Until that point the part of the after a signature has been validated. Until that point the part of
message contained inside of the signature is unrecoverable. The the message contained inside of the signature is unrecoverable. The
second is that the security analysis of the strength of the signature second is that the security analysis of the strength of the signature
is very much based on the structure of the message content. Messages is very much based on the structure of the message content. Messages
which are highly predictable require additional randomness to be which are highly predictable require additional randomness to be
supplied as part of the signature process, in the worst case it supplied as part of the signature process, in the worst case it
becomes the same as doing a signature with appendix. Thirdly, in the becomes the same as doing a signature with appendix. Thirdly, in the
event that multple signatures are applied to a message, all of the event that multiple signatures are applied to a message, all of the
signature algorithms are going to be required to consume the same signature algorithms are going to be required to consume the same
number of bytes of message content. number of bytes of message content.
signature, message sent = Sign(message content, key) signature, message sent = Sign(message content, key)
valid, message content = Verification(message sent, key, signature) valid, message content = Verification(message sent, key, signature)
At this time, only signatures with appendixes are defined for use At this time, only signatures with appendixes are defined for use
with COSE, however considerable interest has been expressed in using with COSE, however considerable interest has been expressed in using
a signature with message recovery algorithm due to the effective size a signature with message recovery algorithm due to the effective size
skipping to change at page 30, line 34 skipping to change at page 29, line 34
and the security strength of the hash function. and the security strength of the hash function.
System which have poor random number generation can leak their keys System which have poor random number generation can leak their keys
by signing two different messages with the same value of 'k'. by signing two different messages with the same value of 'k'.
[RFC6979] provides a method to deal with this problem by making 'k' [RFC6979] provides a method to deal with this problem by making 'k'
be deterministic based on the message content rather than randomly be deterministic based on the message content rather than randomly
generated. Applications which specify ECDSA should evaluate the generated. Applications which specify ECDSA should evaluate the
ability to get good random number generation and require this when it ability to get good random number generation and require this when it
is not possible. Note: Use of this technique a good idea even when is not possible. Note: Use of this technique a good idea even when
good random number generation exists. Doing so both reduces the good random number generation exists. Doing so both reduces the
possiblity of having the same value of 'k' in two signature possibility of having the same value of 'k' in two signature
operations, but allows for reproducable signature values which helps operations, but allows for reproducible signature values which helps
testing. testing.
There are two substitution that can theoretically be mounted against There are two substitution that can theoretically be mounted against
the ECDSA signature algorithm. the ECDSA signature algorithm.
o Changing the curve used to validate the signature: If one changes o Changing the curve used to validate the signature: If one changes
the curve used to validate the signature, then potentially one the curve used to validate the signature, then potentially one
could have a two messages with the same signature each computed could have a two messages with the same signature each computed
under a different curve. The only requirement on the new curve is under a different curve. The only requirement on the new curve is
that it's order be the same as the old one and it be acceptable to that its order be the same as the old one and it be acceptable to
the client. An example would be to change from using the curve the client. An example would be to change from using the curve
secp256r1 (aka P-256) to using secp256k1. (Both are 256 bit secp256r1 (aka P-256) to using secp256k1. (Both are 256 bit
curves.) We current do not have any way to deal with this version curves.) We current do not have any way to deal with this version
of the attack except to restrict the overall set of curves that of the attack except to restrict the overall set of curves that
can be used. can be used.
o Change the hash function used to validate the signature: If one o Change the hash function used to validate the signature: If one
has either two different hash functions of the same length, or one has either two different hash functions of the same length, or one
can truncate a hash function down, then one could potentially find can truncate a hash function down, then one could potentially find
collisions between the hash functions rather than within a single collisions between the hash functions rather than within a single
hash function. (For example, truncating SHA-512 to 256 bits might hash function. (For example, truncating SHA-512 to 256 bits might
collide with a SHA-256 bit hash value.) This attack can be collide with a SHA-256 bit hash value.) This attack can be
mitigated by including the signature algorithm identifier in the mitigated by including the signature algorithm identifier in the
data to be signed. data to be signed.
8.2. RSASSA-PSS
The RSASSA-PSS signature algorithm is defined in [RFC3447].
The RSASSA-PSS signature algorithm is parametized with a hash
function (h), a mask generation function (mgf) and a salt length
(sLen). For this specification, the mask generation function is
fixed to be MGF1 as defined in [RFC3447]. It has been recommended
that the same hash function be used for hashing the data as well as
in the mask generation function, for this specification we following
this recommendation. The salt length is the same length as the hash
function output.
Implementations need to check that the key type is 'RSA' when
creating or verifying a signature.
The algorithms defined in this document can be found in Table 5.
+-------+-------+---------+-------------+-----------------------+
| name | value | hash | salt length | description |
+-------+-------+---------+-------------+-----------------------+
| PS256 | -26 | SHA-256 | 32 | RSASSA-PSS w/ SHA-256 |
| | | | | |
| PS384 | -27 | SHA-384 | 48 | RSASSA-PSS w/ SHA-384 |
| | | | | |
| PS512 | -28 | SHA-512 | 64 | RSASSA-PSS w/ SHA-512 |
+-------+-------+---------+-------------+-----------------------+
Table 5: RSASSA-PSS Algorithm Values
8.2.1. Security Considerations
In addition to needing to worry about keys that are too small to
provide the required security, there are issues with keys that are
too large. Denial of service attacks have been mounted with overly
large keys. This has the potential to consume resources with
potentially bad keys. There are two reasonable ways to address this
attack. First, a key should not be used for a cryptographic
operation until it has been matched back to an authorized user. This
approach means that no cryptography would be done except for
authorized users. Second, applications can impose maximum as well as
minimum length requirements on keys. This limits the resources
consumed even if the matching is not performed until the cryptography
has been done.
There is a theoretical hash substitution attack that can be mounted
against RSASSA-PSS. However, the requirement that the same hash
function be used consistently for all operations is an effective
mitigation against it. Unlike ECDSA, hash functions are not
truncated so that the full hash value is always signed. The internal
padding structure of RSASSA-PSS means that one needs to have multiple
collisions between the two hash functions in order to be successful
in producing a forgery based on changing the hash function. This is
highly unlikely.
9. Message Authentication (MAC) Algorithms 9. Message Authentication (MAC) Algorithms
Message Authentication Codes (MACs) provide data authentication and Message Authentication Codes (MACs) provide data authentication and
integrity protection. They provide either no or very limited data integrity protection. They provide either no or very limited data
origination. (One cannot, for example, be used to prove the identity origination. (One cannot, for example, be used to prove the identity
of the sender to a third party.) of the sender to a third party.)
MACs are designed in the same basic structure as signature with MACs are designed in the same basic structure as signature with
appendix algorithms. The message content is processed and an appendix algorithms. The message content is processed and an
authentication code is produced, the authentication code is authentication code is produced, the authentication code is
skipping to change at page 33, line 11 skipping to change at page 31, line 4
security of hash algorithms such as MD5 has decreased over time, the security of hash algorithms such as MD5 has decreased over time, the
security of HMAC combined with MD5 has not yet been shown to be security of HMAC combined with MD5 has not yet been shown to be
compromised [RFC6151]. compromised [RFC6151].
The HMAC algorithm is parameterized by an inner and outer padding, a The HMAC algorithm is parameterized by an inner and outer padding, a
hash function (h) and an authentication tag value length. For this hash function (h) and an authentication tag value length. For this
specification, the inner and outer padding are fixed to the values specification, the inner and outer padding are fixed to the values
set in [RFC2104]. The length of the authentication tag corresponds set in [RFC2104]. The length of the authentication tag corresponds
to the difficulty of producing a forgery. For use in constrained to the difficulty of producing a forgery. For use in constrained
environments, we define a set of HMAC algorithms that are truncated. environments, we define a set of HMAC algorithms that are truncated.
There are currently no known issues when truncating, however the There are currently no known issues when truncating, however the
security strength of the message tag is correspondingly reduced in security strength of the message tag is correspondingly reduced in
strength. When truncating, the left most tag length bits are kept strength. When truncating, the left most tag length bits are kept
and transmitted. and transmitted.
The algorithm defined in this document can be found in Table 6. The algorithm defined in this document can be found in Table 5.
+-----------+-------+---------+--------+----------------------------+ +-----------+-------+---------+--------+----------------------------+
| name | value | Hash | Length | description | | name | value | Hash | Length | description |
+-----------+-------+---------+--------+----------------------------+ +-----------+-------+---------+--------+----------------------------+
| HMAC | * | SHA-256 | 64 | HMAC w/ SHA-256 truncated | | HMAC | * | SHA-256 | 64 | HMAC w/ SHA-256 truncated |
| 256/64 | | | | to 64 bits | | 256/64 | | | | to 64 bits |
| | | | | | | | | | | |
| HMAC | 4 | SHA-256 | 256 | HMAC w/ SHA-256 | | HMAC | 4 | SHA-256 | 256 | HMAC w/ SHA-256 |
| 256/256 | | | | | | 256/256 | | | | |
| | | | | | | | | | | |
| HMAC | 5 | SHA-384 | 384 | HMAC w/ SHA-384 | | HMAC | 5 | SHA-384 | 384 | HMAC w/ SHA-384 |
| 384/384 | | | | | | 384/384 | | | | |
| | | | | | | | | | | |
| HMAC | 6 | SHA-512 | 512 | HMAC w/ SHA-512 | | HMAC | 6 | SHA-512 | 512 | HMAC w/ SHA-512 |
| 512/512 | | | | | | 512/512 | | | | |
+-----------+-------+---------+--------+----------------------------+ +-----------+-------+---------+--------+----------------------------+
Table 6: HMAC Algorithm Values Table 5: HMAC Algorithm Values
Some recipient algorithms carry the key while others derive a key Some recipient algorithms carry the key while others derive a key
from secret data. For those algorithms which carry the key (i.e. from secret data. For those algorithms which carry the key (i.e.
RSA-OAEP and AES-KeyWrap), the size of the HMAC key SHOULD be the RSA-OAEP and AES-KeyWrap), the size of the HMAC key SHOULD be the
same size as the underlying hash function. For those algorithms same size as the underlying hash function. For those algorithms
which derive the key, the derived key MUST be the same size as the which derive the key, the derived key MUST be the same size as the
underlying hash function. underlying hash function.
If the key obtained from a key structure, the key type MUST be If the key obtained from a key structure, the key type MUST be
'Symmetric'. Implementations creating and validating MAC values MUST 'Symmetric'. Implementations creating and validating MAC values MUST
skipping to change at page 34, line 15 skipping to change at page 32, line 13
related to the security of an HMAC operation. related to the security of an HMAC operation.
9.2. AES Message Authentication Code (AES-CBC-MAC) 9.2. AES Message Authentication Code (AES-CBC-MAC)
AES-CBC-MAC is defined in [MAC]. AES-CBC-MAC is defined in [MAC].
AES-CBC-MAC is parameterized by the key length, the authentication AES-CBC-MAC is parameterized by the key length, the authentication
tag length and the IV used. For all of these algorithms, the IV is tag length and the IV used. For all of these algorithms, the IV is
fixed to all zeros. We provide an array of algorithms for various fixed to all zeros. We provide an array of algorithms for various
key lengths and tag lengths. The algorithms defined in this document key lengths and tag lengths. The algorithms defined in this document
are found in Table 7. are found in Table 6.
+-------------+-------+----------+----------+-----------------------+ +-------------+-------+----------+----------+-----------------------+
| name | value | key | tag | description | | name | value | key | tag | description |
| | | length | length | | | | | length | length | |
+-------------+-------+----------+----------+-----------------------+ +-------------+-------+----------+----------+-----------------------+
| AES-MAC | * | 128 | 64 | AES-MAC 128 bit key, | | AES-MAC | * | 128 | 64 | AES-MAC 128 bit key, |
| 128/64 | | | | 64-bit tag | | 128/64 | | | | 64-bit tag |
| | | | | | | | | | | |
| AES-MAC | * | 256 | 64 | AES-MAC 256 bit key, | | AES-MAC | * | 256 | 64 | AES-MAC 256 bit key, |
| 256/64 | | | | 64-bit tag | | 256/64 | | | | 64-bit tag |
| | | | | | | | | | | |
| AES-MAC | * | 128 | 128 | AES-MAC 128 bit key, | | AES-MAC | * | 128 | 128 | AES-MAC 128 bit key, |
| 128/128 | | | | 128-bit tag | | 128/128 | | | | 128-bit tag |
| | | | | | | | | | | |
| AES-MAC | * | 256 | 128 | AES-MAC 256 bit key, | | AES-MAC | * | 256 | 128 | AES-MAC 256 bit key, |
| 256/128 | | | | 128-bit tag | | 256/128 | | | | 128-bit tag |
+-------------+-------+----------+----------+-----------------------+ +-------------+-------+----------+----------+-----------------------+
Table 7: AES-MAC Algorithm Values Table 6: AES-MAC Algorithm Values
Keys may be obtained either from a key structure or from a recipient Keys may be obtained either from a key structure or from a recipient
structure. If the key obtained from a key structure, the key type structure. If the key obtained from a key structure, the key type
MUST be 'Symmetric'. Implementations creating and validating MAC MUST be 'Symmetric'. Implementations creating and validating MAC
values MUST validate that the key type, key length and algorithm are values MUST validate that the key type, key length and algorithm are
correct and appropriate for the entities involved. correct and appropriate for the entities involved.
9.2.1. Security Considerations 9.2.1. Security Considerations
A number of attacks exist against CBC-MAC that need to be considered. A number of attacks exist against CBC-MAC that need to be considered.
o A single key must only be used for messages of a fixed and known o A single key must only be used for messages of a fixed and known
length. If this is not the case, an attacker will be able to length. If this is not the case, an attacker will be able to
generated a message with a valid tag given two message, tag pairs. generate a message with a valid tag given two message, tag pairs.
This can be addressed by using different keys for different length This can be addressed by using different keys for different length
messages. (CMAC mode also addresses this issue.) messages. (CMAC mode also addresses this issue.)
o If the same key is used for both encryption and authentication o If the same key is used for both encryption and authentication
operations, using CBC modes an attacker can produce messages with operations, using CBC modes an attacker can produce messages with
a valid authentication code. a valid authentication code.
o If the IV can be modified, then messages can be forged. This is o If the IV can be modified, then messages can be forged. This is
addressed by fixing the IV to all zeros. addressed by fixing the IV to all zeros.
10. Content Encryption Algorithms 10. Content Encryption Algorithms
Content Encryption Algorithms provide data confidentialty for Content Encryption Algorithms provide data confidentiality for
potentially large blocks of data using a symmetric key. They provide potentially large blocks of data using a symmetric key. They provide
either no or very limited data origination. (One cannot, for either no or very limited data origination. (One cannot, for
example, be used to prove the identity of the sender to a third example, be used to prove the identity of the sender to a third
party.) The ability to provide data origination is linked to how the party.) The ability to provide data origination is linked to how the
symmetric key is obtained. symmetric key is obtained.
