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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                              J. Bradley
Expires: May 10, 2013                                      Ping Identity
                                                             N. Sakimura
                                                                     NRI
                                                        November 6, 2012


                        JSON Web Signature (JWS)
                 draft-ietf-jose-json-web-signature-07

Abstract

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

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 10, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  JSON Web Signature (JWS) Overview  . . . . . . . . . . . . . .  5
     3.1.  Example JWS  . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  JWS Header . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Reserved Header Parameter Names  . . . . . . . . . . . . .  7
       4.1.1.  "alg" (Algorithm) Header Parameter . . . . . . . . . .  7
       4.1.2.  "jku" (JWK Set URL) Header Parameter . . . . . . . . .  8
       4.1.3.  "jwk" (JSON Web Key) Header Parameter  . . . . . . . .  8
       4.1.4.  "x5u" (X.509 URL) Header Parameter . . . . . . . . . .  8
       4.1.5.  "x5t" (X.509 Certificate Thumbprint) Header
               Parameter  . . . . . . . . . . . . . . . . . . . . . .  8
       4.1.6.  "x5c" (X.509 Certificate Chain) Header Parameter . . .  9
       4.1.7.  "kid" (Key ID) Header Parameter  . . . . . . . . . . .  9
       4.1.8.  "typ" (Type) Header Parameter  . . . . . . . . . . . .  9
       4.1.9.  "cty" (Content Type) Header Parameter  . . . . . . . . 10
     4.2.  Public Header Parameter Names  . . . . . . . . . . . . . . 10
     4.3.  Private Header Parameter Names . . . . . . . . . . . . . . 10
   5.  Rules for Creating and Validating a JWS  . . . . . . . . . . . 10
   6.  Securing JWSs with Cryptographic Algorithms  . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
     7.1.  JSON Web Signature and Encryption Header Parameters
           Registry . . . . . . . . . . . . . . . . . . . . . . . . . 13
       7.1.1.  Registration Template  . . . . . . . . . . . . . . . . 13
       7.1.2.  Initial Registry Contents  . . . . . . . . . . . . . . 14
     7.2.  JSON Web Signature and Encryption Type Values Registry . . 15
       7.2.1.  Registration Template  . . . . . . . . . . . . . . . . 15
       7.2.2.  Initial Registry Contents  . . . . . . . . . . . . . . 15
     7.3.  Media Type Registration  . . . . . . . . . . . . . . . . . 16
       7.3.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 16
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
     8.1.  Cryptographic Security Considerations  . . . . . . . . . . 16
     8.2.  JSON Security Considerations . . . . . . . . . . . . . . . 17
     8.3.  Unicode Comparison Security Considerations . . . . . . . . 18
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 18
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 20
   Appendix A.  JWS Examples  . . . . . . . . . . . . . . . . . . . . 20



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     A.1.  JWS using HMAC SHA-256 . . . . . . . . . . . . . . . . . . 20
       A.1.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 20
       A.1.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 22
       A.1.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 22
     A.2.  JWS using RSA SHA-256  . . . . . . . . . . . . . . . . . . 23
       A.2.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 23
       A.2.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 26
       A.2.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 26
     A.3.  JWS using ECDSA P-256 SHA-256  . . . . . . . . . . . . . . 26
       A.3.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 26
       A.3.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 28
       A.3.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 28
     A.4.  JWS using ECDSA P-521 SHA-512  . . . . . . . . . . . . . . 29
       A.4.1.  Encoding . . . . . . . . . . . . . . . . . . . . . . . 29
       A.4.2.  Decoding . . . . . . . . . . . . . . . . . . . . . . . 31
       A.4.3.  Validating . . . . . . . . . . . . . . . . . . . . . . 31
     A.5.  Example Plaintext JWS  . . . . . . . . . . . . . . . . . . 32
   Appendix B.  "x5c" (X.509 Certificate Chain) Example . . . . . . . 32
   Appendix C.  Notes on implementing base64url encoding without
                padding . . . . . . . . . . . . . . . . . . . . . . . 34
   Appendix D.  Acknowledgements  . . . . . . . . . . . . . . . . . . 35
   Appendix E.  Open Issues . . . . . . . . . . . . . . . . . . . . . 36
   Appendix F.  Document History  . . . . . . . . . . . . . . . . . . 36
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39



























