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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 8225

STIR                                                            C. Wendt
Internet-Draft                                                   Comcast
Intended status: Standards Track                             J. Peterson
Expires: November 25, 2016                                  Neustar Inc.
                                                            May 24, 2016


                        Persona Assertion Token
                      draft-ietf-stir-passport-02

Abstract

   This document defines a token format for verifying with non-
   repudiation the sender of and authorization to send information
   related to the originator of personal communications.  A
   cryptographic signature is defined to protect the integrity of the
   information used to identify the originator of a personal
   communications session (e.g. the telephone number or URI) and verify
   the accuracy of this information at the destination.  The
   cryptographic signature is defined with the intention that it can
   confidently verify the originating persona even when the signature is
   sent to the destination party over an unsecure channel.  The Persona
   Assertion Token (PASSporT) is particularly useful for many personal
   communications applications over IP networks and other multi-hop
   interconnection scenarios where the originating and destination
   parties may not have a direct trusted relationship.

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 November 25, 2016.








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Copyright Notice

   Copyright (c) 2016 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Token Overview  . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  PASSporT Definition . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  PASSporT Header . . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  "typ" (Type) Header Parameter . . . . . . . . . . . .   4
       3.1.2.  "alg" (Algorithm) Header Parameter  . . . . . . . . .   5
       3.1.3.  "x5u" (X.509 URL) Header Parameter  . . . . . . . . .   5
     3.2.  PASSporT Payload  . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  JWT defined claims  . . . . . . . . . . . . . . . . .   5
         3.2.1.1.  "iat" - Issued at claim . . . . . . . . . . . . .   6
       3.2.2.  PASSporT specific claims  . . . . . . . . . . . . . .   6
         3.2.2.1.  Originating and Destination Identities  . . . . .   6
         3.2.2.2.  "mky" - Media Key claim . . . . . . . . . . . . .   7
       3.2.3.  Multi-party Communications  . . . . . . . . . . . . .   8
     3.3.  PASSporT Signature  . . . . . . . . . . . . . . . . . . .   8
   4.  Extending PASSporT  . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  "ppt" (PASSporT) header parameter . . . . . . . . . . . .   8
     4.2.  Extended PASSporT Claims  . . . . . . . . . . . . . . . .   9
     4.3.  Alternate PASSporT Extension  . . . . . . . . . . . . . .   9
     4.4.  Registering PASSporT Extensions . . . . . . . . . . . . .   9
   5.  Deterministic JSON Serialization  . . . . . . . . . . . . . .   9
     5.1.  Example PASSport deterministic JSON form  . . . . . . . .  10
   6.  Human Readability . . . . . . . . . . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
     7.1.  Avoidance of replay and cut and paste attacks . . . . . .  10
     7.2.  Solution Considerations . . . . . . . . . . . . . . . . .  11
     7.3.  Privacy Considerations  . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  Media Type Registration . . . . . . . . . . . . . . . . .  12
       8.1.1.  Media Type Registry Contents Additions Requested  . .  12
     8.2.  JSON Web Token Claims Registration  . . . . . . . . . . .  13



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       8.2.1.  Registry Contents Additions Requested . . . . . . . .  13
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
   Appendix A.  Example ES256 base PASSporT JWS Serialization and
                Signature  . . . . . . . . . . . . . . . . . . . . .  15
     A.1.  X.509 Private Key Certificate for Example in Appendix A .  17
     A.2.  X.509 Public Key Certificate for Example in Appendix A  .  17
   Appendix B.  Example RS256 base PASSporT JWS Serialization and
                Signature  . . . . . . . . . . . . . . . . . . . . .  17
     B.1.  X.509 Private Key Certificate for Example in Appendix A .  19
     B.2.  X.509 Public Key Certificate for Example in Appendix A  .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   In today's IP-enabled telecommunications world, there is a growing
   concern about the ability to trust incoming invitations for
   communications sessions, including video, voice and messaging.  As an
   example, modern telephone networks provide the ability to spoof the
   calling party telephone number for many legitimate purposes including
   providing network features and services on the behalf of a legitimate
   telephone number.  However, as we have seen, bad actors have taken
   advantage of this ability for illegitimate and fraudulent purposes
   meant to trick telephone users to believe they are someone they are
   not.  This problem can be extended to many emerging forms of personal
   communications.

   This document defines a common method for creating and validating a
   token that cryptographically verifies an originating identity, or
   more generally a URI or application specific identity string
   representing the originator of personal communications.  Through
   extended profiles other information relevant to the personal
   communications can also be attached to the token.  The primary goal
   of PASSporT is to provide a common framework for signing persona
   related information in an extensible way.  A secondary goal is to
   provide this functionality independent of any specific personal
   communications signaling call logic, so that creation and
   verification of persona information can be implemented in a flexible
   way and can be used in many personal communications applications
   including end-to-end applications that require different signaling
   protocols.  It is anticipated that signaling protocol specific
   guidance will be provided in other related documents and
   specifications to specify how to use and transport PASSporT tokens,
   however this is intentionally out of scope for this document.

   Note: As of the authoring of this document,
   [I-D.ietf-stir-rfc4474bis] provides details of how to use PASSporT




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   within SIP signaling for the signing and verification of telephone
   numbers.

