Secure Pre-Shared Key (PSK) Authentication for the Internet Key Exchange Protocol (IKE)
RFC 6617

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Internet Engineering Task Force (IETF)                        D. Harkins
Request for Comments: 6617                                Aruba Networks
Category: Experimental                                         June 2012
ISSN: 2070-1721

               Secure Pre-Shared Key (PSK) Authentication
              for the Internet Key Exchange Protocol (IKE)

Abstract

   This memo describes a secure pre-shared key (PSK) authentication
   method for the Internet Key Exchange Protocol (IKE).  It is resistant
   to dictionary attack and retains security even when used with weak
   pre-shared keys.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6617.

Copyright Notice

   Copyright (c) 2012 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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Harkins                       Experimental                      [Page 1]
RFC 6617            Secure PSK Authentication for IKE          June 2012

Table of Contents

   1. Introduction ....................................................3
      1.1. Keyword Definitions ........................................3
   2. Usage Scenarios .................................................3
   3. Terms and Notation ..............................................4
   4. Discrete Logarithm Cryptography .................................5
      4.1. Elliptic Curve Cryptography (ECP) Groups ...................5
      4.2. Finite Field Cryptography (MODP) Groups ....................7
   5. Random Numbers ..................................................8
   6. Using Passwords and Raw Keys For Authentication .................8
   7. Assumptions .....................................................9
   8. Secure PSK Authentication Message Exchange ......................9
      8.1. Negotiation of Secure PSK Authentication ..................10
      8.2. Fixing the Secret Element, SKE ............................11
           8.2.1. ECP Operation to Select SKE ........................12
           8.2.2. MODP Operation to Select SKE .......................13
      8.3. Encoding and Decoding of Group Elements and Scalars .......14
           8.3.1. Encoding and Decoding of Scalars ...................14
           8.3.2. Encoding and Decoding of ECP Elements ..............15
           8.3.3. Encoding and Decoding of MODP Elements .............15
      8.4. Message Generation and Processing .........................16
           8.4.1. Generation of a Commit .............................16
           8.4.2. Processing of a Commit .............................16
                  8.4.2.1. Validation of an ECP Element ..............16
                  8.4.2.2. Validation of a MODP Element ..............16
                  8.4.2.3. Commit Processing Steps ...................17
           8.4.3. Authentication of the Exchange .....................17
      8.5. Payload Format ............................................18
           8.5.1. Commit Payload .....................................18
      8.6. IKEv2 Messaging ...........................................19
   9. IANA Considerations ............................................20
   10. Security Considerations .......................................20
   11. Acknowledgements ..............................................22
   12. References ....................................................22
      12.1. Normative References .....................................22
      12.2. Informative References ...................................23

Harkins                       Experimental                      [Page 2]
RFC 6617            Secure PSK Authentication for IKE          June 2012

1.  Introduction