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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                              J. Bradley
Expires: January 5, 2015                                   Ping Identity
                                                             N. Sakimura
                                                                     NRI
                                                            July 4, 2014


                        JSON Web Signature (JWS)
                 draft-ietf-jose-json-web-signature-31

Abstract

   JSON Web Signature (JWS) represents 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 and
   an IANA registry defined by that 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 5, 2015.

Copyright Notice

   Copyright (c) 2014 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



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  JSON Web Signature (JWS) Overview  . . . . . . . . . . . . . .  6
     3.1.  JWS Compact Serialization Overview . . . . . . . . . . . .  7
     3.2.  JWS JSON Serialization Overview  . . . . . . . . . . . . .  7
     3.3.  Example JWS  . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  JOSE Header  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     4.1.  Registered Header Parameter Names  . . . . . . . . . . . . 10
       4.1.1.  "alg" (Algorithm) Header Parameter . . . . . . . . . . 10
       4.1.2.  "jku" (JWK Set URL) Header Parameter . . . . . . . . . 10
       4.1.3.  "jwk" (JSON Web Key) Header Parameter  . . . . . . . . 10
       4.1.4.  "kid" (Key ID) Header Parameter  . . . . . . . . . . . 11
       4.1.5.  "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 11
       4.1.6.  "x5c" (X.509 Certificate Chain) Header Parameter . . . 11
       4.1.7.  "x5t" (X.509 Certificate SHA-1 Thumbprint) Header
               Parameter  . . . . . . . . . . . . . . . . . . . . . . 12
       4.1.8.  "x5t#S256" (X.509 Certificate SHA-256 Thumbprint)
               Header Parameter . . . . . . . . . . . . . . . . . . . 12
       4.1.9.  "typ" (Type) Header Parameter  . . . . . . . . . . . . 12
       4.1.10. "cty" (Content Type) Header Parameter  . . . . . . . . 13
       4.1.11. "crit" (Critical) Header Parameter . . . . . . . . . . 13
     4.2.  Public Header Parameter Names  . . . . . . . . . . . . . . 14
     4.3.  Private Header Parameter Names . . . . . . . . . . . . . . 14
   5.  Producing and Consuming JWSs . . . . . . . . . . . . . . . . . 14
     5.1.  Message Signature or MAC Computation . . . . . . . . . . . 14
     5.2.  Message Signature or MAC Validation  . . . . . . . . . . . 15
     5.3.  String Comparison Rules  . . . . . . . . . . . . . . . . . 16
   6.  Key Identification . . . . . . . . . . . . . . . . . . . . . . 17
   7.  Serializations . . . . . . . . . . . . . . . . . . . . . . . . 17
     7.1.  JWS Compact Serialization  . . . . . . . . . . . . . . . . 18
     7.2.  JWS JSON Serialization . . . . . . . . . . . . . . . . . . 18
   8.  TLS Requirements . . . . . . . . . . . . . . . . . . . . . . . 19
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
     9.1.  JSON Web Signature and Encryption Header Parameters
           Registry . . . . . . . . . . . . . . . . . . . . . . . . . 21
       9.1.1.  Registration Template  . . . . . . . . . . . . . . . . 21
       9.1.2.  Initial Registry Contents  . . . . . . . . . . . . . . 22



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     9.2.  Media Type Registration  . . . . . . . . . . . . . . . . . 23
       9.2.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 23
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 24
     10.1. Key Entropy  . . . . . . . . . . . . . . . . . . . . . . . 25
     10.2. Chosen Plaintext Attacks . . . . . . . . . . . . . . . . . 25
     10.3. Timing Attacks . . . . . . . . . . . . . . . . . . . . . . 25
     10.4. Differences between Digital Signatures and MACs  . . . . . 25
     10.5. SHA-1 Certificate Thumbprints  . . . . . . . . . . . . . . 26
     10.6. JSON Security Considerations . . . . . . . . . . . . . . . 26
     10.7. Unicode Comparison Security Considerations . . . . . . . . 27
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 27
     11.2. Informative References . . . . . . . . . . . . . . . . . . 29
   Appendix A.  JWS Examples  . . . . . . . . . . . . . . . . . . . . 30
     A.1.  Example JWS using HMAC SHA-256 . . . . . . . . . . . . . . 30
       A.1.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 30
       A.1.2.  Validating . . . . . . . . . . . . . . . . . . . . . . 32
     A.2.  Example JWS using RSASSA-PKCS-v1_5 SHA-256 . . . . . . . . 32
       A.2.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 33
       A.2.2.  Validating . . . . . . . . . . . . . . . . . . . . . . 35
     A.3.  Example JWS using ECDSA P-256 SHA-256  . . . . . . . . . . 35
       A.3.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 35
       A.3.2.  Validating . . . . . . . . . . . . . . . . . . . . . . 37
     A.4.  Example JWS using ECDSA P-521 SHA-512  . . . . . . . . . . 38
       A.4.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 38
       A.4.2.  Validating . . . . . . . . . . . . . . . . . . . . . . 40
     A.5.  Example Plaintext JWS  . . . . . . . . . . . . . . . . . . 40
     A.6.  Example JWS Using JWS JSON Serialization . . . . . . . . . 41
       A.6.1.  JWS Per-Signature Protected Headers  . . . . . . . . . 41
       A.6.2.  JWS Per-Signature Unprotected Headers  . . . . . . . . 42
       A.6.3.  Complete JOSE Header Values  . . . . . . . . . . . . . 42
       A.6.4.  Complete JWS JSON Serialization Representation . . . . 42
   Appendix B.  "x5c" (X.509 Certificate Chain) Example . . . . . . . 43
   Appendix C.  Notes on implementing base64url encoding without
                padding . . . . . . . . . . . . . . . . . . . . . . . 45
   Appendix D.  Notes on Key Selection  . . . . . . . . . . . . . . . 46
   Appendix E.  Negative Test Case for "crit" Header Parameter  . . . 47
   Appendix F.  Detached Content  . . . . . . . . . . . . . . . . . . 48
   Appendix G.  Acknowledgements  . . . . . . . . . . . . . . . . . . 48
   Appendix H.  Document History  . . . . . . . . . . . . . . . . . . 49
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 58










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1.  Introduction

   JSON Web Signature (JWS) represents content secured with digital
   signatures or Message Authentication Codes (MACs) using JavaScript
   Object Notation (JSON) [RFC7159] based data structures.  The JWS
   cryptographic mechanisms provide integrity protection for an
   arbitrary sequence of octets.