2.  Token Overview

   Tokens are a convenient way of encapsulating information with
   associated digital signatures.  They are used in many applications
   that require authentication, authorization, encryption, non-
   repudiation and other use cases.  JSON Web Token (JWT) [RFC7519] and
   JSON Web Signature (JWS) [RFC7515] are designed to provide a compact
   form for many of these purposes and define a specific method and
   syntax for signing a specific set of information or "claims" within
   the token and therefore providing an extensible set of claims.
   Additionally, JWS provides extensible mechanisms for specifying the
   method and cryptographic algorithms used for the associated digital
   signatures.

3.  PASSporT Definition

   The PASSporT is constructed based on JWT [RFC7519] and JWS [RFC7515]
   specifications.  JWS defines the use of JSON data structures in a
   specified canonical format for signing data corresponding to JOSE
   header, JWS Payload, and JWS Signature.  JWT defines specific set of
   claims that are represented by specified key value pairs which can be
   extended with custom keys for specific applications.

3.1.  PASSporT Header

   The JWS token header is a JOSE header [RFC7515] that defines the type
   and encryption algorithm used in the token.

   An example of the header for the case of an ECDSA P-256 digital
   signature would be the following,

       {
           "typ":"passport",
           "alg":"ES256",
           "x5u":"https://cert.example.org/passport.crt"
       }

3.1.1.  "typ" (Type) Header Parameter

   JWS defines the "typ" (Type) Header Parameter to declare the media
   type [IANA.MediaTypes] of the JWS.

   For PASSporT Token the "typ" header MUST minimally include and begin
   with "passport".  This represents that the encoded token is a JWT of
   type passport.  Note with extensions explained later in this



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   document, the typ may be another value if defined as a passport
   extension.

3.1.2.  "alg" (Algorithm) Header Parameter

   For PASSporT, the "alg" should be defined as follows, for the
   creation of PASSporT tokens and their corresponding digital
   signatures,

   o  ES256 MUST be implemented.

   o  RS256 SHOULD be implemented

   For the verification of PASSporT tokens, both ES256 and RS256 MUST be
   supported.

   Note that JWA [RFC7518] defines other algorithms that may be utilized
   or updated in the future depending on cryptographic strength
   requirements guided by current security best practice.

3.1.3.  "x5u" (X.509 URL) Header Parameter

   As defined in JWS, the "x5u" header parameter is used to provide a
   URI [RFC3986] referring to the resource for the X.509 public key
   certificate or certificate chain [RFC5280] corresponding to the key
   used to digitally sign the JWS.  Note: The definition of what the URI
   represents in terms of the actor serving the X.509 public key is out
   of scope of this document.  However, generally this would correspond
   to an HTTPS or DNSSEC resource with the guidance that it MUST be a
   TLS protected, per JWS spec.

3.2.  PASSporT Payload

   The token payload claims should consist of the information which
   needs to be verified at the destination party.  This claim should
   correspond to a JWT claim [RFC7519] and be encoded as defined by the
   JWS Payload [RFC7515]

   The PASSporT defines the use of a number of standard JWT defined
   headers as well as two new custom headers corresponding to the two
   parties associated with personal communications, the originator and
   terminator.  These headers or key value pairs are detailed below.

3.2.1.  JWT defined claims







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3.2.1.1.  "iat" - Issued at claim

   The JSON claim MUST include the "iat" [RFC7519] defined claim issued
   at.  As defined this should be set to a date cooresponding to the
   origination of the personal communications.  The time value should be
   of the format defined in [RFC7519] Section 2 NumericDate.  This is
   included for securing the token against replay and cut and paste
   attacks, as explained further in the security considerations in
   section 7.

3.2.2.  PASSporT specific claims

3.2.2.1.  Originating and Destination Identities

   Baseline PASSporT defines claims that convey the identity of the
   origination and destination of personal communications represented as
   either telephone numbers or Uniform Resource Indicators (URIs).  Some
   using protocols may require other identifiers for personae; these may
   be specified as claims through the PASSporT extensibility mechanisms.
   But for telephone numbers and URIs, the following claims should be
   used:

3.2.2.1.1.  "otn" and "dtn" - Originating and Destination Telephone
            Number claim

   If the originating identity is a telephone number, the claim "otn"
   SHOULD be included.  If the destination identity is a telephone
   number, the claim "dtn" SHOULD be included.

   Telephone Number strings for "otn" and "dtn" claims MUST be
   canonicalized according to the procedures specified in
   [I-D.ietf-stir-rfc4474bis] Section 6.1.1.

3.2.2.1.2.  "ouri" and "duri" - Originating and Destination URI claims

   If the originating identity is not a telephone number, the claim
   "ouri" SHOULD be included with the string cooresponding to the URI
   form of the identity as defined in [RFC3986], alternatively it could
   also contain an application specific identity string, if URI format
   is not appropriate.

   If the destination identity is not a telephone number, the claim
   "duri" SHOULD be included.  The same string format rules apply as
   stated for "ouri".







