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Versions: (draft-jones-oauth-amr-values) 00 01 02 03 04 05 06 07 08

OAuth Working Group                                             M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                                 P. Hunt
Expires: September 14, 2017                                       Oracle
                                                              A. Nadalin
                                                               Microsoft
                                                          March 13, 2017


                 Authentication Method Reference Values
                     draft-ietf-oauth-amr-values-08

Abstract

   The "amr" (Authentication Methods References) claim is defined and
   registered in the IANA "JSON Web Token Claims" registry but no
   standard Authentication Method Reference values are currently
   defined.  This specification establishes a registry for
   Authentication Method Reference values and defines an initial set of
   Authentication Method Reference values.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on September 14, 2017.

Copyright Notice

   Copyright (c) 2017 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



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   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.  Requirements Notation and Conventions . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Authentication Method Reference Values  . . . . . . . . . . .   4
   3.  Relationship to "acr" (Authentication Context Class
       Reference)  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Authentication Method Reference Values Registry . . . . .   7
       6.1.1.  Registration Template . . . . . . . . . . . . . . . .   8
       6.1.2.  Initial Registry Contents . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  13
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . .  14
   Appendix C.  Document History . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The "amr" (Authentication Methods References) claim is defined and
   registered in the IANA "JSON Web Token Claims" registry
   [IANA.JWT.Claims] but no standard Authentication Method Reference
   values are currently defined.  This specification establishes a
   registry for Authentication Method Reference values and defines an
   initial set of Authentication Method Reference values.

   For context, the "amr" (Authentication Methods References) claim is
   defined by Section 2 of the OpenID Connect Core 1.0 specification
   [OpenID.Core] as follows:

   amr
      OPTIONAL.  Authentication Methods References.  JSON array of
      strings that are identifiers for authentication methods used in
      the authentication.  For instance, values might indicate that both
      password and OTP authentication methods were used.  The definition
      of particular values to be used in the "amr" Claim is beyond the
      scope of this specification.  Parties using this claim will need
      to agree upon the meanings of the values used, which may be



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      context-specific.  The "amr" value is an array of case sensitive
      strings.

   Each "amr" value typically provides an identifier for a family of
   closely-related authentication methods.  For example, the "otp"
   identifier intentionally covers both time-based and HMAC-based OTPs.
   Many relying parties will be content to know that an OTP has been
   used in addition to a password; the distinction between which kind of
   OTP was used is not useful to them.  Thus, there's a single
   identifier that can be satisfied in two or more nearly equivalent
   ways.

   Similarly, there's a whole range of nuances between different
   fingerprint matching algorithms.  They differ in false positive and
   false negative rates over different population samples and also
   differ based on the kind and model of fingerprint sensor used.  Like
   the OTP case, many relying parties will be content to know that a
   fingerprint match mas made, without delving into and differentiating
   based on every aspect of the implementation of fingerprint capture
   and match.  The "fpt" identifier accomplishes this.

   Ultimately, the relying party is depending upon the identity provider
   to do reasonable things.  If it does not trust the identity provider
   to do so, it has no business using it.  The "amr" value lets the
   identity provider signal to the relying party additional information
   about what it did, for the cases in which that information is useful
   to the relying party.

   The "amr" values defined by this specification are not intended to be
   an exhaustive set covering all use cases.  Additional values can and
   will be added to the registry by other specifications.  Rather, the
   values defined herein are an intentionally small set that are already
   actually being used in practice.

   The values defined by this specification only make distinctions that
   are known to be useful to relying parties.  Slicing things more
   finely than would be used in practice would actually hurt interop,
   rather than helping it, because it would force relying parties to
   recognize that several or many different values actually mean the
   same thing to them.

   For context, while the claim values registered pertain to
   authentication, note that OAuth 2.0 [RFC6749] is designed for
   resource authorization and cannot be used for authentication without
   employing appropriate extensions, such as those defined by OpenID
   Connect Core 1.0 [OpenID.Core].  The existence of the "amr" claim and
   values for it should not be taken as encouragement to try to use




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   OAuth 2.0 for authentication without employing extensions enabling
   secure authentication to be performed.