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1.  Introduction

   JSON Web Signature (JWS) is a compact format for representing content
   secured with digital signatures or Message Authentication Codes
   (MACs) intended for space constrained environments such as HTTP
   Authorization headers and URI query parameters.  It represents this
   content using JavaScript Object Notation (JSON) [RFC4627] based data
   structures.  The JWS cryptographic mechanisms provide integrity
   protection for arbitrary sequences of bytes.

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

1.1.  Notational Conventions

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


2.  Terminology

   JSON Web Signature (JWS)  A data structure cryptographically securing
      a JWS Header and a JWS Payload with a JWS Signature value.

   JWS Header  A string representing a JSON object that describes the
      digital signature or MAC operation applied to create the JWS
      Signature value.

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

   JWS Signature  A byte array containing the cryptographic material
      that secures the JWS Header and the JWS Payload.

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

   Encoded JWS Header  Base64url encoding of the bytes of the UTF-8
      [RFC3629] representation of the JWS Header.





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   Encoded JWS Payload  Base64url encoding of the JWS Payload.

   Encoded JWS Signature  Base64url encoding of the JWS Signature.

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

   Header Parameter Name  The name of a member of the JSON object
      representing a JWS Header.

   Header Parameter Value  The value of a member of the JSON object
      representing a JWS Header.

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

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

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


3.  JSON Web Signature (JWS) Overview

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



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   (JWS-JS) [JWS-JS] specification.)

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

3.1.  Example JWS

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

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

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

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

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

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

   Base64url encoding the bytes of the UTF-8 representation of the JSON
   object yields the following Encoded JWS Payload (with line breaks for
   display purposes only):

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

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

     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

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



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     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .
     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

   This computation is illustrated in more detail in Appendix A.1.


4.  JWS Header

   The members of the JSON object represented by the JWS Header describe
   the digital signature or MAC applied to the Encoded JWS Header and
   the Encoded JWS Payload and optionally additional properties of the
   JWS.  The Header Parameter Names within this object MUST be unique;
   JWSs with duplicate Header Parameter Names MUST be rejected.
   Implementations MUST understand the entire contents of the header;
   otherwise, the JWS MUST be rejected.

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

4.1.  Reserved Header Parameter Names

   The following header parameter names are reserved with meanings as
   defined below.  All the names are short because a core goal of JWSs
   is for the representations to be compact.

   Additional reserved header parameter names MAY be defined via the
   IANA JSON Web Signature and Encryption Header Parameters registry
   Section 7.1.  As indicated by the common registry, JWSs and JWEs
   share a common header parameter space; when a parameter is used by
   both specifications, its usage must be compatible between the
   specifications.

4.1.1.  "alg" (Algorithm) Header Parameter

   The "alg" (algorithm) header parameter identifies the cryptographic
   algorithm used to secure the JWS.  The algorithm specified by the
   "alg" value MUST be supported by the implementation and there MUST be
   a key for use with that algorithm associated with the party that
   digitally signed or MACed the content or the JWS MUST be rejected.
   "alg" values SHOULD either be registered in the IANA JSON Web
   Signature and Encryption Algorithms registry [JWA] or be a URI that
   contains a Collision Resistant Namespace.  The "alg" value is a case
   sensitive string containing a StringOrURI value.  This header



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   parameter is REQUIRED.

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

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

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

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

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

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

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

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

   The "x5t" (X.509 Certificate Thumbprint) header parameter provides a
   base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER
   encoding of the X.509 certificate [RFC5280] corresponding to the key



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   used to digitally sign the JWS.  This header parameter is OPTIONAL.

   If, in the future, certificate thumbprints need to be computed using
   hash functions other than SHA-1, it is suggested that additional
   related header parameters be defined for that purpose.  For example,
   it is suggested that a new "x5t#S256" (X.509 Certificate Thumbprint
   using SHA-256) header parameter could be defined by registering it in
   the IANA JSON Web Signature and Encryption Header Parameters registry
   Section 7.1.