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3.2.2.2.  "mky" - Media Key claim

   Some protocols that use PASSporT convey hashes for media security
   keys within their signaling in order to bind those keys to the
   identities established in the signaling layers.  One example would be
   the DTLS-SRTP key fingerprints carried in SDP via the "a=fingerprint"
   attribute; multiple instances of that fingerprint may appear in a
   single SDP body corresponding to difference media streams offered.
   The "mky" value of PASSporT contains a hexadecimal key presentation
   of any hash(es) necessary to establish media security via DTLS-SRTP.
   This mky value should be formated in a JSON form including the
   'algorithm' and 'digest' keys with the corresponding algorithm and
   hexadecimal values.  Note that per guidance of Section 5 of this
   document any whitespace and line feeds must be removed.  If there is
   multiple fingerprint values, more than one, the fingerprint values
   should be constructed as a JSON array denoted by bracket characters.

   An example claim with "mky" claim is as follows:

   For an SDP offer that includes the following fingerprint values,

       a=fingerprint:sha-256 02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65:
       2E:7D:46:3F:54:42:CD:54:F1:7A:03:A2:7D:F9:B0:7F:46:19:B2
       a=fingerprint:sha-256 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:
       5D:49:6B:19:E5:7C:AB:3E:4B:65:2E:7D:46:3F:54:42:CD:54:F1

   the PASSporT Payload object would be:

       {
           "iat":"1443208345",
           "otn":"12155551212",
           "duri":"sip:alice@example.com",
           "mky":"[
           {
               "algorithm":"sha-256",
               "digest":"02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65:2E:7D:
                   46:3F:54:42:CD:54:F1:7A:03:A2:7D:F9:B0:7F:46:19:B2"
           },
           {
               "algorithm":"sha-256",
               "digest":"4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:
               6B:19:E5:7C:AB:3E:4B:65:2E:7D:46:3F:54:42:CD:54:F1"
           }]"
       }







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3.2.3.  Multi-party Communications

   Personal communications in the context of PASSporT can certainly
   extend to multi-party scenerios where there is more than one
   destination identity.  In the future, it is anticipated that PASSporT
   will be extended to support these cases.

3.3.  PASSporT Signature

   The signature of the PASSporT is created as specified by JWS using
   the private key corresponding to the X.509 public key certificate
   referenced by the "x5u" header parameter.

4.  Extending PASSporT

   PASSporT represents the bare minimum set of claims needed to assert
   the originating identity, however there will certainly be new and
   extended applications and usage of PASSPorT that will need to extend
   the claims to represent other information specific to the origination
   identities beyond the identity itself.

   There are two mechanisms defined to extend PASSporT.  The first
   includes an extension of the base passport claims to include
   additional claims.  An alternative method of extending PASSporT is
   for applications of PASSporT unrelated to the base set of claims,
   that will define it's own set of claims.  Both are described below.

4.1.  "ppt" (PASSporT) header parameter

   For extended profiles of PASSporT, a new JWS header parameter "ppt"
   MUST be used with a string that uniquely identifies the profile
   specification that defines any new claims that would extend the base
   set of claims of PASSporT.

   An example header with an extended PASSporT profile of "foo" is as
   follows:

       {
           "typ":"passport",
           "ppt":"foo",
           "alg":"ES256",
           "x5u":"https://tel.example.org/passport.crt"
       }








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4.2.  Extended PASSporT Claims

   Future specifications that define such extensions to the PASSporT
   mechanism MUST explicitly designate what claims they include, the
   order in which they will appear, and any further information
   necessary to implement the extension.  All extensions MUST
   incorporate the baseline JWT elements specified in Section 3; claims
   may only be appended to the claims object specified; they can never
   be subtracted or re-ordered.  Specifying new claims follows the
   baseline JWT procedures ([RFC7519] Section 10.1).  Note that
   understanding an extension as a verifier is always optional for
   compliance with this specification (though future specifications or
   profiles for deployment environments may make other "ppt" values
   mandatory).  The creator of a PASSporT object cannot assume that
   verifiers will understand any given extension.  Verifiers that do
   support an extension may then trigger appropriate application-level
   behavior in the presence of an extension; authors of extensions
   should provide appropriate extension-specific guidance to application
   developers on this point.

4.3.  Alternate PASSporT Extension

   Some applications may want to use the mechanism of the PASSporT
   digital signature that is not a superset of the base set of claims of
   the PASSporT token as defined in Section 3.  Rather, a specification
   may use PASSporT with its own defined set of claims.

   In this case, the specification SHOULD define its own MIME media type
   [RFC2046] in the "Media Types" registry [IANA.MediaTypes].  The MIME
   subtype SHOULD start with the string "passport-" to signify that it
   is related to the PASSporT token.  For example, for the "foo"
   application the MIME type/sub-type could be defined as "application/
   passport-foo".

4.4.  Registering PASSporT Extensions

   Toward interoperability and to maintain uniqueness of the extended
   PASSporT profile header parameter string, there SHOULD be an industry
   registry that tracks the definition of the profile strings.

5.  Deterministic JSON Serialization

   In order to provide a deterministic representation of the PASSporT
   Header and Claims, particularly if PASSporT is used across multiple
   signaling environments, the JSON header object and JSON Claim object
   MUST be computed as follows.





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   The JSON object MUST follow the rules for the construction of the
   thumbprint of a JSON Web Key (JWK) as defined in [RFC7638] Section 3.
   Each JSON object MUST contain no whitespace or line breaks before or
   after any syntactic elements and with the required members ordered
   lexicographically by the Unicode [UNICODE] code points of the member
   names.

   In addition, the JSON header and claim members MUST follow the
   lexicographical ordering and character and string rules defined in
   [RFC7638] Section 3.3.

