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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                             E. Rescorla
Expires: April 10, 2014                                             RTFM
                                                           J. Hildebrand
                                                                   Cisco
                                                         October 7, 2013


                       JSON Web Encryption (JWE)
                 draft-ietf-jose-json-web-encryption-17

Abstract

   JSON Web Encryption (JWE) represents encrypted content 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 IANA registries defined by that specification.
   Related digital signature and MAC capabilities are described in the
   separate JSON Web Signature (JWS) 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 April 10, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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



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


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  JSON Web Encryption (JWE) Overview . . . . . . . . . . . . . .  7
     3.1.  Example JWE  . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  JWE Header . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.1.  Registered Header Parameter Names  . . . . . . . . . . . . 11
       4.1.1.  "alg" (Algorithm) Header Parameter . . . . . . . . . . 11
       4.1.2.  "enc" (Encryption Method) Header Parameter . . . . . . 12
       4.1.3.  "zip" (Compression Algorithm) Header Parameter . . . . 12
       4.1.4.  "jku" (JWK Set URL) Header Parameter . . . . . . . . . 12
       4.1.5.  "jwk" (JSON Web Key) Header Parameter  . . . . . . . . 13
       4.1.6.  "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 13
       4.1.7.  "x5t" (X.509 Certificate SHA-1 Thumbprint) Header
               Parameter  . . . . . . . . . . . . . . . . . . . . . . 13
       4.1.8.  "x5c" (X.509 Certificate Chain) Header Parameter . . . 13
       4.1.9.  "kid" (Key ID) Header Parameter  . . . . . . . . . . . 13
       4.1.10. "typ" (Type) Header Parameter  . . . . . . . . . . . . 13
       4.1.11. "cty" (Content Type) Header Parameter  . . . . . . . . 14
       4.1.12. "crit" (Critical) Header Parameter . . . . . . . . . . 14
     4.2.  Public Header Parameter Names  . . . . . . . . . . . . . . 14
     4.3.  Private Header Parameter Names . . . . . . . . . . . . . . 14
   5.  Producing and Consuming JWEs . . . . . . . . . . . . . . . . . 14
     5.1.  Message Encryption . . . . . . . . . . . . . . . . . . . . 14
     5.2.  Message Decryption . . . . . . . . . . . . . . . . . . . . 16
     5.3.  String Comparison Rules  . . . . . . . . . . . . . . . . . 19
   6.  Key Identification . . . . . . . . . . . . . . . . . . . . . . 19
   7.  Serializations . . . . . . . . . . . . . . . . . . . . . . . . 19
     7.1.  JWE Compact Serialization  . . . . . . . . . . . . . . . . 19
     7.2.  JWE JSON Serialization . . . . . . . . . . . . . . . . . . 19
   8.  Distinguishing Between JWS and JWE Objects . . . . . . . . . . 22
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 23
     9.1.  JWE Header Parameter Names Registration  . . . . . . . . . 23
       9.1.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 23
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 25
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 25
     11.2. Informative References . . . . . . . . . . . . . . . . . . 26
   Appendix A.  JWE Examples  . . . . . . . . . . . . . . . . . . . . 27



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     A.1.  Example JWE using RSAES OAEP and AES GCM . . . . . . . . . 27
       A.1.1.  JWE Header . . . . . . . . . . . . . . . . . . . . . . 27
       A.1.2.  Content Encryption Key (CEK) . . . . . . . . . . . . . 27
       A.1.3.  Key Encryption . . . . . . . . . . . . . . . . . . . . 28
       A.1.4.  Initialization Vector  . . . . . . . . . . . . . . . . 29
       A.1.5.  Additional Authenticated Data  . . . . . . . . . . . . 29
       A.1.6.  Content Encryption . . . . . . . . . . . . . . . . . . 29
       A.1.7.  Complete Representation  . . . . . . . . . . . . . . . 30
       A.1.8.  Validation . . . . . . . . . . . . . . . . . . . . . . 30
     A.2.  Example JWE using RSAES-PKCS1-V1_5 and
           AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 30
       A.2.1.  JWE Header . . . . . . . . . . . . . . . . . . . . . . 31
       A.2.2.  Content Encryption Key (CEK) . . . . . . . . . . . . . 31
       A.2.3.  Key Encryption . . . . . . . . . . . . . . . . . . . . 31
       A.2.4.  Initialization Vector  . . . . . . . . . . . . . . . . 33
       A.2.5.  Additional Authenticated Data  . . . . . . . . . . . . 33
       A.2.6.  Content Encryption . . . . . . . . . . . . . . . . . . 33
       A.2.7.  Complete Representation  . . . . . . . . . . . . . . . 34
       A.2.8.  Validation . . . . . . . . . . . . . . . . . . . . . . 34
     A.3.  Example JWE using AES Key Wrap and
           AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 34
       A.3.1.  JWE Header . . . . . . . . . . . . . . . . . . . . . . 34
       A.3.2.  Content Encryption Key (CEK) . . . . . . . . . . . . . 35
       A.3.3.  Key Encryption . . . . . . . . . . . . . . . . . . . . 35
       A.3.4.  Initialization Vector  . . . . . . . . . . . . . . . . 36
       A.3.5.  Additional Authenticated Data  . . . . . . . . . . . . 36
       A.3.6.  Content Encryption . . . . . . . . . . . . . . . . . . 36
       A.3.7.  Complete Representation  . . . . . . . . . . . . . . . 37
       A.3.8.  Validation . . . . . . . . . . . . . . . . . . . . . . 37
     A.4.  Example JWE using JWE JSON Serialization . . . . . . . . . 37
       A.4.1.  JWE Per-Recipient Unprotected Headers  . . . . . . . . 38
       A.4.2.  JWE Protected Header . . . . . . . . . . . . . . . . . 38
       A.4.3.  JWE Unprotected Header . . . . . . . . . . . . . . . . 38
       A.4.4.  Complete JWE Header Values . . . . . . . . . . . . . . 38
       A.4.5.  Additional Authenticated Data  . . . . . . . . . . . . 39
       A.4.6.  Content Encryption . . . . . . . . . . . . . . . . . . 39
       A.4.7.  Complete JWE JSON Serialization Representation . . . . 39
   Appendix B.  Example AES_128_CBC_HMAC_SHA_256 Computation  . . . . 40
     B.1.  Extract MAC_KEY and ENC_KEY from Key . . . . . . . . . . . 40
     B.2.  Encrypt Plaintext to Create Ciphertext . . . . . . . . . . 41
     B.3.  64 Bit Big Endian Representation of AAD Length . . . . . . 41
     B.4.  Initialization Vector Value  . . . . . . . . . . . . . . . 41
     B.5.  Create Input to HMAC Computation . . . . . . . . . . . . . 42
     B.6.  Compute HMAC Value . . . . . . . . . . . . . . . . . . . . 42
     B.7.  Truncate HMAC Value to Create Authentication Tag . . . . . 42
   Appendix C.  Acknowledgements  . . . . . . . . . . . . . . . . . . 42
   Appendix D.  Document History  . . . . . . . . . . . . . . . . . . 43
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 51



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1.  Introduction

   JSON Web Encryption (JWE) represents encrypted content using
   JavaScript Object Notation (JSON) [RFC4627] based data structures.
   The JWE cryptographic mechanisms encrypt and provide integrity
   protection for an arbitrary sequence of octets.

   Two closely related serializations for JWE objects are defined.  The
   JWE Compact Serialization is a compact, URL-safe representation
   intended for space constrained environments such as HTTP
   Authorization headers and URI query parameters.  The JWE JSON
   Serialization represents JWE objects as JSON objects and enables the
   same content to be encrypted to multiple parties.  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 IANA registries defined by that
   specification.  Related digital signature and MAC capabilities are
   described in the separate JSON Web Signature (JWS) [JWS]
   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", "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 defined by the JSON Web Signature (JWS) [JWS]
   specification are incorporated into this specification: "JSON Web
   Signature (JWS)", "JSON Text Object", "Base64url Encoding",
   "Collision Resistant Name", and "StringOrURI".

   These terms are defined for use by this specification:

   JSON Web Encryption (JWE)  A data structure representing an encrypted
      and integrity protected message.

   Authenticated Encryption with Associated Data (AEAD)  An AEAD
      algorithm is one that encrypts the Plaintext, allows Additional
      Authenticated Data to be specified, and provides an integrated
      content integrity check over the Ciphertext and Additional
      Authenticated Data.  AEAD algorithms accept two inputs, the
      Plaintext and the Additional Authenticated Data value, and produce
      two outputs, the Ciphertext and the Authentication Tag value.  AES
      Galois/Counter Mode (GCM) is one such algorithm.

   Plaintext  The sequence of octets to be encrypted -- a.k.a., the
      message.  The plaintext can contain an arbitrary sequence of
      octets.

   Ciphertext  An encrypted representation of the Plaintext.

   Additional Authenticated Data (AAD)  An input to an AEAD operation
      that is integrity protected but not encrypted.

   Authentication Tag  An output of an AEAD operation that ensures the
      integrity of the Ciphertext and the Additional Authenticated Data.
      Note that some algorithms may not use an Authentication Tag, in
      which case this value is the empty octet sequence.

   Content Encryption Key (CEK)  A symmetric key for the AEAD algorithm
      used to encrypt the Plaintext for the recipient to produce the
      Ciphertext and the Authentication Tag.