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

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

   See Appendix B for an example "x5c" value.

4.1.7.  "kid" (Key ID) Header Parameter

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

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

4.1.8.  "typ" (Type) Header Parameter

   The "typ" (type) header parameter is used to declare the type of this
   object.  The type value "JWS" MAY be used to indicate that this
   object is a JWS.  The "typ" value is a case sensitive string.  This
   header parameter is OPTIONAL.




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

   "typ" values SHOULD either be registered in the IANA JSON Web
   Signature and Encryption Type Values registry Section 7.2 or be a URI
   that contains a Collision Resistant Namespace.

4.1.9.  "cty" (Content Type) Header Parameter

   The "cty" (content type) header parameter is used to declare the type
   of the secured content (the Payload).  The "cty" value is a case
   sensitive string.  This header parameter is OPTIONAL.

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

4.2.  Public Header Parameter Names

   Additional header parameter names can be defined by those using JWSs.
   However, in order to prevent collisions, any new header parameter
   name SHOULD either be registered in the IANA JSON Web Signature and
   Encryption Header Parameters registry Section 7.1 or be a URI that
   contains a Collision Resistant Namespace.  In each case, the definer
   of the name or value needs to take reasonable precautions to make
   sure they are in control of the part of the namespace they use to
   define the header parameter name.

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

4.3.  Private Header Parameter Names

   A producer and consumer of a JWS may agree to any header parameter
   name that is not a Reserved Name Section 4.1 or a Public Name
   Section 4.2.  Unlike Public Names, these private names are subject to
   collision and should be used with caution.


5.  Rules for Creating and Validating a JWS

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

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

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



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

   4.  Base64url encode the bytes of the UTF-8 representation of the JWS
       Header to create the Encoded JWS Header.

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

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

   7.  The three encoded parts, taken together, are the result.  The
       Compact Serialization of this result is the concatenation of the
       Encoded JWS Header, the Encoded JWS Payload, and the Encoded JWS
       Signature in that order, with the three strings being separated
       by two period ('.') characters.

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

   1.  Parse the three parts of the input (which are separated by period
       ('.') characters when using the JWS Compact Serialization) into
       the Encoded JWS Header, the Encoded JWS Payload, and the Encoded
       JWS Signature.

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

   3.  The resulting JWS Header MUST be completely valid JSON syntax
       conforming to RFC 4627 [RFC4627].

   4.  The resulting JWS Header MUST be validated to only include
       parameters and values whose syntax and semantics are both
       understood and supported.

   5.  The Encoded JWS Payload MUST be successfully base64url decoded
       following the restriction given in this specification that no



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       padding characters have been used.

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

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

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

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

   1.  Remove any JSON applied escaping to produce an array of Unicode
       code points.

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

   3.  Comparisons between the two strings MUST be performed as a
       Unicode code point to code point equality comparison.


6.  Securing JWSs with Cryptographic Algorithms

   JWS uses cryptographic algorithms to digitally sign or MAC the JWS
   Header and the JWS Payload.  The JSON Web Algorithms (JWA) [JWA]
   specification describes a set of cryptographic algorithms and
   identifiers to be used with this specification.  Specifically,
   Section 3.1 specifies a set of "alg" (algorithm) header parameter
   values intended for use this specification.  It also describes the
   semantics and operations that are specific to these algorithms and
   algorithm families.

   Public keys employed for digital signing can be identified using the
   Header Parameter methods described in Section 4.1 or can be
   distributed using methods that are outside the scope of this



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   specification.


7.  IANA Considerations

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

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

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

   Within the review period, the Designated Expert(s) will either
   approve or deny the registration request, communicating this decision
   to the review list and IANA.  Denials should include an explanation
   and, if applicable, suggestions as to how to make the request
   successful.

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

7.1.  JSON Web Signature and Encryption Header Parameters Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption Header Parameters registry for reserved JWS and JWE header
   parameter names.  The registry records the reserved header parameter
   name and a reference to the specification that defines it.  The same
   Header Parameter Name may be registered multiple times, provided that
   the parameter usage is compatible between the specifications.

