draft-ietf-cose-rfc8152bis-struct-10.txt   draft-ietf-cose-rfc8152bis-struct-11.txt 
COSE Working Group J. Schaad COSE Working Group J. Schaad
Internet-Draft August Cellars Internet-Draft August Cellars
Obsoletes: 8152 (if approved) 2 June 2020 Obsoletes: 8152 (if approved) 1 July 2020
Intended status: Standards Track Intended status: Standards Track
Expires: 4 December 2020 Expires: 2 January 2021
CBOR Object Signing and Encryption (COSE): Structures and Process CBOR Object Signing and Encryption (COSE): Structures and Process
draft-ietf-cose-rfc8152bis-struct-10 draft-ietf-cose-rfc8152bis-struct-11
Abstract Abstract
Concise Binary Object Representation (CBOR) is a data format designed Concise Binary Object Representation (CBOR) is a 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 basic security services defined for this data format. ability to have basic security services defined for this data format.
This document defines the CBOR Object Signing and Encryption (COSE) This document defines the CBOR Object Signing and Encryption (COSE)
protocol. This specification describes how to create and process protocol. This specification describes how to create and process
signatures, message authentication codes, and encryption using CBOR signatures, message authentication codes, and encryption using CBOR
for serialization. This specification additionally describes how to for serialization. This specification additionally describes how to
skipping to change at page 2, line 4 skipping to change at page 2, line 4
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-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
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 4 December 2020. This Internet-Draft will expire on 2 January 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 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 (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 37 skipping to change at page 2, line 37
1.5. CBOR-Related Terminology . . . . . . . . . . . . . . . . 8 1.5. CBOR-Related Terminology . . . . . . . . . . . . . . . . 8
1.6. Document Terminology . . . . . . . . . . . . . . . . . . 9 1.6. Document Terminology . . . . . . . . . . . . . . . . . . 9
2. Basic COSE Structure . . . . . . . . . . . . . . . . . . . . 9 2. Basic COSE Structure . . . . . . . . . . . . . . . . . . . . 9
3. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 13 3. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 13
3.1. Common COSE Header Parameters . . . . . . . . . . . . . . 15 3.1. Common COSE Header Parameters . . . . . . . . . . . . . . 15
4. Signing Objects . . . . . . . . . . . . . . . . . . . . . . . 18 4. Signing Objects . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. Signing with One or More Signers . . . . . . . . . . . . 18 4.1. Signing with One or More Signers . . . . . . . . . . . . 18
4.2. Signing with One Signer . . . . . . . . . . . . . . . . . 20 4.2. Signing with One Signer . . . . . . . . . . . . . . . . . 20
4.3. Externally Supplied Data . . . . . . . . . . . . . . . . 21 4.3. Externally Supplied Data . . . . . . . . . . . . . . . . 21
4.4. Signing and Verification Process . . . . . . . . . . . . 22 4.4. Signing and Verification Process . . . . . . . . . . . . 22
5. Counter Signatures . . . . . . . . . . . . . . . . . . . . . 24 5. Counter Signatures . . . . . . . . . . . . . . . . . . . . . 25
5.1. Full Counter Signatures . . . . . . . . . . . . . . . . . 25 5.1. Full Counter Signatures . . . . . . . . . . . . . . . . . 26
5.2. Abbreviated Counter Signatures . . . . . . . . . . . . . 26 5.2. Abbreviated Counter Signatures . . . . . . . . . . . . . 26
6. Encryption Objects . . . . . . . . . . . . . . . . . . . . . 26 6. Encryption Objects . . . . . . . . . . . . . . . . . . . . . 27
6.1. Enveloped COSE Structure . . . . . . . . . . . . . . . . 26 6.1. Enveloped COSE Structure . . . . . . . . . . . . . . . . 27
6.1.1. Content Key Distribution Methods . . . . . . . . . . 28 6.1.1. Content Key Distribution Methods . . . . . . . . . . 29
6.2. Single Recipient Encrypted . . . . . . . . . . . . . . . 29 6.2. Single Recipient Encrypted . . . . . . . . . . . . . . . 30
6.3. How to Encrypt and Decrypt for AEAD Algorithms . . . . . 29 6.3. How to Encrypt and Decrypt for AEAD Algorithms . . . . . 30
6.4. How to Encrypt and Decrypt for AE Algorithms . . . . . . 32 6.4. How to Encrypt and Decrypt for AE Algorithms . . . . . . 33
7. MAC Objects . . . . . . . . . . . . . . . . . . . . . . . . . 33 7. MAC Objects . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.1. MACed Message with Recipients . . . . . . . . . . . . . . 34 7.1. MACed Message with Recipients . . . . . . . . . . . . . . 35
7.2. MACed Messages with Implicit Key . . . . . . . . . . . . 35 7.2. MACed Messages with Implicit Key . . . . . . . . . . . . 36
7.3. How to Compute and Verify a MAC . . . . . . . . . . . . . 35 7.3. How to Compute and Verify a MAC . . . . . . . . . . . . . 36
8. Key Objects . . . . . . . . . . . . . . . . . . . . . . . . . 37 8. Key Objects . . . . . . . . . . . . . . . . . . . . . . . . . 38
8.1. COSE Key Common Parameters . . . . . . . . . . . . . . . 37 8.1. COSE Key Common Parameters . . . . . . . . . . . . . . . 38
9. Taxonomy of Algorithms used by COSE . . . . . . . . . . . . . 40 9. Taxonomy of Algorithms used by COSE . . . . . . . . . . . . . 41
9.1. Signature Algorithms . . . . . . . . . . . . . . . . . . 41 9.1. Signature Algorithms . . . . . . . . . . . . . . . . . . 42
9.2. Message Authentication Code (MAC) Algorithms . . . . . . 42 9.2. Message Authentication Code (MAC) Algorithms . . . . . . 43
9.3. Content Encryption Algorithms . . . . . . . . . . . . . . 42 9.3. Content Encryption Algorithms . . . . . . . . . . . . . . 43
9.4. Key Derivation Functions (KDFs) . . . . . . . . . . . . . 43 9.4. Key Derivation Functions (KDFs) . . . . . . . . . . . . . 44
9.5. Content Key Distribution Methods . . . . . . . . . . . . 44 9.5. Content Key Distribution Methods . . . . . . . . . . . . 45
9.5.1. Direct Encryption . . . . . . . . . . . . . . . . . . 44 9.5.1. Direct Encryption . . . . . . . . . . . . . . . . . . 45
9.5.2. Key Wrap . . . . . . . . . . . . . . . . . . . . . . 44 9.5.2. Key Wrap . . . . . . . . . . . . . . . . . . . . . . 45
9.5.3. Key Transport . . . . . . . . . . . . . . . . . . . . 45 9.5.3. Key Transport . . . . . . . . . . . . . . . . . . . . 46
9.5.4. Direct Key Agreement . . . . . . . . . . . . . . . . 45 9.5.4. Direct Key Agreement . . . . . . . . . . . . . . . . 46
9.5.5. Key Agreement with Key Wrap . . . . . . . . . . . . . 46 9.5.5. Key Agreement with Key Wrap . . . . . . . . . . . . . 47
10. CBOR Encoding Restrictions . . . . . . . . . . . . . . . . . 47 10. CBOR Encoding Restrictions . . . . . . . . . . . . . . . . . 48
11. Application Profiling Considerations . . . . . . . . . . . . 47 11. Application Profiling Considerations . . . . . . . . . . . . 48
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50
12.1. CBOR Tag Assignment . . . . . . . . . . . . . . . . . . 49 12.1. CBOR Tag Assignment . . . . . . . . . . . . . . . . . . 50
12.2. COSE Header Parameters Registry . . . . . . . . . . . . 49 12.2. COSE Header Parameters Registry . . . . . . . . . . . . 50
12.3. COSE Header Algorithm Parameters Registry . . . . . . . 49 12.3. COSE Key Common Parameters Registry . . . . . . . . . . 50
12.4. COSE Key Common Parameters Registry . . . . . . . . . . 49 12.4. Media Type Registrations . . . . . . . . . . . . . . . . 50
12.5. Media Type Registrations . . . . . . . . . . . . . . . . 50 12.4.1. COSE Security Message . . . . . . . . . . . . . . . 51
12.5.1. COSE Security Message . . . . . . . . . . . . . . . 50 12.4.2. COSE Key Media Type . . . . . . . . . . . . . . . . 52
12.5.2. COSE Key Media Type . . . . . . . . . . . . . . . . 51 12.5. CoAP Content-Formats Registry . . . . . . . . . . . . . 54
12.6. CoAP Content-Formats Registry . . . . . . . . . . . . . 53 12.6. Expert Review Instructions . . . . . . . . . . . . . . . 54
13. Security Considerations . . . . . . . . . . . . . . . . . . . 53 13. Security Considerations . . . . . . . . . . . . . . . . . . . 55
14. Implementation Status . . . . . . . . . . . . . . . . . . . . 55 14. Implementation Status . . . . . . . . . . . . . . . . . . . . 56
14.1. Author's Versions . . . . . . . . . . . . . . . . . . . 55 14.1. Author's Versions . . . . . . . . . . . . . . . . . . . 57
14.2. JavaScript Version . . . . . . . . . . . . . . . . . . . 56 14.2. JavaScript Version . . . . . . . . . . . . . . . . . . . 58
14.3. Python Version . . . . . . . . . . . . . . . . . . . . . 56 14.3. Python Version . . . . . . . . . . . . . . . . . . . . . 58
14.4. COSE Testing Library . . . . . . . . . . . . . . . . . . 57 14.4. COSE Testing Library . . . . . . . . . . . . . . . . . . 58
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 57 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 59
15.1. Normative References . . . . . . . . . . . . . . . . . . 57 15.1. Normative References . . . . . . . . . . . . . . . . . . 59
15.2. Informative References . . . . . . . . . . . . . . . . . 58 15.2. Informative References . . . . . . . . . . . . . . . . . 59
Appendix A. Guidelines for External Data Authentication of Appendix A. Guidelines for External Data Authentication of
Algorithms . . . . . . . . . . . . . . . . . . . . . . . 61 Algorithms . . . . . . . . . . . . . . . . . . . . . . . 63
Appendix B. Two Layers of Recipient Information . . . . . . . . 65 Appendix B. Two Layers of Recipient Information . . . . . . . . 66
Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 66 Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 68
C.1. Examples of Signed Messages . . . . . . . . . . . . . . . 67 C.1. Examples of Signed Messages . . . . . . . . . . . . . . . 69
C.1.1. Single Signature . . . . . . . . . . . . . . . . . . 67 C.1.1. Single Signature . . . . . . . . . . . . . . . . . . 69
C.1.2. Multiple Signers . . . . . . . . . . . . . . . . . . 68 C.1.2. Multiple Signers . . . . . . . . . . . . . . . . . . 70
C.1.3. Counter Signature . . . . . . . . . . . . . . . . . . 69 C.1.3. Counter Signature . . . . . . . . . . . . . . . . . . 71
C.1.4. Signature with Criticality . . . . . . . . . . . . . 70 C.1.4. Signature with Criticality . . . . . . . . . . . . . 72
C.2. Single Signer Examples . . . . . . . . . . . . . . . . . 71 C.2. Single Signer Examples . . . . . . . . . . . . . . . . . 73
C.2.1. Single ECDSA Signature . . . . . . . . . . . . . . . 71 C.2.1. Single ECDSA Signature . . . . . . . . . . . . . . . 73
C.3. Examples of Enveloped Messages . . . . . . . . . . . . . 72 C.3. Examples of Enveloped Messages . . . . . . . . . . . . . 74
C.3.1. Direct ECDH . . . . . . . . . . . . . . . . . . . . . 72 C.3.1. Direct ECDH . . . . . . . . . . . . . . . . . . . . . 74
C.3.2. Direct Plus Key Derivation . . . . . . . . . . . . . 73 C.3.2. Direct Plus Key Derivation . . . . . . . . . . . . . 75
C.3.3. Counter Signature on Encrypted Content . . . . . . . 74 C.3.3. Counter Signature on Encrypted Content . . . . . . . 76
C.3.4. Encrypted Content with External Data . . . . . . . . 75 C.3.4. Encrypted Content with External Data . . . . . . . . 77
C.4. Examples of Encrypted Messages . . . . . . . . . . . . . 76 C.4. Examples of Encrypted Messages . . . . . . . . . . . . . 78
C.4.1. Simple Encrypted Message . . . . . . . . . . . . . . 76 C.4.1. Simple Encrypted Message . . . . . . . . . . . . . . 78
C.4.2. Encrypted Message with a Partial IV . . . . . . . . . 77 C.4.2. Encrypted Message with a Partial IV . . . . . . . . . 79
C.5. Examples of MACed Messages . . . . . . . . . . . . . . . 77 C.5. Examples of MACed Messages . . . . . . . . . . . . . . . 79
C.5.1. Shared Secret Direct MAC . . . . . . . . . . . . . . 77 C.5.1. Shared Secret Direct MAC . . . . . . . . . . . . . . 79
C.5.2. ECDH Direct MAC . . . . . . . . . . . . . . . . . . . 78 C.5.2. ECDH Direct MAC . . . . . . . . . . . . . . . . . . . 80
C.5.3. Wrapped MAC . . . . . . . . . . . . . . . . . . . . . 79 C.5.3. Wrapped MAC . . . . . . . . . . . . . . . . . . . . . 81
C.5.4. Multi-Recipient MACed Message . . . . . . . . . . . . 80 C.5.4. Multi-Recipient MACed Message . . . . . . . . . . . . 82
C.6. Examples of MAC0 Messages . . . . . . . . . . . . . . . . 81 C.6. Examples of MAC0 Messages . . . . . . . . . . . . . . . . 83
C.6.1. Shared Secret Direct MAC . . . . . . . . . . . . . . 81 C.6.1. Shared Secret Direct MAC . . . . . . . . . . . . . . 83
C.7. COSE Keys . . . . . . . . . . . . . . . . . . . . . . . . 82 C.7. COSE Keys . . . . . . . . . . . . . . . . . . . . . . . . 84
C.7.1. Public Keys . . . . . . . . . . . . . . . . . . . . . 82 C.7.1. Public Keys . . . . . . . . . . . . . . . . . . . . . 84
C.7.2. Private Keys . . . . . . . . . . . . . . . . . . . . 83 C.7.2. Private Keys . . . . . . . . . . . . . . . . . . . . 85
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 85 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 87
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 86 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 88
1. Introduction 1. Introduction
There has been an increased focus on small, constrained devices that There has been an increased focus on small, constrained devices that
make up the Internet of Things (IoT). One of the standards that has make up the Internet of Things (IoT). One of the standards that has
come out of this process is "Concise Binary Object Representation come out of this process is "Concise Binary Object Representation
(CBOR)" [RFC7049]. CBOR extended the data model of the JavaScript (CBOR)" [RFC7049]. CBOR extended the data model of the JavaScript
Object Notation (JSON) [RFC8259] by allowing for binary data, among Object Notation (JSON) [STD90] by allowing for binary data, among
other changes. CBOR has been adopted by several of the IETF working other changes. CBOR has been 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 both to be small in terms structures. CBOR was designed specifically both to be small in terms
of messages transported and implementation size and be a schema-free of messages transported and implementation size and to be a schema-
decoder. A need exists to provide message security services for IoT, free decoder. A need exists to provide message security services for
and using CBOR as the message-encoding format makes sense. IoT, and using CBOR as the message-encoding format makes sense.
The JOSE working group produced a set of documents [RFC7515] The JOSE working group produced a set of documents [RFC7515]
[RFC7516] [RFC7517] [RFC7518] that specified how to process [RFC7516] [RFC7517] [RFC7518] that specified how to process
encryption, signatures, and Message Authentication Code (MAC) encryption, signatures, and Message Authentication Code (MAC)
operations and how to encode keys using JSON. This document along operations and how to encode keys using JSON. This document along
with [I-D.ietf-cose-rfc8152bis-algs] defines the CBOR Object Signing with [I-D.ietf-cose-rfc8152bis-algs] defines the CBOR Object Signing
and Encryption (COSE) standard, which does the same thing for the and Encryption (COSE) standard, which does the same thing for the
CBOR encoding format. While there is a strong attempt to keep the CBOR encoding format. While there is a strong attempt to keep the
flavor of the original JSON Object Signing and Encryption (JOSE) flavor of the original JSON Object Signing and Encryption (JOSE)
documents, two considerations are taken into account: documents, two considerations are taken into account:
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into a base64-encoded text string. into a base64-encoded text string.
