Compact TLS 1.3
draft-rescorla-tls-ctls-01

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TLS Working Group                                            E. Rescorla
Internet-Draft                                                   Mozilla
Intended status: Informational                            March 11, 2019
Expires: September 12, 2019

                            Compact TLS 1.3
                       draft-rescorla-tls-ctls-01

Abstract

   This document specifies a "compact" version of TLS 1.3.  It is
   isomorphic to TLS 1.3 but saves space by aggressive use of defaults
   and tighter encodings.  CTLS is not interoperable with TLS 1.3, but
   it should eventually be possible for the server to distinguish TLS
   1.3 and CTLS handshakes.

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

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

Copyright Notice

   Copyright (c) 2019 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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Rescorla               Expires September 12, 2019               [Page 1]
Internet-Draft                  CTLS 1.3                      March 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Common Primitives . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Varints . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Record Layer  . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Handshake Layer . . . . . . . . . . . . . . . . . . . . .   4
     3.4.  Extensions  . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Handshake Messages  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  ClientHello . . . . . . . . . . . . . . . . . . . . . . .   5
       4.1.1.  KeyShare  . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  ServerHello . . . . . . . . . . . . . . . . . . . . . . .   7
       4.2.1.  KeyShare  . . . . . . . . . . . . . . . . . . . . . .   7
       4.2.2.  PreSharedKeys . . . . . . . . . . . . . . . . . . . .   8
     4.3.  EncryptedExtensions . . . . . . . . . . . . . . . . . . .   8
     4.4.  CertificateRequest  . . . . . . . . . . . . . . . . . . .   8
     4.5.  Certificate . . . . . . . . . . . . . . . . . . . . . . .   8
       4.5.1.  Key IDs . . . . . . . . . . . . . . . . . . . . . . .   9
       4.5.2.  CertificateVerify . . . . . . . . . . . . . . . . . .   9
       4.5.3.  Finished  . . . . . . . . . . . . . . . . . . . . . .   9
       4.5.4.  HelloRetryRequest . . . . . . . . . . . . . . . . . .  10
   5.  Handshake Size Calculations . . . . . . . . . . . . . . . . .  10
     5.1.  ECDHE w/ Signatures . . . . . . . . . . . . . . . . . . .  10
       5.1.1.  Flight 1 (ClientHello) ***  . . . . . . . . . . . . .  10
       5.1.2.  Flight 2 (ServerHello..Finished)  . . . . . . . . . .  10
       5.1.3.  Flight 3 (Client Certificate..Finished) . . . . . . .  11
     5.2.  ECDHE w/ PSK  . . . . . . . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  13
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  13
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   DDISCLAIMER: This is a work-in-progress draft of cTLS and has not yet
   seen significant security analysis, so could contain major errors.
   It should not be used as a basis for building production systems.

   This document specifies a "compact" version of TLS 1.3 [RFC8446].  It
   is isomorphic to TLS 1.3 but designed to take up minimal bandwidth.
   The space reduction is achieved by two basic techniques:

   o  Default values for common configurations, thus avoiding the need