Hybrid key exchange in TLS 1.3
draft-stebila-tls-hybrid-design-03

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Network Working Group                                         D. Stebila
Internet-Draft                                    University of Waterloo
Intended status: Informational                                S. Fluhrer
Expires: August 15, 2020                                   Cisco Systems
                                                               S. Gueron
                                           U. Haifa, Amazon Web Services
                                                       February 12, 2020

                     Hybrid key exchange in TLS 1.3
                   draft-stebila-tls-hybrid-design-03

Abstract

   Hybrid key exchange refers to using multiple key exchange algorithms
   simultaneously and combining the result with the goal of providing
   security even if all but one of the component algorithms is broken.
   It is motivated by transition to post-quantum cryptography.  This
   document provides a construction for hybrid key exchange in the
   Transport Layer Security (TLS) protocol version 1.3.

   Discussion of this work is encouraged to happen on the TLS IETF
   mailing list tls@ietf.org or on the GitHub repository which contains
   the draft: https://github.com/dstebila/draft-stebila-tls-hybrid-
   design.

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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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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 August 15, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Stebila, et al.          Expires August 15, 2020                [Page 1]
Internet-Draft          stebila-tls-hybrid-design          February 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Revision history  . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Motivation for use of hybrid key exchange . . . . . . . .   5
     1.4.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.5.  Goals . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  Key encapsulation mechanisms  . . . . . . . . . . . . . . . .   7
   3.  Construction for hybrid key exchange  . . . . . . . . . . . .   8
     3.1.  Negotiation . . . . . . . . . . . . . . . . . . . . . . .   8
     3.2.  Transmitting public keys and ciphertexts  . . . . . . . .   9
     3.3.  Shared secret calculation . . . . . . . . . . . . . . . .  10
   4.  Open questions  . . . . . . . . . . . . . . . . . . . . . . .  12
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  Related work . . . . . . . . . . . . . . . . . . . .  18
   Appendix B.  Design Considerations  . . . . . . . . . . . . . . .  19
     B.1.  (Neg) How to negotiate hybridization and component
           algorithms? . . . . . . . . . . . . . . . . . . . . . . .  21
       B.1.1.  Key exchange negotiation in TLS 1.3 . . . . . . . . .  21
       B.1.2.  (Neg-Ind) Negotiating component algorithms
               individually  . . . . . . . . . . . . . . . . . . . .  21
       B.1.3.  (Neg-Comb) Negotiating component algorithms as a
               combination . . . . . . . . . . . . . . . . . . . . .  22
       B.1.4.  Benefits and drawbacks  . . . . . . . . . . . . . . .  23
     B.2.  (Num) How many component algorithms to combine? . . . . .  24
       B.2.1.  (Num-2) Two . . . . . . . . . . . . . . . . . . . . .  24