   Two closely related serializations 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 and an IANA registry defined by that
   specification.  Related encryption capabilities are described in the
   separate JSON Web Encryption (JWE) [JWE] specification.

   Names defined by this specification are short because a core goal is
   for the resulting representations to be compact.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in Key
   words for use in RFCs to Indicate Requirement Levels [RFC2119].  If
   these words are used without being spelled in uppercase then they are
   to be interpreted with their normal natural language meanings.

   BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per
   Section 2.

   UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation
   of STRING.

   ASCII(STRING) denotes the octets of the ASCII [USASCII]
   representation of STRING.

   The concatenation of two values A and B is denoted as A || B.







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2.  Terminology

   These terms are defined by this specification:

   JSON Web Signature (JWS)
      A data structure representing a digitally signed or MACed message.

   JOSE Header
      JSON object containing the parameters describing the cryptographic
      operations and parameters employed.  The members of the JOSE
      Header 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.

   JWS Signature
      Digital signature or MAC over the JWS Protected Header and the JWS
      Payload.

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

   JWS Protected Header
      JSON object that contains the Header Parameters that are integrity
      protected by the JWS Signature digital signature or MAC operation.
      For the JWS Compact Serialization, this comprises the entire JOSE
      Header.  For the JWS JSON Serialization, this is one component of
      the JOSE Header.

   JWS Unprotected Header
      JSON object that contains the Header Parameters that are not
      integrity protected.  This can only be present when using the JWS
      JSON Serialization.

   Base64url Encoding
      Base64 encoding using the URL- and filename-safe character set
      defined in Section 5 of RFC 4648 [RFC4648], with all trailing '='
      characters omitted (as permitted by Section 3.2) and without the
      inclusion of any line breaks, white space, or other additional
      characters.  (See Appendix C for notes on implementing base64url
      encoding without padding.)

   JWS Signing Input
      The input to the digital signature or MAC computation.  Its value
      is ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' ||
      BASE64URL(JWS Payload)).




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   JWS Compact Serialization
      A representation of the JWS as a compact, URL-safe string.

   JWS JSON Serialization
      A representation of the JWS as a JSON object.  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 optimized for compactness nor URL-
      safe.

   Plaintext JWS
      A JWS object that provides no integrity protection.

   Collision-Resistant Name
      A name in a namespace that enables names to be allocated in a
      manner such that they are highly unlikely to collide with other
      names.  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.

   These terms defined by the JSON Web Encryption (JWE) [JWE]
   specification are incorporated into this specification: "JSON Web
   Encryption (JWE)" and "JWE Compact Serialization".


3.  JSON Web Signature (JWS) Overview

   JWS represents digitally signed or MACed content using JSON data
   structures and base64url encoding.  A JWS represents these logical
   values:

   JOSE Header
      JSON object containing the parameters describing the cryptographic
      operations and parameters employed.  For a JWS object, the JOSE
      Header members are the union of the members of the JWS Protected
      Header and the JWS Unprotected Header, as described below.




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

   JWS Signature
      Digital signature or MAC over the JWS Protected Header and the JWS
      Payload.

   For a JWS object, the JOSE Header represents the combination of these
   values:

   JWS Protected Header
      JSON object that contains the Header Parameters that are integrity
      protected by the JWS Signature digital signature or MAC operation.

   JWS Unprotected Header
      JSON object that contains the Header Parameters that are not
      integrity protected.

   This document defines two serializations for JWS objects: a compact,
   URL-safe serialization called the JWS Compact Serialization and a
   JSON serialization called the JWS JSON Serialization.  In both
   serializations, the JWS Protected Header, JWS Payload, and JWS
   Signature are base64url encoded for transmission, since JSON lacks a
   way to directly represent octet sequences.

3.1.  JWS Compact Serialization Overview

   In the JWS Compact Serialization, no JWS Unprotected Header is used.
   In this case, the JOSE Header and the JWS Protected Header are the
   same.

   In the JWS Compact Serialization, a JWS object is represented as the
   combination of these three string values,
      BASE64URL(UTF8(JWS Protected Header)),
      BASE64URL(JWS Payload), and
      BASE64URL(JWS Signature),
   concatenated in that order, with the three strings being separated by
   two period ('.') characters.

3.2.  JWS JSON Serialization Overview

   In the JWS JSON Serialization, one or both of the JWS Protected
   Header and JWS Unprotected Header MUST be present.  In this case, the
   members of the JOSE Header are the combination of the members of the
   JWS Protected Header and the JWS Unprotected Header values that are
   present.




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   In the JWS JSON Serialization, a JWS object is represented as the
   combination of these four values,
      BASE64URL(UTF8(JWS Protected Header)),
      JWS Unprotected Header,
      BASE64URL(JWS Payload), and
      BASE64URL(JWS Signature),
   with the three base64url encoding result strings and the JWS
   Unprotected Header value being represented as members within a JSON
   object.  The inclusion of some of these values is OPTIONAL.  The JWS
   JSON Serialization can also represent multiple signature and/or MAC
   values, rather than just one.  See Section 7.2 for more information
   about the JWS JSON Serialization.

3.3.  Example JWS

   This section provides an example of a JWS.  Its computation is
   described in more detail in Appendix A.1, including specifying the
   exact octet sequences representing the JSON values used and the key
   value used.

   The following example JWS Protected Header declares that the encoded
   object is a JSON Web Token (JWT) [JWT] and the JWS Protected Header
   and the JWS Payload are secured using the HMAC SHA-256 [RFC2104, SHS]
   algorithm:

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

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value:

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

   The UTF-8 representation of following JSON object is used as the 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}

   Encoding this JWS Payload as BASE64URL(JWS Payload) gives this value
   (with line breaks for display purposes only):

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   Computing the HMAC of the JWS Signing Input ASCII(BASE64URL(UTF8(JWS



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   Protected Header)) || '.' || BASE64URL(JWS Payload)) with the HMAC
   SHA-256 algorithm using the key specified in Appendix A.1 and
   base64url encoding the result yields this BASE64URL(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

   See Appendix A for additional examples.


4.  JOSE Header

   For a JWS object, the members of the JSON object(s) representing the
   JOSE Header describe the digital signature or MAC applied to the JWS
   Protected Header and the JWS Payload and optionally additional
   properties of the JWS.  The Header Parameter names within the JOSE
   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 4.1.11, all Header Parameters not defined by this
   specification MUST be ignored when not understood.

   There are three classes of Header Parameter names: Registered Header
   Parameter names, Public Header Parameter names, and Private Header
   Parameter names.