* COSE is not a direct copy of the JOSE specification. In the * COSE is not a direct copy of the JOSE specification. In the
process of creating COSE, decisions that were made for JOSE were process of creating COSE, decisions that were made for JOSE were
re-examined. In many cases, different results were decided on as re-examined. In many cases, different results were decided on as
the criteria were not always the same. the criteria were not always the same.
This document contains: This document contains:
* The description of the structure for the CBOR objects which are * The description of the structure for the CBOR objects which are
transmitted over the wire. Two objects are defined for transmitted over the wire. Two objects are defined for each of
encryption, signing and message authentication. One object is encryption, signing and message authentication. One object is
defined for transporting keys and one for transporting groups of defined for transporting keys and one for transporting groups of
keys. keys.
* The procedures used to build the inputs to the cryptographic * The procedures used to build the inputs to the cryptographic
functions required for each of the structures. functions required for each of the structures.
* A starting set of attributes that apply to the different security * A set of attributes that apply to the different security objects.
objects.
This document does not contain the rules and procedures for using This document does not contain the rules and procedures for using
specific cryptographic algorithms. Details on specific algorithms specific cryptographic algorithms. Details on specific algorithms
can be found in [I-D.ietf-cose-rfc8152bis-algs] and [RFC8230]. can be found in [I-D.ietf-cose-rfc8152bis-algs] and [RFC8230].
Details for additional algorithms are expected to be defined in Details for additional algorithms are expected to be defined in
future documents. future documents.
COSE was initially designed as part of a solution to provide security COSE was initially designed as part of a solution to provide security
to Constrained RESTful Environments (CoRE), and this is done using to Constrained RESTful Environments (CoRE), and this is done using
[RFC8613] and [I-D.ietf-core-groupcomm-bis]. However, COSE is not [RFC8613] and [I-D.ietf-core-groupcomm-bis]. However, COSE is not
restricted to just these cases and can be used in any place where one restricted to just these cases and can be used in any place where one
would consider either JOSE or CMS [RFC5652] for the purpose of would consider either JOSE or CMS [RFC5652] for the purpose of
providing security services. The use of COSE, like JOSE and CMS, is providing security services. The use of COSE, like JOSE and CMS, is
only in store and forward or offline protocols, different solutions only for use in store and forward or offline protocols. The use of
would be appropriate for online protocols although one can use COSE COSE in online protocols needing encryption, require that an online
in an online protocol after having done some type of online key key establishment process be done before sending objects back and
establishment process. Any application which uses COSE for security forth. Any application which uses COSE for security services first
services first needs to determine what security services are required needs to determine what security services are required and then
and then select the appropriate COSE structures and cryptographic select the appropriate COSE structures and cryptographic algorithms
algorithms based on those needs. Section 11 provides additional based on those needs. Section 11 provides additional information on
information on what applications need to specify when using COSE. what applications need to specify when using COSE.
One feature that is present in CMS that is not present in this One feature that is present in CMS that is not present in this
standard is a digest structure. This omission is deliberate. It is standard is a digest structure. This omission is deliberate. It is
better for the structure to be defined in each protocol as different better for the structure to be defined in each protocol as different
protocols will want to include a different set of fields as part of protocols will want to include a different set of fields as part of
the structure. While an algorithm identifier and the digest value the structure. While an algorithm identifier and the digest value
are going to be common to all applications, the two values may not are going to be common to all applications, the two values may not
always be adjacent as the algorithm could be defined once with always be adjacent as the algorithm could be defined once with
multiple values. Applications may additionally want to define multiple values. Applications may additionally want to define
additional data fields as part of the structure. A common structure additional data fields as part of the structure. A one such
is going to include a URI or other pointer to where the data that is application-specific element would be to include a URI or other
being hashed is kept, allowing this to be application-specific. pointer to where the data that is being hashed can be obtained.
[I-D.ietf-cose-hash-algs] contains one such possible structure along [I-D.ietf-cose-hash-algs] contains one such possible structure along
with defining a set of digest algorithms. with defining a set of digest algorithms.
1.1. Requirements Terminology 1.1. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
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* Add some text describing why there is no digest structure defined * Add some text describing why there is no digest structure defined
by COSE. by COSE.
* Rearrange the text around counter signatures and define a CBOR Tag * Rearrange the text around counter signatures and define a CBOR Tag
for a standalone counter signature. for a standalone counter signature.
* Text clarifications and changes in terminology. * Text clarifications and changes in terminology.
1.3. Design Changes from JOSE 1.3. Design Changes from JOSE
* Define a single top message structure so that encrypted, signed, * Define a single overall message structure so that encrypted,
and MACed messages can easily be identified and still have a signed, and MACed messages can easily be identified and still have
consistent view. a consistent view.
* Signed messages distinguish between the protected and unprotected * Signed messages distinguish between the protected and unprotected
header parameters that relate to the content from those that header parameters that relate to the content and those that relate
relate to the signature. to the signature.
* MACed messages are separated from signed messages. * MACed messages are separated from signed messages.
* MACed messages have the ability to use the same set of recipient * MACed messages have the ability to use the same set of recipient
algorithms as enveloped messages for obtaining the MAC algorithms as enveloped messages for obtaining the MAC
authentication key. authentication key.
* Use binary encodings, rather than base64url encodings, to encode * Use binary encodings, rather than base64url encodings, to encode
binary data. binary data.
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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
text string. In COSE, we use text strings, negative integers, and text string. In COSE, we use text strings, negative integers, and
unsigned integers as map keys. The integers are used for compactness unsigned integers as map keys. The integers are used for compactness
of encoding and easy comparison. The inclusion of text strings of encoding and easy comparison. The inclusion of text strings
allows for an additional range of short encoded values to be used as allows for an additional range of short encoded values to be used as
well. Since the word "key" is mainly used in its other meaning, as a well. Since the word "key" is mainly used in its other meaning, as a
cryptographic key, we use the term "label" for this usage as a map cryptographic key, we use the term "label" for this usage as a map
key. key.
The presence in a CBOR map of a label that is not a text string or an The presence a label that is neither a a text string bor an integer,
integer is an error. Applications can either fail processing or in a CBOR map, is an error. Applications can either fail processing
process messages by ignoring incorrect labels; however, they MUST NOT or process messages by ignoring incorrect labels; however, they MUST
create messages with incorrect labels. NOT create messages with incorrect labels.
A CDDL grammar fragment defines the non-terminal 'label', as in the A CDDL grammar fragment defines the non-terminal 'label', as in the
previous paragraph, and 'values', which permits any value to be used. previous paragraph, and 'values', which permits any value to be used.
label = int / tstr label = int / tstr
values = any values = any
1.6. Document Terminology 1.6. Document Terminology
In this document, we use the following terminology: In this document, we use the following terminology:
Byte is a synonym for octet. Byte is a synonym for octet.
Constrained Application Protocol (CoAP) is a specialized web transfer Constrained Application Protocol (CoAP) is a specialized web transfer
protocol for use in constrained systems. It is defined in [RFC7252]. protocol for use in constrained systems. It is defined in [RFC7252].
Authenticated Encryption (AE) [RFC5116] algorithms are those Authenticated Encryption (AE) [RFC5116] algorithms are encryption
encryption algorithms that provide an authentication check of the algorithms that provide an authentication check of the contents with
contents algorithm with the encryption service. the encryption service. An example of an AE algorithm used in COSE
is AES Key Wrap [RFC3394]. These algorithms are used for key
encryption algorithms, but AEAD algorithms would be preferred.
Authenticated Encryption with Associated Data (AEAD) [RFC5116] Authenticated Encryption with Associated Data (AEAD) [RFC5116]
algorithms provide the same content authentication service as AE algorithms provide the same authentication service of the content as
algorithms, but they additionally provide for authentication of non- AE algorithms do. They also allow for associated data to be included
encrypted data as well. in the authentication service, but which is not part of the encrypted
body. An example of an AEAD algorithm used in COSE is AES-GCM
[RFC5116]. These algorithms are used for content encryption and can
be used for key encryption as well.
Context is used throughout the document to represent information that Context is used throughout the document to represent information that
is not part of the COSE message. Information which is part of the is not part of the COSE message. Information which is part of the
context can come from several different sources including: Protocol context can come from several different sources including: Protocol
interactions, associated key structures and program configuration. interactions, associated key structures, and program configuration.
The context to use can be implicit, identified using the 'kid The context to use can be implicit, identified using the 'kid
context' header parameter defined in [RFC8613], or identified by a context' header parameter defined in [RFC8613], or identified by a
protocol-specific identifier. Context should generally be included protocol-specific identifier. Context should generally be included
in the cryptographic configuration; for more details see Section 4.3. in the cryptographic construction; for more details see Section 4.3.
The term 'byte string' is used for sequences of bytes, while the term The term 'byte string' is used for sequences of bytes, while the term
'text string' is used for sequences of characters. 'text string' is used for sequences of characters.
2. Basic COSE Structure 2. Basic COSE Structure
The COSE object structure is designed so that there can be a large The COSE object structure is designed so that there can be a large
amount of common code when parsing and processing the different types amount of common code when parsing and processing the different types
of security messages. All of the message structures are built on the of security messages. All of the message structures are built on the
CBOR array type. The first three elements of the array always CBOR array type. The first three elements of the array always
contain the same information: contain the same information:
1. The protected header parameters encoded and wrapped in a bstr. 1. The protected header parameters, encoded and wrapped in a bstr.
2. The unprotected header parameters as a map. 2. The unprotected header parameters as a map.
3. The content of the message. The content is either the plaintext 3. The content of the message. The content is either the plaintext
or the ciphertext as appropriate. The content may be detached or the ciphertext as appropriate. The content may be detached
(i.e. transported separately from the COSE structure), but the (i.e. transported separately from the COSE structure), but the
location is still used. The content is wrapped in a bstr when location is still used. The content is wrapped in a bstr when
present and is a nil value when detached. present and is a nil value when detached.
Elements after this point are dependent on the specific message type. Elements after this point are dependent on the specific message type.
COSE messages are built using the concept of layers to separate COSE messages are built using the concept of layers to separate
different types of cryptographic concepts. As an example of how this different types of cryptographic concepts. As an example of how this
works, consider the COSE_Encrypt message (Section 6.1). This message works, consider the COSE_Encrypt message (Section 6.1). This message
type is broken into two layers: the content layer and the recipient type is broken into two layers: the content layer and the recipient
layer. In the content layer, the plaintext is encrypted and layer. The content layer contains the plaintext is encrypted and
information about the encrypted message is placed. In the recipient information about the encrypted message. The recipient layer contins
layer, the content encryption key (CEK) is encrypted and information the content encryption key (CEK) is encrypted and information about
about how it is encrypted for each recipient is placed. A single how it is encrypted for each recipient. A single layer version of
layer version of the encryption message COSE_Encrypt0 (Section 6.2) the encryption message COSE_Encrypt0 (Section 6.2) is provided for
is provided for cases where the CEK is pre-shared. cases where the CEK is pre-shared.
Identification of which type of message has been presented is done by Identification of which type of message has been presented is done by
the following methods: the following methods:
1. The specific message type is known from the context. This may be 1. The specific message type is known from the context. This may be
defined by a marker in the containing structure or by defined by a marker in the containing structure or by
restrictions specified by the application protocol. restrictions specified by the application protocol.
2. The message type is identified by a CBOR tag. Messages with a 2. The message type is identified by a CBOR tag. Messages with a
CBOR tag are known in this specification as tagged messages, CBOR tag are known in this specification as tagged messages,
skipping to change at page 11, line 5 skipping to change at page 11, line 5
the untagged version of the structure is used. The value to use the untagged version of the structure is used. The value to use
with the parameter for each of the structures can be found in with the parameter for each of the structures can be found in
Table 1. Table 1.
4. When a COSE object is carried as a CoAP payload, the CoAP 4. When a COSE object is carried as a CoAP payload, the CoAP
Content-Format Option can be used to identify the message Content-Format Option can be used to identify the message
content. The CoAP Content-Format values can be found in Table 2. content. The CoAP Content-Format values can be found in Table 2.
The CBOR tag for the message structure is not required as each The CBOR tag for the message structure is not required as each
security message is uniquely identified. security message is uniquely identified.
+------+------------------+-----------------------+-------------+ +=======+==================+=======================+=============+
| CBOR | cose-type | Data Item | Semantics | | CBOR | cose-type | Data Item | Semantics |
| Tag | | | | | Tag | | | |
+======+==================+=======================+=============+ +=======+==================+=======================+=============+
| 98 | cose-sign | COSE_Sign | COSE Signed | | 98 | cose-sign | COSE_Sign | COSE Signed |
| | | | Data Object | | | | | Data Object |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
| 18 | cose-sign1 | COSE_Sign1 | COSE Single | | 18 | cose-sign1 | COSE_Sign1 | COSE Single |
| | | | Signer Data | | | | | Signer Data |
| | | | Object | | | | | Object |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
| 96 | cose-encrypt | COSE_Encrypt | COSE | | 96 | cose-encrypt | COSE_Encrypt | COSE |
| | | | Encrypted | | | | | Encrypted |
| | | | Data Object | | | | | Data Object |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
| 16 | cose-encrypt0 | COSE_Encrypt0 | COSE Single | | 16 | cose-encrypt0 | COSE_Encrypt0 | COSE Single |
| | | | Recipient | | | | | Recipient |
| | | | Encrypted | | | | | Encrypted |
| | | | Data Object | | | | | Data Object |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
| 97 | cose-mac | COSE_Mac | COSE MACed | | 97 | cose-mac | COSE_Mac | COSE MACed |
| | | | Data Object | | | | | Data Object |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
| 17 | cose-mac0 | COSE_Mac0 | COSE Mac w/ | | 17 | cose-mac0 | COSE_Mac0 | COSE Mac w/ |
| | | | o | | | | | o |
| | | | Recipients | | | | | Recipients |
| | | | Object | | | | | Object |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
| TBD0 | cose-countersign | COSE_Countersignature | COSE | | TBD00 | cose-countersign | COSE_Countersignature | COSE |
| | | | standalone | | | | | standalone |
| | | | counter | | | | | counter |
| | | | signature | | | | | signature |
+------+------------------+-----------------------+-------------+ +-------+------------------+-----------------------+-------------+
Table 1: COSE Message Identification Table 1: COSE Message Identification
+---------------------------+----------+-----+------------+ +===========================+==========+=====+============+
| Media Type | Encoding | ID | Reference | | Media Type | Encoding | ID | Reference |
+===========================+==========+=====+============+ +===========================+==========+=====+============+
| application/cose; cose- | | 98 | [[THIS | | application/cose; cose- | | 98 | [[THIS |
| type="cose-sign" | | | DOCUMENT]] | | type="cose-sign" | | | DOCUMENT]] |
+---------------------------+----------+-----+------------+ +---------------------------+----------+-----+------------+
| application/cose; cose- | | 18 | [[THIS | | application/cose; cose- | | 18 | [[THIS |
| type="cose-sign1" | | | DOCUMENT]] | | type="cose-sign1" | | | DOCUMENT]] |
+---------------------------+----------+-----+------------+ +---------------------------+----------+-----+------------+
| application/cose; cose- | | 96 | [[THIS | | application/cose; cose- | | 96 | [[THIS |
| type="cose-encrypt" | | | DOCUMENT]] | | type="cose-encrypt" | | | DOCUMENT]] |
skipping to change at page 13, line 12 skipping to change at page 13, line 12
COSE_Encrypt_Tagged / COSE_Encrypt0_Tagged / COSE_Encrypt_Tagged / COSE_Encrypt0_Tagged /
COSE_Mac_Tagged / COSE_Mac0_Tagged / COSE_Countersignature_Tagged COSE_Mac_Tagged / COSE_Mac0_Tagged / COSE_Countersignature_Tagged
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 except for buckets are available for use in all of the structures except for
keys. While these buckets are present, they may not all be usable in keys. While these buckets are present, they may not always be usable
all instances. For example, while the protected bucket is defined as in all instances. For example, while the protected bucket is defined
part of the recipient structure, some of the algorithms used for as part of the recipient structure, some of the algorithms used for
recipient structures do not provide for authenticated data. If this recipient structures do not provide for authenticated data. If this
is the case, the protected bucket is left empty. is the case, the protected bucket is left empty.