   JWE Header  A JSON Text Object (or JSON Text Objects, when using the
      JWE JSON Serialization) that describes the encryption operations
      applied to create the JWE Encrypted Key, the JWE Ciphertext, and
      the JWE Authentication Tag. The members of the JWE Header
      object(s) are Header Parameters.







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   JWE Encrypted Key  The result of encrypting the Content Encryption
      Key (CEK) with the intended recipient's key using the specified
      algorithm.  Note that for some algorithms, the JWE Encrypted Key
      value is specified as being the empty octet sequence.

   JWE Initialization Vector  A sequence of octets containing the
      Initialization Vector used when encrypting the Plaintext.  Note
      that some algorithms may not use an Initialization Vector, in
      which case this value is the empty octet sequence.

   JWE Ciphertext  A sequence of octets containing the Ciphertext for a
      JWE.

   JWE Authentication Tag  A sequence of octets containing the
      Authentication Tag for a JWE.

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

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

   JWE Compact Serialization  A representation of the JWE as the string
      BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE
      Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) ||
      '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
      Authentication Tag).  This representation is compact and URL-safe.

   JWE JSON Serialization  A representation of the JWE as a JSON
      structure.  Unlike the JWE Compact Serialization, the JWE JSON
      Serialization enables the same content to be encrypted to multiple
      parties.  This representation is neither compact nor URL-safe.

   Key Management Mode  A method of determining the Content Encryption
      Key (CEK) value to use.  Each algorithm used for determining the
      CEK value uses a specific Key Management Mode.  Key Management
      Modes employed by this specification are Key Encryption, Key
      Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping,
      and Direct Encryption.

   Key Encryption  A Key Management Mode in which the Content Encryption
      Key (CEK) value is encrypted to the intended recipient using an
      asymmetric encryption algorithm.







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   Key Wrapping  A Key Management Mode in which the Content Encryption
      Key (CEK) value is encrypted to the intended recipient using a
      symmetric key wrapping algorithm.

   Direct Key Agreement  A Key Management Mode in which a key agreement
      algorithm is used to agree upon the Content Encryption Key (CEK)
      value.

   Key Agreement with Key Wrapping  A Key Management Mode in which a key
      agreement algorithm is used to agree upon a symmetric key used to
      encrypt the Content Encryption Key (CEK) value to the intended
      recipient using a symmetric key wrapping algorithm.

   Direct Encryption  A Key Management Mode in which the Content
      Encryption Key (CEK) value used is the secret symmetric key value
      shared between the parties.


3.  JSON Web Encryption (JWE) Overview

   JWE represents encrypted content using JSON data structures and
   base64url encoding.  A JWE represents these logical values:

   JWE Header  JSON object containing the parameters describing the
      cryptographic operations and parameters employed.  The JWE Header
      members are the union of the members of the JWE Protected Header,
      the JWE Shared Unprotected Header, and the JWE Per-Recipient
      Unprotected Header, as described below.

   JWE Encrypted Key  Encrypted Content Encryption Key (CEK) value.

   JWE Initialization Vector  Initialization Vector value used when
      encrypting the plaintext.

   JWE Ciphertext  Ciphertext value resulting from authenticated
      encryption of the plaintext.

   JWE Authentication Tag  Authentication Tag value resulting from
      authenticated encryption of the plaintext with additional
      associated data.

   JWE AAD  Additional value to be integrity protected by the
      authenticated encryption operation.

   The JWE Header represents the combination of these logical values:






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   JWE Protected Header  JSON object containing some of the parameters
      describing the cryptographic operations and parameters employed.
      These parameters apply to all recipients of the JWE.  This value
      is integrity protected in the digital signature or MAC calculation
      of the JWE Signature.

   JWE Shared Unprotected Header  JSON object containing some of the
      parameters describing the cryptographic operations and parameters
      employed.  These parameters apply to all recipients of the JWE.
      This value is not integrity protected in the authenticated
      encryption operation.

   JWE Per-Recipient Unprotected Header  JSON object containing some of
      the parameters describing the cryptographic operations and
      parameters employed.  These parameters apply to a single recipient
      of the JWE.  This value is not integrity protected in the
      authenticated encryption operation.

   This document defines two serializations for JWE objects: a compact,
   URL-safe serialization called the JWE Compact Serialization and a
   JSON serialization called the JWE JSON Serialization.  In both
   serializations, the JWE Protected Header, JWE Encrypted Key, JWE
   Initialization Vector, JWE Ciphertext, and JWE Authentication Tag are
   base64url encoded for transmission, since JSON lacks a way to
   directly represent octet sequences.  When present, the JWE AAD is
   also base64url encoded for transmission.

   In the JWE Compact Serialization, no JWE Shared Unprotected Header or
   JWE Per-Recipient Unprotected Header are used.  In this case, the JWE
   Header and the JWE Protected Header are the same.

   In the JWE Compact Serialization, a JWE object is represented as the
   combination of these five string values,
      BASE64URL(UTF8(JWE Protected Header)),
      BASE64URL(JWE Encrypted Key),
      BASE64URL(JWE Initialization Vector),
      BASE64URL(JWE Ciphertext), and
      BASE64URL(JWE Authentication Tag),
   concatenated in that order, with the five strings being separated by
   four period ('.') characters.

   In the JWE JSON Serialization, one or more of the JWE Protected
   Header, JWE Shared Unprotected Header, and JWE Per-Recipient
   Unprotected Header MUST be present.  In this case, the members of the
   JWE Header are the combination of the members of the JWE Protected
   Header, JWE Shared Unprotected Header, and JWE Per-Recipient
   Unprotected Header values that are present.




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   In the JWE JSON Serialization, a JWE object is represented as the
   combination of these eight values,
      BASE64URL(UTF8(JWE Protected Header)),
      JWE Shared Unprotected Header,
      JWE Per-Recipient Unprotected Header,
      BASE64URL(JWE Encrypted Key),
      BASE64URL(JWE Initialization Vector),
      BASE64URL(JWE Ciphertext),
      BASE64URL(JWE Authentication Tag), and
      BASE64URL(JWE AAD),
   with the six base64url encoding result strings and the two
   unprotected JSON object values being represented as members within a
   JSON object.  The inclusion of some of these values is OPTIONAL.  The
   JWE JSON Serialization can also encrypt the plaintext to multiple
   recipients.  See Section 7.2 for more information about the JWE JSON
   Serialization.

   JWE utilizes authenticated encryption to ensure the confidentiality
   and integrity of the Plaintext and the integrity of the JWE Protected
   Header and the JWE AAD.

3.1.  Example JWE

   This example encrypts the plaintext "The true sign of intelligence is
   not knowledge but imagination." to the recipient using RSAES OAEP for
   key encryption and AES GCM for content encryption.

   The following example JWE Protected Header declares that:

   o  the Content Encryption Key is encrypted to the recipient using the
      RSAES OAEP algorithm to produce the JWE Encrypted Key and

   o  the Plaintext is encrypted using the AES GCM algorithm with a 256
      bit key to produce the Ciphertext.


     {"alg":"RSA-OAEP","enc":"A256GCM"}

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

     eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

   The remaining steps to finish creating this JWE are:

   o  Generate a random Content Encryption Key (CEK).





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   o  Encrypt the CEK with the recipient's public key using the RSAES
      OAEP algorithm to produce the JWE Encrypted Key.

   o  Base64url encode the JWE Encrypted Key.

   o  Generate a random JWE Initialization Vector.

   o  Base64url encode the JWE Initialization Vector.

   o  Let the Additional Authenticated Data encryption parameter be
      ASCII(BASE64URL(UTF8(JWE Protected Header))).

   o  Encrypt the Plaintext with AES GCM using the CEK as the encryption
      key, the JWE Initialization Vector, and the Additional
      Authenticated Data value, requesting a 128 bit Authentication Tag
      output.

   o  Base64url encode the Ciphertext.

   o  Base64url encode the Authentication Tag.

   o  Assemble the final representation: The Compact Serialization of
      this result is the string BASE64URL(UTF8(JWE Protected Header)) ||
      '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE
      Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.'
      || BASE64URL(JWE Authentication Tag).

   The final result in this example (with line breaks for display
   purposes only) is:

     eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
     OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
     ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
     Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
     mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
     1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
     6UklfCpIMfIjf7iGdXKHzg.
     48V1_ALb6US04U3b.
     5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
     SdiwkIr3ajwQzaBtQD_A.
     XFBoMYUZodetZdvTiFvSkQ

   See Appendix A.1 for the complete details of computing this JWE.  See
   Appendix A for additional examples.







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4.  JWE Header

   The members of the JSON object(s) representing the JWE Header
   describe the encryption applied to the Plaintext and optionally
   additional properties of the JWE.  The Header Parameter names within
   the JWE Header MUST be unique; recipients MUST either reject JWEs
   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 4.1.12, 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.

4.1.  Registered Header Parameter Names

   The following Header Parameter names are registered in the IANA JSON
   Web Signature and Encryption Header Parameters registry defined in
   [JWS], 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

   This parameter has the same meaning, syntax, and processing rules as
   the "alg" Header Parameter defined in Section 4.1.1 of [JWS], except
   that the Header Parameter identifies the cryptographic algorithm used
   to encrypt or determine the value of the Content Encryption Key
   (CEK).  The encrypted content is not usable if the "alg" value does
   not represent a supported algorithm, or if the recipient does not
   have a key that can be used with that algorithm.