We restrict the set of legal content encryption algorithms to those We restrict the set of legal content encryption algorithms to those
which support authentication both of the content and additional data. which support authentication both of the content and additional data.
The encryption process will generate some type of authentication The encryption process will generate some type of authentication
value, but that value may be either explicit or implicit in terms of value, but that value may be either explicit or implicit in terms of
skipping to change at page 35, line 40 skipping to change at page 33, line 36
valid, message content = Decrypt(cipher text, key, additional data) valid, message content = Decrypt(cipher text, key, additional data)
Most AEAD algorithms are logically defined as returning the message Most AEAD algorithms are logically defined as returning the message
content only if the decryption is valid. Many but not all content only if the decryption is valid. Many but not all
implementations will follow this convention. The message content implementations will follow this convention. The message content
MUST NOT be used if the decryption does not validate. MUST NOT be used if the decryption does not validate.
10.1. AES GCM 10.1. AES GCM
The GCM mode is is a generic authenticated encryption block cipher The GCM mode is a generic authenticated encryption block cipher mode
mode defined in [AES-GCM]. The GCM mode is combined with the AES defined in [AES-GCM]. The GCM mode is combined with the AES block
block encryption algorithm to define a an AEAD cipher. encryption algorithm to define an AEAD cipher.
The GCM mode is parameterized with by the size of the authentication The GCM mode is parameterized with by the size of the authentication
tag. The size of the authentication tag is limited to a small set of tag. The size of the authentication tag is limited to a small set of
values. For this document however, the size of the authentication values. For this document however, the size of the authentication
tag is fixed at 128-bits. tag is fixed at 128-bits.
The set of algorithms defined in this document are in Table 8. The set of algorithms defined in this document are in Table 7.
+---------+-------+-----------------------------+ +---------+-------+-----------------------------+
| name | value | description | | name | value | description |
+---------+-------+-----------------------------+ +---------+-------+-----------------------------+
| A128GCM | 1 | AES-GCM mode w/ 128-bit key | | A128GCM | 1 | AES-GCM mode w/ 128-bit key |
| | | | | | | |
| A192GCM | 2 | AES-GCM mode w/ 192-bit key | | A192GCM | 2 | AES-GCM mode w/ 192-bit key |
| | | | | | | |
| A256GCM | 3 | AES-GCM mode w/ 256-bit key | | A256GCM | 3 | AES-GCM mode w/ 256-bit key |
+---------+-------+-----------------------------+ +---------+-------+-----------------------------+
Table 8: Algorithm Value for AES-GCM Table 7: Algorithm Value for AES-GCM
Keys may be obtained either from a key structure or from a recipient Keys may be obtained either from a key structure or from a recipient
structure. If the key obtained from a key structure, the key type structure. If the key obtained from a key structure, the key type
MUST be 'Symmetric'. Implementations creating and validating MAC MUST be 'Symmetric'. Implementations creating and validating MAC
values MUST validate that the key type, key length and algorithm are values MUST validate that the key type, key length and algorithm are
correct and appropriate for the entities involved. correct and appropriate for the entities involved.
10.1.1. Security Considerations 10.1.1. Security Considerations
When using AES-CCM the following restrictions MUST be enforced: When using AES-CCM the following restrictions MUST be enforced:
o The key and nonce pair MUST be unique for every message encrypted. o The key and nonce pair MUST be unique for every message encrypted.
o The total amount of data encrypted MUST NOT exceed 2^39 - 256 bits o The total amount of data encrypted MUST NOT exceed 2^39 - 256
. An explicit check is required only in environments where it is bits. An explicit check is required only in environments where it
expected that it might be exceeded. is expected that it might be exceeded.
10.2. AES CCM 10.2. AES CCM
Counter with CBC-MAC (CCM) is a generic authentication encryption Counter with CBC-MAC (CCM) is a generic authentication encryption
block cipher mode defined in [RFC3610]. The CCM mode is combined block cipher mode defined in [RFC3610]. The CCM mode is combined
with the AES block encryption algorithm to define a commonly used with the AES block encryption algorithm to define a commonly used
content encryption algorithm used in constrainted devices. content encryption algorithm used in constrained devices.
The CCM mode has two parameter choices. The first choice is M, the The CCM mode has two parameter choices. The first choice is M, the
size of the authentication field. The choice of the value for M size of the authentication field. The choice of the value for M
involves a trade-off between message expansion and the probably that involves a trade-off between message expansion and the probably that
an attacker can undetecably modify a message. The second choice is an attacker can undetectably modify a message. The second choice is
L, the size of the length field. This value requires a trade-off L, the size of the length field. This value requires a trade-off
between the maximum message size and the size of the Nonce. between the maximum message size and the size of the Nonce.
It is unfortunate that the specification for CCM specified L and M as It is unfortunate that the specification for CCM specified L and M as
a count of bytes rather than a count of bits. This leads to possible a count of bytes rather than a count of bits. This leads to possible
misunderstandings where AES-CCM-8 is frequently used to refer to a misunderstandings where AES-CCM-8 is frequently used to refer to a
version of CCM mode where the size of the authentication is 64-bits version of CCM mode where the size of the authentication is 64-bits
and not 8-bits. These values have traditionally been specified as and not 8-bits. These values have traditionally been specified as
bit counts rather than byte counts. This document will follow the bit counts rather than byte counts. This document will follow the
tradition of using bit counts so that it is easier to compare the tradition of using bit counts so that it is easier to compare the
skipping to change at page 37, line 20 skipping to change at page 35, line 20
specific cryptographic operations. This favors smaller values of M specific cryptographic operations. This favors smaller values of M
and larger values of L. Less constrained devices do will want to be and larger values of L. Less constrained devices do will want to be
able to user larger messages and are more willing to generate new able to user larger messages and are more willing to generate new
keys for every operation. This favors larger values of M and smaller keys for every operation. This favors larger values of M and smaller
values of L. (The use of a large nonce means that random generation values of L. (The use of a large nonce means that random generation
of both the key and the nonce will decrease the chances of repeating of both the key and the nonce will decrease the chances of repeating
the pair on two different messages.) the pair on two different messages.)
The following values are used for L: The following values are used for L:
16-bits (2) limits messages to 2^16 bytes (64Kbyte) in length. This 16-bits (2) limits messages to 2^16 bytes (64 KiB) in length. This
sufficently long for messages in the constrainted world. The sufficiently long for messages in the constrained world. The
nonce length is 13 bytes allowing for 2^(13*8) possible values of nonce length is 13 bytes allowing for 2^(13*8) possible values of
the nonce without repeating. the nonce without repeating.
64-bits (8) limits messages to 2^64 byes in length. The nonce 64-bits (8) limits messages to 2^64 bytes in length. The nonce
length is 7 bytes allowing for 2^56 possible values of the nonce length is 7 bytes allowing for 2^56 possible values of the nonce
without repeating. without repeating.
The following values are used for M: The following values are used for M:
64-bits (8) produces a 64-bit authentication tag. This implies that 64-bits (8) produces a 64-bit authentication tag. This implies that
there is a 1 in 2^64 chance that an modified message will there is a 1 in 2^64 chance that a modified message will
authenticate. authenticate.
128-bits (16) produces a 128-bit authentication tag. This implies 128-bits (16) produces a 128-bit authentication tag. This implies
that there is a 1 in 2^128 chance that an modified message will that there is a 1 in 2^128 chance that a modified message will
authenticate. authenticate.
+--------------------+-------+----+-----+-----+---------------------+ +--------------------+-------+----+-----+-----+---------------------+
| name | value | L | M | k | description | | name | value | L | M | k | description |
+--------------------+-------+----+-----+-----+---------------------+ +--------------------+-------+----+-----+-----+---------------------+
| AES-CCM-16-64-128 | 10 | 16 | 64 | 128 | AES-CCM mode | | AES-CCM-16-64-128 | 10 | 16 | 64 | 128 | AES-CCM mode |
| | | | | | 128-bit key, 64-bit | | | | | | | 128-bit key, 64-bit |
| | | | | | tag, 13-byte nonce | | | | | | | tag, 13-byte nonce |
| | | | | | | | | | | | | |
| AES-CCM-16-64-256 | 11 | 16 | 64 | 256 | AES-CCM mode | | AES-CCM-16-64-256 | 11 | 16 | 64 | 256 | AES-CCM mode |
skipping to change at page 38, line 45 skipping to change at page 36, line 45
| | | | | | 128-bit key, | | | | | | | 128-bit key, |
| | | | | | 128-bit tag, 7-byte | | | | | | | 128-bit tag, 7-byte |
| | | | | | nonce | | | | | | | nonce |
| | | | | | | | | | | | | |
| AES-CCM-64-128-256 | 33 | 64 | 128 | 256 | AES-CCM mode | | AES-CCM-64-128-256 | 33 | 64 | 128 | 256 | AES-CCM mode |
| | | | | | 256-bit key, | | | | | | | 256-bit key, |
| | | | | | 128-bit tag, 7-byte | | | | | | | 128-bit tag, 7-byte |
| | | | | | nonce | | | | | | | nonce |
+--------------------+-------+----+-----+-----+---------------------+ +--------------------+-------+----+-----+-----+---------------------+
Table 9: Algorithm Values for AES-CCM Table 8: Algorithm Values for AES-CCM
Keys may be obtained either from a key structure or from a recipient Keys may be obtained either from a key structure or from a recipient
structure. If the key obtained from a key structure, the key type structure. If the key obtained from a key structure, the key type
MUST be 'Symmetric'. Implementations creating and validating MAC MUST be 'Symmetric'. Implementations creating and validating MAC
values MUST validate that the key type, key length and algorithm are values MUST validate that the key type, key length and algorithm are
correct and appropriate for the entities involved. correct and appropriate for the entities involved.
10.2.1. Security Considerations 10.2.1. Security Considerations
When using AES-CCM the following restrictions MUST be enforced: When using AES-CCM the following restrictions MUST be enforced:
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10.3. ChaCha20 and Poly1305 10.3. ChaCha20 and Poly1305
ChaCha20 and Poly1305 combined together is a new AEAD mode that is ChaCha20 and Poly1305 combined together is a new AEAD mode that is
defined in [RFC7539]. This is a new algorithm defined to be a cipher defined in [RFC7539]. This is a new algorithm defined to be a cipher
which is not AES and thus would not suffer from any future weaknesses which is not AES and thus would not suffer from any future weaknesses
found in AES. These cryptographic functions are designed to be fast found in AES. These cryptographic functions are designed to be fast
in software only implementations. in software only implementations.
The ChaCha20/Poly1305 AEAD construction defined in [RFC7539] has no The ChaCha20/Poly1305 AEAD construction defined in [RFC7539] has no
parameterization. It takes a 256-bit key and an a 96-bit nonce as parameterization. It takes a 256-bit key and a 96-bit nonce as well
well as the plain text and additional data as inputs and produces the as the plain text and additional data as inputs and produces the
cipher text as an option. We define one algorithm identifier for cipher text as an option. We define one algorithm identifier for
this algorithm in Table 10. this algorithm in Table 9.
+-------------------+-------+----------------------------------+ +-------------------+-------+----------------------------------+
| name | value | description | | name | value | description |
+-------------------+-------+----------------------------------+ +-------------------+-------+----------------------------------+
| ChaCha20/Poly1305 | 11 | ChaCha20/Poly1305 w/ 256-bit key | | ChaCha20/Poly1305 | 11 | ChaCha20/Poly1305 w/ 256-bit key |
+-------------------+-------+----------------------------------+ +-------------------+-------+----------------------------------+
Table 10: Algorithm Value for AES-GCM Table 9: Algorithm Value for AES-GCM
Keys may be obtained either from a key structure or from a recipient Keys may be obtained either from a key structure or from a recipient
structure. If the key obtained from a key structure, the key type structure. If the key obtained from a key structure, the key type
MUST be 'Symmetric'. Implementations creating and validating MAC MUST be 'Symmetric'. Implementations creating and validating MAC
values MUST validate that the key type, key length and algorithm are values MUST validate that the key type, key length and algorithm are
correct and appropriate for the entities involved. correct and appropriate for the entities involved.
10.3.1. Security Considerations 10.3.1. Security Considerations
The pair of key, nonce MUST be unique for every invocation of the The pair of key, nonce MUST be unique for every invocation of the
skipping to change at page 41, line 9 skipping to change at page 39, line 9
context information. Context information is used to allow for context information. Context information is used to allow for
different keying information to be derived from the same secret. The different keying information to be derived from the same secret. The
use of context based keying material is considered to be a good use of context based keying material is considered to be a good
security practice. This document defines a single context structure security practice. This document defines a single context structure
and a single KDF function. and a single KDF function.
11.1. HMAC-based Extract-and-Expand Key Derivation Function (HKDF) 11.1. HMAC-based Extract-and-Expand Key Derivation Function (HKDF)
The HKDF key derivation algorithm is defined in [RFC5869]. The HKDF key derivation algorithm is defined in [RFC5869].
The HKDF algorithm is defined to take a number of inputs These inputs The HKDF algorithm is defined to take a number of inputs. These
are: inputs are:
secret - a shared value that is secret. Secrets may be either secret - a shared value that is secret. Secrets may be either
previously shared or derived from operations like a DH key previously shared or derived from operations like a DH key
agreement. agreement.
salt - an optional public value that is used to change the salt - an optional public value that is used to change the
generation process. If specified, the salt is carried using the generation process. If specified, the salt is carried using the
'salt' algorithm parameter. While [RFC5869] suggests that the 'salt' algorithm parameter. While [RFC5869] suggests that the
length of the salt be the same as the length of the underlying length of the salt be the same as the length of the underlying
hash value, any amount of salt will improve the security as hash value, any amount of salt will improve the security as
different key values will be generated. A parameter to carry the different key values will be generated. A parameter to carry the
salt is defined in Table 12. This parameter is protected by being salt is defined in Table 11. This parameter is protected by being
included in the key computation and does not need to be separately included in the key computation and does not need to be separately
authenticated. authenticated.
length - the number of bytes of output that need to be generated. length - the number of bytes of output that need to be generated.
context information - Information that describes the context in context information - Information that describes the context in
which the resulting value will be used. Making this information which the resulting value will be used. Making this information
specific to the context that the material is going to be used specific to the context that the material is going to be used
ensures that the resulting material will always be unique. The ensures that the resulting material will always be unique. The
context structure used is encoded into the algorithm identifier. context structure used is encoded into the algorithm identifier.
skipping to change at page 41, line 45 skipping to change at page 39, line 45
HKDF algorithm. The hash function is encoded into the HKDF HKDF algorithm. The hash function is encoded into the HKDF
algorithm selection. algorithm selection.