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4.1.  Registered Header Parameter Names

   The following Header Parameter names for use in JWS objects are
   registered in the IANA JSON Web Signature and Encryption Header
   Parameters registry defined in Section 9.1, with meanings as defined
   below.

   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 the cryptographic
   algorithm used to secure the JWS.  The signature, MAC, or plaintext
   value is not valid 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 defined in [JWA] or be a
   value that contains a Collision-Resistant Name.  The "alg" value is a
   case-sensitive string containing a StringOrURI value.  This Header
   Parameter MUST be present and MUST be understood and processed by
   implementations.

   A list of defined "alg" values for this use can be found in the IANA
   JSON Web Signature and Encryption Algorithms registry defined in
   [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 6 of RFC 6125 [RFC6125].  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



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   OPTIONAL.

4.1.4.  "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.  The structure 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 is used to match a JWK "kid"
   parameter value.

4.1.5.  "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 6 of RFC 6125 [RFC6125].
   Use of this Header Parameter is OPTIONAL.

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 validate
   the certificate chain according to RFC 5280 [RFC5280] and reject the
   signature if any validation failure occurs.  Use of this Header
   Parameter is OPTIONAL.

   See Appendix B for an example "x5c" value.



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4.1.7.  "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter

   The "x5t" (X.509 Certificate SHA-1 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.

4.1.8.  "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header
        Parameter

   The "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header
   Parameter is a base64url encoded SHA-256 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.

4.1.9.  "typ" (Type) Header Parameter

   The "typ" (type) Header Parameter is used by JWS applications to
   declare the MIME Media Type [IANA.MediaTypes] of this complete JWS
   object.  This is intended for use by the application when more than
   one kind of object could be present in an application data structure
   that can contain a JWS object; the application can use this value to
   disambiguate among the different kinds of objects that might be
   present.  It will typically not be used by applications when the kind
   of object is already known.  This parameter is ignored by JWS
   implementations; any processing of this parameter is performed by the
   JWS application.  Use of this Header Parameter is OPTIONAL.

   Per RFC 2045 [RFC2045], all media type values, subtype values, and
   parameter names are case-insensitive.  However, parameter values are
   case-sensitive unless otherwise specified for the specific parameter.

   To keep messages compact in common situations, it is RECOMMENDED that
   senders omit an "application/" prefix of a media type value in a
   "typ" Header Parameter when no other '/' appears in the media type
   value.  A recipient using the media type value MUST treat it as if
   "application/" were prepended to any "typ" value not containing a
   '/'.  For instance, a "typ" value of "example" SHOULD be used to
   represent the "application/example" media type; whereas, the media
   type "application/example;part="1/2"" cannot be shortened to
   "example;part="1/2"".

   The "typ" value "JOSE" can 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 "typ" value "JOSE+JSON" can be
   used by applications to indicate that this object is a JWS or JWE



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   using the JWS JSON Serialization or the JWE JSON Serialization.
   Other type values can also be used by applications.

4.1.10.  "cty" (Content Type) Header Parameter

   The "cty" (content type) Header Parameter is used by JWS applications
   to declare the MIME Media Type [IANA.MediaTypes] of the secured
   content (the payload).  This is intended for use by the application
   when more than one kind of object could be present in the JWS
   payload; the application can use this value to disambiguate among the
   different kinds of objects that might be present.  It will typically
   not be used by applications when the kind of object is already known.
   This parameter is ignored by JWS implementations; any processing of
   this parameter is performed by the JWS application.  Use of this
   Header Parameter is OPTIONAL.

   Per RFC 2045 [RFC2045], all media type values, subtype values, and
   parameter names are case-insensitive.  However, parameter values are
   case-sensitive unless otherwise specified for the specific parameter.

   To keep messages compact in common situations, it is RECOMMENDED that
   senders omit an "application/" prefix of a media type value in a
   "cty" Header Parameter when no other '/' appears in the media type
   value.  A recipient using the media type value MUST treat it as if
   "application/" were prepended to any "cty" value not containing a
   '/'.  For instance, a "cty" value of "example" SHOULD be used to
   represent the "application/example" media type; whereas, the media
   type "application/example;part="1/2"" cannot be shortened to
   "example;part="1/2"".

4.1.11.  "crit" (Critical) Header Parameter

   The "crit" (critical) Header Parameter indicates that extensions to
   the initial RFC versions of [[ this specification ]] and [JWA] are
   being used that MUST be understood and processed.  Its value is an
   array listing the Header Parameter names present in the JOSE Header
   that use those extensions.  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 the initial RFC versions of [[ this specification ]] or
   [JWA] for use with JWS, duplicate names, or names that do not occur
   as Header Parameter names within the JOSE 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 the initial RFC versions of [[ this
   specification ]] or [JWA] for use with JWS, or any other constraints
   on its use are violated.  This Header Parameter MUST be integrity
   protected, and therefore MUST occur only within the JWS Protected



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   Header, when used.  Use of this Header Parameter is OPTIONAL.  This
   Header Parameter MUST be understood and processed 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 defined in Section 9.1 or be a
   Public Name: a value that contains a Collision-Resistant Name.  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 Registered Header
   Parameter names Section 4.1 or Public Header Parameter names
   Section 4.2.  Unlike Public Header Parameter names, Private Header
   Parameter names are subject to collision and should be used with
   caution.


5.  Producing and Consuming JWSs

5.1.  Message Signature or MAC Computation

   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.  Compute the encoded payload value BASE64URL(JWS Payload).
   3.  Create the JSON object(s) containing the desired set of Header
       Parameters, which together comprise the JOSE Header: the JWS
       Protected Header, and if the JWS JSON Serialization is being
       used, the JWS Unprotected Header.



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   4.  Compute the encoded header value BASE64URL(UTF8(JWS Protected
       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 this value be the empty
       string.
   5.  Compute the JWS Signature in the manner defined for the
       particular algorithm being used over the JWS Signing Input
       ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' ||
       BASE64URL(JWS Payload)).  The "alg" (algorithm) Header Parameter
       MUST be present in the JOSE Header, with the algorithm value
       accurately representing the algorithm used to construct the JWS
       Signature.
   6.  Compute the encoded signature value BASE64URL(JWS Signature).
   7.  These three encoded values are 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
       (steps 3-7) for each digital signature or MAC operation being
       performed.
   9.  Create the desired serialized output.  The JWS Compact
       Serialization of this result is BASE64URL(UTF8(JWS Protected
       Header)) || '.' || BASE64URL(JWS Payload) || '.' || BASE64URL(JWS
       Signature).  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 signature or MAC cannot be
   validated.

