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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                              J. Bradley
Expires: January 30, 2014                                  Ping Identity
                                                             N. Sakimura
                                                                     NRI
                                                           July 29, 2013


                        JSON Web Signature (JWS)
                 draft-ietf-jose-json-web-signature-14

Abstract

   JSON Web Signature (JWS) is a means of representing content secured
   with digital signatures or Message Authentication Codes (MACs) using
   JavaScript Object Notation (JSON) based data structures.
   Cryptographic algorithms and identifiers for use with this
   specification are described in the separate JSON Web Algorithms (JWA)
   specification.  Related encryption capabilities are described in the
   separate JSON Web Encryption (JWE) specification.

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 January 30, 2014.

Copyright Notice

   Copyright (c) 2013 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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  JSON Web Signature (JWS) Overview  . . . . . . . . . . . . . .  6
     3.1.  Example JWS  . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  JWS Header . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Reserved Header Parameter Names  . . . . . . . . . . . . .  8
       4.1.1.  "alg" (Algorithm) Header Parameter . . . . . . . . . .  8
       4.1.2.  "jku" (JWK Set URL) Header Parameter . . . . . . . . .  9
       4.1.3.  "jwk" (JSON Web Key) Header Parameter  . . . . . . . .  9
       4.1.4.  "x5u" (X.509 URL) Header Parameter . . . . . . . . . .  9
       4.1.5.  "x5t" (X.509 Certificate Thumbprint) Header
               Parameter  . . . . . . . . . . . . . . . . . . . . . . 10
       4.1.6.  "x5c" (X.509 Certificate Chain) Header Parameter . . . 10
       4.1.7.  "kid" (Key ID) Header Parameter  . . . . . . . . . . . 10
       4.1.8.  "typ" (Type) Header Parameter  . . . . . . . . . . . . 11
       4.1.9.  "cty" (Content Type) Header Parameter  . . . . . . . . 11
       4.1.10. "crit" (Critical) Header Parameter . . . . . . . . . . 11
     4.2.  Public Header Parameter Names  . . . . . . . . . . . . . . 12
     4.3.  Private Header Parameter Names . . . . . . . . . . . . . . 12
   5.  Producing and Consuming JWSs . . . . . . . . . . . . . . . . . 12
     5.1.  Message Signing or MACing  . . . . . . . . . . . . . . . . 12
     5.2.  Message Signature or MAC Validation  . . . . . . . . . . . 13
     5.3.  String Comparison Rules  . . . . . . . . . . . . . . . . . 15
   6.  Key Identification . . . . . . . . . . . . . . . . . . . . . . 15
   7.  Serializations . . . . . . . . . . . . . . . . . . . . . . . . 16
     7.1.  JWS Compact Serialization  . . . . . . . . . . . . . . . . 16
     7.2.  JWS JSON Serialization . . . . . . . . . . . . . . . . . . 16
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
     8.1.  JSON Web Signature and Encryption Header Parameters
           Registry . . . . . . . . . . . . . . . . . . . . . . . . . 18
       8.1.1.  Registration Template  . . . . . . . . . . . . . . . . 19
       8.1.2.  Initial Registry Contents  . . . . . . . . . . . . . . 19
     8.2.  JSON Web Signature and Encryption Type Values Registry . . 20
       8.2.1.  Registration Template  . . . . . . . . . . . . . . . . 20
       8.2.2.  Initial Registry Contents  . . . . . . . . . . . . . . 21
     8.3.  Media Type Registration  . . . . . . . . . . . . . . . . . 21
       8.3.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 21
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22



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     9.1.  Cryptographic Security Considerations  . . . . . . . . . . 23
     9.2.  JSON Security Considerations . . . . . . . . . . . . . . . 24
     9.3.  Unicode Comparison Security Considerations . . . . . . . . 24
     9.4.  TLS Requirements . . . . . . . . . . . . . . . . . . . . . 25
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 25
     10.2. Informative References . . . . . . . . . . . . . . . . . . 27
   Appendix A.  JWS Examples  . . . . . . . . . . . . . . . . . . . . 27
     A.1.  Example JWS using HMAC SHA-256 . . . . . . . . . . . . . . 28
       A.1.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 28
       A.1.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 30
       A.1.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 30
     A.2.  Example JWS using RSASSA-PKCS-v1_5 SHA-256 . . . . . . . . 30
       A.2.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 30
       A.2.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 33
       A.2.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 33
     A.3.  Example JWS using ECDSA P-256 SHA-256  . . . . . . . . . . 33
       A.3.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 33
       A.3.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 35
       A.3.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 36
     A.4.  Example JWS using ECDSA P-521 SHA-512  . . . . . . . . . . 36
       A.4.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 36
       A.4.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 38
       A.4.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 38
     A.5.  Example Plaintext JWS  . . . . . . . . . . . . . . . . . . 39
     A.6.  Example JWS Using JWS JSON Serialization . . . . . . . . . 40
       A.6.1.  JWS Per-Signature Protected Headers  . . . . . . . . . 40
       A.6.2.  JWS Per-Signature Unprotected Headers  . . . . . . . . 40
       A.6.3.  Complete JWS Header Values . . . . . . . . . . . . . . 41
       A.6.4.  Complete JWS JSON Serialization Representation . . . . 41
   Appendix B.  "x5c" (X.509 Certificate Chain) Example . . . . . . . 41
   Appendix C.  Notes on implementing base64url encoding without
                padding . . . . . . . . . . . . . . . . . . . . . . . 43
   Appendix D.  Negative Test Case for "crit" Header Parameter  . . . 44
   Appendix E.  Acknowledgements  . . . . . . . . . . . . . . . . . . 45
   Appendix F.  Document History  . . . . . . . . . . . . . . . . . . 45
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 51














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1.  Introduction

   JSON Web Signature (JWS) is a means of representing content secured
   with digital signatures or Message Authentication Codes (MACs) using
   JavaScript Object Notation (JSON) [RFC4627] based data structures.
   The JWS cryptographic mechanisms provide integrity protection for
   arbitrary sequences of octets.

   Two closely related representations for JWS objects are defined.  The
   JWS Compact Serialization is a compact, URL-safe representation
   intended for space constrained environments such as HTTP
   Authorization headers and URI query parameters.  The JWS JSON
   Serialization represents JWS objects as JSON objects and enables
   multiple signatures and/or MACs to be applied to the same content.
   Both share the same cryptographic underpinnings.

   Cryptographic algorithms and identifiers for use with this
   specification are described in the separate JSON Web Algorithms (JWA)
   [JWA] specification.  Related encryption capabilities are described
   in the separate JSON Web Encryption (JWE) [JWE] specification.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in Key words for use in
   RFCs to Indicate Requirement Levels [RFC2119].


2.  Terminology

   JSON Web Signature (JWS)  A data structure representing a digitally
      signed or MACed message.  The structure represents three values:
      the JWS Header, the JWS Payload, and the JWS Signature.

   JSON Text Object  A UTF-8 [RFC3629] encoded text string representing
      a JSON object; the syntax of JSON objects is defined in Section
      2.2 of [RFC4627].

   JWS Header  A JSON Text Object (or JSON Text Objects, when using the
      JWS JSON Serialization) that describes the digital signature or
      MAC operation applied to create the JWS Signature value.  The
      members of the JWS Header object(s) are Header Parameters.

   JWS Payload  The sequence of octets to be secured -- a.k.a., the
      message.  The payload can contain an arbitrary sequence of octets.





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   JWS Signature  A sequence of octets containing the cryptographic
      material that ensures the integrity of the JWS Protected Header
      and the JWS Payload.  The JWS Signature value is a digital
      signature or MAC value calculated over the JWS Signing Input using
      the parameters specified in the JWS Header.

   JWS Protected Header  A JSON Text Object that contains the portion of
      the JWS Header that is integrity protected.  For the JWS Compact
      Serialization, this comprises the entire JWS Header.  For the JWS
      JSON Serialization, this is one component of the JWS Header.

   Header Parameter  A name/value pair that is member of the JWS Header.

   Header Parameter Name  The name of a member of the JWS Header.

   Header Parameter Value  The value of a member of the JWS Header.

   Base64url Encoding  The URL- and filename-safe Base64 encoding
      described in RFC 4648 [RFC4648], Section 5, with the (non URL-
      safe) '=' padding characters omitted, as permitted by Section 3.2.
      (See Appendix C for notes on implementing base64url encoding
      without padding.)

   Encoded JWS Header  Base64url encoding of the JWS Protected Header.

   Encoded JWS Payload  Base64url encoding of the JWS Payload.

   Encoded JWS Signature  Base64url encoding of the JWS Signature.

   JWS Signing Input  The concatenation of the Encoded JWS Header, a
      period ('.') character, and the Encoded JWS Payload.

   JWS Compact Serialization  A representation of the JWS as the
      concatenation of the Encoded JWS Header, the Encoded JWS Payload,
      and the Encoded JWS Signature in that order, with the three
      strings being separated by two period ('.') characters.  This
      representation is compact and URL-safe.

   JWS JSON Serialization  A representation of the JWS as a JSON
      structure containing JWS Header, Encoded JWS Payload, and Encoded
      JWS Signature values.  Unlike the JWS Compact Serialization, the
      JWS JSON Serialization enables multiple digital signatures and/or
      MACs to be applied to the same content.  This representation is
      neither compact nor URL-safe.







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   Collision Resistant Namespace  A namespace that allows names to be
      allocated in a manner such that they are highly unlikely to
      collide with other names.  For instance, collision resistance can
      be achieved through administrative delegation of portions of the
      namespace or through use of collision-resistant name allocation
      functions.  Examples of Collision Resistant Namespaces include:
      Domain Names, Object Identifiers (OIDs) as defined in the ITU-T
      X.660 and X.670 Recommendation series, and Universally Unique
      IDentifiers (UUIDs) [RFC4122].  When using an administratively
      delegated namespace, the definer of a name needs to take
      reasonable precautions to ensure they are in control of the
      portion of the namespace they use to define the name.

   StringOrURI  A JSON string value, with the additional requirement
      that while arbitrary string values MAY be used, any value
      containing a ":" character MUST be a URI [RFC3986].  StringOrURI
      values are compared as case-sensitive strings with no
      transformations or canonicalizations applied.


3.  JSON Web Signature (JWS) Overview

   JWS represents digitally signed or MACed content using JSON data
   structures and base64url encoding.  Three values are represented in a
   JWS: the JWS Header, the JWS Payload, and the JWS Signature.  In the
   Compact Serialization, the three values are base64url-encoded for
   transmission, and represented as the concatenation of the encoded
   strings in that order, with the three strings being separated by two
   period ('.') characters.  A JSON Serialization for this information
   is also defined in Section 7.2.

   The JWS Header describes the signature or MAC method and parameters
   employed.  The JWS Payload is the message content to be secured.  The
   JWS Signature ensures the integrity of both the JWS Protected Header
   and the JWS Payload.

3.1.  Example JWS

   The following example JWS Header declares that the encoded object is
   a JSON Web Token (JWT) [JWT] and the JWS Header and the JWS Payload
   are secured using the HMAC SHA-256 algorithm:

     {"typ":"JWT",
      "alg":"HS256"}

   Base64url encoding the octets of the UTF-8 representation of the JWS
   Header yields this Encoded JWS Header value:




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     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

   The following is an example of a JSON object that can be used as a
   JWS Payload.  (Note that the payload can be any content, and need not
   be a representation of a JSON object.)