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 1.5). The value portion is dependent on the definition for (Section 1.5). 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 text string values for labels have been divided into integer and text string values for labels have been divided into
several sections including a standard range, a private range, and a several sections including a standard range, a private range, and a
range that is dependent on the algorithm selected. The defined range that is dependent on the algorithm selected. The defined
labels can be found in the "COSE Header Parameters" IANA registry labels can be found in the "COSE Header Parameters" IANA registry
skipping to change at page 13, line 38 skipping to change at page 13, line 38
protected: Contains parameters about the current layer that are protected: Contains parameters about the current layer that are
cryptographically protected. This bucket MUST be empty if it is cryptographically protected. This bucket MUST be empty if it is
not going to be included in a cryptographic computation. This 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 a zero-length map as a zero- a bstr object. Senders SHOULD encode a zero-length map as a zero-
length byte string rather than as a zero-length map (encoded as length byte string rather than as a zero-length map (encoded as
h'a0'). The zero-length binary encoding is preferred because it h'a0'). The zero-length binary encoding is preferred because it
is both shorter and the version used in the serialization is both shorter and the version used in the serialization
structures for cryptographic computation. After encoding the map, structures for cryptographic computation. Recipients MUST accept
the value is wrapped in the binary object. Recipients MUST accept both a zero-length byte string and a zero-length map encoded in a
both a zero-length byte string and a zero-length map encoded in byte string.
the binary value.
Wrapping the encoding with a byte string allows for the protected Wrapping the encoding with a byte string allows for the protected
map to be transported with a greater chance that it will not be map to be transported with a greater chance that it will not be
altered accidentally in transit. (Badly behaved intermediates altered accidentally in transit. (Badly behaved intermediates
could decode and re-encode, but this will result in a failure to could decode and re-encode, but this will result in a failure to
verify unless the re-encoded byte string is identical to the verify unless the re-encoded byte string is identical to the
decoded byte string.) This avoids the problem of all parties decoded byte string.) This avoids the problem of all parties
needing to be able to do a common canonical encoding. needing to be able to do a common canonical encoding of the map
for input to cyprtographic operations.
unprotected: Contains parameters about the current layer that are unprotected: Contains parameters about the current layer that are
not cryptographically protected. not cryptographically protected.
Only header parameters that deal with the current layer are to be Only header parameters that deal with the current layer are to be
placed at that layer. As an example of this, the header parameter placed at that layer. As an example of this, the header parameter
'content type' describes the content of the message being carried in 'content type' describes the content of the message being carried in
the message. As such, this header parameter is placed only in the the message. As such, this header parameter is placed only in the
content layer and is not placed in the recipient or signature layers. content layer and is not placed in the recipient or signature layers.
In principle, one should be able to process any given layer without In principle, one should be able to process any given layer without
reference to any other layer. With the exception of the COSE_Sign reference to any other layer. With the exception of the COSE_Sign
structure, the only data that needs to cross layers is the structure, the only data that needs 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 header type). The presence of both buckets is required. The header
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" registry (Section 12.2). Some common header parameters Parameters" registry (Section 12.2). Some header parameters are
are defined in the next section. defined in the next section.
Labels in each of the maps MUST be unique. When processing messages, Labels in each of the maps MUST be unique. When processing messages,
if a label appears multiple times, the message MUST be rejected as if a label appears multiple times, the message MUST be rejected as
malformed. Applications SHOULD verify that the same label does not malformed. Applications SHOULD verify that the same label does not
occur in both the protected and unprotected header parameters. If occur in both the protected and unprotected header parameters. If
the message is not rejected as malformed, attributes MUST be obtained the message is not rejected as malformed, attributes MUST be obtained
from the protected bucket before they are obtained from the from the protected bucket, and only if not found are attributes
unprotected bucket. obtained from the unprotected bucket.
The following CDDL fragment represents the two header parameter The following CDDL fragment represents the two header parameter
buckets. A group "Headers" is defined in CDDL that represents the buckets. A group "Headers" is defined in CDDL that represents the
two buckets in which attributes are placed. This group is used to two buckets in which attributes are placed. This group is used to
provide these two fields consistently in all locations. A type is provide these two fields consistently in all locations. A type is
also defined that represents the map of common header parameters. also defined that represents the map of common header parameters.
Headers = ( Headers = (
protected : empty_or_serialized_map, protected : empty_or_serialized_map,
unprotected : header_map unprotected : header_map
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This section defines a set of common header parameters. A summary of This section defines a set of common header parameters. A summary of
these header parameters can be found in Table 3. This table should these header parameters can be found in Table 3. This table should
be consulted to determine the value of label and the type of the be consulted to determine the value of label and the type of the
value. value.
The set of header parameters defined in this section are: The set of header parameters defined in this section are:
alg: This header parameter is used to indicate the algorithm used alg: This header parameter is used to indicate the algorithm used
for the security processing. This header parameter MUST be for the security processing. This header parameter MUST be
authenticated where the ability to do so exists. This support is authenticated where the ability to do so exists. This support is
provided by AEAD algorithms or construction (COSE_Sign, provided by AEAD algorithms or construction (e.g. COSE_Sign and
COSE_Sign1, COSE_Mac, and COSE_Mac0). This authentication can be COSE_Mac0). This authentication can be done either by placing the
done either by placing the header parameter in the protected header parameter in the protected header parameter bucket or as
header parameter bucket or as part of the externally supplied part of the externally supplied data Section 4.3). The value is
data. The value is taken from the "COSE Algorithms" registry (see taken from the "COSE Algorithms" registry (see [COSE.Algorithms]).
[COSE.Algorithms]).
crit: This header parameter is used to indicate which protected crit: This header parameter is used to indicate which protected
header parameters an application that is processing a message is header parameters an application that is processing a message is
required to understand. Header parameters defined in this required to understand. Header parameters defined in this
document do not need to be included as they should be understood document do not need to be included as they should be understood
by all implementations. When present, this the 'crit' header by all implementations. When present, this the 'crit' header
parameter MUST be placed in the protected header parameter bucket. parameter MUST be placed in the protected header parameter bucket.
The array MUST have at least one value in it. The array MUST have at least one value in it.
Not all header parameter labels need to be included in the 'crit' Not all header parameter labels need to be included in the 'crit'
header parameter. The rules for deciding which header parameters header parameter. The rules for deciding which header parameters
are placed in the array are: are placed in the array are:
* Integer labels in the range of 0 to 7 SHOULD be omitted. * Integer labels in the range of 0 to 7 SHOULD be omitted.
* Integer labels in the range -1 to -128 can be omitted as they * Integer labels in the range -1 to -128 can be omitted.
are algorithm dependent. If an application can correctly Algorithms can assign labels in this range where the ability to
process an algorithm, it can be assumed that it will correctly process the content of the label is considered to be core to
process all of the common header parameters associated with implementing the algorithm. Algorithms can assign labels
that algorithm. Integer labels in the range -129 to -65536 outside of this range where the ability to process the content
SHOULD be included as these would be less common header of the label is not considered to be core, but needs to be
parameters that might not be generally supported. understood to correctly process this instance. Integer labels
in the range -129 to -65536 SHOULD be included as these would
be less common header parameters that might not be generally
supported.
* Labels for header parameters required for an application MAY be * Labels for header parameters required for an application MAY be
omitted. Applications should have a statement if the label can omitted. Applications should have a statement if the label can
be omitted. be omitted.
The header parameters indicated by 'crit' can be processed by The header parameters indicated by 'crit' can be processed by
either the security library code or an application using a either the security library code or an application using a
security library; the only requirement is that the header security library; the only requirement is that the header
parameter is processed. If the 'crit' value list includes a label parameter is processed. If the 'crit' value list includes a label
for which the header parameter is not in the protected header for which the header parameter is not in the protected header
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portion can be changed with each message (Partial IV). This field portion can be changed with each message (Partial IV). This field
is used to carry a value that causes the IV to be changed for each is used to carry a value that causes the IV to be changed for each
message. The Partial IV can be placed in the unprotected bucket message. The Partial IV can be placed in the unprotected bucket
as modifying the value will cause the decryption to yield as modifying the value will cause the decryption to yield
plaintext that is readily detectable as garbled. The plaintext that is readily detectable as garbled. The
'Initialization Vector' and 'Partial Initialization Vector' header 'Initialization Vector' and 'Partial Initialization Vector' header
parameters MUST NOT both be present in the same security layer. parameters MUST NOT both be present in the same security layer.
The message IV is generated by the following steps: The message IV is generated by the following steps:
1. Left-pad the Partial IV with zeros to the length of IV. 1. Left-pad the Partial IV with zeros to the length of IV
(determined by the algorithm).
2. XOR the padded Partial IV with the context IV. 2. XOR the padded Partial IV with the context IV.
counter signature: This header parameter holds one or more counter counter signature: This header parameter holds one or more counter
signature values. Counter signatures provide a method of having a signature values. Counter signatures provide a method of having a
second party sign some data. The counter signature header second party sign some data. The counter signature header
parameter can occur as an unprotected attribute in any of the parameter can occur as an unprotected attribute in any of the
following structures: COSE_Sign1, COSE_Signature, COSE_Encrypt, following structures: COSE_Sign1, COSE_Signature, COSE_Encrypt,
COSE_recipient, COSE_Encrypt0, COSE_Mac, and COSE_Mac0. These COSE_recipient, COSE_Encrypt0, COSE_Mac, and COSE_Mac0. These
structures all have the same beginning elements, so that a structures all have the same beginning elements, so that a
consistent calculation of the counter signature can be computed. consistent calculation of the counter signature can be computed.
Details on counter signatures are found in Section 5. Details on counter signatures are found in Section 5.
+---------+-----+----------------+-----------------+----------------+ +=========+=====+================+=================+================+
| Name |Label| Value Type | Value Registry | Description | | Name |Label| Value Type | Value Registry | Description |
+=========+=====+================+=================+================+ +=========+=====+================+=================+================+
| alg | 1 | int / tstr | COSE Algorithms | Cryptographic | | alg | 1 | int / tstr | COSE Algorithms | Cryptographic |
| | | | registry |algorithm to use| | | | | registry |algorithm to use|
+---------+-----+----------------+-----------------+----------------+ +---------+-----+----------------+-----------------+----------------+
| crit | 2 | [+ label] | COSE Header |Critical header | | crit | 2 | [+ label] | COSE Header |Critical header |
| | | | Parameters |parameters to be| | | | | Parameters |parameters to be|
| | | | registry | understood | | | | | registry | understood |
+---------+-----+----------------+-----------------+----------------+ +---------+-----+----------------+-----------------+----------------+
| content | 3 | tstr / uint | CoAP Content- |Content type of | | content | 3 | tstr / uint | CoAP Content- |Content type of |
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be converted between each other; as the signature computation be converted between each other; as the signature computation
includes a parameter identifying which structure is being used, the includes a parameter identifying which structure is being used, the
converted structure will fail signature validation. converted structure will fail signature validation.
4.1. Signing with One or More Signers 4.1. Signing with One or More Signers
The COSE_Sign structure allows for one or more signatures to be The COSE_Sign structure allows for one or more signatures to be
applied to a message payload. Header parameters relating to the applied to a message payload. Header parameters relating to the
content and header parameters relating to the signature are carried content and header parameters relating to the signature are carried
along with the signature itself. These header parameters may be along with the signature itself. These header parameters may be
authenticated by the signature, or just present. An example of authenticated by the signature, or just present. An example of a
header a parameter about the content is the content type header header parameter about the content is the content type header
parameter. Examples of header parameters about the signature would parameter. Examples of header parameters about the signature would
be the algorithm and key used to create the signature and counter be the algorithm and key used to create the signature and counter
signatures. signatures.
RFC 5652 indicates that: RFC 5652 indicates that:
| When more than one signature is present, the successful validation | When more than one signature is present, the successful validation
| of one signature associated with a given signer is usually treated | of one signature associated with a given signer is usually treated
| as a successful signature by that signer. However, there are some | as a 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
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If the payload is not present in the message, the application is If the payload is not present in the message, the application is
required to supply the payload separately. The payload is wrapped required to supply the payload separately. The payload is wrapped
in a bstr to ensure that it is transported without changes. If in a bstr to ensure that it is transported without changes. If
the payload is transported separately ("detached content"), then a the payload is transported separately ("detached content"), then a
nil CBOR object is placed in this location, and it is the nil CBOR object is placed in this location, and it is the
responsibility of the application to ensure that it will be responsibility of the application to ensure that it will be
transported without changes. transported without changes.
Note: When a signature with a message recovery algorithm is used Note: When a signature with a message recovery algorithm is used
(Section 9.1), the maximum number of bytes that can be recovered (Section 9.1), the maximum number of bytes that can be recovered
is the length of the payload. The size of the payload is reduced is the length of the original payload. The size of the encoded
by the number of bytes that will be recovered. If all of the payload is reduced by the number of bytes that will be recovered.
bytes of the payload are consumed, then the payload is encoded as If all of the bytes of the original payload are consumed, then the
a zero-length byte string rather than as being absent. transmitted payload is encoded as a zero-length byte string rather
than as being absent.
signatures: This field is an array of signatures. Each signature is signatures: This field is an array of signatures. Each signature is
represented as a COSE_Signature structure. represented as a COSE_Signature structure.
The CDDL fragment that represents the above text for COSE_Sign The CDDL fragment that represents the above text for COSE_Sign
follows. follows.
COSE_Sign = [ COSE_Sign = [
Headers, Headers,
payload : bstr / nil, payload : bstr / nil,
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is not carried as part of the COSE object. The primary reason for is not carried as part of the COSE object. The primary reason for
supporting this can be seen by looking at the CoAP message structure supporting this can be seen by looking at the CoAP message structure
[RFC7252], where the facility exists for options to be carried before [RFC7252], where the facility exists for options to be carried before
the payload. Examples of data that can be placed in this location the payload. Examples of data that can be placed in this location
would be the CoAP code or CoAP options. If the data is in the would be the CoAP code or CoAP options. If the data is in the
headers of the CoAP message, then it is available for proxies to help headers of the CoAP message, then it is available for proxies to help
in performing its operations. For example, the Accept Option can be in performing its operations. For example, the Accept Option can be
used by a proxy to determine if an appropriate value is in the used by a proxy to determine if an appropriate value is in the
proxy's cache. But the sender can cause a failure at the server if a proxy's cache. But the sender can cause a failure at the server if a
proxy, or an attacker, changes the set of accept values by including proxy, or an attacker, changes the set of accept values by including
the field in the application-supplied data. the field in the externally supplied data.
This document describes the process for using a byte array of This document describes the process for using a byte array of
externally supplied authenticated data; the method of constructing externally supplied authenticated data; the method of constructing
the byte array is a function of the application. Applications that the byte array is a function of the application. Applications that
use this feature need to define how the externally supplied use this feature need to define how the externally supplied
authenticated data is to be constructed. Such a construction needs authenticated data is to be constructed. Such a construction needs
to take into account the following issues: to take into account the following issues:
* If multiple items are included, applications need to ensure that * If multiple items are included, applications need to ensure that
the same byte string cannot be produced if there are different the same byte string cannot be produced if there are different
inputs. This would occur by appending the text strings 'AB' and inputs. This would occur by concatenating the text strings 'AB'
'CDE' or by appending the text strings 'ABC' and 'DE'. This is and 'CDE' or by concatenating the text strings 'ABC' and 'DE'.
usually addressed by making fields a fixed width and/or encoding This is usually addressed by making fields a fixed width and/or
the length of the field as part of the output. Using options from encoding the length of the field as part of the output. Using
CoAP [RFC7252] as an example, these fields use a TLV structure so options from CoAP [RFC7252] as an example, these fields use a TLV
they can be concatenated without any problems. structure so they can be concatenated without any problems.
* If multiple items are included, an order for the items needs to be * If multiple items are included, an order for the items needs to be
defined. Using options from CoAP as an example, an application defined. Using options from CoAP as an example, an application
could state that the fields are to be ordered by the option could state that the fields are to be ordered by the option
number. number.
* Applications need to ensure that the byte string is going to be * Applications need to ensure that the byte string is going to be
the same on both sides. Using options from CoAP might give a the same on both sides. Using options from CoAP might give a
problem if the same relative numbering is kept. An intermediate problem if the same relative numbering is kept. An intermediate
node could insert or remove an option, changing how the relative node could insert or remove an option, changing how the relative
skipping to change at page 22, line 43 skipping to change at page 22, line 50
application data (external source). A Sig_structure is a CBOR array. application data (external source). A Sig_structure is a CBOR array.
The fields of the Sig_structure in order are: The fields of the Sig_structure in order are:
1. A context text string identifying the context of the signature. 1. A context text string identifying the context of the signature.
The context text string is: The context text string is:
"Signature" for signatures using the COSE_Signature structure. "Signature" for signatures using the COSE_Signature structure.