5.1.  Example PASSport deterministic JSON form

   For the example PASSporT Payload shown in Section 3.2.2.2, the
   following is the deterministic JSON object form.

       {"iat": 1443208345,"otn":"12155551212","duri":
       "sip:alice@example.com","mky":{"algorithm":"sha-256","digest":
       "02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65:2E:7D:46:3F:54:42:CD:54:
       F1:7A:03:A2:7D:F9:B0:7F:46:19:B2;sha-256 4A:AD:B9:B1:3F:82:18:
       3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB:3E:4B:65:2E:7D:46:3F:54:
       42:CD:54:F1"}}

6.  Human Readability

   JWT [RFC7519] and JWS [RFC7515] are defined to use Base64 and/or UTF8
   encoding to the Header, Payload, and Signature sections.  However,
   many personal communications protocols, such as SIP and XMPP, use a
   "human readable" format to allow for ease of use and ease of
   operational debugging and monitoring.  As such, specifications using
   PASSporT may provide guidance on whether Base64 encoding or plain
   text will be used for the construction of the PASSporT Header and
   Claim sections.

7.  Security Considerations

7.1.  Avoidance of replay and cut and paste attacks

   There are a number of security considerations for use of the token
   for avoidance of replay and cut and paste attacks.  PASSporT tokens
   must be sent along with other application level protocol information
   (e.g. for SIP an INVITE as defined in [RFC3261]).  There should be a
   link between various information provided in the token and
   information provided by the application level protocol information.

   These would include:





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   o  "iat" claim should closely correspond to a date/time the message
      was originated.  It should also be within a relative delta time
      that is reasonable for clock drift and transmission time
      characteristics associated with the application using the PASSporT
      token.

   o  either "dtn" claim or "duri" claim is included to prevent the
      ability to use a previously originated message to send to another
      destination party

7.2.  Solution Considerations

   It should be recognized that the use of this token should not, in
   it's own right, be considered a full solution for absolute non-
   repudiation of the persona being asserted.  This only provides non-
   repudiation of the signer of PASSporT.  If the signer and the persona
   are not one in the same, which can and often will be the case in
   telecommunications networks today, protecting the destination party
   from being spoofed may take some interpretation or additional
   verification of the link between the PASSporT signature and the
   persona being asserted.

   In addition, the telecommunications systems and specifications that
   use PASSporT should in practice provide mechanisms for:

   o  Managing X.509 certificates and X.509 certificate chains to an
      authorized trust anchor that can be a trusted entity to all
      participants in the telecommunications network

   o  Accounting for entities that may route calls from other peer or
      interconnected telecommunications networks that are not part of
      the "trusted" communications network or may not be following the
      usage of PASSporT or the profile of PASSporT appropriate to that
      network

   o  Following best practices around management and security of X.509
      certificates

7.3.  Privacy Considerations

   Because PASSporT explicity includes claims of identitifiers of
   parties involved in communications, times, and potentially other call
   detail, care should be taken outside of traditional protected or
   private telephony communications paths where there may be concerns
   about exposing information to either unintended or illegitimately
   intented actors.  These identifiers are often exposed through many
   communications signaling protocols as of today, but appropriate
   precautions should be taken.



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8.  IANA Considerations

8.1.  Media Type Registration

8.1.1.  Media Type Registry Contents Additions Requested

   This section registers the "application/passport" media type
   [RFC2046] in the "Media Types" registry [IANA.MediaTypes] in the
   manner described in [RFC6838], which can be used to indicate that the
   content is a PASSporT defined JWT and JWS.

   o  Type name: application

   o  Subtype name: passport

   o  Required parameters: n/a

   o  Optional parameters: n/a

   o  Encoding considerations: 8bit; application/passport values are
      encoded as a series of base64url-encoded values (some of which may
      be the empty string), each separated from the next by a single
      period ('.') character.

   o  Security considerations: See the Security Considerations section
      of RFC 7515.

   o  Interoperability considerations: n/a

   o  Published specification: draft-ietf-stir-passport-00

   o  Applications that use this media type: STIR and other applications
      that require identity related assertion

   o  Fragment identifier considerations: n/a

   o  Additional information:

      *  Magic number(s): n/a

      *  File extension(s): n/a

      *  Macintosh file type code(s): n/a

   o  Person and email address to contact for further information: Chris
      Wendt, chris-ietf@chriswendt.net

   o  Intended usage: COMMON



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   o  Restrictions on usage: none

   o  Author: Chris Wendt, chris-ietf@chriswendt.net

   o  Change Controller: IESG

   o  Provisional registration?  No

8.2.  JSON Web Token Claims Registration

8.2.1.  Registry Contents Additions Requested

   o  Claim Name: "otn"

   o  Claim Description: Originating Telephone Number String

   o  Change Controller: IESG

   o  Specification Document(s): Section 3.2 of draft-ietf-stir-
      passport-00

   o  Claim Name: "dtn"

   o  Claim Description: Destination Telephone Number String

   o  Change Controller: IESG

   o  Specification Document(s): Section 3.2 of draft-ietf-stir-
      passport-00

   o  Claim Name: "ouri"

   o  Claim Description: Originating URI String

   o  Change Controller: IESG

   o  Specification Document(s): Section 3.2 of draft-ietf-stir-
      passport-00

   o  Claim Name: "duri"

