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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                             E. Rescorla
Expires: November 29, 2013                                          RTFM
                                                           J. Hildebrand
                                                                   Cisco
                                                            May 28, 2013


                       JSON Web Encryption (JWE)
                 draft-ietf-jose-json-web-encryption-11

Abstract

   JSON Web Encryption (JWE) is a means of representing 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.  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 November 29, 2013.

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
   carefully, as they describe your rights and restrictions with respect



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  JSON Web Encryption (JWE) Overview . . . . . . . . . . . . . .  8
     3.1.  Example JWE  . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  JWE Header . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.1.  Reserved Header Parameter Names  . . . . . . . . . . . . . 11
       4.1.1.  "alg" (Algorithm) Header Parameter . . . . . . . . . . 11
       4.1.2.  "enc" (Encryption Method) Header Parameter . . . . . . 12
       4.1.3.  "epk" (Ephemeral Public Key) Header Parameter  . . . . 12
       4.1.4.  "zip" (Compression Algorithm) Header Parameter . . . . 12
       4.1.5.  "jku" (JWK Set URL) Header Parameter . . . . . . . . . 13
       4.1.6.  "jwk" (JSON Web Key) Header Parameter  . . . . . . . . 13
       4.1.7.  "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 13
       4.1.8.  "x5t" (X.509 Certificate Thumbprint) Header
               Parameter  . . . . . . . . . . . . . . . . . . . . . . 13
       4.1.9.  "x5c" (X.509 Certificate Chain) Header Parameter . . . 14
       4.1.10. "kid" (Key ID) Header Parameter  . . . . . . . . . . . 14
       4.1.11. "typ" (Type) Header Parameter  . . . . . . . . . . . . 14
       4.1.12. "cty" (Content Type) Header Parameter  . . . . . . . . 15
       4.1.13. "apu" (Agreement PartyUInfo) Header Parameter  . . . . 15
       4.1.14. "crit" (Critical) Header Parameter . . . . . . . . . . 15
     4.2.  Public Header Parameter Names  . . . . . . . . . . . . . . 16
     4.3.  Private Header Parameter Names . . . . . . . . . . . . . . 16
   5.  Producing and Consuming JWEs . . . . . . . . . . . . . . . . . 16
     5.1.  Message Encryption . . . . . . . . . . . . . . . . . . . . 16
     5.2.  Message Decryption . . . . . . . . . . . . . . . . . . . . 18
     5.3.  String Comparison Rules  . . . . . . . . . . . . . . . . . 20
   6.  Cryptographic Algorithms . . . . . . . . . . . . . . . . . . . 21
     6.1.  CEK Encryption . . . . . . . . . . . . . . . . . . . . . . 21
   7.  Key Identification . . . . . . . . . . . . . . . . . . . . . . 21
   8.  JWE JSON Serialization . . . . . . . . . . . . . . . . . . . . 22
   9.  Implementation Considerations  . . . . . . . . . . . . . . . . 24
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
     10.1. Registration of JWE Header Parameter Names . . . . . . . . 24
       10.1.1. Registry Contents  . . . . . . . . . . . . . . . . . . 25
     10.2. JSON Web Signature and Encryption Type Values
           Registration . . . . . . . . . . . . . . . . . . . . . . . 26
       10.2.1. Registry Contents  . . . . . . . . . . . . . . . . . . 26
     10.3. Media Type Registration  . . . . . . . . . . . . . . . . . 26



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       10.3.1. Registry Contents  . . . . . . . . . . . . . . . . . . 27
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 28
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 28
     12.2. Informative References . . . . . . . . . . . . . . . . . . 30
   Appendix A.  JWE Examples  . . . . . . . . . . . . . . . . . . . . 30
     A.1.  Example JWE using RSAES OAEP and AES GCM . . . . . . . . . 30
       A.1.1.  JWE Header . . . . . . . . . . . . . . . . . . . . . . 31
       A.1.2.  Encoded JWE Header . . . . . . . . . . . . . . . . . . 31
       A.1.3.  Content Encryption Key (CEK) . . . . . . . . . . . . . 31
       A.1.4.  Key Encryption . . . . . . . . . . . . . . . . . . . . 31
       A.1.5.  Encoded JWE Encrypted Key  . . . . . . . . . . . . . . 34
       A.1.6.  Initialization Vector  . . . . . . . . . . . . . . . . 34
       A.1.7.  Additional Authenticated Data  . . . . . . . . . . . . 34
       A.1.8.  Plaintext Encryption . . . . . . . . . . . . . . . . . 34
       A.1.9.  Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 35
       A.1.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 35
       A.1.11. Complete Representation  . . . . . . . . . . . . . . . 35
       A.1.12. Validation . . . . . . . . . . . . . . . . . . . . . . 36
     A.2.  Example JWE using RSAES-PKCS1-V1_5 and
           AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 36
       A.2.1.  JWE Header . . . . . . . . . . . . . . . . . . . . . . 36
       A.2.2.  Encoded JWE Header . . . . . . . . . . . . . . . . . . 36
       A.2.3.  Content Encryption Key (CEK) . . . . . . . . . . . . . 36
       A.2.4.  Key Encryption . . . . . . . . . . . . . . . . . . . . 37
       A.2.5.  Encoded JWE Encrypted Key  . . . . . . . . . . . . . . 39
       A.2.6.  Initialization Vector  . . . . . . . . . . . . . . . . 39
       A.2.7.  Additional Authenticated Data  . . . . . . . . . . . . 39
       A.2.8.  Plaintext Encryption . . . . . . . . . . . . . . . . . 39
       A.2.9.  Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 40
       A.2.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 40
       A.2.11. Complete Representation  . . . . . . . . . . . . . . . 40
       A.2.12. Validation . . . . . . . . . . . . . . . . . . . . . . 40
     A.3.  Example JWE using AES Key Wrap and AES GCM . . . . . . . . 41
       A.3.1.  JWE Header . . . . . . . . . . . . . . . . . . . . . . 41
       A.3.2.  Encoded JWE Header . . . . . . . . . . . . . . . . . . 41
       A.3.3.  Content Encryption Key (CEK) . . . . . . . . . . . . . 41
       A.3.4.  Key Encryption . . . . . . . . . . . . . . . . . . . . 41
       A.3.5.  Encoded JWE Encrypted Key  . . . . . . . . . . . . . . 42
       A.3.6.  Initialization Vector  . . . . . . . . . . . . . . . . 42
       A.3.7.  Additional Authenticated Data  . . . . . . . . . . . . 42
       A.3.8.  Plaintext Encryption . . . . . . . . . . . . . . . . . 42
       A.3.9.  Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 43
       A.3.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 43
       A.3.11. Complete Representation  . . . . . . . . . . . . . . . 43
       A.3.12. Validation . . . . . . . . . . . . . . . . . . . . . . 43
     A.4.  Example JWE Using JWE JSON Serialization . . . . . . . . . 44
       A.4.1.  JWE Per-Recipient Unprotected Headers  . . . . . . . . 44



