Semi-Static Diffie-Hellman Key Establishment for TLS 1.3
draft-rescorla-tls-semistatic-dh-00

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Last updated 2018-10-22
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TLS Working Group                                            E. Rescorla
Internet-Draft                                                   Mozilla
Intended status: Standards Track                             N. Sullivan
Expires: April 25, 2019                                       Cloudflare
                                                                 C. Wood
                                                              Apple Inc.
                                                        October 22, 2018

        Semi-Static Diffie-Hellman Key Establishment for TLS 1.3
                  draft-rescorla-tls-semistatic-dh-00

Abstract

   TLS 1.3 [I-D.ietf-tls-tls13] specifies a signed Diffie-Hellman
   exchange modelled after SIGMA [SIGMA].  This design is suitable for
   endpoints whose certified credential is a signing key, which is the
   common situation for current TLS servers.  This document describes a
   mode of TLS 1.3 in which one or both endpoints have a certified DH
   key which is used to authenticate the exchange.

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
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   This Internet-Draft will expire on April 25, 2019.

Copyright Notice

   Copyright (c) 2018 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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   (http://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

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   to this document.  Code Components extracted from this document must
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Negotiation . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Certificate Format  . . . . . . . . . . . . . . . . . . . . .   5
   5.  Cryptographic Details . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Certificate Verify Computation  . . . . . . . . . . . . .   5
     5.2.  Key Schedule  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Early Data and Resumption . . . . . . . . . . . . . . . . . .   6
   7.  Client Authentication . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   DISCLAIMER: This is a work-in-progress draft and has not yet seen
   significant security analysis.  Analysis of the modified TLS 1.3 -21
   Tamarin model is currently underway.  Thus, this draft should not be
   used as a basis for building production systems.

   TLS 1.3 [I-D.ietf-tls-tls13] specifies a signed Diffie-Hellman
   exchange modeled after SIGMA [SIGMA].  This design is suitable for
   endpoints whose certified credential is a signing key, which is the
   common situation for current TLS servers, which is why it was
   selected for TLS 1.3.

   However, it is also possible - although currently rare - for
   endpoints to have a credential which is an (EC)DH key.  This can
   happen in one of two ways:

   o  They may be issued a certificate with an (EC)DH key, as specified
      for instance in [I-D.ietf-curdle-pkix]

   o  They may have a signing key which they use to generate a delegated
      credential [I-D.ietf-tls-subcerts] containing an (EC)DH key.

   In these situations, a signed DH exchange is not appropriate, and
   instead a design in which the server authenticates via its long-term

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