"Signature1" for signatures using the COSE_Sign1 structure. "Signature1" for signatures using the COSE_Sign1 structure.
"CounterSignature" for signatures used as counter signature "CounterSignature" for signatures using the
attributes. COSE_Countersignature structure.
"CounterSignature0" for signatures used as CounterSignature0 "CounterSignature0" for signatures used as
attributes. COSE_Countersignature0 structure.
2. The protected attributes from the body structure encoded in a 2. The protected attributes from the body structure encoded in a
bstr type. If there are no protected attributes, a zero-length bstr type. If there are no protected attributes, a zero-length
byte string is used. byte string is used.
3. The protected attributes from the signer structure encoded in a 3. The protected attributes from the signer structure encoded in a
bstr type. If there are no protected attributes, a zero-length bstr type. If there are no protected attributes, a zero-length
byte string is used. This field is omitted for the COSE_Sign1 byte string is used. This field is omitted for the COSE_Sign1
signature structure and CounterSignature0 attributes. signature structure and CounterSignature0 attributes.
4. The protected attributes from the application encoded in a bstr 4. The externally supplied data from the application encoded in a
type. If this field is not supplied, it defaults to a zero- bstr type. If this field is not supplied, it defaults to a zero-
length byte string. (See Section 4.3 for application guidance on length byte string. (See Section 4.3 for application guidance on
constructing this field.) constructing this field.)
5. The payload to be signed encoded in a bstr type. The payload is 5. The payload to be signed encoded in a bstr type. The payload is
placed here independent of how it is transported. placed here independent of how it is transported.
The CDDL fragment that describes the above text is: The CDDL fragment that describes the above text is:
Sig_structure = [ Sig_structure = [
context : "Signature" / "Signature1" / "CounterSignature" / context : "Signature" / "Signature1" / "CounterSignature" /
"CounterSignature0", "CounterSignature0",
body_protected : empty_or_serialized_map, body_protected : empty_or_serialized_map,
? sign_protected : empty_or_serialized_map, ? sign_protected : empty_or_serialized_map,
external_aad : bstr, external_aad : bstr,
payload : bstr payload : bstr
] ]
A countersignature, like a signature needs a well-defined byte
string. The process uses the same Sig_structure but fills it in
slightly differently. The signing and verification process takes in
the target information (COSE_Sign, COSE_Sign1, COSE_Mac, COSE_Mac0,
COSE_Encrypt, COSE_Encrypt0, COSE_Recipient, and
COSE_Countersignature), the signer information (COSE_Signature) and
the application data (external source). The target structure of the
countersignature needs to have all of it's cryptographic functions
finalized before the computing the signature. The fields of the
Sig_stucture in order are:
1. A context string identifing the context of the signature as
above.
2. The protected attributes from the target structure encoded in a
bstr type. If there are no protected attributes, a zero-length
byte string is used.
3. The protected attributes from the countersignture structure
encoded in a bstr type. If there are no protected attributes, a
zero-length byte string is used. This field is omitted when
computing the CounterSignature0 attributes.
4. The externally supplied data from the application encoded in a
bstr type. If this field is not supplied, it defaults to a zero-
length byte string. (See Section 4.3 for application guidance on
constructing this field.)
5. The payload from the target structure encoded in a bstr type.
The payload is placed here independent of how it is transported.
How to compute a signature: How to compute a signature:
1. Create a Sig_structure and populate it with the appropriate 1. Create a Sig_structure and populate it with the appropriate
fields. fields.
2. Create the value ToBeSigned by encoding the Sig_structure to a 2. Create the value ToBeSigned by encoding the Sig_structure to a
byte string, using the encoding described in Section 10. byte string, using the encoding described in Section 10.
3. Call the signature creation algorithm passing in K (the key to 3. Call the signature creation algorithm passing in K (the key to
sign with), alg (the algorithm to sign with), and ToBeSigned (the sign with), alg (the algorithm to sign with), and ToBeSigned (the
skipping to change at page 24, line 29 skipping to change at page 25, line 20
as witnessing that you have signed the document. Thus applying a as witnessing that you have signed the document. Thus applying a
counter signature to either the COSE_Signature or COSE_Sign1 objects counter signature to either the COSE_Signature or COSE_Sign1 objects
match this traditional definition. This document extends the context match this traditional definition. This document extends the context
of a counter signature to allow it to be applied to all of the of a counter signature to allow it to be applied to all of the
security structures defined. It needs to be noted that the counter security structures defined. It needs to be noted that the counter
signature needs to be treated as a separate operation from the signature needs to be treated as a separate operation from the
initial operation even if it is applied by the same user as is done initial operation even if it is applied by the same user as is done
in [I-D.ietf-core-groupcomm-bis]. in [I-D.ietf-core-groupcomm-bis].
COSE supports two different forms for counter signatures. Full COSE supports two different forms for counter signatures. Full
counter signatures use the structure COSE_Countersign. This is same counter signatures use the structure COSE_Countersignature. This is
structure as COSE_Signature and thus it can have protected same structure as COSE_Signature and thus it can have protected and
attributes, chained counter signatures and information about unprotected attributes, including chained counter signatures.
identifying the key. Abbreviated counter signatures use the Abbreviated counter signatures use the structure
structure COSE_Countersign1. This structure only contains the COSE_Countersignature0. This structure only contains the signature
signature value and nothing else. The structures cannot be converted value and nothing else. The structures cannot be converted between
between each other; as the signature computation includes a parameter each other; as the signature computation includes a parameter
identifying which structure is being used, the converted structure identifying which structure is being used, the converted structure
will fail signature validation. will fail signature validation.
COSE was designed for uniformity in how the data structures are COSE was designed for uniformity in how the data structures are
specified. One result of this is that for COSE one can expand the specified. One result of this is that for COSE one can expand the
concept of counter signatures beyond just the idea of signing a concept of counter signatures beyond just the idea of signing a
signature to being able to sign most of the structures without having signature to being able to sign most of the structures without having
to create a new signing layer. When creating a counter signature, to create a new signing layer. When creating a counter signature,
one needs to be clear about the security properties that result. one needs to be clear about the security properties that result.
When done on a COSE_Signature, the normal counter signature semantics When done on a COSE_Signature, the normal counter signature semantics
skipping to change at page 25, line 15 skipping to change at page 26, line 8
is what is desired, then one needs to apply a signature to the data is what is desired, then one needs to apply a signature to the data
and then encrypt that. It is always possible to construct cases and then encrypt that. It is always possible to construct cases
where the use of two different keys will appear to result in a where the use of two different keys will appear to result in a
successful decryption (the tag check success), but which produce two successful decryption (the tag check success), but which produce two
completely different plaintexts. This situation is not detectable by completely different plaintexts. This situation is not detectable by
a counter signature on the encrypted data. a counter signature on the encrypted data.
5.1. Full Counter Signatures 5.1. Full Counter Signatures
The COSE_Countersignature structure allows for the same set of The COSE_Countersignature structure allows for the same set of
capabilities of a COSE_Signature. This means that all of the capabilities as a COSE_Signature. This means that all of the
capabilities of a signature are duplicated with this structure. capabilities of a signature are duplicated with this structure.
Specifically, the counter signer does not need to be related to the Specifically, the counter signer does not need to be related to the
producer of what is being counter signed as key and algorithm producer of what is being counter signed as key and algorithm
identification can be placed in the counter signature attributes. identification can be placed in the counter signature attributes.
This also means that the counter signature can itself be counter This also means that the counter signature can itself be counter
signed. This is a feature required by protocols such as long-term signed. This is a feature required by protocols such as long-term
archiving services. More information on how this is used can be archiving services. More information on how counter signatures is
found in the evidence record syntax described in [RFC4998]. used can be found in the evidence record syntax described in
[RFC4998].
The full counter signature structure can be encoded as either tagged The full counter signature structure can be encoded as either tagged
or untagged depending on the context it is used in. A tagged or untagged depending on the context it is used in. A tagged
COSE_Countersign structure is identified by the CBOR tag TBD0. The COSE_Countersignature structure is identified by the CBOR tag TBD0.
CDDL fragment for full counter signatures is: The CDDL fragment for full counter signatures is:
COSE_CounterSignature_Tagged = #6.98(COSE_CounterSignature) COSE_Countersignature_Tagged = #6.9999(COSE_Countersignature)
COSE_CounterSignature = COSE_Signature COSE_Countersignature = COSE_Signature
COSE_CounterSignature = COSE_Countersignature
The details of the fields of a counter signature can be found in The details of the fields of a counter signature can be found in
Section 4.1. The process of creating and validating abbreviated Section 4.1. The process of creating and validating abbreviated
counter signatures is defined in Section 4.4. counter signatures is defined in Section 4.4.
An example of a counter signature on a signature can be found in An example of a counter signature on a signature can be found in
Appendix C.1.3. An example of a counter signature in an encryption Appendix C.1.3. An example of a counter signature in an encryption
object can be found in Appendix C.3.3. object can be found in Appendix C.3.3.
It should be noted that only a signature algorithm with appendix (see It should be noted that only a signature algorithm with appendix (see
skipping to change at page 26, line 17 skipping to change at page 27, line 5
Abbreviated counter signatures were designed primarily to deal with Abbreviated counter signatures were designed primarily to deal with
the problem of having encrypted group messaging, but still needing to the problem of having encrypted group messaging, but still needing to
know who originated the message. The objective was to keep the know who originated the message. The objective was to keep the
counter signature as small as possible while still providing the counter signature as small as possible while still providing the
needed security. For abbreviated counter signatures, there is no needed security. For abbreviated counter signatures, there is no
provision for any protected attributes related to the signing provision for any protected attributes related to the signing
operation. Instead, the parameters for computing or verifying the operation. Instead, the parameters for computing or verifying the
abbreviated counter signature are inferred from the same context used abbreviated counter signature are inferred from the same context used
to describe the encryption, signature, or MAC processing. to describe the encryption, signature, or MAC processing.
The CDDL fragment for the abbreviated counter signatures is:
COSE_Countersignature0 = bstr
The byte string representing the signature value is placed in the The byte string representing the signature value is placed in the
CounterSignature0 attribute. This attribute is then encoded as an CounterSignature0 attribute. This attribute is then encoded as an
unprotected header parameter. The attribute is defined below. unprotected header parameter. The attribute is defined below.
The process of creating and validating abbreviated counter signatures The process of creating and validating abbreviated counter signatures
is defined in Section 4.4. is defined in Section 4.4.
+-------------------+-------+-------+-------+-------------------+ +==================+=====+========================+=====+===========+
| Name | Label | Value | Value | Description | | Name |Label| Value Type |Value|Description|
| | | Type | | | +==================+=====+========================+=====+===========+
+===================+=======+=======+=======+===================+ |CounterSignature0 | 9 | COSE_Countersignature0 | |Abbreviated|
| CounterSignature0 | 9 | bstr | | Abbreviated | | | | | | Counter |
| | | | | Counter Signature | | | | | | Signature |
+-------------------+-------+-------+-------+-------------------+ +------------------+-----+------------------------+-----+-----------+
Table 4: Header Parameter for CounterSignature0 Table 4: Header Parameter for CounterSignature0
6. Encryption Objects 6. Encryption Objects
COSE supports two different encryption structures. COSE_Encrypt0 is COSE supports two different encryption structures. COSE_Encrypt0 is
used when a recipient structure is not needed because the key to be used when a recipient structure is not needed because the key to be
used is known implicitly. COSE_Encrypt is used the rest of the time. used is known implicitly. COSE_Encrypt is used the rest of the time.
This includes cases where there are multiple recipients or a This includes cases where there are multiple recipients or a
recipient algorithm other than direct (i.e. pre-shared secret) is recipient algorithm other than direct (i.e. pre-shared secret) is
skipping to change at page 30, line 27 skipping to change at page 31, line 21
"Mac_Recipient" for a recipient encoding to be placed in a "Mac_Recipient" for a recipient encoding to be placed in a
MACed message structure. MACed message structure.
"Rec_Recipient" for a recipient encoding to be placed in a "Rec_Recipient" for a recipient encoding to be placed in a
recipient structure. recipient structure.
2. The protected attributes from the body structure encoded in a 2. The protected attributes from the body structure encoded in a
bstr type. If there are no protected attributes, a zero-length bstr type. If there are no protected attributes, a zero-length
byte string is used. byte string is used.
3. The protected attributes from the application encoded in a bstr 3. The externally supplied data from the application encoded in a
type. If this field is not supplied, it defaults to a zero- bstr type. If this field is not supplied, it defaults to a zero-
length byte string. (See Section 4.3 for application guidance on length byte string. (See Section 4.3 for application guidance on
constructing this field.) constructing this field.)
The CDDL fragment that describes the above text is: The CDDL fragment that describes the above text is:
Enc_structure = [ Enc_structure = [
context : "Encrypt" / "Encrypt0" / "Enc_Recipient" / context : "Encrypt" / "Encrypt0" / "Enc_Recipient" /
"Mac_Recipient" / "Rec_Recipient", "Mac_Recipient" / "Rec_Recipient",
protected : empty_or_serialized_map, protected : empty_or_serialized_map,
external_aad : bstr external_aad : bstr
skipping to change at page 36, line 8 skipping to change at page 37, line 8
in order are: in order are:
1. A context text string that identifies the structure that is being 1. A context text string that identifies the structure that is being
encoded. This context text string is "MAC" for the COSE_Mac encoded. This context text string is "MAC" for the COSE_Mac
structure. This context text string is "MAC0" for the COSE_Mac0 structure. This context text string is "MAC0" for the COSE_Mac0
structure. structure.
2. The protected attributes from the COSE_MAC structure. If there 2. The protected attributes from the COSE_MAC structure. If there
are no protected attributes, a zero-length bstr is used. are no protected attributes, a zero-length bstr is used.
3. The protected attributes from the application encoded as a bstr 3. The externally supplied data from the application encoded as a
type. If this field is not supplied, it defaults to a zero- bstr type. If this field is not supplied, it defaults to a zero-
length byte string. (See Section 4.3 for application guidance on length byte string. (See Section 4.3 for application guidance on
constructing this field.) constructing this field.)
4. The payload to be MACed encoded in a bstr type. The payload is 4. The payload to be MACed encoded in a bstr type. The payload is
placed here independent of how it is transported. placed here independent of how it is transported.
The CDDL fragment that corresponds to the above text is: The CDDL fragment that corresponds to the above text is:
MAC_structure = [ MAC_structure = [
context : "MAC" / "MAC0", context : "MAC" / "MAC0",
skipping to change at page 37, line 16 skipping to change at page 38, line 16
alg (the algorithm to MAC with), and ToBeMaced (the value to alg (the algorithm to MAC with), and ToBeMaced (the value to
compute the MAC on). compute the MAC on).
5. Compare the MAC value to the 'tag' field of the COSE_Mac or 5. Compare the MAC value to the 'tag' field of the COSE_Mac or
COSE_Mac0 structure. COSE_Mac0 structure.
8. Key Objects 8. Key Objects
A COSE Key structure is built on a CBOR map. The set of common A COSE Key structure is built on a CBOR map. The set of common
parameters that can appear in a COSE Key can be found in the IANA parameters that can appear in a COSE Key can be found in the IANA
"COSE Key Common Parameters" registry (Section 12.4). Additional "COSE Key Common Parameters" registry (Section 12.3). Additional
parameters defined for specific key types can be found in the IANA parameters defined for specific key types can be found in the IANA
"COSE Key Type Parameters" registry ([COSE.KeyParameters]). "COSE Key Type Parameters" registry ([COSE.KeyParameters]).
A COSE Key Set uses a CBOR array object as its 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 COSE Key Set MUST have values of the array elements are COSE Keys. A COSE Key Set MUST have
at least one element in the array. Examples of COSE Key Sets can be at least one element in the array. Examples of COSE Key Sets can be
found in Appendix C.7. found in Appendix C.7.
Each element in a COSE Key Set MUST be processed independently. If Each element in a COSE Key Set MUST be processed independently. If
one element in a COSE Key Set is either malformed or uses a key that one element in a COSE Key Set is either malformed or uses a key that
skipping to change at page 38, line 5 skipping to change at page 39, line 5
COSE_KeySet = [+COSE_Key] COSE_KeySet = [+COSE_Key]
8.1. COSE Key Common Parameters 8.1. COSE Key Common Parameters
This document defines a set of common parameters for a COSE Key This document defines a set of common parameters for a COSE Key
object. Table 5 provides a summary of the parameters defined in this object. Table 5 provides a summary of the parameters defined in this
section. There are also parameters that are defined for specific key section. There are also parameters that are defined for specific key
types. Key-type-specific parameters can be found in types. Key-type-specific parameters can be found in
[I-D.ietf-cose-rfc8152bis-algs]. [I-D.ietf-cose-rfc8152bis-algs].
