Internet DRAFT - draft-bormann-cose-registration-principles
draft-bormann-cose-registration-principles
CBOR Object Signing and Encryption C. Bormann
Internet-Draft Universität Bremen TZI
Intended status: Informational 24 July 2023
Expires: 25 January 2024
COSE: On Registration Principles
draft-bormann-cose-registration-principles-00
Abstract
COSE (STD 96, RFC 9052 and RFC 9338) defines a number of registries
that allow registrants to exercise the numerous extension points
defined in COSE. Section 11.6 of RFC 9052 gives the Designated
Experts for these registries considerable leeway in deciding about
registration requests.
The present document is intended to collect information that has been
the basis for initial population of and further registration in these
registries. It is intended to be shaped by the Designated Experts
and serve them as a collective memorandum and a checklist. As a
secondary function, it is also intended to help registrants create
registrations that are acceptable to the Designated Experts.
// Revision -00 of this draft is an early skeleton that should allow
// us to decide whether such a collection of information is useful
// and whether we want to flesh out this document.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-bormann-cose-registration-
principles/.
Discussion of this document takes place on the CBOR Object Signing
and Encryption (COSE) Working Group mailing list
(mailto:cose@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/cose/. Subscribe at
https://www.ietf.org/mailman/listinfo/cose/.
Source for this draft and an issue tracker can be found at
https://github.com/cabo/cose-regprin.
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on 25 January 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. COSE Registration Principles . . . . . . . . . . . . . . . . 4
2.1. General Considerations . . . . . . . . . . . . . . . . . 4
2.2. COSE Header Parameters . . . . . . . . . . . . . . . . . 4
2.3. COSE Header Algorithm Parameters . . . . . . . . . . . . 4
2.4. COSE Algorithms . . . . . . . . . . . . . . . . . . . . . 4
2.5. COSE Key Common Parameters . . . . . . . . . . . . . . . 5
2.6. COSE Key Type Parameters . . . . . . . . . . . . . . . . 5
2.7. COSE Key Types . . . . . . . . . . . . . . . . . . . . . 5
2.8. COSE Elliptic Curves . . . . . . . . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Informative References . . . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
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Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
COSE (STD 96, RFC 9052 and RFC 9338) defines a number of registries
that allow registrants to exercise the numerous extension points
defined in COSE. Section 11.6 of RFC 9052 gives the Designated
Experts for these registries considerable leeway in deciding about
registration requests.
Specifically, Section 11.6 of [RFC9052] says:
| 11.6. Expert Review Instructions
|
| All the IANA registries established by [RFC8152] are, at least in
| part, defined as Expert Review [RFC8126]. 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.
([RFC8152] is the previous edition of what is now RFC9052 and
[RFC9053]; this document established the registries being discussed,
which together make up the [IANA.cose] registry group.)
The further text of Section 11.6 of [RFC9052] gives instructions
about the general operations of the registries, but does not discuss
the architectural and structural principles that might go into a
registration decision.
The present document is intended to collect information that has been
the basis for initial population of and further registration in these
registries. It is intended to be shaped by the Designated Experts
and serve them as a collective memorandum and a checklist. As a
secondary function, it is also intended to help registrants create
registrations that are acceptable to the Designated Experts.
// Revision -00 of this draft is an early skeleton that should allow
// us to decide whether such a collection of information is useful
// and whether we want to flesh out this document.
1.1. Conventions and Definitions
The definitions of [STD94] and [STD96] apply.
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2. COSE Registration Principles
// This section is a skeleton and needs to be fleshed out.
At the time of writing, some 172 registrations have been made in the
COSE registry group [IANA.cose]. These can serve as a body of
examples how to make registrations. Unfortunately, not all
registrations in this set demonstrate outstanding consistency in
decision-making, so this section will also collect information about
where existing registration decisions turned out to be suboptimal or
at least different in structure than registrations of a similar
nature.
2.1. General Considerations
Code Point Frugality: COSE is designed to work in environments where
at least some of the devices have limited resources; curation of
codepoints so that the ones that are most frequently used with
such constrained devices receive the codepoints with the shortest
representation (and can continue to do so over a number of
decades) is always an objective.
2.2. COSE Header Parameters
...
2.3. COSE Header Algorithm Parameters
...
2.4. COSE Algorithms
Algorithm identifiers in these registrations have a _Recommended_
Tag, which indicates (Section 16.4 of [RFC8152]):
| Recommended: Does the IETF have a consensus recommendation to use
| the algorithm? The legal values are 'Yes', 'No', and
| 'Deprecated'.
Note that an algorithm can be _deprecated_ already at registration
time. This value was used in the registration of the
[I-D.ietf-cose-aes-ctr-and-cbc] values which only can be used under
very specific conditions.
Algorithm identifiers are usually assigned so that a single
identifier stands for a collection of underlying algorithms, with
main parameters such as key or hash length chosen, so that a single
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algorithm identifier suffices to fully characterize the cryptographic
operations. A key is the obvious exception, but also parameters that
go with a key such as its curve type.
Where a certain underlying algorithm has a small number of possible
parameter sets, all registrations for the use of that underlying
algorithm in a COSE Algorithm are made at the same time. For
instance: A128GCM (AES-GCM mode w/ 128-bit key, 128-bit tag) we
registered together with A192GCM (AES-GCM mode w/ 192-bit key,
128-bit tag) and A256GCM (AES-GCM mode w/ 256-bit key, 128-bit tag).
The expert (in this case the author of [RFC9053]) did not make
separate assessments how useful or desirable the individual parameter
sets were going to be, but registered them all at once. When the
collection of AES-CCM-16-64-128, AES-CCM-16-64-256, AES-CCM-
64-64-128, and AES-CCM-64-64-256, as well as AES-CCM-16-128-128, AES-
CCM-16-128-256, AES-CCM-64-128-128, and AES-CCM-64-128-256 were
registered, these were also registered all at once, but grouped into
two groups with different representation sizes of the algorithm
identifier.
2.5. COSE Key Common Parameters
...
2.6. COSE Key Type Parameters
...
2.7. COSE Key Types
...
2.8. COSE Elliptic Curves
This registry is governed by similar principles as the COSE
Algorithms registry (Section 2.4). Curve types identify all
parameters of a curve and are registered all at once where natural
groups of such types exist.
3. Security Considerations
This document is about registrations in registries that have direct
security impact; security considerations that require discussion
beyond that are mentioned in the discussions above.
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4. IANA Considerations
This document has no IANA actions.
5. Informative References
[I-D.ietf-cose-aes-ctr-and-cbc]
Housley, R. and H. Tschofenig, "CBOR Object Signing and
Encryption (COSE): AES-CTR and AES-CBC", Work in Progress,
Internet-Draft, draft-ietf-cose-aes-ctr-and-cbc-06, 25 May
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
cose-aes-ctr-and-cbc-06>.
[IANA.cose]
IANA, "CBOR Object Signing and Encryption (COSE)",
<https://www.iana.org/assignments/cose>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/rfc/rfc8152>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[STD94] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[STD96] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052, August 2022.
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Countersignatures", STD 96, RFC 9338, December 2022.
Acknowledgments
This document was motivated by a discussion at IETF 117 Hackathon.
The author is grateful to the many contributors to the discussions on
the mailing lists that build the basis for this document.
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Author's Address
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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