   When used with OpenID Connect, if the identity provider supplies an
   "amr" claim in the ID Token resulting from a successful
   authentication, the relying party can inspect the values returned and
   thereby learn details about how the authentication was performed.
   For instance, the relying party might learn that only a password was
   used or it might learn that iris recognition was used in combination
   with a hardware-secured key.  Whether "amr" values are provided and
   which values are understood by what parties are both beyond the scope
   of this specification.  The OpenID Connect MODRNA Authentication
   Profile 1.0 [OpenID.MODRNA] is one example of an application context
   that uses "amr" values defined by this specification.

1.1.  Requirements Notation and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

1.2.  Terminology

   This specification uses the terms defined by JSON Web Token (JWT)
   [JWT] and OpenID Connect Core 1.0 [OpenID.Core].

2.  Authentication Method Reference Values

   The following is a list of Authentication Method Reference values
   defined by this specification:

   face
      Biometric authentication [RFC4949] using facial recognition

   fpt
      Biometric authentication [RFC4949] using a fingerprint

   geo
      Use of geolocation information for authentication, such as that
      provided by [W3C.REC-geolocation-API-20161108]

   hwk
      Proof-of-possession (PoP) of a hardware-secured key.  See
      Appendix C of [RFC4211] for a discussion on PoP.

   iris
      Biometric authentication [RFC4949] using an iris scan



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   kba
      Knowledge-based authentication [NIST.800-63-2] [ISO29115]

   mca
      Multiple-channel authentication [MCA].  The authentication
      involves communication over more than one distinct communication
      channel.  For instance, a multiple-channel authentication might
      involve both entering information into a workstation's browser and
      providing information on a telephone call to a pre-registered
      number.

   mfa
      Multiple-factor authentication [NIST.800-63-2]  [ISO29115].  When
      this is present, specific authentication methods used may also be
      included.

   otp
      One-time password [RFC4949].  One-time password specifications
      that this authentication method applies to include [RFC4226] and
      [RFC6238].

   pin
      Personal Identification Number (PIN) [RFC4949] or pattern (not
      restricted to containing only numbers) that a user enters to
      unlock a key on the device.  This mechanism should have a way to
      deter an attacker from obtaining the PIN by trying repeated
      guesses.

   pwd
      Password-based authentication [RFC4949]

   rba
      Risk-based authentication [JECM]

   retina
      Biometric authentication [RFC4949] using a retina scan

   sc
      Smart card [RFC4949]

   sms
      Confirmation using SMS [SMS] text message to the user at a
      registered number

   swk
      Proof-of-possession (PoP) of a software-secured key.  See
      Appendix C of [RFC4211] for a discussion on PoP.




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   tel
      Confirmation by telephone call to the user at a registered number.
      This authentication technique is sometimes also referred to as
      "call back" [RFC4949].

   user
      User presence test.  Evidence that the end-user is present and
      interacting with the device.  This is sometimes also referred to
      as "test of user presence" [W3C.WD-webauthn-20170216].

   vbm
      Biometric authentication [RFC4949] using a voiceprint

   wia
      Windows integrated authentication [MSDN]

3.  Relationship to "acr" (Authentication Context Class Reference)

   The "acr" (Authentication Context Class Reference) claim and
   "acr_values" request parameter are related to the "amr"
   (Authentication Methods References) claim, but with important
   differences.  An Authentication Context Class specifies a set of
   business rules that authentications are being requested to satisfy.
   These rules can often be satisfied by using a number of different
   specific authentication methods, either singly or in combination.
   Interactions using "acr_values" request that the specified
   Authentication Context Classes be used and that the result should
   contain an "acr" claim saying which Authentication Context Class was
   satisfied.  The "acr" claim in the reply states that the business
   rules for the class were satisfied -- not how they were satisfied.

   In contrast, interactions using the "amr" claim make statements about
   the particular authentication methods that were used.  This tends to
   be more brittle than using "acr", since the authentication methods
   that may be appropriate for a given authentication will vary over
   time, both because of the evolution of attacks on existing methods
   and the deployment of new authentication methods.

4.  Privacy Considerations

   The list of "amr" claim values returned in an ID Token reveals
   information about the way that the end-user authenticated to the
   identity provider.  In some cases, this information may have privacy
   implications.