   o  Claim Description: Destination URI String

   o  Change Controller: IESG

   o  Specification Document(s): Section 3.2 of draft-ietf-stir-
      passport-00




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   o  Claim Name: "mky"

   o  Claim Description: Media Key Fingerprint String

   o  Change Controller: IESG

   o  Specification Document(s): Section 3.2 of draft-ietf-stir-
      passport-00

9.  Acknowledgements

   Particular thanks to members of the ATIS and SIP Forum NNI Task Group
   including Jim McEchern, Martin Dolly, Richard Shockey, John Barnhill,
   Christer Holmberg, Victor Pascual Avila, Mary Barnes, and Eric Burger
   for their review, ideas, and contributions.  Also thanks to Henning
   Schulzrinne, Russ Housley, Alan Johnston, and Richard Barnes for
   valuable feedback on the technical and security aspects of the
   document.  Additional thanks to Harsha Bellur for assistance in
   coding the example tokens.

10.  References

   [I-D.ietf-stir-rfc4474bis]
              Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-07
              (work in progress), February 2016.

   [IANA.MediaTypes]
              "IANA, "Media Types"", <Media Types>.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <http://www.rfc-editor.org/info/rfc2046>.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.





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   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <http://www.rfc-editor.org/info/rfc6838>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <http://www.rfc-editor.org/info/rfc7515>.

   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <http://www.rfc-editor.org/info/rfc7518>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <http://www.rfc-editor.org/info/rfc7519>.

   [RFC7638]  Jones, M. and N. Sakimura, "JSON Web Key (JWK)
              Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
              2015, <http://www.rfc-editor.org/info/rfc7638>.

   [UNICODE]  "The Unicode Consortium, "The Unicode Standard"",
              <http://www.unicode.org/versions/latest/>.

Appendix A.  Example ES256 base PASSporT JWS Serialization and Signature

   For PASSporT, there will always be a JWS with the following members:

   o  "protected", with the value BASE64URL(UTF8(JWS Protected Header))

   o  "payload", with the value BASE64URL (JWS Payload)

   o  "signature", with the value BASE64URL(JWS Signature)

   Note: there will never be a JWS Unprotected Header for PASSporT.

   First, an example PASSporT Protected Header is as follows:








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       {
           "typ":"passport",
           "alg":"ES256",
           "x5u":"https://cert.example.org/passport.crt"
       }

   This would be serialized to the form:

       {"typ":"passport","alg":"ES256","x5u":"https://cert.example.org/
       passport.crt"}

   Encoding this with UTF8 and BASE64 encoding produces this value:

       eyJ0eXAiOiJwYXNzcG9ydCIsImFsZyI6IkVTMjU2IiwieDV1IjoiaHR0cHM6Ly9j
       ZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNydCJ9

   Second, an example PASSporT Payload is as follows:

       {
           "iat":"1443208345",
           "otn":"12155551212",
           "duri":"sip:alice@example.com"
       }

   This would be serialized to the form:

       {"iat":"1443208345","otn":"12155551212","duri":
       "sip:alice@example.com"}

   Encoding this with the UTF8 and BASE64 encoding produces this value:

       eyJpYXQiOiIxNDQzMjA4MzQ1Iiwib3RuIjoiMTIxNTU1NTEyMTIiLCJkdXJp
       Ijoic2lwOmFsaWNlQGV4YW1wbGUuY29tIn0

   Computing the digital signature of the PASSporT Signing Input
   ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS
   Payload))

       KK89q2RFY-BkKQQhiB0z6-fIaFUy6NDyUboKXOix9XnYLxTCjdw1UHjCbw4Ce
       feKwH_t7W-bnGlZz4pI-rMjfQ

   The final PASSporT token is produced by concatenating the values in
   the order Header.Payload.Signature with period (',') characters.  For
   the above example values this would produce the following:







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       eyJ0eXAiOiJwYXNzcG9ydCIsImFsZyI6IkVTMjU2IiwieDV1IjoiaHR0cHM6Ly9j
       ZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNydCJ9
       .
       eyJpYXQiOiIxNDQzMjA4MzQ1Iiwib3RuIjoiMTIxNTU1NTEyMTIiLCJkdXJpIjoi
       c2lwOmFsaWNlQGV4YW1wbGUuY29tIn0
       .
       KK89q2RFY-BkKQQhiB0z6-fIaFUy6NDyUboKXOix9XnYLxTCjdw1UHjCbw4CefeK
       wH_t7W-bnGlZz4pI-rMjfQ

A.1.  X.509 Private Key Certificate for Example in Appendix A

       -----BEGIN EC PRIVATE KEY-----
       MHcCAQEEIFeZ1R208QCvcu5GuYyMfG4W7sH4m99/7eHSDLpdYllFoAoGCCqGSM49
       AwEHoUQDQgAE8HNbQd/TmvCKwPKHkMF9fScavGeH78YTU8qLS8I5HLHSSmlATLcs
       lQMhNC/OhlWBYC626nIlo7XeebYS7Sb37g==
       -----END EC PRIVATE KEY-----

A.2.  X.509 Public Key Certificate for Example in Appendix A

       -----BEGIN PUBLIC KEY-----
       MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE8HNbQd/TmvCKwPKHkMF9fScavGeH
       78YTU8qLS8I5HLHSSmlATLcslQMhNC/OhlWBYC626nIlo7XeebYS7Sb37g==
       -----END PUBLIC KEY-----

Appendix B.  Example RS256 base PASSporT JWS Serialization and Signature

   For PASSporT, there will always be a JWS with the following members:

   o  "protected", with the value BASE64URL(UTF8(JWS Protected Header))

   o  "payload", with the value BASE64URL (JWS Payload)

   o  "signature", with the value BASE64URL(JWS Signature)

   Note: there will never be a JWS Unprotected Header for PASSporT.