     {"iss":"joe",
      "exp":1300819380,
      "http://example.com/is_root":true}

   The following octet sequence, which is the UTF-8 representation of
   the JSON object above, is the JWS Payload:

   [123, 34, 105, 115, 115, 34, 58, 34, 106, 111, 101, 34, 44, 13, 10,
   32, 34, 101, 120, 112, 34, 58, 49, 51, 48, 48, 56, 49, 57, 51, 56,
   48, 44, 13, 10, 32, 34, 104, 116, 116, 112, 58, 47, 47, 101, 120, 97,
   109, 112, 108, 101, 46, 99, 111, 109, 47, 105, 115, 95, 114, 111,
   111, 116, 34, 58, 116, 114, 117, 101, 125]

   Base64url encoding the JWS Payload yields this Encoded JWS Payload
   (with line breaks for display purposes only):

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   Computing the HMAC of the octets of the ASCII [USASCII]
   representation of the JWS Signing Input (the concatenation of the
   Encoded JWS Header, a period ('.') character, and the Encoded JWS
   Payload) with the HMAC SHA-256 algorithm using the key specified in
   Appendix A.1 and base64url encoding the result yields this Encoded
   JWS Signature value:

     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

   Concatenating these values in the order Header.Payload.Signature with
   period ('.') characters between the parts yields this complete JWS
   representation using the JWS Compact Serialization (with line breaks
   for display purposes only):

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .
     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

   This computation is illustrated in more detail in Appendix A.1.  See
   Appendix A for additional examples.



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4.  JWS Header

   The members of the JSON object(s) representing the JWS Header
   describe the digital signature or MAC applied to the Encoded JWS
   Header and the Encoded JWS Payload and optionally additional
   properties of the JWS.  The Header Parameter Names within the JWS
   Header MUST be unique; recipients MUST either reject JWSs with
   duplicate Header Parameter Names or use a JSON parser that returns
   only the lexically last duplicate member name, as specified in
   Section 15.12 (The JSON Object) of ECMAScript 5.1 [ECMAScript].

   Implementations are required to understand the specific header
   parameters defined by this specification that are designated as "MUST
   be understood" and process them in the manner defined in this
   specification.  All other header parameters defined by this
   specification that are not so designated MUST be ignored when not
   understood.  Unless listed as a critical header parameter, per
   Section 4.1.10, all header parameters not defined by this
   specification MUST be ignored when not understood.

   There are three classes of Header Parameter Names: Reserved Header
   Parameter Names, Public Header Parameter Names, and Private Header
   Parameter Names.

4.1.  Reserved Header Parameter Names

   The following Header Parameter Names are reserved with meanings as
   defined below.  All the names are short because a core goal of this
   specification is for the resulting representations using the JWS
   Compact Serialization to be compact.

   Additional reserved Header Parameter Names can be defined via the
   IANA JSON Web Signature and Encryption Header Parameters registry
   Section 8.1.  As indicated by the common registry, JWSs and JWEs
   share a common header parameter space; when a parameter is used by
   both specifications, its usage must be compatible between the
   specifications.

4.1.1.  "alg" (Algorithm) Header Parameter

   The "alg" (algorithm) header parameter identifies a cryptographic
   algorithm used to secure the JWS.  The recipient MUST reject the JWS
   if the "alg" value does not represent a supported algorithm, or if
   there is not a key for use with that algorithm associated with the
   party that digitally signed or MACed the content. "alg" values SHOULD
   either be registered in the IANA JSON Web Signature and Encryption
   Algorithms registry [JWA] or be a value that contains a Collision
   Resistant Namespace.  The "alg" value is a case sensitive string



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   containing a StringOrURI value.  Use of this header parameter is
   REQUIRED.  This header parameter MUST be understood by
   implementations.

   A list of defined "alg" values can be found in the IANA JSON Web
   Signature and Encryption Algorithms registry [JWA]; the initial
   contents of this registry are the values defined in Section 3.1 of
   the JSON Web Algorithms (JWA) [JWA] specification.

4.1.2.  "jku" (JWK Set URL) Header Parameter

   The "jku" (JWK Set URL) header parameter is a URI [RFC3986] that
   refers to a resource for a set of JSON-encoded public keys, one of
   which corresponds to the key used to digitally sign the JWS.  The
   keys MUST be encoded as a JSON Web Key Set (JWK Set) [JWK].  The
   protocol used to acquire the resource MUST provide integrity
   protection; an HTTP GET request to retrieve the JWK Set MUST use TLS
   [RFC2818] [RFC5246]; the identity of the server MUST be validated, as
   per Section 3.1 of HTTP Over TLS [RFC2818].  Use of this header
   parameter is OPTIONAL.

4.1.3.  "jwk" (JSON Web Key) Header Parameter

   The "jwk" (JSON Web Key) header parameter is the public key that
   corresponds to the key used to digitally sign the JWS.  This key is
   represented as a JSON Web Key [JWK].  Use of this header parameter is
   OPTIONAL.

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

   The "x5u" (X.509 URL) header parameter is a URI [RFC3986] that refers
   to a resource for the X.509 public key certificate or certificate
   chain [RFC5280] corresponding to the key used to digitally sign the
   JWS.  The identified resource MUST provide a representation of the
   certificate or certificate chain that conforms to RFC 5280 [RFC5280]
   in PEM encoded form [RFC1421].  The certificate containing the public
   key corresponding to the key used to digitally sign the JWS MUST be
   the first certificate.  This MAY be followed by additional
   certificates, with each subsequent certificate being the one used to
   certify the previous one.  The protocol used to acquire the resource
   MUST provide integrity protection; an HTTP GET request to retrieve
   the certificate MUST use TLS [RFC2818] [RFC5246]; the identity of the
   server MUST be validated, as per Section 3.1 of HTTP Over TLS
   [RFC2818].  Use of this header parameter is OPTIONAL.







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4.1.5.  "x5t" (X.509 Certificate Thumbprint) Header Parameter

   The "x5t" (X.509 Certificate Thumbprint) header parameter is a
   base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER
   encoding of the X.509 certificate [RFC5280] corresponding to the key
   used to digitally sign the JWS.  Use of this header parameter is
   OPTIONAL.

   If, in the future, certificate thumbprints need to be computed using
   hash functions other than SHA-1, it is suggested that additional
   related header parameters be defined for that purpose.  For example,
   it is suggested that a new "x5t#S256" (X.509 Certificate Thumbprint
   using SHA-256) header parameter could be defined by registering it in
   the IANA JSON Web Signature and Encryption Header Parameters registry
   Section 8.1.

4.1.6.  "x5c" (X.509 Certificate Chain) Header Parameter

   The "x5c" (X.509 Certificate Chain) header parameter contains the
   X.509 public key certificate or certificate chain [RFC5280]
   corresponding to the key used to digitally sign the JWS.  The
   certificate or certificate chain is represented as a JSON array of
   certificate value strings.  Each string in the array is a base64
   encoded ([RFC4648] Section 4 -- not base64url encoded) DER
   [ITU.X690.1994] PKIX certificate value.  The certificate containing
   the public key corresponding to the key used to digitally sign the
   JWS MUST be the first certificate.  This MAY be followed by
   additional certificates, with each subsequent certificate being the
   one used to certify the previous one.  The recipient MUST verify the
   certificate chain according to [RFC5280] and reject the JWS if any
   validation failure occurs.  Use of this header parameter is OPTIONAL.

   See Appendix B for an example "x5c" value.

4.1.7.  "kid" (Key ID) Header Parameter

   The "kid" (key ID) header parameter is a hint indicating which key
   was used to secure the JWS.  This parameter allows originators to
   explicitly signal a change of key to recipients.  Should the
   recipient be unable to locate a key corresponding to the "kid" value,
   they SHOULD treat that condition as an error.  The interpretation of
   the "kid" value is unspecified.  Its value MUST be a string.  Use of
   this header parameter is OPTIONAL.

   When used with a JWK, the "kid" value can be used to match a JWK
   "kid" parameter value.





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4.1.8.  "typ" (Type) Header Parameter

   The "typ" (type) header parameter MAY be used to declare the type of
   this complete JWS object in an application-specific manner in
   contexts where this is useful to the application.  This parameter has
   no effect upon the JWS processing.  The type value "JOSE" MAY be used
   by applications to indicate that this object is a JWS or JWE using
   the JWS Compact Serialization or the JWE Compact Serialization.  The
   type value "JOSE+JSON" MAY be used by applications to indicate that
   this object is a JWS or JWE using the JWS JSON Serialization or the
   JWE JSON Serialization.  Other type values MAY be used, and if not
   understood, SHOULD be ignored.  The "typ" value is a case sensitive
   string.  Use of this header parameter is OPTIONAL.

   MIME Media Type [RFC2046] values MAY be used as "typ" values.

   "typ" values SHOULD either be registered in the IANA JSON Web
   Signature and Encryption Type Values registry Section 8.2 or be a
   value that contains a Collision Resistant Namespace.

4.1.9.  "cty" (Content Type) Header Parameter

   The "cty" (content type) header parameter MAY be used to declare the
   type of the secured content (the payload) in an application-specific
   manner in contexts where this is useful to the application.  This
   parameter has no effect upon the JWS processing.  Content type values
   that are not understood SHOULD be ignored.  The "cty" value is a case
   sensitive string.  Use of this header parameter is OPTIONAL.

   The values used for the "cty" header parameter come from the same
   value space as the "typ" header parameter, with the same rules
   applying.

4.1.10.  "crit" (Critical) Header Parameter

   The "crit" (critical) header parameter indicates that extensions to
   [[ this specification ]] are being used that MUST be understood and
   processed.  Its value is an array listing the header parameter names
   defined by those extensions that are used in the JWS Header.  If any
   of the listed extension header parameters are not understood and
   supported by the receiver, it MUST reject the JWS.  Senders MUST NOT
   include header parameter names defined by [[ this specification ]] or
   by [JWA] for use with JWS, duplicate names, or names that do not
   occur as header parameter names within the JWS Header in the "crit"
   list.  Senders MUST not use the empty list "[]" as the "crit" value.
   Recipients MAY reject the JWS if the critical list contains any
   header parameter names defined by [[ this specification ]] or by
   [JWA] for use with JWS, or any other constraints on its use are



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   violated.  This header parameter MUST be integrity protected, and
   therefore MUST occur only with the JWS Protected Header, when used.
   Use of this header parameter is OPTIONAL.  This header parameter MUST
   be understood by implementations.

   An example use, along with a hypothetical "exp" (expiration-time)
   field is:

     {"alg":"ES256",
      "crit":["exp"],
      "exp":1363284000
     }

4.2.  Public Header Parameter Names

   Additional Header Parameter Names can be defined by those using JWSs.
   However, in order to prevent collisions, any new Header Parameter
   Name SHOULD either be registered in the IANA JSON Web Signature and
   Encryption Header Parameters registry Section 8.1 or be a Public
   Name: a value that contains a Collision Resistant Namespace.  In each
   case, the definer of the name or value needs to take reasonable
   precautions to make sure they are in control of the part of the
   namespace they use to define the Header Parameter Name.

   New header parameters should be introduced sparingly, as they can
   result in non-interoperable JWSs.

4.3.  Private Header Parameter Names

   A producer and consumer of a JWS may agree to use Header Parameter
   Names that are Private Names: names that are not Reserved Names
   Section 4.1 or Public Names Section 4.2.  Unlike Public Names,
   Private Names are subject to collision and should be used with
   caution.


5.  Producing and Consuming JWSs

5.1.  Message Signing or MACing

   To create a JWS, one MUST perform these steps.  The order of the
   steps is not significant in cases where there are no dependencies
   between the inputs and outputs of the steps.

   1.  Create the content to be used as the JWS Payload.

   2.  Base64url encode the octets of the JWS Payload.  This encoding
       becomes the Encoded JWS Payload.



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   3.  Create a JWS Header containing the desired set of header
       parameters.  Note that white space is explicitly allowed in the
       representation and no canonicalization need be performed before
       encoding.