   While this specification defines identifiers for particular kinds of
   credentials, it does not define how these credentials are stored or
   protected.  For instance, ensuring the security and privacy of



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   biometric credentials that are referenced by some of the defined
   Authentication Method Reference values is beyond the scope of this
   specification.

5.  Security Considerations

   The security considerations in OpenID Connect Core 1.0 [OpenID.Core]
   and OAuth 2.0 [RFC6749] and the OAuth 2.0 Threat Model [RFC6819]
   apply to applications using this specification.

   As described in Section 3, taking a dependence upon particular
   authentication methods may result in brittle systems since the
   authentication methods that may be appropriate for a given
   authentication will vary over time.

6.  IANA Considerations

6.1.  Authentication Method Reference Values Registry

   This specification establishes the IANA "Authentication Method
   Reference Values" registry for "amr" claim array element values.  The
   registry records the Authentication Method Reference value and a
   reference to the specification that defines it.  This specification
   registers the Authentication Method Reference values defined in
   Section 2.

   Values are registered on an Expert Review [RFC5226] basis after a
   three-week review period on the jwt-reg-review@ietf.org mailing list,
   on the advice of one or more Designated Experts.  To increase
   potential interoperability, the experts are requested to encourage
   registrants to provide the location of a publicly-accessible
   specification defining the values being registered, so that their
   intended usage can be more easily understood.

   Registration requests sent to the mailing list for review should use
   an appropriate subject (e.g., "Request to register Authentication
   Method Reference value: otp").

   Within the review period, the Designated Experts will either approve
   or deny the registration request, communicating this decision to the
   review list and IANA.  Denials should include an explanation and, if
   applicable, suggestions as to how to make the request successful.
   Registration requests that are undetermined for a period longer than
   21 days can be brought to the IESG's attention (using the
   iesg@ietf.org mailing list) for resolution.






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   IANA must only accept registry updates from the Designated Experts
   and should direct all requests for registration to the review mailing
   list.

   It is suggested that the same Designated Experts evaluate these
   registration requests as those who evaluate registration requests for
   the IANA "JSON Web Token Claims" registry [IANA.JWT.Claims].

   Criteria that should be applied by the Designated Experts includes
   determining whether the proposed registration duplicates existing
   functionality, whether it is likely to be of general applicability or
   whether it is useful only for a single application, whether the value
   is actually being used, and whether the registration description is
   clear.

6.1.1.  Registration Template

   Authentication Method Reference Name:
      The name requested (e.g., "otp") for the authentication method or
      family of closely-related authentication methods.  Because a core
      goal of this specification is for the resulting representations to
      be compact, it is RECOMMENDED that the name be short -- that is,
      not to exceed 8 characters without a compelling reason to do so.
      To facilitate interoperability, the name must use only printable
      ASCII characters excluding double quote ('"') and backslash ('\')
      (the Unicode characters with code points U+0021, U+0023 through
      U+005B, and U+005D through U+007E).  This name is case sensitive.
      Names may not match other registered names in a case-insensitive
      manner unless the Designated Experts state that there is a
      compelling reason to allow an exception.

   Authentication Method Reference Description:
      Brief description of the Authentication Method Reference (e.g.,
      "One-time password").

   Change Controller:
      For Standards Track RFCs, state "IESG".  For others, give the name
      of the responsible party.  Other details (e.g., postal address,
      email address, home page URI) may also be included.

   Specification Document(s):
      Reference to the document or documents that specify the parameter,
      preferably including URIs that can be used to retrieve copies of
      the documents.  An indication of the relevant sections may also be
      included but is not required.