   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 4.1 of the JSON Web Algorithms (JWA) [JWA] specification.



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4.1.2.  "enc" (Encryption Method) Header Parameter

   The "enc" (encryption method) Header Parameter identifies the content
   encryption algorithm used to encrypt the Plaintext to produce the
   Ciphertext.  This algorithm MUST be an AEAD algorithm with a
   specified key length.  The recipient MUST reject the JWE if the "enc"
   value does not represent a supported algorithm. "enc" 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 "enc" value is a case sensitive string
   containing a StringOrURI value.  Use of this Header Parameter is
   REQUIRED.  This Header Parameter MUST be understood and processed by
   implementations.

   A list of defined "enc" 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 4.2 of the JSON Web Algorithms (JWA) [JWA] specification.

4.1.3.  "zip" (Compression Algorithm) Header Parameter

   The "zip" (compression algorithm) applied to the Plaintext before
   encryption, if any.  The "zip" value defined by this specification
   is:

   o  "DEF" - Compression with the DEFLATE [RFC1951] algorithm

   Other values MAY be used.  Compression algorithm values can be
   registered in the IANA JSON Web Encryption Compression Algorithm
   registry defined in [JWA].  The "zip" value is a case sensitive
   string.  If no "zip" parameter is present, no compression is applied
   to the Plaintext before encryption.  This Header Parameter MUST be
   integrity protected, and therefore MUST occur only within the JWE
   Protected Header, when used.  Use of this Header Parameter is
   OPTIONAL.  This Header Parameter MUST be understood and processed by
   implementations.

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

   This parameter has the same meaning, syntax, and processing rules as
   the "jku" Header Parameter defined in Section 4.1.2 of [JWS], except
   that the JWK Set resource contains the public key to which the JWE
   was encrypted; this can be used to determine the private key needed
   to decrypt the JWE.







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

   This parameter has the same meaning, syntax, and processing rules as
   the "jwk" Header Parameter defined in Section 4.1.3 of [JWS], except
   that the key is the public key to which the JWE was encrypted; this
   can be used to determine the private key needed to decrypt the JWE.

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

   This parameter has the same meaning, syntax, and processing rules as
   the "x5u" Header Parameter defined in Section 4.1.4 of [JWS], except
   that the X.509 public key certificate or certificate chain [RFC5280]
   contains the public key to which the JWE was encrypted; this can be
   used to determine the private key needed to decrypt the JWE.

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

   This parameter has the same meaning, syntax, and processing rules as
   the "x5t" Header Parameter defined in Section 4.1.5 of [JWS], except
   that certificate referenced by the thumbprint contains the public key
   to which the JWE was encrypted; this can be used to determine the
   private key needed to decrypt the JWE.

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

   This parameter has the same meaning, syntax, and processing rules as
   the "x5c" Header Parameter defined in Section 4.1.6 of [JWS], except
   that the X.509 public key certificate or certificate chain [RFC5280]
   contains the public key to which the JWE was encrypted; this can be
   used to determine the private key needed to decrypt the JWE.

   See Appendix B of [JWS] for an example "x5c" value.

4.1.9.  "kid" (Key ID) Header Parameter

   This parameter has the same meaning, syntax, and processing rules as
   the "kid" Header Parameter defined in Section 4.1.7 of [JWS], except
   that the key hint references the public key to which the JWE was
   encrypted; this can be used to determine the private key needed to
   decrypt the JWE.  This parameter allows originators to explicitly
   signal a change of key to JWE recipients.

4.1.10.  "typ" (Type) Header Parameter

   This parameter has the same meaning, syntax, and processing rules as
   the "typ" Header Parameter defined in Section 4.1.8 of [JWS], except
   that the type is of this complete JWE object.




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4.1.11.  "cty" (Content Type) Header Parameter

   This parameter has the same meaning, syntax, and processing rules as
   the "cty" Header Parameter defined in Section 4.1.9 of [JWS], except
   that the type is of the secured content (the payload).

4.1.12.  "crit" (Critical) Header Parameter

   This parameter has the same meaning, syntax, and processing rules as
   the "typ" Header Parameter defined in Section 4.1.8 of [JWS], except
   that the Header Parameters referenced are the JWE Header Parameters.

4.2.  Public Header Parameter Names

   Additional Header Parameter names can be defined by those using JWEs.
   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 [JWS] 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 JWEs.

4.3.  Private Header Parameter Names

   A producer and consumer of a JWE 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 JWEs

5.1.  Message Encryption

   The message encryption process is as follows.  The order of the steps
   is not significant in cases where there are no dependencies between
   the inputs and outputs of the steps.

   1.   Determine the Key Management Mode employed by the algorithm used
        to determine the Content Encryption Key (CEK) value.  (This is
        the algorithm recorded in the "alg" (algorithm) Header Parameter
        of the resulting JWE.)



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   2.   When Key Wrapping, Key Encryption, or Key Agreement with Key
        Wrapping are employed, generate a random Content Encryption Key
        (CEK) value.  See RFC 4086 [RFC4086] for considerations on
        generating random values.  The CEK MUST have a length equal to
        that required for the content encryption algorithm.

   3.   When Direct Key Agreement or Key Agreement with Key Wrapping are
        employed, use the key agreement algorithm to compute the value
        of the agreed upon key.  When Direct Key Agreement is employed,
        let the Content Encryption Key (CEK) be the agreed upon key.
        When Key Agreement with Key Wrapping is employed, the agreed
        upon key will be used to wrap the CEK.

   4.   When Key Wrapping, Key Encryption, or Key Agreement with Key
        Wrapping are employed, encrypt the CEK to the recipient and let
        the result be the JWE Encrypted Key.

   5.   Otherwise, when Direct Key Agreement or Direct Encryption are
        employed, let the JWE Encrypted Key be the empty octet sequence.

   6.   When Direct Encryption is employed, let the Content Encryption
        Key (CEK) be the shared symmetric key.

   7.   Compute the encoded key value BASE64URL(JWE Encrypted Key).

   8.   If the JWE JSON Serialization is being used, repeat this process
        for each recipient.

   9.   Generate a random JWE Initialization Vector of the correct size
        for the content encryption algorithm (if required for the
        algorithm); otherwise, let the JWE Initialization Vector be the
        empty octet sequence.

   10.  Compute the encoded initialization vector value BASE64URL(JWE
        Initialization Vector).

   11.  Compress the Plaintext if a "zip" parameter was included.

   12.  Serialize the (compressed) Plaintext into an octet sequence M.

   13.  Create a JWE Header containing the encryption parameters used.
        Note that white space is explicitly allowed in the
        representation and no canonicalization need be performed before
        encoding.

   14.  Compute the encoded header value BASE64URL(UTF8(JWE Protected
        Header)).  If the JWE Protected Header is not present (which can
        only happen when using the JWE JSON Serialization and no



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        "protected" member is present), let this value be the empty
        string.

   15.  Let the Additional Authenticated Data encryption parameter be
        ASCII(BASE64URL(UTF8(JWE Protected Header))).  However if a JWE
        AAD value is present when using the JWE JSON Serialization,
        instead let the Additional Authenticated Data encryption
        parameter be ASCII(BASE64URL(UTF8(JWE Protected Header)) || '.'
        || BASE64URL(JWE AAD)).

   16.  Encrypt M using the CEK, the JWE Initialization Vector, and the
        Additional Authenticated Data value using the specified content
        encryption algorithm to create the JWE Ciphertext value and the
        JWE Authentication Tag (which is the Authentication Tag output
        from the encryption operation).

   17.  Compute the encoded ciphertext value BASE64URL(JWE Ciphertext).

   18.  Compute the encoded authentication tag value BASE64URL(JWE
        Authentication Tag).

   19.  The five encoded values are used in both the JWE Compact
        Serialization and the JWE JSON Serialization representations.

   20.  If a JWE AAD value is present, compute the encoded AAD value
        BASE64URL(JWE AAD).

   21.  Create the desired serialized output.  The Compact Serialization
        of this result is the string BASE64URL(UTF8(JWE Protected
        Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' ||
        BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE
        Ciphertext) || '.' || BASE64URL(JWE Authentication Tag).  The
        JWE JSON Serialization is described in Section 7.2.

5.2.  Message Decryption

   The message decryption process is the reverse of the encryption
   process.  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 these steps fails, the encrypted content cannot be
   validated.

   It is an application decision which recipients' encrypted content
   must successfully validate for the JWE to be accepted.  In some
   cases, encrypted content for all recipients must successfully
   validate or the JWE will be rejected.  In other cases, only the
   encrypted content for a single recipient needs to be successfully
   validated.  However, in all cases, the encrypted content for at least



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   one recipient MUST successfully validate or the JWE MUST be rejected.

   1.   Parse the JWE representation to extract the serialized values
        for the components of the JWE -- when using the JWE Compact
        Serialization, the base64url encoded representations of the JWE
        Protected Header, the JWE Encrypted Key, the JWE Initialization
        Vector, the JWE Ciphertext, and the JWE Authentication Tag, and
        when using the JWE JSON Serialization, also the base64url
        encoded representation of the JWE AAD and the unencoded JWE
        Shared Unprotected Header and JWE Per-Recipient Unprotected
        Header values.  When using the JWE Compact Serialization, the
        JWE Protected Header, the JWE Encrypted Key, the JWE
        Initialization Vector, the JWE Ciphertext, and the JWE
        Authentication Tag are represented as base64url encoded values
        in that order, separated by four period ('.') characters.  The
        JWE JSON Serialization is described in Section 7.2.