HKDF is defined to use HMAC as the underlying PRF. However, it is HKDF is defined to use HMAC as the underlying PRF. However, it is
possible to use other functions in the same construct to provide a possible to use other functions in the same construct to provide a
different KDF function that may be more appropriate in the different KDF function that may be more appropriate in the
constrained world. Specifically, one can use AES-CBC-MAC as the PRF constrained world. Specifically, one can use AES-CBC-MAC as the PRF
for the expand step, but not for the extract step. When using a good for the expand step, but not for the extract step. When using a good
random shared secret of the correct length, the extract step can be random shared secret of the correct length, the extract step can be
skipped. The extract cannot be skipped if the secret is not skipped. The extract cannot be skipped if the secret is not
uniformly random, for example if it is the result of a ECDH key uniformly random, for example if it is the result of an ECDH key
agreement step. agreement step.
The algorithms defined in this document are found in Table 11 The algorithms defined in this document are found in Table 10
+-------------+-------------+----------+----------------------------+ +-------------+-------------+----------+----------------------------+
| name | hash | Skip | context | | name | hash | Skip | context |
| | | extract | | | | | extract | |
+-------------+-------------+----------+----------------------------+ +-------------+-------------+----------+----------------------------+
| HKDF | SHA-256 | no | XXX | | HKDF | SHA-256 | no | XXX |
| SHA-256 | | | | | SHA-256 | | | |
| | | | | | | | | |
| HKDF | SHA-512 | no | XXX | | HKDF | SHA-512 | no | XXX |
| SHA-512 | | | | | SHA-512 | | | |
| | | | | | | | | |
| HKDF AES- | AES-CBC-128 | yes | HKDF using AES-MAC as the | | HKDF AES- | AES-CBC-128 | yes | HKDF using AES-MAC as the |
| MAC-128 | | | PRF w/ 128-bit key | | MAC-128 | | | PRF w/ 128-bit key |
| | | | | | | | | |
| HKDF AES- | AES-CBC-128 | yes | HKDF using AES-MAC as the | | HKDF AES- | AES-CBC-128 | yes | HKDF using AES-MAC as the |
| MAC-256 | | | PRF w/ 256-bit key | | MAC-256 | | | PRF w/ 256-bit key |
+-------------+-------------+----------+----------------------------+ +-------------+-------------+----------+----------------------------+
Table 11: HKDF algorithms Table 10: HKDF algorithms
+------+-------+------+-------------+ +------+-------+------+-------------+
| name | label | type | description | | name | label | type | description |
+------+-------+------+-------------+ +------+-------+------+-------------+
| salt | -20 | bstr | Random salt | | salt | -20 | bstr | Random salt |
+------+-------+------+-------------+ +------+-------+------+-------------+
Table 12: HKDF Algorithm Parameters Table 11: HKDF Algorithm Parameters
11.2. Context Information Structure 11.2. Context Information Structure
The context information structure is used to ensure that the derived The context information structure is used to ensure that the derived
keying material is "bound" to the context of the transaction. The keying material is "bound" to the context of the transaction. The
context information structure used here is based on that defined in context information structure used here is based on that defined in
[SP800-56A]. By using CBOR for the encoding of the context [SP800-56A]. By using CBOR for the encoding of the context
information structure, we automatically get the same type of type and information structure, we automatically get the same type of type and
length separation of fields that is obtained by the use of ASN.1. length separation of fields that is obtained by the use of ASN.1.
This means that there is no need to encode the lengths for the base This means that there is no need to encode the lengths for the base
elements as it is done by the JOSE encoding. [CREF11] elements as it is done by the JOSE encoding. [CREF7]
The context information structure refers to PartyU and PartyV as the The context information structure refers to PartyU and PartyV as the
two parties which are doing the key derivation. Unless the two parties which are doing the key derivation. Unless the
application protocol defines differently, we assign PartyU to the application protocol defines differently, we assign PartyU to the
entity that is creating the message and PartyV to the entity that is entity that is creating the message and PartyV to the entity that is
receiving the message. By doing this association, different keys receiving the message. By doing this association, different keys
will be derived for each direction as the context information is will be derived for each direction as the context information is
different in each direction. different in each direction.
Application protocols are free to define the roles differently. For Application protocols are free to define the roles differently. For
skipping to change at page 43, line 19 skipping to change at page 41, line 19
supplemental fields or as the salt if one is using HKDF, ensures that supplemental fields or as the salt if one is using HKDF, ensures that
a unique key is generated for each set of transactions. Combining a unique key is generated for each set of transactions. Combining
nonce fields with the transaction identifier provides a method so nonce fields with the transaction identifier provides a method so
that a different key is used for each message in each direction. that a different key is used for each message in each direction.
The context structure is built from information that is known to both The context structure is built from information that is known to both
entities. Some of the information is known only to the two entities, entities. Some of the information is known only to the two entities,
some is implied based on the application and some is explicitly some is implied based on the application and some is explicitly
transported as part of the message. The information that can be transported as part of the message. The information that can be
carried in the message, parameters have been defined and can be found carried in the message, parameters have been defined and can be found
in Table 13. These parameters are designed to be placed in the in Table 12. These parameters are designed to be placed in the
unprotected bucket of the recipient structure. (They do not need to unprotected bucket of the recipient structure. (They do not need to
be in the protected bucket since they already are included in the be in the protected bucket since they already are included in the
cryptographic computation by virtue of being included in the context cryptographic computation by virtue of being included in the context
structure.) structure.)
We encode the context specific information using a CBOR array type. We encode the context specific information using a CBOR array type.
The fields in the array are: The fields in the array are:
AlgorithmID This field indicates the algorithm for which the key AlgorithmID This field indicates the algorithm for which the key
material will be used. This field is required to be present and material will be used. This field is required to be present and
is a copy of the algorithm identifier in the message. The field is a copy of the algorithm identifier in the message. The field
exists in the context information so that if the same environment exists in the context information so that if the same environment
is used for different algorithms, then completely different keys is used for different algorithms, then completely different keys
will be generated each of those algorithms. (This practice means will be generated each of those algorithms. (This practice means
if algorithm A is broken and thus can is easier to find, the key if algorithm A is broken and thus can is easier to find, the key
derived for algorithm B will not be the same as the key for derived for algorithm B will not be the same as the key for
algorithm B.) algorithm B.)
PartyUInfo This field holds information about party U. The PartyUInfo This field holds information about party U. The
PartyUInfo is encoded as a CBOR struture. The elements of PartyUInfo is encoded as a CBOR structure. The elements of
PartyUInfo are encoded in the order presented, however if the PartyUInfo are encoded in the order presented, however if the
element does not exist no element is placed in the array. The element does not exist no element is placed in the array. The
elements of the PartyUInfo array are: elements of the PartyUInfo array are:
identity This contains the identity information for party U. The identity This contains the identity information for party U. The
identities can be assigned in one of two manners. Firstly, a identities can be assigned in one of two manners. Firstly, a
protocol can assign identities based on roles. For example, protocol can assign identities based on roles. For example,
the roles of "client" and "server" may be assigned to different the roles of "client" and "server" may be assigned to different
entities in the protocol. Each entity would then use the entities in the protocol. Each entity would then use the
correct label for the data they they send or receive. The correct label for the data they send or receive. The second
second way is for a protocol to assign identities is to use a way is for a protocol to assign identities is to use a name
name based on a naming system (i.e. DNS, X.509 names). based on a naming system (i.e. DNS, X.509 names).
We define an algorithm parameter 'PartyU identity' that can be We define an algorithm parameter 'PartyU identity' that can be
used to carry identity information in the message. However, used to carry identity information in the message. However,
identity information is often known as part of the protocol and identity information is often known as part of the protocol and
can thus be inferred rather than made explicit. If identity can thus be inferred rather than made explicit. If identity
information is carried in the message, applications SHOULD have information is carried in the message, applications SHOULD have
a way of validating the supplied identity information. The a way of validating the supplied identity information. The
identity information does not need to be specified and can be identity information does not need to be specified and can be
left as absent. left as absent.
The identity value supplied will be integrity checked as part The identity value supplied will be integrity checked as part
skipping to change at page 45, line 34 skipping to change at page 43, line 34
| PartyV | -24 | bstr | Party V identity Information | | PartyV | -24 | bstr | Party V identity Information |
| identity | | | | | identity | | | |
| | | | | | | | | |
| PartyV nonce | -25 | bstr / | Party V provided nonce | | PartyV nonce | -25 | bstr / | Party V provided nonce |
| | | int | | | | | int | |
| | | | | | | | | |
| PartyV other | -26 | bstr | Party V other provided | | PartyV other | -26 | bstr | Party V other provided |
| | | | information | | | | | information |
+---------------+-------+-----------+-------------------------------+ +---------------+-------+-----------+-------------------------------+
Table 13: Context Algorithm Parameters Table 12: Context Algorithm Parameters
Text from here to start of next section to be removed Text from here to start of next section to be removed
COSE_KDF_Context = [ COSE_KDF_Context = [
AlgorithmID : int / tstr, AlgorithmID : int / tstr,
PartyUInfo : [ PartyUInfo : [
? nonce : bstr / int, ? nonce : bstr / int,
? identity : bstr, ? identity : bstr,
? other : bstr ? other : bstr
], ],
PartyVInfo : [ PartyVInfo : [
skipping to change at page 47, line 12 skipping to change at page 45, line 12
o The 'ciphertext' field MUST be a zero length item. o The 'ciphertext' field MUST be a zero length item.
o The 'recipients' field MUST be absent. o The 'recipients' field MUST be absent.
12.1.1. Direct Key 12.1.1. Direct Key
This recipient algorithm is the simplest, the supplied key is This recipient algorithm is the simplest, the supplied key is
directly used as the key for the next layer down in the message. directly used as the key for the next layer down in the message.
There are no algorithm parameters defined for this algorithm. The There are no algorithm parameters defined for this algorithm. The
algorithm identifier value is assigned in Table 14. algorithm identifier value is assigned in Table 13.
When this algorithm is used, the protected field MUST be zero length. When this algorithm is used, the protected field MUST be zero length.
The key type MUST be 'Symmetric'. The key type MUST be 'Symmetric'.
+--------+-------+-------------------+ +--------+-------+-------------------+
| name | value | description | | name | value | description |
+--------+-------+-------------------+ +--------+-------+-------------------+
| direct | -6 | Direct use of CEK | | direct | -6 | Direct use of CEK |
+--------+-------+-------------------+ +--------+-------+-------------------+
Table 14: Direct Key Table 13: Direct Key
12.1.1.1. Security Considerations 12.1.1.1. Security Considerations
This recipient algorithm has several potential problems that need to This recipient algorithm has several potential problems that need to
be considered: be considered:
o These keys need to have some method to be regularly updated over o These keys need to have some method to be regularly updated over
time. All of the content encryption algorithms specified in this time. All of the content encryption algorithms specified in this
document have limits on how many times a key can be used without document have limits on how many times a key can be used without
significant loss of security. significant loss of security.
skipping to change at page 48, line 24 skipping to change at page 46, line 24
A new IV must be used if the same key is used in more than one A new IV must be used if the same key is used in more than one
message. The IV can be modified in a predictable manner, a random message. The IV can be modified in a predictable manner, a random
manner or an unpredictable manner. One unpredictable manner that can manner or an unpredictable manner. One unpredictable manner that can
be used is to use the HKDF function to generate the IV. If HKDF is be used is to use the HKDF function to generate the IV. If HKDF is
used for generating the IV, the algorithm identifier is set to "IV- used for generating the IV, the algorithm identifier is set to "IV-
GENERATION". GENERATION".
When these algorithms are used, the key type MUST be 'symmetric'. When these algorithms are used, the key type MUST be 'symmetric'.
The set of algorithms defined in this document can be found in The set of algorithms defined in this document can be found in
Table 15. Table 14.
+---------------------+-------+-------------+-----------------------+ +---------------------+-------+-------------+-----------------------+
| name | value | KDF | description | | name | value | KDF | description |
+---------------------+-------+-------------+-----------------------+ +---------------------+-------+-------------+-----------------------+
| direct+HKDF-SHA-256 | * | HKDF | Shared secret w/ HKDF | | direct+HKDF-SHA-256 | * | HKDF | Shared secret w/ HKDF |
| | | SHA-256 | and SHA-256 | | | | SHA-256 | and SHA-256 |
| | | | | | | | | |
| direct+HKDF-SHA-512 | * | HKDF | Shared secret w/ HKDF | | direct+HKDF-SHA-512 | * | HKDF | Shared secret w/ HKDF |
| | | SHA-512 | and SHA-512 | | | | SHA-512 | and SHA-512 |
| | | | | | | | | |
| direct+HKDF-AES-128 | * | HKDF AES- | Shared secret w/ AES- | | direct+HKDF-AES-128 | * | HKDF AES- | Shared secret w/ AES- |
| | | MAC-128 | MAC 128-bit key | | | | MAC-128 | MAC 128-bit key |
| | | | | | | | | |
| direct+HKDF-AES-256 | * | HKDF AES- | Shared secret w/ AES- | | direct+HKDF-AES-256 | * | HKDF AES- | Shared secret w/ AES- |
| | | MAC-256 | MAC 256-bit key | | | | MAC-256 | MAC 256-bit key |
+---------------------+-------+-------------+-----------------------+ +---------------------+-------+-------------+-----------------------+
Table 15: Direct Key Table 14: Direct Key
12.1.2.1. Security Considerations 12.1.2.1. Security Considerations
The shared secret need to have some method to be regularly updated The shared secret need to have some method to be regularly updated
over time. The shared secret is forming the basis of trust, although over time. The shared secret is forming the basis of trust, although
not used directly it should still be subject to scheduled rotation. not used directly it should still be subject to scheduled rotation.
12.2. Key Wrapping 12.2. Key Wrapping
In key wrapping mode, the CEK is randomly generated and that key is In key wrapping mode, the CEK is randomly generated and that key is
skipping to change at page 50, line 15 skipping to change at page 48, line 15
+--------+-------+----------+-----------------------------+ +--------+-------+----------+-----------------------------+
| name | value | key size | description | | name | value | key size | description |
+--------+-------+----------+-----------------------------+ +--------+-------+----------+-----------------------------+
| A128KW | -3 | 128 | AES Key Wrap w/ 128-bit key | | A128KW | -3 | 128 | AES Key Wrap w/ 128-bit key |
| | | | | | | | | |
| A192KW | -4 | 192 | AES Key Wrap w/ 192-bit key | | A192KW | -4 | 192 | AES Key Wrap w/ 192-bit key |
| | | | | | | | | |
| A256KW | -5 | 256 | AES Key Wrap w/ 256-bit key | | A256KW | -5 | 256 | AES Key Wrap w/ 256-bit key |
+--------+-------+----------+-----------------------------+ +--------+-------+----------+-----------------------------+
Table 16: AES Key Wrap Algorithm Values Table 15: AES Key Wrap Algorithm Values
12.2.1.1. Security Considerations for AES-KW 12.2.1.1. Security Considerations for AES-KW
The shared secret need to have some method to be regularly updated The shared secret need to have some method to be regularly updated
over time. The shared secret is forming the basis of trust, although over time. The shared secret is forming the basis of trust, although
not used directly it should still be subject to scheduled rotation. not used directly it should still be subject to scheduled rotation.