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       A.4.2.  JWE Protected Header . . . . . . . . . . . . . . . . . 44
       A.4.3.  JWE Unprotected Header . . . . . . . . . . . . . . . . 45
       A.4.4.  Complete JWE Header Values . . . . . . . . . . . . . . 45
       A.4.5.  Additional Authenticated Data  . . . . . . . . . . . . 45
       A.4.6.  Plaintext Encryption . . . . . . . . . . . . . . . . . 45
       A.4.7.  Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 46
       A.4.8.  Encoded JWE Authentication Tag . . . . . . . . . . . . 46
       A.4.9.  Complete JWE JSON Serialization Representation . . . . 46
   Appendix B.  Example AES_128_CBC_HMAC_SHA_256 Computation  . . . . 47
     B.1.  Extract MAC_KEY and ENC_KEY from Key . . . . . . . . . . . 47
     B.2.  Encrypt Plaintext to Create Ciphertext . . . . . . . . . . 47
     B.3.  64 Bit Big Endian Representation of AAD Length . . . . . . 48
     B.4.  Initialization Vector Value  . . . . . . . . . . . . . . . 48
     B.5.  Create Input to HMAC Computation . . . . . . . . . . . . . 48
     B.6.  Compute HMAC Value . . . . . . . . . . . . . . . . . . . . 48
     B.7.  Truncate HMAC Value to Create Authentication Tag . . . . . 49
   Appendix C.  Acknowledgements  . . . . . . . . . . . . . . . . . . 49
   Appendix D.  Document History  . . . . . . . . . . . . . . . . . . 49
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 56
































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1.  Introduction

   JSON Web Encryption (JWE) is a means of representing encrypted
   content using JavaScript Object Notation (JSON) [RFC4627] based data
   structures.  The JWE cryptographic mechanisms encrypt and provide
   integrity protection for arbitrary sequences of octets.

   Two closely related representations 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.  Related digital signature and MAC capabilities
   are described in the separate JSON Web Signature (JWS) [JWS]
   specification.

1.1.  Notational Conventions

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


2.  Terminology

   JSON Web Encryption (JWE)  A data structure representing an encrypted
      message.  The structure represents five values: the JWE Header,
      the JWE Encrypted Key, the JWE Initialization Vector, the JWE
      Ciphertext, and the JWE Authentication Tag.

   Authenticated Encryption  An Authenticated Encryption algorithm is
      one that provides an integrated content integrity check.
      Authenticated Encryption 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.





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   Ciphertext  An encrypted representation of the Plaintext.

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

   Authentication Tag  An output of an Authenticated Encryption
      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 Authenticated
      Encryption algorithm used to encrypt the Plaintext for the
      recipient to produce the Ciphertext and the Authentication Tag.

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

   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.

   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.





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

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

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

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

   Encoded JWE Header  Base64url encoding of the JWE Protected Header.

   Encoded JWE Encrypted Key  Base64url encoding of the JWE Encrypted
      Key.

   Encoded JWE Initialization Vector  Base64url encoding of the JWE
      Initialization Vector.

   Encoded JWE Ciphertext  Base64url encoding of the JWE Ciphertext.

   Encoded JWE Authentication Tag  Base64url encoding of the JWE
      Authentication Tag.

   JWE Compact Serialization  A representation of the JWE as the
      concatenation of the Encoded JWE Header, the Encoded JWE Encrypted
      Key, the Encoded JWE Initialization Vector, the Encoded JWE
      Ciphertext, and the Encoded JWE Authentication Tag in that order,
      with the five strings being separated by four period ('.')
      characters.  This representation is compact and URL-safe.

   JWE JSON Serialization  A representation of the JWE as a JSON
      structure containing JWE Header, Encoded JWE Encrypted Key,
      Encoded JWE Initialization Vector, Encoded JWE Ciphertext, and
      Encoded JWE Authentication Tag values.  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.

   Collision Resistant Namespace  A namespace that allows names to be
      allocated in a manner such that they are highly unlikely to
      collide with other names.  For instance, collision resistance can
      be achieved through administrative delegation of portions of the
      namespace or through use of collision-resistant name allocation
      functions.  Examples of Collision Resistant Namespaces include:
      Domain Names, Object Identifiers (OIDs) as defined in the ITU-T
      X.660 and X.670 Recommendation series, and Universally Unique



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      IDentifiers (UUIDs) [RFC4122].  When using an administratively
      delegated namespace, the definer of a name needs to take
      reasonable precautions to ensure they are in control of the
      portion of the namespace they use to define the name.

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

   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.