   First, an example PASSporT Protected Header is as follows:

       {
           "typ":"passport",
           "alg":"RS256",
           "x5u":"https://cert.example.org/passport.crt"
       }

   This would be serialized to the form:

       {"typ":"passport","alg":"RS256","x5u":"https://cert.example.org/
       passport.crt"}



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   Encoding this with UTF8 and BASE64 encoding produces this value:

       eyJ0eXAiOiJwYXNzcG9ydCIsImFsZyI6IlJTMjU2IiwieDV1IjoiaHR0cHM
       6Ly9jZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNydCJ9

   Second, an example PASSporT Payload is as follows:

       {
           "iat":"1443208345",
           "otn":"12155551212",
           "duri":"sip:alice@example.com"
       }

   This would be serialized to the form:

       {"iat":"1443208345","otn":"12155551212","duri":
       "sip:alice@example.com"}

   Encoding this with the UTF8 and BASE64 encoding produces this value:

       eyJpYXQiOiIxNDQzMjA4MzQ1Iiwib3RuIjoiMTIxNTU1NTEyMTIiLCJkdXJp
       Ijoic2lwOmFsaWNlQGV4YW1wbGUuY29tIn0

   Computing the digital signature of the PASSporT Signing Input
   ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS
   Payload))

       AaeXRqm7kHnkZu2j6cQmDCiomZRiaE55bYWhFgnX8xMqpBFq96M0xgMM5OLa9
       _LMrkuKv2ivK5GZz8OlFrmAirucRlAh8YdUkj5Cr5xPRr-gg9acD9jqJUnQ-Z
       xpL1yq-FFVLhvpbsE5NMPHXUp5lpt62rD-S0NlhwHNCeMqZHxt6T5BmZBXITE
       d1PRRij_6FhE3wxWEhZMthWJuEbcPpRMZDu-R7lTNddn62nUKjn3s00R3gm25
       Dto5Z0dzfQpAysJvnbc1QRimfsYqJPUFc57lnglVLf4WrpeZCc8-LcoXeSr_d
       seDgsrmg2EuHmn5h1nTOmLgF16ZHm121ZVjiXz2sMFvs9RaIxw0AFkM7rnV56
       OxAFCRuzMNldiEVf8plRZVvqZ4BfVQlCNXNyyVgPOUtNr3ta6yD2H0oANQvvH
       twjuSwB9Kruj4Wsu5N7Iki4MBs6SWJDmcUV-NW_AHYLaao-IvFVe4oCkJNjsq
       wwXuLv1TO2sDHdc5sQO5zm21019PPxw1udHVtywsRVNKLo0RzE0TqYUF7XclC
       Dur7MMOx9SnStV2PFIM7Jejyn9x54RtJEjOnchaSalfIFr_UXqXgVmRZVTzLD
       QIlcmHjlhhLnCnNx3sYsAANen8Y8jtfgJ2ewjGotB4Lq8VYe1FacBKKk0VyCf
       ImXba0u1hB8Q

   The final PASSporT token is produced by concatenating the values in
   the order Header.Payload.Signature with period (',') characters.  For
   the above example values this would produce the following:








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       eyJ0eXAiOiJwYXNzcG9ydCIsImFsZyI6IlJTMjU2IiwieDV1IjoiaHR0cHM6L
       y9jZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNydCJ9
       .
       eyJpYXQiOiIxNDQzMjA4MzQ1Iiwib3RuIjoiMTIxNTU1NTEyMTIiLCJkdXJpI
       joic2lwOmFsaWNlQGV4YW1wbGUuY29tIn0
       .
       AaeXRqm7kHnkZu2j6cQmDCiomZRiaE55bYWhFgnX8xMqpBFq96M0xgMM5OLa9
       _LMrkuKv2ivK5GZz8OlFrmAirucRlAh8YdUkj5Cr5xPRr-gg9acD9jqJUnQ-Z
       xpL1yq-FFVLhvpbsE5NMPHXUp5lpt62rD-S0NlhwHNCeMqZHxt6T5BmZBXITE
       d1PRRij_6FhE3wxWEhZMthWJuEbcPpRMZDu-R7lTNddn62nUKjn3s00R3gm25
       Dto5Z0dzfQpAysJvnbc1QRimfsYqJPUFc57lnglVLf4WrpeZCc8-LcoXeSr_d
       seDgsrmg2EuHmn5h1nTOmLgF16ZHm121ZVjiXz2sMFvs9RaIxw0AFkM7rnV56
       OxAFCRuzMNldiEVf8plRZVvqZ4BfVQlCNXNyyVgPOUtNr3ta6yD2H0oANQvvH
       twjuSwB9Kruj4Wsu5N7Iki4MBs6SWJDmcUV-NW_AHYLaao-IvFVe4oCkJNjsq
       wwXuLv1TO2sDHdc5sQO5zm21019PPxw1udHVtywsRVNKLo0RzE0TqYUF7XclC
       Dur7MMOx9SnStV2PFIM7Jejyn9x54RtJEjOnchaSalfIFr_UXqXgVmRZVTzLD
       QIlcmHjlhhLnCnNx3sYsAANen8Y8jtfgJ2ewjGotB4Lq8VYe1FacBKKk0VyCf
       ImXba0u1hB8Q