12.3. Key Encryption 12.3. Key Encryption
Key Encryption mode is also called key transport mode in some Key Encryption mode is also called key transport mode in some
skipping to change at page 50, line 43 skipping to change at page 48, line 43
o The 'protected' field MUST be absent. o The 'protected' field MUST be absent.
o The plain text to be encrypted is the key from next layer down o The plain text to be encrypted is the key from next layer down
(usually the content layer). (usually the content layer).
o At a minimum, the 'unprotected' field MUST contain the 'alg' o At a minimum, the 'unprotected' field MUST contain the 'alg'
parameter and SHOULD contain a parameter identifying the parameter and SHOULD contain a parameter identifying the
asymmetric key. asymmetric key.
12.3.1. RSAES-OAEP
RSAES-OAEP is an asymmetric key encryption algorithm. The defintion
of RSAEA-OAEP can be find in Section 7.1 of [RFC3447]. The algorithm
is parameterized using a masking generation function (mgf), a hash
function (h) and encoding parameters (P). For the algorithm
identifiers defined in this section:
o mgf is always set to MFG1 from [RFC3447] and uses the same hash
function as h.
o P is always set to the empty octet string.
Table 17 summarizes the rest of the values.
+----------------------+-------+---------+-----------------------+
| name | value | hash | description |
+----------------------+-------+---------+-----------------------+
| RSAES-OAEP w/SHA-256 | -25 | SHA-256 | RSAES OAEP w/ SHA-256 |
| | | | |
| RSAES-OAEP w/SHA-512 | -26 | SHA-512 | RSAES OAEP w/ SHA-512 |
+----------------------+-------+---------+-----------------------+
Table 17: RSAES-OAEP Algorithm Values
The key type MUST be 'RSA'.
12.3.1.1. Security Considerations for RSAES-OAEP
A key size of 2048 bits or larger MUST be used with these algorithms.
This key size corresponds roughly to the same strength as provided by
a 128-bit symmetric encryption algorithm.
It is highly recommended that checks on the key length be done before
starting a decryption operation. One potential denial of service
operation is to provide encrypted objects using either abnormally
long or oddly sized RSA modulus values. Implementations SHOULD be
able to encrypt and decrypt with modulus between 2048 and 16K bits in
length. Applications can impose additional restrictions on the
length of the modulus.
12.4. Direct Key Agreement 12.4. Direct Key Agreement
The 'direct key agreement' class of recipient algorithms uses a key The 'direct key agreement' class of recipient algorithms uses a key
agreement method to create a shared secret. A KDF is then applied to agreement method to create a shared secret. A KDF is then applied to
the shared secret to derive a key to be used in protecting the data. the shared secret to derive a key to be used in protecting the data.
This key is normally used as a CEK or MAC key, but could be used for This key is normally used as a CEK or MAC key, but could be used for
other purposes if more than two layers are in use (see Appendix B). other purposes if more than two layers are in use (see Appendix B).
The most commonly used key agreement algorithm used is Diffie- The most commonly used key agreement algorithm used is Diffie-
Hellman, but other variants exist. Since COSE is designed for a Hellman, but other variants exist. Since COSE is designed for a
skipping to change at page 52, line 40 skipping to change at page 49, line 47
o At a minimum, the 'unprotected' field MUST contain the 'alg' o At a minimum, the 'unprotected' field MUST contain the 'alg'
parameter and SHOULD contain a parameter identifying the parameter and SHOULD contain a parameter identifying the
recipient's asymmetric key. recipient's asymmetric key.
o The 'unprotected' field MUST contain the 'epk' parameter. o The 'unprotected' field MUST contain the 'epk' parameter.
12.4.1. ECDH 12.4.1. ECDH
The basic mathematics for Elliptic Curve Diffie-Hellman can be found The basic mathematics for Elliptic Curve Diffie-Hellman can be found
in [RFC6090]. Two new curves have been defined in in [RFC6090].
[I-D.irtf-cfrg-curves].
ECDH is parameterized by the following: ECDH is parameterized by the following:
o Curve Type/Curve: The curve selected controls not only the size of o Curve Type/Curve: The curve selected controls not only the size of
the shared secret, but the mathematics for computing the shared the shared secret, but the mathematics for computing the shared
secret. The curve selected also controls how a point in the curve secret. The curve selected also controls how a point in the curve
is represented and what happens for the identity points on the is represented and what happens for the identity points on the
curve. In this specification we allow for a number of different curve. In this specification we allow for a number of different
curves to be used. The curves are defined in Table 21. curves to be used. The curves are defined in Table 19.
Since the only the math is changed by changing the curve, the Since the only the math is changed by changing the curve, the
curve is not fixed for any of the algorithm identifiers we define, curve is not fixed for any of the algorithm identifiers we define,
instead it is defined by the points used. instead it is defined by the points used.
o Ephemeral-static or static-static: The key agreement process may o Ephemeral-static or static-static: The key agreement process may
be done using either a static or an ephemeral key at the senders be done using either a static or an ephemeral key at the sender's
side. When using ephemeral keys, the sender MUST generate a new side. When using ephemeral keys, the sender MUST generate a new
ephemeral key for every key agreement operation. The ephemeral ephemeral key for every key agreement operation. The ephemeral
key is placed in in the 'ephemeral key' parameter and MUST be key is placed in the 'ephemeral key' parameter and MUST be present
present for all algorithm identifiers which use ephemeral keys. for all algorithm identifiers which use ephemeral keys. When
When using static keys, the sender MUST either generate a new using static keys, the sender MUST either generate a new random
random value placed in either in the KDF parameters or the context value placed in either in the KDF parameters or the context
structure. For the KDF functions used, this means either in the structure. For the KDF functions used, this means either in the
'salt' parameter for HKDF (Table 12) or in in the 'PartyU nonce' 'salt' parameter for HKDF (Table 11) or in the 'PartyU nonce'
parameter for the context struture (Table 13) MUST be present. parameter for the context structure (Table 12) MUST be present.
(Both may be present if desired.) The value in the parameter MUST (Both may be present if desired.) The value in the parameter MUST
be unique for the key pair being used. It is acceptable to use a be unique for the key pair being used. It is acceptable to use a
global counter which is incremented for every static-static global counter which is incremented for every static-static
operation and use the resulting value. When using static keys, operation and use the resulting value. When using static keys,
the static key needs to be identified to the recipient. The the static key needs to be identified to the recipient. The
static key can be identified either by providing the key ('static static key can be identified either by providing the key ('static
key') or by providing a key identifier for the static key ('static key') or by providing a key identifier for the static key ('static
key id'). Both of these parameters are defined in Table 19 key id'). Both of these parameters are defined in Table 17
o Key derivation algorithm: The result of an ECDH key agreement o Key derivation algorithm: The result of an ECDH key agreement
process does not provide a uniformly random secret, as such it process does not provide a uniformly random secret, as such it
needs to be run through a KDF in order to produce a usable key. needs to be run through a KDF in order to produce a usable key.
Processing the secret through a KDF also allows for the Processing the secret through a KDF also allows for the
introduction of both context material, how the key is going to be introduction of both context material, how the key is going to be
used, and one time material in the even to of a static-static key used, and one time material in the even to of a static-static key
agreement. agreement.
o Key Wrap algorithm: The key wrap algorithm can be 'none' if the o Key Wrap algorithm: The key wrap algorithm can be 'none' if the
result of the KDF is going to be used as the key directly. This result of the KDF is going to be used as the key directly. This
option, along with static-static, should be used if knowledge option, along with static-static, should be used if knowledge
about the sender is desired. If 'none' is used then the content about the sender is desired. If 'none' is used then the content
layer encryption algorithm size is value fed to the context layer encryption algorithm size is value fed to the context
structure. Support is also provided for any of the key wrap structure. Support is also provided for any of the key wrap
algorithms defined in section Section 12.2.1. If one of these algorithms defined in Section 12.2.1. If one of these options is
options is used, the input key size to the key wrap algorithm is used, the input key size to the key wrap algorithm is the value
the value fed into the context structure as the key size. fed into the context structure as the key size.
The set of algorithms direct ECDH defined in this document are found The set of algorithms direct ECDH defined in this document are found
in Table 18. in Table 16.
+-------------+------+-------+----------------+--------+------------+ +-------------+------+-------+----------------+--------+------------+
| name | valu | KDF | Ephemeral- | Key | descriptio | | name | valu | KDF | Ephemeral- | Key | descriptio |
| | e | | Static | Wrap | n | | | e | | Static | Wrap | n |
+-------------+------+-------+----------------+--------+------------+ +-------------+------+-------+----------------+--------+------------+
| ECDH-ES + | 50 | HKDF | yes | none | ECDH ES w/ | | ECDH-ES + | 50 | HKDF | yes | none | ECDH ES w/ |
| HKDF-256 | | - SHA | | | HKDF - | | HKDF-256 | | - SHA | | | HKDF - |
| | | -256 | | | generate | | | | -256 | | | generate |
| | | | | | key | | | | | | | key |
| | | | | | directly | | | | | | | directly |
skipping to change at page 55, line 24 skipping to change at page 52, line 30
| | | | | | key | | | | | | | key |
| | | | | | | | | | | | | |
| ECDH- | 59 | HKDF | no | A256KW | ECDH SS w/ | | ECDH- | 59 | HKDF | no | A256KW | ECDH SS w/ |
| SS+A256KW | | - SHA | | | Concat KDF | | SS+A256KW | | - SHA | | | Concat KDF |
| | | -256 | | | and AES | | | | -256 | | | and AES |
| | | | | | Key wrap | | | | | | | Key wrap |
| | | | | | w/ 256 bit | | | | | | | w/ 256 bit |
| | | | | | key | | | | | | | key |
+-------------+------+-------+----------------+--------+------------+ +-------------+------+-------+----------------+--------+------------+
Table 18: ECDH Algorithm Values Table 16: ECDH Algorithm Values
+-----------+-------+----------+-----------+------------------------+ +-----------+-------+----------+-----------+------------------------+
| name | label | type | algorithm | description | | name | label | type | algorithm | description |
+-----------+-------+----------+-----------+------------------------+ +-----------+-------+----------+-----------+------------------------+
| ephemeral | -1 | COSE_Key | ECDH-ES | Ephemeral Public key | | ephemeral | -1 | COSE_Key | ECDH-ES | Ephemeral Public key |
| key | | | | for the sender | | key | | | | for the sender |
| | | | | | | | | | | |
| static | -2 | COSE_Key | ECDH-ES | Static Public key for | | static | -2 | COSE_Key | ECDH-ES | Static Public key for |
| key | | | | the sender | | key | | | | the sender |
| | | | | | | | | | | |
| static | -3 | bstr | ECDH-SS | Static Public key | | static | -3 | bstr | ECDH-SS | Static Public key |
| key id | | | | identifier for the | | key id | | | | identifier for the |
| | | | | sender | | | | | | sender |
+-----------+-------+----------+-----------+------------------------+ +-----------+-------+----------+-----------+------------------------+
Table 19: ECDH Algorithm Parameters Table 17: ECDH Algorithm Parameters
This document defines these algorithms to be used with the curves This document defines these algorithms to be used with the curves
P-256, P-384, P-521, X25519 and X448. Implementations MUST verify P-256, P-384, P-521. Implementations MUST verify that the key type
that the key type and curve are correct, different curves are and curve are correct, different curves are restricted to different
restricted to different key types. Implementations MUST verify that key types. Implementations MUST verify that the curve and algorithm
the curve and algorithm are appropriate for the entities involved. are appropriate for the entities involved.
12.5. Key Agreement with KDF 12.5. Key Agreement with KDF
Key Agreement with Key Wrapping uses a randomly generated CEK. The Key Agreement with Key Wrapping uses a randomly generated CEK. The
CEK is then encrypted using a Key Wrapping algorithm and a key CEK is then encrypted using a Key Wrapping algorithm and a key
derived from the shared secret computed by the key agreement derived from the shared secret computed by the key agreement
algorithm. algorithm.
The COSE_encrypt structure for the recipient is organized as follows: The COSE_encrypt structure for the recipient is organized as follows:
o The 'protected' field is fed into the KDF context structure. o The 'protected' field is fed into the KDF context structure.
o The plain text to be encrypted is the key from next layer down o The plain text to be encrypted is the key from next layer down
(usually the content layer). (usually the content layer).
o The 'alg' parameter MUST be present in the layer. o The 'alg' parameter MUST be present in the layer.
o A parameter identifying the recipient's key SHOULD be present. A o A parameter identifying the recipient's key SHOULD be present. A
parameter identifying the senders key SHOULD be present. parameter identifying the sender's key SHOULD be present.
12.5.1. ECDH 12.5.1. ECDH
These algorithms are defined in Table 18. These algorithms are defined in Table 16.
13. Keys 13. Keys
The COSE_Key object defines a way to hold a single key object, it is The COSE_Key object defines a way to hold a single key object, it is
still required that the members of individual key types be defined. still required that the members of individual key types be defined.
This section of the document is where we define an initial set of This section of the document is where we define an initial set of
members for specific key types. members for specific key types.
For each of the key types, we define both public and private members. For each of the key types, we define both public and private members.
The public members are what is transmitted to others for their usage. The public members are what is transmitted to others for their usage.
skipping to change at page 57, line 8 skipping to change at page 54, line 8
Centralized key creation for multi-cast type operations. Protocols Centralized key creation for multi-cast type operations. Protocols
where a shared secret is used as a bearer token for authorization where a shared secret is used as a bearer token for authorization
purposes. purposes.
Key types are identified by the 'kty' member of the COSE_Key object. Key types are identified by the 'kty' member of the COSE_Key object.
In this document we define four values for the member. In this document we define four values for the member.
+-----------+-------+--------------------------------------------+ +-----------+-------+--------------------------------------------+
| name | value | description | | name | value | description |
+-----------+-------+--------------------------------------------+ +-----------+-------+--------------------------------------------+
| EC1 | 1 | Elliptic Curve Keys w/ X Coordinate only |
| | | |
| EC2 | 2 | Elliptic Curve Keys w/ X,Y Coordinate pair | | EC2 | 2 | Elliptic Curve Keys w/ X,Y Coordinate pair |
| | | | | | | |
| RSA | 3 | RSA Keys |
| | | |
| Symmetric | 4 | Symmetric Keys | | Symmetric | 4 | Symmetric Keys |
| | | | | | | |
| Reserved | 0 | This value is reserved | | Reserved | 0 | This value is reserved |
+-----------+-------+--------------------------------------------+ +-----------+-------+--------------------------------------------+
Table 20: Key Type Values Table 18: Key Type Values
13.1. Elliptic Curve Keys 13.1. Elliptic Curve Keys
Two different key structures are being defined for Elliptic Curve Two different key structures could be defined for Elliptic Curve
keys. One version uses both an x and a y coordinate, potentially keys. One version uses both an x and a y coordinate, potentially
with point compression. This is the traditional EC point with point compression. This is the traditional EC point
representation that is used in [RFC5480]. The other version uses representation that is used in [RFC5480]. The other version uses
only the x coordinate as the y coordinate is either to be recomputed only the x coordinate as the y coordinate is either to be recomputed
or not needed for the key agreement operation. An example of this is or not needed for the key agreement operation Currently no algorithms
Curve25519 [I-D.irtf-cfrg-curves]. [CREF12] are defined using this key structure.