+---------+-------+--------+------------+--------------------+ +=========+=======+========+============+====================+
| Name | Label | CBOR | Value | Description | | Name | Label | CBOR | Value | Description |
| | | Type | Registry | | | | | Type | Registry | |
+=========+=======+========+============+====================+ +=========+=======+========+============+====================+
| kty | 1 | tstr / | COSE Key | Identification of | | kty | 1 | tstr / | COSE Key | Identification of |
| | | int | Types | the key type | | | | int | Types | the key type |
+---------+-------+--------+------------+--------------------+ +---------+-------+--------+------------+--------------------+
| kid | 2 | bstr | | Key identification | | kid | 2 | bstr | | Key identification |
| | | | | value -- match to | | | | | | value -- match to |
| | | | | kid in message | | | | | | kid in message |
+---------+-------+--------+------------+--------------------+ +---------+-------+--------+------------+--------------------+
skipping to change at page 39, line 10 skipping to change at page 40, line 5
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 byte string to a value computed on the public portion of provided byte string to a value computed on the public portion of
the key. This field is intended for matching against a 'kid' the key. This field is intended for matching against a 'kid'
parameter in a message in order to filter down the set of keys parameter in a message in order to filter down the set of keys
that need to be checked. that need to be checked. The value of the identifier is not a
unique value and can occur in other key objects, even for
different keys.
key_ops: This parameter is defined to restrict the set of operations key_ops: This parameter is defined to restrict the set of operations
that a key is to be used for. The value of the field is an array that a key is to be used for. The value of the field is an array
of values from Table 6. Algorithms define the values of key ops of values from Table 6. Algorithms define the values of key ops
that are permitted to appear and are required for specific that are permitted to appear and are required for specific
operations. The set of values matches that in [RFC7517] and operations. The set of values matches that in [RFC7517] and
[W3C.WebCrypto]. [W3C.WebCrypto].
Base IV: This parameter is defined to carry the base portion of an Base IV: This parameter is defined to carry the base portion of an
IV. It is designed to be used with the Partial IV header IV. It is designed to be used with the Partial IV header
parameter defined in Section 3.1. This field provides the ability parameter defined in Section 3.1. This field provides the ability
to associate a Partial IV with a key that is then modified on a to associate a Base IV with a key that is then modified on a per
per message basis with the Partial IV. message basis with the Partial IV.
Extreme care needs to be taken when using a Base IV in an Extreme care needs to be taken when using a Base IV in an
application. Many encryption algorithms lose security if the same application. Many encryption algorithms lose security if the same
IV is used twice. IV is used twice.
If different keys are derived for each sender, using the same Base If different keys are derived for each sender, starting at the
IV with Partial IVs starting at zero is likely to ensure that the same Base IV is likely to satisfy this condition. If the same key
IV would not be used twice for a single key. If different keys is used for multiple senders, then the application needs to
are derived for each sender, starting at the same Base IV is provide for a method of dividing the IV space up between the
likely to satisfy this condition. If the same key is used for senders. This could be done by providing a different base point
multiple senders, then the application needs to provide for a to start from or a different Partial IV to start with and
method of dividing the IV space up between the senders. This restricting the number of messages to be sent before rekeying.
could be done by providing a different base point to start from or
a different Partial IV to start with and restricting the number of
messages to be sent before rekeying.
+---------+-------+----------------------------------------------+ +=========+=======+==============================================+
| Name | Value | Description | | Name | Value | Description |
+=========+=======+==============================================+ +=========+=======+==============================================+
| sign | 1 | The key is used to create signatures. | | sign | 1 | The key is used to create signatures. |
| | | Requires private key fields. | | | | Requires private key fields. |
+---------+-------+----------------------------------------------+ +---------+-------+----------------------------------------------+
| verify | 2 | The key is used for verification of | | verify | 2 | The key is used for verification of |
| | | signatures. | | | | signatures. |
+---------+-------+----------------------------------------------+ +---------+-------+----------------------------------------------+
| encrypt | 3 | The key is used for key transport | | encrypt | 3 | The key is used for key transport |
| | | encryption. | | | | encryption. |
skipping to change at page 40, line 46 skipping to change at page 41, line 46
| verify | | | | verify | | |
+---------+-------+----------------------------------------------+ +---------+-------+----------------------------------------------+
Table 6: Key Operation Values Table 6: Key Operation Values
9. Taxonomy of Algorithms used by COSE 9. Taxonomy of Algorithms used by COSE
In this section, a taxonomy of the different algorithm types that can In this section, a taxonomy of the different algorithm types that can
be used in COSE is laid out. This taxonomy should not be considered be used in COSE is laid out. This taxonomy should not be considered
to be exhaustive. New algorithms will be created which will not fit to be exhaustive. New algorithms will be created which will not fit
into this taxonomy. If this occurs, then new documents addressing into this taxonomy.
this new algorithms are going to be needed.
9.1. Signature Algorithms 9.1. Signature Algorithms
Signature algorithms provide data origination and data integrity Signature algorithms provide data origination and data integrity
services. Data origination provides the ability to infer who services. Data origination provides the ability to infer who
originated the data based on who signed the data. Data integrity originated the data based on who signed the data. Data integrity
provides the ability to verify that the data has not been modified provides the ability to verify that the data has not been modified
since it was signed. since it was signed.
There are two signature algorithm schemes. The first is signature There are two signature algorithm schemes. The first is signature
skipping to change at page 43, line 32 skipping to change at page 44, line 32
is created by a good random number generator. is created by a good random number generator.
* Secrets that are not uniformly random: This is type of secret that * Secrets that are not uniformly random: This is type of secret that
is created by operations like key agreement. is created by operations like key agreement.
* Secrets that are not random: This is the type of secret that * Secrets that are not random: This is the type of secret that
people generate for things like passwords. people generate for things like passwords.
General KDFs work well with the first type of secret, can do General KDFs work well with the first type of secret, can do
reasonably well with the second type of secret, and generally do reasonably well with the second type of secret, and generally do
poorly with the last type of secret. Functions like PBES2 [RFC8018] poorly with the last type of secret. Functions like Argon2
need to be used for non-random secrets. [I-D.irtf-cfrg-argon2] need to be used for non-random secrets.
The same KDF can be set up to deal with the first two types of The same KDF can be set up to deal with the first two types of
secrets in a different way. The KDF defined in section 5.1 of secrets in a different way. The KDF defined in section 5.1 of
[I-D.ietf-cose-rfc8152bis-algs] is such a function. This is [I-D.ietf-cose-rfc8152bis-algs] is such a function. This is
reflected in the set of algorithms defined around the HMAC-based reflected in the set of algorithms defined around the HMAC-based
Extract-and-Expand Key Derivation Function (HKDF). Extract-and-Expand Key Derivation Function (HKDF).
When using KDFs, one component that is included is context When using KDFs, one component that is included is context
information. Context information is used to allow for different information. Context information is used to allow for different
keying information to be derived from the same secret. The use of keying information to be derived from the same secret. The use of
skipping to change at page 44, line 50 skipping to change at page 45, line 50
encrypted by a shared secret between the sender and the recipient. encrypted by a shared secret between the sender and the recipient.
All of the currently defined key wrap algorithms for COSE are AE All of the currently defined key wrap algorithms for COSE are AE
algorithms. Key wrap mode is considered to be superior to direct algorithms. Key wrap mode is considered to be superior to direct
encryption if the system has any capability for doing random key encryption if the system has any capability for doing random key
generation. This is because the shared key is used to wrap random generation. This is because the shared key is used to wrap random
data rather than data that has some degree of organization and may in data rather than data that has some degree of organization and may in
fact be repeating the same content. The use of key wrap loses the fact be repeating the same content. The use of key wrap loses the
weak data origination that is provided by the direct encryption weak data origination that is provided by the direct encryption
algorithms. algorithms.
The COSE_Encrypt structure for the recipient is organized as follows: The COSE_Recipient structure for the recipient is organized as
follows:
* The 'protected' field MUST be absent if the key wrap algorithm is * The 'protected' field MUST be absent if the key wrap algorithm is
an AE algorithm. an AE algorithm.
* The 'recipients' field is normally absent, but can be used. * The 'recipients' field is normally absent, but can be used.
Applications MUST deal with a recipient field being present that Applications MUST deal with a recipient field being present that
has an unsupported algorithm, not being able to decrypt that has an unsupported algorithm. Failing to decrypt that specific
recipient is an acceptable way of dealing with it. Failing to recipient is an acceptable way of dealing with it. Failing to
process the message is not an acceptable way of dealing with it. process the message is not an acceptable way of dealing with it.
* The plaintext to be encrypted is the key from next layer down * The plaintext to be encrypted is the key from next layer down
(usually the content layer). (usually the content layer).
* At a minimum, the 'unprotected' field MUST contain the 'alg' * At a minimum, the 'unprotected' field MUST contain the 'alg'
header parameter and SHOULD contain a header parameter identifying header parameter and SHOULD contain a header parameter identifying
the shared secret. the shared secret.
9.5.3. Key Transport 9.5.3. Key Transport
Key transport mode is also called key encryption mode in some Key transport mode is also called key encryption mode in some
standards. Key transport mode differs from key wrap mode in that it standards. Key transport mode differs from key wrap mode in that it
uses an asymmetric encryption algorithm rather than a symmetric uses an asymmetric encryption algorithm rather than a symmetric
encryption algorithm to protect the key. A set of key transport encryption algorithm to protect the key. A set of key transport
algorithms are defined in [RFC8230]. algorithms are defined in [RFC8230].
When using a key transport algorithm, the COSE_Encrypt structure for When using a key transport algorithm, the COSE_Recipient structure
the recipient is organized as follows: for the recipient is organized as follows:
* The 'protected' field MUST be absent. * The 'protected' field MUST be absent.
* The plaintext to be encrypted is the key from the next layer down * The plaintext to be encrypted is the key from the next layer down
(usually the content layer). (usually the content layer).
* At a minimum, the 'unprotected' field MUST contain the 'alg' * At a minimum, the 'unprotected' field MUST contain the 'alg'
header parameter and SHOULD contain a parameter identifying the header parameter and SHOULD contain a parameter identifying the
asymmetric key. asymmetric key.
skipping to change at page 46, line 4 skipping to change at page 47, line 4
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 is Diffie-Hellman, but The most commonly used key agreement algorithm is Diffie-Hellman, but
other variants exist. Since COSE is designed for a store and forward other variants exist. Since COSE is designed for a store and forward
environment rather than an online environment, many of the DH environment rather than an online environment, many of the DH
variants cannot be used as the receiver of the message cannot provide variants cannot be used as the receiver of the message cannot provide
any dynamic key material. One side effect of this is that perfect any dynamic key material. One side effect of this is that forward
forward secrecy (see [RFC4949]) is not achievable. A static key will secrecy (see [RFC4949]) is not achievable. A static key will always
always be used for the receiver of the COSE object. be used for the receiver of the COSE object.
Two variants of DH that are supported are: Two variants of DH that are supported are:
Ephemeral-Static (ES) DH: where the sender of the message creates Ephemeral-Static (ES) DH: where the sender of the message creates
a one-time DH key and uses a static key for the recipient. The a one-time DH key and uses a static key for the recipient. The
use of the ephemeral sender key means that no additional random use of the ephemeral sender key means that no additional random
input is needed as this is randomly generated for each message. input is needed as this is randomly generated for each message.
Static-Static (SS) DH: where a static key is used for both the Static-Static (SS) DH: where a static key is used for both the
sender and the recipient. The use of static keys allows for the sender and the recipient. The use of static keys allows for the
skipping to change at page 46, line 28 skipping to change at page 47, line 28
message. When static-static key agreement is used, then some message. When static-static key agreement is used, then some
piece of unique data for the KDF is required to ensure that a piece of unique data for the KDF is required to ensure that a
different key is created for each message. different key is created for each message.
When direct key agreement mode is used, there MUST be only one When direct key agreement mode is used, there MUST be only one
recipient in the message. This method creates the key directly, and recipient in the message. This method creates the key directly, and
that makes it difficult to mix with additional recipients. If that makes it difficult to mix with additional recipients. If
multiple recipients are needed, then the version with key wrap needs multiple recipients are needed, then the version with key wrap needs
to be used. to be used.
The COSE_Encrypt structure for the recipient is organized as follows: The COSE_Recipient structure for the recipient is organized as
follows:
* At a minimum, headers MUST contain the 'alg' header parameter and * At a minimum, headers MUST contain the 'alg' header parameter and
SHOULD contain a header parameter identifying the recipient's SHOULD contain a header parameter identifying the recipient's
asymmetric key. asymmetric key.
* The headers SHOULD identify the sender's key for the static-static * The headers SHOULD identify the sender's key for the static-static
versions and MUST contain the sender's ephemeral key for the versions and MUST contain the sender's ephemeral key for the
ephemeral-static versions. ephemeral-static versions.
9.5.5. Key Agreement with Key Wrap 9.5.5. Key Agreement with Key Wrap
Key Agreement with Key Wrap uses a randomly generated CEK. The CEK Key Agreement with Key Wrap uses a randomly generated CEK. The CEK
is then encrypted using a key wrap algorithm and a key derived from is then encrypted using a key wrap algorithm and a key derived from
the shared secret computed by the key agreement algorithm. The the shared secret computed by the key agreement algorithm. The
function for this would be: function for this would be:
encryptedKey = KeyWrap(KDF(DH-Shared, context), CEK) encryptedKey = KeyWrap(KDF(DH-Shared, context), CEK)
The COSE_Encrypt structure for the recipient is organized as follows: The COSE_Recipient structure for the recipient is organized as
follows:
* The 'protected' field is fed into the KDF context structure. * The 'protected' field is fed into the KDF context structure.
* The plaintext to be encrypted is the key from the next layer down * The plaintext to be encrypted is the key from the next layer down
(usually the content layer). (usually the content layer).
* The 'alg' header parameter MUST be present in the layer. * The 'alg' header parameter MUST be present in the layer.
* A header parameter identifying the recipient's key SHOULD be * A header parameter identifying the recipient's key SHOULD be
present. A header parameter identifying the sender's key SHOULD present. A header parameter identifying the sender's key SHOULD
be present. be present.
10. CBOR Encoding Restrictions 10. CBOR Encoding Restrictions
The document limits the restrictions it imposes on the CBOR Encoder This document limits the restrictions it imposes on how the CBOR
needs to work. Encoder needs to work. It has been narrowed down to the following
restrictions:
* The restriction applies to the encoding of the Sig_structure, the * The restriction applies to the encoding of the Sig_structure, the
Enc_structure, and the MAC_structure. Enc_structure, and the MAC_structure.
* Encoding MUST be done using definite lengths and values MUST be * Encoding MUST be done using definite lengths and values MUST be
the minimum possible length. This means that the integer 1 is the minimum possible length. This means that the integer 1 is
encoded as "0x01" and not "0x1801". encoded as "0x01" and not "0x1801".
* Applications MUST NOT generate messages with the same label used * Applications MUST NOT generate messages with the same label used
twice as a key in a single map. Applications MUST NOT parse and twice as a key in a single map. Applications MUST NOT parse and
skipping to change at page 48, line 33 skipping to change at page 49, line 33
* Applications need to determine the set of security algorithms that * Applications need to determine the set of security algorithms that
are to be used. When selecting the algorithms to be used as the are to be used. When selecting the algorithms to be used as the
mandatory-to-implement set, consideration should be given to mandatory-to-implement set, consideration should be given to
choosing different types of algorithms when two are chosen for a choosing different types of algorithms when two are chosen for a
specific purpose. An example of this would be choosing HMAC- specific purpose. An example of this would be choosing HMAC-
SHA512 and AES-CMAC as different MAC algorithms; the construction SHA512 and AES-CMAC as different MAC algorithms; the construction
is vastly different between these two algorithms. This means that is vastly different between these two algorithms. This means that
a weakening of one algorithm would be unlikely to lead to a a weakening of one algorithm would be unlikely to lead to a
weakening of the other algorithms. Of course, these algorithms do weakening of the other algorithms. Of course, these algorithms do
not provide the same level of security and thus may not be not provide the same level of security and thus may not be
comparable for the desired security functionality. comparable for the desired security functionality. Additional
guidence can be found in [BCP201].