7.1.1.  Registration Template

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





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

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

7.1.2.  Initial Registry Contents

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

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

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

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

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

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

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

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

   o  Header Parameter Name: "typ"
   o  Change Controller: IETF





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   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

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

7.2.  JSON Web Signature and Encryption Type Values Registry

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

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

7.2.1.  Registration Template

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

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

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

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

7.2.2.  Initial Registry Contents

   This specification registers the "JWS" type value in this registry:






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

7.3.  Media Type Registration

7.3.1.  Registry Contents

   This specification registers the "application/jws" Media Type
   [RFC2046] in the MIME Media Type registry [RFC4288] to indicate that
   the content is a JWS using the Compact Serialization.

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


8.  Security Considerations

8.1.  Cryptographic Security Considerations

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



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

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

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

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

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

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

8.2.  JSON Security Considerations

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

   Section 2.2 of the JavaScript Object Notation (JSON) specification
   [RFC4627] states "The names within an object SHOULD be unique",



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   whereas this specification states that "Header Parameter Names within
   this object MUST be unique; JWSs with duplicate Header Parameter
   Names MUST be rejected".  Thus, this specification requires that the
   Section 2.2 "SHOULD" be treated as a "MUST".  Ambiguous and
   potentially exploitable situations could arise if the JSON parser
   used does not enforce the uniqueness of member names.

8.3.  Unicode Comparison Security Considerations

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

   JSON strings MAY 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.


9.  References

9.1.  Normative References

   [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)", November 2012.

   [JWK]      Jones, M., "JSON Web Key (JWK)", November 2012.

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

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



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              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.

   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
              Registration Procedures", BCP 13, RFC 4288, December 2005.

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

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

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

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

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

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

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

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




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9.2.  Informative References

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

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

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", November 2012.

   [JWS-JS]   Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature JSON Serialization (JWS-JS)", November 2012.

   [JWT]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", November 2012.

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

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

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


Appendix A.  JWS Examples

   This section provides several examples of JWSs.  While these examples
   all represent JSON Web Tokens (JWTs) [JWT], the payload can be any
   base64url encoded content.

A.1.  JWS using HMAC SHA-256

A.1.1.  Encoding

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

     {"typ":"JWT",



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      "alg":"HS256"}

   The following byte array contains the UTF-8 representation of the JWS
   Header:

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

   Base64url encoding these bytes yields this Encoded JWS Header value:

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

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

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

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

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

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

     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

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

     eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The ASCII representation of the JWS Secured Input is the following
   byte array:




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   [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 key
   represented by the following byte array:

   [3, 35, 53, 75, 43, 15, 165, 188, 131, 126, 6, 101, 119, 123, 166,
   143, 90, 179, 40, 230, 240, 84, 201, 40, 169, 15, 132, 178, 210, 80,
   46, 191, 211, 251, 90, 146, 210, 6, 71, 239, 150, 138, 180, 195, 119,
   98, 61, 34, 61, 46, 33, 114, 5, 46, 79, 8, 192, 205, 154, 245, 103,
   208, 128, 163]

   Running the HMAC SHA-256 algorithm on the bytes of the ASCII
   representation of the JWS Secured Input with this key yields the
   following byte array:

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

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

     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

A.1.2.  Decoding

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

A.1.3.  Validating

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

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



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

A.2.  JWS using RSA SHA-256

A.2.1.  Encoding

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

     {"alg":"RS256"}

   The following byte array contains the UTF-8 representation of the JWS
   Header:

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

   Base64url encoding these bytes yields this Encoded JWS Header value:

     eyJhbGciOiJSUzI1NiJ9

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

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

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

     eyJhbGciOiJSUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The ASCII representation of the JWS Secured Input is the following
   byte array:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 122, 73,



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   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]

   The RSA key consists of a public part (Modulus, Exponent), and a
   Private Exponent.  The values of the RSA key used in this example,
   presented as the byte arrays representing big endian integers are:

   +-----------+-------------------------------------------------------+
   | Parameter | Value                                                 |
   | Name      |                                                       |
   +-----------+-------------------------------------------------------+
   | Modulus   | [161, 248, 22, 10, 226, 227, 201, 180, 101, 206, 141, |
   |           | 45, 101, 98, 99, 54, 43, 146, 125, 190, 41, 225, 240, |
   |           | 36, 119, 252, 22, 37, 204, 144, 161, 54, 227, 139,    |
   |           | 217, 52, 151, 197, 182, 234, 99, 221, 119, 17, 230,   |
   |           | 124, 116, 41, 249, 86, 176, 251, 138, 143, 8, 154,    |
   |           | 220, 75, 105, 137, 60, 193, 51, 63, 83, 237, 208, 25, |
   |           | 184, 119, 132, 37, 47, 236, 145, 79, 228, 133, 119,   |
   |           | 105, 89, 75, 234, 66, 128, 211, 44, 15, 85, 191, 98,  |
   |           | 148, 79, 19, 3, 150, 188, 110, 155, 223, 110, 189,    |
   |           | 210, 189, 163, 103, 142, 236, 160, 198, 104, 247, 1,  |
   |           | 179, 141, 191, 251, 56, 200, 52, 44, 226, 254, 109,   |
   |           | 39, 250, 222, 74, 90, 72, 116, 151, 157, 212, 185,    |
   |           | 207, 154, 222, 196, 199, 91, 5, 133, 44, 44, 15, 94,  |
   |           | 248, 165, 193, 117, 3, 146, 249, 68, 232, 237, 100,   |
   |           | 193, 16, 198, 182, 71, 96, 154, 164, 120, 58, 235,    |
   |           | 156, 108, 154, 215, 85, 49, 48, 80, 99, 139, 131,     |
   |           | 102, 92, 111, 111, 122, 130, 163, 150, 112, 42, 31,   |
   |           | 100, 27, 130, 211, 235, 242, 57, 34, 25, 73, 31, 182, |
   |           | 134, 135, 44, 87, 22, 245, 10, 248, 53, 141, 154,     |
   |           | 139, 157, 23, 195, 64, 114, 143, 127, 135, 216, 154,  |
   |           | 24, 216, 252, 171, 103, 173, 132, 89, 12, 46, 207,    |
   |           | 117, 147, 57, 54, 60, 7, 3, 77, 111, 96, 111, 158,    |
   |           | 33, 224, 84, 86, 202, 229, 233, 161]                  |
   | Exponent  | [1, 0, 1]                                             |











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   | Private   | [18, 174, 113, 164, 105, 205, 10, 43, 195, 126, 82,   |
   | Exponent  | 108, 69, 0, 87, 31, 29, 97, 117, 29, 100, 233, 73,    |
   |           | 112, 123, 98, 89, 15, 157, 11, 165, 124, 150, 60, 64, |
   |           | 30, 63, 207, 47, 44, 211, 189, 236, 136, 229, 3, 191, |
   |           | 198, 67, 155, 11, 40, 200, 47, 125, 55, 151, 103, 31, |
   |           | 82, 19, 238, 216, 193, 90, 37, 216, 213, 206, 160, 2, |
   |           | 94, 227, 171, 46, 139, 127, 121, 33, 111, 198, 59,    |
   |           | 234, 86, 39, 83, 180, 6, 68, 198, 161, 81, 39, 217,   |
   |           | 178, 149, 69, 64, 160, 187, 225, 163, 5, 86, 152, 45, |
   |           | 78, 159, 222, 95, 100, 37, 241, 77, 75, 113, 52, 65,  |
   |           | 181, 93, 199, 59, 155, 74, 237, 204, 146, 172, 227,   |
   |           | 146, 126, 55, 245, 125, 12, 253, 94, 117, 129, 250,   |
   |           | 81, 44, 143, 73, 97, 169, 235, 11, 128, 248, 168, 7,  |
   |           | 70, 114, 138, 85, 255, 70, 71, 31, 52, 37, 6, 59,     |
   |           | 157, 83, 100, 47, 94, 222, 30, 132, 214, 19, 8, 26,   |
   |           | 250, 92, 34, 208, 81, 40, 91, 214, 59, 148, 59, 86,   |
   |           | 93, 137, 138, 5, 104, 84, 19, 229, 60, 60, 108, 101,  |
   |           | 37, 255, 31, 227, 78, 61, 220, 112, 240, 213, 100,    |
   |           | 80, 253, 164, 139, 161, 46, 16, 78, 157, 235, 159,    |
   |           | 184, 24, 129, 225, 196, 189, 242, 93, 146, 71, 244,   |
   |           | 80, 200, 101, 146, 121, 104, 231, 115, 52, 244, 65,   |
   |           | 79, 117, 167, 80, 225, 57, 84, 110, 58, 138, 115,     |
   |           | 157]                                                  |
   +-----------+-------------------------------------------------------+