   It is an application decision which signatures, MACs, or plaintext
   values must successfully validate for the JWS to be accepted.  In
   some cases, all must successfully validate or the JWS will be
   rejected.  In other cases, only a specific signature, MAC, or
   plaintext value needs to be successfully validated.  However, in all
   cases, at least one signature, MAC, or plaintext value MUST
   successfully validate or the JWS MUST be rejected.

   1.   Parse the JWS representation to extract the serialized values
        for the components of the JWS.  When using the JWS Compact
        Serialization, these components are the base64url encoded
        representations of the JWS Protected Header, the JWS Payload,
        and the JWS Signature, and when using the JWS JSON
        Serialization, these components also include the unencoded JWS
        Unprotected Header value.  When using the JWS Compact
        Serialization, the JWS Protected Header, the JWS Payload, and



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        the JWS Signature are represented as base64url encoded values in
        that order, separated by two period ('.') characters.  The JWS
        JSON Serialization is described in Section 7.2.
   2.   The encoded representation of the JWS Protected Header MUST be
        successfully base64url decoded following the restriction that no
        padding characters have been used.
   3.   The resulting octet sequence MUST be a UTF-8 encoded
        representation of a completely valid JSON object conforming to
        RFC 7159 [RFC7159], which is the JWS Protected Header.
   4.   If using the JWS Compact Serialization, let the JOSE Header be
        the JWS Protected Header.  Otherwise, when using the JWS JSON
        Serialization, let the JOSE Header be the union of the members
        of the corresponding JWS Protected Header and JWS Unprotected
        Header, all of which must be completely valid JSON objects.
   5.   The resulting JOSE 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 object values that together
        comprise the JOSE Header.
   6.   Verify that the implementation understands and can process all
        fields that it is required to support, whether required by this
        specification, by the algorithm being used, or by the "crit"
        Header Parameter value, and that the values of those parameters
        are also understood and supported.
   7.   The encoded representation of the JWS Payload MUST be
        successfully base64url decoded following the restriction that no
        padding characters have been used.
   8.   The encoded representation of the JWS Signature MUST be
        successfully base64url decoded following the restriction that no
        padding characters have been used.
   9.   The JWS Signature MUST be successfully validated against the JWS
        Signing Input ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.'
        || BASE64URL(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.
   10.  If the JWS JSON Serialization is being used, repeat this process
        (steps 4-9) for each digital signature or MAC value contained in
        the representation.

5.3.  String Comparison Rules

   Processing a JWS inevitably requires comparing known strings to
   members and values in a JSON object.  For example, in checking what
   the algorithm is, the Unicode string "alg" will be checked against
   the member names in the JOSE Header to see if there is a matching
   Header Parameter name.  The same process is then used to determine if
   the value of the "alg" Header Parameter represents a supported



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   algorithm.

   Since the only string comparison operations that are performed are
   equality and inequality, the same rules can be used for comparing
   both member names and member values against known strings.  The JSON
   rules for doing member name comparison are described in Section 8.3
   of RFC 7159 [RFC7159].

   Also, see the JSON security considerations in Section 10.6 and the
   Unicode security considerations in Section 10.7.


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", "kid", "x5u", "x5c", "x5t", and "x5t#S256"
   can be used to identify the key used.  These Header Parameters MUST
   be integrity protected if the information that they convey is to be
   utilized in a trust decision.

   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.  Validation of
   the signature or MAC fails when the algorithm used requires a key
   (which is true of all algorithms except for "none") and the key used
   cannot be determined.

   The means of exchanging any shared symmetric keys used is outside the
   scope of this specification.

   Also, see Appendix D for notes on possible key selection algorithms.


7.  Serializations

   JWS objects use one of two serializations, the JWS Compact
   Serialization or the JWS JSON Serialization.  Applications using this
   specification need to specify what serialization and serialization
   features are used for that application.  For instance, applications
   might specify that only the JWS JSON Serialization is used, that only
   JWS JSON Serialization support for a single signature or MAC value is
   used, or that support for multiple signatures and/or MAC values is
   used.  JWS implementations only need to implement the features needed
   for the applications they are designed to support.



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7.1.  JWS Compact Serialization

   The JWS Compact Serialization represents digitally signed or MACed
   content as a compact URL-safe string.  This string is
   BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS
   Payload) || '.' || BASE64URL(JWS Signature).  Only one signature/MAC
   is supported by the JWS Compact Serialization and it provides no
   syntax to represent a JWS Unprotected Header value.

7.2.  JWS JSON Serialization

   The JWS JSON Serialization represents digitally signed or MACed
   content as a JSON object.  Content using the JWS JSON Serialization
   can be secured with more than one digital signature and/or MAC
   operation.  This representation is neither optimized for compactness
   nor URL-safe.

   The following members are defined for use in top-level JSON objects
   used for the JWS JSON Serialization:
   payload
      The "payload" member MUST be present and contain the value
      BASE64URL(JWS Payload).
   signatures
      The "signatures" member value MUST be an array of JSON objects.
      Each object represents a signature or MAC over the JWS Payload and
      the JWS Protected Header.

   The following members are defined for use in the JSON objects that
   are elements of the "signatures" array:
   protected
      The "protected" member MUST be present and contain the value
      BASE64URL(UTF8(JWS Protected Header)) when the JWS Protected
      Header value is non-empty; otherwise, it MUST be absent.  These
      Header Parameter values are integrity protected.
   header
      The "header" member MUST be present and contain the value JWS
      Unprotected Header when the JWS Unprotected Header value is non-
      empty; otherwise, it MUST be absent.  This value is represented as
      an unencoded JSON object, rather than as a string.  These Header
      Parameter values are not integrity protected.
   signature
      The "signature" member MUST be present and contain the value
      BASE64URL(JWS Signature).

   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.




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   Additional members can be present in both the JSON objects defined
   above; if not understood by implementations encountering them, they
   MUST be ignored.

   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 JWS Protected
   Header represented in the "protected" member of the signature/MAC's
   array element, and (2) the JWS Unprotected Header in the "header"
   member of the signature/MAC's array element.  The union of these sets
   of Header Parameters comprises the JOSE Header.  The Header Parameter
   names in the two locations MUST be disjoint.

   Each JWS Signature value is computed using the parameters of the
   corresponding JOSE Header value in the same manner as for the JWS
   Compact Serialization.  This has the desirable property that each JWS
   Signature value represented in the "signatures" array is identical to
   the value that would have been computed for the same parameter in the
   JWS Compact Serialization, provided that the JWS Protected Header
   value for that signature/MAC computation (which represents the
   integrity-protected Header Parameter values) matches that used in the
   JWS Compact Serialization.