* Applications may need to provide some type of negotiation or * Applications may need to provide some type of negotiation or
discovery method if multiple algorithms or message structures are discovery method if multiple algorithms or message structures are
permitted. The method can be as simple as requiring pre- permitted. The method can be as simple as requiring pre-
configuration of the set of algorithms to providing a discovery configuration 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 that applications could different ways to approach the problem that applications could
follow: follow:
- Advertising in the message (S/MIME capabilities) [RFC5751]. - Advertising in the message (S/MIME capabilities) [RFC5751].
skipping to change at page 49, line 22 skipping to change at page 50, line 22
IANA assigned tags in the "CBOR Tags" registry as part of processing IANA assigned tags in the "CBOR Tags" registry as part of processing
[RFC8152]. IANA is requested to update the references from [RFC8152] [RFC8152]. IANA is requested to update the references from [RFC8152]
to this document. to this document.
IANA is requested to register a new tag for the CounterSignature IANA is requested to register a new tag for the CounterSignature
type. type.
* Tag: TBD0 * Tag: TBD0
* Data Item: COSE_Signature * Data Item: COSE_Countersignature
* Semantics: COSE standalone counter signature * Semantics: COSE standalone counter signature
* Reference: [[this document]] * Reference: [[this document]]
12.2. COSE Header Parameters Registry 12.2. COSE Header Parameters Registry
IANA created a registry titled "COSE Header Parameters" as part of IANA created a registry titled "COSE Header Parameters" as part of
processing [RFC8152]. The registry has been created to use the processing [RFC8152]. IANA is requested to update the reference for
"Expert Review Required" registration procedure [RFC8126]. entries in the table from [RFC8152] to this document.
IANA is requested to update the reference for entries in the table
from [RFC8152] to this document. This document does not update the
expert review guidelines provided in [RFC8152].
12.3. COSE Header Algorithm Parameters Registry
IANA created a registry titled "COSE Header Algorithm Parameters" as Additionally, the type for the attribute CounterSignature0 is to be
part of processing [RFC8152]. The registry has been created to use updated from 'bstr' to 'COSE_Countersignature0'.
the "Expert Review Required" registration procedure [RFC8126].
IANA is requested to update the references from [RFC8152] to this IANA is requested to update the pointer for expert rview to [[this
document. This document does not update the expert review guidelines document]].
provided in [RFC8152].
12.4. COSE Key Common Parameters Registry 12.3. COSE Key Common Parameters Registry
IANA created a registry titled "COSE Key Common Parameters" as part IANA created a registry titled "COSE Key Common Parameters" as part
of the processing of [RFC8152]. The registry has been created to use of the processing of [RFC8152]. IANA is requested to update the
the "Expert Review Required" registration procedure [RFC8126]. reference for entries in the table from [RFC8152] to this document.
IANA is requested to update the reference for entries in the table
from [RFC8152] to this document. This document does not update the
expert review guidelines provided in [RFC8152].
12.5. Media Type Registrations IANA is requested to update the pointer for expert rview to [[this
document]].
12.5.1. COSE Security Message 12.4. Media Type Registrations
12.4.1. COSE Security Message
This section registers the 'application/cose' media type in the This section registers the 'application/cose' media type in the
"Media Types" registry. These media types are used to indicate that "Media Types" registry. These media types are used to indicate that
the content is a COSE message. the content is a COSE message.
Type name: application Type name: application
Subtype name: cose Subtype name: cose
Required parameters: N/A Required parameters: N/A
skipping to change at page 51, line 4 skipping to change at page 51, line 46
- 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
12.5.2. COSE Key Media Type 12.4.2. COSE Key Media Type
This section registers the 'application/cose-key' and 'application/ This section registers the 'application/cose-key' and 'application/
cose-key-set' media types in the "Media Types" registry. These media cose-key-set' media types in the "Media Types" registry. These media
types are used to indicate, respectively, that content is a COSE_Key types are used to indicate, respectively, that content is a COSE_Key
or COSE_KeySet object. or COSE_KeySet object.
The template for registering 'application/cose-key' is: The template for registering 'application/cose-key' is:
Type name: application Type name: application
skipping to change at page 53, line 4 skipping to change at page 53, line 45
Additional information: Additional information:
- Deprecated alias names for this type: N/A - Deprecated alias names for this type: N/A
- 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
12.6. CoAP Content-Formats Registry 12.5. CoAP Content-Formats Registry
IANA added the following entries to the "CoAP Content-Formats" IANA added entries to the "CoAP Content-Formats" registry while
registry while processing [RFC8152]. IANA is requested to update the processing [RFC8152]. IANA is requested to update the reference
reference value from [RFC8152] to [[This Document]]. value from [RFC8152] to [[This Document]].
12.6. Expert Review Instructions
All of the IANA registries established by [RFC8152] are, at least in
part, defined as expert review. This section gives some general
guidelines for what the experts should be looking for, but they are
being designated as experts for a reason, so they should be given
substantial latitude.
Expert reviewers should take into consideration the following points:
* Point squatting should be discouraged. Reviewers are encouraged
to get sufficient information for registration requests to ensure
that the usage is not going to duplicate one that is already
registered, and that the point is likely to be used in
deployments. The zones tagged as private use are intended for
testing purposes and closed environments; code points in other
ranges should not be assigned for testing.
* Specifications are required for the standards track range of point
assignment. Specifications should exist for specification
required ranges, but early assignment before a specification is
available is considered to be permissible. Specifications are
needed for the first-come, first-serve range if they are expected
to be used outside of closed environments in an interoperable way.
When specifications are not provided, the description provided
needs to have sufficient information to identify what the point is
being used for.
* Experts should take into account the expected usage of fields when
approving point assignment. The fact that there is a range for
standards track documents does not mean that a standards track
document cannot have points assigned outside of that range. The
length of the encoded value should be weighed against how many
code points of that length are left, the size of device it will be
used on, and the number of code points left that encode to that
size.
* When algorithms are registered, vanity registrations should be
discouraged. One way to do this is to require registrations to
provide additional documentation on security analysis of the
algorithm. Another thing that should be considered is requesting
an opinion on the algorithm from the Crypto Forum Research Group
(CFRG). Algorithms that do not meet the security requirements of
the community and the messages structures should not be
registered.
13. Security Considerations 13. Security Considerations
There are a number of security considerations that need to be taken There are a number of security considerations that need to be taken
into account by implementers of this specification. The security into account by implementers of this specification. While some
considerations that are specific to an individual algorithm are
placed next to the description of the algorithm. While some
considerations have been highlighted here, additional considerations considerations have been highlighted here, additional considerations
may be found in the documents listed in the references. may be found in the documents listed in the references.
Implementations need to protect the private key material for any Implementations need to protect the private key material for any
individuals. There are some cases that need to be highlighted on individuals. There are some cases that need to be highlighted on
this issue. this issue.
* Using the same key for two different algorithms can leak * Using the same key for two different algorithms can leak
information about the key. It is therefore recommended that keys information about the key. It is therefore recommended that keys
be restricted to a single algorithm. be restricted to a single algorithm.
skipping to change at page 54, line 47 skipping to change at page 56, line 35
* Have the restrictions associated with the key, such as algorithm * Have the restrictions associated with the key, such as algorithm
or freshness, been checked and are they correct? or freshness, been checked and are they correct?
* Is the request something that is reasonable, given the current * Is the request something that is reasonable, given the current
state of the application? state of the application?
* Have any security considerations that are part of the message been * Have any security considerations that are part of the message been
enforced (as specified by the application or 'crit' header enforced (as specified by the application or 'crit' header
parameter)? parameter)?
There are a large number of algorithms presented in One area that has been getting exposure is traffic analysis of
[I-D.ietf-cose-rfc8152bis-algs] that use nonce values. Nonces encrypted messages based on the length of the message. This
generally have some type of restriction on their values. Generally a specification does not provide for a uniform method of providing
nonce needs to be a unique value either for a key or for some other
conditions. In all of these cases, there is no known requirement on
the nonce being both unique and unpredictable; under these
circumstances, it's reasonable to use a counter for creation of the
nonce. In cases where one wants the pattern of the nonce to be
unpredictable as well as unique, one can use a key created for that
purpose and encrypt the counter to produce the nonce value.
One area that has been starting to get exposure is doing traffic
analysis of encrypted messages based on the length of the message.
This specification does not provide for a uniform method of providing
padding as part of the message structure. An observer can padding as part of the message structure. An observer can
distinguish between two different messages (for example, 'YES' and distinguish between two different messages (for example, 'YES' and
'NO') based on the length for all of the content encryption 'NO') based on the length for all of the content encryption
algorithms that are defined in [I-D.ietf-cose-rfc8152bis-algs] algorithms that are defined in [I-D.ietf-cose-rfc8152bis-algs]
document. This means that it is up to the applications to document document. This means that it is up to the applications to document
how content padding is to be done in order to prevent or discourage how content padding is to be done in order to prevent or discourage
such analysis. (For example, the text strings could be defined as such analysis. (For example, the text strings could be defined as
'YES' and 'NO '.) 'YES' and 'NO '.)
14. Implementation Status 14. Implementation Status
skipping to change at page 56, line 14 skipping to change at page 57, line 41
* Implementation Location: https://github.com/cose-wg * Implementation Location: https://github.com/cose-wg
* Primary Maintainer: Jim Schaad * Primary Maintainer: Jim Schaad
* Languages: There are three different languages that are currently * Languages: There are three different languages that are currently
supported: Java, C# and C. supported: Java, C# and C.
* Cryptography: The Java and C# libraries use Bouncy Castle to * Cryptography: The Java and C# libraries use Bouncy Castle to
provide the required cryptography. The C version uses OPENSSL provide the required cryptography. The C version uses OPENSSL
Version 1.0 for the cryptography. Version 1.1 for the cryptography.
* Coverage: The C version currently does not have full counter sign * Coverage: The C version currently does not have full counter sign
support. The other two versions do. They do have support to support. The other two versions do. They do have support to
allow for implicit algorithm support as they allow for the allow for implicit algorithm support as they allow for the
application to set attributes that are not to be sent in the application to set attributes that are not to be sent in the
message. message.
* Testing: All of the examples in the example library are generated * Testing: All of the examples in the example library are generated
by the C# library and then validated using the Java and C by the C# library and then validated using the Java and C
libraries. All three libraries have tests to allow for the libraries. All three libraries have tests to allow for the
skipping to change at page 57, line 25 skipping to change at page 59, line 4
* Testing: Basic testing plus running against the common example * Testing: Basic testing plus running against the common example
library. library.
* Licensing: BSD 3-Clause License * Licensing: BSD 3-Clause License
14.4. COSE Testing Library 14.4. COSE Testing Library
* Implementation Location: https://github.com/cose-wg/Examples * Implementation Location: https://github.com/cose-wg/Examples
* Primary Maintainer: Jim Schaad * Primary Maintainer: Jim Schaad
* Description: A set of tests for the COSE library is provided as * Description: A set of tests for the COSE library is provided as
part of the implementation effort. Both success and fail tests part of the implementation effort. Both success and fail tests
have been provided. All of the examples in this document are part have been provided. All of the examples in this document are part
of this example set. of this example set.
* Coverage: An attempt has been made to have test cases for every * Coverage: An attempt has been made to have test cases for every
message type and algorithm in the document. Currently examples message type and algorithm in the document. Currently examples
dealing with counter signatures, and ECDH with Curve24459 and dealing with counter signatures, and ECDH with Curve25519 and
Goldilocks are missing. Goldilocks are missing.
* Licensing: Public Domain * Licensing: Public Domain
15. References 15. References
15.1. Normative References 15.1. Normative References
[COAP.Formats]
IANA, "CoAP Content-Formats",
<https://www.iana.org/assignments/core-parameters/core-
parameters.xhtml#content-formats>.
[COSE.Algorithms]
IANA, "COSE Algorithms",
<https://www.iana.org/assignments/cose/
cose.xhtml#algorithms>.
[COSE.KeyParameters]
IANA, "COSE Key Parameters",
<https://www.iana.org/assignments/cose/cose.xhtml#key-
common-parameters>.
[COSE.KeyTypes]
IANA, "COSE Key Types",
<https://www.iana.org/assignments/cose/cose.xhtml#key-
type>.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>. October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[DSS] National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", DOI 10.6028/NIST.FIPS.186-4,
FIPS PUB 186-4, July 2013,
<http://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.186-4.pdf>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>.
[I-D.ietf-cose-rfc8152bis-algs] [I-D.ietf-cose-rfc8152bis-algs]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", Work in Progress, Internet-Draft, Initial Algorithms", Work in Progress, Internet-Draft,
draft-ietf-cose-rfc8152bis-algs-08, 14 May 2020, draft-ietf-cose-rfc8152bis-algs-10, 26 June 2020,
<https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis- <https://tools.ietf.org/html/draft-ietf-cose-rfc8152bis-
algs-08>. algs-10>.
15.2. Informative References 15.2. Informative References
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017, RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>. <https://www.rfc-editor.org/info/rfc8152>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and Express Concise Binary Object Representation (CBOR) and
skipping to change at page 60, line 10 skipping to change at page 61, line 5
"Use of the RSA-KEM Key Transport Algorithm in the "Use of the RSA-KEM Key Transport Algorithm in the
Cryptographic Message Syntax (CMS)", RFC 5990, Cryptographic Message Syntax (CMS)", RFC 5990,
DOI 10.17487/RFC5990, September 2010, DOI 10.17487/RFC5990, September 2010,
<https://www.rfc-editor.org/info/rfc5990>. <https://www.rfc-editor.org/info/rfc5990>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>. <https://www.rfc-editor.org/info/rfc6838>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [STD90] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259, Interchange Format", STD 90, RFC 8259, December 2017.
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>. <https://www.rfc-editor.org/info/std90>
[BCP201] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, November 2015.
<https://www.rfc-editor.org/info/bcp201>
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>. 2015, <https://www.rfc-editor.org/info/rfc7515>.
skipping to change at page 60, line 36 skipping to change at page 61, line 37
<https://www.rfc-editor.org/info/rfc7516>. <https://www.rfc-editor.org/info/rfc7516>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, [RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015, DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>. <https://www.rfc-editor.org/info/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015, DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>. <https://www.rfc-editor.org/info/rfc7518>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Writing an IANA Considerations Section in RFCs", BCP 26, Signature Algorithm (EdDSA)", RFC 8032,
RFC 8126, DOI 10.17487/RFC8126, June 2017, DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8032>.
[DSS] National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", DOI 10.6028/NIST.FIPS.186-4,
FIPS PUB 186-4, July 2013,
<http://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.186-4.pdf>.
[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 Recovery", Signature Scheme with Partial Message Recovery",
DOI 10.1007/3-540-45353-9_11, LNCS Volume 2020, June 2000, DOI 10.1007/3-540-45353-9_11, LNCS Volume 2020, June 2000,
<https://doi.org/10.1007/3-540-45353-9_11>. <https://doi.org/10.1007/3-540-45353-9_11>.
[W3C.WebCrypto] [W3C.WebCrypto]
Watson, M., "Web Cryptography API", W3C Recommendation, Watson, M., "Web Cryptography API", W3C Recommendation,
January 2017, <https://www.w3.org/TR/WebCryptoAPI/>. January 2017, <https://www.w3.org/TR/WebCryptoAPI/>.
skipping to change at page 61, line 19 skipping to change at page 62, line 23
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205, Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016, RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>. <https://www.rfc-editor.org/info/rfc7942>.
[RFC4998] Gondrom, T., Brandner, R., and U. Pordesch, "Evidence [RFC4998] Gondrom, T., Brandner, R., and U. Pordesch, "Evidence
Record Syntax (ERS)", RFC 4998, DOI 10.17487/RFC4998, Record Syntax (ERS)", RFC 4998, DOI 10.17487/RFC4998,
August 2007, <https://www.rfc-editor.org/info/rfc4998>. August 2007, <https://www.rfc-editor.org/info/rfc4998>.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
September 2002, <https://www.rfc-editor.org/info/rfc3394>.
[I-D.ietf-cose-hash-algs] [I-D.ietf-cose-hash-algs]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Hash Algorithms", Work in Progress, Internet-Draft, draft- Hash Algorithms", Work in Progress, Internet-Draft, draft-
ietf-cose-hash-algs-04, 29 May 2020, ietf-cose-hash-algs-04, 29 May 2020,
<https://tools.ietf.org/html/draft-ietf-cose-hash-algs- <https://tools.ietf.org/html/draft-ietf-cose-hash-algs-
04>. 04>.