   4.  Base64url encode the octets of the UTF-8 representation of the
       JWS Protected Header to create the Encoded JWS Header.  If the
       JWS Protected Header is not present (which can only happen when
       using the JWS JSON Serialization and no "protected" member is
       present), let the Encoded JWS Header be the empty string.

   5.  Compute the JWS Signature in the manner defined for the
       particular algorithm being used over the JWS Signing Input (the
       concatenation of the Encoded JWS Header, a period ('.')
       character, and the Encoded JWS Payload).  The "alg" (algorithm)
       header parameter MUST be present in the JWS Header, with the
       algorithm value accurately representing the algorithm used to
       construct the JWS Signature.

   6.  Base64url encode the representation of the JWS Signature to
       create the Encoded JWS Signature.

   7.  The three encoded parts are result values used in both the JWS
       Compact Serialization and the JWS JSON Serialization
       representations.

   8.  If the JWS JSON Serialization is being used, repeat this process
       for each digital signature or MAC value being applied.

   9.  Create the desired serialized output.  The JWS Compact
       Serialization of this result is the concatenation of the Encoded
       JWS Header, the Encoded JWS Payload, and the Encoded JWS
       Signature in that order, with the three strings being separated
       by two period ('.') characters.  The JWS JSON Serialization is
       described in Section 7.2.

5.2.  Message Signature or MAC Validation

   When validating a JWS, the following steps MUST be taken.  The order
   of the steps is not significant in cases where there are no
   dependencies between the inputs and outputs of the steps.  If any of
   the listed steps fails, then the JWS MUST be rejected.

   1.   Parse the serialized input to determine the values of the JWS
        Header, the Encoded JWS Payload, and the Encoded JWS Signature.
        When using the JWS Compact Serialization, the Encoded JWS
        Header, the Encoded JWS Payload, and the Encoded JWS Signature
        are represented as text strings in that order, separated by two



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        period ('.') characters.  The JWS JSON Serialization is
        described in Section 7.2.

   2.   The Encoded JWS Header MUST be successfully base64url decoded
        following the restriction given in this specification that no
        padding characters have been used.

   3.   Let the JWS Protected Header value be the result of base64url
        decoding the Encoded JWS Header.

   4.   The resulting JWS Protected Header MUST be a completely valid
        JSON object conforming to RFC 4627 [RFC4627].

   5.   If using the JWS Compact Serialization, let the JWS Header be
        the JWS Protected Header; otherwise, when using the JWS JSON
        Serialization, let the JWS Header be the union of the members of
        the corresponding "protected" and "header" header parameter
        values, all of which must be completely valid JSON objects.

   6.   The resulting JWS Header MUST NOT contain duplicate Header
        Parameter Names.  When using the JWS JSON Serialization, this
        restriction includes that the same Header Parameter Name also
        MUST NOT occur in distinct JSON Text Object values that together
        comprise the JWS Header.

   7.   The resulting JWS Header MUST be validated to only include
        parameters and values whose syntax and semantics are both
        understood and supported or that are specified as being ignored
        when not understood.

   8.   The Encoded JWS Payload MUST be successfully base64url decoded
        following the restriction given in this specification that no
        padding characters have been used.

   9.   The Encoded JWS Signature MUST be successfully base64url decoded
        following the restriction given in this specification that no
        padding characters have been used.

   10.  The JWS Signature MUST be successfully validated against the JWS
        Signing Input (the concatenation of the Encoded JWS Header, a
        period ('.') character, and the Encoded JWS Payload) in the
        manner defined for the algorithm being used, which MUST be
        accurately represented by the value of the "alg" (algorithm)
        header parameter, which MUST be present.

   11.  If the JWS JSON Serialization is being used, repeat this process
        for each digital signature or MAC value contained in the
        representation.



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5.3.  String Comparison Rules

   Processing a JWS inevitably requires comparing known strings to
   values in JSON objects.  For example, in checking what the algorithm
   is, the Unicode string encoding "alg" will be checked against the
   member names in the JWS Header to see if there is a matching Header
   Parameter Name.  A similar process occurs when determining if the
   value of the "alg" header parameter represents a supported algorithm.

   Comparisons between JSON strings and other Unicode strings MUST be
   performed as specified below:

   1.  Remove any JSON escaping from the input JSON string and convert
       the string into a sequence of Unicode code points.

   2.  Likewise, convert the string to be compared against into a
       sequence of Unicode code points.

   3.  Unicode Normalization [USA15] MUST NOT be applied at any point to
       either the JSON string or to the string it is to be compared
       against.

   4.  Comparisons between the two strings MUST be performed as a
       Unicode code point to code point equality comparison.  (Note that
       values that originally used different Unicode encodings (UTF-8,
       UTF-16, etc.) may result in the same code point values.)

   Also, see the JSON security considerations in Section 9.2 and the
   Unicode security considerations in Section 9.3.


6.  Key Identification

   It is necessary for the recipient of a JWS to be able to determine
   the key that was employed for the digital signature or MAC operation.
   The key employed can be identified using the Header Parameter methods
   described in Section 4.1 or can be identified using methods that are
   outside the scope of this specification.  Specifically, the Header
   Parameters "jku", "jwk", "x5u", "x5t", "x5c", and "kid" can be used
   to identify the key used.  The sender SHOULD include sufficient
   information in the Header Parameters to identify the key used, unless
   the application uses another means or convention to determine the key
   used.  Recipients MUST reject the input when the algorithm used
   requires a key (which is true of all algorithms except for "none")
   and the key used cannot be determined.






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7.  Serializations

   JWS objects use one of two serializations, the JWS Compact
   Serialization or the JWS JSON Serialization.  The JWS Compact
   Serialization is mandatory to implement.  Implementation of the JWS
   JSON Serialization is OPTIONAL.

7.1.  JWS Compact Serialization

   The JWS Compact Serialization represents digitally signed or MACed
   content as a compact URL-safe string.  This string is the
   concatenation of the Encoded JWS Header, the Encoded JWS Payload, and
   the Encoded JWS Signature in that order, with the three strings being
   separated by two period ('.') characters.  Only one signature/MAC is
   supported by the JWS Compact Serialization.

7.2.  JWS JSON Serialization

   The JWS JSON Serialization represents digitally signed or MACed
   content as a JSON object.  Unlike the JWS Compact Serialization,
   content using the JWS JSON Serialization can be secured with more
   than one digital signature and/or MAC value.

   The representation is closely related to that used in the JWS Compact
   Serialization, with the following differences for the JWS JSON
   Serialization:

   o  Values in the JWS JSON Serialization are represented as members of
      a JSON object, rather than as base64url encoded strings separated
      by period ('.') characters.  (However binary values and values
      that are integrity protected are still base64url encoded.)

   o  The Encoded JWS Payload value is stored in the "payload" member.

   o  There can be multiple signature and/or MAC values, rather than
      just one.  A JSON array in the "signatures" member is used to hold
      values that are specific to a particular signature or MAC
      computation, with one array element per signature/MAC represented.
      These array elements are JSON objects.

   o  Each Encoded JWS Signature value, if non-empty, is stored in the
      "signature" member of a JSON object that is an element of the
      "signatures" array.

   o  Each Encoded JWS Header value, which is a base64url encoded set of
      header parameter values that are included in the signature/MAC
      computation, if non-empty, is stored in the "protected" member of
      the corresponding element of the "signatures" array.



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   o  Unlike the JWS Compact Serialization, in the JWS JSON
      Serialization there can also be header parameter values that are
      not included in the signature/MAC computation.  If present,
      unprotected header parameter values are represented as an
      unencoded JSON Text Object in the "header" member of the
      corresponding element of the "signatures" array.

   o  The header parameter values used when creating or validating
      individual signature or MAC values are the union of the two sets
      of header parameter values that may be present: (1) the integrity-
      protected per-signature/MAC values represented in the "protected"
      member of the signature/MAC's array element, and (2) the non-
      integrity-protected per-signature/MAC values in the "header"
      member of the signature/MAC's array element.  The union of these
      sets of header parameters comprises the JWS Header.  The header
      parameter names in the two locations MUST be disjoint.

   The syntax of a JWS using the JWS JSON Serialization is as follows:

     {
      "payload":"<payload contents>"
      "signatures":[
       {"protected":<integrity-protected header 1 contents>",
        "header":"<non-integrity-protected header 1 contents>",
        "signature":"<signature 1 contents>"},
       ...
       {"protected":<integrity-protected header N contents>",
        "header":"<non-integrity-protected header N contents>",
        "signature":"<signature N contents>"}],
     }

   Of these members, only the "payload", "signatures", and "signature"
   members MUST be present.  At least one of the "protected" and
   "header" members MUST be present for each signature/MAC computation
   so that an "alg" header parameter value is conveyed.

   The contents of the Encoded JWS Payload and Encoded JWS Signature
   values are exactly as defined in the rest of this specification.
   They are interpreted and validated in the same manner, with each
   corresponding Encoded JWS Signature and set of header parameter
   values being created and validated together.  The JWS Header values
   used are the union of the header parameters in the corresponding
   "protected" and "header" members, as described earlier.

   Each JWS Signature value is computed on the JWS Signing Input using
   the parameters of the corresponding JWS Header value in the same
   manner as for the JWS Compact Serialization.  This has the desirable
   property that each Encoded JWS Signature value in the "signatures"



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   array is identical to the value that would have been computed for the
   same parameter in the JWS Compact Serialization, provided that the
   Encoded JWS Header value for that signature/MAC computation (which
   represents the integrity-protected header parameter values) matches
   that used in the JWS Compact Serialization.

   See Appendix A.6 for an example of computing a JWS using the JWS JSON
   Serialization.


8.  IANA Considerations

   The following registration procedure is used for all the registries
   established by this specification.

   Values are registered with a Specification Required [RFC5226] after a
   two-week review period on the [TBD]@ietf.org mailing list, on the
   advice of one or more Designated Experts.  However, to allow for the
   allocation of values prior to publication, the Designated Expert(s)
   may approve registration once they are satisfied that such a
   specification will be published.

   Registration requests must be sent to the [TBD]@ietf.org mailing list
   for review and comment, with an appropriate subject (e.g., "Request
   for access token type: example"). [[ Note to RFC-EDITOR: The name of
   the mailing list should be determined in consultation with the IESG
   and IANA.  Suggested name: jose-reg-review. ]]

   Within the review period, the Designated Expert(s) 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.

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

8.1.  JSON Web Signature and Encryption Header Parameters Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption Header Parameters registry for reserved JWS and JWE Header
   Parameter Names.  The registry records the reserved Header Parameter
   Name and a reference to the specification that defines it.  The same
   Header Parameter Name MAY be registered multiple times, provided that
   the parameter usage is compatible between the specifications.
   Different registrations of the same Header Parameter Name will
   typically use different Header Parameter Usage Location(s) values.



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8.1.1.  Registration Template

   Header Parameter Name:
      The name requested (e.g., "example").  This name is case
      sensitive.  Names that match other registered names in a case
      insensitive manner SHOULD NOT be accepted.

   Header Parameter Usage Location(s):
      The header parameter usage locations, which should be one or more
      of the values "JWS" or "JWE".

   Change Controller:
      For Standards Track RFCs, state "IETF".  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(s) that specify the parameter,
      preferably including URI(s) that can be used to retrieve copies of
      the document(s).  An indication of the relevant sections may also
      be included but is not required.