   In summary, 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>"}]
     }

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


8.  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



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   [RFC5246] is the most recent version.

   To protect against information disclosure and tampering,
   confidentiality protection MUST be applied using TLS with a
   ciphersuite that provides confidentiality and integrity protection.
   See current publications by the IETF TLS working group, including RFC
   6176 [RFC6176], for guidance on the ciphersuites currently considered
   to be appropriate for use.

   Whenever TLS is used, the identity of the service provider encoded in
   the TLS server certificate MUST be verified using the procedures
   described in Section 6 of RFC 6125 [RFC6125].


9.  IANA Considerations

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

   Values are registered on a Specification Required [RFC5226] basis
   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 the 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.  Registration requests that are undetermined for a period
   longer than 21 days can be brought to the IESG's attention (using the
   iesg@iesg.org mailing list) for resolution.

   Criteria that should be applied by the Designated Expert(s) includes
   determining whether the proposed registration duplicates existing
   functionality, determining whether it is likely to be of general
   applicability or whether it is useful only for a single application,
   and whether the registration makes sense.

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



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   list.

   It is suggested that multiple Designated Experts be appointed who are
   able to represent the perspectives of different applications using
   this specification, in order to enable broadly-informed review of
   registration decisions.  In cases where a registration decision could
   be perceived as creating a conflict of interest for a particular
   Expert, that Expert should defer to the judgment of the other
   Expert(s).

9.1.  JSON Web Signature and Encryption Header Parameters Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption Header Parameters registry for Header Parameter names.
   The registry records the Header Parameter name and a reference to the
   specification that defines it.  The same Header Parameter name can 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.

9.1.1.  Registration Template

   Header Parameter Name:
      The name requested (e.g., "example").  Because a core goal of this
      specification is for the resulting representations to be compact,
      it is RECOMMENDED that the name be short -- not to exceed 8
      characters without a compelling reason to do so.  This name is
      case-sensitive.  Names may not match other registered names in a
      case-insensitive manner unless the Designated Expert(s) state that
      there is a compelling reason to allow an exception in this
      particular case.
   Header Parameter Description:
      Brief description of the Header Parameter (e.g., "Example
      description").
   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 "IESG".  For others, give the name
      of the responsible party.  Other details (e.g., postal address,
      email address, home page URI) may also be included.
   Specification Document(s):
      Reference to the document(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.




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9.1.2.  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 Description: Algorithm
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.1 of [[ this document ]]

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

   o  Header Parameter Name: "jwk"
   o  Header Parameter Description: JSON Web Key
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification document(s): Section 4.1.3 of [[ this document ]]

   o  Header Parameter Name: "kid"
   o  Header Parameter Description: Key ID
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.4 of [[ this document ]]

   o  Header Parameter Name: "x5u"
   o  Header Parameter Description: X.509 URL
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.5 of [[ this document ]]

   o  Header Parameter Name: "x5c"
   o  Header Parameter Description: X.509 Certificate Chain
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.6 of [[ this document ]]

   o  Header Parameter Name: "x5t"
   o  Header Parameter Description: X.509 Certificate SHA-1 Thumbprint
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.7 of [[ this document ]]





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   o  Header Parameter Name: "x5t#S256"
   o  Header Parameter Description: X.509 Certificate SHA-256 Thumbprint
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

   o  Header Parameter Name: "typ"
   o  Header Parameter Description: Type
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.9 of [[ this document ]]

   o  Header Parameter Name: "cty"
   o  Header Parameter Description: Content Type
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.10 of [[ this document ]]

   o  Header Parameter Name: "crit"
   o  Header Parameter Description: Critical
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.11 of [[ this document ]]

9.2.  Media Type Registration

9.2.1.  Registry Contents

   This specification registers the "application/jose" Media Type
   [RFC2046] in the MIME Media Types registry [IANA.MediaTypes], 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 Types
   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.

   o  Type name: application
   o  Subtype name: jose
   o  Required parameters: n/a
   o  Optional parameters: n/a
   o  Encoding considerations: 8bit; 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 ]]





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   o  Interoperability considerations: n/a
   o  Published specification: [[ this document ]]
   o  Applications that use this media type: OpenID Connect, Mozilla
      Persona, Salesforce, Google, Android, Windows Azure, Xbox One, and
      numerous others that use 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: IESG

   o  Type name: application
   o  Subtype name: jose+json
   o  Required parameters: n/a
   o  Optional parameters: n/a
   o  Encoding considerations: 8bit; 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: IESG


10.  Security Considerations

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

   All the security considerations in XML DSIG 2.0
   [W3C.NOTE-xmldsig-core2-20130411], also apply to this specification,



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   other than those that are XML specific.  Likewise, many of the best
   practices documented in XML Signature Best Practices
   [W3C.NOTE-xmldsig-bestpractices-20130411] also apply to this
   specification, other than those that are XML specific.

10.1.  Key Entropy

   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.

10.2.  Chosen Plaintext Attacks

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

10.3.  Timing Attacks

   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.

10.4.  Differences between Digital Signatures and MACs

   While MACs and digital signatures can both be used for integrity
   checking, there are some significant differences between the security
   properties that each of them provides.  These need to be taken into
   consideration when designing protocols and selecting the algorithms
   to be used in protocols.

   Both signatures and MACs provide for integrity checking -- verifying
   that the message has not been modified since the integrity value was
   computed.  However, MACs provide for origination identification only
   under specific circumstances.  It can normally be assumed that a
   private key used for a signature is only in the hands of a single
   entity (although perhaps a distributed entity, in the case of
   replicated servers); however, a MAC key needs to be in the hands of
   all the entities that use it for integrity computation and checking.
   This means that origination can only be determined if a MAC key is
   known only to two entities and the receiver knows that it did not
   create the message.  MAC validation cannot be used to prove
   origination to a third party.




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10.5.  SHA-1 Certificate Thumbprints

   A SHA-1 hash is used when computing "x5t" (X.509 Certificate SHA-1
   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.

   Alternatively, the "x5t#S256" (X.509 Certificate SHA-256 Thumbprint)
   Header Parameter could be used instead of "x5t".  However, at the
   time of this writing, no development platform is known to support
   SHA-256 certificate thumbprints.

10.6.  JSON Security Considerations

   Strict JSON [RFC7159] 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.  In particular, any JSON inputs not
   conforming to the JSON-text syntax defined in RFC 7159 input MUST be
   rejected in their entirety.