+------------+----------+-------+-----------------------------------+
| name | key type | value | description |
+------------+----------+-------+-----------------------------------+
| P-256 | EC2 | 1 | NIST P-256 also known as |
| | | | secp256r1 |
| | | | |
| P-384 | EC2 | 2 | NIST P-384 also known as |
| | | | secp384r1 |
| | | | |
| P-521 | EC2 | 3 | NIST P-521 also known as |
| | | | secp521r1 |
| | | | |
| Curve25519 | EC1 | 1 | Curve 25519 |
| | | | |
| Curve448 | EC1 | 2 | Curve 448 |
+------------+----------+-------+-----------------------------------+
Table 21: EC Curves
13.1.1. Single Coordinate Curves
One class of Elliptic Curve mathematics allows for a point to be
completely defined using the curve and the x coordinate of the point
on the curve. The two curves that are initially setup to use is
point format are Curve 25519 and Curve 448 which are defined in
[I-D.irtf-cfrg-curves].
For EC keys with only the x coordinates, the 'kty' member is set to 1
(EC1). The key parameters defined in this section are summarized in
Table 22. The members that are defined for this key type are:
crv contains an identifier of the curve to be used with the key.
[CREF13] The curves defined in this document for this key type can
be found in Table 21. Other curves may be registered in the
future and private curves can be used as well.
x contains the x coordinate for the EC point. The octet string
represents a little-endian encoding of x.
d contains the private key.
For public keys, it is REQUIRED that 'crv' and 'x' be present in the
structure. For private keys, it is REQUIRED that 'crv' and 'd' be
present in the structure. For private keys, it is RECOMMENDED that
'x' also be present, but it can be recomputed from the required
elements and omitting it saves on space.
+------+-------+-------+--------+-----------------------------------+ +-------+----------+-------+------------------------------------+
| name | key | value | type | description | | name | key type | value | description |
| | type | | | | +-------+----------+-------+------------------------------------+
+------+-------+-------+--------+-----------------------------------+ | P-256 | EC2 | 1 | NIST P-256 also known as secp256r1 |
| crv | 1 | -1 | int / | EC Curve identifier - Taken from | | | | | |
| | | | tstr | the COSE General Registry | | P-384 | EC2 | 2 | NIST P-384 also known as secp384r1 |
| | | | | | | | | | |
| x | 1 | -2 | bstr | X Coordinate | | P-521 | EC2 | 3 | NIST P-521 also known as secp521r1 |
| | | | | | +-------+----------+-------+------------------------------------+
| d | 1 | -4 | bstr | Private key |
+------+-------+-------+--------+-----------------------------------+
Table 22: EC Key Parameters Table 19: EC Curves
13.1.2. Double Coordinate Curves 13.1.1. Double Coordinate Curves
The traditional way of sending EC curves has been to send either both The traditional way of sending EC curves has been to send either both
the x and y coordinates, or the x coordinate and a sign bit for the y the x and y coordinates, or the x coordinate and a sign bit for the y
coordinate. The latter encoding has not been recommend in the IETF coordinate. The latter encoding has not been recommended in the IETF
due to potential IPR issues with Certicom. However, for operations due to potential IPR issues. However, for operations in constrained
in constrained environments, the ability to shrink a message by not environments, the ability to shrink a message by not sending the y
sending the y coordinate is potentially useful. coordinate is potentially useful.
For EC keys with both coordinates, the 'kty' member is set to 2 For EC keys with both coordinates, the 'kty' member is set to 2
(EC2). The key parameters defined in this section are summarized in (EC2). The key parameters defined in this section are summarized in
Table 23. The members that are defined for this key type are: Table 20. The members that are defined for this key type are:
crv contains an identifier of the curve to be used with the key. crv contains an identifier of the curve to be used with the key.
The curves defined in this document for this key type can be found The curves defined in this document for this key type can be found
in Table 21. Other curves may be registered in the future and in Table 19. Other curves may be registered in the future and
private curves can be used as well. private curves can be used as well.
x contains the x coordinate for the EC point. The integer is x contains the x coordinate for the EC point. The integer is
converted to an octet string as defined in [SEC1]. Zero octets converted to an octet string as defined in [SEC1]. Zero octets
MUST NOT be removed from the front of the octet string. [CREF14] MUST NOT be removed from the front of the octet string.
y contains either the sign bit or the value of y coordinate for the y contains either the sign bit or the value of y coordinate for the
EC point. For the value, the integer is converted to an octet EC point. For the value, the integer is converted to an octet
string as defined in [SEC1]. Zero octets MUST NOT be removed from string as defined in [SEC1]. Zero octets MUST NOT be removed from
the front of the octet string. For the sign bit, the value is the front of the octet string. For the sign bit, the value is
true if the value of y is positive. true if the value of y is positive.
d contains the private key. d contains the private key.
For public keys, it is REQUIRED that 'crv', 'x' and 'y' be present in For public keys, it is REQUIRED that 'crv', 'x' and 'y' be present in
skipping to change at page 59, line 49 skipping to change at page 55, line 43
| | | | tstr | the COSE General Registry | | | | | tstr | the COSE General Registry |
| | | | | | | | | | | |
| x | 2 | -2 | bstr | X Coordinate | | x | 2 | -2 | bstr | X Coordinate |
| | | | | | | | | | | |
| y | 2 | -3 | bstr / | Y Coordinate | | y | 2 | -3 | bstr / | Y Coordinate |
| | | | bool | | | | | | bool | |
| | | | | | | | | | | |
| d | 2 | -4 | bstr | Private key | | d | 2 | -4 | bstr | Private key |
+------+-------+-------+---------+----------------------------------+ +------+-------+-------+---------+----------------------------------+
Table 23: EC Key Parameters Table 20: EC Key Parameters
13.2. RSA Keys
This document defines a key structure for both the public and private
halves of RSA keys. Together, an RSA public key and an RSA private
key form an RSA key pair. [CREF15]
The document also provides support for the so-called "multi-prime"
RSA where the modulus may have more than two prime factors. The
benefit of multi-prime RSA is lower computational cost for the
decryption and signature primitives. For a discussion on how multi-
prime affects the security of RSA crypto-systems, the reader is
referred to [MultiPrimeRSA].
This document follows the naming convention of [RFC3447] for the
naming of the fields of an RSA public or private key. The table
Table 24 provides a summary of the label values and the types
associated with each of those labels. The requirements for fields
for RSA keys are as follows:
o For all keys, 'kty' MUST be present and MUST have a value of 3.
o For public keys, the fields 'n' and 'e' MUST be present. All
other fields defined in Table 24 MUST be absent.
o For private keys with two primes, the fields 'other', 'r_i', 'd_i'
and 't_i' MUST be absent, all other fields MUST be present.
o For private keys with more than two primes, all fields MUST be
present. For the third to nth primes, each of the primes is
represented as a map containing the fields 'r_i', 'd_i' and 't_i'.
The field 'other' is an array of those maps.
+-------+----------+-------+-------+--------------------------------+
| name | key type | value | type | description |
+-------+----------+-------+-------+--------------------------------+
| n | 3 | -1 | bstr | Modulus Parameter |
| | | | | |
| e | 3 | -2 | int | Exponent Parameter |
| | | | | |
| d | 3 | -3 | bstr | Private Exponent Parameter |
| | | | | |
| p | 3 | -4 | bstr | First Prime Factor |
| | | | | |
| q | 3 | -5 | bstr | Second Prime Factor |
| | | | | |
| dP | 3 | -6 | bstr | First Factor CRT Exponent |
| | | | | |
| dQ | 3 | -7 | bstr | Second Factor CRT Exponent |
| | | | | |
| qInv | 3 | -8 | bstr | First CRT Coefficient |
| | | | | |
| other | 3 | -9 | array | Other Primes Info |
| | | | | |
| r_i | 3 | -10 | bstr | i-th factor, Prime Factor |
| | | | | |
| d_i | 3 | -11 | bstr | i-th factor, Factor CRT |
| | | | | Exponent |
| | | | | |
| t_i | 3 | -12 | bstr | i-th factor, Factor CRT |
| | | | | Coefficient |
+-------+----------+-------+-------+--------------------------------+
Table 24: RSA Key Parameters
13.3. Symmetric Keys 13.2. Symmetric Keys
Occasionally it is required that a symmetric key be transported Occasionally it is required that a symmetric key be transported
between entities. This key structure allows for that to happen. between entities. This key structure allows for that to happen.
For symmetric keys, the 'kty' member is set to 3 (Symmetric). The For symmetric keys, the 'kty' member is set to 3 (Symmetric). The
member that is defined for this key type is: member that is defined for this key type is:
k contains the value of the key. k contains the value of the key.
This key structure contains only private key information, care must This key structure contains only private key information, care must
be taken that it is never transmitted accidentally. For public keys, be taken that it is never transmitted accidentally. For public keys,
there are no required fields. For private keys, it is REQUIRED that there are no required fields. For private keys, it is REQUIRED that
'k' be present in the structure. 'k' be present in the structure.
+------+----------+-------+------+-------------+ +------+----------+-------+------+-------------+
| name | key type | value | type | description | | name | key type | value | type | description |
+------+----------+-------+------+-------------+ +------+----------+-------+------+-------------+
| k | 4 | -1 | bstr | Key Value | | k | 4 | -1 | bstr | Key Value |
+------+----------+-------+------+-------------+ +------+----------+-------+------+-------------+
Table 25: Symmetric Key Parameters Table 21: Symmetric Key Parameters
14. CBOR Encoder Restrictions 14. CBOR Encoder Restrictions
There as been an attempt to limit the number of places where the There has been an attempt to limit the number of places where the
document needs to impose restrictions on how the CBOR Encoder needs document needs to impose restrictions on how the CBOR Encoder needs
to work. We have managed to narrow it down to the following to work. We have managed to narrow it down to the following
restrictions: restrictions:
o The restriction applies to the encoding the Sig_structure, the o The restriction applies to the encoding the Sig_structure, the
Enc_structure, and the MAC_structure. Enc_structure, and the MAC_structure.
o The rules for Canonical CBOR (Section 3.9 of RFC 7049) MUST be o The rules for Canonical CBOR (Section 3.9 of RFC 7049) MUST be
used in these locations. The main rule that needs to be enforced used in these locations. The main rule that needs to be enforced
is that all lengths in these structures MUST be encoded such that is that all lengths in these structures MUST be encoded such that
they are encoded using definite lengths and the minimum length they are encoded using definite lengths and the minimum length
encoding is used. encoding is used.
o All parsers used SHOULD fail on both parsing and generation if the o All parsers used SHOULD fail on both parsing and generation if the
same label is used twice as a key for the same map. same label is used twice as a key for the same map.
15. IANA Considerations 15. IANA Considerations
15.1. CBOR Tag assignment 15.1. CBOR Tag assignment
It is requested that IANA assign a new tag from the "Concise Binary It is requested that IANA assign the following tags from the "Concise
Object Representation (CBOR) Tags" registry. It is requested that Binary Object Representation (CBOR) Tags" registry. It is requested
the tag be assigned in the 0 to 23 value range. that the tags be assigned in the 24 to 255 value range.
Tag Value: TBD1
Data Item: COSE_Msg The tags to be assigned are:
Semantics: COSE security message. +-----------+-----------------------+-------------------------------+
| Tag Value | Data Item | Semantics |
+-----------+-----------------------+-------------------------------+
| TBD1 | COSE_Sign | COSE Signed Data Object |
| | | |
| TBD2 | COSE_enveloped | COSE Enveloped Data Object |
| | | |
| TBD3 | COSE_encryptData | COSE Encrypted Data Object |
| | | |
| TBD4 | COSE_Mac | COSE Mac-ed Data Object |
| | | |
| TBD5 | COSE_Key, COSE_KeySet | COSE Key or COSE Key Set |
| | | Object |
+-----------+-----------------------+-------------------------------+
15.2. COSE Header Parameter Registry 15.2. COSE Header Parameter Registry
It is requested that IANA create a new registry entitled "COSE Header It is requested that IANA create a new registry entitled "COSE Header
Parameters". Parameters".
The columns of the registry are: The columns of the registry are:
name The name is present to make it easier to refer to and discuss name The name is present to make it easier to refer to and discuss
the registration entry. The value is not used in the protocol. the registration entry. The value is not used in the protocol.
skipping to change at page 64, line 19 skipping to change at page 58, line 40
label. label.
value registry This contains a pointer to the registry used to value registry This contains a pointer to the registry used to
contain values where the set is limited. contain values where the set is limited.
description This contains a brief description of the header field. description This contains a brief description of the header field.
specification This contains a pointer to the specification defining specification This contains a pointer to the specification defining
the header field (where public). the header field (where public).
The initial contents of the registry can be found in: Table 12, The initial contents of the registry can be found in: Table 11,
Table 13, Table 19. The specification column for all rows in that Table 12, Table 17. The specification column for all rows in that
table should be this document. table should be this document.
15.4. COSE Algorithm Registry 15.4. COSE Algorithm Registry
It is requested that IANA create a new registry entitled "COSE It is requested that IANA create a new registry entitled "COSE
Algorithm Registry". Algorithm Registry".
The columns of the registry are: The columns of the registry are:
value The value to be used to identify this algorithm. Algorithm value The value to be used to identify this algorithm. Algorithm
skipping to change at page 64, line 48 skipping to change at page 59, line 20
range -1 to -65536 are delegated to the "COSE Header Algorithm range -1 to -65536 are delegated to the "COSE Header Algorithm
Label" registry. Integer values beyond -65536 are marked as Label" registry. Integer values beyond -65536 are marked as
private use. private use.
description A short description of the algorithm. description A short description of the algorithm.
specification A document where the algorithm is defined (if publicly specification A document where the algorithm is defined (if publicly
available). available).
The initial contents of the registry can be found in the following: The initial contents of the registry can be found in the following:
Table 9, Table 8, Table 10, Table 4, Table 5, Table 6, Table 7, Table 8, Table 7, Table 9, Table 4, Table 5, Table 6, Table 13,
Table 14, Table 15, Table 16, Table 17, Table 18. The specification Table 14, Table 15, Table 16. The specification column for all rows
column for all rows in that table should be this document. in that table should be this document.