8.1.2.  Initial Registry Contents

   This specification registers the Header Parameter Names defined in
   Section 4.1 in this registry.

   o  Header Parameter Name: "alg"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.1 of [[ this document ]]

   o  Header Parameter Name: "jku"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.2 of [[ this document ]]

   o  Header Parameter Name: "jwk"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification document(s): Section 4.1.3 of [[ this document ]]

   o  Header Parameter Name: "x5u"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.4 of [[ this document ]]





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   o  Header Parameter Name: "x5t"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.5 of [[ this document ]]

   o  Header Parameter Name: "x5c"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.6 of [[ this document ]]

   o  Header Parameter Name: "kid"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.7 of [[ this document ]]

   o  Header Parameter Name: "typ"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

   o  Header Parameter Name: "cty"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.9 of [[ this document ]]

   o  Header Parameter Name: "crit"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.10 of [[ this document ]]

8.2.  JSON Web Signature and Encryption Type Values Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption Type Values registry for values of the JWS and JWE "typ"
   (type) header parameter.  It is RECOMMENDED that all registered "typ"
   values also include a MIME Media Type [RFC2046] value that the
   registered value is a short name for.  The registry records the "typ"
   value, the MIME type value that it is an abbreviation for (if any),
   and a reference to the specification that defines it.

   MIME Media Type [RFC2046] values MUST NOT be directly registered as
   new "typ" values; rather, new "typ" values MAY be registered as short
   names for MIME types.

8.2.1.  Registration Template






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   "typ" Header Parameter Value:
      The name requested (e.g., "example").  This name is case
      sensitive.  Names that match other registered names in a case
      insensitive manner SHOULD NOT be accepted.

   Abbreviation for MIME Type:
      The MIME type that this name is an abbreviation for (e.g.,
      "application/example").

   Change Controller:
      For Standards Track RFCs, state "IETF".  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(s) that specify the parameter,
      preferably including URI(s) that can be used to retrieve copies of
      the document(s).  An indication of the relevant sections may also
      be included but is not required.

8.2.2.  Initial Registry Contents

   This specification registers the "JOSE" and "JOSE+JSON" type values
   in this registry:

   o  "typ" Header Parameter Value: "JOSE"
   o  Abbreviation for MIME type: application/jose
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

   o  "typ" Header Parameter Value: "JOSE+JSON"
   o  Abbreviation for MIME type: application/jose+json
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

8.3.  Media Type Registration

8.3.1.  Registry Contents

   This specification registers the "application/jose" Media Type
   [RFC2046] in the MIME Media Type registry [RFC4288], which can be
   used to indicate that the content is a JWS or JWE object using the
   JWS Compact Serialization or the JWE Compact Serialization and the
   "application/jose+json" Media Type in the MIME Media Type registry,
   which can be used to indicate that the content is a JWS or JWE object
   using the JWS JSON Serialization or the JWE JSON Serialization.





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   o  Type name: application
   o  Subtype name: jose
   o  Required parameters: n/a
   o  Optional parameters: n/a
   o  Encoding considerations: application/jose values are encoded as a
      series of base64url encoded values (some of which may be the empty
      string) separated by period ('.') characters.
   o  Security considerations: See the Security Considerations section
      of [[ this document ]]
   o  Interoperability considerations: n/a
   o  Published specification: [[ this document ]]
   o  Applications that use this media type: OpenID Connect, Mozilla
      Persona, Salesforce, Google, numerous others that use signed JWTs
   o  Additional information: Magic number(s): n/a, File extension(s):
      n/a, Macintosh file type code(s): n/a
   o  Person & email address to contact for further information: Michael
      B. Jones, mbj@microsoft.com
   o  Intended usage: COMMON
   o  Restrictions on usage: none
   o  Author: Michael B. Jones, mbj@microsoft.com
   o  Change Controller: IETF

   o  Type name: application
   o  Subtype name: jose+json
   o  Required parameters: n/a
   o  Optional parameters: n/a
   o  Encoding considerations: application/jose+json values are
      represented as a JSON Object; UTF-8 encoding SHOULD be employed
      for the JSON object.
   o  Security considerations: See the Security Considerations section
      of [[ this document ]]
   o  Interoperability considerations: n/a
   o  Published specification: [[ this document ]]
   o  Applications that use this media type: TBD
   o  Additional information: Magic number(s): n/a, File extension(s):
      n/a, Macintosh file type code(s): n/a
   o  Person & email address to contact for further information: Michael
      B. Jones, mbj@microsoft.com
   o  Intended usage: COMMON
   o  Restrictions on usage: none
   o  Author: Michael B. Jones, mbj@microsoft.com
   o  Change Controller: IETF


9.  Security Considerations






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9.1.  Cryptographic Security Considerations

   All of the security issues faced by any cryptographic application
   must be faced by a JWS/JWE/JWK agent.  Among these issues are
   protecting the user's private and symmetric keys, preventing various
   attacks, and helping the user avoid mistakes such as inadvertently
   encrypting a message for the wrong recipient.  The entire list of
   security considerations is beyond the scope of this document, but
   some significant concerns are listed here.

   All the security considerations in XML DSIG 2.0
   [W3C.CR-xmldsig-core2-20120124], also apply to this specification,
   other than those that are XML specific.  Likewise, many of the best
   practices documented in XML Signature Best Practices
   [W3C.WD-xmldsig-bestpractices-20110809] also apply to this
   specification, other than those that are XML specific.

   Keys are only as strong as the amount of entropy used to generate
   them.  A minimum of 128 bits of entropy should be used for all keys,
   and depending upon the application context, more may be required.  In
   particular, it may be difficult to generate sufficiently random
   values in some browsers and application environments.

   Creators of JWSs should not allow third parties to insert arbitrary
   content into the message without adding entropy not controlled by the
   third party.

   When utilizing TLS to retrieve information, the authority providing
   the resource MUST be authenticated and the information retrieved MUST
   be free from modification.

   When cryptographic algorithms are implemented in such a way that
   successful operations take a different amount of time than
   unsuccessful operations, attackers may be able to use the time
   difference to obtain information about the keys employed.  Therefore,
   such timing differences must be avoided.

   A SHA-1 hash is used when computing "x5t" (x.509 certificate
   thumbprint) values, for compatibility reasons.  Should an effective
   means of producing SHA-1 hash collisions be developed, and should an
   attacker wish to interfere with the use of a known certificate on a
   given system, this could be accomplished by creating another
   certificate whose SHA-1 hash value is the same and adding it to the
   certificate store used by the intended victim.  A prerequisite to
   this attack succeeding is the attacker having write access to the
   intended victim's certificate store.

   If, in the future, certificate thumbprints need to be computed using



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   hash functions other than SHA-1, it is suggested that additional
   related header parameters be defined for that purpose.  For example,
   it is suggested that a new "x5t#S256" (X.509 Certificate Thumbprint
   using SHA-256) header parameter could be defined and used.

9.2.  JSON Security Considerations

   Strict JSON validation is a security requirement.  If malformed JSON
   is received, then the intent of the sender is impossible to reliably
   discern.  Ambiguous and potentially exploitable situations could
   arise if the JSON parser used does not reject malformed JSON syntax.

   Section 2.2 of the JavaScript Object Notation (JSON) specification
   [RFC4627] states "The names within an object SHOULD be unique",
   whereas this specification states that "Header Parameter Names within
   this object MUST be unique; recipients MUST either reject JWSs with
   duplicate Header Parameter Names or use a JSON parser that returns
   only the lexically last duplicate member name, as specified in
   Section 15.12 (The JSON Object) of ECMAScript 5.1 [ECMAScript]".
   Thus, this specification requires that the Section 2.2 "SHOULD" be
   treated as a "MUST" by senders and that it be either treated as a
   "MUST" or in the manner specified in ECMAScript 5.1 by receivers.
   Ambiguous and potentially exploitable situations could arise if the
   JSON parser used does not enforce the uniqueness of member names or
   returns an unpredictable value for duplicate member names.

   Some JSON parsers might not reject input that contains extra
   significant characters after a valid input.  For instance, the input
   "{"tag":"value"}ABCD" contains a valid JSON object followed by the
   extra characters "ABCD".  Such input MUST be rejected in its
   entirety.

9.3.  Unicode Comparison Security Considerations

   Header Parameter Names and algorithm names are Unicode strings.  For
   security reasons, the representations of these names must be compared
   verbatim after performing any escape processing (as per RFC 4627
   [RFC4627], Section 2.5).  This means, for instance, that these JSON
   strings must compare as being equal ("sig", "\u0073ig"), whereas
   these must all compare as being not equal to the first set or to each
   other ("SIG", "Sig", "si\u0047").

   JSON strings can contain characters outside the Unicode Basic
   Multilingual Plane.  For instance, the G clef character (U+1D11E) may
   be represented in a JSON string as "\uD834\uDD1E".  Ideally, JWS
   implementations SHOULD ensure that characters outside the Basic
   Multilingual Plane are preserved and compared correctly;
   alternatively, if this is not possible due to these characters



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   exercising limitations present in the underlying JSON implementation,
   then input containing them MUST be rejected.

9.4.  TLS Requirements

   Implementations MUST support TLS.  Which version(s) ought to be
   implemented will vary over time, and depend on the widespread
   deployment and known security vulnerabilities at the time of
   implementation.  At the time of this writing, TLS version 1.2
   [RFC5246] is the most recent version, but has very limited actual
   deployment, and might not be readily available in implementation
   toolkits.  TLS version 1.0 [RFC2246] is the most widely deployed
   version, and will give the broadest interoperability.

   To protect against information disclosure and tampering,
   confidentiality protection MUST be applied using TLS with a
   ciphersuite that provides confidentiality and integrity protection.

   Whenever TLS is used, a TLS server certificate check MUST be
   performed, per RFC 6125 [RFC6125].


10.  References

10.1.  Normative References

   [ECMAScript]
              Ecma International, "ECMAScript Language Specification,
              5.1 Edition", ECMA 262, June 2011.

   [ITU.X690.1994]
              International Telecommunications Union, "Information
              Technology - ASN.1 encoding rules: Specification of Basic
              Encoding Rules (BER), Canonical Encoding Rules (CER) and
              Distinguished Encoding Rules (DER)", ITU-T Recommendation
              X.690, 1994.

   [JWA]      Jones, M., "JSON Web Algorithms (JWA)",
              draft-ietf-jose-json-web-algorithms (work in progress),
              July 2013.

   [JWK]      Jones, M., "JSON Web Key (JWK)",
              draft-ietf-jose-json-web-key (work in progress),
              July 2013.

   [RFC1421]  Linn, J., "Privacy Enhancement for Internet Electronic
              Mail: Part I: Message Encryption and Authentication
              Procedures", RFC 1421, February 1993.



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   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, January 1999.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
              Registration Procedures", RFC 4288, December 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [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, May 2008.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.

   [USA15]    Davis, M., Whistler, K., and M. Deurst, "Unicode
              Normalization Forms", Unicode Standard Annex 15, 09 2009.



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   [USASCII]  American National Standards Institute, "Coded Character
              Set -- 7-bit American Standard Code for Information
              Interchange", ANSI X3.4, 1986.

   [W3C.WD-xmldsig-bestpractices-20110809]
              Datta, P. and F. Hirsch, "XML Signature Best Practices",
              World Wide Web Consortium WD WD-xmldsig-bestpractices-
              20110809, August 2011, <http://www.w3.org/TR/2011/
              WD-xmldsig-bestpractices-20110809>.

10.2.  Informative References

   [CanvasApp]
              Facebook, "Canvas Applications", 2010.

   [JSS]      Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
              September 2010.

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", draft-ietf-jose-json-web-encryption
              (work in progress), July 2013.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", draft-ietf-oauth-json-web-token (work in
              progress), July 2013.

   [MagicSignatures]
              Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
              Signatures", January 2011.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.

