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rfc:rfc7516

Internet Engineering Task Force (IETF) M. Jones Request for Comments: 7516 Microsoft Category: Standards Track J. Hildebrand ISSN: 2070-1721 Cisco

                                                              May 2015
                     JSON Web Encryption (JWE)

Abstract

 JSON Web Encryption (JWE) represents encrypted content using
 JSON-based data structures.  Cryptographic algorithms and identifiers
 for use with this specification are described in the separate JSON
 Web Algorithms (JWA) specification and IANA registries defined by
 that specification.  Related digital signature and Message
 Authentication Code (MAC) capabilities are described in the separate
 JSON Web Signature (JWS) specification.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7516.

Copyright Notice

 Copyright (c) 2015 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
 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.

Jones & Hildebrand Standards Track [Page 1] RFC 7516 JSON Web Encryption (JWE) May 2015

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
 3.  JSON Web Encryption (JWE) Overview  . . . . . . . . . . . . .   8
   3.1.  JWE Compact Serialization Overview  . . . . . . . . . . .   8
   3.2.  JWE JSON Serialization Overview . . . . . . . . . . . . .   9
   3.3.  Example JWE . . . . . . . . . . . . . . . . . . . . . . .  10
 4.  JOSE Header . . . . . . . . . . . . . . . . . . . . . . . . .  11
   4.1.  Registered Header Parameter Names . . . . . . . . . . . .  11
     4.1.1.  "alg" (Algorithm) Header Parameter  . . . . . . . . .  12
     4.1.2.  "enc" (Encryption Algorithm) Header Parameter . . . .  12
     4.1.3.  "zip" (Compression Algorithm) Header Parameter  . . .  12
     4.1.4.  "jku" (JWK Set URL) Header Parameter  . . . . . . . .  13
     4.1.5.  "jwk" (JSON Web Key) Header Parameter . . . . . . . .  13
     4.1.6.  "kid" (Key ID) Header Parameter . . . . . . . . . . .  13
     4.1.7.  "x5u" (X.509 URL) Header Parameter  . . . . . . . . .  13
     4.1.8.  "x5c" (X.509 Certificate Chain) Header Parameter  . .  13
     4.1.9.  "x5t" (X.509 Certificate SHA-1 Thumbprint) Header
             Parameter . . . . . . . . . . . . . . . . . . . . . .  14
     4.1.10. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint)
             Header Parameter  . . . . . . . . . . . . . . . . . .  14
     4.1.11. "typ" (Type) Header Parameter . . . . . . . . . . . .  14
     4.1.12. "cty" (Content Type) Header Parameter . . . . . . . .  14
     4.1.13. "crit" (Critical) Header Parameter  . . . . . . . . .  14
   4.2.  Public Header Parameter Names . . . . . . . . . . . . . .  14
   4.3.  Private Header Parameter Names  . . . . . . . . . . . . .  15
 5.  Producing and Consuming JWEs  . . . . . . . . . . . . . . . .  15
   5.1.  Message Encryption  . . . . . . . . . . . . . . . . . . .  15
   5.2.  Message Decryption  . . . . . . . . . . . . . . . . . . .  17
   5.3.  String Comparison Rules . . . . . . . . . . . . . . . . .  20
 6.  Key Identification  . . . . . . . . . . . . . . . . . . . . .  20
 7.  Serializations  . . . . . . . . . . . . . . . . . . . . . . .  20
   7.1.  JWE Compact Serialization . . . . . . . . . . . . . . . .  20
   7.2.  JWE JSON Serialization  . . . . . . . . . . . . . . . . .  20
     7.2.1.  General JWE JSON Serialization Syntax . . . . . . . .  21
     7.2.2.  Flattened JWE JSON Serialization Syntax . . . . . . .  23
 8.  TLS Requirements  . . . . . . . . . . . . . . . . . . . . . .  24
 9.  Distinguishing between JWS and JWE Objects  . . . . . . . . .  24
 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
   10.1.  JSON Web Signature and Encryption Header Parameters
          Registration . . . . . . . . . . . . . . . . . . . . . .  25
     10.1.1.  Registry Contents  . . . . . . . . . . . . . . . . .  25
 11. Security Considerations . . . . . . . . . . . . . . . . . . .  27
   11.1.  Key Entropy and Random Values  . . . . . . . . . . . . .  27
   11.2.  Key Protection . . . . . . . . . . . . . . . . . . . . .  27
   11.3.  Using Matching Algorithm Strengths . . . . . . . . . . .  28