   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.  Five values are represented in a JWE: the JWE
   Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE
   Ciphertext, and the JWE Authentication Tag. In the Compact
   Serialization, the five values are base64url-encoded for
   transmission, and represented as the concatenation of the encoded



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   strings in that order, with the five strings being separated by four
   period ('.') characters.  A JSON Serialization for this information
   is also defined in Section 8.

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

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 and
   AES GCM.

   The following example JWE 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"}

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

     eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

   The remaining steps to finish creating this JWE are:

   o  Generate a random Content Encryption Key (CEK).

   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 to produce the Encoded JWE
      Encrypted Key.

   o  Generate a random JWE Initialization Vector.

   o  Base64url encode the JWE Initialization Vector to produce the
      Encoded JWE Initialization Vector.

   o  Let the Additional Authenticated Data encryption parameter be the
      octets of the ASCII representation of the Encoded JWE Header
      value.



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   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 to create the Encoded JWE
      Ciphertext.

   o  Base64url encode the Authentication Tag to create the Encoded JWE
      Authentication Tag.

   o  Assemble the final representation: The Compact Serialization of
      this result is the concatenation of the Encoded JWE Header, the
      Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector,
      the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag
      in that order, with the five strings being separated by four
      period ('.') characters.

   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.


4.  JWE Header

   The members of the JSON object(s) represented by 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; JWEs with duplicate Header Parameter
   Names MUST be rejected.

   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



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   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 4.1.14, all other header parameters MUST be ignored when not
   understood.

   There are two ways of distinguishing whether a header is a JWS Header
   or a JWE Header.  The first is 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.  A second method is determining whether an "enc"
   (encryption method) member exists.  If the "enc" member exists, it is
   a JWE; otherwise, it is a JWS.  Both methods will yield the same
   result for all legal input values.

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

4.1.  Reserved Header Parameter Names

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

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

4.1.1.  "alg" (Algorithm) Header Parameter

   The "alg" (algorithm) header parameter identifies the cryptographic
   algorithm used to encrypt or determine the value of the Content
   Encryption Key (CEK).  The algorithm specified by the "alg" value
   MUST be supported by the implementation and there MUST be a key for
   use with that algorithm associated with the intended recipient or the
   JWE MUST be rejected. "alg" values SHOULD either be registered in the
   IANA JSON Web Signature and Encryption Algorithms registry [JWA] or
   be a value that contains a Collision Resistant Namespace.  The "alg"
   value is a case sensitive string containing a StringOrURI value.  Use
   of this header parameter is REQUIRED.  This header parameter MUST be
   understood by implementations.



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   A list of defined "alg" values can be found in the IANA JSON Web
   Signature and Encryption Algorithms registry [JWA]; the initial
   contents of this registry are the values defined in Section 4.1 of
   the JSON Web Algorithms (JWA) [JWA] specification.

4.1.2.  "enc" (Encryption Method) Header Parameter

   The "enc" (encryption method) header parameter identifies the block
   encryption algorithm used to encrypt the Plaintext to produce the
   Ciphertext.  This algorithm MUST be an Authenticated Encryption
   algorithm with a specified key length.  The algorithm specified by
   the "enc" value MUST be supported by the implementation or the JWE
   MUST be rejected. "enc" values SHOULD either be registered in the
   IANA JSON Web Signature and Encryption Algorithms registry [JWA] or
   be a value that contains a Collision Resistant Namespace.  The "enc"
   value is a case sensitive string containing a StringOrURI value.  Use
   of this header parameter is REQUIRED.  This header parameter MUST be
   understood by implementations.

   A list of defined "enc" values can be found in the IANA JSON Web
   Signature and Encryption Algorithms registry [JWA]; the initial
   contents of this registry are the values defined in Section 4.2 of
   the JSON Web Algorithms (JWA) [JWA] specification.

4.1.3.  "epk" (Ephemeral Public Key) Header Parameter

   The "epk" (ephemeral public key) value created by the originator for
   the use in key agreement algorithms.  This key is represented as a
   JSON Web Key [JWK] value.  When the "alg" value used identifies an
   algorithm for which "epk" is a parameter, this parameter MUST be
   present if REQUIRED by the algorithm and this header parameter MUST
   be understood by implementations; otherwise, this parameter MUST be
   omitted.

4.1.4.  "zip" (Compression Algorithm) Header Parameter

   The "zip" (compression algorithm) applied to the Plaintext before
   encryption, if any.  If present, the value of the "zip" header
   parameter MUST be the case sensitive string "DEF".  Compression is
   performed with the DEFLATE [RFC1951] algorithm.  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 with the JWE Protected
   Header, when used.  Use of this header parameter is OPTIONAL.  This
   header parameter MUST be understood by implementations.






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

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

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

   The "jwk" (JSON Web Key) header parameter is the public key to which
   the JWE was encrypted; this can be used to determine the private key
   needed to decrypt the JWE.  This key is represented as a JSON Web Key
   [JWK].  Use of this header parameter is OPTIONAL.

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

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

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

   The "x5t" (X.509 Certificate Thumbprint) header parameter is a
   base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER
   encoding of the X.509 certificate [RFC5280] containing the key to
   which the JWE was encrypted; this can be used to determine the
   private key needed to decrypt the JWE.  Use of this header parameter
   is OPTIONAL.

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



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

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

   The "x5c" (X.509 Certificate Chain) header parameter contains the
   X.509 public key certificate or certificate chain [RFC5280]
   containing the key to which the JWE was encrypted; this can be used
   to determine the private key needed to decrypt the JWE.  The
   certificate or certificate chain is represented as a JSON array of
   certificate value strings.  Each string in the array is a base64
   encoded ([RFC4648] Section 4 -- not base64url encoded) DER
   [ITU.X690.1994] PKIX certificate value.  The certificate containing
   the public key to which the JWE was encrypted MUST be the first
   certificate.  This MAY be followed by additional certificates, with
   each subsequent certificate being the one used to certify the
   previous one.  Use of this header parameter is OPTIONAL.