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6.1.2.  Initial Registry Contents

   o  Authentication Method Reference Name: "face"
   o  Authentication Method Reference Description: Facial recognition
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "fpt"
   o  Authentication Method Reference Description: Fingerprint biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "geo"
   o  Authentication Method Reference Description: Geolocation
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "hwk"
   o  Authentication Method Reference Description: Proof-of-possession
      of a hardware-secured key
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "iris"
   o  Authentication Method Reference Description: Iris scan biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "kba"
   o  Authentication Method Reference Description: Knowledge-based
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "mca"
   o  Authentication Method Reference Description: Multiple-channel
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "mfa"
   o  Authentication Method Reference Description: Multiple-factor
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "otp"
   o  Authentication Method Reference Description: One-time password



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   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "pin"
   o  Authentication Method Reference Description: Personal
      Identification Number or pattern
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "pwd"
   o  Authentication Method Reference Description: Password-based
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "rba"
   o  Authentication Method Reference Description: Risk-based
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "retina"
   o  Authentication Method Reference Description: Retina scan biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "sc"
   o  Authentication Method Reference Description: Smart card
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "sms"
   o  Authentication Method Reference Description: Confirmation using
      SMS
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "swk"
   o  Authentication Method Reference Description: Proof-of-possession
      of a software-secured key
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "tel"
   o  Authentication Method Reference Description: Confirmation by
      telephone call
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]



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   o  Authentication Method Reference Name: "user"
   o  Authentication Method Reference Description: User presence test
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "vbm"
   o  Authentication Method Reference Description: Voice biometric
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

   o  Authentication Method Reference Name: "wia"
   o  Authentication Method Reference Description: Windows integrated
      authentication
   o  Change Controller: IESG
   o  Specification Document(s): Section 2 of [[ this specification ]]

7.  References

7.1.  Normative References

   [IANA.JWT.Claims]
              IANA, "JSON Web Token Claims",
              <http://www.iana.org/assignments/jwt>.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, May 2015,
              <http://www.rfc-editor.org/info/rfc7519>.

   [OpenID.Core]
              Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
              C. Mortimore, "OpenID Connect Core 1.0", November 2014,
              <http://openid.net/specs/openid-connect-core-1_0.html>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <http://www.rfc-editor.org/info/rfc6749>.





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7.2.  Informative References

   [ISO29115]
              International Organization for Standardization, "ISO/IEC
              29115:2013 -- Information technology - Security techniques
              - Entity authentication assurance framework", ISO/
              IEC 29115:2013, April 2013,
              <http://www.iso.org/iso/iso_catalogue/catalogue_tc/
              catalogue_detail.htm?csnumber=45138>.

   [JECM]     Williamson, G., "Enhanced Authentication In Online
              Banking", Journal of Economic Crime Management 4.2: 18-19,
              2006,
              <http://utica.edu/academic/institutes/ecii/publications/
              articles/51D6D996-90F2-F468-AC09C4E8071575AE.pdf>.

   [MCA]      ldapwiki.com, "Multiple-channel Authentication", August
              2016, <https://www.ldapwiki.com/wiki/Multiple-
              channel%20Authentication>.

   [MSDN]     Microsoft, "Integrated Windows Authentication with
              Negotiate", September 2011,
              <http://blogs.msdn.com/b/benjaminperkins/
              archive/2011/09/14/iis-integrated-windows-authentication-
              with-negotiate.aspx>.

   [NIST.800-63-2]
              National Institute of Standards and Technology (NIST),
              "Electronic Authentication Guideline", NIST Special
              Publication 800-63-2, August 2013,
              <http://nvlpubs.nist.gov/nistpubs/SpecialPublications/
              NIST.SP.800-63-2.pdf>.

   [OpenID.MODRNA]
              Connotte, J. and J. Bradley, "OpenID Connect MODRNA
              Authentication Profile 1.0", March 2017,
              <http://openid.net/specs/
              openid-connect-modrna-authentication-1_0.html>.

   [RFC4211]  Schaad, J., "Internet X.509 Public Key Infrastructure
              Certificate Request Message Format (CRMF)", RFC 4211,
              DOI 10.17487/RFC4211, September 2005,
              <http://www.rfc-editor.org/info/rfc4211>.

   [RFC4226]  M'Raihi, D., Bellare, M., Hoornaert, F., Naccache, D., and
              O. Ranen, "HOTP: An HMAC-Based One-Time Password
              Algorithm", RFC 4226, DOI 10.17487/RFC4226, December 2005,
              <http://www.rfc-editor.org/info/rfc4226>.



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   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <http://www.rfc-editor.org/info/rfc4949>.

