Messaging Layer Security Ciphersuite using X25519Kyber768Draft00 Key Exchange Mechanism
draft-mahy-mls-x25519kyber768draft00-00

MLS                                                              R. Mahy
Internet-Draft                                                  M. Amiot
Intended status: Informational                                      Wire
Expires: 11 January 2024                                    10 July 2023

  Messaging Layer Security Ciphersuite using X25519Kyber768Draft00 Key
                           Exchange Mechanism
                draft-mahy-mls-x25519kyber768draft00-00

Abstract

   This document registers a new Messaging Layer Security (MLS)
   ciphersuite using the hybrid post-quantum resistant / traditional
   (PQ/T) Key Exchange Mechanism X25519Kyber768Draft00.

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-mahy-mls-
   x25519kyber768draft00/.

   Discussion of this document takes place on the MLS Working Group
   mailing list (mailto:mls@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/mls/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/mls/.

   Source for this draft and an issue tracker can be found at
   https://github.com/rohan-wire/mls-x25519kyber768draft00/.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 11 January 2024.

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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
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Security Considerations . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   3
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   This document reserves a Messaging Layer Security (MLS)
   [I-D.ietf-mls-protocol] ciphersuite value based on the MLS default
   ciphersuite, but replacing the KEM with the hybrid post-quantum /
   traditional Key Exchange Mechanism X25519Kyber768Draft00
   [I-D.draft-westerbaan-cfrg-hpke-xyber768d00] which was assigned the
   Hybrid Public Key Encryption (HPKE) Key Exchange Mechanism (KEM)
   Identifier value 0x0030.

2.  Security Considerations

   This ciphersuite uses a hybrid post-quantum/traditional KEM and a
   traditional signature algorithm.  As such, it is designed to provide
   confidentiality against quantum and classical attacks, but provides
   authenticity against classical attacks only.  This is actually very
   useful, because an attacker could store MLS-encrypted traffic that
   uses any classical KEM today.  If years or decades in the future a
   quantum attack on classical KEMs becomes feasible, the traffic sent
   today (some of which could still be sensitive in the future) will
   then be readable.  By contrast, an attack on a signature algorithm in
   MLS would require an active attack which can extract the private key
   during the signature key's lifetime.

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   The security properties of
   [I-D.draft-westerbaan-cfrg-hpke-xyber768d00] apply.

3.  IANA Considerations

   This document registers a new MLS Ciphersuite value.

   Value:     0x0030 (please)
   Name:      MLS_128_X25519Kyber768Draft00_AES128GCM_SHA256_Ed25519
   Required:  N
   Reference: This document

4.  Normative References

   [I-D.draft-westerbaan-cfrg-hpke-xyber768d00]
              Westerbaan, B. and C. A. Wood, "X25519Kyber768Draft00
              hybrid post-quantum KEM for HPKE", Work in Progress,
              Internet-Draft, draft-westerbaan-cfrg-hpke-xyber768d00-02,
              4 May 2023, <https://datatracker.ietf.org/doc/html/draft-
              westerbaan-cfrg-hpke-xyber768d00-02>.

   [I-D.ietf-mls-protocol]
              Barnes, R., Beurdouche, B., Robert, R., Millican, J.,
              Omara, E., and K. Cohn-Gordon, "The Messaging Layer
              Security (MLS) Protocol", Work in Progress, Internet-
              Draft, draft-ietf-mls-protocol-20, 27 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-mls-
              protocol-20>.

Acknowledgments

   Thanks to Joël Alwen, Marta Mularczyk, and Britta Hale.

Authors' Addresses

   Rohan Mahy
   Wire
   Email: rohan.mahy@wire.com

   Mathieu Amiot
   Wire
   Email: mathieu.amiot@wire.com

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