   [W3C.CR-xmldsig-core2-20120124]
              Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P.,
              Hirsch, F., Cantor, S., and T. Roessler, "XML Signature
              Syntax and Processing Version 2.0", World Wide Web
              Consortium CR CR-xmldsig-core2-20120124, January 2012,
              <http://www.w3.org/TR/2012/CR-xmldsig-core2-20120124>.


Appendix A.  JWS Examples

   This section provides several examples of JWSs.  While the first
   three examples all represent JSON Web Tokens (JWTs) [JWT], the
   payload can be any octet sequence, as shown in Appendix A.4.




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A.1.  Example JWS using HMAC SHA-256

A.1.1.  Encoding

   The following example JWS Header declares that the data structure is
   a JSON Web Token (JWT) [JWT] and the JWS Signing Input is secured
   using the HMAC SHA-256 algorithm.

     {"typ":"JWT",
      "alg":"HS256"}

   The following octet sequence contains the UTF-8 representation of the
   JWS Header:

   [123, 34, 116, 121, 112, 34, 58, 34, 74, 87, 84, 34, 44, 13, 10, 32,
   34, 97, 108, 103, 34, 58, 34, 72, 83, 50, 53, 54, 34, 125]

   Base64url encoding these octets yields this Encoded JWS Header value:

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

   The JWS Payload used in this example is the octets of the UTF-8
   representation of the JSON object below.  (Note that the payload can
   be any base64url encoded octet sequence, and need not be a base64url
   encoded JSON object.)

     {"iss":"joe",
      "exp":1300819380,
      "http://example.com/is_root":true}

   The following octet sequence, which is the UTF-8 representation of
   the JSON object above, is the JWS Payload:

   [123, 34, 105, 115, 115, 34, 58, 34, 106, 111, 101, 34, 44, 13, 10,
   32, 34, 101, 120, 112, 34, 58, 49, 51, 48, 48, 56, 49, 57, 51, 56,
   48, 44, 13, 10, 32, 34, 104, 116, 116, 112, 58, 47, 47, 101, 120, 97,
   109, 112, 108, 101, 46, 99, 111, 109, 47, 105, 115, 95, 114, 111,
   111, 116, 34, 58, 116, 114, 117, 101, 125]

   Base64url encoding the JWS Payload yields this Encoded JWS Payload
   value (with line breaks for display purposes only):

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   Concatenating the Encoded JWS Header, a period ('.') character, and
   the Encoded JWS Payload yields this JWS Signing Input value (with
   line breaks for display purposes only):



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     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The ASCII representation of the JWS Signing Input is the following
   octet sequence:

   [101, 121, 74, 48, 101, 88, 65, 105, 79, 105, 74, 75, 86, 49, 81,
   105, 76, 65, 48, 75, 73, 67, 74, 104, 98, 71, 99, 105, 79, 105, 74,
   73, 85, 122, 73, 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51,
   77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67,
   74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84,
   107, 122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100,
   72, 65, 54, 76, 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76,
   109, 78, 118, 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73,
   106, 112, 48, 99, 110, 86, 108, 102, 81]

   HMACs are generated using keys.  This example uses the symmetric key
   represented in JSON Web Key [JWK] format below (with line breaks for
   display purposes only):

     {"kty":"oct",
      "k":"AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75
           aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
     }

   Running the HMAC SHA-256 algorithm on the octets of the ASCII
   representation of the JWS Signing Input with this key yields this
   octet sequence:

   [116, 24, 223, 180, 151, 153, 224, 37, 79, 250, 96, 125, 216, 173,
   187, 186, 22, 212, 37, 77, 105, 214, 191, 240, 91, 88, 5, 88, 83,
   132, 141, 121]

   Base64url encoding the above HMAC output yields this Encoded JWS
   Signature value:

     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

   Concatenating these values in the order Header.Payload.Signature with
   period ('.') characters between the parts yields this complete JWS
   representation using the JWS Compact Serialization (with line breaks
   for display purposes only):







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     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .
     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

A.1.2.  Decoding

   Decoding the JWS requires base64url decoding the Encoded JWS Header,
   Encoded JWS Payload, and Encoded JWS Signature to produce the JWS
   Header, JWS Payload, and JWS Signature octet sequences.  The octet
   sequence containing the UTF-8 representation of the JWS Header is
   decoded into the JWS Header string.

A.1.3.  Validating

   Next we validate the decoded results.  Since the "alg" parameter in
   the header is "HS256", we validate the HMAC SHA-256 value contained
   in the JWS Signature.  If any of the validation steps fail, the JWS
   MUST be rejected.

   First, we validate that the JWS Header string is legal JSON.

   To validate the HMAC value, we repeat the previous process of using
   the correct key and the ASCII representation of the JWS Signing Input
   as input to the HMAC SHA-256 function and then taking the output and
   determining if it matches the JWS Signature.  If it matches exactly,
   the HMAC has been validated.

A.2.  Example JWS using RSASSA-PKCS-v1_5 SHA-256

A.2.1.  Encoding

   The JWS Header in this example is different from the previous example
   in two ways: First, because a different algorithm is being used, the
   "alg" value is different.  Second, for illustration purposes only,
   the optional "typ" parameter is not used.  (This difference is not
   related to the algorithm employed.)  The JWS Header used is:

     {"alg":"RS256"}

   The following octet sequence contains the UTF-8 representation of the
   JWS Header:

   [123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125]

   Base64url encoding these octets yields this Encoded JWS Header value:



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     eyJhbGciOiJSUzI1NiJ9

   The JWS Payload used in this example, which follows, is the same as
   in the previous example.  Since the Encoded JWS Payload will
   therefore be the same, its computation is not repeated here.

     {"iss":"joe",
      "exp":1300819380,
      "http://example.com/is_root":true}

   Concatenating the Encoded JWS Header, a period ('.') character, and
   the Encoded JWS Payload yields this JWS Signing Input value (with
   line breaks for display purposes only):

     eyJhbGciOiJSUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The ASCII representation of the JWS Signing Input is the following
   octet sequence:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 122, 73,
   49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105,
   74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72,
   65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68,
   65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76,
   121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118,
   98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48,
   99, 110, 86, 108, 102, 81]

   This example uses the RSA key represented in JSON Web Key [JWK]
   format below (with line breaks for display purposes only):

     {"kty":"RSA",
      "n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx
           HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs
           D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH
           SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV
           MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8
           NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ",
      "e":"AQAB",
      "d":"Eq5xpGnNCivDflJsRQBXHx1hdR1k6Ulwe2JZD50LpXyWPEAeP88vLNO97I
           jlA7_GQ5sLKMgvfTeXZx9SE-7YwVol2NXOoAJe46sui395IW_GO-pWJ1O0
           BkTGoVEn2bKVRUCgu-GjBVaYLU6f3l9kJfFNS3E0QbVdxzubSu3Mkqzjkn
           439X0M_V51gfpRLI9JYanrC4D4qAdGcopV_0ZHHzQlBjudU2QvXt4ehNYT
           CBr6XCLQUShb1juUO1ZdiYoFaFQT5Tw8bGUl_x_jTj3ccPDVZFD9pIuhLh
           BOneufuBiB4cS98l2SR_RQyGWSeWjnczT0QU91p1DhOVRuOopznQ"



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     }

   The RSA private key is then passed to the RSA signing function, which
   also takes the hash type, SHA-256, and the octets of the ASCII
   representation of the JWS Signing Input as inputs.  The result of the
   digital signature is an octet sequence, which represents a big endian
   integer.  In this example, it is:

   [112, 46, 33, 137, 67, 232, 143, 209, 30, 181, 216, 45, 191, 120, 69,
   243, 65, 6, 174, 27, 129, 255, 247, 115, 17, 22, 173, 209, 113, 125,
   131, 101, 109, 66, 10, 253, 60, 150, 238, 221, 115, 162, 102, 62, 81,
   102, 104, 123, 0, 11, 135, 34, 110, 1, 135, 237, 16, 115, 249, 69,
   229, 130, 173, 252, 239, 22, 216, 90, 121, 142, 232, 198, 109, 219,
   61, 184, 151, 91, 23, 208, 148, 2, 190, 237, 213, 217, 217, 112, 7,
   16, 141, 178, 129, 96, 213, 248, 4, 12, 167, 68, 87, 98, 184, 31,
   190, 127, 249, 217, 46, 10, 231, 111, 36, 242, 91, 51, 187, 230, 244,
   74, 230, 30, 177, 4, 10, 203, 32, 4, 77, 62, 249, 18, 142, 212, 1,
   48, 121, 91, 212, 189, 59, 65, 238, 202, 208, 102, 171, 101, 25, 129,
   253, 228, 141, 247, 127, 55, 45, 195, 139, 159, 175, 221, 59, 239,
   177, 139, 93, 163, 204, 60, 46, 176, 47, 158, 58, 65, 214, 18, 202,
   173, 21, 145, 18, 115, 160, 95, 35, 185, 232, 56, 250, 175, 132, 157,
   105, 132, 41, 239, 90, 30, 136, 121, 130, 54, 195, 212, 14, 96, 69,
   34, 165, 68, 200, 242, 122, 122, 45, 184, 6, 99, 209, 108, 247, 202,
   234, 86, 222, 64, 92, 178, 33, 90, 69, 178, 194, 85, 102, 181, 90,
   193, 167, 72, 160, 112, 223, 200, 163, 42, 70, 149, 67, 208, 25, 238,
   251, 71]

   Base64url encoding the digital signature produces this value for the
   Encoded JWS Signature (with line breaks for display purposes only):

     cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7
     AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4
     BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K
     0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv
     hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB
     p0igcN_IoypGlUPQGe77Rw

   Concatenating these values in the order Header.Payload.Signature with
   period ('.') characters between the parts yields this complete JWS
   representation using the JWS Compact Serialization (with line breaks
   for display purposes only):










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     eyJhbGciOiJSUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .
     cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7
     AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4
     BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K
     0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv
     hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB
     p0igcN_IoypGlUPQGe77Rw

A.2.2.  Decoding

   Decoding the JWS requires base64url decoding the Encoded JWS Header,
   Encoded JWS Payload, and Encoded JWS Signature to produce the JWS
   Header, JWS Payload, and JWS Signature octet sequences.  The octet
   sequence containing the UTF-8 representation of the JWS Header is
   decoded into the JWS Header string.

A.2.3.  Validating

   Since the "alg" parameter in the header is "RS256", we validate the
   RSASSA-PKCS-v1_5 SHA-256 digital signature contained in the JWS
   Signature.  If any of the validation steps fail, the JWS MUST be
   rejected.

   First, we validate that the JWS Header string is legal JSON.

   Validating the JWS Signature is a little different from the previous
   example.  First, we base64url decode the Encoded JWS Signature to
   produce a digital signature S to check.  We then pass (n, e), S and
   the octets of the ASCII representation of the JWS Signing Input to an
   RSASSA-PKCS-v1_5 signature verifier that has been configured to use
   the SHA-256 hash function.

A.3.  Example JWS using ECDSA P-256 SHA-256

A.3.1.  Encoding

   The JWS Header for this example differs from the previous example
   because a different algorithm is being used.  The JWS Header used is:

     {"alg":"ES256"}

   The following octet sequence contains the UTF-8 representation of the
   JWS Header:




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   [123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125]

   Base64url encoding these octets yields this Encoded JWS Header value:

     eyJhbGciOiJFUzI1NiJ9

   The JWS Payload used in this example, which follows, is the same as
   in the previous examples.  Since the Encoded JWS Payload will
   therefore be the same, its computation is not repeated here.