   The RSA private key (Modulus, Private Exponent) is then passed to the
   RSA signing function, which also takes the hash type, SHA-256, and
   the bytes of the ASCII representation of the JWS Secured Input as
   inputs.  The result of the digital signature is a byte array, 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,



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   251, 71]

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

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

A.2.2.  Decoding

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

A.2.3.  Validating

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

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

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

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

A.3.1.  Encoding

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

     {"alg":"ES256"}

   The following byte array contains the UTF-8 representation of the JWS
   Header:

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



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   Base64url encoding these bytes yields this Encoded JWS Header value:

     eyJhbGciOiJFUzI1NiJ9

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

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

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

     eyJhbGciOiJFUzI1NiJ9
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The ASCII representation of the JWS Secured Input is the following
   byte array:

   [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]

   The ECDSA key consists of a public part, the EC point (x, y), and a
   private part d.  The values of the ECDSA key used in this example,
   presented as the byte arrays representing three 256 bit big endian
   integers are:

   +-----------+-------------------------------------------------------+
   | Parameter | Value                                                 |
   | Name      |                                                       |
   +-----------+-------------------------------------------------------+
   | x         | [127, 205, 206, 39, 112, 246, 196, 93, 65, 131, 203,  |
   |           | 238, 111, 219, 75, 123, 88, 7, 51, 53, 123, 233, 239, |
   |           | 19, 186, 207, 110, 60, 123, 209, 84, 69]              |
   | y         | [199, 241, 68, 205, 27, 189, 155, 126, 135, 44, 223,  |
   |           | 237, 185, 238, 185, 244, 179, 105, 93, 110, 169, 11,  |
   |           | 36, 173, 138, 70, 35, 40, 133, 136, 229, 173]         |



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   | d         | [142, 155, 16, 158, 113, 144, 152, 191, 152, 4, 135,  |
   |           | 223, 31, 93, 119, 233, 203, 41, 96, 110, 190, 210,    |
   |           | 38, 59, 95, 87, 194, 19, 223, 132, 244, 178]          |
   +-----------+-------------------------------------------------------+

   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 bytes of the ASCII representation of the JWS Secured 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 byte arrays representing big endian integers are:

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

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

     DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA
     pmWQxfKTUJqPP3-Kg6NU1Q

A.3.2.  Decoding

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

A.3.3.  Validating

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

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

   Validating the JWS Signature is a little different from the first



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   example.  First, we base64url decode the Encoded JWS Signature as in
   the previous examples but we then need to split the 64 member byte
   array that must result into two 32 byte arrays, the first R and the
   second S. We then pass (x, y), (R, S) and the bytes of the ASCII
   representation of the JWS Secured Input to an ECDSA signature
   verifier that has been configured to use the P-256 curve with the
   SHA-256 hash function.

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

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

A.4.1.  Encoding

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

     {"alg":"ES512"}

   The following byte array contains the UTF-8 representation of the JWS
   Header:

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

   Base64url encoding these bytes yields this Encoded JWS Header value:

     eyJhbGciOiJFUzUxMiJ9

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

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

   Base64url encoding these bytes yields the Encoded JWS Payload value:

     UGF5bG9hZA

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

     eyJhbGciOiJFUzUxMiJ9.UGF5bG9hZA

   The ASCII representation of the JWS Secured Input is the following



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   byte array:

   [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]