   Section 4 of the JSON Data Interchange Format specification [RFC7159]
   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 4 "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-text object followed by
   the extra characters "ABCD".  Such input MUST be rejected in its
   entirety.





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10.7.  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 Section 8.3
   of RFC 7159 [RFC7159]).  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
   exercising limitations present in the underlying JSON implementation,
   then input containing them MUST be rejected.


11.  References

11.1.  Normative References

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

   [IANA.MediaTypes]
              Internet Assigned Numbers Authority (IANA), "MIME Media
              Types", 2005.

   [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 2014.

   [JWK]      Jones, M., "JSON Web Key (JWK)",
              draft-ietf-jose-json-web-key (work in progress),
              July 2014.

   [RFC1421]  Linn, J., "Privacy Enhancement for Internet Electronic



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              Mail: Part I: Message Encryption and Authentication
              Procedures", RFC 1421, February 1993.

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [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.

   [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.

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

   [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.

   [RFC6176]  Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer
              (SSL) Version 2.0", RFC 6176, March 2011.

   [RFC7159]  Bray, T., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, March 2014.

   [USASCII]  American National Standards Institute, "Coded Character
              Set -- 7-bit American Standard Code for Information



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              Interchange", ANSI X3.4, 1986.

11.2.  Informative References

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

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

   [JWE]      Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              draft-ietf-jose-json-web-encryption (work in progress),
              July 2014.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", draft-ietf-oauth-json-web-token (work in
              progress), July 2014.

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

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              February 1997.

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

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

   [SHS]      National Institute of Standards and Technology, "Secure
              Hash Standard (SHS)", FIPS PUB 180-3, October 2008.

   [W3C.NOTE-xmldsig-bestpractices-20130411]
              Hirsch, F. and P. Datta, "XML Signature Best Practices",
              World Wide Web Consortium Note NOTE-xmldsig-bestpractices-
              20130411, April 2013, <http://www.w3.org/TR/2013/
              NOTE-xmldsig-bestpractices-20130411/>.

   [W3C.NOTE-xmldsig-core2-20130411]
              Eastlake, D., Reagle, J., Solo, D., Hirsch, F., Roessler,
              T., Yiu, K., Datta, P., and S. Cantor, "XML Signature
              Syntax and Processing Version 2.0", World Wide Web
              Consortium Note NOTE-xmldsig-core2-20130411, April 2013,



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              <http://www.w3.org/TR/2013/NOTE-xmldsig-core2-20130411/>.


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.

A.1.  Example JWS using HMAC SHA-256

A.1.1.  Encoding

   The following example JWS Protected 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"}

   To remove potential ambiguities in the representation of the JSON
   object above, the actual octet sequence representing UTF8(JWS
   Protected Header) used in this example is also included below.  (Note
   that ambiguities can arise due to differing platform representations
   of line breaks (CRLF versus LF), differing spacing at the beginning
   and ends of lines, whether the last line has a terminating line break
   or not, and other causes.  In the representation used in this
   example, the first line has no leading or trailing spaces, a CRLF
   line break (13, 10) occurs between the first and second lines, the
   second line has one leading space (32) and no trailing spaces, and
   the last line does not have a terminating line break.)  The octets
   representing UTF8(JWS Protected Header) in this example (using JSON
   array notation) are:

   [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]

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this 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.)





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

   The following octet sequence, which is the UTF-8 representation used
   in this example for 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]

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value (with line breaks for display purposes
   only):

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
   BASE64URL(JWS Payload) gives this string (with line breaks for
   display purposes only):

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The resulting JWS Signing Input value, which is the ASCII
   representation of above string, is the following octet sequence
   (using JSON array notation):

   [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
   within values for display purposes only):





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

   Running the HMAC SHA-256 algorithm on the JWS Signing Input with this
   key yields this JWS Signature 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]

   Encoding this JWS Signature as BASE64URL(JWS Signature) gives this
   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

A.1.2.  Validating

   Since the "alg" Header Parameter is "HS256", we validate the HMAC
   SHA-256 value contained in the JWS Signature.

   To validate the HMAC value, we repeat the previous process of using
   the correct key and the JWS Signing Input (which is the initial
   substring of the JWS Compact Serialization representation up until
   but not including the second period character) as input to the HMAC
   SHA-256 function and then taking the output and determining if it
   matches the JWS Signature (which is base64url decoded from the value
   encoded in the JWS representation).  If it matches exactly, the HMAC
   has been validated.

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







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A.2.1.  Encoding

   The JWS Protected 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
   Protected Header used is:

     {"alg":"RS256"}

   The octets representing UTF8(JWS Protected Header) in this example
   (using JSON array notation) are:

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

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value:

     eyJhbGciOiJSUzI1NiJ9

   The JWS Payload used in this example, which follows, is the same as
   in the previous example.  Since the BASE64URL(JWS Payload) value will
   therefore be the same, its computation is not repeated here.

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

   Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
   BASE64URL(JWS Payload) gives this string (with line breaks for
   display purposes only):

     eyJhbGciOiJSUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The resulting JWS Signing Input value, which is the ASCII
   representation of above string, 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,



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   99, 110, 86, 108, 102, 81]

   This example uses the RSA key represented in JSON Web Key [JWK]
   format below (with line breaks within values 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"
     }

   The RSA private key is then passed to the RSA signing function, which
   also takes the hash type, SHA-256, and 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]

   Encoding the signature as BASE64URL(JWS Signature) produces this
   value (with line breaks for display purposes only):



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     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):

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

A.2.2.  Validating

   Since the "alg" Header Parameter is "RS256", we validate the RSASSA-
   PKCS-v1_5 SHA-256 digital signature contained in the JWS Signature.

   Validating the JWS Signature is a bit different from the previous
   example.  We pass the public key (n, e), the JWS Signature (which is
   base64url decoded from the value encoded in the JWS representation),
   and the JWS Signing Input (which is the initial substring of the JWS
   Compact Serialization representation up until but not including the
   second period character) 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 Protected Header for this example differs from the previous
   example because a different algorithm is being used.  The JWS
   Protected Header used is:

     {"alg":"ES256"}

   The octets representing UTF8(JWS Protected Header) in this example



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   (using JSON array notation) are:

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

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value:

     eyJhbGciOiJFUzI1NiJ9

   The JWS Payload used in this example, which follows, is the same as
   in the previous examples.  Since the BASE64URL(JWS Payload) value
   will therefore be the same, its computation is not repeated here.