   2.   The encoded representations of the JWE Protected Header, the JWE
        Encrypted Key, the JWE Initialization Vector, the JWE
        Ciphertext, the JWE Authentication Tag, and the JWE AAD MUST be
        successfully base64url decoded following the restriction that no
        padding characters have been used.

   3.   The resulting UTF8 encoded JWE Protected Header MUST be a
        completely valid JSON object conforming to RFC 4627 [RFC4627].

   4.   If using the JWE Compact Serialization, let the JWE Header be
        the JWE Protected Header; otherwise, when using the JWE JSON
        Serialization, let the JWE Header be the union of the members of
        the JWE Protected Header, the JWE Shared Unprotected Header and
        the corresponding JWE Per-Recipient Unprotected Header, all of
        which must be completely valid JSON objects.

   5.   The resulting JWE Header MUST NOT contain duplicate Header
        Parameter names.  When using the JWE JSON Serialization, this
        restriction includes that the same Header Parameter name also
        MUST NOT occur in distinct JSON Text Object values that together
        comprise the JWE Header.

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

   7.   Determine the Key Management Mode employed by the algorithm
        specified by the "alg" (algorithm) Header Parameter.





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   8.   Verify that the JWE uses a key known to the recipient.

   9.   When Direct Key Agreement or Key Agreement with Key Wrapping are
        employed, use the key agreement algorithm to compute the value
        of the agreed upon key.  When Direct Key Agreement is employed,
        let the Content Encryption Key (CEK) be the agreed upon key.
        When Key Agreement with Key Wrapping is employed, the agreed
        upon key will be used to decrypt the JWE Encrypted Key.

   10.  When Key Wrapping, Key Encryption, or Key Agreement with Key
        Wrapping are employed, decrypt the JWE Encrypted Key to produce
        the Content Encryption Key (CEK).  The CEK MUST have a length
        equal to that required for the content encryption algorithm.
        Note that when there are multiple recipients, each recipient
        will only be able decrypt any JWE Encrypted Key values that were
        encrypted to a key in that recipient's possession.  It is
        therefore normal to only be able to decrypt one of the per-
        recipient JWE Encrypted Key values to obtain the CEK value.  To
        mitigate the attacks described in RFC 3218 [RFC3218], the
        recipient MUST NOT distinguish between format, padding, and
        length errors of encrypted keys.  It is strongly recommended, in
        the event of receiving an improperly formatted key, that the
        receiver substitute a randomly generated CEK and proceed to the
        next step, to mitigate timing attacks.

   11.  Otherwise, when Direct Key Agreement or Direct Encryption are
        employed, verify that the JWE Encrypted Key value is empty octet
        sequence.

   12.  When Direct Encryption is employed, let the Content Encryption
        Key (CEK) be the shared symmetric key.

   13.  If the JWE JSON Serialization is being used, repeat this process
        for each recipient contained in the representation until the CEK
        value has been determined.

   14.  Let the Additional Authenticated Data encryption parameter be
        ASCII(BASE64URL(UTF8(JWE Protected Header))).  However if a JWE
        AAD value is present when using the JWE JSON Serialization,
        instead let the Additional Authenticated Data encryption
        parameter be ASCII(BASE64URL(UTF8(JWE Protected Header)) || '.'
        || BASE64URL(JWE AAD)).

   15.  Decrypt the JWE Ciphertext using the CEK, the JWE Initialization
        Vector, the Additional Authenticated Data value, and the JWE
        Authentication Tag (which is the Authentication Tag input to the
        calculation) using the specified content encryption algorithm,
        returning the decrypted plaintext and verifying the JWE



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        Authentication Tag in the manner specified for the algorithm,
        rejecting the input without emitting any decrypted output if the
        JWE Authentication Tag is incorrect.

   16.  Uncompress the decrypted plaintext if a "zip" parameter was
        included.

   17.  Output the resulting Plaintext.

5.3.  String Comparison Rules

   The string comparison rules for this specification are the same as
   those defined in Section 5.3 of [JWS].


6.  Key Identification

   The key identification methods for this specification are the same as
   those defined in Section 6 of [JWS], except that the key being
   identified is the public key to which the JWE was encrypted.


7.  Serializations

   JWE objects use one of two serializations, the JWE Compact
   Serialization or the JWE JSON Serialization.  For general-purpose
   implementations, both the JWE Compact Serialization and JWE JSON
   Serialization support for the single recipient case are mandatory to
   implement; support for multiple recipients is OPTIONAL.  Special-
   purpose implementations are permitted to implement only a single
   serialization, if that meets the needs of the targeted use cases.

7.1.  JWE Compact Serialization

   The JWE Compact Serialization represents encrypted content as a
   compact URL-safe string.  This string is BASE64URL(UTF8(JWE Protected
   Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' ||
   BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE
   Ciphertext) || '.' || BASE64URL(JWE Authentication Tag).  Only one
   recipient is supported by the JWE Compact Serialization.

7.2.  JWE JSON Serialization

   The JWE JSON Serialization represents encrypted content as a JSON
   object.  Unlike the JWE Compact Serialization, content using the JWE
   JSON Serialization can be encrypted to more than one recipient.

   The representation is closely related to that used in the JWE Compact



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   Serialization, with the following differences for the JWE JSON
   Serialization:

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

   o  The value BASE64URL(UTF8(JWE Protected Header)), if non-empty, is
      stored in the "protected" member.

   o  The value BASE64URL(UTF8(JWE Shared Unprotected Header)), if non-
      empty, is stored in the "unprotected" member.

   o  The value BASE64URL(JWE Initialization Vector), if non-empty, is
      stored in the "iv" member.

   o  The value BASE64URL(JWE Ciphertext)is stored in the "ciphertext"
      member.

   o  The value BASE64URL(JWE Authentication Tag), if non-empty, is
      stored in the "tag" member.

   o  The JWE can be encrypted to multiple recipients, rather than just
      one.  A JSON array in the "recipients" member is used to hold
      values that are specific to a particular recipient, with one array
      element per recipient represented.  These array elements are JSON
      objects.

   o  Each value BASE64URL(JWE Encrypted Key), if non-empty, is stored
      in the "encrypted_key" member of a JSON object that is an element
      of the "recipients" array.

   o  Some Header Parameter values, such as the "alg" value and
      parameters used for selecting keys, can also differ for different
      recipient computations.  JWE Per-Recipient Unprotected Header
      values, if present, are stored in the "header" members of the same
      JSON objects that are elements of the "recipients" array.

   o  Some Header Parameters, including the "alg" parameter, can be
      shared among all recipient computations.  Header Parameters in the
      JWE Protected Header and JWE Shared Unprotected Header values are
      shared among all recipients.

   o  Not all Header Parameters are integrity protected.  The shared
      Header Parameters in the JWE Protected Header value member are
      integrity protected, and are base64url encoded for transmission.
      The per-recipient Header Parameters in the JWE Per-Recipient



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      Unprotected Header values and the shared Header Parameters in the
      JWE Shared Unprotected Header value are not integrity protected.
      These JSON Text Objects containing Header Parameters that are not
      integrity protected are not base64url encoded.

   o  The Header Parameter values used when creating or validating per-
      recipient Ciphertext and Authentication Tag values are the union
      of the three sets of Header Parameter values that may be present:
      (1) the JWE Protected Header values represented in the "protected"
      member, (2) the JWE Shared Unprotected Header values represented
      in the "unprotected" member, and (3) the JWE Per-Recipient
      Unprotected Header values represented in the "header" member of
      the recipient's array element.  The union of these sets of Header
      Parameters comprises the JWE Header.  The Header Parameter names
      in the three locations MUST be disjoint.

   o  A JWE AAD value can be included to supply a base64url encoded
      value to be integrity protected but not encrypted.  (Note that
      this can also be achieved when using either serialization by
      including the AAD value as a protected Header Parameter value, but
      at the cost of the value being double base64url encoded.)  If a
      JWE AAD value is present, the value BASE64URL(JWE AAD)) is stored
      in the "aad" member.

   o  The "recipients" array MUST always be present, even if the array
      elements contain only the empty JSON object "{}" (which can happen
      when all Header Parameter values are shared between all recipients
      and when no encrypted key is used, such as when doing Direct
      Encryption).

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

     {"protected":<integrity-protected shared header contents>",
      "unprotected":<non-integrity-protected shared header contents>",
      "recipients":[
       {"header":"<per-recipient unprotected header 1 contents>",
        "encrypted_key":"<encrypted key 1 contents>"},
       ...
       {"header":"<per-recipient unprotected header N contents>",
        "encrypted_key":"<encrypted key N contents>"}],
      "aad":"<additional authenticated data contents>",
      "iv":"<initialization vector contents>",
      "ciphertext":"<ciphertext contents>",
      "tag":"<authentication tag contents>"
     }

   Of these members, only the "ciphertext" member MUST be present.  The
   "iv", "tag", and "encrypted_key" members MUST be present when



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   corresponding JWE Initialization Vector, JWE Authentication Tag, and
   JWE Encrypted Key values are non-empty.  The "recipients" member MUST
   be present when any "header" or "encrypted_key" members are needed
   for recipients.  At least one of the "header", "protected", and
   "unprotected" members MUST be present so that "alg" and "enc" Header
   Parameter values are conveyed for each recipient computation.