   The ECDSA key consists of a public part, the EC point (x, y), and a
   private part d.  The values of the ECDSA key used in this example,
   presented as the byte arrays representing three 521 bit big endian
   integers are:

   +-----------+-------------------------------------------------------+
   | Parameter | Value                                                 |
   | Name      |                                                       |
   +-----------+-------------------------------------------------------+
   | x         | [1, 233, 41, 5, 15, 18, 79, 198, 188, 85, 199, 213,   |
   |           | 57, 51, 101, 223, 157, 239, 74, 176, 194, 44, 178,    |
   |           | 87, 152, 249, 52, 235, 4, 227, 198, 186, 227, 112,    |
   |           | 26, 87, 167, 145, 14, 157, 129, 191, 54, 49, 89, 232, |
   |           | 235, 203, 21, 93, 99, 73, 244, 189, 182, 204, 248,    |
   |           | 169, 76, 92, 89, 199, 170, 193, 1, 164]               |
   | y         | [0, 52, 166, 68, 14, 55, 103, 80, 210, 55, 31, 209,   |
   |           | 189, 194, 200, 243, 183, 29, 47, 78, 229, 234, 52,    |
   |           | 50, 200, 21, 204, 163, 21, 96, 254, 93, 147, 135,     |
   |           | 236, 119, 75, 85, 131, 134, 48, 229, 203, 191, 90,    |
   |           | 140, 190, 10, 145, 221, 0, 100, 198, 153, 154, 31,    |
   |           | 110, 110, 103, 250, 221, 237, 228, 200, 200, 246]     |
   | d         | [1, 142, 105, 111, 176, 52, 80, 88, 129, 221, 17, 11, |
   |           | 72, 62, 184, 125, 50, 206, 73, 95, 227, 107, 55, 69,  |
   |           | 237, 242, 216, 202, 228, 240, 242, 83, 159, 70, 21,   |
   |           | 160, 233, 142, 171, 82, 179, 192, 197, 234, 196, 206, |
   |           | 7, 81, 133, 168, 231, 187, 71, 222, 172, 29, 29, 231, |
   |           | 123, 204, 246, 97, 53, 230, 61, 130]                  |
   +-----------+-------------------------------------------------------+

   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 bytes of the ASCII representation of the JWS Secured 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 byte arrays representing big endian integers are:











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

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

     AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq
     wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp
     EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn

A.4.2.  Decoding

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

A.4.3.  Validating

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

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

   Validating the JWS Signature is similar to the previous example.
   First, we base64url decode the Encoded JWS Signature as in the
   previous examples but we then need to split the 132 member byte array
   that must result into two 66 byte arrays, the first R and the second
   S. We then pass (x, y), (R, S) and the bytes of the ASCII
   representation of the JWS Secured Input to an ECDSA signature



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   verifier that has been configured to use the P-521 curve with the
   SHA-512 hash function.

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

A.5.  Example Plaintext JWS

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

     {"alg":"none"}

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

     eyJhbGciOiJub25lIn0

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

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

   The Encoded JWS Signature is the empty string.

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

     eyJhbGciOiJub25lIn0
     .
     eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
     cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
     .


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



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   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
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Appendix C.  Notes on implementing base64url encoding without padding

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

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
















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

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

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

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


Appendix D.  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.  Dirk
   Balfanz, Yaron Y. Goland, John Panzer, and Paul Tarjan all made
   significant contributions to the design of this specification.



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

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


Appendix E.  Open Issues

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

   The following items remain to be considered or done in this draft:

   o  Should we define optional nonce, timestamp, and/or uninterpreted
      string header parameter(s)?


Appendix F.  Document History

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

   -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





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

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

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

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

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

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

   o  Described additional open issues.

   o  Applied editorial suggestions.

   -03

   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.




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   o  Added Registry Contents sections to populate registry values.

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

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

   o  Numerous editorial improvements.

   -02

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

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

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

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

   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.




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

   -01

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

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

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

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

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

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

   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/




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   John Bradley
   Ping Identity

   Email: ve7jtb@ve7jtb.com


   Nat Sakimura
   Nomura Research Institute

   Email: n-sakimura@nri.co.jp









































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