OCRA: OATH Challenge-Response Algorithm
RFC 6287

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Internet Engineering Task Force (IETF)                        D. M'Raihi
Request for Comments: 6287                                Verisign, Inc.
Category: Informational                                        J. Rydell
ISSN: 2070-1721                                           Portwise, Inc.
                                                                S. Bajaj
                                                          Symantec Corp.
                                                              S. Machani
                                                        Diversinet Corp.
                                                             D. Naccache
                                                Ecole Normale Superieure
                                                               June 2011

                OCRA: OATH Challenge-Response Algorithm

Abstract

   This document describes an algorithm for challenge-response
   authentication developed by the Initiative for Open Authentication
   (OATH).  The specified mechanisms leverage the HMAC-based One-Time
   Password (HOTP) algorithm and offer one-way and mutual
   authentication, and electronic signature capabilities.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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/rfc6287.

Copyright Notice

   Copyright (c) 2011 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

M'Raihi, et al.               Informational                     [Page 1]
RFC 6287                          OCRA                         June 2011

   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.

Table of Contents

   1. Introduction ....................................................3
   2. Notation and Terminology ........................................3
   3. Algorithm Requirements ..........................................3
   4. OCRA Background .................................................4
      4.1. HOTP Algorithm .............................................4
   5. Definition of OCRA ..............................................5
      5.1. DataInput Parameters .......................................5
      5.2. CryptoFunction .............................................7
   6. The OCRASuite ...................................................8
      6.1. Algorithm ..................................................9
      6.2. CryptoFunction .............................................9
      6.3. DataInput ..................................................9
      6.4. OCRASuite Examples ........................................10
   7. Algorithm Modes for Authentication .............................10
      7.1. One-Way Challenge-Response ................................11
      7.2. Mutual Challenge-Response .................................12
      7.3. Algorithm Modes for Signature .............................13
           7.3.1. Plain Signature ....................................13
           7.3.2. Signature with Server Authentication ...............14
   8. Security Considerations ........................................16
      8.1. Security Analysis of OCRA .................................16
      8.2. Implementation Considerations .............................17
   9. Conclusion .....................................................18
   10. Acknowledgements ..............................................18
   11. References ....................................................19
      11.1. Normative References .....................................19
      11.2. Informative References ...................................19
   Appendix A. Reference Implementation ..............................20
   Appendix B. Test Vectors Generation ...............................26
   Appendix C. Test Vectors ..........................................33
     C.1. One-Way Challenge Response .................................34