15.5. COSE Key Common Parameter Registry 15.5. COSE Key Common Parameter Registry
It is requested that IANA create a new registry entitled "COSE Key It is requested that IANA create a new registry entitled "COSE Key
Common Parameter" Registry. Common Parameter" Registry.
The columns of the registry are: The columns of the registry are:
name This is a descriptive name that enables easier reference to the name This is a descriptive name that enables easier reference to the
item. It is not used in the encoding. item. It is not used in the encoding.
skipping to change at page 66, line 19 skipping to change at page 60, line 36
range of values is from -256 to -1. Labels are expected to be range of values is from -256 to -1. Labels are expected to be
reused for different keys. reused for different keys.
CBOR type This field contains the CBOR type for the field CBOR type This field contains the CBOR type for the field
description This field contains a brief description for the field description This field contains a brief description for the field
specification This contains a pointer to the public specification specification This contains a pointer to the public specification
for the field if one exists for the field if one exists
This registry will be initially populated by the values in Table 22, This registry will be initially populated by the values in Table 20,
Table 23, Table 24, and Table 25. The specification column for all and Table 21. The specification column for all of these entries will
of these entries will be this document. be this document.
15.7. COSE Elliptic Curve Registry 15.7. COSE Elliptic Curve Registry
It is requested that IANA create a new registry "COSE Elliptic Curve It is requested that IANA create a new registry "COSE Elliptic Curve
Parameters". Parameters".
The columns of the table are: The columns of the table are:
name This is a descriptive name that enables easier reference to the name This is a descriptive name that enables easier reference to the
item. It is not used in the encoding. item. It is not used in the encoding.
value This is the value used to identify the curve. These values value This is the value used to identify the curve. These values
MUST be unique. The integer values from -256 to 255 are MUST be unique. The integer values from -256 to 255 are
designated as Standards Track Document Required. The the integer designated as Standards Track Document Required. The integer
values from 256 to 65535 and -65536 to -257 are designated as values from 256 to 65535 and -65536 to -257 are designated as
Specification Required. Integer values over 65535 are designated Specification Required. Integer values over 65535 are designated
as first come first serve. Integer values less than -65536 are as first come first serve. Integer values less than -65536 are
marked as private use. marked as private use.
key type This designates the key type(s) that can be used with this key type This designates the key type(s) that can be used with this
curve. curve.
description This field contains a brief description of the curve. description This field contains a brief description of the curve.
specification This contains a pointer to the public specification specification This contains a pointer to the public specification
for the curve if one exists. for the curve if one exists.
This registry will be initially populated by the values in Table 20. This registry will be initially populated by the values in Table 18.
The specification column for all of these entries will be this The specification column for all of these entries will be this
document. document.
15.8. Media Type Registration 15.8. Media Type Registrations
15.8.1. COSE Security Message 15.8.1. COSE Security Message
This section registers the "application/cose" and "application/ This section registers the "application/cose" and "application/
cose+cbor" media types in the "Media Types" registry. [CREF16] These cose+cbor" media types in the "Media Types" registry. [CREF8] These
media types are used to indicate that the content is a COSE_MSG. media types are used to indicate that the content is a COSE_MSG.
[CREF9]
Type name: application Type name: application
Subtype name: cose Subtype name: cose
Required parameters: N/A Required parameters: N/A
Optional parameters: N/A Optional parameters: N/A
Encoding considerations: binary Encoding considerations: binary
skipping to change at page 70, line 37 skipping to change at page 65, line 4
* Magic number(s): N/A * Magic number(s): N/A
* File extension(s): cbor * File extension(s): cbor
* Macintosh file type code(s): N/A * Macintosh file type code(s): N/A
Person & email address to contact for further information: Person & email address to contact for further information:
iesg@ietf.org iesg@ietf.org
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: Jim Schaad, ietf@augustcellars.com Author: Jim Schaad, ietf@augustcellars.com
Change Controller: IESG Change Controller: IESG
Provisional registration? No Provisional registration? No
15.9. CoAP Content Format Registrations
This section registers a set of content formats for CoAP. ID
assignment in the 24-255 range requested.
+--------------------------+----------+-------+-----------------+
| Media Type | Encoding | ID | Reference |
+--------------------------+----------+-------+-----------------+
| application/cose | | TBD10 | [This Document] |
| | | | |
| application/cose-key | | TBD11 | [This Document] |
| | | | |
| application/cose-key-set | | TBD12 | [This Document |
+--------------------------+----------+-------+-----------------+
16. Security Considerations 16. Security Considerations
There are security considerations: There are security considerations:
1. Protect private keys 1. Protect private keys
2. MAC messages with more than one recipient means one cannot figure 2. MAC messages with more than one recipient means one cannot figure
out who sent the message out who sent the message
3. Use of direct key with other recipient structures hands the key 3. Use of direct key with other recipient structures hands the key
to other recipients. to other recipients.
4. Use of direct ECDH direct encryption is easy for people to leak 4. Use of direct ECDH direct encryption is easy for people to leak
information on if there are other recipients in the message. information on if there are other recipients in the message.
5. Considerations about protected vs unprotected header fields. 5. Considerations about protected vs unprotected header fields.
skipping to change at page 71, line 16 skipping to change at page 65, line 45
3. Use of direct key with other recipient structures hands the key 3. Use of direct key with other recipient structures hands the key
to other recipients. to other recipients.
4. Use of direct ECDH direct encryption is easy for people to leak 4. Use of direct ECDH direct encryption is easy for people to leak
information on if there are other recipients in the message. information on if there are other recipients in the message.
5. Considerations about protected vs unprotected header fields. 5. Considerations about protected vs unprotected header fields.
6. Need to verify that: 1) the kty field of the key matches the key 6. Need to verify that: 1) the kty field of the key matches the key
and algorithm being used. 2) that the kty field needs to be and algorithm being used. 2) the kty field needs to be included
included in the trust decision as well as the other key fields. in the trust decision as well as the other key fields. 3) the
3) that the algorithm be included in the trust decision. algorithm be included in the trust decision.
17. References 17. References
17.1. Normative References 17.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, October 2013. Representation (CBOR)", RFC 7049, October 2013.
skipping to change at page 71, line 45 skipping to change at page 66, line 30
[DSS] U.S. National Institute of Standards and Technology, [DSS] U.S. National Institute of Standards and Technology,
"Digital Signature Standard (DSS)", July 2013. "Digital Signature Standard (DSS)", July 2013.
[I-D.greevenbosch-appsawg-cbor-cddl] [I-D.greevenbosch-appsawg-cbor-cddl]
Vigano, C., Birkholz, H., and R. Sun, "CBOR data Vigano, C., Birkholz, H., and R. Sun, "CBOR data
definition language: a notational convention to express definition language: a notational convention to express
CBOR data structures.", draft-greevenbosch-appsawg-cbor- CBOR data structures.", draft-greevenbosch-appsawg-cbor-
cddl-05 (work in progress), March 2015. cddl-05 (work in progress), March 2015.
[I-D.irtf-cfrg-curves]
Langley, A. and R. Salz, "Elliptic Curves for Security",
draft-irtf-cfrg-curves-02 (work in progress), March 2015.
[MAC] NiST, N., "FIPS PUB 113: Computer Data Authentication", [MAC] NiST, N., "FIPS PUB 113: Computer Data Authentication",
May 1985. May 1985.
[MultiPrimeRSA] [MultiPrimeRSA]
Hinek, M. and D. Cheriton, "On the Security of Multi-prime Hinek, M. and D. Cheriton, "On the Security of Multi-prime
RSA", June 2006. RSA", June 2006.
[PVSig] Brown, D. and D. Johnson, "Formal Security Proofs for a [PVSig] Brown, D. and D. Johnson, "Formal Security Proofs for a
Signature Scheme with Partial Message Recover", February Signature Scheme with Partial Message Recover", February
2000. 2000.
skipping to change at page 74, line 20 skipping to change at page 68, line 48
Special Publication 800-56A: Recommendation for Pair-Wise Special Publication 800-56A: Recommendation for Pair-Wise
Key Establishment Schemes Using Discrete Logarithm Key Establishment Schemes Using Discrete Logarithm
Cryptography", May 2013. Cryptography", May 2013.
Appendix A. CDDL Grammar Appendix A. CDDL Grammar
For people who prefer using a formal language to describe the syntax For people who prefer using a formal language to describe the syntax
of the CBOR, in this section a CDDL grammar is given that corresponds of the CBOR, in this section a CDDL grammar is given that corresponds
to [I-D.greevenbosch-appsawg-cbor-cddl]. This grammar is to [I-D.greevenbosch-appsawg-cbor-cddl]. This grammar is
informational, in the event of differences between this grammar and informational, in the event of differences between this grammar and
the prose, the prose is considered to be authorative. the prose, the prose is considered to be authoritative.
The collected CDDL can be extracted from the XML version of this The collected CDDL can be extracted from the XML version of this
document via the following XPath expression below. (Depending on the document via the following XPath expression below. (Depending on the
XPath evaluator one is using, it may be necessary to deal with > XPath evaluator one is using, it may be necessary to deal with >
as an entity.) as an entity.)
//artwork[@type='CDDL']/text() //artwork[@type='CDDL']/text()
Appendix B. Three Levels of Recipient Information Appendix B. Three Levels of Recipient Information
skipping to change at page 75, line 13 skipping to change at page 69, line 41
o Level 0: Has a content encrypted with AES-GCM using a 128-bit key. o Level 0: Has a content encrypted with AES-GCM using a 128-bit key.
o Level 1: Uses the AES Key wrap algorithm with a 128-bit key. o Level 1: Uses the AES Key wrap algorithm with a 128-bit key.
o Level 2: Uses ECDH Ephemeral-Static direct to generate the level 1 o Level 2: Uses ECDH Ephemeral-Static direct to generate the level 1
key. key.
In effect this example is a decomposed version of using the ECDH- In effect this example is a decomposed version of using the ECDH-
ES+A128KW algorithm. ES+A128KW algorithm.
Size of binary file is 214 bytes Size of binary file is 216 bytes
998( [
[
2,
h'a10101', h'a10101',
{ {
5: h'02d1f7e6f26c43d4868d87ce' 5: h'02d1f7e6f26c43d4868d87ce'
}, },
h'64f84d913ba60a76070a9a48f26e97e863e285295a44320878caceb0763a3 h'64f84d913ba60a76070a9a48f26e97e863e285295a44320878caceb0763a3
34806857c67', 34806857c67',
[ [
[ [
h'', h'',
{ {
skipping to change at page 75, line 51 skipping to change at page 70, line 39
a55a600b21233e86e68', a55a600b21233e86e68',
-3: h'1a2cf118b9ee6895c8f415b686d4ca1cef362d4a7630a -3: h'1a2cf118b9ee6895c8f415b686d4ca1cef362d4a7630a
31ef6019c0c56d33de0' 31ef6019c0c56d33de0'
} }
}, },
h'' h''
] ]
] ]
] ]
] ]
] ])
Appendix C. Examples Appendix C. Examples
The examples can be found at https://github.com/cose-wg/Examples. The examples can be found at https://github.com/cose-wg/Examples.
The file names in each section correspond the the same file names in The file names in each section correspond the same file names in the
the repository. I am currently still in the process of getting the repository. I am currently still in the process of getting the
examples up there along with some control information for people to examples up there along with some control information for people to
be able to check and reproduce the examples. be able to check and reproduce the examples.
Examples may have some features that are in questions but not yet Examples may have some features that are in questions but not yet
incorporated in the document. incorporated in the document.
To make it easier to read, the examples are presented using the To make it easier to read, the examples are presented using the
CBOR's diagnostic notation rather than a binary dump. A ruby based CBOR's diagnostic notation rather than a binary dump. A ruby based
tool exists to convert between a number of formats. This tool can be tool exists to convert between a number of formats. This tool can be
installed with the command line: installed with the command line:
gem install cbor-diag gem install cbor-diag
The diagnostic notation can be converted into binary files using the The diagnostic notation can be converted into binary files using the
following command line: following command line:
diag2cbor < inputfile > outputfile diag2cbor < inputfile > outputfile
The examples can be extracted from the XML version of this docuent The examples can be extracted from the XML version of this document
via an XPath expression as all of the artwork is tagged with the via an XPath expression as all of the artwork is tagged with the
attribute type='CBORdiag'. attribute type='CBORdiag'.
