The OPAQUE Asymmetric PAKE Protocol
draft-krawczyk-cfrg-opaque-04

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Document Type Active Internet-Draft (individual)
Author Hugo Krawczyk 
Last updated 2020-05-14 (latest revision 2019-10-19)
Replaced by draft-irtf-cfrg-opaque
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Crypto Forum Research Group                                  H. Krawczyk
Internet-Draft                                       Algorand Foundation
Intended status: Informational                              May 15, 2020
Expires: November 16, 2020

                  The OPAQUE Asymmetric PAKE Protocol
                     draft-krawczyk-cfrg-opaque-04

Abstract

   This draft 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.
   Prior aPAKE protocols did not use salt and if they did, the salt was
   transmitted in the clear from server to user allowing for the
   building of targeted pre-computed dictionaries.  OPAQUE security has
   been proven by Jarecki et al.  (Eurocrypt 2018) in a strong and
   universally composable formal model of aPAKE security.  In addition,
   the protocol provides forward secrecy and the ability to hide the
   password from the server even during password registration.

   Strong security, versatility through modularity, good performance,
   and an array of additional features make OPAQUE a natural candidate
   for practical use and for adoption as a standard.  To this end, this
   draft presents several instantiations of OPAQUE and ways of
   integrating OPAQUE with TLS.

   This draft presents a high-level description of OPAQUE highlighting
   its components and modular design.  It also provides the basis for a
   specification for standardization but a detailed specification ready
   for implementation is beyond the current scope of this document
   (which may be expanded in future revisions or done separately).

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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   and may be updated, replaced, or obsoleted by other documents at any

Krawczyk                Expires November 16, 2020               [Page 1]
Internet-Draft                   OPAQUE                         May 2020

   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 16, 2020.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
     1.2.  Notation  . . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  DH-OPRF . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.1.  DH-OPRF instantiation and detailed specification  . . . .   8
     2.2.  Hardening OPRF via user iterations  . . . . . . . . . . .   8
   3.  OPAQUE Specification  . . . . . . . . . . . . . . . . . . . .   8
     3.1.  Password registration . . . . . . . . . . . . . . . . . .   9
     3.2.  Online OPAQUE protocol (Login and key exchange))  . . . .  10
     3.3.  Parties' identities . . . . . . . . . . . . . . . . . . .  10
   4.  Specification of the EnvU envelope  . . . . . . . . . . . . .  11
   5.  OPAQUE Instantiations . . . . . . . . . . . . . . . . . . . .  13
     5.1.  Instantiation of OPAQUE with HMQV and 3DH . . . . . . . .  14
     5.2.  Instantiation of OPAQUE with SIGMA-I  . . . . . . . . . .  17
   6.  Integrating OPAQUE with TLS 1.3 . . . . . . . . . . . . . . .  17
   7.  User enumeration  . . . . . . . . . . . . . . . . . . . . . .  21
   8.  Security considerations . . . . . . . . . . . . . . . . . . .  22
   9.  Appendix A.  Counter mode encryption  . . . . . . . . . . . .  23
   10. Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . .  24
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  24
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  24
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