SPAKE2, a PAKE
draft-irtf-cfrg-spake2-01

The information below is for an old version of the document
Document Type Active Internet-Draft (cfrg RG)
Last updated 2015-02-16
Replaces draft-ladd-spake2
Stream IRTF
Intended RFC status Informational
Formats plain text pdf html bibtex
Additional URLs
- Mailing list discussion
Stream IRTF state Active RG Document
Consensus Boilerplate Unknown
Document shepherd No shepherd assigned
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to cfrg-chairs@ietf.org
Internet Draft                                                   W. Ladd
<draft-irtf-cfrg-spake2-01.txt>                                UC Berkeley
Category: Informational                                      
Expires 20 August 2015                                  16 February 2015

                             SPAKE2, a PAKE
                    <draft-irtf-cfrg-spake2-01.txt>

Status of this Memo

   Distribution of this memo is unlimited.

   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
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on date.

Copyright Notice

   Copyright (c) 2015 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
   (http://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 and restrictions with respect
   to this document.

Abstract          

   This Internet-Draft describes SPAKE2, a secure, efficient password
 

Ladd, Watson              Expires 9 July 2015                   [Page 1]
Internet Draft                cfrg-spake2                22 January 2015

   based key exchange protocol.

 

Ladd, Watson              Expires 9 July 2015                   [Page 2]
Internet Draft                cfrg-spake2                22 January 2015

Table of Contents

   1. Introduction ....................................................3
   2. Definition of SPAKE2.............................................3
   3. Table of points .................................................4
   4. Security considerations .........................................5
   5. IANA actions ....................................................5
   6. Acknowledgements.................................................5
   7. References.......................................................5

1. Introduction

   This document describes a means for two parties that share a password
   to derive a shared key. This method is compatible with any group, is
   computationally efficient, and has a strong security proof.

2. Definition of SPAKE2

   Let G be a group in which the Diffie-Hellman problem is hard of order
   ph, with p a big prime and h a cofactor. We denote the operations in
   the group additively. Let H be a hash function from arbitrary strings
   to bit strings of a fixed length. Common choices for H are SHA256 or
   SHA512. We assume there is a representation of elements of G as byte
   strings: common choices would be SEC1 uncompressed for elliptic curve
   groups or big endian integers of a particular length for prime field
   DH.

   || denotes concatenation of strings. We also let len(S) denote the
   length of a string in bytes, represented as an eight-byte big-endian
   number.

   We fix two elements M and N as defined in the table in this document
   for common groups, as well as a generator G of the group. G is
   specified in the document defining the group, and so we do not recall
   it here.

   Let A and B be two parties. We will assume that A and B are also
   representations of the parties such as MAC addresses or other names
   (hostnames, usernames, etc). We assume they share an integer w.
   Typically w will be the hash of a user-supplied password, truncated
   and taken mod p. Protocols using this protocol must define the method
   used to compute w: it may be necessary to carry out normalization.

   A picks x randomly and uniformly from the integers in [0,ph)
   divisible by h, and calculates X=xG and T=wM+X, then transmits T to
   B.

   B selects y randomly and uniformly from the integers in [0,ph),
 

Ladd, Watson              Expires 9 July 2015                   [Page 3]
Internet Draft                cfrg-spake2                22 January 2015

   divisible by h and calculates Y=yG, S=wN+Y, then transmits S to A.

   Both A and B calculate a group element K. A calculates it as x(S-wN),
Show full document text