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

4.1.10.  "kid" (Key ID) Header Parameter

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

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

4.1.11.  "typ" (Type) Header Parameter

   The "typ" (type) header parameter is used to declare the type of this
   object.  The type value "JWE" is used to indicate that this object is
   a JWE using the JWE Compact Serialization.  The type value "JWE+JSON"
   is used to indicate that this object is a JWE using the JWE JSON
   Serialization.  Other type values MAY be used, and if not understood,
   SHOULD be ignored.  The "typ" value is a case sensitive string.  Use
   of this header parameter is OPTIONAL.




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

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

4.1.12.  "cty" (Content Type) Header Parameter

   The "cty" (content type) header parameter is used to declare the type
   of the encrypted content (the Plaintext).  For example, the JSON Web
   Token (JWT) [JWT] specification uses the "cty" value "JWT" to
   indicate that the Plaintext is a JSON Web Token (JWT).  Content type
   values that are not understood SHOULD be ignored.  The "cty" value is
   a case sensitive string.  Use of this header parameter is OPTIONAL.

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

4.1.13.  "apu" (Agreement PartyUInfo) Header Parameter

   The "apu" (agreement PartyUInfo) value for key agreement algorithms
   using it (such as "ECDH-ES"), represented as a base64url encoded
   string.  Use of this header parameter is OPTIONAL.  When the "alg"
   value used identifies an algorithm for which "apu" is a parameter,
   this header parameter MUST be understood by implementations;
   otherwise, this parameter MUST be omitted.

4.1.14.  "crit" (Critical) Header Parameter

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





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

     {"alg":"RSA-OAEP",
      "enc":"A256GCM",
      "crit":["exp"],
      "exp":1363284000
     }

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 [JWS] or be a Public Name: a
   value that contains a Collision Resistant Namespace.  In each case,
   the definer of the name or value needs to take reasonable precautions
   to make sure they are in control of the part of the namespace they
   use to define the Header Parameter Name.

   New header parameters should be introduced sparingly, as they can
   result in non-interoperable 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 Reserved Names
   Section 4.1 or Public Names Section 4.2.  Unlike Public Names,
   Private Names are subject to collision and should be used with
   caution.


5.  Producing and Consuming 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.)

   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



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        generating random values.  The CEK MUST have a length equal to
        that required for the block 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 (see
        Section 6.1) 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.   Base64url encode the JWE Encrypted Key to create the Encoded 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 block encryption algorithm (if required for the
        algorithm); otherwise, let the JWE Initialization Vector be the
        empty octet sequence.

   10.  Base64url encode the JWE Initialization Vector to create the
        Encoded 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.  Base64url encode the octets of the UTF-8 representation of the
        JWE Protected Header to create the Encoded JWE Header.  If the
        JWE Protected Header is not present (which can only happen when
        using the JWE JSON Serialization), let the Encoded JWE Header be
        the empty string.



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   15.  Let the Additional Authenticated Data encryption parameter be
        the octets of the ASCII representation of the Encoded JWE Header
        value.

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

   17.  Base64url encode the JWE Ciphertext to create the Encoded JWE
        Ciphertext.

   18.  Base64url encode the JWE Authentication Tag to create the
        Encoded JWE Authentication Tag.

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

   20.  Create the desired serialized output.  The JWE Compact
        Serialization of this result is the concatenation of the Encoded
        JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE
        Initialization Vector, the Encoded JWE Ciphertext, and the
        Encoded JWE Authentication Tag in that order, with the five
        strings being separated by four period ('.') characters.  The
        JWE JSON Serialization is described in Section 8.

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 JWE MUST be rejected.

   1.   Parse the serialized input to determine the values of the JWE
        Header, the Encoded JWE Encrypted Key, the Encoded JWE
        Initialization Vector, the Encoded JWE Ciphertext, and the
        Encoded JWE Authentication Tag. When using the JWE Compact
        Serialization, the Encoded JWE Header, the Encoded JWE Encrypted
        Key, the Encoded JWE Initialization Vector, the Encoded JWE
        Ciphertext, and the Encoded JWE Authentication Tag are
        represented as text strings in that order, separated by four
        period ('.') characters.  The JWE JSON Serialization is
        described in Section 8.

   2.   The Encoded JWE Header, the Encoded JWE Encrypted Key, the
        Encoded JWE Initialization Vector, the Encoded JWE Ciphertext,



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        and the Encoded JWE Authentication Tag MUST be successfully
        base64url decoded following the restriction that no padding
        characters have been used.

   3.   The resulting 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 members of the "unprotected"
        value, and the members of the corresponding "header" value, 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.

   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 block 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 against attacks described in RFC 3218 [RFC3218], the
        recipient MUST NOT distinguish between format, padding, and



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        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
        the octets of the ASCII representation of the Encoded JWE Header
        value.

   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 block encryption algorithm,
        returning the decrypted plaintext and verifying the JWE
        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

   Processing a JWE inevitably requires comparing known strings to
   values in JSON objects.  For example, in checking what the encryption
   method is, the Unicode string encoding "enc" will be checked against
   the member names in the JWE Header to see if there is a matching
   Header Parameter Name.

   Comparisons between JSON strings and other Unicode strings MUST be
   performed by comparing Unicode code points without normalization as
   specified in the String Comparison Rules in Section 5.3 of [JWS].






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6.  Cryptographic Algorithms

   JWE uses cryptographic algorithms to encrypt the Plaintext and the
   Content Encryption Key (CEK) and to provide integrity protection for
   the JWE Protected Header and JWE Ciphertext.  The JSON Web Algorithms
   (JWA) [JWA] specification specifies a set of cryptographic algorithms
   and identifiers to be used with this specification and defines
   registries for additional such algorithms.  Specifically, Section 4.1
   specifies a set of "alg" (algorithm) header parameter values and
   Section 4.2 specifies a set of "enc" (encryption method) header
   parameter values intended for use this specification.  It also
   describes the semantics and operations that are specific to these
   algorithms.