B.1.  X.509 Private Key Certificate for Example in Appendix A

       -----BEGIN RSA PRIVATE KEY-----
       MIIJKQIBAAKCAgEAsrKb3NsMgrXTzEcNlg3vaBbI12mG3D9QBn61H8PpsVFIh3MA
       XNXjkV64he/eEQou3STTEgSqUXj5kj+jnnVFF0Cd0T6j7SuRvpq5YaiKfXgdUlsv
       F3LjTRGyoKRNOf16f/zEFiyJBX10vj/LKvnWos1vVTSqBeui2dNLynr0+f1n8b0+
       0FZwACceo3qaVwuSNIJWSQgM1qAINBpPEKnrIpdt5fa7mUorJ5gjITys3gjNJ4ee
       sjqUEu5ZGXDgMshVtH2iMceC1393sK6rJ7z+g3jVziSo6vy9lA2wveKMuoqQTwp0
       V0IrkzExU7vpTzyx0E3mJNmlgmDp7Whp2HCvKjeG+iPfsuPMDRggUrdy9qG6QTFq
       QORzLywTpu78ExYMSfqt94NVhf2Dv+QEPoytT1avN6bwGu/R/84g2z0YMfum5roS
       TG5PGP4H56vjML8wNTd6v8Ny8SLAgzG/XBaV7c8Ll2awLEj4FSeBpNzTyDgnLrth
       7Tk0LmM8EtO1aozDDEaMFrNy4/L+Uuwxp/wcFADawE9N7VdHa9endEo9V/bu1tkq
       ecv1Ma+G4NvJZzD8JTBRVsHNc3zvI0qD0KWCjqPvaIMiiVATVAIW9ZEtUZNm5UVu
       DzhcY7QrXNRpGE6ULIXgim66mbfUQ0LFq4G+zUjoRZTA92rFBn4vDKvsPs8CAwEA
       AQKCAgEAk3Sc9sbucOGXbuZmyJ6hIhRDELXsacv4vhNKZHbmXMJFBjgYYYLBsRAn
       VaZUaV0sxKEBZsngvTAFSPAolLYSGBji4Wo+HJQqRM0qEfLgrJ40G+RQXJoaBFuJ
       OdO6QhLvRbOPHvkK7DPU5LSBcuoMefTpXLcDYbVKgVJBJUkG405+ulS+A26AJzAg
       sSeXOiK7N4chqkvxRB10B4J6IbcE51trfSp3LQutxpNc0a1evC0pFOhtRIbf7yss
       7Lhe2KjFSBWvhEIsrqRpYKsRYs4qetR4IQ3RMW7zBLuzT00lcTyrzf1DeUmJ6YDb
       Qkw6Pn9H/yp4sYnDcG2GOrhBNy/s6ZecANLDbKg6MqwszDqLZnIOh7zPV1MPGEjc
       LkfLue1CA7FaipDUAlSYDfkaNHEcGFxHEgTuv3zmcuMijgNzCtA71M/6kG41DZa1
       8PZmqcw8CmMo+1UD3QwL5hHvMbeCyq1UZQvrTmwSLaGjC/goTjChzrsq5NBQcNNb
       eiGUFXciqJlh10NfxT8arefoQ/EDuARiZNvwGDqrGkvZk3/xokGeQi6nf1DL4NtU
       wQJyzVDJERFs9SohwkJWlPACFxISbxBztyw3nUvGN2iUQdnglGXmwmo7Ork0uook
       R2TV1OS7INVOTiEx8AApdiFXWZ752pB96ww6s5pDP3Isp0yxddECggEBAOuSVK2/
       7v9aCzlf+IZiklTkpG9CRkBqEsIj6p9ADBMWahqxlzjKwzGJH55v0U/etqOOZYVV
       HFzHIzlfZN1Yy1LXYKKcrwU23rLLiG5IsYFCcX2t1Cw6ZxHEsuMsOi8X8IbhSjJe
       xTGmwYiJqdKlSyznFopPtZ0leVqMjHTAMCk36AzRwTMnjOIhA1p1Ru0HPFK1RF/5
       /EuAUPws2ur1CDjsJwOQa2gRpInbxzZMCE/J+OqgWz4DMivLMCYT40zSjvY7+sqW