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

   Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
   BASE64URL(JWS Payload) gives this string (with line breaks for
   display purposes only):

     eyJhbGciOiJFUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The resulting JWS Signing Input value, which is the ASCII
   representation of above string, 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"
     }




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   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 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      | [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]                    |
   +--------+----------------------------------------------------------+

   The JWS Signature is the value R || S. Encoding the signature as
   BASE64URL(JWS Signature) produces this value (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.  Validating

   Since the "alg" Header Parameter is "ES256", we validate the ECDSA
   P-256 SHA-256 digital signature contained in the JWS Signature.

   Validating the JWS Signature is a bit different from the previous
   examples.  We need to split the 64 member octet sequence of the JWS
   Signature (which is base64url decoded from the value encoded in the
   JWS representation) into two 32 octet sequences, the first



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   representing R and the second S. We then pass the public key (x, y),
   the signature (R, S), and the JWS Signing Input (which is the initial
   substring of the JWS Compact Serialization representation up until
   but not including the second period character) to an ECDSA signature
   verifier that has been configured to use the P-256 curve with the
   SHA-256 hash function.

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

A.4.1.  Encoding

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

     {"alg":"ES512"}

   The octets representing UTF8(JWS Protected Header) in this example
   (using JSON array notation) are:

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

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this 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]

   Encoding this JWS Payload as BASE64URL(JWS Payload) gives this value:

     UGF5bG9hZA

   Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
   BASE64URL(JWS Payload) gives this string:

     eyJhbGciOiJFUzUxMiJ9.UGF5bG9hZA

   The resulting JWS Signing Input value, which is the ASCII
   representation of above string, 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



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   [JWK] format below (with line breaks within values 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 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]                        |
   | 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]                                  |
   +--------+----------------------------------------------------------+

   The JWS Signature is the value R || S. Encoding the signature as
   BASE64URL(JWS Signature) produces this value (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



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   representation using the JWS Compact Serialization (with line breaks
   for display purposes only):

     eyJhbGciOiJFUzUxMiJ9
     .
     UGF5bG9hZA
     .
     AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq
     wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp
     EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn

A.4.2.  Validating

   Since the "alg" Header Parameter is "ES512", we validate the ECDSA
   P-521 SHA-512 digital signature contained in the JWS Signature.

   Validating this JWS Signature is very similar to the previous
   example.  We need to split the 132 member octet sequence of the JWS
   Signature into two 66 octet sequences, the first representing R and
   the second S. We then pass the public key (x, y), the signature (R,
   S), and 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.

A.5.  Example Plaintext JWS

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

     {"alg":"none"}

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value:

     eyJhbGciOiJub25lIn0

   The JWS Payload used in this example, which follows, is the same as
   in the previous examples.  Since the BASE64URL(JWS Payload) value
   will therefore be the same, its computation is not repeated here.

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

   The JWS Signature is the empty octet string and BASE64URL(JWS
   Signature) is the empty string.

   Concatenating these parts in the order Header.Payload.Signature with



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   period ('.') characters between the parts yields this complete JWS
   (with line breaks for display purposes only):

     eyJhbGciOiJub25lIn0
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .

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 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"}

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value:

     eyJhbGciOiJSUzI1NiJ9

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

     {"alg":"ES256"}

   Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
   Header)) gives this value:



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     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

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

A.6.3.  Complete JOSE Header Values

   Combining the protected and unprotected header values supplied, the
   JOSE 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 within values for display purposes
   only):



















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     {"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
   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



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       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
       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



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       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.

     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 '='



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   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.  Notes on Key Selection

   This appendix describes a set of possible algorithms for selecting
   the key to be used to validate the digital signature or MAC of a JWS
   object or for selecting the key to be used to decrypt a JWE object.
   This guidance describes a family of possible algorithms, rather than
   a single algorithm, because in different contexts, not all the
   sources of keys will be used, they can be tried in different orders,
   and sometimes not all the collected keys will be tried; hence,
   different algorithms will be used in different application contexts.

   The steps below are described for illustration purposes only;
   specific applications can and are likely to use different algorithms
   or perform some of the steps in different orders.  Specific
   applications will frequently have a much simpler method of
   determining the keys to use, as there may be one or two key selection
   methods that are profiled for the application's use.  This appendix
   supplements the normative information on key location in Section 6.

   These algorithms include the following steps.  Note that the steps
   can be performed in any order and do not need to be treated as
   distinct.  For example, keys can be tried as soon as they are found,
   rather than collecting all the keys before trying any.

   1.  Collect the set of potentially applicable keys.  Sources of keys
       may include:

       *  Keys supplied by the application protocol being used.

       *  Keys referenced by the "jku" (JWK Set URL) Header Parameter.

       *  The key provided by the "jwk" (JSON Web Key) Header Parameter.

       *  The key referenced by the "x5u" (X.509 URL) Header Parameter.

       *  The key provided by the "x5c" (X.509 Certificate Chain) Header
          Parameter.




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       *  Other applicable keys available to the application.

       The order for collecting and trying keys from different key
       sources is typically application dependent.  For example,
       frequently all keys from a one set of locations, such as local
       caches, will be tried before collecting and trying keys from
       other locations.

   2.  Filter the set of collected keys.  For instance, some
       applications will use only keys referenced by "kid" (key ID) or
       "x5t" (X.509 certificate SHA-1 thumbprint) parameters.  If the
       application uses the "alg" (algorithm), "use" (public key use),
       or "key_ops" (key operations) parameters, keys with keys with
       inappropriate values of those parameters would be excluded.
       Additionally, keys might be filtered to include or exclude keys
       with certain other member values in an application specific
       manner.  For some applications, no filtering will be applied.

   3.  Order the set of collected keys.  For instance, keys referenced
       by "kid" (Key ID) or "x5t" (X.509 Certificate SHA-1 Thumbprint)
       parameters might be tried before keys with neither of these
       values.  Likewise, keys with certain member values might be
       ordered before keys with other member values.  For some
       applications, no ordering will be applied.

   4.  Make trust decisions about the keys.  Signatures made with keys
       not meeting the application's trust criteria would not be
       accepted.  Such criteria might include, but is not limited to the
       source of the key, whether the TLS certificate validates for keys
       retrieved from URLs, whether a key in an X.509 certificate is
       backed by a valid certificate chain, and other information known
       by the application.

   5.  Attempt signature or MAC validation for a JWS object or
       decryption of a JWE object with some or all of the collected and
       possibly filtered and/or ordered keys.  A limit on the number of
       keys to be tried might be applied.  This process will normally
       terminate following a successful validation or decryption.

