TOTP: Time-Based One-Time Password Algorithm
RFC 6238

Document Type RFC - Informational (May 2011; Errata)
Was draft-mraihi-totp-timebased (individual in sec area)
Last updated 2013-03-02
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IESG IESG state RFC 6238 (Informational)
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Responsible AD spt
IESG note Hannes Tschofenig (Hannes.Tschofenig@gmx.net) is the document shepherd.
Send notices to smachani@diversinet.com, mpei@verisign.com, johan.rydell@portwise.com, draft-mraihi-totp-timebased@ietf.org, Hannes.Tschofenig@gmx.net
Internet Engineering Task Force (IETF)                        D. M'Raihi
Request for Comments: 6238                                Verisign, Inc.
Category: Informational                                       S. Machani
ISSN: 2070-1721                                         Diversinet Corp.
                                                                  M. Pei
                                                                Symantec
                                                               J. Rydell
                                                          Portwise, Inc.
                                                                May 2011

              TOTP: Time-Based One-Time Password Algorithm

Abstract

   This document describes an extension of the One-Time Password (OTP)
   algorithm, namely the HMAC-based One-Time Password (HOTP) algorithm,
   as defined in RFC 4226, to support the time-based moving factor.  The
   HOTP algorithm specifies an event-based OTP algorithm, where the
   moving factor is an event counter.  The present work bases the moving
   factor on a time value.  A time-based variant of the OTP algorithm
   provides short-lived OTP values, which are desirable for enhanced
   security.

   The proposed algorithm can be used across a wide range of network
   applications, from remote Virtual Private Network (VPN) access and
   Wi-Fi network logon to transaction-oriented Web applications.  The
   authors believe that a common and shared algorithm will facilitate
   adoption of two-factor authentication on the Internet by enabling
   interoperability across commercial and open-source implementations.

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/rfc6238.

M'Raihi, et al.               Informational                     [Page 1]
RFC 6238                      HOTPTimeBased                     May 2011

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
   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 ....................................................2
      1.1. Scope ......................................................2
      1.2. Background .................................................3
   2. Notation and Terminology ........................................3
   3. Algorithm Requirements ..........................................3
   4. TOTP Algorithm ..................................................4
      4.1. Notations ..................................................4
      4.2. Description ................................................4
   5. Security Considerations .........................................5
      5.1. General ....................................................5
      5.2. Validation and Time-Step Size ..............................6
   6. Resynchronization ...............................................7
   7. Acknowledgements ................................................7
   8. References ......................................................8
      8.1. Normative References .......................................8
      8.2. Informative References .....................................8
   Appendix A. TOTP Algorithm: Reference Implementation ...............9
   Appendix B. Test Vectors ..........................................14

1.  Introduction

1.1.  Scope

   This document describes an extension of the One-Time Password (OTP)
   algorithm, namely the HMAC-based One-Time Password (HOTP) algorithm,
   as defined in [RFC4226], to support the time-based moving factor.

M'Raihi, et al.               Informational                     [Page 2]
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