[I-D.ietf-core-groupcomm-bis] [I-D.ietf-core-groupcomm-bis]
Dijk, E., Wang, C., and M. Tiloca, "Group Communication Dijk, E., Wang, C., and M. Tiloca, "Group Communication
for the Constrained Application Protocol (CoAP)", Work in for the Constrained Application Protocol (CoAP)", Work in
Progress, Internet-Draft, draft-ietf-core-groupcomm-bis- Progress, Internet-Draft, draft-ietf-core-groupcomm-bis-
00, 30 March 2020, <https://tools.ietf.org/html/draft- 00, 30 March 2020, <https://tools.ietf.org/html/draft-
ietf-core-groupcomm-bis-00>. ietf-core-groupcomm-bis-00>.
[RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz, [RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments "Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019, (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
<https://www.rfc-editor.org/info/rfc8613>. <https://www.rfc-editor.org/info/rfc8613>.
[I-D.irtf-cfrg-argon2]
Biryukov, A., Dinu, D., Khovratovich, D., and S.
Josefsson, "The memory-hard Argon2 password hash and
proof-of-work function", Work in Progress, Internet-Draft,
draft-irtf-cfrg-argon2-10, 25 March 2020,
<https://tools.ietf.org/html/draft-irtf-cfrg-argon2-10>.
[COAP.Formats]
IANA, "CoAP Content-Formats",
<https://www.iana.org/assignments/core-parameters/core-
parameters.xhtml#content-formats>.
[COSE.Algorithms]
IANA, "COSE Algorithms",
<https://www.iana.org/assignments/cose/
cose.xhtml#algorithms>.
[COSE.KeyParameters]
IANA, "COSE Key Parameters",
<https://www.iana.org/assignments/cose/cose.xhtml#key-
common-parameters>.
[COSE.KeyTypes]
IANA, "COSE Key Types",
<https://www.iana.org/assignments/cose/cose.xhtml#key-
type>.
Appendix A. Guidelines for External Data Authentication of Algorithms Appendix A. Guidelines for External Data Authentication of Algorithms
During development of COSE, the requirement that the algorithm During development of COSE, the requirement that the algorithm
identifier be located in the protected attributes was relaxed from a identifier be located in the protected attributes was relaxed from a
must to a should. There were two basic reasons that have been must to a should. There were two basic reasons that have been
advanced to support this position. First, the resulting message will advanced to support this position. First, the resulting message will
be smaller if the algorithm identifier is omitted from the most be smaller if the algorithm identifier is omitted from the most
common messages in a CoAP environment. Second, there is a potential common messages in a CoAP environment. Second, there is a potential
bug that will arise if full checking is not done correctly between bug that will arise if full checking is not done correctly between
the different places that an algorithm identifier could be placed the different places that an algorithm identifier could be placed
skipping to change at page 65, line 15 skipping to change at page 66, line 40
For these cases, the following additional items need to be For these cases, the following additional items need to be
considered: considered:
* Applications need to ensure that the multiple contexts stay * Applications need to ensure that the multiple contexts stay
associated. If one of the contexts is invalidated for any reason, associated. If one of the contexts is invalidated for any reason,
all of the contexts associated with it should also be invalidated. all of the contexts associated with it should also be invalidated.
Appendix B. Two Layers of Recipient Information Appendix B. Two Layers of Recipient Information
All of the currently defined recipient algorithm classes only use two All of the currently defined recipient algorithm classes only use two
layers of the COSE_Encrypt structure. The first layer is the message layers of the COSE structure. The first layer (COSE_Encrypt) is the
content, and the second layer is the content key encryption. message content, and the second layer (COSE_Recipint) is the content
However, if one uses a recipient algorithm such as the RSA Key key encryption. However, if one uses a recipient algorithm such as
Encapsulation Mechanism (RSA-KEM) (see Appendix A of RSA-KEM the RSA Key Encapsulation Mechanism (RSA-KEM) (see Appendix A of RSA-
[RFC5990]), then it makes sense to have three layers of the KEM [RFC5990]), then it makes sense to have two layers of the
COSE_Encrypt structure. COSE_Recipient structure.
These layers would be: These layers would be:
* Layer 0: The content encryption layer. This layer contains the * Layer 0: The content encryption layer. This layer contains the
payload of the message. payload of the message.
* Layer 1: The encryption of the CEK by a KEK. * Layer 1: The encryption of the CEK by a KEK.
* Layer 2: The encryption of a long random secret using an RSA key * Layer 2: The encryption of a long random secret using an RSA key
and a key derivation function to convert that secret into the KEK. and a key derivation function to convert that secret into the KEK.
skipping to change at page 66, line 5 skipping to change at page 68, line 5
* Layer 1: Uses the AES Key Wrap algorithm with a 128-bit key. * Layer 1: Uses the AES Key Wrap algorithm with a 128-bit key.
* Layer 2: Uses ECDH Ephemeral-Static direct to generate the layer 1 * Layer 2: Uses ECDH Ephemeral-Static direct to generate the layer 1
key. key.
In effect, this example is a decomposed version of using the In effect, this example is a decomposed version of using the
ECDH-ES+A128KW algorithm. ECDH-ES+A128KW algorithm.
Size of binary file is 183 bytes Size of binary file is 183 bytes
96( 96(
[ [ / COSE_Encrypt /
/ protected / h'a10101' / { / protected h'a10101' / << {
\ alg \ 1:1 \ AES-GCM 128 \ / alg / 1:1 / AES-GCM 128 /
} / , } >>,
/ unprotected / { / unprotected / {
/ iv / 5:h'02d1f7e6f26c43d4868d87ce' / iv / 5:h'02d1f7e6f26c43d4868d87ce'
}, },
/ ciphertext / h'64f84d913ba60a76070a9a48f26e97e863e2852948658f0 / ciphertext / h'64f84d913ba60a76070a9a48f26e97e863e2852948658f0
811139868826e89218a75715b', 811139868826e89218a75715b',
/ recipients / [ / recipients / [
[ [ / COSE_Recipient /
/ protected / h'', / protected / h'',
/ unprotected / { / unprotected / {
/ alg / 1:-3 / A128KW / / alg / 1:-3 / A128KW /
}, },
/ ciphertext / h'dbd43c4e9d719c27c6275c67d628d493f090593db82 / ciphertext / h'dbd43c4e9d719c27c6275c67d628d493f090593db82
18f11', 18f11',
/ recipients / [ / recipients / [
[ [ / COSE_Recipient /
/ protected / h'a1013818' / { / protected h'a1013818' / << {
\ alg \ 1:-25 \ ECDH-ES + HKDF-256 \ / alg / 1:-25 / ECDH-ES + HKDF-256 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ ephemeral / -1:{ / ephemeral / -1:{
/ kty / 1:2, / kty / 1:2,
/ crv / -1:1, / crv / -1:1,
/ x / -2:h'b2add44368ea6d641f9ca9af308b4079aeb519f11 / x / -2:h'b2add44368ea6d641f9ca9af308b4079aeb519f11
e9b8a55a600b21233e86e68', e9b8a55a600b21233e86e68',
/ y / -3:false / y / -3:false
}, },
/ kid / 4:'meriadoc.brandybuck@buckland.example' / kid / 4:'meriadoc.brandybuck@buckland.example'
}, },
skipping to change at page 68, line 11 skipping to change at page 70, line 11
* Signature Algorithm: ECDSA w/ SHA-256, Curve P-256 * Signature Algorithm: ECDSA w/ SHA-256, Curve P-256
Size of binary file is 103 bytes Size of binary file is 103 bytes
98( 98(
[ [
/ protected / h'', / protected / h'',
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ signatures / [ / signatures / [
[ [
/ protected / h'a10126' / { / protected h'a10126' / << {
\ alg \ 1:-7 \ ECDSA 256 \ / alg / 1:-7 / ECDSA 256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ kid / 4:'11' / kid / 4:'11'
}, },
/ signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb / signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb
5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b 5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b
98f53afd2fa0f30a' 98f53afd2fa0f30a'
] ]
] ]
] ]
) )
skipping to change at page 69, line 11 skipping to change at page 71, line 11
* Signature Algorithm: ECDSA w/ SHA-512, Curve P-521 * Signature Algorithm: ECDSA w/ SHA-512, Curve P-521
Size of binary file is 277 bytes Size of binary file is 277 bytes
98( 98(
[ [
/ protected / h'', / protected / h'',
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ signatures / [ / signatures / [
[ [
/ protected / h'a10126' / { / protected h'a10126' / << {
\ alg \ 1:-7 \ ECDSA 256 \ / alg / 1:-7 / ECDSA 256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ kid / 4:'11' / kid / 4:'11'
}, },
/ signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb / signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb
5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b 5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b
98f53afd2fa0f30a' 98f53afd2fa0f30a'
], ],
[ [
/ protected / h'a1013823' / { / protected h'a1013823' / << {
\ alg \ 1:-36 / alg / 1:-36 / ECDSA 521 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ kid / 4:'bilbo.baggins@hobbiton.example' / kid / 4:'bilbo.baggins@hobbiton.example'
}, },
/ signature / h'00a2d28a7c2bdb1587877420f65adf7d0b9a06635dd1 / signature / h'00a2d28a7c2bdb1587877420f65adf7d0b9a06635dd1
de64bb62974c863f0b160dd2163734034e6ac003b01e8705524c5c4ca479a952f024 de64bb62974c863f0b160dd2163734034e6ac003b01e8705524c5c4ca479a952f024
7ee8cb0b4fb7397ba08d009e0c8bf482270cc5771aa143966e5a469a09f613488030 7ee8cb0b4fb7397ba08d009e0c8bf482270cc5771aa143966e5a469a09f613488030
c5b07ec6d722e3835adb5b2d8c44e95ffb13877dd2582866883535de3bb03d01753f c5b07ec6d722e3835adb5b2d8c44e95ffb13877dd2582866883535de3bb03d01753f
83ab87bb4f7a0297' 83ab87bb4f7a0297'
] ]
] ]
skipping to change at page 70, line 9 skipping to change at page 72, line 9
* The same header parameters are used for both the signature and the * The same header parameters are used for both the signature and the
counter signature. counter signature.
Size of binary file is 180 bytes Size of binary file is 180 bytes
98( 98(
[ [
/ protected / h'', / protected / h'',
/ unprotected / { / unprotected / {
/ countersign / 7:[ / countersign / 7:[
/ protected / h'a10126' / { / protected h'a10126' / << {
\ alg \ 1:-7 \ ECDSA 256 \ / alg / 1:-7 / ECDSA 256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ kid / 4:'11' / kid / 4:'11'
}, },
/ signature / h'5ac05e289d5d0e1b0a7f048a5d2b643813ded50bc9e4 / signature / h'5ac05e289d5d0e1b0a7f048a5d2b643813ded50bc9e4
9220f4f7278f85f19d4a77d655c9d3b51e805a74b099e1e085aacd97fc29d72f887e 9220f4f7278f85f19d4a77d655c9d3b51e805a74b099e1e085aacd97fc29d72f887e
8802bb6650cceb2c' 8802bb6650cceb2c'
] ]
}, },
/ payload / 'This is the content.', / payload / 'This is the content.',
/ signatures / [ / signatures / [
[ [
/ protected / h'a10126' / { / protected h'a10126' / << {
\ alg \ 1:-7 \ ECDSA 256 \ / alg / 1:-7 / ECDSA 256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ kid / 4:'11' / kid / 4:'11'
}, },
/ signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb / signature / h'e2aeafd40d69d19dfe6e52077c5d7ff4e408282cbefb
5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b 5d06cbf414af2e19d982ac45ac98b8544c908b4507de1e90b717c3d34816fe926a2b
98f53afd2fa0f30a' 98f53afd2fa0f30a'
] ]
] ]
] ]
) )
skipping to change at page 71, line 6 skipping to change at page 73, line 6
This example uses the following: This example uses the following:
* Signature Algorithm: ECDSA w/ SHA-256, Curve P-256 * Signature Algorithm: ECDSA w/ SHA-256, Curve P-256
* There is a criticality marker on the "reserved" header parameter * There is a criticality marker on the "reserved" header parameter
Size of binary file is 125 bytes Size of binary file is 125 bytes
98( 98(
[ [
/ protected / h'a2687265736572766564f40281687265736572766564' / / protected h'a2687265736572766564f40281687265736572766564' /
{ << {
"reserved":false, "reserved":false,
\ crit \ 2:[ / crit / 2:[
"reserved" "reserved"
] ]
} / , } >>,
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ signatures / [ / signatures / [
[ [
/ protected / h'a10126' / { / protected h'a10126' / << {
\ alg \ 1:-7 \ ECDSA 256 \ / alg / 1:-7 / ECDSA 256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ kid / 4:'11' / kid / 4:'11'
}, },
/ signature / h'3fc54702aa56e1b2cb20284294c9106a63f91bac658d / signature / h'3fc54702aa56e1b2cb20284294c9106a63f91bac658d
69351210a031d8fc7c5ff3e4be39445b1a3e83e1510d1aca2f2e8a7c081c7645042b 69351210a031d8fc7c5ff3e4be39445b1a3e83e1510d1aca2f2e8a7c081c7645042b
18aba9d1fad1bd9c' 18aba9d1fad1bd9c'
] ]
] ]
] ]
) )
skipping to change at page 72, line 6 skipping to change at page 74, line 6
C.2.1. Single ECDSA Signature C.2.1. Single ECDSA Signature
This example uses the following: This example uses the following:
* Signature Algorithm: ECDSA w/ SHA-256, Curve P-256 * Signature Algorithm: ECDSA w/ SHA-256, Curve P-256
Size of binary file is 98 bytes Size of binary file is 98 bytes
18( 18(
[ [
/ protected / h'a10126' / { / protected h'a10126' / << {
\ alg \ 1:-7 \ ECDSA 256 \ / alg / 1:-7 / ECDSA 256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ kid / 4:'11' / kid / 4:'11'
}, },
/ payload / 'This is the content.', / payload / 'This is the content.',
/ signature / h'8eb33e4ca31d1c465ab05aac34cc6b23d58fef5c083106c4 / signature / h'8eb33e4ca31d1c465ab05aac34cc6b23d58fef5c083106c4
d25a91aef0b0117e2af9a291aa32e14ab834dc56ed2a223444547e01f11d3b0916e5 d25a91aef0b0117e2af9a291aa32e14ab834dc56ed2a223444547e01f11d3b0916e5
a4c345cacb36' a4c345cacb36'
] ]
) )
skipping to change at page 73, line 6 skipping to change at page 75, line 6
This example uses the following: This example uses the following:
* CEK: AES-GCM w/ 128-bit key * CEK: AES-GCM w/ 128-bit key
* Recipient class: ECDH Ephemeral-Static, Curve P-256 * Recipient class: ECDH Ephemeral-Static, Curve P-256
Size of binary file is 151 bytes Size of binary file is 151 bytes
96( 96(
[ [
/ protected / h'a10101' / { / protected h'a10101' / << {
\ alg \ 1:1 \ AES-GCM 128 \ / alg / 1:1 / AES-GCM 128 /
} / , } >>,
/ unprotected / { / unprotected / {
/ iv / 5:h'c9cf4df2fe6c632bf7886413' / iv / 5:h'c9cf4df2fe6c632bf7886413'