   The contents of the JWE Encrypted Key, JWE Initialization Vector, JWE
   Ciphertext, and JWE Authentication Tag values are exactly as defined
   in the rest of this specification.  They are interpreted and
   validated in the same manner, with each corresponding JWE Encrypted
   Key, JWE Initialization Vector, JWE Ciphertext, JWE Authentication
   Tag, and set of Header Parameter values being created and validated
   together.  The JWE Header values used are the union of the Header
   Parameters in the JWE Protected Header, JWE Shared Unprotected
   Header, and corresponding JWE Per-Recipient Unprotected Header
   values, as described earlier.

   Each JWE Encrypted Key value is computed using the parameters of the
   corresponding JWE Header value in the same manner as for the JWE
   Compact Serialization.  This has the desirable property that each JWE
   Encrypted Key value in the "recipients" array is identical to the
   value that would have been computed for the same parameter in the JWE
   Compact Serialization.  Likewise, the JWE Ciphertext and JWE
   Authentication Tag values match those produced for the JWE Compact
   Serialization, provided that the JWE Protected Header value (which
   represents the integrity-protected Header Parameter values) matches
   that used in the JWE Compact Serialization.

   All recipients use the same JWE Protected Header, JWE Initialization
   Vector, JWE Ciphertext, and JWE Authentication Tag values, resulting
   in potentially significant space savings if the message is large.
   Therefore, all Header Parameters that specify the treatment of the
   Plaintext value MUST be the same for all recipients.  This primarily
   means that the "enc" (encryption method) Header Parameter value in
   the JWE Header for each recipient and any parameters of that
   algorithm MUST be the same.

   See Appendix A.4 for an example of computing a JWE using the JWE JSON
   Serialization.


8.  Distinguishing Between JWS and JWE Objects

   There are several ways of distinguishing whether an object is a JWS
   or JWE object.  All these methods will yield the same result for all
   legal input values.




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   o  If the object is using the JWS Compact Serialization or the JWE
      Compact Serialization, the number of base64url encoded segments
      separated by period ('.') characters differs for JWSs and JWEs.
      JWSs have three segments separated by two period ('.') characters.
      JWEs have five segments separated by four period ('.') characters.

   o  If the object is using the JWS JSON Serialization or the JWE JSON
      Serialization, the members used will be different.  JWSs have a
      "signatures" member and JWEs do not.  JWEs have a "recipients"
      member and JWSs do not.

   o  A JWS Header can be distinguished from a JWE header by examining
      the "alg" (algorithm) Header Parameter value.  If the value
      represents a digital signature or MAC algorithm, or is the value
      "none", it is for a JWS; if it represents a Key Encryption, Key
      Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping,
      or Direct Encryption algorithm, it is for a JWE.

   o  A JWS Header can also be distinguished from a JWE header by
      determining whether an "enc" (encryption method) member exists.
      If the "enc" member exists, it is a JWE; otherwise, it is a JWS.


9.  IANA Considerations

9.1.  JWE Header Parameter Names Registration

   This specification registers the Header Parameter names defined in
   Section 4.1 in the IANA JSON Web Signature and Encryption Header
   Parameters registry defined in [JWS].

9.1.1.  Registry Contents

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

   o  Header Parameter Name: "enc"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.2 of [[ this document ]]

   o  Header Parameter Name: "zip"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG





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   o  Specification Document(s): Section 4.1.3 of [[ this document ]]

   o  Header Parameter Name: "jku"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.4 of [[ this document ]]

   o  Header Parameter Name: "jwk"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification document(s): Section 4.1.5 of [[ this document ]]

   o  Header Parameter Name: "x5u"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.6 of [[ this document ]]

   o  Header Parameter Name: "x5t"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.7 of [[ this document ]]

   o  Header Parameter Name: "x5c"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

   o  Header Parameter Name: "kid"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.9 of [[ this document ]]

   o  Header Parameter Name: "typ"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.10 of [[ this document ]]

   o  Header Parameter Name: "cty"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.11 of [[ this document ]]

   o  Header Parameter Name: "crit"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IESG
   o  Specification Document(s): Section 4.1.12 of [[ this document ]]





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10.  Security Considerations

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

   All the security considerations in the JWS specification also apply
   to this specification.  Likewise, all the security considerations in
   XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313] also apply, other
   than those that are XML specific.

   When decrypting, particular care must be taken not to allow the JWE
   recipient to be used as an oracle for decrypting messages.  RFC 3218
   [RFC3218] should be consulted for specific countermeasures to attacks
   on RSAES-PKCS1-V1_5.  An attacker might modify the contents of the
   "alg" parameter from "RSA-OAEP" to "RSA1_5" in order to generate a
   formatting error that can be detected and used to recover the CEK
   even if RSAES OAEP was used to encrypt the CEK.  It is therefore
   particularly important to report all formatting errors to the CEK,
   Additional Authenticated Data, or ciphertext as a single error when
   the encrypted content is rejected.


11.  References

11.1.  Normative References

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

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

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

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", draft-ietf-jose-json-web-signature (work
              in progress), October 2013.

   [RFC1951]  Deutsch, P., "DEFLATE Compressed Data Format Specification
              version 1.3", RFC 1951, May 1996.



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

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

   [RFC4086]  Eastlake, D., Schiller, J., and S. Crocker, "Randomness
              Requirements for Security", BCP 106, RFC 4086, June 2005.

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

   [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.

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

   [W3C.CR-xmlenc-core1-20120313]
              Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch,
              "XML Encryption Syntax and Processing Version 1.1", World
              Wide Web Consortium CR CR-xmlenc-core1-20120313,
              March 2012,
              <http://www.w3.org/TR/2012/CR-xmlenc-core1-20120313>.

11.2.  Informative References

   [I-D.mcgrew-aead-aes-cbc-hmac-sha2]
              McGrew, D. and K. Paterson, "Authenticated Encryption with
              AES-CBC and HMAC-SHA",
              draft-mcgrew-aead-aes-cbc-hmac-sha2-01 (work in progress),
              October 2012.

   [I-D.rescorla-jsms]
              Rescorla, E. and J. Hildebrand, "JavaScript Message
              Security Format", draft-rescorla-jsms-00 (work in
              progress), March 2011.

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

   [RFC3218]  Rescorla, E., "Preventing the Million Message Attack on
              Cryptographic Message Syntax", RFC 3218, January 2002.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,



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              RFC 5652, September 2009.


Appendix A.  JWE Examples

   This section provides examples of JWE computations.

A.1.  Example JWE using RSAES OAEP and AES GCM

   This example encrypts the plaintext "The true sign of intelligence is
   not knowledge but imagination." to the recipient using RSAES OAEP for
   key encryption and AES GCM for content encryption.  The
   representation of this plaintext is:

   [84, 104, 101, 32, 116, 114, 117, 101, 32, 115, 105, 103, 110, 32,
   111, 102, 32, 105, 110, 116, 101, 108, 108, 105, 103, 101, 110, 99,
   101, 32, 105, 115, 32, 110, 111, 116, 32, 107, 110, 111, 119, 108,
   101, 100, 103, 101, 32, 98, 117, 116, 32, 105, 109, 97, 103, 105,
   110, 97, 116, 105, 111, 110, 46]

A.1.1.  JWE Header

   The following example JWE Protected Header declares that:

   o  the Content Encryption Key is encrypted to the recipient using the
      RSAES OAEP algorithm to produce the JWE Encrypted Key and

   o  the Plaintext is encrypted using the AES GCM algorithm with a 256
      bit key to produce the Ciphertext.


     {"alg":"RSA-OAEP","enc":"A256GCM"}

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

     eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

A.1.2.  Content Encryption Key (CEK)

   Generate a 256 bit random Content Encryption Key (CEK).  In this
   example, the value is:

   [177, 161, 244, 128, 84, 143, 225, 115, 63, 180, 3, 255, 107, 154,
   212, 246, 138, 7, 110, 91, 112, 46, 34, 105, 47, 130, 203, 46, 122,
   234, 64, 252]





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A.1.3.  Key Encryption

   Encrypt the CEK with the recipient's public key using the RSAES OAEP
   algorithm to produce the JWE Encrypted Key. This example uses the RSA
   key represented in JSON Web Key [JWK] format below (with line breaks
   for display purposes only):

     {"kty":"RSA",
      "n":"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW
           cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S
           psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a
           sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS
           tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj
           YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw",
      "e":"AQAB",
      "d":"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N
           WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9
           3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk
           qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl
           t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd
           VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ"
     }

   The resulting JWE Encrypted Key value is:

   [56, 163, 154, 192, 58, 53, 222, 4, 105, 218, 136, 218, 29, 94, 203,
   22, 150, 92, 129, 94, 211, 232, 53, 89, 41, 60, 138, 56, 196, 216,
   82, 98, 168, 76, 37, 73, 70, 7, 36, 8, 191, 100, 136, 196, 244, 220,
   145, 158, 138, 155, 4, 117, 141, 230, 199, 247, 173, 45, 182, 214,
   74, 177, 107, 211, 153, 11, 205, 196, 171, 226, 162, 128, 171, 182,
   13, 237, 239, 99, 193, 4, 91, 219, 121, 223, 107, 167, 61, 119, 228,
   173, 156, 137, 134, 200, 80, 219, 74, 253, 56, 185, 91, 177, 34, 158,
   89, 154, 205, 96, 55, 18, 138, 43, 96, 218, 215, 128, 124, 75, 138,
   243, 85, 25, 109, 117, 140, 26, 155, 249, 67, 167, 149, 231, 100, 6,
   41, 65, 214, 251, 232, 87, 72, 40, 182, 149, 154, 168, 31, 193, 126,
   215, 89, 28, 111, 219, 125, 182, 139, 235, 195, 197, 23, 234, 55, 58,
   63, 180, 68, 202, 206, 149, 75, 205, 248, 176, 67, 39, 178, 60, 98,
   193, 32, 238, 122, 96, 158, 222, 57, 183, 111, 210, 55, 188, 215,
   206, 180, 166, 150, 166, 106, 250, 55, 229, 72, 40, 69, 214, 216,
   104, 23, 40, 135, 212, 28, 127, 41, 80, 175, 174, 168, 115, 171, 197,
   89, 116, 92, 103, 246, 83, 216, 182, 176, 84, 37, 147, 35, 45, 219,
   172, 99, 226, 233, 73, 37, 124, 42, 72, 49, 242, 35, 127, 184, 134,
   117, 114, 135, 206]

   Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
   this value (with line breaks for display purposes only):





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     OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
     ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
     Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
     mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
     1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
     6UklfCpIMfIjf7iGdXKHzg

A.1.4.  Initialization Vector

   Generate a random 96 bit JWE Initialization Vector.  In this example,
   the value is:

   [227, 197, 117, 252, 2, 219, 233, 68, 180, 225, 77, 219]

   Encoding this JWE Initialization Vector as BASE64URL(JWE
   Initialization Vector) gives this value:

     48V1_ALb6US04U3b

A.1.5.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be
   ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
   116, 84, 48, 70, 70, 85, 67, 73, 115, 73, 109, 86, 117, 89, 121, 73,
   54, 73, 107, 69, 121, 78, 84, 90, 72, 81, 48, 48, 105, 102, 81]

A.1.6.  Content Encryption

   Encrypt the Plaintext with AES GCM using the CEK as the encryption
   key, the JWE Initialization Vector, and the Additional Authenticated
   Data value above, requesting a 128 bit Authentication Tag output.
   The resulting Ciphertext is:

   [229, 236, 166, 241, 53, 191, 115, 196, 174, 43, 73, 109, 39, 122,
   233, 96, 140, 206, 120, 52, 51, 237, 48, 11, 190, 219, 186, 80, 111,
   104, 50, 142, 47, 167, 59, 61, 181, 127, 196, 21, 40, 82, 242, 32,
   123, 143, 168, 226, 73, 216, 176, 144, 138, 247, 106, 60, 16, 205,
   160, 109, 64, 63, 192]

   The resulting Authentication Tag value is:

   [92, 80, 104, 49, 133, 25, 161, 215, 173, 101, 219, 211, 136, 91,
   210, 145]

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



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     5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
     SdiwkIr3ajwQzaBtQD_A

   Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
   Tag) gives this value:

     XFBoMYUZodetZdvTiFvSkQ

A.1.7.  Complete Representation

   Assemble the final representation: The Compact Serialization of this
   result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
   BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
   Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
   Authentication Tag).

   The final result in this example (with line breaks for display
   purposes only) is:

     eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
     OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
     ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
     Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
     mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
     1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
     6UklfCpIMfIjf7iGdXKHzg.
     48V1_ALb6US04U3b.
     5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
     SdiwkIr3ajwQzaBtQD_A.
     XFBoMYUZodetZdvTiFvSkQ

A.1.8.  Validation

   This example illustrates the process of creating a JWE with RSAES
   OAEP for key encryption and AES GCM for content encryption.  These
   results can be used to validate JWE decryption implementations for
   these algorithms.  Note that since the RSAES OAEP computation
   includes random values, the encryption results above will not be
   completely reproducible.  However, since the AES GCM computation is
   deterministic, the JWE Encrypted Ciphertext values will be the same
   for all encryptions performed using these inputs.

A.2.  Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256

   This example encrypts the plaintext "Live long and prosper." to the
   recipient using RSAES-PKCS1-V1_5 for key encryption and
   AES_128_CBC_HMAC_SHA_256 for content encryption.  The representation
   of this plaintext is:



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   [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
   112, 114, 111, 115, 112, 101, 114, 46]

A.2.1.  JWE Header

   The following example JWE Protected Header declares that:

   o  the Content Encryption Key is encrypted to the recipient using the
      RSAES-PKCS1-V1_5 algorithm to produce the JWE Encrypted Key and

   o  the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
      algorithm to produce the Ciphertext.


     {"alg":"RSA1_5","enc":"A128CBC-HS256"}

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

     eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.2.2.  Content Encryption Key (CEK)

   Generate a 256 bit random Content Encryption Key (CEK).  In this
   example, the key value is:

   [4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
   206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
   44, 207]

A.2.3.  Key Encryption

   Encrypt the CEK with the recipient's public key using the RSAES-
   PKCS1-V1_5 algorithm to produce the JWE Encrypted Key. This example
   uses the RSA key represented in JSON Web Key [JWK] format below (with
   line breaks for display purposes only):















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     {"kty":"RSA",
      "n":"sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl
           UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre
           cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_
           7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI
           Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU
           7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw",
      "e":"AQAB",
      "d":"VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq
           1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry
           nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_
           0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj
           -VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj
           T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ"
     }

   The resulting JWE Encrypted Key value is:

   [80, 104, 72, 58, 11, 130, 236, 139, 132, 189, 255, 205, 61, 86, 151,
   176, 99, 40, 44, 233, 176, 189, 205, 70, 202, 169, 72, 40, 226, 181,
   156, 223, 120, 156, 115, 232, 150, 209, 145, 133, 104, 112, 237, 156,
   116, 250, 65, 102, 212, 210, 103, 240, 177, 61, 93, 40, 71, 231, 223,
   226, 240, 157, 15, 31, 150, 89, 200, 215, 198, 203, 108, 70, 117, 66,
   212, 238, 193, 205, 23, 161, 169, 218, 243, 203, 128, 214, 127, 253,
   215, 139, 43, 17, 135, 103, 179, 220, 28, 2, 212, 206, 131, 158, 128,
   66, 62, 240, 78, 186, 141, 125, 132, 227, 60, 137, 43, 31, 152, 199,
   54, 72, 34, 212, 115, 11, 152, 101, 70, 42, 219, 233, 142, 66, 151,
   250, 126, 146, 141, 216, 190, 73, 50, 177, 146, 5, 52, 247, 28, 197,
   21, 59, 170, 247, 181, 89, 131, 241, 169, 182, 246, 99, 15, 36, 102,
   166, 182, 172, 197, 136, 230, 120, 60, 58, 219, 243, 149, 94, 222,
   150, 154, 194, 110, 227, 225, 112, 39, 89, 233, 112, 207, 211, 241,
   124, 174, 69, 221, 179, 107, 196, 225, 127, 167, 112, 226, 12, 242,
   16, 24, 28, 120, 182, 244, 213, 244, 153, 194, 162, 69, 160, 244,
   248, 63, 165, 141, 4, 207, 249, 193, 79, 131, 0, 169, 233, 127, 167,
   101, 151, 125, 56, 112, 111, 248, 29, 232, 90, 29, 147, 110, 169,
   146, 114, 165, 204, 71, 136, 41, 252]

   Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
   this value (with line breaks for display purposes only):

     UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm
     1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc
     HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF
     NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8
     rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv
     -B3oWh2TbqmScqXMR4gp_A





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A.2.4.  Initialization Vector

   Generate a random 128 bit JWE Initialization Vector.  In this
   example, the value is:

   [3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
   101]

   Encoding this JWE Initialization Vector as BASE64URL(JWE
   Initialization Vector) gives this value:

     AxY8DCtDaGlsbGljb3RoZQ

A.2.5.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be
   ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
   120, 88, 122, 85, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105,
   74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85,
   50, 73, 110, 48]

A.2.6.  Content Encryption

   Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as
   the encryption key, the JWE Initialization Vector, and the Additional
   Authenticated Data value above.  The steps for doing this using the
   values from Appendix A.3 are detailed in Appendix B.  The resulting
   Ciphertext is:

   [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
   75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
   112, 56, 102]

   The resulting Authentication Tag value is:

   [246, 17, 244, 190, 4, 95, 98, 3, 231, 0, 115, 157, 242, 203, 100,
   191]

   Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
   value:

     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

   Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
   Tag) gives this value:




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     9hH0vgRfYgPnAHOd8stkvw

A.2.7.  Complete Representation

   Assemble the final representation: The Compact Serialization of this
   result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
   BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
   Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
   Authentication Tag).

   The final result in this example (with line breaks for display
   purposes only) is:

     eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
     UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm
     1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc
     HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF
     NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8
     rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv
     -B3oWh2TbqmScqXMR4gp_A.
     AxY8DCtDaGlsbGljb3RoZQ.
     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
     9hH0vgRfYgPnAHOd8stkvw

A.2.8.  Validation

   This example illustrates the process of creating a JWE with RSAES-
   PKCS1-V1_5 for key encryption and AES_CBC_HMAC_SHA2 for content
   encryption.  These results can be used to validate JWE decryption
   implementations for these algorithms.  Note that since the RSAES-
   PKCS1-V1_5 computation includes random values, the encryption results
   above will not be completely reproducible.  However, since the AES
   CBC computation is deterministic, the JWE Encrypted Ciphertext values
   will be the same for all encryptions performed using these inputs.