Jones & Hildebrand Standards Track [Page 2] RFC 7516 JSON Web Encryption (JWE) May 2015

   11.4.  Adaptive Chosen-Ciphertext Attacks . . . . . . . . . . .  28
   11.5.  Timing Attacks . . . . . . . . . . . . . . . . . . . . .  28
 12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  29
   12.1.  Normative References . . . . . . . . . . . . . . . . . .  29
   12.2.  Informative References . . . . . . . . . . . . . . . . .  30
 Appendix A.  JWE Examples . . . . . . . . . . . . . . . . . . . .  32
   A.1.  Example JWE using RSAES-OAEP and AES GCM  . . . . . . . .  32
     A.1.1.  JOSE Header . . . . . . . . . . . . . . . . . . . . .  32
     A.1.2.  Content Encryption Key (CEK)  . . . . . . . . . . . .  32
     A.1.3.  Key Encryption  . . . . . . . . . . . . . . . . . . .  33
     A.1.4.  Initialization Vector . . . . . . . . . . . . . . . .  34
     A.1.5.  Additional Authenticated Data . . . . . . . . . . . .  35
     A.1.6.  Content Encryption  . . . . . . . . . . . . . . . . .  35
     A.1.7.  Complete Representation . . . . . . . . . . . . . . .  36
     A.1.8.  Validation  . . . . . . . . . . . . . . . . . . . . .  36
   A.2.  Example JWE using RSAES-PKCS1-v1_5 and
         AES_128_CBC_HMAC_SHA_256  . . . . . . . . . . . . . . . .  36
     A.2.1.  JOSE Header . . . . . . . . . . . . . . . . . . . . .  37
     A.2.2.  Content Encryption Key (CEK)  . . . . . . . . . . . .  37
     A.2.3.  Key Encryption  . . . . . . . . . . . . . . . . . . .  38
     A.2.4.  Initialization Vector . . . . . . . . . . . . . . . .  39
     A.2.5.  Additional Authenticated Data . . . . . . . . . . . .  40
     A.2.6.  Content Encryption  . . . . . . . . . . . . . . . . .  40
     A.2.7.  Complete Representation . . . . . . . . . . . . . . .  40
     A.2.8.  Validation  . . . . . . . . . . . . . . . . . . . . .  41
   A.3.  Example JWE Using AES Key Wrap and
         AES_128_CBC_HMAC_SHA_256  . . . . . . . . . . . . . . . .  41
     A.3.1.  JOSE Header . . . . . . . . . . . . . . . . . . . . .  41
     A.3.2.  Content Encryption Key (CEK)  . . . . . . . . . . . .  42
     A.3.3.  Key Encryption  . . . . . . . . . . . . . . . . . . .  42
     A.3.4.  Initialization Vector . . . . . . . . . . . . . . . .  42
     A.3.5.  Additional Authenticated Data . . . . . . . . . . . .  43
     A.3.6.  Content Encryption  . . . . . . . . . . . . . . . . .  43
     A.3.7.  Complete Representation . . . . . . . . . . . . . . .  43
     A.3.8.  Validation  . . . . . . . . . . . . . . . . . . . . .  44
   A.4.  Example JWE Using General JWE JSON Serialization  . . . .  44
     A.4.1.  JWE Per-Recipient Unprotected Headers . . . . . . . .  45
     A.4.2.  JWE Protected Header  . . . . . . . . . . . . . . . .  45
     A.4.3.  JWE Shared Unprotected Header . . . . . . . . . . . .  45
     A.4.4.  Complete JOSE Header Values . . . . . . . . . . . . .  45
     A.4.5.  Additional Authenticated Data . . . . . . . . . . . .  46
     A.4.6.  Content Encryption  . . . . . . . . . . . . . . . . .  46
     A.4.7.  Complete JWE JSON Serialization Representation  . . .  47
   A.5.  Example JWE Using Flattened JWE JSON Serialization  . . .  47
 Appendix B.  Example AES_128_CBC_HMAC_SHA_256 Computation . . . .  48
   B.1.  Extract MAC_KEY and ENC_KEY from Key  . . . . . . . . . .  48
   B.2.  Encrypt Plaintext to Create Ciphertext  . . . . . . . . .  49
   B.3.  64-Bit Big-Endian Representation of AAD Length  . . . . .  49

