Usage of SPAKE with TLS 1.3
draft-barnes-tls-pake-01

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Network Working Group                                          R. Barnes
Internet-Draft                                                  O. Friel
Intended status: Informational                                     Cisco
Expires: October 15, 2018                                 April 13, 2018

                      Usage of SPAKE with TLS 1.3
                        draft-barnes-tls-pake-01

Abstract

   The pre-shared key mechanism available in TLS 1.3 is not suitable for
   usage with low-entropy keys, such as passwords entered by users.
   This document describes how the SPAKE password-authenticated key
   exchange can be used with TLS 1.3.

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 October 15, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  TLS Extensions  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   DISCLAIMER: This is a work-in-progress draft of MLS and has not yet
   seen significant security analysis.  It should not be used as a basis
   for building production systems.

   In some applications, it is desireable to enable a client and server
   to authenticate to one another using a low-entropy pre-shared value,
   such as a user-entered password.

   In prior versions of TLS, this functionality has been provided by the
   integration of the Secure Remote Password PAKE protocol (SRP)
   [RFC5054].  The specific SRP integration described in RFC 5054 does
   not immediately extend to TLS 1.3 becauseit relies on the Client Key
   Exchange and Server Key Exchange messages, which no longer exist in
   1.3.  At a more fundamental level, the messaging patterns required by
   SRP do not map cleanly to the standard TLS 1.3 handshake, which has
   fewer round-trips than prior versions.

   TLS 1.3 itself provides a mechanism for authentication with pre-
   shared keys (PSKs).  However, PSKs used with this protocol need to be
   "full-entropy", because the binder values used for authentication can
   be used to mount a dictionary attack on the PSK.  So while the TLS
   1.3 PSK mechanism is suitable for the session resumption cases for
   which it is specified, it cannot be used when the client and server
   share only a low-entropy secret.

   Enabling TLS to address this use case effectively requires the TLS
   handshake to perform a password-authenticated key establishment
   (PAKE) protocol.  This document describes an embedding of the SPAKE2
   PAKE protocol in TLS 1.3 [I-D.irtf-cfrg-spake2] [I-D.ietf-tls-tls13].
   This mechanism also applies to DTLS 1.3 [I-D.ietf-tls-dtls13], but
   for brevity, we will refer only to TLS throughout.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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