   Note that it is reasonable for some applications to perform signature
   or MAC validation prior to making a trust decision about a key, since
   keys for which the validation fails need no trust decision.


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

   Conforming implementations must reject input containing critical
   extensions that are not understood or cannot be processed.  The



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   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
   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 Protected 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 F.  Detached Content

   In some contexts, it is useful integrity protect content that is not
   itself contained in a JWS object.  One way to do this is create a JWS
   object in the normal fashion using a representation of the content as
   the payload, but then delete the payload representation from the JWS,
   and send this modified object to the recipient, rather than the JWS.
   When using the JWS Compact Serialization, the deletion is
   accomplished by replacing the second field (which contains
   BASE64URL(JWS Payload)) value with the empty string; when using the
   JWS JSON Serialization, the deletion is accomplished by deleting the
   "payload" member.  This method assumes that the recipient can
   reconstruct the exact payload used in the JWS.  To use the modified
   object, the recipient reconstructs the JWS by re-inserting the
   payload representation into the modified object, and uses the
   resulting JWS in the usual manner.  Note that this method needs no
   support from JWS libraries, as applications can use this method by
   modifying the inputs and outputs of standard JWS libraries.


Appendix G.  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.



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   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, Kathleen Moriarty, Tony Nadalin,
   Hideki Nara, 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, Stephen Farrell, and Kathleen Moriarty served as
   Security area directors during the creation of this specification.


Appendix H.  Document History

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

   -31

   o  Reworded the language about JWS implementations ignoring the "typ"
      and "cty" parameters, explicitly saying that their processing is
      performed by JWS applications.

   o  Added additional guidance on ciphersuites currently considered to
      be appropriate for use, including a reference to a recent update
      by the TLS working group.

   -30

   o  Added subsection headings within the Overview section for the two
      serializations.

   o  Added references and cleaned up the reference syntax in a few
      places.

   o  Applied minor wording changes to the Security Considerations
      section and made other local editorial improvements.

   -29





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   o  Replaced the terms JWS Header, JWE Header, and JWT Header with a
      single JOSE Header term defined in the JWS specification.  This
      also enabled a single Header Parameter definition to be used and
      reduced other areas of duplication between specifications.

   -28

   o  Revised the introduction to the Security Considerations section.
      Also introduced additional subsection headings for security
      considerations items and also moved a security consideration item
      here from the JWA draft.

   o  Added text about when applications typically would and would not
      use "typ" and "cty" header parameters.

   -27

   o  Added the "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) header
      parameter.

   o  Stated that any JSON inputs not conforming to the JSON-text syntax
      defined in RFC 7159 input MUST be rejected in their entirety.

   o  Simplified the TLS requirements.

   -26

   o  Referenced Section 6 of RFC 6125 for TLS server certificate
      identity validation.

   o  Described potential sources of ambiguity in representing the JSON
      objects used in the examples.  The octets of the actual UTF-8
      representations of the JSON objects used in the examples are
      included to remove these ambiguities.

   o  Added a small amount of additional explanatory text to the
      signature validation examples to aid implementers.

   o  Noted that octet sequences are depicted using JSON array notation.

   o  Updated references, including to W3C specifications.

   -25

   o  No changes were made, other than to the version number and date.

   -24




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   o  Updated the JSON reference to RFC 7159.

   -23

   o  Clarified that the base64url encoding includes no line breaks,
      white space, or other additional characters.

   -22

   o  Corrected RFC 2119 terminology usage.

   o  Replaced references to draft-ietf-json-rfc4627bis with RFC 7158.

   -21

   o  Applied review comments to the appendix "Notes on Key Selection",
      addressing issue #93.

   o  Changed some references from being normative to informative,
      addressing issue #90.

   o  Applied review comments to the JSON Serialization section,
      addressing issue #121.

   -20

   o  Made terminology definitions more consistent, addressing issue
      #165.

   o  Restructured the JSON Serialization section to call out the
      parameters used in hanging lists, addressing issue #121.

   o  Described key filtering and refined other aspects of the text in
      the appendix "Notes on Key Selection", addressing issue #93.

   o  Replaced references to RFC 4627 with draft-ietf-json-rfc4627bis,
      addressing issue #90.

   -19

   o  Added the appendix "Notes on Validation Key Selection", addressing
      issue #93.

   o  Reordered the key selection parameters.

   -18





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   o  Updated the mandatory-to-implement (MTI) language to say that
      applications using this specification need to specify what
      serialization and serialization features are used for that
      application, addressing issue #119.

   o  Changes to address editorial and minor issues #25, #89, #97, #110,
      #114, #115, #116, #117, #120, and #184.

   o  Added and used Header Parameter Description registry field.

   -17

   o  Refined the "typ" and "cty" definitions to always be MIME Media
      Types, with the omission of "application/" prefixes recommended
      for brevity, addressing issue #50.

   o  Updated the mandatory-to-implement (MTI) language to say that
      general-purpose implementations must implement the single
      signature/MAC value case for both serializations whereas special-
      purpose implementations can implement just one serialization if
      that meets the needs of the use cases the implementation is
      designed for, addressing issue #119.

   o  Explicitly named all the logical components of a JWS and defined
      the processing rules and serializations in terms of those
      components, addressing issues #60, #61, and #62.

   o  Replaced verbose repetitive phases such as "base64url encode the
      octets of the UTF-8 representation of X" with mathematical
      notation such as "BASE64URL(UTF8(X))".

   o  Terms used in multiple documents are now defined in one place and
      incorporated by reference.  Some lightly used or obvious terms
      were also removed.  This addresses issue #58.

   -16

   o  Changes to address editorial and minor issues #50, #98, #99, #102,
      #104, #106, #107, #111, and #112.

   -15

   o  Clarified that it is an application decision which signatures,
      MACs, or plaintext values must successfully validate for the JWS
      to be accepted, addressing issue #35.

   o  Corrected editorial error in "ES512" example.




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   o  Changes to address editorial and minor issues #34, #96, #100,
      #101, #104, #105, and #106.

   -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.



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

   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.




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   o  Added seriesInfo information to Internet Draft references.

   -07

   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 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.





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   o  Described additional open issues.

   o  Applied editorial suggestions.

   -03

   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.



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

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

   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



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      the inputs and outputs of the steps.

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

   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
   URI:   http://www.thread-safe.com/


   Nat Sakimura
   Nomura Research Institute

   Email: n-sakimura@nri.co.jp
   URI:   http://nat.sakimura.org/











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