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       K77khwSm9/wMhuvVDedXHaNcrrQQbrk89oYt0Lx74RjUGc/nF79loQDOTZ/Hc7Fq
       1Nj2cuw0rIdJoUkCggEBAMIxrp4jSjdNT62WpnTfejJUdLVvn+3zvuNWcwIpUrIl
       ILBINlVofMMKLIi0VuqFc7tJiim+dUufp+taoj4E2rPumxZGMb7m9/XGFIyDY+2j
       qJEin6kK8WMT5he94C5uQg3faSzMi+sbEa4HSXMhBOP6iLqSQyUZpq1ecRjOdnDk
       bWCAHoRRYKSaPMJRdQjHD5++hItLCo2MiwVFBl2nRVh3vHIYARY3K84BMnvbUayd
       nfZB/tGOuvTksMRHcqoDFgXNj5/ymqBzoSpQzCMfH79Sv1uQPkDqKO/YbBT3HVDv
       6nKX44Vv4iy9Xwqsv3nTtuq2gpFJU30tfHBVltYB91cCggEAUaJhE+EaeoUCtLxM
       TI2mNiMR1Lh7zeC0ZXC64rr4NDklReDbDcQ+RlFFkssfFvWQBzfWeJEZBhHAZCZp
       tscJlsiqZU+02zK7k+wyeD1avfd/itUNXNJUW3T1pQHzm9RI9wTliHUNEvq9wIos
       PqInXgUq631Z635MApQILIFZbz8/fAnIUOjYypg0KEnR7Vv/jI3ihvwDcUqjRfBp
       YNjPI6K6lmKaxfKvOVLfQzKwAq50QyKU2/WRklmUcu2bbEjfX/dDHqdRu5JIM9WE
       xGS28MzhR5UJ4U3CAQZcyHaW28LOvjKTu93sn/5uXVZjp/rWLZOZxRbHcfRduPs7
       +poKeQKCAQBc8nqppip3ncFtTJYPiodqX5Ic5Xie4/ORzGbvueei7LJgra+T4ZcV
       o2D9bZPMXGOwWNqQcGCj+Z7dv1u4Y4pqZOJGHwLgZJx6PnzHZHwH2jVsgi35Mwum
       aHfRFUif8JYdHbmxf5XYyfQEX+h/+mXk2J1o72jD8Ssd//4R6YA3OJ5BehEhM/IV
       1t0OBP8HXH/V7dJy+U/rwEEqHIeXe+BtH6JK2cJrZ6zHxTrsnWTSQf7BR4U3uCEz
       5eHVkH0JcsCvtlvwKqZn9fBF2LZceSEw6eI9aSTi3TEK24Of5Uda3fpRLvHvhEW1
       NE6xRU3Aed0rKoAEGhyj5YmSGuU/OWGxAoIBAQDbREen8GWGLFmj0iQFs0I2Jr1k
       1iazomLyR9Vvhe8sUu57mE0lKbFo6vt8RPm69NSJ7nMCrSbCwG+qERMdMLK8OuiY
       v+W3wvvKcpXCShJ1GpgqKmBdP4VnHKvgHQ/kzdtLDmJI4SkTim1Mi94szSMPIfQw
       cMdZAGivDPjdXw95xENLClPOkhjX9t/qZjkZclQyjYCYGJHRxX6J7PdcKRY0/9VV
       jgRwxooE2POv11/qSk1O3lhFvjjm5oxr7CKPcHvESk/r8mh+VWO4DaOD4gQ9ke00
       2QGhocy3K578uL4ph7nfTR2QD96mxCNX9b2Pj9HG8Qb3wEvtaGBfUu8do2mT
       -----END RSA PRIVATE KEY-----

B.2.  X.509 Public Key Certificate for Example in Appendix A

       -----BEGIN PUBLIC KEY-----
       MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAsrKb3NsMgrXTzEcNlg3v
       aBbI12mG3D9QBn61H8PpsVFIh3MAXNXjkV64he/eEQou3STTEgSqUXj5kj+jnnVF
       F0Cd0T6j7SuRvpq5YaiKfXgdUlsvF3LjTRGyoKRNOf16f/zEFiyJBX10vj/LKvnW
       os1vVTSqBeui2dNLynr0+f1n8b0+0FZwACceo3qaVwuSNIJWSQgM1qAINBpPEKnr
       Ipdt5fa7mUorJ5gjITys3gjNJ4eesjqUEu5ZGXDgMshVtH2iMceC1393sK6rJ7z+
       g3jVziSo6vy9lA2wveKMuoqQTwp0V0IrkzExU7vpTzyx0E3mJNmlgmDp7Whp2HCv
       KjeG+iPfsuPMDRggUrdy9qG6QTFqQORzLywTpu78ExYMSfqt94NVhf2Dv+QEPoyt
       T1avN6bwGu/R/84g2z0YMfum5roSTG5PGP4H56vjML8wNTd6v8Ny8SLAgzG/XBaV
       7c8Ll2awLEj4FSeBpNzTyDgnLrth7Tk0LmM8EtO1aozDDEaMFrNy4/L+Uuwxp/wc
       FADawE9N7VdHa9endEo9V/bu1tkqecv1Ma+G4NvJZzD8JTBRVsHNc3zvI0qD0KWC
       jqPvaIMiiVATVAIW9ZEtUZNm5UVuDzhcY7QrXNRpGE6ULIXgim66mbfUQ0LFq4G+
       zUjoRZTA92rFBn4vDKvsPs8CAwEAAQ==
       -----END PUBLIC KEY-----

Authors' Addresses








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   Chris Wendt
   Comcast
   One Comcast Center
   Philadelphia, PA  19103
   USA

   Email: chris-ietf@chriswendt.net


   Jon Peterson
   Neustar Inc.
   1800 Sutter St Suite 570
   Concord, CA  94520
   US

   Email: jon.peterson@neustar.biz



































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