A.3.  Example JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

   This example encrypts the plaintext "Live long and prosper." to the
   recipient using AES Key Wrap for key encryption and AES GCM for
   content encryption.  The representation of this plaintext is:

   [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
   112, 114, 111, 115, 112, 101, 114, 46]

A.3.1.  JWE Header

   The following example JWE Protected Header declares that:




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   o  the Content Encryption Key is encrypted to the recipient using the
      AES Key Wrap algorithm with a 128 bit key to produce the JWE
      Encrypted Key and

   o  the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
      algorithm to produce the Ciphertext.


     {"alg":"A128KW","enc":"A128CBC-HS256"}

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

     eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.3.2.  Content Encryption Key (CEK)

   Generate a 256 bit random Content Encryption Key (CEK).  In this
   example, the value is:

   [4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
   206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
   44, 207]

A.3.3.  Key Encryption

   Encrypt the CEK with the shared symmetric key using the AES Key Wrap
   algorithm to produce the JWE Encrypted Key. This example uses the
   symmetric key represented in JSON Web Key [JWK] format below:

     {"kty":"oct",
      "k":"GawgguFyGrWKav7AX4VKUg"
     }

   The resulting JWE Encrypted Key value is:

   [232, 160, 123, 211, 183, 76, 245, 132, 200, 128, 123, 75, 190, 216,
   22, 67, 201, 138, 193, 186, 9, 91, 122, 31, 246, 90, 28, 139, 57, 3,
   76, 124, 193, 11, 98, 37, 173, 61, 104, 57]

   Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
   this value:

     6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ







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A.3.4.  Initialization Vector

   Generate a random 128 bit JWE Initialization Vector.  In this
   example, the value is:

   [3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
   101]

   Encoding this JWE Initialization Vector as BASE64URL(JWE
   Initialization Vector) gives this value:

     AxY8DCtDaGlsbGljb3RoZQ

A.3.5.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be
   ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
   83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
   77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
   110, 48]

A.3.6.  Content Encryption

   Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as
   the encryption key, the JWE Initialization Vector, and the Additional
   Authenticated Data value above.  The steps for doing this using the
   values from this example are detailed in Appendix B.  The resulting
   Ciphertext is:

   [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
   75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
   112, 56, 102]

   The resulting Authentication Tag value is:

   [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
   194, 85]

   Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
   value:

     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

   Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
   Tag) gives this value:




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     U0m_YmjN04DJvceFICbCVQ

A.3.7.  Complete Representation

   Assemble the final representation: The Compact Serialization of this
   result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
   BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
   Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
   Authentication Tag).

   The final result in this example (with line breaks for display
   purposes only) is:

     eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
     6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.
     AxY8DCtDaGlsbGljb3RoZQ.
     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
     U0m_YmjN04DJvceFICbCVQ

A.3.8.  Validation

   This example illustrates the process of creating a JWE with AES Key
   Wrap for key encryption and AES GCM for content encryption.  These
   results can be used to validate JWE decryption implementations for
   these algorithms.  Also, since both the AES Key Wrap and AES GCM
   computations are deterministic, the resulting JWE value will be the
   same for all encryptions performed using these inputs.  Since the
   computation is reproducible, these results can also be used to
   validate JWE encryption implementations for these algorithms.

A.4.  Example JWE using JWE JSON Serialization

   This section contains an example using the JWE JSON Serialization.
   This example demonstrates the capability for encrypting the same
   plaintext to multiple recipients.

   Two recipients are present in this example.  The algorithm and key
   used for the first recipient are the same as that used in
   Appendix A.2.  The algorithm and key used for the second recipient
   are the same as that used in Appendix A.3.  The resulting JWE
   Encrypted Key values are therefore the same; those computations are
   not repeated here.

   The Plaintext, the Content Encryption Key (CEK), Initialization
   Vector, and JWE Protected Header are shared by all recipients (which
   must be the case, since the Ciphertext and Authentication Tag are
   also shared).




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A.4.1.  JWE Per-Recipient Unprotected Headers

   The first recipient uses the RSAES-PKCS1-V1_5 algorithm to encrypt
   the Content Encryption Key (CEK).  The second uses AES Key Wrap to
   encrypt the CEK.  Key ID values are supplied for both keys.  The two
   per-recipient header values used to represent these algorithms and
   Key IDs are:

     {"alg":"RSA1_5","kid":"2011-04-29"}

   and

     {"alg":"A128KW","kid":"7"}

A.4.2.  JWE Protected Header

   The Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
   algorithm to produce the common JWE Ciphertext and JWE Authentication
   Tag values.  The JWE Protected Header value representing this is:

     {"enc":"A128CBC-HS256"}

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

     eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.4.3.  JWE Unprotected Header

   This JWE uses the "jku" Header Parameter to reference a JWK Set. This
   is represented in the following JWE Unprotected Header value as:

     {"jku":"https://server.example.com/keys.jwks"}

A.4.4.  Complete JWE Header Values

   Combining the per-recipient, protected, and unprotected header values
   supplied, the JWE Header values used for the first and second
   recipient respectively are:

     {"alg":"RSA1_5",
      "kid":"2011-04-29",
      "enc":"A128CBC-HS256",
      "jku":"https://server.example.com/keys.jwks"}

   and





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     {"alg":"A128KW",
      "kid":"7",
      "enc":"A128CBC-HS256",
      "jku":"https://server.example.com/keys.jwks"}

A.4.5.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be
   ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:

   [101, 121, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73,
   52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48]

A.4.6.  Content Encryption

   Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as
   the encryption key, the JWE Initialization Vector, and the Additional
   Authenticated Data value above.  The steps for doing this using the
   values from Appendix A.3 are detailed in Appendix B.  The resulting
   Ciphertext is:

   [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
   75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
   112, 56, 102]

   The resulting Authentication Tag value is:

   [51, 63, 149, 60, 252, 148, 225, 25, 92, 185, 139, 245, 35, 2, 47,
   207]

   Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
   value:

     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

   Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
   Tag) gives this value:

     Mz-VPPyU4RlcuYv1IwIvzw

A.4.7.  Complete JWE JSON Serialization Representation

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







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     {"protected":
       "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
      "unprotected":
       {"jku":"https://server.example.com/keys.jwks"},
      "recipients":[
       {"header":
         {"alg":"RSA1_5"},
        "encrypted_key":
         "UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-
          kFm1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKx
          GHZ7PcHALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3
          YvkkysZIFNPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPh
          cCdZ6XDP0_F8rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPg
          wCp6X-nZZd9OHBv-B3oWh2TbqmScqXMR4gp_A"},
       {"header":
         {"alg":"A128KW"},
        "encrypted_key":
         "6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"}],
      "iv":
       "AxY8DCtDaGlsbGljb3RoZQ",
      "ciphertext":
       "KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
      "tag":
       "Mz-VPPyU4RlcuYv1IwIvzw"
     }


Appendix B.  Example AES_128_CBC_HMAC_SHA_256 Computation

   This example shows the steps in the AES_128_CBC_HMAC_SHA_256
   authenticated encryption computation using the values from the
   example in Appendix A.3.  As described where this algorithm is
   defined in Sections 4.8 and 4.8.3 of JWA, the AES_CBC_HMAC_SHA2
   family of algorithms are implemented using Advanced Encryption
   Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5
   padding to perform the encryption and an HMAC SHA-2 function to
   perform the integrity calculation - in this case, HMAC SHA-256.

B.1.  Extract MAC_KEY and ENC_KEY from Key

   The 256 bit AES_128_CBC_HMAC_SHA_256 key K used in this example is:

   [4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
   206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
   44, 207]

   Use the first 128 bits of this key as the HMAC SHA-256 key MAC_KEY,
   which is:



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   [4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
   206]

   Use the last 128 bits of this key as the AES CBC key ENC_KEY, which
   is:

   [107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156, 44,
   207]

   Note that the MAC key comes before the encryption key in the input
   key K; this is in the opposite order of the algorithm names in the
   identifiers "AES_128_CBC_HMAC_SHA_256" and "A128CBC-HS256".

B.2.  Encrypt Plaintext to Create Ciphertext

   Encrypt the Plaintext with AES in Cipher Block Chaining (CBC) mode
   using PKCS #5 padding using the ENC_KEY above.  The Plaintext in this
   example is:

   [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
   112, 114, 111, 115, 112, 101, 114, 46]

   The encryption result is as follows, which is the Ciphertext output:

   [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
   75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
   112, 56, 102]

B.3.  64 Bit Big Endian Representation of AAD Length

   The Additional Authenticated Data (AAD) in this example is:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
   83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
   77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
   110, 48]

   This AAD is 51 bytes long, which is 408 bits long.  The octet string
   AL, which is the number of bits in AAD expressed as a big endian 64
   bit unsigned integer is:

   [0, 0, 0, 0, 0, 0, 1, 152]

B.4.  Initialization Vector Value

   The Initialization Vector value used in this example is:

   [3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,



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   101]

B.5.  Create Input to HMAC Computation

   Concatenate the AAD, the Initialization Vector, the Ciphertext, and
   the AL value.  The result of this concatenation is:

   [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
   83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
   77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
   110, 48, 3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111,
   116, 104, 101, 40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24,
   152, 230, 6, 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215,
   104, 143, 112, 56, 102, 0, 0, 0, 0, 0, 0, 1, 152]

B.6.  Compute HMAC Value

   Compute the HMAC SHA-256 of the concatenated value above.  This
   result M is:

   [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
   194, 85, 9, 84, 229, 201, 219, 135, 44, 252, 145, 102, 179, 140, 105,
   86, 229, 116]

B.7.  Truncate HMAC Value to Create Authentication Tag

   Use the first half (128 bits) of the HMAC output M as the
   Authentication Tag output T. This truncated value is:

   [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
   194, 85]


Appendix C.  Acknowledgements

   Solutions for encrypting JSON content were also explored by JSON
   Simple Encryption [JSE] and JavaScript Message Security Format
   [I-D.rescorla-jsms], both of which significantly influenced this
   draft.  This draft attempts to explicitly reuse as many of the
   relevant concepts from XML Encryption 1.1
   [W3C.CR-xmlenc-core1-20120313] and RFC 5652 [RFC5652] as possible,
   while utilizing simple, compact JSON-based data structures.