6.1.  CEK Encryption

   JWE supports three forms of Content Encryption Key (CEK) encryption:

   o  Asymmetric encryption under the recipient's public key.

   o  Symmetric encryption under a key shared between the sender and
      receiver.

   o  Symmetric encryption under a key agreed upon between the sender
      and receiver.

   See the algorithms registered for "enc" usage in the IANA JSON Web
   Signature and Encryption Algorithms registry [JWA] and Section 4.1 of
   the JSON Web Algorithms (JWA) [JWA] specification for lists of
   encryption algorithms that can be used for CEK encryption.


7.  Key Identification

   It is necessary for the recipient of a JWE to be able to determine
   the key that was employed for the encryption operation.  The key
   employed can be identified using the Header Parameter methods
   described in Section 4.1 or can be identified using methods that are
   outside the scope of this specification.  Specifically, the Header
   Parameters "jku", "jwk", "x5u", "x5t", "x5c", and "kid" can be used
   to identify the key used.  The sender SHOULD include sufficient
   information in the Header Parameters to identify the key used, unless
   the application uses another means or convention to determine the key
   used.  Recipients MUST reject the input when the key used cannot be
   determined.






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8.  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
   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 Encoded JWE Header value, if non-empty, is stored in the
      "protected" member.

   o  The Encoded JWE Initialization Vector value is stored in the "iv"
      member.

   o  The Encoded JWE Ciphertext value is stored in the "ciphertext"
      member.

   o  The Encoded JWE Authentication Tag value 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 Encoded JWE Encrypted Key value 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.  Per-recipient header parameter values 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.  These header parameters
      are stored in either of two top-level member(s) of the JSON
      object: the "protected" member and the "unprotected" member.  The
      values of these members are JSON Text Objects containing Header



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      Parameters.

   o  Not all header parameters are integrity protected.  The shared
      header parameters in the "protected" member are integrity
      protected, and are base64url encoded.  The per-recipient header
      parameters in the "header" array element members and the shared
      header parameters in the "unprotected" member 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 per-recipient values in the "header" member of the
      recipient's array element, (2) the shared integrity-protected
      values in the "protected" member, and (3) the shared non-
      integrity-protected values in the "unprotected" member.  The union
      of these sets of header parameters comprises the JWE Header.  The
      header parameter names in the three locations MUST be disjoint.

   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>"}],
      "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
   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 Encoded JWE Encrypted Key, Encoded JWE
   Initialization Vector, Encoded JWE Ciphertext, and Encoded JWE
   Authentication Tag values are exactly as defined in the rest of this
   specification.  They are interpreted and validated in the same



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   manner, with each corresponding Encoded JWE Encrypted Key, Encoded
   JWE Initialization Vector, Encoded JWE Ciphertext, Encoded 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 "protected", "unprotected", and
   corresponding "header" members, 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
   Encoded 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 Encoded JWE 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.


9.  Implementation Considerations

   The JWE Compact Serialization is mandatory to implement.
   Implementation of the JWE JSON Serialization is OPTIONAL.


10.  IANA Considerations

10.1.  Registration of JWE Header Parameter Names

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







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10.1.1.  Registry Contents

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

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

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

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

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

   o  Header Parameter Name: "x5u"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.7 of [[ this document ]]

   o  Header Parameter Name: "x5t"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.8 of [[ this document ]]

   o  Header Parameter Name: "x5c"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.9 of [[ this document ]]





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

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

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

   o  Header Parameter Name: "apu"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.13 of [[ this document ]]

   o  Header Parameter Name: "crit"
   o  Header Parameter Usage Location(s): JWS
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.14 of [[ this document ]]

10.2.  JSON Web Signature and Encryption Type Values Registration

10.2.1.  Registry Contents

   This specification registers the "JWE" and "JWE+JSON" type values in
   the IANA JSON Web Signature and Encryption Type Values registry
   [JWS]:

   o  "typ" Header Parameter Value: "JWE"
   o  Abbreviation for MIME Type: application/jwe
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.11 of [[ this document ]]

   o  "typ" Header Parameter Value: "JWE+JSON"
   o  Abbreviation for MIME Type: application/jwe+json
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1.11 of [[ this document ]]

10.3.  Media Type Registration







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10.3.1.  Registry Contents

   This specification registers the "application/jwe" and
   "application/jwe+json" Media Types [RFC2046] in the MIME Media Type
   registry [RFC4288] to indicate, respectively, that the content is a
   JWE using the JWE Compact Serialization or a JWE using the JWE JSON
   Serialization.

   o  Type Name: application
   o  Subtype Name: jwe
   o  Required Parameters: n/a
   o  Optional Parameters: n/a
   o  Encoding considerations: JWE values are encoded as a series of
      base64url encoded values (some of which may be the empty string)
      separated by period ('.') characters
   o  Security Considerations: See the Security Considerations section
      of [[ this document ]]
   o  Interoperability Considerations: n/a
   o  Published Specification: [[ this document ]]
   o  Applications that use this media type: OpenID Connect and other
      applications using encrypted JWTs
   o  Additional Information: Magic number(s): n/a, File extension(s):
      n/a, Macintosh file type code(s): n/a
   o  Person & email address to contact for further information: Michael
      B. Jones, mbj@microsoft.com
   o  Intended Usage: COMMON
   o  Restrictions on Usage: none
   o  Author: Michael B. Jones, mbj@microsoft.com
   o  Change Controller: IETF

   o  Type Name: application
   o  Subtype Name: jwe+json
   o  Required Parameters: n/a
   o  Optional Parameters: n/a
   o  Encoding considerations: application/jwe+json values are
      represented as a JSON Object; UTF-8 encoding SHOULD be employed
      for the JSON object.
   o  Security Considerations: See the Security Considerations section
      of [[ this document ]]
   o  Interoperability Considerations: n/a
   o  Published Specification: [[ this document ]]
   o  Applications that use this media type: TBD
   o  Additional Information: Magic number(s): n/a, File extension(s):
      n/a, Macintosh file type code(s): n/a
   o  Person & email address to contact for further information: Michael
      B. Jones, mbj@microsoft.com





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   o  Intended Usage: COMMON
   o  Restrictions on Usage: none
   o  Author: Michael B. Jones, mbj@microsoft.com
   o  Change Controller: IETF


11.  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 JWE is rejected.