     {"iss":"joe",
      "exp":1300819380,
      "http://example.com/is_root":true}

   Concatenating the Encoded JWS Header, a period ('.') character, and
   the Encoded JWS Payload yields this JWS Signing Input value (with
   line breaks for display purposes only):

     eyJhbGciOiJFUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The ASCII representation of the JWS Signing Input is the following
   octet sequence:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 73,
   49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105,
   74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72,
   65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68,
   65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76,
   121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118,
   98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48,
   99, 110, 86, 108, 102, 81]

   This example uses the elliptic curve key represented in JSON Web Key
   [JWK] format below:

     {"kty":"EC",
      "crv":"P-256",
      "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",
      "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0",
      "d":"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI"
     }

   The ECDSA private part d is then passed to an ECDSA signing function,
   which also takes the curve type, P-256, the hash type, SHA-256, and
   the octets of the ASCII representation of the JWS Signing Input as



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   inputs.  The result of the digital signature is the EC point (R, S),
   where R and S are unsigned integers.  In this example, the R and S
   values, given as octet sequences representing big endian integers
   are:

   +--------+----------------------------------------------------------+
   | Result | Value                                                    |
   | Name   |                                                          |
   +--------+----------------------------------------------------------+
   | R      | [14, 209, 33, 83, 121, 99, 108, 72, 60, 47, 127, 21, 88, |
   |        | 7, 212, 2, 163, 178, 40, 3, 58, 249, 124, 126, 23, 129,  |
   |        | 154, 195, 22, 158, 166, 101]                             |
   | S      | [197, 10, 7, 211, 140, 60, 112, 229, 216, 241, 45, 175,  |
   |        | 8, 74, 84, 128, 166, 101, 144, 197, 242, 147, 80, 154,   |
   |        | 143, 63, 127, 138, 131, 163, 84, 213]                    |
   +--------+----------------------------------------------------------+

   Concatenating the S array to the end of the R array and base64url
   encoding the result produces this value for the Encoded JWS Signature
   (with line breaks for display purposes only):

     DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA
     pmWQxfKTUJqPP3-Kg6NU1Q

   Concatenating these values in the order Header.Payload.Signature with
   period ('.') characters between the parts yields this complete JWS
   representation using the JWS Compact Serialization (with line breaks
   for display purposes only):

     eyJhbGciOiJFUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .
     DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA
     pmWQxfKTUJqPP3-Kg6NU1Q

A.3.2.  Decoding

   Decoding the JWS requires base64url decoding the Encoded JWS Header,
   Encoded JWS Payload, and Encoded JWS Signature to produce the JWS
   Header, JWS Payload, and JWS Signature octet sequences.  The octet
   sequence containing the UTF-8 representation of the JWS Header is
   decoded into the JWS Header string.







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A.3.3.  Validating

   Since the "alg" parameter in the header is "ES256", we validate the
   ECDSA P-256 SHA-256 digital signature contained in the JWS Signature.
   If any of the validation steps fail, the JWS MUST be rejected.

   First, we validate that the JWS Header string is legal JSON.

   Validating the JWS Signature is a little different from the first
   example.  First, we base64url decode the Encoded JWS Signature as in
   the previous examples but we then need to split the 64 member octet
   sequence that must result into two 32 octet sequences, the first R
   and the second S. We then pass (x, y), (R, S) and the octets of the
   ASCII representation of the JWS Signing Input to an ECDSA signature
   verifier that has been configured to use the P-256 curve with the
   SHA-256 hash function.

   As explained in Section 3.4 of the JSON Web Algorithms (JWA) [JWA]
   specification, the use of the K value in ECDSA means that we cannot
   validate the correctness of the digital signature in the same way we
   validated the correctness of the HMAC.  Instead, implementations MUST
   use an ECDSA validator to validate the digital signature.

A.4.  Example JWS using ECDSA P-521 SHA-512

A.4.1.  Encoding

   The JWS Header for this example differs from the previous example
   because different ECDSA curves and hash functions are used.  The JWS
   Header used is:

     {"alg":"ES512"}

   The following octet sequence contains the UTF-8 representation of the
   JWS Header:

   [123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 53, 49, 50, 34, 125]

   Base64url encoding these octets yields this Encoded JWS Header value:

     eyJhbGciOiJFUzUxMiJ9

   The JWS Payload used in this example, is the ASCII string "Payload".
   The representation of this string is the octet sequence:

   [80, 97, 121, 108, 111, 97, 100]

   Base64url encoding these octets yields this Encoded JWS Payload



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   value:

     UGF5bG9hZA

   Concatenating the Encoded JWS Header, a period ('.') character, and
   the Encoded JWS Payload yields this JWS Signing Input value:

     eyJhbGciOiJFUzUxMiJ9.UGF5bG9hZA

   The ASCII representation of the JWS Signing Input is the following
   octet sequence:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 85,
   120, 77, 105, 74, 57, 46, 85, 71, 70, 53, 98, 71, 57, 104, 90, 65]

   This example uses the elliptic curve key represented in JSON Web Key
   [JWK] format below (with line breaks for display purposes only):

     {"kty":"EC",
      "crv":"P-521",
      "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_
           NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk",
      "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDl
           y79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2",
      "d":"AY5pb7A0UFiB3RELSD64fTLOSV_jazdF7fLYyuTw8lOfRhWg6Y6rUrPA
           xerEzgdRhajnu0ferB0d53vM9mE15j2C"
     }

   The ECDSA private part d is then passed to an ECDSA signing function,
   which also takes the curve type, P-521, the hash type, SHA-512, and
   the octets of the ASCII representation of the JWS Signing Input as
   inputs.  The result of the digital signature is the EC point (R, S),
   where R and S are unsigned integers.  In this example, the R and S
   values, given as octet sequences representing big endian integers
   are:

   +--------+----------------------------------------------------------+
   | Result | Value                                                    |
   | Name   |                                                          |
   +--------+----------------------------------------------------------+
   | R      | [1, 220, 12, 129, 231, 171, 194, 209, 232, 135, 233,     |
   |        | 117, 247, 105, 122, 210, 26, 125, 192, 1, 217, 21, 82,   |
   |        | 91, 45, 240, 255, 83, 19, 34, 239, 71, 48, 157, 147,     |
   |        | 152, 105, 18, 53, 108, 163, 214, 68, 231, 62, 153, 150,  |
   |        | 106, 194, 164, 246, 72, 143, 138, 24, 50, 129, 223, 133, |
   |        | 206, 209, 172, 63, 237, 119, 109]                        |





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   | S      | [0, 111, 6, 105, 44, 5, 41, 208, 128, 61, 152, 40, 92,   |
   |        | 61, 152, 4, 150, 66, 60, 69, 247, 196, 170, 81, 193,     |
   |        | 199, 78, 59, 194, 169, 16, 124, 9, 143, 42, 142, 131,    |
   |        | 48, 206, 238, 34, 175, 83, 203, 220, 159, 3, 107, 155,   |
   |        | 22, 27, 73, 111, 68, 68, 21, 238, 144, 229, 232, 148,    |
   |        | 188, 222, 59, 242, 103]                                  |
   +--------+----------------------------------------------------------+

   Concatenating the S array to the end of the R array and base64url
   encoding the result produces this value for the Encoded JWS Signature
   (with line breaks for display purposes only):

     AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq
     wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp
     EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn

   Concatenating these values in the order Header.Payload.Signature with
   period ('.') characters between the parts yields this complete JWS
   representation using the JWS Compact Serialization (with line breaks
   for display purposes only):

     eyJhbGciOiJFUzUxMiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .
     AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq
     wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp
     EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn

A.4.2.  Decoding

   Decoding the JWS requires base64url decoding the Encoded JWS Header,
   Encoded JWS Payload, and Encoded JWS Signature to produce the JWS
   Header, JWS Payload, and JWS Signature octet sequences.  The octet
   sequence containing the UTF-8 representation of the JWS Header is
   decoded into the JWS Header string.

A.4.3.  Validating

   Since the "alg" parameter in the header is "ES512", we validate the
   ECDSA P-521 SHA-512 digital signature contained in the JWS Signature.
   If any of the validation steps fail, the JWS MUST be rejected.

   First, we validate that the JWS Header string is legal JSON.

   Validating the JWS Signature is similar to the previous example.
   First, we base64url decode the Encoded JWS Signature as in the



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   previous examples but we then need to split the 132 member octet
   sequence that must result into two 66 octet sequences, the first R
   and the second S. We then pass (x, y), (R, S) and the octets of the
   ASCII representation of the JWS Signing Input to an ECDSA signature
   verifier that has been configured to use the P-521 curve with the
   SHA-512 hash function.

   As explained in Section 3.4 of the JSON Web Algorithms (JWA) [JWA]
   specification, the use of the K value in ECDSA means that we cannot
   validate the correctness of the digital signature in the same way we
   validated the correctness of the HMAC.  Instead, implementations MUST
   use an ECDSA validator to validate the digital signature.

A.5.  Example Plaintext JWS

   The following example JWS Header declares that the encoded object is
   a Plaintext JWS:

     {"alg":"none"}

   Base64url encoding the octets of the UTF-8 representation of the JWS
   Header yields this Encoded JWS Header:

     eyJhbGciOiJub25lIn0

   The JWS Payload used in this example, which follows, is the same as
   in the previous examples.  Since the Encoded JWS Payload will
   therefore be the same, its computation is not repeated here.

     {"iss":"joe",
      "exp":1300819380,
      "http://example.com/is_root":true}

   The Encoded JWS Signature is the empty string.

   Concatenating these parts in the order Header.Payload.Signature with
   period ('.') characters between the parts yields this complete JWS
   (with line breaks for display purposes only):

     eyJhbGciOiJub25lIn0
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .







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A.6.  Example JWS Using JWS JSON Serialization

   This section contains an example using the JWS JSON Serialization.
   This example demonstrates the capability for conveying multiple
   digital signatures and/or MACs for the same payload.

   The Encoded JWS Payload used in this example is the same as that used
   in the examples in Appendix A.2 and Appendix A.3 (with line breaks
   for display purposes only):

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   Two digital signatures are used in this example: the first using
   RSASSA-PKCS-v1_5 SHA-256 and the second using ECDSA P-256 SHA-256.
   For the first, the JWS Protected Header and key are the same as in
   Appendix A.2, resulting in the same JWS Signature value; therefore,
   its computation is not repeated here.  For the second, the JWS
   Protected Header and key are the same as in Appendix A.3, resulting
   in the same JWS Signature value; therefore, its computation is not
   repeated here.

A.6.1.  JWS Per-Signature Protected Headers

   The JWS Protected Header value used for the first signature is:

     {"alg":"RS256"}

   Base64url encoding these octets yields this Encoded JWS Header value:

     eyJhbGciOiJSUzI1NiJ9

   The JWS Protected Header value used for the second signature is:

     {"alg":"ES256"}

   Base64url encoding these octets yields this Encoded JWS Header value:

     eyJhbGciOiJFUzI1NiJ9

A.6.2.  JWS Per-Signature Unprotected Headers

   Key ID values are supplied for both keys using per-signature header
   parameters.  The two values used to represent these Key IDs are:

     {"kid":"2010-12-29"}

   and:



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     {"kid":"e9bc097a-ce51-4036-9562-d2ade882db0d"}

A.6.3.  Complete JWS Header Values

   Combining the protected and unprotected header values supplied, the
   JWS Header values used for the first and second signatures
   respectively are:

     {"alg":"RS256",
      "kid":"2010-12-29"}

   and:

     {"alg":"ES256",
      "kid":"e9bc097a-ce51-4036-9562-d2ade882db0d"}

A.6.4.  Complete JWS JSON Serialization Representation

   The complete JSON Web Signature JSON Serialization for these values
   is as follows (with line breaks for display purposes only):

     {"payload":
       "eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGF
        tcGxlLmNvbS9pc19yb290Ijp0cnVlfQ",
      "signatures":[
       {"protected":"eyJhbGciOiJSUzI1NiJ9",
        "header":
         {"kid":"2010-12-29"},
        "signature":
         "cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZ
          mh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjb
          KBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHl
          b1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZES
          c6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AX
          LIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw"},
       {"protected":"eyJhbGciOiJFUzI1NiJ9",
        "header":
         {"kid":"e9bc097a-ce51-4036-9562-d2ade882db0d"},
        "signature":
         "DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8IS
          lSApmWQxfKTUJqPP3-Kg6NU1Q"}]
     }


Appendix B.  "x5c" (X.509 Certificate Chain) Example

   The JSON array below is an example of a certificate chain that could
   be used as the value of an "x5c" (X.509 Certificate Chain) header



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   parameter, per Section 4.1.6.  Note that since these strings contain
   base64 encoded (not base64url encoded) values, they are allowed to
   contain white space and line breaks.