   [RFC6238]  M'Raihi, D., Machani, S., Pei, M., and J. Rydell, "TOTP:
              Time-Based One-Time Password Algorithm", RFC 6238,
              DOI 10.17487/RFC6238, May 2011,
              <http://www.rfc-editor.org/info/rfc6238>.

   [RFC6819]  Lodderstedt, T., Ed., McGloin, M., and P. Hunt, "OAuth 2.0
              Threat Model and Security Considerations", RFC 6819,
              DOI 10.17487/RFC6819, January 2013,
              <http://www.rfc-editor.org/info/rfc6819>.

   [SMS]      3rd Generation Partnership Project, "Technical realization
              of the Short Message Service (SMS)", 3GPP Technical
              Specification (TS) 03.40 V7.5.0 (2001-12), January 2002,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=141>.

   [W3C.REC-geolocation-API-20161108]
              Popescu, A., "Geolocation API Specification 2nd Edition",
              World Wide Web Consortium Recommendation REC-geolocation-
              API-20161108, November 2016, <https://www.w3.org/TR/2016/
              REC-geolocation-API-20161108>.

   [W3C.WD-webauthn-20170216]
              Bharadwaj, V., Le Van Gong, H., Balfanz, D., Czeskis, A.,
              Birgisson, A., Hodges, J., Jones, M., Lindemann, R., and
              J. Jones, "Web Authentication: An API for accessing Scoped
              Credentials", World Wide Web Consortium Working Draft WD-
              webauthn-20170216, February 2017,
              <http://www.w3.org/TR/2017/WD-webauthn-20170216/>.

Appendix A.  Examples

   In some cases, the "amr" claim value returned may contain a single
   Authentication Method Reference value.  For example, the following
   "amr" claim value indicates that the authentication performed used an
   iris scan biometric:

     "amr": ["iris"]

   In other cases, the "amr" claim value returned may contain multiple
   Authentication Method Reference values.  For example, the following
   "amr" claim value indicates that the authentication performed used a
   password and knowledge-based authentication:




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     "amr": ["pwd", "kba"]

Appendix B.  Acknowledgements

   Caleb Baker participated in specifying the original set of "amr"
   values.  Jari Arkko, John Bradley, Ben Campbell, Brian Campbell,
   William Denniss, Linda Dunbar, Stephen Farrell, Paul Kyzivat, Elaine
   Newton, James Manger, Catherine Meadows, Alexey Melnikov, Kathleen
   Moriarty, Nat Sakimura, and Mike Schwartz provided reviews of the
   specification.

Appendix C.  Document History

   [[ to be removed by the RFC editor before publication as an RFC ]]

   -08

   o  Added text in the IANA Registration Template saying that names can
      be for families of closely-related authentication methods, as
      suggested by Stephen Farrell.

   -07

   o  Clarified that the values are intended to provide identifiers for
      families of closely-related authentication methods.
   o  Updated the MODRNA Authentication Profile reference.

   -06

   o  Addressed IESG comments.  Identifiers are now restricted to using
      only printable JSON-friendly ASCII characters.  Additional
      references to documentation relevant to specific AMR values were
      added.

   -05

   o  Specified characters allowed in "amr" values, reusing the IANA
      Considerations language on this topic from RFC 7638.

   -04

   o  Added examples with single and multiple values.
   o  Clarified that the actual credentials referenced are not part of
      this specification to avoid additional privacy concerns for
      biometric data.
   o  Clarified that the OAuth 2.0 Threat Model [RFC6819] applies to
      applications using this specification.




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   -03

   o  Addressed shepherd comments.

   -02

   o  Addressed working group last call comments.

   -01

   o  Distinguished between retina and iris biometrics.
   o  Expanded the introduction to provide additional context to
      readers.
   o  Referenced the OpenID Connect MODRNA Authentication Profile 1.0
      specification, which uses "amr" values defined by this
      specification.

   -00

   o  Created the initial working group draft from draft-jones-oauth-
      amr-values-05 with no normative changes.

Authors' Addresses

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/


   Phil Hunt
   Oracle

   Email: phil.hunt@yahoo.com


   Anthony Nadalin
   Microsoft

   Email: tonynad@microsoft.com










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