}, },
/ ciphertext / h'7adbe2709ca818fb415f1e5df66f4e1a51053ba6d65a1a0 / ciphertext / h'7adbe2709ca818fb415f1e5df66f4e1a51053ba6d65a1a0
c52a357da7a644b8070a151b0', c52a357da7a644b8070a151b0',
/ recipients / [ / recipients / [
[ [
/ protected / h'a1013818' / { / protected h'a1013818' / << {
\ alg \ 1:-25 \ ECDH-ES + HKDF-256 \ / alg / 1:-25 / ECDH-ES + HKDF-256 /
} / , } >>,
/ unprotected / { / unprotected / {
/ ephemeral / -1:{ / ephemeral / -1:{
/ kty / 1:2, / kty / 1:2,
/ crv / -1:1, / crv / -1:1,
/ x / -2:h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbf / x / -2:h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbf
bf054e1c7b4d91d6280', bf054e1c7b4d91d6280',
/ y / -3:true / y / -3:true
}, },
/ kid / 4:'meriadoc.brandybuck@buckland.example' / kid / 4:'meriadoc.brandybuck@buckland.example'
}, },
skipping to change at page 74, line 9 skipping to change at page 76, line 9
- PartyU identity: "lighting-client" - PartyU identity: "lighting-client"
- PartyV identity: "lighting-server" - PartyV identity: "lighting-server"
- Supplementary Public Other: "Encryption Example 02" - Supplementary Public Other: "Encryption Example 02"
Size of binary file is 91 bytes Size of binary file is 91 bytes
96( 96(
[ [
/ protected / h'a1010a' / { / protected h'a1010a' / << {
\ alg \ 1:10 \ AES-CCM-16-64-128 \ / alg / 1:10 / AES-CCM-16-64-128 /
} / , } >>,
/ unprotected / { / unprotected / {
/ iv / 5:h'89f52f65a1c580933b5261a76c' / iv / 5:h'89f52f65a1c580933b5261a76c'
}, },
/ ciphertext / h'753548a19b1307084ca7b2056924ed95f2e3b17006dfe93 / ciphertext / h'753548a19b1307084ca7b2056924ed95f2e3b17006dfe93
1b687b847', 1b687b847',
/ recipients / [ / recipients / [
[ [
/ protected / h'a10129' / { / protected h'a10129' / << {
\ alg \ 1:-10 / alg / 1:-10
} / , } >>,
/ unprotected / { / unprotected / {
/ salt / -20:'aabbccddeeffgghh', / salt / -20:'aabbccddeeffgghh',
/ kid / 4:'our-secret' / kid / 4:'our-secret'
}, },
/ ciphertext / h'' / ciphertext / h''
] ]
] ]
] ]
) )
skipping to change at page 75, line 6 skipping to change at page 77, line 6
This example uses the following: This example uses the following:
* CEK: AES-GCM w/ 128-bit key * CEK: AES-GCM w/ 128-bit key
* Recipient class: ECDH Ephemeral-Static, Curve P-256 * Recipient class: ECDH Ephemeral-Static, Curve P-256
Size of binary file is 326 bytes Size of binary file is 326 bytes
96( 96(
[ [
/ protected / h'a10101' / { / protected h'a10101' / << {
\ alg \ 1:1 \ AES-GCM 128 \ / alg / 1:1 / AES-GCM 128 /
} / , } >>,
/ unprotected / { / unprotected / {
/ iv / 5:h'c9cf4df2fe6c632bf7886413', / iv / 5:h'c9cf4df2fe6c632bf7886413',
/ countersign / 7:[ / countersign / 7:[
/ protected / h'a1013823' / { / protected / h'a1013823' / {
\ alg \ 1:-36 \ alg \ 1:-36
} / , } / ,
/ unprotected / { / unprotected / {
/ kid / 4:'bilbo.baggins@hobbiton.example' / kid / 4:'bilbo.baggins@hobbiton.example'
}, },
/ signature / h'00929663c8789bb28177ae28467e66377da12302d7f9 / signature / h'00929663c8789bb28177ae28467e66377da12302d7f9
594d2999afa5dfa531294f8896f2b6cdf1740014f4c7f1a358e3a6cf57f4ed6fb02f 594d2999afa5dfa531294f8896f2b6cdf1740014f4c7f1a358e3a6cf57f4ed6fb02f
cf8f7aa989f5dfd07f0700a3a7d8f3c604ba70fa9411bd10c2591b483e1d2c31de00 cf8f7aa989f5dfd07f0700a3a7d8f3c604ba70fa9411bd10c2591b483e1d2c31de00
3183e434d8fba18f17a4c7e3dfa003ac1cf3d30d44d2533c4989d3ac38c38b71481c 3183e434d8fba18f17a4c7e3dfa003ac1cf3d30d44d2533c4989d3ac38c38b71481c
c3430c9d65e7ddff' c3430c9d65e7ddff'
] ]
}, },
/ ciphertext / h'7adbe2709ca818fb415f1e5df66f4e1a51053ba6d65a1a0 / ciphertext / h'7adbe2709ca818fb415f1e5df66f4e1a51053ba6d65a1a0
c52a357da7a644b8070a151b0', c52a357da7a644b8070a151b0',
/ recipients / [ / recipients / [
[ [
/ protected / h'a1013818' / { / protected h'a1013818' / << {
\ alg \ 1:-25 \ ECDH-ES + HKDF-256 \ / alg / 1:-25 / ECDH-ES + HKDF-256 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ ephemeral / -1:{ / ephemeral / -1:{
/ kty / 1:2, / kty / 1:2,
/ crv / -1:1, / crv / -1:1,
/ x / -2:h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbf / x / -2:h'98f50a4ff6c05861c8860d13a638ea56c3f5ad7590bbf
bf054e1c7b4d91d6280', bf054e1c7b4d91d6280',
/ y / -3:true / y / -3:true
}, },
/ kid / 4:'meriadoc.brandybuck@buckland.example' / kid / 4:'meriadoc.brandybuck@buckland.example'
}, },
skipping to change at page 76, line 15 skipping to change at page 78, line 15
* CEK: AES-GCM w/ 128-bit key * CEK: AES-GCM w/ 128-bit key
* Recipient class: ECDH static-Static, Curve P-256 with AES Key Wrap * Recipient class: ECDH static-Static, Curve P-256 with AES Key Wrap
* Externally Supplied AAD: h'0011bbcc22dd44ee55ff660077' * Externally Supplied AAD: h'0011bbcc22dd44ee55ff660077'
Size of binary file is 173 bytes Size of binary file is 173 bytes
96( 96(
[ [
/ protected / h'a10101' / { / protected h'a10101' / << {
\ alg \ 1:1 \ AES-GCM 128 \ / alg / 1:1 / AES-GCM 128 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ iv / 5:h'02d1f7e6f26c43d4868d87ce' / iv / 5:h'02d1f7e6f26c43d4868d87ce'
}, },
/ ciphertext / h'64f84d913ba60a76070a9a48f26e97e863e28529d8f5335 / ciphertext / h'64f84d913ba60a76070a9a48f26e97e863e28529d8f5335
e5f0165eee976b4a5f6c6f09d', e5f0165eee976b4a5f6c6f09d',
/ recipients / [ / recipients / [
[ [
/ protected / h'a101381f' / { / protected / h'a101381f' / {
\ alg \ 1:-32 \ ECHD-SS+A128KW \ \ alg \ 1:-32 \ ECHD-SS+A128KW \
} / , } / ,
skipping to change at page 77, line 6 skipping to change at page 79, line 6
C.4.1. Simple Encrypted Message C.4.1. Simple Encrypted Message
This example uses the following: This example uses the following:
* CEK: AES-CCM w/ 128-bit key and a 64-bit tag * CEK: AES-CCM w/ 128-bit key and a 64-bit tag
Size of binary file is 52 bytes Size of binary file is 52 bytes
16( 16(
[ [
/ protected / h'a1010a' / { / protected h'a1010a' / << {
\ alg \ 1:10 \ AES-CCM-16-64-128 \ / alg / 1:10 / AES-CCM-16-64-128 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ iv / 5:h'89f52f65a1c580933b5261a78c' / iv / 5:h'89f52f65a1c580933b5261a78c'
}, },
/ ciphertext / h'5974e1b99a3a4cc09a659aa2e9e7fff161d38ce71cb45ce / ciphertext / h'5974e1b99a3a4cc09a659aa2e9e7fff161d38ce71cb45ce
460ffb569' 460ffb569'
] ]
) )
C.4.2. Encrypted Message with a Partial IV C.4.2. Encrypted Message with a Partial IV
This example uses the following: This example uses the following:
* CEK: AES-CCM w/ 128-bit key and a 64-bit tag * CEK: AES-CCM w/ 128-bit key and a 64-bit tag
* Prefix for IV is 89F52F65A1C580933B52 * Prefix for IV is 89F52F65A1C580933B52
Size of binary file is 41 bytes Size of binary file is 41 bytes
16( 16(
[ [
/ protected / h'a1010a' / { / protected h'a1010a' / << {
\ alg \ 1:10 \ AES-CCM-16-64-128 \ / alg / 1:10 / AES-CCM-16-64-128 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ partial iv / 6:h'61a7' / partial iv / 6:h'61a7'
}, },
/ ciphertext / h'252a8911d465c125b6764739700f0141ed09192de139e05 / ciphertext / h'252a8911d465c125b6764739700f0141ed09192de139e05
3bd09abca' 3bd09abca'
] ]
) )
C.5. Examples of MACed Messages C.5. Examples of MACed Messages
skipping to change at page 78, line 6 skipping to change at page 80, line 6
This example uses the following: This example uses the following:
* MAC: AES-CMAC, 256-bit key, truncated to 64 bits * MAC: AES-CMAC, 256-bit key, truncated to 64 bits
* Recipient class: direct shared secret * Recipient class: direct shared secret
Size of binary file is 57 bytes Size of binary file is 57 bytes
97( 97(
[ [
/ protected / h'a1010f' / { / protected h'a1010f' / << {
\ alg \ 1:15 \ AES-CBC-MAC-256//64 \ / alg / 1:15 / AES-CBC-MAC-256//64 /
} / , } >> ,
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ tag / h'9e1226ba1f81b848', / tag / h'9e1226ba1f81b848',
/ recipients / [ / recipients / [
[ [
/ protected / h'', / protected / h'',
/ unprotected / { / unprotected / {
/ alg / 1:-6 / direct /, / alg / 1:-6 / direct /,
/ kid / 4:'our-secret' / kid / 4:'our-secret'
}, },
skipping to change at page 79, line 6 skipping to change at page 81, line 6
This example uses the following: This example uses the following:
* MAC: HMAC w/SHA-256, 256-bit key * MAC: HMAC w/SHA-256, 256-bit key
* Recipient class: ECDH key agreement, two static keys, HKDF w/ * Recipient class: ECDH key agreement, two static keys, HKDF w/
context structure context structure
Size of binary file is 214 bytes Size of binary file is 214 bytes
97( 97(
[ [
/ protected / h'a10105' / { / protected h'a10105' / << {
\ alg \ 1:5 \ HMAC 256//256 \ / alg / 1:5 / HMAC 256//256 /
} / , } >> ,
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ tag / h'81a03448acd3d305376eaa11fb3fe416a955be2cbe7ec96f012c99 / tag / h'81a03448acd3d305376eaa11fb3fe416a955be2cbe7ec96f012c99
4bc3f16a41', 4bc3f16a41',
/ recipients / [ / recipients / [
[ [
/ protected / h'a101381a' / { / protected h'a101381a' / << {
\ alg \ 1:-27 \ ECDH-SS + HKDF-256 \ / alg / 1:-27 / ECDH-SS + HKDF-256 /
} / , } >> ,
/ unprotected / { / unprotected / {
/ static kid / -3:'peregrin.took@tuckborough.example', / static kid / -3:'peregrin.took@tuckborough.example',
/ kid / 4:'meriadoc.brandybuck@buckland.example', / kid / 4:'meriadoc.brandybuck@buckland.example',
/ U nonce / -22:h'4d8553e7e74f3c6a3a9dd3ef286a8195cbf8a23d / U nonce / -22:h'4d8553e7e74f3c6a3a9dd3ef286a8195cbf8a23d
19558ccfec7d34b824f42d92bd06bd2c7f0271f0214e141fb779ae2856abf585a583 19558ccfec7d34b824f42d92bd06bd2c7f0271f0214e141fb779ae2856abf585a583
68b017e7f2a9e5ce4db5' 68b017e7f2a9e5ce4db5'
}, },
/ ciphertext / h'' / ciphertext / h''
] ]
] ]
skipping to change at page 80, line 6 skipping to change at page 82, line 6
This example uses the following: This example uses the following:
* MAC: AES-MAC, 128-bit key, truncated to 64 bits * MAC: AES-MAC, 128-bit key, truncated to 64 bits
* Recipient class: AES Key Wrap w/ a pre-shared 256-bit key * Recipient class: AES Key Wrap w/ a pre-shared 256-bit key
Size of binary file is 109 bytes Size of binary file is 109 bytes
97( 97(
[ [
/ protected / h'a1010e' / { / protected h'a1010e' / << {
\ alg \ 1:14 \ AES-CBC-MAC-128//64 \ / alg / 1:14 / AES-CBC-MAC-128//64 /
} / , } >> ,
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ tag / h'36f5afaf0bab5d43', / tag / h'36f5afaf0bab5d43',
/ recipients / [ / recipients / [
[ [
/ protected / h'', / protected / h'',
/ unprotected / { / unprotected / {
/ alg / 1:-5 / A256KW /, / alg / 1:-5 / A256KW /,
/ kid / 4:'018c0ae5-4d9b-471b-bfd6-eef314bc7037' / kid / 4:'018c0ae5-4d9b-471b-bfd6-eef314bc7037'
}, },
skipping to change at page 81, line 6 skipping to change at page 83, line 6
* Recipient class: Uses three different methods * 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. AES Key Wrap w/ 256-bit key 2. AES Key Wrap w/ 256-bit key
Size of binary file is 309 bytes Size of binary file is 309 bytes
97( 97(
[ [
/ protected / h'a10105' / { / protected h'a10105' / << {
\ alg \ 1:5 \ HMAC 256//256 \ / alg / 1:5 / HMAC 256//256 /
} / , } >> ,
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ tag / h'bf48235e809b5c42e995f2b7d5fa13620e7ed834e337f6aa43df16 / tag / h'bf48235e809b5c42e995f2b7d5fa13620e7ed834e337f6aa43df16
1e49e9323e', 1e49e9323e',
/ recipients / [ / recipients / [
[ [
/ protected / h'a101381c' / { / protected h'a101381c' / << {
\ alg \ 1:-29 \ ECHD-ES+A128KW \ / alg / 1:-29 / ECHD-ES+A128KW /
} / , } >> ,
/ unprotected / { / unprotected / {
/ ephemeral / -1:{ / ephemeral / -1:{
/ kty / 1:2, / kty / 1:2,
/ crv / -1:3, / crv / -1:3,
/ x / -2:h'0043b12669acac3fd27898ffba0bcd2e6c366d53bc4db / x / -2:h'0043b12669acac3fd27898ffba0bcd2e6c366d53bc4db
71f909a759304acfb5e18cdc7ba0b13ff8c7636271a6924b1ac63c02688075b55ef2 71f909a759304acfb5e18cdc7ba0b13ff8c7636271a6924b1ac63c02688075b55ef2
d613574e7dc242f79c3', d613574e7dc242f79c3',
/ y / -3:true / y / -3:true
}, },
/ kid / 4:'bilbo.baggins@hobbiton.example' / kid / 4:'bilbo.baggins@hobbiton.example'
skipping to change at page 82, line 10 skipping to change at page 84, line 10
This example uses the following: This example uses the following:
* MAC: AES-CMAC, 256-bit key, truncated to 64 bits * MAC: AES-CMAC, 256-bit key, truncated to 64 bits
* Recipient class: direct shared secret * Recipient class: direct shared secret
Size of binary file is 37 bytes Size of binary file is 37 bytes
17( 17(
[ [
/ protected / h'a1010f' / { / protected h'a1010f' / << {
\ alg \ 1:15 \ AES-CBC-MAC-256//64 \ / alg / 1:15 / AES-CBC-MAC-256//64 /
} / , } >> ,
/ unprotected / {}, / unprotected / {},
/ payload / 'This is the content.', / payload / 'This is the content.',
/ tag / h'726043745027214f' / tag / h'726043745027214f'
] ]
) )
Note that this example uses the same inputs as Appendix C.5.1. Note that this example uses the same inputs as Appendix C.5.1.
C.7. COSE Keys C.7. COSE Keys
skipping to change at page 86, line 7 skipping to change at page 88, line 7
The following individuals are to blame for getting me started on this The following individuals are to blame for getting me started on this
project in the first place: Richard Barnes, Matt Miller, and Martin project in the first place: Richard Barnes, Matt Miller, and Martin
Thomson. Thomson.
The initial version of the specification was based to some degree on The initial version of the specification was based to some degree on
the outputs of the JOSE and S/MIME working groups. the outputs of the JOSE and S/MIME working groups.
The following individuals provided input into the final form of the The following individuals provided input into the final form of the
document: Carsten Bormann, John Bradley, Brain Campbell, Michael B. document: Carsten Bormann, John Bradley, Brain Campbell, Michael B.
Jones, Ilari Liusvaara, Francesca Palombini, Ludwig Seitz, and Goran Jones, Ilari Liusvaara, Francesca Palombini, Ludwig Seitz, and
Selander. G&#246;ran Selander.
Author's Address Author's Address
Jim Schaad Jim Schaad
August Cellars August Cellars
Email: ietf@augustcellars.com Email: ietf@augustcellars.com
 End of changes. 127 change blocks. 
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