The OPAQUE Asymmetric PAKE Protocol
draft-irtf-cfrg-opaque-00

Document Type Active Internet-Draft (cfrg RG)
Authors Hugo Krawczyk  , Kevin Lewi  , Christopher Wood 
Last updated 2020-09-28
Replaces draft-krawczyk-cfrg-opaque
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Network Working Group                                        H. Krawczyk
Internet-Draft                                       Algorand Foundation
Intended status: Informational                                   K. Lewi
Expires: 1 April 2021                                           Facebook
                                                               C.A. Wood
                                                              Cloudflare
                                                       28 September 2020

                  The OPAQUE Asymmetric PAKE Protocol
                       draft-irtf-cfrg-opaque-00

Abstract

   This document describes the OPAQUE protocol, a secure asymmetric
   password-authenticated key exchange (aPAKE) that supports mutual
   authentication in a client-server setting without reliance on PKI and
   with security against pre-computation attacks upon server compromise.
   In addition, the protocol provides forward secrecy and the ability to
   hide the password from the server, even during password registration.
   This document specifies the core OPAQUE protocol, along with several
   instantiations in different authenticated key exchange protocols.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/cfrg/draft-irtf-cfrg-opaque.

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 1 April 2021.

Krawczyk, et al.          Expires 1 April 2021                  [Page 1]
Internet-Draft                   OPAQUE                   September 2020

Copyright Notice

   Copyright (c) 2020 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
   Provisions Relating to IETF Documents (https://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
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Notation . . . . . . . . . . . . . . . . . .   5
     1.2.  Notation  . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  Cryptographic Protocol and Algorithm Dependencies . . . . . .   6
   3.  Core Protocol . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Protocol messages . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Offline registration stage  . . . . . . . . . . . . . . .  10
       3.2.1.  Registration messages . . . . . . . . . . . . . . . .  11
       3.2.2.  Registration functions  . . . . . . . . . . . . . . .  12
     3.3.  Online authenticated key exchange stage . . . . . . . . .  15
       3.3.1.  Authenticated key exchange messages . . . . . . . . .  16
       3.3.2.  Authenticated key exchange functions  . . . . . . . .  17
     3.4.  Export Key  . . . . . . . . . . . . . . . . . . . . . . .  18
     3.5.  AKE Execution and Party Identities  . . . . . . . . . . .  19
   4.  Authenticated Key Exchange Protocol Instantiations  . . . . .  19
     4.1.  Key Schedule Utility Functions  . . . . . . . . . . . . .  20
     4.2.  Instantiation with HMQV and 3DH . . . . . . . . . . . . .  21
       4.2.1.  HMQV and 3DH protocol messages  . . . . . . . . . . .  21
       4.2.2.  HMQV and 3DH key derivation . . . . . . . . . . . . .  23
     4.3.  Instantiation with SIGMA-I  . . . . . . . . . . . . . . .  25
       4.3.1.  SIGMA protocol messages . . . . . . . . . . . . . . .  25
       4.3.2.  SIGMA key derivation  . . . . . . . . . . . . . . . .  25
   5.  Configurations  . . . . . . . . . . . . . . . . . . . . . . .  25
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
     6.1.  Configuration Choice  . . . . . . . . . . . . . . . . . .  28
     6.2.  Static Diffie-Hellman Oracles . . . . . . . . . . . . . .  28
     6.3.  Input validation  . . . . . . . . . . . . . . . . . . . .  28
     6.4.  User authentication versus Authenticated Key Exchange . .  29
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