C.1. Examples of MAC messages C.1. Examples of MAC messages
C.1.1. Shared Secret Direct MAC C.1.1. Shared Secret Direct MAC
This example users the following: This example users the following:
o MAC: AES-CMAC, 256-bit key, trucated to 64 bits o MAC: AES-CMAC, 256-bit key, truncated to 64 bits
o Recipient class: direct shared secret o Recipient class: direct shared secret
o File name: Mac-04 o File name: Mac-04
Size of binary file is 71 bytes Size of binary file is 73 bytes
996( [
[
3,
h'a1016f4145532d434d41432d3235362f3634', h'a1016f4145532d434d41432d3235362f3634',
{ {
}, },
h'546869732069732074686520636f6e74656e742e', h'546869732069732074686520636f6e74656e742e',
h'd9afa663dd740848', h'd9afa663dd740848',
[ [
[ [
h'', h'',
{ {
1: -6, 1: -6,
4: h'6f75722d736563726574' 4: h'6f75722d736563726574'
}, },
h'' h''
] ]
] ]
] ])
C.1.2. ECDH Direct MAC C.1.2. ECDH Direct MAC
This example uses the following: This example uses the following:
o MAC: HMAC w/SHA-256, 256-bit key o MAC: HMAC w/SHA-256, 256-bit key
o Recipient class: ECDH key agreement, two static keys, HKDF w/ o Recipient class: ECDH key agreement, two static keys, HKDF w/
context structure context structure
Size of binary file is 215 bytes Size of binary file is 217 bytes
996( [
[
3,
h'a10104', h'a10104',
{ {
}, },
h'546869732069732074686520636f6e74656e742e', h'546869732069732074686520636f6e74656e742e',
h'2ba937ca03d76c3dbad30cfcbaeef586f9c0f9ba616ad67e9205d38576ad9 h'2ba937ca03d76c3dbad30cfcbaeef586f9c0f9ba616ad67e9205d38576ad9
930', 930',
[ [
[ [
h'', h'',
{ {
skipping to change at page 78, line 29 skipping to change at page 73, line 27
6e642e6578616d706c65', 6e642e6578616d706c65',
-3: h'706572656772696e2e746f6f6b407475636b626f726f7567682 -3: h'706572656772696e2e746f6f6b407475636b626f726f7567682
e6578616d706c65', e6578616d706c65',
"apu": h'4d8553e7e74f3c6a3a9dd3ef286a8195cbf8a23d19558ccf "apu": h'4d8553e7e74f3c6a3a9dd3ef286a8195cbf8a23d19558ccf
ec7d34b824f42d92bd06bd2c7f0271f0214e141fb779ae2856abf585a58368b01 ec7d34b824f42d92bd06bd2c7f0271f0214e141fb779ae2856abf585a58368b01
7e7f2a9e5ce4db5' 7e7f2a9e5ce4db5'
}, },
h'' h''
] ]
] ]
] ])
C.1.3. Wrapped MAC C.1.3. Wrapped MAC
This example uses the following: This example uses the following:
o MAC: AES-MAC, 128-bit key, truncated to 64 bits o MAC: AES-MAC, 128-bit key, truncated to 64 bits
o Recipient class: AES keywrap w/ a pre-shared 256-bit key o Recipient class: AES keywrap w/ a pre-shared 256-bit key
Size of binary file is 122 bytes Size of binary file is 124 bytes
996( [
[
3,
h'a1016e4145532d3132382d4d41432d3634', h'a1016e4145532d3132382d4d41432d3634',
{ {
}, },
h'546869732069732074686520636f6e74656e742e', h'546869732069732074686520636f6e74656e742e',
h'6d1fa77b2dd9146a', h'6d1fa77b2dd9146a',
[ [
[ [
h'', h'',
{ {
1: -5, 1: -5,
4: h'30313863306165352d346439622d343731622d626664362d6565 4: h'30313863306165352d346439622d343731622d626664362d6565
66333134626337303337' 66333134626337303337'
}, },
h'711ab0dc2fc4585dce27effa6781c8093eba906f227b6eb0' h'711ab0dc2fc4585dce27effa6781c8093eba906f227b6eb0'
] ]
] ]
] ])
C.1.4. Multi-recipient MAC message C.1.4. Multi-recipient MAC message
This example uses the following: This example uses the following:
o MAC: HMAC w/ SHA-256, 128-bit key o MAC: HMAC w/ SHA-256, 128-bit key
o Recipient class: Uses three different methods o Recipient class: Uses three different methods
1. ECDH Ephemeral-Static, Curve P-521, AES-Key Wrap w/ 128-bit 1. ECDH Ephemeral-Static, Curve P-521, AES-Key Wrap w/ 128-bit
key key
2. RSA-OAEP w/ SHA-256 2. AES-Key Wrap w/ 256-bit key
3. AES-Key Wrap w/ 256-bit key
Size of binary file is 670 bytes
[ Size of binary file is 374 bytes
3, 996( [
h'a10104', h'a10104',
{ {
}, },
h'546869732069732074686520636f6e74656e742e', h'546869732069732074686520636f6e74656e742e',
h'7aaa6e74546873061f0a7de21ff0c0658d401a68da738dd893748651983ce h'7aaa6e74546873061f0a7de21ff0c0658d401a68da738dd893748651983ce
1d0', 1d0',
[ [
[ [
h'', h'',
{ {
skipping to change at page 80, line 25 skipping to change at page 75, line 35
b44f22b9d1091ae8fc8ae40b687e5cfbe7ee6f8b47918a07bb04e9f5b1a51a334 b44f22b9d1091ae8fc8ae40b687e5cfbe7ee6f8b47918a07bb04e9f5b1a51a334
a16bc09777434113' a16bc09777434113'
} }
}, },
h'f20ad9c96134f3c6be4f75e7101c0ecc5efa071ff20a87fd1ac285109 h'f20ad9c96134f3c6be4f75e7101c0ecc5efa071ff20a87fd1ac285109
41ee0376573e2b384b56b99' 41ee0376573e2b384b56b99'
], ],
[ [
h'', h'',
{ {
1: -26,
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65'
},
h'46c4f88069b650909a891e84013614cd58a3668f88fa18f3852940a20
b35098591d3aacf91c125a2595cda7bee75a490579f0e2f20fd6bc956623bfde3
029c318f82c426dac3463b261c981ab18b72fe9409412e5c7f2d8f2b5abaf780d
f6a282db033b3a863fa957408b81741878f466dcc437006ca21407181a016ca60
8ca8208bd3c5a1ddc828531e30b89a67ec6bb97b0c3c3c92036c0cb84aa0f0ce8
c3e4a215d173bfa668f116ca9f1177505afb7629a9b0b5e096e81d37900e06f56
1a32b6bc993fc6d0cb5d4bb81b74e6ffb0958dac7227c2eb8856303d989f93b4a
051830706a4c44e8314ec846022eab727e16ada628f12ee7978855550249ccb58
'
],
[
h'',
{
1: -5, 1: -5,
4: h'30313863306165352d346439622d343731622d626664362d6565 4: h'30313863306165352d346439622d343731622d626664362d6565
66333134626337303337' 66333134626337303337'
}, },
h'0b2c7cfce04e98276342d6476a7723c090dfdd15f9a518e7736549e99 h'0b2c7cfce04e98276342d6476a7723c090dfdd15f9a518e7736549e99
8370695e6d6a83b4ae507bb' 8370695e6d6a83b4ae507bb'
] ]
] ]
] ])
C.2. Examples of Encrypted Messages C.2. Examples of Encrypted Messages
C.2.1. Direct ECDH C.2.1. Direct ECDH
This example uses the following: This example uses the following:
o CEK: AES-GCM w/ 128-bit key o CEK: AES-GCM w/ 128-bit key
o Recipient class: ECDH Ephemeral-Static, Curve P-256 o Recipient class: ECDH Ephemeral-Static, Curve P-256
Size of binary file is 182 bytes Size of binary file is 184 bytes
[ 998( [
2,
h'a10101', h'a10101',
{ {
5: h'c9cf4df2fe6c632bf7886413' 5: h'c9cf4df2fe6c632bf7886413'
}, },
h'45fce2814311024d3a479e7d3eed063850f3f0b9f3f948677e3ae9869bcf9 h'45fce2814311024d3a479e7d3eed063850f3f0b9f3f948677e3ae9869bcf9
ff4e1763812', ff4e1763812',
[ [
[ [
h'', h'',
{ {
skipping to change at page 81, line 44 skipping to change at page 76, line 34
-1: 1, -1: 1,
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf05 -2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf05
4e1c7b4d91d6280', 4e1c7b4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d -3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d
924b7e03bf822bb' 924b7e03bf822bb'
} }
}, },
h'' h''
] ]
] ]
] ])
C.2.2. Direct plus Key Derivation C.2.2. Direct plus Key Derivation
This example uses the following: This example uses the following:
o CEK: AES-CCM w/128-bit key, trucate the tag to 64-bits o CEK: AES-CCM w/128-bit key, truncate the tag to 64-bits
o Recipient class: Use HKDF on a shared secret with the following o Recipient class: Use HKDF on a shared secret with the following
implicit fields as part of the context. implicit fields as part of the context.
* APU identity: "lighting-client" * APU identity: "lighting-client"
* APV identity: "lighting-server" * APV identity: "lighting-server"
* Supplimentary Public Other: "Encryption Example 02" * Supplementary Public Other: "Encryption Example 02"
Size of binary file is 95 bytes
[ Size of binary file is 97 bytes
2, 998( [
h'a1010a', h'a1010a',
{ {
5: h'89f52f65a1c580933b5261a7' 5: h'89f52f65a1c580933b5261a7'
}, },
h'7b9dcfa42c4e1d3182c402dc18ef8b5637de4fb62cf1dd156ea6e6e0', h'7b9dcfa42c4e1d3182c402dc18ef8b5637de4fb62cf1dd156ea6e6e0',
[ [
[ [
h'', h'',
{ {
1: "dir+kdf", 1: "dir+kdf",
4: h'6f75722d736563726574', 4: h'6f75722d736563726574',
-20: h'61616262636364646565666667676868' -20: h'61616262636364646565666667676868'
}, },
h'' h''
] ]
] ]
] ])
C.3. Examples of Signed Message C.3. Examples of Signed Message
C.3.1. Single Signature C.3.1. Single Signature
This example uses the following: This example uses the following:
o Signature Algorithm: RSA-PSS w/ SHA-384, MGF-1 o Signature Algorithm: ECDSA w/ SHA-256, Curve P-256-1
Size of binary file is 330 bytes Size of binary file is 105 bytes
[ 999( [
1,
h'', h'',
{ {
}, },
h'546869732069732074686520636f6e74656e742e', h'546869732069732074686520636f6e74656e742e',
[ [
[ [
h'a20165505333383404581e62696c626f2e62616767696e7340686f626 h'a10126',
269746f6e2e6578616d706c65',
{ {
4: h'3131'
}, },
h'6d9d88a90ef4d6d7c0079fb11a33c855e2274c773f358df43b68f7873 h'4358e9e92b46d45134548b6e3b4eae3d2f801bce85236c7aab42968ad
eeda210692a61d70cd6a24ba0e3d82e359384be09faafea496bb0ed16f02091c4 8e3e92400873ed761735222a6d1f442c4bb3a3151946b16900048572455e65451
8c02f33574edab5b3e334bae68d19580021327cc131fbee38eb0b28289dbce118 d89aaba7'
3f9067891b17fe752674b80437da02e9928ab7a155fef707b11d2bd38a71f224f
53170480116d96cc3f7266487b268679a13cdedffa93252a550371acc19971369
b58039056b308cc4e158bebe7c55db7874442d4321fd27f17dbb820ef19f43dcc
16cd50ccdd1b7dfd7cdde239a9245af41d949cdbbf1337ca254af20eeb167a62d
a5a51c83899c6f6e7c7e01dc3db21a250092a69fc635b74a2e54f5c98cb955d83
'
] ]
] ]
] ])
C.3.2. Multiple Signers C.3.2. Multiple Signers
This example uses the following: This example uses the following:
o Signature Algorithm: RSA-PSS w/ SHA-256, MGF-1 o Signature Algorithm: ECDSA w/ SHA-256, Curve P-256-1
o Signature Algorithm: ECDSA w/ SHA-512, Curve P-521 o Signature Algorithm: ECDSA w/ SHA-512, Curve P-521
Size of binary file is 496 bytes Size of binary file is 277 bytes
[ 999( [
1,
h'', h'',
{ {
}, },
h'546869732069732074686520636f6e74656e742e', h'546869732069732074686520636f6e74656e742e',
[ [
[ [
h'a1013819', h'a10126',
{ {
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861 4: h'3131'
6d706c65'
}, },
h'0ee972d931c7ab906e4bb71b80da0cc99c104fa53ebbf1f2cf7b668b9 h'0dc1c5e62719d8f3cce1468b7c881eee6a8088b46bf836ae956dd38fe
3d766d3d2da28299f074675bb0db3cd0792ba83050c23c96795d58f9c7d68f66a 931991900823ea760648f2425b96c39e23ddc4b7faed56d4a9bd0f3752cfdc628
bbb8f35af8a0b5df369517b6db85e2cb62d852b666bc135c9022e46b538f78c26 254ed0f2'
adc2668963e74a019de718254385bb9cb137926ad6a88d1ff70043f85e555fb57
84107ce6e9de7c89c4fbadf8eca363a35f415f7a23523a8331b1aa2dfbac59a06
3e4357bde8e53fe34195d59bcda37d2c604804fffe60362e81476436aaa677129
f34b26639fc41b8e758e5edf273079c61b30130f0f83c57aa6856347e2556f718
eaf79a1fee1397a4f0b16b1b34db946eaaff10c793e5d1e681cb21c4fd20c5fdf
'
], ],
[ [
h'', h'',
{ {
1: -9, 1: -9,
4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861 4: h'62696c626f2e62616767696e7340686f626269746f6e2e657861
6d706c65' 6d706c65'
}, },
h'0118eaa7d62778b5a9525a583f06b115d80cd246bc930f0c2850588ee h'012ce5b1dfe8b5aa6eaa09a54c58a84ad0900e4fdf2759ec22d1c861c
c85186b427026e096a076bfab738215f354be59f57643a7f6b2c92535cf3c37ee ccd75c7e1c4025a2da35e512fc2874d6ac8fd862d09ad07ed2deac297b897561e
2746a908ab1dcc673a63f327d9eff852b874f7a98b6638c7054fdeeaa3dce6542 04a8d42476011eb209c016416b4247b4d1475c398d35c4ac24d1c9fadda7eefe2
4a21bd5dc728acedda7fcae6df6fc3298ff51ac911603a0f26d066935dccb85ea 857e25a500d29aea539e58e8ca7737fe450d4e87ed3f78e637c12bbd213e78ba8
eb0ae6d0e6' 3a55f7e89934'
] ]
] ]
] ])
C.4. COSE Keys C.4. COSE Keys
C.4.1. Public Keys C.4.1. Public Keys
This is an example of a COSE Key set. This example includes the This is an example of a COSE Key set. This example includes the
public keys for all of the previous examples. public keys for all of the previous examples.
In order the keys are: In order the keys are:
o An EC key with a kid of "meriadoc.brandybuck@buckland.example" o An EC key with a kid of "meriadoc.brandybuck@buckland.example"
o An EC key with a kid of "peregrin.took@tuckborough.example" o An EC key with a kid of "peregrin.took@tuckborough.example"
o An EC key with a kid of "bilbo.baggins@hobbiton.example" o An EC key with a kid of "bilbo.baggins@hobbiton.example"
o An RSA key with a kid of "bilbo.baggins@hobbiton.example" o An EC key with a kid of "11"
Size of binary file is 703 bytes Size of binary file is 481 bytes
[ [
{ {
-1: 1, -1: 1,
-2: h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de4 -2: h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de4
39c08551d', 39c08551d',
-3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eec -3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eec
d0084d19c', d0084d19c',
1: 2, 1: 2,
2: h'6d65726961646f632e6272616e64796275636b406275636b6c616e64 2: h'6d65726961646f632e6272616e64796275636b406275636b6c616e64
2e6578616d706c65' 2e6578616d706c65'
}, },
{ {
-1: 1,
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf054e1c7b
4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d924b7e
03bf822bb',
1: 2,
2: h'706572656772696e2e746f6f6b407475636b626f726f7567682e6578
616d706c65'
},
{
-1: 3, -1: 3,
-2: h'0072992cb3ac08ecf3e5c63dedec0d51a8c1f79ef2f82f94f3c737b -2: h'0072992cb3ac08ecf3e5c63dedec0d51a8c1f79ef2f82f94f3c737b
f5de7986671eac625fe8257bbd0394644caaa3aaf8f27a4585fbbcad0f2457620 f5de7986671eac625fe8257bbd0394644caaa3aaf8f27a4585fbbcad0f2457620
085e5c8f42ad', 085e5c8f42ad',
-3: h'01dca6947bce88bc5790485ac97427342bc35f887d86d65a089377e -3: h'01dca6947bce88bc5790485ac97427342bc35f887d86d65a089377e
247e60baa55e4e8501e2ada5724ac51d6909008033ebc10ac999b9d7f5cc2519f 247e60baa55e4e8501e2ada5724ac51d6909008033ebc10ac999b9d7f5cc2519f
3fe1ea1d9475', 3fe1ea1d9475',
1: 2, 1: 2,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70 2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65' 6c65'
}, },
{ {
-2: h'9f810fb4038273d02591e4073f31d2b6001b82cedb4d92f050165d4 -1: 1,
7cfcab8a3c41cb778ac7553793f8ef975768d1a2374d8712564c3bcd77b9ea434 -2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf054e1c7b
544899407cff0099920a931a24c4414852ab29bdb0a95c0653f36c60e60bf90b6 4d91d6280',
258dda56f37047ba5c2d1d029af9c9d40bac7aa41c78a0dd1068add699e808fea -3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d924b7e
011ea1441d8a4f7bb4e97be39f55f1ddd44e9c4ba335159703d4d34b603e65147 03bf822bb',
a4f23d6d3c0996c75edee846a82d190ae10783c961cf0387aed2106d2d0555b6f 1: 2,
d937fad5535387e0ff72ffbe78941402b0b822ea2a74b6058c1dabf9b34a76cb6 2: h'706572656772696e2e746f6f6b407475636b626f726f7567682e6578
3b87faa2c6847b8e2837fff91186e6b1c14911cf989a89092a81ce601ddacd3f9 616d706c65'
cf', },
-1: h'010001', {
1: 3, -1: 1,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70 -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a8
6c65' 6d6a09eff',
-3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed2
8bbfc117e',
1: 2,
2: h'3131'
} }
] ]
C.4.2. Private Keys C.4.2. Private Keys
This is an example of a COSE Key set. This example includes the This is an example of a COSE Key set. This example includes the
private keys for all of the previous examples. private keys for all of the previous examples.