12.  References

12.1.  Normative References

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

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

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



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              draft-ietf-jose-json-web-key (work in progress), May 2013.

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

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

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

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

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

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

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

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

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

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

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

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

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

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



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   [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>.

12.2.  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.

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

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

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

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              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 and
   AES GCM.  The representation of this plaintext is:




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   [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 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"}

A.1.2.  Encoded JWE Header

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

     eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

A.1.3.  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]

A.1.4.  Key Encryption

   Encrypt the CEK with the recipient's public key using the RSAES OAEP
   algorithm to produce the JWE Encrypted Key. In this example, the RSA
   key parameters are:











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   +-----------+-------------------------------------------------------+
   | Parameter | Value                                                 |
   | Name      |                                                       |
   +-----------+-------------------------------------------------------+
   | Modulus   | [161, 168, 84, 34, 133, 176, 208, 173, 46, 176, 163,  |
   |           | 110, 57, 30, 135, 227, 9, 31, 226, 128, 84, 92, 116,  |
   |           | 241, 70, 248, 27, 227, 193, 62, 5, 91, 241, 145, 224, |
   |           | 205, 141, 176, 184, 133, 239, 43, 81, 103, 9, 161,    |
   |           | 153, 157, 179, 104, 123, 51, 189, 34, 152, 69, 97,    |
   |           | 69, 78, 93, 140, 131, 87, 182, 169, 101, 92, 142, 3,  |
   |           | 22, 167, 8, 212, 56, 35, 79, 210, 222, 192, 208, 252, |
   |           | 49, 109, 138, 173, 253, 210, 166, 201, 63, 102, 74,   |
   |           | 5, 158, 41, 90, 144, 108, 160, 79, 10, 89, 222, 231,  |
   |           | 172, 31, 227, 197, 0, 19, 72, 81, 138, 78, 136, 221,  |
   |           | 121, 118, 196, 17, 146, 10, 244, 188, 72, 113, 55,    |
   |           | 221, 162, 217, 171, 27, 57, 233, 210, 101, 236, 154,  |
   |           | 199, 56, 138, 239, 101, 48, 198, 186, 202, 160, 76,   |
   |           | 111, 234, 71, 57, 183, 5, 211, 171, 136, 126, 64, 40, |
   |           | 75, 58, 89, 244, 254, 107, 84, 103, 7, 236, 69, 163,  |
   |           | 18, 180, 251, 58, 153, 46, 151, 174, 12, 103, 197,    |
   |           | 181, 161, 162, 55, 250, 235, 123, 110, 17, 11, 158,   |
   |           | 24, 47, 133, 8, 199, 235, 107, 126, 130, 246, 73,     |
   |           | 195, 20, 108, 202, 176, 214, 187, 45, 146, 182, 118,  |
   |           | 54, 32, 200, 61, 201, 71, 243, 1, 255, 131, 84, 37,   |
   |           | 111, 211, 168, 228, 45, 192, 118, 27, 197, 235, 232,  |
   |           | 36, 10, 230, 248, 190, 82, 182, 140, 35, 204, 108,    |
   |           | 190, 253, 186, 186, 27]                               |
   | Exponent  | [1, 0, 1]                                             |























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   | Private   | [144, 183, 109, 34, 62, 134, 108, 57, 44, 252, 10,    |
   | Exponent  | 66, 73, 54, 16, 181, 233, 92, 54, 219, 101, 42, 35,   |
   |           | 178, 63, 51, 43, 92, 119, 136, 251, 41, 53, 23, 191,  |
   |           | 164, 164, 60, 88, 227, 229, 152, 228, 213, 149, 228,  |
   |           | 169, 237, 104, 71, 151, 75, 88, 252, 216, 77, 251,    |
   |           | 231, 28, 97, 88, 193, 215, 202, 248, 216, 121, 195,   |
   |           | 211, 245, 250, 112, 71, 243, 61, 129, 95, 39, 244,    |
   |           | 122, 225, 217, 169, 211, 165, 48, 253, 220, 59, 122,  |
   |           | 219, 42, 86, 223, 32, 236, 39, 48, 103, 78, 122, 216, |
   |           | 187, 88, 176, 89, 24, 1, 42, 177, 24, 99, 142, 170,   |
   |           | 1, 146, 43, 3, 108, 64, 194, 121, 182, 95, 187, 134,  |
   |           | 71, 88, 96, 134, 74, 131, 167, 69, 106, 143, 121, 27, |
   |           | 72, 44, 245, 95, 39, 194, 179, 175, 203, 122, 16,     |
   |           | 112, 183, 17, 200, 202, 31, 17, 138, 156, 184, 210,   |
   |           | 157, 184, 154, 131, 128, 110, 12, 85, 195, 122, 241,  |
   |           | 79, 251, 229, 183, 117, 21, 123, 133, 142, 220, 153,  |
   |           | 9, 59, 57, 105, 81, 255, 138, 77, 82, 54, 62, 216,    |
   |           | 38, 249, 208, 17, 197, 49, 45, 19, 232, 157, 251,     |
   |           | 131, 137, 175, 72, 126, 43, 229, 69, 179, 117, 82,    |
   |           | 157, 213, 83, 35, 57, 210, 197, 252, 171, 143, 194,   |
   |           | 11, 47, 163, 6, 253, 75, 252, 96, 11, 187, 84, 130,   |
   |           | 210, 7, 121, 78, 91, 79, 57, 251, 138, 132, 220, 60,  |
   |           | 224, 173, 56, 224, 201]                               |
   +-----------+-------------------------------------------------------+