   Special thanks are due to John Bradley and Nat Sakimura for the
   discussions that helped inform the content of this specification and
   to Eric Rescorla and Joe Hildebrand for allowing the reuse of text
   from [I-D.rescorla-jsms] in this document.




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   Thanks to Axel Nennker, Emmanuel Raviart, Brian Campbell, and Edmund
   Jay for validating the examples in this specification.

   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:

   Richard Barnes, John Bradley, Brian Campbell, Breno de Medeiros, Dick
   Hardt, Jeff Hodges, Edmund Jay, James Manger, Matt Miller, Tony
   Nadalin, Axel Nennker, Emmanuel Raviart, Nat Sakimura, Jim Schaad,
   Hannes Tschofenig, and Sean Turner.

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


Appendix D.  Document History

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

   -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
      recipient 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 #176.

   o  Explicitly named all the logical components of a JWE 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  Header Parameters and processing rules occurring in both JWS and
      JWE are now referenced in JWS by JWE, rather than duplicated,
      addressing issue #57.





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   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 #163, #168, #169,
      #170, #172, and #173.

   -15

   o  Clarified that it is an application decision which recipients'
      encrypted content must successfully validate for the JWE to be
      accepted, addressing issue #35.

   o  Changes to address editorial issues #34, #164, and #169.

   -14

   o  Clarified that the "protected", "unprotected", "header", "iv",
      "tag", and "encrypted_key" parameters are to be omitted in the JWE
      JSON Serialization when their values would be empty.  Stated that
      the "recipients" array must always be present.

   -13

   o  Added an "aad" (Additional Authenticated Data) member for the JWE
      JSON Serialization, enabling Additional Authenticated Data to be
      supplied that is not double base64url encoded, addressing issue
      #29.

   -12

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

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

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

   o  Moved the "epk", "apu", and "apv" Header Parameter definitions to
      be with the algorithm descriptions that use them.




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

   o  Restored use of the term "AEAD".

   o  Changed terminology from "block encryption" to "content
      encryption".

   -11

   o  Added Key Identification section.

   o  Removed the Encrypted Key value from the AAD computation since it
      is already effectively integrity protected by the encryption
      process.  The AAD value now only contains the representation of
      the JWE Encrypted Header.

   o  For the JWE 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 JWE Compact Serialization, in which all Header
      Parameter values are in a single integrity protected JWE Header
      value.)

   o  Shortened the names "authentication_tag" to "tag" and
      "initialization_vector" to "iv" in the JWE JSON Serialization,
      addressing issue #20.

   o  Removed "apv" (agreement PartyVInfo) since it is no longer used.

   o  Removed suggested compact serialization for multiple recipients.

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

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

   -10

   o  Changed the JWE processing rules for multiple recipients so that a
      single AAD value contains the header parameters and encrypted key
      values for all the recipients, enabling AES GCM to be safely used
      for multiple recipients.



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   o  Added an appendix suggesting a possible compact serialization for
      JWEs with multiple recipients.

   -09

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

   o  Registered "application/jwe-js" MIME type and "JWE-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  Corrected "x5c" description.  This addressed issue #12.

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

   o  Added Key Management Mode definitions to terminology section and
      used the defined terms to provide clearer key management
      instructions.  This addressed issue #5.

   o  Added text about preventing the recipient from behaving as an
      oracle during decryption, especially when using RSAES-PKCS1-V1_5.

   o  Changed from using the term "Integrity Value" to "Authentication
      Tag".

   o  Changed member name from "integrity_value" to "authentication_tag"
      in the JWE JSON Serialization.

   o  Removed Initialization Vector from the AAD value since it is
      already integrity protected by all of the authenticated encryption
      algorithms specified in the JWA specification.

   o  Replaced "A128CBC+HS256" and "A256CBC+HS512" with "A128CBC-HS256"
      and "A256CBC-HS512".  The new algorithms perform the same
      cryptographic computations as [I-D.mcgrew-aead-aes-cbc-hmac-sha2],
      but with the Initialization Vector and Authentication Tag values
      remaining separate from the Ciphertext value in the output
      representation.  Also deleted the header parameters "epu"
      (encryption PartyUInfo) and "epv" (encryption PartyVInfo), since
      they are no longer used.

   -08



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   o  Replaced uses of the term "AEAD" with "Authenticated Encryption",
      since the term AEAD in the RFC 5116 sense implied the use of a
      particular data representation, rather than just referring to the
      class of algorithms that perform authenticated encryption with
      associated data.

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

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

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

   o  Added seriesInfo information to Internet Draft references.

   -07

   o  Added a data length prefix to PartyUInfo and PartyVInfo values.

   o  Updated values for example AES CBC calculations.

   o  Made several local editorial changes to clean up loose ends left
      over from to the decision to only support block encryption methods
      providing integrity.  One of these changes was to explicitly state
      that the "enc" (encryption method) algorithm must be an
      Authenticated Encryption algorithm with a specified key length.

   -06

   o  Removed the "int" and "kdf" parameters and defined the new
      composite Authenticated Encryption algorithms "A128CBC+HS256" and
      "A256CBC+HS512" to replace the former uses of AES CBC, which
      required the use of separate integrity and key derivation
      functions.

   o  Included additional values in the Concat KDF calculation -- the
      desired output size and the algorithm value, and optionally
      PartyUInfo and PartyVInfo values.  Added the optional header
      parameters "apu" (agreement PartyUInfo), "apv" (agreement
      PartyVInfo), "epu" (encryption PartyUInfo), and "epv" (encryption
      PartyVInfo).  Updated the KDF examples accordingly.

   o  Promoted Initialization Vector from being a header parameter to
      being a top-level JWE element.  This saves approximately 16 bytes
      in the compact serialization, which is a significant savings for
      some use cases.  Promoting the Initialization Vector out of the



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      header also avoids repeating this shared value in the JSON
      serialization.

   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  Added an AES Key Wrap example.

   o  Reordered the encryption steps so CMK creation is first, when
      required.

   o  Correct statements in examples about which algorithms produce
      reproducible results.

   -05

   o  Support both direct encryption using a shared or agreed upon
      symmetric key, and the use of a shared or agreed upon symmetric
      key to key wrap the CMK.

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

   o  Updated open issues.

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

   -04

   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 Encryption 1.1
      [W3C.CR-xmlenc-core1-20120313] for its security considerations.

   o  Reference draft-jones-jose-jwe-json-serialization instead of
      draft-jones-json-web-encryption-json-serialization.

   o  Described additional open issues.

   o  Applied editorial suggestions.

   -03



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   o  Added the "kdf" (key derivation function) header parameter to
      provide crypto agility for key derivation.  The default KDF
      remains the Concat KDF with the SHA-256 digest function.

   o  Reordered encryption steps so that the Encoded JWE Header is
      always created before it is needed as an input to the
      Authenticated Encryption "additional authenticated data"
      parameter.

   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  Moved description of how to determine whether a header is for a
      JWS or a JWE from the JWT spec to the JWE spec.

   o  Added complete encryption examples for both Authenticated
      Encryption and non-Authenticated Encryption algorithms.

   o  Added complete key derivation examples.

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

   o  Reference ITU.X690.1994 for DER encoding.

   o  Added Registry Contents sections to populate registry values.

   o  Numerous editorial improvements.

   -02

   o  When using Authenticated Encryption algorithms (such as AES GCM),
      use the "additional authenticated data" parameter to provide
      integrity for the header, encrypted key, and ciphertext and use
      the resulting "authentication tag" value as the JWE Authentication
      Tag.

   o  Defined KDF output key sizes.

   o  Generalized text to allow key agreement to be employed as an
      alternative to key wrapping or key encryption.

   o  Changed compression algorithm from gzip to DEFLATE.

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




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

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

   o  Registered application/jwe MIME type and "JWE" 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  Added an integrity check for non-Authenticated Encryption
      algorithms.

   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 JWE Compact
      Serialization.  Referenced the new JWE-JS spec, which defines the
      JWE JSON Serialization.

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

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



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

   -00

   o  Created the initial IETF draft based upon
      draft-jones-json-web-encryption-02 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/


   Eric Rescorla
   RTFM, Inc.

   Email: ekr@rtfm.com


   Joe Hildebrand
   Cisco Systems, Inc.

   Email: jhildebr@cisco.com




















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