In order the keys are: In order the keys are:
skipping to change at page 86, line 34 skipping to change at page 81, line 23
o A shared-secret key with a kid of "our-secret" o A shared-secret key with a kid of "our-secret"
o An EC key with a kid of "peregrin.took@tuckborough.example" o An EC key with a kid of "peregrin.took@tuckborough.example"
o A shared-secret key with a kid of "018c0ae5-4d9b-471b- o A shared-secret key with a kid of "018c0ae5-4d9b-471b-
bfd6-eef314bc7037" bfd6-eef314bc7037"
o An EC key with a kid of "bilbo.baggins@hobbiton.example" o An EC key with a kid of "bilbo.baggins@hobbiton.example"
o An RSA key with a kid of "bilbo.baggins@hobbiton.example" o An EC key with a kid of "11"
Size of binary file is 1884 bytes Size of binary file is 782 bytes
[ [
{ {
1: 2, 1: 2,
2: h'6d65726961646f632e6272616e64796275636b406275636b6c616e64 2: h'6d65726961646f632e6272616e64796275636b406275636b6c616e64
2e6578616d706c65', 2e6578616d706c65',
-1: 1, -1: 1,
-2: h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de4 -2: h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de4
39c08551d', 39c08551d',
-3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eec -3: h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eec
skipping to change at page 87, line 11 skipping to change at page 81, line 48
40fa208cf' 40fa208cf'
}, },
{ {
1: 4, 1: 4,
2: h'6f75722d736563726574', 2: h'6f75722d736563726574',
-1: h'849b57219dae48de646d07dbb533566e976686457c1491be3a76dce -1: h'849b57219dae48de646d07dbb533566e976686457c1491be3a76dce
a6c427188' a6c427188'
}, },
{ {
1: 2, 1: 2,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65',
-1: 3,
-2: h'0072992cb3ac08ecf3e5c63dedec0d51a8c1f79ef2f82f94f3c737b
f5de7986671eac625fe8257bbd0394644caaa3aaf8f27a4585fbbcad0f2457620
085e5c8f42ad',
-3: h'01dca6947bce88bc5790485ac97427342bc35f887d86d65a089377e
247e60baa55e4e8501e2ada5724ac51d6909008033ebc10ac999b9d7f5cc2519f
3fe1ea1d9475',
-4: h'00085138ddabf5ca975f5860f91a08e91d6d5f9a76ad4018766a476
680b55cd339e8ab6c72b5facdb2a2a50ac25bd086647dd3e2e6e99e84ca2c3609
fdf177feb26d'
},
{
1: 2,
-1: 1, -1: 1,
2: h'706572656772696e2e746f6f6b407475636b626f726f7567682e6578 2: h'706572656772696e2e746f6f6b407475636b626f726f7567682e6578
616d706c65', 616d706c65',
-2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf054e1c7b -2: h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbfbf054e1c7b
4d91d6280', 4d91d6280',
-3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d924b7e -3: h'f01400b089867804b8e9fc96c3932161f1934f4223069170d924b7e
03bf822bb', 03bf822bb',
-4: h'02d1f7e6f26c43d4868d87ceb2353161740aacf1f7163647984b522 -4: h'02d1f7e6f26c43d4868d87ceb2353161740aacf1f7163647984b522
a848df1c3' a848df1c3'
}, },
{ {
1: 4, 1: 4,
2: h'30313863306165352d346439622d343731622d626664362d65656633 2: h'30313863306165352d346439622d343731622d626664362d65656633
3134626337303337', 3134626337303337',
-1: h'849b57219dae48de646d07dbb533566e976686457c1491be3a76dce -1: h'849b57219dae48de646d07dbb533566e976686457c1491be3a76dce
a6c427188' a6c427188'
}, },
{ {
1: 2, 1: 2,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70 2: h'3131',
6c65', -1: 1,
-1: 3, -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a8
-2: h'0072992cb3ac08ecf3e5c63dedec0d51a8c1f79ef2f82f94f3c737b 6d6a09eff',
f5de7986671eac625fe8257bbd0394644caaa3aaf8f27a4585fbbcad0f2457620 -3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed2
085e5c8f42ad', 8bbfc117e',
-3: h'01dca6947bce88bc5790485ac97427342bc35f887d86d65a089377e -4: h'57c92077664146e876760c9520d054aa93c3afb04e306705db60903
247e60baa55e4e8501e2ada5724ac51d6909008033ebc10ac999b9d7f5cc2519f 08507b4d3'
3fe1ea1d9475',
-4: h'00085138ddabf5ca975f5860f91a08e91d6d5f9a76ad4018766a476
680b55cd339e8ab6c72b5facdb2a2a50ac25bd086647dd3e2e6e99e84ca2c3609
fdf177feb26d'
},
{
1: 3,
2: h'62696c626f2e62616767696e7340686f626269746f6e2e6578616d70
6c65',
-2: h'9f810fb4038273d02591e4073f31d2b6001b82cedb4d92f050165d4
7cfcab8a3c41cb778ac7553793f8ef975768d1a2374d8712564c3bcd77b9ea434
544899407cff0099920a931a24c4414852ab29bdb0a95c0653f36c60e60bf90b6
258dda56f37047ba5c2d1d029af9c9d40bac7aa41c78a0dd1068add699e808fea
011ea1441d8a4f7bb4e97be39f55f1ddd44e9c4ba335159703d4d34b603e65147
a4f23d6d3c0996c75edee846a82d190ae10783c961cf0387aed2106d2d0555b6f
d937fad5535387e0ff72ffbe78941402b0b822ea2a74b6058c1dabf9b34a76cb6
3b87faa2c6847b8e2837fff91186e6b1c14911cf989a89092a81ce601ddacd3f9
cf',
-1: h'010001',
-3: h'6d6502f41f84151228f24a467e1d19bb218fbcc34abd858db41fe29
221fd936d1e4fe3b5abf23bf1e8999295f15d0d144c4b362ec3514bef2e25bbd0
f80d62ae4c0c48c90ad49dd74c681dae10a4bbd81195d63bb0d03f00a64687e43
aeb5ff8dab20d2d109ef16fa7677e2e8bfa8e7e42e72bd4160c3aa9688b00f9b3
3059648316ed8c5016309074cc1332d81aa39ed389e8a9eab5844c414c704e05d
90c5e2b85854ab5054ea5f83a84896c6a83cdac5edda1f8b3274f7d38e8039826
8462a33ef9b525107c60ac8564c19cfe6e0e3775f242a1cafd3b9617d225dacf7
4ce4f972976d61b057f82ff9870aea056aeee076c3df1cfc718d539c3a906b433
c1',
-4: h'dd297183f0f04d725c6fad3de51a17ca0402019e519c0bd9967a35c
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] ]
Appendix D. Document Updates Appendix D. Document Updates
D.1. Version -04 to -05
D.1. Version -05 to -06
o Remove new CFRG Elliptical Curve key agreement algorithms.
o Remove RSA algorithms
o Define a creation time and sequence number for discussions.
o Remove message type field from all structures.
o Define CBOR tagging for all structures with IANA registrations.
D.2. Version -04 to -05
o Removed the jku, x5c, x5t, x5t#S256, x5u, and jwk headers. o Removed the jku, x5c, x5t, x5t#S256, x5u, and jwk headers.
o Add enveloped data vs encrypted data structures. o Add enveloped data vs encrypted data structures.
o Add counter signature parameter. o Add counter signature parameter.
D.2. Version -03 to -04 D.3. Version -03 to -04
o Change top level from map to array. o Change top level from map to array.
o Eliminate the term "key managment" from the document. o Eliminate the term "key management" from the document.
o Point to content registries for the 'content type' attribute o Point to content registries for the 'content type' attribute
o Push protected field into the KDF functions for recipients. o Push protected field into the KDF functions for recipients.
o Remove password based recipient information. o Remove password based recipient information.
o Create EC Curve Registry. o Create EC Curve Registry.
D.3. Version -02 to -03 D.4. Version -02 to -03
o Make a pass over all of the algorithm text. o Make a pass over all of the algorithm text.
o Alter the CDDL so that Keys and KeySets are top level items and o Alter the CDDL so that Keys and KeySets are top level items and
the key examples validate. the key examples validate.
o Add sample key structures. o Add sample key structures.
o Expand text on dealing with Externally Supplied Data. o Expand text on dealing with Externally Supplied Data.
o Update the examples to match some of the renumbering of fields. o Update the examples to match some of the renumbering of fields.
D.4. Version -02 to -03 D.5. Version -02 to -03
o Add a set of straw man proposals for algorithms. It is possible/ o Add a set of straw man proposals for algorithms. It is possible/
expected that this text will be moved to a new document. expected that this text will be moved to a new document.
o Add a set of straw man proposals for key structures. It is o Add a set of straw man proposals for key structures. It is
possible/expected that this text will be moved to a new document. possible/expected that this text will be moved to a new document.
o Provide guidance on use of externally supplied authenticated data. o Provide guidance on use of externally supplied authenticated data.
o Add external authenticated data to signing structure. o Add external authenticated data to signing structure.
D.5. Version -01 to -2 D.6. Version -01 to -2
o Add first pass of algorithm information o Add first pass of algorithm information
o Add direct key derivation example. o Add direct key derivation example.
D.6. Version -00 to -01 D.7. Version -00 to -01
o Add note on where the document is being maintained and o Add note on where the document is being maintained and
contributing notes. contributing notes.
o Put in proposal on MTI algorithms. o Put in proposal on MTI algorithms.
o Changed to use labels rather than keys when talking about what o Changed to use labels rather than keys when talking about what
indexes a map. indexes a map.
o Moved nonce/IV to be a common header item. o Moved nonce/IV to be a common header item.
skipping to change at page 90, line 40 skipping to change at page 84, line 44
Editorial Comments Editorial Comments
[CREF1] JLS: Need to check this list for correctness before publishing. [CREF1] JLS: Need to check this list for correctness before publishing.
[CREF2] JLS: I have not gone through the document to determine what [CREF2] JLS: I have not gone through the document to determine what
needs to be here yet. We mostly want to grab terms which are needs to be here yet. We mostly want to grab terms which are
used in unusual ways or are not generally understood. used in unusual ways or are not generally understood.
[CREF3] JLS: It would be possible to extend this section to talk about [CREF3] JLS: It would be possible to extend this section to talk about
those decisions which an application needs to think about rather those decisions which an application needs to think about rather
than just talking about MTI algoithms. than just talking about MTI algorithms.
[CREF4] Hannes: I would remove references to CMS and S/MIME since they
are most likely only helpful to a very small audience.
[CREF5] JLS: I have moved msg_type into the individual structures.
However, they would not be necessary in the cases where a) the
security service is known and b) security libraries can setup to
take individual structures. Should they be moved back to just
appearing if used in a COSE_MSG rather than on the individual
structure? This would make things shorter if one was using just
a signed message because the msg_type field can be omitted as
well as the COSE_Tagged_MSG tag field. One the other hand, it
will complicated the code if one is doing general purpose
library type things.
[CREF6] JLS: Should we create an IANA registries for the values of
msg_type?
[CREF7] CB: I would like to make msg_type go away
[CREF8] JLS: A completest version of this grammar would list the options [CREF4] JLS: A completest version of this grammar would list the options
available in the protected and unprotected headers. Do we want available in the protected and unprotected headers. Do we want
to head that direction? to head that direction?
[CREF9] JLS: Is there a reason to assign a CBOR tag to identify keys [CREF5] Hannes: Ensure that the list of examples only includes items
and/or key sets? which are implemented in this specification. Check the other
places where such lists occur and ensure that they also follow
[CREF10] JLS: We can really simplify the grammar for COSE_Key to be just this rule.
the kty (the one required field) and the generic item. The
reason to do this is that it makes things simpler. The reason
not to do this says that we really need to add a lot more items
so that a grammar check can be done that is more tightly
enforced.
[CREF11] Ilari: Look to see if we need to be clearer about how the
fields defined in the table are transported and thus why they
have labels.
[CREF12] Ilari: Check to see what the curves are renamed to during final [CREF6] JLS: We can really simplify the grammar for COSE_Key to be just
publishing. It appears to be X25519 now. the kty (the one required field) and the generic item. The
reason to do this is that it makes things simpler. The reason
not to do this says that we really need to add a lot more items
so that a grammar check can be done that is more tightly
enforced.
[CREF13] JLS: Do we create a registry for curves? Is is the same [CREF7] Ilari: Look to see if we need to be clearer about how the fields
registry for both EC1 and EC2? defined in the table are transported and thus why they have
labels.
[CREF14] JLS: Should we use the bignum encoding for x, y and d instead [CREF8] JLS: Should we register both or just the cose+cbor one?
of bstr?
[CREF15] JLS: Looking at the CBOR specification, the bstr that we are [CREF9] JLS: Should we create the equivalent of the smime-type parameter
looking in our table below should most likely be specified as to identify the inner content type?
big numbers rather than as binary strings. This means that we
would use the tag 6.2 instead. From my reading of the
specification, there is no difference in the encoded size of
the resulting output. The specification of bignum does
explicitly allow for integers encoded with leading zeros.
[CREF16] JLS: Should we register both or just the cose+cbor one? Author's Address
Authors' Addresses
Jim Schaad Jim Schaad
August Cellars August Cellars
Email: ietf@augustcellars.com Email: ietf@augustcellars.com
Brian Campbell
Ping Identity
Email: brian.d.campbell@gmail.com
 End of changes. 206 change blocks. 
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