   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]






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A.1.5.  Encoded JWE Encrypted Key

   Base64url encode the JWE Encrypted Key to produce the Encoded JWE
   Encrypted Key. This result (with line breaks for display purposes
   only) is:

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

A.1.6.  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]

   Base64url encoding this value yields the Encoded JWE Initialization
   Vector value:

     48V1_ALb6US04U3b

A.1.7.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be the
   octets of the ASCII representation of the Encoded JWE Header value.
   This AAD 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.1.8.  Plaintext 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]




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   The resulting Authentication Tag value is:

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

A.1.9.  Encoded JWE Ciphertext

   Base64url encode the Ciphertext to create the Encoded JWE Ciphertext.
   This result (with line breaks for display purposes only) is:

     5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
     SdiwkIr3ajwQzaBtQD_A

A.1.10.  Encoded JWE Authentication Tag

   Base64url encode the Authentication Tag to create the Encoded JWE
   Authentication Tag. This result is:

     XFBoMYUZodetZdvTiFvSkQ

A.1.11.  Complete Representation

   Assemble the final representation: The Compact Serialization of this
   result is the concatenation of the Encoded JWE Header, the Encoded
   JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded
   JWE Ciphertext, and the Encoded JWE Authentication Tag in that order,
   with the five strings being separated by four period ('.')
   characters.

   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








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A.1.12.  Validation

   This example illustrates the process of creating a JWE with RSA OAEP
   and AES GCM.  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 and AES_128_CBC_HMAC_SHA_256.  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.2.1.  JWE Header

   The following example JWE Header (with line breaks for display
   purposes only) 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"}

A.2.2.  Encoded JWE Header

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

     eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.2.3.  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]



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A.2.4.  Key Encryption

   Encrypt the CEK with the recipient's public key using the RSAES-
   PKCS1-V1_5 algorithm to produce the JWE Encrypted Key. In this
   example, the RSA key parameters are:

   +-----------+-------------------------------------------------------+
   | Parameter | Value                                                 |
   | Name      |                                                       |
   +-----------+-------------------------------------------------------+
   | Modulus   | [177, 119, 33, 13, 164, 30, 108, 121, 207, 136, 107,  |
   |           | 242, 12, 224, 19, 226, 198, 134, 17, 71, 173, 75, 42, |
   |           | 61, 48, 162, 206, 161, 97, 108, 185, 234, 226, 219,   |
   |           | 118, 206, 118, 5, 169, 224, 60, 181, 90, 85, 51, 123, |
   |           | 6, 224, 4, 122, 29, 230, 151, 12, 244, 127, 121, 25,  |
   |           | 4, 85, 220, 144, 215, 110, 130, 17, 68, 228, 129,     |
   |           | 138, 7, 130, 231, 40, 212, 214, 17, 179, 28, 124,     |
   |           | 151, 178, 207, 20, 14, 154, 222, 113, 176, 24, 198,   |
   |           | 73, 211, 113, 9, 33, 178, 80, 13, 25, 21, 25, 153,    |
   |           | 212, 206, 67, 154, 147, 70, 194, 192, 183, 160, 83,   |
   |           | 98, 236, 175, 85, 23, 97, 75, 199, 177, 73, 145, 50,  |
   |           | 253, 206, 32, 179, 254, 236, 190, 82, 73, 67, 129,    |
   |           | 253, 252, 220, 108, 136, 138, 11, 192, 1, 36, 239,    |
   |           | 228, 55, 81, 113, 17, 25, 140, 63, 239, 146, 3, 172,  |
   |           | 96, 60, 227, 233, 64, 255, 224, 173, 225, 228, 229,   |
   |           | 92, 112, 72, 99, 97, 26, 87, 187, 123, 46, 50, 90,    |
   |           | 202, 117, 73, 10, 153, 47, 224, 178, 163, 77, 48, 46, |
   |           | 154, 33, 148, 34, 228, 33, 172, 216, 89, 46, 225,     |
   |           | 127, 68, 146, 234, 30, 147, 54, 146, 5, 133, 45, 78,  |
   |           | 254, 85, 55, 75, 213, 86, 194, 218, 215, 163, 189,    |
   |           | 194, 54, 6, 83, 36, 18, 153, 53, 7, 48, 89, 35, 66,   |
   |           | 144, 7, 65, 154, 13, 97, 75, 55, 230, 132, 3, 13,     |
   |           | 239, 71]                                              |
   | Exponent  | [1, 0, 1]                                             |

















