TLS 1.3 Extension for Certificate-based Authentication with an External Pre-Shared Key
draft-housley-tls-tls13-cert-with-extern-psk-03

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Network Working Group                                         R. Housley
Internet-Draft                                            Vigil Security
Intended status: Standards Track                        November 8, 2018
Expires: May 12, 2019

TLS 1.3 Extension for Certificate-based Authentication with an External
                             Pre-Shared Key
            draft-housley-tls-tls13-cert-with-extern-psk-03

Abstract

   This document specifies a TLS 1.3 extension that allows a server to
   authenticate with a combination of a certificate and an external pre-
   shared key (PSK).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on May 12, 2019.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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1.  Introduction

   The TLS 1.3 [RFC8446] handshake protocol provides two mutually
   exclusive forms of server authentication.  First, the server can be
   authenticated by providing a signature certificate and creating a
   valid digital signature to demonstrate that it possesses the
   corresponding private key.  Second, the server can be authenticated
   by demonstrating that it possesses a pre-shared key (PSK) that was
   established by a previous handshake.  A PSK that is established in
   this fashion is called a resumption PSK.  A PSK that is established
   by any other means is called an external PSK.  This document
   specifies a TLS 1.3 extension permitting certificate-based server
   authentication to be combined with an external PSK as an input to the
   TLS 1.3 key schedule.

2.  Terminology

   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.

3.  Motivation and Design Rationale

   The invention of a large-scale quantum computer would pose a serious
   challenge for the cryptographic algorithms that are widely deployed
   today, including the digital signature algorithms that are used to
   authenticate the server in the TLS 1.3 handshake protocol.  It is an
   open question whether or not it is feasible to build a large-scale
   quantum computer, and if so, when that might happen.  However, if
   such a quantum computer is invented, many of the cryptographic
   algorithms and the security protocols that use them would become
   vulnerable.

   The TLS 1.3 handshake protocol employs key agreement algorithms that
   could be broken by the invention of a large-scale quantum computer
   [I-D.hoffman-c2pq].  These algorithms include Diffie-Hellman (DH)
   [DH] and Elliptic Curve Diffie-Hellman (ECDH) [IEEE1363].  As a
   result, an adversary that stores a TLS 1.3 handshake protocol
   exchange today could decrypt the associated encrypted communications
   in the future when a large-scale quantum computer becomes available.

   In the near-term, this document describes TLS 1.3 extension to
   protect today's communications from the future invention of a large-
   scale quantum computer by providing a strong external PSK as an input
   to the TLS 1.3 key schedule while preserving the authentication

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   provided by the existing certificate and digital signature
   mechanisms.

4.  Extension Overview

   This section provides a brief overview of the
   "tls_cert_with_extern_psk" extension.