     ["MIIE3jCCA8agAwIBAgICAwEwDQYJKoZIhvcNAQEFBQAwYzELMAkGA1UEBhMCVVM
       xITAfBgNVBAoTGFRoZSBHbyBEYWRkeSBHcm91cCwgSW5jLjExMC8GA1UECxMoR2
       8gRGFkZHkgQ2xhc3MgMiBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTAeFw0wNjExM
       TYwMTU0MzdaFw0yNjExMTYwMTU0MzdaMIHKMQswCQYDVQQGEwJVUzEQMA4GA1UE
       CBMHQXJpem9uYTETMBEGA1UEBxMKU2NvdHRzZGFsZTEaMBgGA1UEChMRR29EYWR
       keS5jb20sIEluYy4xMzAxBgNVBAsTKmh0dHA6Ly9jZXJ0aWZpY2F0ZXMuZ29kYW
       RkeS5jb20vcmVwb3NpdG9yeTEwMC4GA1UEAxMnR28gRGFkZHkgU2VjdXJlIENlc
       nRpZmljYXRpb24gQXV0aG9yaXR5MREwDwYDVQQFEwgwNzk2OTI4NzCCASIwDQYJ
       KoZIhvcNAQEBBQADggEPADCCAQoCggEBAMQt1RWMnCZM7DI161+4WQFapmGBWTt
       wY6vj3D3HKrjJM9N55DrtPDAjhI6zMBS2sofDPZVUBJ7fmd0LJR4h3mUpfjWoqV
       Tr9vcyOdQmVZWt7/v+WIbXnvQAjYwqDL1CBM6nPwT27oDyqu9SoWlm2r4arV3aL
       GbqGmu75RpRSgAvSMeYddi5Kcju+GZtCpyz8/x4fKL4o/K1w/O5epHBp+YlLpyo
       7RJlbmr2EkRTcDCVw5wrWCs9CHRK8r5RsL+H0EwnWGu1NcWdrxcx+AuP7q2BNgW
       JCJjPOq8lh8BJ6qf9Z/dFjpfMFDniNoW1fho3/Rb2cRGadDAW/hOUoz+EDU8CAw
       EAAaOCATIwggEuMB0GA1UdDgQWBBT9rGEyk2xF1uLuhV+auud2mWjM5zAfBgNVH
       SMEGDAWgBTSxLDSkdRMEXGzYcs9of7dqGrU4zASBgNVHRMBAf8ECDAGAQH/AgEA
       MDMGCCsGAQUFBwEBBCcwJTAjBggrBgEFBQcwAYYXaHR0cDovL29jc3AuZ29kYWR
       keS5jb20wRgYDVR0fBD8wPTA7oDmgN4Y1aHR0cDovL2NlcnRpZmljYXRlcy5nb2
       RhZGR5LmNvbS9yZXBvc2l0b3J5L2dkcm9vdC5jcmwwSwYDVR0gBEQwQjBABgRVH
       SAAMDgwNgYIKwYBBQUHAgEWKmh0dHA6Ly9jZXJ0aWZpY2F0ZXMuZ29kYWRkeS5j
       b20vcmVwb3NpdG9yeTAOBgNVHQ8BAf8EBAMCAQYwDQYJKoZIhvcNAQEFBQADggE
       BANKGwOy9+aG2Z+5mC6IGOgRQjhVyrEp0lVPLN8tESe8HkGsz2ZbwlFalEzAFPI
       UyIXvJxwqoJKSQ3kbTJSMUA2fCENZvD117esyfxVgqwcSeIaha86ykRvOe5GPLL
       5CkKSkB2XIsKd83ASe8T+5o0yGPwLPk9Qnt0hCqU7S+8MxZC9Y7lhyVJEnfzuz9
       p0iRFEUOOjZv2kWzRaJBydTXRE4+uXR21aITVSzGh6O1mawGhId/dQb8vxRMDsx
       uxN89txJx9OjxUUAiKEngHUuHqDTMBqLdElrRhjZkAzVvb3du6/KFUJheqwNTrZ
       EjYx8WnM25sgVjOuH0aBsXBTWVU+4=",
      "MIIE+zCCBGSgAwIBAgICAQ0wDQYJKoZIhvcNAQEFBQAwgbsxJDAiBgNVBAcTG1Z
       hbGlDZXJ0IFZhbGlkYXRpb24gTmV0d29yazEXMBUGA1UEChMOVmFsaUNlcnQsIE
       luYy4xNTAzBgNVBAsTLFZhbGlDZXJ0IENsYXNzIDIgUG9saWN5IFZhbGlkYXRpb
       24gQXV0aG9yaXR5MSEwHwYDVQQDExhodHRwOi8vd3d3LnZhbGljZXJ0LmNvbS8x
       IDAeBgkqhkiG9w0BCQEWEWluZm9AdmFsaWNlcnQuY29tMB4XDTA0MDYyOTE3MDY
       yMFoXDTI0MDYyOTE3MDYyMFowYzELMAkGA1UEBhMCVVMxITAfBgNVBAoTGFRoZS
       BHbyBEYWRkeSBHcm91cCwgSW5jLjExMC8GA1UECxMoR28gRGFkZHkgQ2xhc3MgM
       iBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTCCASAwDQYJKoZIhvcNAQEBBQADggEN
       ADCCAQgCggEBAN6d1+pXGEmhW+vXX0iG6r7d/+TvZxz0ZWizV3GgXne77ZtJ6XC
       APVYYYwhv2vLM0D9/AlQiVBDYsoHUwHU9S3/Hd8M+eKsaA7Ugay9qK7HFiH7Eux
       6wwdhFJ2+qN1j3hybX2C32qRe3H3I2TqYXP2WYktsqbl2i/ojgC95/5Y0V4evLO
       tXiEqITLdiOr18SPaAIBQi2XKVlOARFmR6jYGB0xUGlcmIbYsUfb18aQr4CUWWo
       riMYavx4A6lNf4DD+qta/KFApMoZFv6yyO9ecw3ud72a9nmYvLEHZ6IVDd2gWMZ
       Eewo+YihfukEHU1jPEX44dMX4/7VpkI+EdOqXG68CAQOjggHhMIIB3TAdBgNVHQ
       4EFgQU0sSw0pHUTBFxs2HLPaH+3ahq1OMwgdIGA1UdIwSByjCBx6GBwaSBvjCBu
       zEkMCIGA1UEBxMbVmFsaUNlcnQgVmFsaWRhdGlvbiBOZXR3b3JrMRcwFQYDVQQK
       Ew5WYWxpQ2VydCwgSW5jLjE1MDMGA1UECxMsVmFsaUNlcnQgQ2xhc3MgMiBQb2x



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       pY3kgVmFsaWRhdGlvbiBBdXRob3JpdHkxITAfBgNVBAMTGGh0dHA6Ly93d3cudm
       FsaWNlcnQuY29tLzEgMB4GCSqGSIb3DQEJARYRaW5mb0B2YWxpY2VydC5jb22CA
       QEwDwYDVR0TAQH/BAUwAwEB/zAzBggrBgEFBQcBAQQnMCUwIwYIKwYBBQUHMAGG
       F2h0dHA6Ly9vY3NwLmdvZGFkZHkuY29tMEQGA1UdHwQ9MDswOaA3oDWGM2h0dHA
       6Ly9jZXJ0aWZpY2F0ZXMuZ29kYWRkeS5jb20vcmVwb3NpdG9yeS9yb290LmNybD
       BLBgNVHSAERDBCMEAGBFUdIAAwODA2BggrBgEFBQcCARYqaHR0cDovL2NlcnRpZ
       mljYXRlcy5nb2RhZGR5LmNvbS9yZXBvc2l0b3J5MA4GA1UdDwEB/wQEAwIBBjAN
       BgkqhkiG9w0BAQUFAAOBgQC1QPmnHfbq/qQaQlpE9xXUhUaJwL6e4+PrxeNYiY+
       Sn1eocSxI0YGyeR+sBjUZsE4OWBsUs5iB0QQeyAfJg594RAoYC5jcdnplDQ1tgM
       QLARzLrUc+cb53S8wGd9D0VmsfSxOaFIqII6hR8INMqzW/Rn453HWkrugp++85j
       09VZw==",
      "MIIC5zCCAlACAQEwDQYJKoZIhvcNAQEFBQAwgbsxJDAiBgNVBAcTG1ZhbGlDZXJ
       0IFZhbGlkYXRpb24gTmV0d29yazEXMBUGA1UEChMOVmFsaUNlcnQsIEluYy4xNT
       AzBgNVBAsTLFZhbGlDZXJ0IENsYXNzIDIgUG9saWN5IFZhbGlkYXRpb24gQXV0a
       G9yaXR5MSEwHwYDVQQDExhodHRwOi8vd3d3LnZhbGljZXJ0LmNvbS8xIDAeBgkq
       hkiG9w0BCQEWEWluZm9AdmFsaWNlcnQuY29tMB4XDTk5MDYyNjAwMTk1NFoXDTE
       5MDYyNjAwMTk1NFowgbsxJDAiBgNVBAcTG1ZhbGlDZXJ0IFZhbGlkYXRpb24gTm
       V0d29yazEXMBUGA1UEChMOVmFsaUNlcnQsIEluYy4xNTAzBgNVBAsTLFZhbGlDZ
       XJ0IENsYXNzIDIgUG9saWN5IFZhbGlkYXRpb24gQXV0aG9yaXR5MSEwHwYDVQQD
       ExhodHRwOi8vd3d3LnZhbGljZXJ0LmNvbS8xIDAeBgkqhkiG9w0BCQEWEWluZm9
       AdmFsaWNlcnQuY29tMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDOOnHK5a
       vIWZJV16vYdA757tn2VUdZZUcOBVXc65g2PFxTXdMwzzjsvUGJ7SVCCSRrCl6zf
       N1SLUzm1NZ9WlmpZdRJEy0kTRxQb7XBhVQ7/nHk01xC+YDgkRoKWzk2Z/M/VXwb
       P7RfZHM047QSv4dk+NoS/zcnwbNDu+97bi5p9wIDAQABMA0GCSqGSIb3DQEBBQU
       AA4GBADt/UG9vUJSZSWI4OB9L+KXIPqeCgfYrx+jFzug6EILLGACOTb2oWH+heQ
       C1u+mNr0HZDzTuIYEZoDJJKPTEjlbVUjP9UNV+mWwD5MlM/Mtsq2azSiGM5bUMM
       j4QssxsodyamEwCW/POuZ6lcg5Ktz885hZo+L7tdEy8W9ViH0Pd"]


Appendix C.  Notes on implementing base64url encoding without padding

   This appendix describes how to implement base64url encoding and
   decoding functions without padding based upon standard base64
   encoding and decoding functions that do use padding.