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   | Private   | [84, 80, 150, 58, 165, 235, 242, 123, 217, 55, 38,    |
   | Exponent  | 154, 36, 181, 221, 156, 211, 215, 100, 164, 90, 88,   |
   |           | 40, 228, 83, 148, 54, 122, 4, 16, 165, 48, 76, 194,   |
   |           | 26, 107, 51, 53, 179, 165, 31, 18, 198, 173, 78, 61,  |
   |           | 56, 97, 252, 158, 140, 80, 63, 25, 223, 156, 36, 203, |
   |           | 214, 252, 120, 67, 180, 167, 3, 82, 243, 25, 97, 214, |
   |           | 83, 133, 69, 16, 104, 54, 160, 200, 41, 83, 164, 187, |
   |           | 70, 153, 111, 234, 242, 158, 175, 28, 198, 48, 211,   |
   |           | 45, 148, 58, 23, 62, 227, 74, 52, 117, 42, 90, 41,    |
   |           | 249, 130, 154, 80, 119, 61, 26, 193, 40, 125, 10,     |
   |           | 152, 174, 227, 225, 205, 32, 62, 66, 6, 163, 100, 99, |
   |           | 219, 19, 253, 25, 105, 80, 201, 29, 252, 157, 237,    |
   |           | 69, 1, 80, 171, 167, 20, 196, 156, 109, 249, 88, 0,   |
   |           | 3, 152, 38, 165, 72, 87, 6, 152, 71, 156, 214, 16,    |
   |           | 71, 30, 82, 51, 103, 76, 218, 63, 9, 84, 163, 249,    |
   |           | 91, 215, 44, 238, 85, 101, 240, 148, 1, 82, 224, 91,  |
   |           | 135, 105, 127, 84, 171, 181, 152, 210, 183, 126, 24,  |
   |           | 46, 196, 90, 173, 38, 245, 219, 186, 222, 27, 240,    |
   |           | 212, 194, 15, 66, 135, 226, 178, 190, 52, 245, 74,    |
   |           | 65, 224, 81, 100, 85, 25, 204, 165, 203, 187, 175,    |
   |           | 84, 100, 82, 15, 11, 23, 202, 151, 107, 54, 41, 207,  |
   |           | 3, 136, 229, 134, 131, 93, 139, 50, 182, 204, 93,     |
   |           | 130, 89]                                              |
   +-----------+-------------------------------------------------------+

   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]






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A.2.5.  Encoded JWE Encrypted Key

   Base64url encode the JWE Encrypted Key to produce the Encoded JWE
   Encrypted Key. This result (with line breaks for display purposes
   only) is:

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

A.2.6.  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]

   Base64url encoding this value yields the Encoded JWE Initialization
   Vector value:

     AxY8DCtDaGlsbGljb3RoZQ

A.2.7.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be the
   octets of the ASCII representation of the Encoded JWE Header value.
   This AAD 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.2.8.  Plaintext 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]



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   The resulting Authentication Tag value is:

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

A.2.9.  Encoded JWE Ciphertext

   Base64url encode the Ciphertext to create the Encoded JWE Ciphertext.
   This result is:

     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

A.2.10.  Encoded JWE Authentication Tag

   Base64url encode the Authentication Tag to create the Encoded JWE
   Authentication Tag. This result is:

     9hH0vgRfYgPnAHOd8stkvw

A.2.11.  Complete Representation

   Assemble the final representation: The Compact Serialization of this
   result is the concatenation of the Encoded JWE Header, the Encoded
   JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded
   JWE Ciphertext, and the Encoded JWE Authentication Tag in that order,
   with the five strings being separated by four period ('.')
   characters.

   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.2.12.  Validation

   This example illustrates the process of creating a JWE with RSAES-
   PKCS1-V1_5 and AES_CBC_HMAC_SHA2.  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,



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   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 GCM

   This example encrypts the plaintext "Live long and prosper." to the
   recipient using AES Key Wrap and AES GCM.  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 Header declares that:

   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"}

A.3.2.  Encoded JWE Header

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

     eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.3.3.  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.3.4.  Key Encryption

   Encrypt the CEK with the shared symmetric key using the AES Key Wrap
   algorithm to produce the JWE Encrypted Key. In this example, the



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   shared symmetric key value is:

   [25, 172, 32, 130, 225, 114, 26, 181, 138, 106, 254, 192, 95, 133,
   74, 82]

   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]

A.3.5.  Encoded JWE Encrypted Key

   Base64url encode the JWE Encrypted Key to produce the Encoded JWE
   Encrypted Key. This result is:

     6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ

A.3.6.  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]

   Base64url encoding this value yields the Encoded JWE Initialization
   Vector value:

     AxY8DCtDaGlsbGljb3RoZQ

A.3.7.  Additional Authenticated Data

   Let the Additional Authenticated Data encryption parameter be the
   octets of the ASCII representation of the Encoded JWE Header value.
   This AAD 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.3.8.  Plaintext 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



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   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]

A.3.9.  Encoded JWE Ciphertext

   Base64url encode the Ciphertext to create the Encoded JWE Ciphertext.
   This result is:

     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

A.3.10.  Encoded JWE Authentication Tag

   Base64url encode the Authentication Tag to create the Encoded JWE
   Authentication Tag. This result is:

     U0m_YmjN04DJvceFICbCVQ

A.3.11.  Complete Representation

   Assemble the final representation: The Compact Serialization of this
   result is the concatenation of the Encoded JWE Header, the Encoded
   JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded
   JWE Ciphertext, and the Encoded JWE Authentication Tag in that order,
   with the five strings being separated by four period ('.')
   characters.

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

     eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
     6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.
     AxY8DCtDaGlsbGljb3RoZQ.
     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
     U0m_YmjN04DJvceFICbCVQ

A.3.12.  Validation

   This example illustrates the process of creating a JWE with symmetric
   key wrap and AES_CBC_HMAC_SHA2.  These results can be used to
   validate JWE decryption implementations for these algorithms.  Also,



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   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).

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 RSAES OAEP 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"}

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



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     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:

     {"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 the
   octets of the ASCII representation of the Encoded JWE Protected
   Header value.  This AAD 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.  Plaintext 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]




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   The resulting Authentication Tag value is:

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

A.4.7.  Encoded JWE Ciphertext

   Base64url encode the Ciphertext to create the Encoded JWE Ciphertext.
   This result is:

     KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

A.4.8.  Encoded JWE Authentication Tag

   Base64url encode the Authentication Tag to create the Encoded JWE
   Authentication Tag. This result is:

     Mz-VPPyU4RlcuYv1IwIvzw

A.4.9.  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):

     {"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"



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     }


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:

   [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:



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   [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,
   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]




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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.

   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 ]]

   -11




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   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.

   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.



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   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

   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.





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   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
      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.





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   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

   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"



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      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.

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

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





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   o  Registered application/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.

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

   -00




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   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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