Internet DRAFT - draft-tls-westerbaan-xyber768d00
draft-tls-westerbaan-xyber768d00
None B. Westerbaan
Internet-Draft Cloudflare
Intended status: Informational D. Stebila
Expires: 2 October 2023 University of Waterloo
31 March 2023
X25519Kyber768Draft00 hybrid post-quantum key agreement
draft-tls-westerbaan-xyber768d00-02
Abstract
This memo defines X25519Kyber768Draft00, a hybrid post-quantum key
exchange for TLS 1.3.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://bwesterb.github.io/draft-westerbaan-tls-xyber768d00/draft-
tls-westerbaan-xyber768d00.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-tls-
westerbaan-xyber768d00/.
Source for this draft and an issue tracker can be found at
https://github.com/bwesterb/draft-westerbaan-tls-xyber768d00.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 October 2023.
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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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2
3. Construction . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
6.1. Normative References . . . . . . . . . . . . . . . . . . 3
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 4
A.1. Since draft-tls-westerbaan-xyber768d00-01 . . . . . . . . 4
A.2. Since draft-tls-westerbaan-xyber768d00-00 . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
1.1. Motivation
The final draft for Kyber is expected in 2024. There are already
early deployments of post-quantum key agreement, with more to come
before Kyber is standardised. To promote interoperability of early
implementations, this document specifies a preliminary hybrid post-
quantum key agreement.
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. Construction
We instantiate draft-ietf-tls-hybrid-design-06 with X25519 [rfc7748]
and Kyber768Draft00 [kyber]. The latter is Kyber as submitted to
round 3 of the NIST PQC process [KyberV302].
For the client's share, the key_exchange value contains the
concatenation of the client's X25519 ephemeral share (32 bytes) and
the client's Kyber768Draft00 public key (1184 bytes). The resulting
key_exchange value is 1216 bytes in length.
For the server's share, the key_exchange value contains the
concatenation of the server's X25519 ephemeral share (32 bytes) and
the Kyber768Draft00 ciphertext (1088 bytes) returned from
encapsulation for the client's public key. The resulting
key_exchange value is 1120 bytes in length.
The shared secret is calculated as the concatenation of the X25519
shared secret (32 bytes) and the Kyber768Draft00 shared secret (32
bytes). The resulting shared secret value is 64 bytes in length.
4. Security Considerations
For TLS 1.3, this concatenation approach provides a secure key
exchange if either component key exchange methods (X25519 or
Kyber768Draft00) are secure [hybrid].
5. IANA Considerations
This document requests/registers a new entry to the TLS Named Group
(or Supported Group) registry, according to the procedures in
Section 6 of [tlsiana].
Value: 0x6399 (please)
Description: X25519Kyber768Draft00
DTLS-OK: Y
Recommended: N
Reference: This document
Comment: Pre-standards version of Kyber768
6. References
6.1. Normative References
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[kyber] Schwabe, P. and B. Westerbaan, "Kyber Post-Quantum KEM",
Work in Progress, Internet-Draft, draft-cfrg-schwabe-
kyber-02, 31 March 2023,
<https://datatracker.ietf.org/doc/html/draft-cfrg-schwabe-
kyber-02>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[rfc7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/rfc/rfc7748>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
6.2. Informative References
[hybrid] Stebila, D., Fluhrer, S., and S. Gueron, "Hybrid key
exchange in TLS 1.3", Work in Progress, Internet-Draft,
draft-ietf-tls-hybrid-design-06, 27 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
hybrid-design-06>.
[KyberV302]
Avanzi, R., Bos, J., Ducas, L., Kiltz, E., Lepoint, T.,
Lyubashevsky, V., Schanck, J., Schwabe, P., Seiler, G.,
and D. Stehle, "CRYSTALS-Kyber, Algorithm Specification
And Supporting Documentation (version 3.02)", 2021,
<https://pq-crystals.org/kyber/data/kyber-specification-
round3-20210804.pdf>.
[tlsiana] Salowey, J. A. and S. Turner, "IANA Registry Updates for
TLS and DTLS", Work in Progress, Internet-Draft, draft-
ietf-tls-rfc8447bis-04, 27 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
rfc8447bis-04>.
Appendix A. Change log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
A.1. Since draft-tls-westerbaan-xyber768d00-01
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* Change reference for X25519
A.2. Since draft-tls-westerbaan-xyber768d00-00
* Set working group to None.
* Bump to cfrg-schwabe-kyber-02
Authors' Addresses
Bas Westerbaan
Cloudflare
Email: bas@cloudflare.com
Douglas Stebila
University of Waterloo
Email: dstebila@uwaterloo.ca
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