   To be concrete, example C# code implementing these functions is shown
   below.  Similar code could be used in other languages.














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     static string base64urlencode(byte [] arg)
     {
       string s = Convert.ToBase64String(arg); // Regular base64 encoder
       s = s.Split('=')[0]; // Remove any trailing '='s
       s = s.Replace('+', '-'); // 62nd char of encoding
       s = s.Replace('/', '_'); // 63rd char of encoding
       return s;
     }

     static byte [] base64urldecode(string arg)
     {
       string s = arg;
       s = s.Replace('-', '+'); // 62nd char of encoding
       s = s.Replace('_', '/'); // 63rd char of encoding
       switch (s.Length % 4) // Pad with trailing '='s
       {
         case 0: break; // No pad chars in this case
         case 2: s += "=="; break; // Two pad chars
         case 3: s += "="; break; // One pad char
         default: throw new System.Exception(
           "Illegal base64url string!");
       }
       return Convert.FromBase64String(s); // Standard base64 decoder
     }

   As per the example code above, the number of '=' padding characters
   that needs to be added to the end of a base64url encoded string
   without padding to turn it into one with padding is a deterministic
   function of the length of the encoded string.  Specifically, if the
   length mod 4 is 0, no padding is added; if the length mod 4 is 2, two
   '=' padding characters are added; if the length mod 4 is 3, one '='
   padding character is added; if the length mod 4 is 1, the input is
   malformed.

   An example correspondence between unencoded and encoded values
   follows.  The octet sequence below encodes into the string below,
   which when decoded, reproduces the octet sequence.
   3 236 255 224 193
   A-z_4ME


Appendix D.  Negative Test Case for "crit" Header Parameter

   Conforming implementations must reject input containing critical
   extensions that are not understood or cannot be processed.  The
   following JWS must be rejected by all implementations, because it
   uses an extension header parameter name
   "http://example.invalid/UNDEFINED" that they do not understand.  Any



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   other similar input, in which the use of the value
   "http://example.invalid/UNDEFINED" is substituted for any other
   header parameter name not understood by the implementation, must also
   be rejected.

   The JWS Header value for this JWS is:

     {"alg":"none",
      "crit":["http://example.invalid/UNDEFINED"],
      "http://example.invalid/UNDEFINED":true
     }

   The complete JWS that must be rejected is as follows (with line
   breaks for display purposes only):

     eyJhbGciOiJub25lIiwNCiAiY3JpdCI6WyJodHRwOi8vZXhhbXBsZS5jb20vVU5ERU
     ZJTkVEIl0sDQogImh0dHA6Ly9leGFtcGxlLmNvbS9VTkRFRklORUQiOnRydWUNCn0.
     RkFJTA.


Appendix E.  Acknowledgements

   Solutions for signing JSON content were previously explored by Magic
   Signatures [MagicSignatures], JSON Simple Sign [JSS], and Canvas
   Applications [CanvasApp], all of which influenced this draft.

   Thanks to Axel Nennker for his early implementation and feedback on
   the JWS and JWE specifications.

   This specification is the work of the JOSE Working Group, which
   includes dozens of active and dedicated participants.  In particular,
   the following individuals contributed ideas, feedback, and wording
   that influenced this specification:

   Dirk Balfanz, Richard Barnes, Brian Campbell, Breno de Medeiros, Dick
   Hardt, Joe Hildebrand, Jeff Hodges, Edmund Jay, Yaron Y. Goland, Ben
   Laurie, James Manger, Matt Miller, Tony Nadalin, Axel Nennker, John
   Panzer, Emmanuel Raviart, Eric Rescorla, Jim Schaad, Paul Tarjan,
   Hannes Tschofenig, and Sean Turner.

   Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
   Sean Turner and Stephen Farrell served as Security area directors
   during the creation of this specification.


Appendix F.  Document History

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



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   -14

   o  Stated that the "signature" parameter is to be omitted in the JWS
      JSON Serialization when its value would be empty (which is only
      the case for a Plaintext JWS).

   -13

   o  Made all header parameter values be per-signature/MAC, addressing
      issue #24.

   -12

   o  Clarified that the "typ" and "cty" header parameters are used in
      an application-specific manner and have no effect upon the JWS
      processing.

   o  Replaced the MIME types "application/jws+json" and
      "application/jws" with "application/jose+json" and
      "application/jose".

   o  Stated that recipients MUST either reject JWSs with duplicate
      Header Parameter Names or use a JSON parser that returns only the
      lexically last duplicate member name.

   o  Added a Serializations section with parallel treatment of the JWS
      Compact Serialization and the JWS JSON Serialization and also
      moved the former Implementation Considerations content there.

   -11

   o  Added Key Identification section.

   o  For the JWS JSON Serialization, enable header parameter values to
      be specified in any of three parameters: the "protected" member
      that is integrity protected and shared among all recipients, the
      "unprotected" member that is not integrity protected and shared
      among all recipients, and the "header" member that is not
      integrity protected and specific to a particular recipient.  (This
      does not affect the JWS Compact Serialization, in which all header
      parameter values are in a single integrity protected JWE Header
      value.)

   o  Removed suggested compact serialization for multiple digital
      signatures and/or MACs.

   o  Changed the MIME type name "application/jws-js" to
      "application/jws+json", addressing issue #22.



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   o  Tightened the description of the "crit" (critical) header
      parameter.

   o  Added a negative test case for the "crit" header parameter

   -10

   o  Added an appendix suggesting a possible compact serialization for
      JWSs with multiple digital signatures and/or MACs.

   -09

   o  Added JWS JSON Serialization, as specified by
      draft-jones-jose-jws-json-serialization-04.

   o  Registered "application/jws-js" MIME type and "JWS-JS" typ header
      parameter value.

   o  Defined that the default action for header parameters that are not
      understood is to ignore them unless specifically designated as
      "MUST be understood" or included in the new "crit" (critical)
      header parameter list.  This addressed issue #6.

   o  Changed term "JWS Secured Input" to "JWS Signing Input".

   o  Changed from using the term "byte" to "octet" when referring to 8
      bit values.

   o  Changed member name from "recipients" to "signatures" in the JWS
      JSON Serialization.

   o  Added complete values using the JWS Compact Serialization for all
      examples.

   -08

   o  Applied editorial improvements suggested by Jeff Hodges and Hannes
      Tschofenig.  Many of these simplified the terminology used.

   o  Clarified statements of the form "This header parameter is
      OPTIONAL" to "Use of this header parameter is OPTIONAL".

   o  Added a Header Parameter Usage Location(s) field to the IANA JSON
      Web Signature and Encryption Header Parameters registry.

   o  Added seriesInfo information to Internet Draft references.

   -07



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   o  Updated references.

   -06

   o  Changed "x5c" (X.509 Certificate Chain) representation from being
      a single string to being an array of strings, each containing a
      single base64 encoded DER certificate value, representing elements
      of the certificate chain.

   o  Applied changes made by the RFC Editor to RFC 6749's registry
      language to this specification.

   -05

   o  Added statement that "StringOrURI values are compared as case-
      sensitive strings with no transformations or canonicalizations
      applied".

   o  Indented artwork elements to better distinguish them from the body
      text.

   -04

   o  Completed JSON Security Considerations section, including
      considerations about rejecting input with duplicate member names.

   o  Completed security considerations on the use of a SHA-1 hash when
      computing "x5t" (x.509 certificate thumbprint) values.

   o  Refer to the registries as the primary sources of defined values
      and then secondarily reference the sections defining the initial
      contents of the registries.

   o  Normatively reference XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124]
      for its security considerations.

   o  Added this language to Registration Templates: "This name is case
      sensitive.  Names that match other registered names in a case
      insensitive manner SHOULD NOT be accepted."

   o  Reference draft-jones-jose-jws-json-serialization instead of
      draft-jones-json-web-signature-json-serialization.

   o  Described additional open issues.

   o  Applied editorial suggestions.

   -03



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   o  Added the "cty" (content type) header parameter for declaring type
      information about the secured content, as opposed to the "typ"
      (type) header parameter, which declares type information about
      this object.

   o  Added "Collision Resistant Namespace" to the terminology section.

   o  Reference ITU.X690.1994 for DER encoding.

   o  Added an example JWS using ECDSA P-521 SHA-512.  This has
      particular illustrative value because of the use of the 521 bit
      integers in the key and signature values.  This is also an example
      in which the payload is not a base64url encoded JSON object.

   o  Added an example "x5c" value.

   o  No longer say "the UTF-8 representation of the JWS Secured Input
      (which is the same as the ASCII representation)".  Just call it
      "the ASCII representation of the JWS Secured Input".

   o  Added Registration Template sections for defined registries.

   o  Added Registry Contents sections to populate registry values.

   o  Changed name of the JSON Web Signature and Encryption "typ" Values
      registry to be the JSON Web Signature and Encryption Type Values
      registry, since it is used for more than just values of the "typ"
      parameter.

   o  Moved registries JSON Web Signature and Encryption Header
      Parameters and JSON Web Signature and Encryption Type Values to
      the JWS specification.

   o  Numerous editorial improvements.

   -02

   o  Clarified that it is an error when a "kid" value is included and
      no matching key is found.

   o  Removed assumption that "kid" (key ID) can only refer to an
      asymmetric key.

   o  Clarified that JWSs with duplicate Header Parameter Names MUST be
      rejected.

   o  Clarified the relationship between "typ" header parameter values
      and MIME types.



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   o  Registered application/jws MIME type and "JWS" typ header
      parameter value.

   o  Simplified JWK terminology to get replace the "JWK Key Object" and
      "JWK Container Object" terms with simply "JSON Web Key (JWK)" and
      "JSON Web Key Set (JWK Set)" and to eliminate potential confusion
      between single keys and sets of keys.  As part of this change, the
      Header Parameter Name for a public key value was changed from
      "jpk" (JSON Public Key) to "jwk" (JSON Web Key).

   o  Added suggestion on defining additional header parameters such as
      "x5t#S256" in the future for certificate thumbprints using hash
      algorithms other than SHA-1.

   o  Specify RFC 2818 server identity validation, rather than RFC 6125
      (paralleling the same decision in the OAuth specs).

   o  Generalized language to refer to Message Authentication Codes
      (MACs) rather than Hash-based Message Authentication Codes (HMACs)
      unless in a context specific to HMAC algorithms.

   o  Reformatted to give each header parameter its own section heading.

   -01

   o  Moved definition of Plaintext JWSs (using "alg":"none") here from
      the JWT specification since this functionality is likely to be
      useful in more contexts that just for JWTs.

   o  Added "jpk" and "x5c" header parameters for including JWK public
      keys and X.509 certificate chains directly in the header.

   o  Clarified that this specification is defining the JWS Compact
      Serialization.  Referenced the new JWS-JS spec, which defines the
      JWS JSON Serialization.

   o  Added text "New header parameters should be introduced sparingly
      since an implementation that does not understand a parameter MUST
      reject the JWS".

   o  Clarified that the order of the creation and validation steps is
      not significant in cases where there are no dependencies between
      the inputs and outputs of the steps.

   o  Changed "no canonicalization is performed" to "no canonicalization
      need be performed".





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   o  Corrected the Magic Signatures reference.

   o  Made other editorial improvements suggested by JOSE working group
      participants.

   -00

   o  Created the initial IETF draft based upon
      draft-jones-json-web-signature-04 with no normative changes.

   o  Changed terminology to no longer call both digital signatures and
      HMACs "signatures".


Authors' Addresses

   Michael B. Jones
   Microsoft

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


   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com


   Nat Sakimura
   Nomura Research Institute

   Email: n-sakimura@nri.co.jp


















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