Jones & Hildebrand Standards Track [Page 3] RFC 7516 JSON Web Encryption (JWE) May 2015

   B.4.  Initialization Vector Value . . . . . . . . . . . . . . .  49
   B.5.  Create Input to HMAC Computation  . . . . . . . . . . . .  50
   B.6.  Compute HMAC Value  . . . . . . . . . . . . . . . . . . .  50
   B.7.  Truncate HMAC Value to Create Authentication Tag  . . . .  50
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  50
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  51

1. Introduction

 JSON Web Encryption (JWE) represents encrypted content using JSON-
 based data structures [RFC7159].  The JWE cryptographic mechanisms
 encrypt and provide integrity protection for an arbitrary sequence of
 octets.
 Two closely related serializations for JWEs 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 JWEs
 as JSON objects and enables the same content to be encrypted to
 multiple parties.  Both share the same cryptographic underpinnings.
 Cryptographic algorithms and identifiers for use with this
 specification are described in the separate JSON Web Algorithms (JWA)
 [JWA] specification and IANA registries defined by that
 specification.  Related digital signature and MAC capabilities are
 described in the separate JSON Web Signature (JWS) [JWS]
 specification.
 Names defined by this specification are short because a core goal is
 for the resulting representations to be compact.

1.1. Notational Conventions

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "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].
 The interpretation should only be applied when the terms appear in
 all capital letters.
 BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per
 Section 2 of [JWS].
 UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation
 of STRING, where STRING is a sequence of zero or more Unicode
 [UNICODE] characters.

Jones & Hildebrand Standards Track [Page 4] RFC 7516 JSON Web Encryption (JWE) May 2015

 ASCII(STRING) denotes the octets of the ASCII [RFC20] representation
 of STRING, where STRING is a sequence of zero or more ASCII
 characters.
 The concatenation of two values A and B is denoted as A || B.

2. Terminology

 The terms "JSON Web Signature (JWS)", "Base64url Encoding",
 "Collision-Resistant Name", "Header Parameter", "JOSE Header", and
 "StringOrURI" are defined by the JWS specification [JWS].
 The terms "Ciphertext", "Digital Signature", "Initialization Vector
 (IV)", "Message Authentication Code (MAC)", and "Plaintext" are
 defined by the "Internet Security Glossary, Version 2" [RFC4949].
 These terms are defined by this specification:
 JSON Web Encryption (JWE)
    A data structure representing an encrypted and integrity-protected
    message.
 Authenticated Encryption with Associated Data (AEAD)
    An AEAD algorithm is one that encrypts the plaintext, allows
    Additional Authenticated Data to be specified, and provides an
    integrated content integrity check over the ciphertext and
    Additional Authenticated Data.  AEAD algorithms accept two inputs,
    the plaintext and the Additional Authenticated Data value, and
    produce two outputs, the ciphertext and the Authentication Tag
    value.  AES Galois/Counter Mode (GCM) is one such algorithm.
 Additional Authenticated Data (AAD)
    An input to an AEAD operation that is integrity protected but not
    encrypted.
 Authentication Tag
    An output of an AEAD operation that ensures the integrity of the
    ciphertext and the Additional Authenticated Data.  Note that some
    algorithms may not use an Authentication Tag, in which case this
    value is the empty octet sequence.
 Content Encryption Key (CEK)
    A symmetric key for the AEAD algorithm used to encrypt the
    plaintext to produce the ciphertext and the Authentication Tag.

Jones & Hildebrand Standards Track [Page 5] RFC 7516 JSON Web Encryption (JWE) May 2015

 JWE Encrypted Key
    Encrypted Content Encryption Key value.  Note that for some
    algorithms, the JWE Encrypted Key value is specified as being the
    empty octet sequence.
 JWE Initialization Vector
    Initialization Vector value 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 AAD
    Additional value to be integrity protected by the authenticated
    encryption operation.  This can only be present when using the JWE
    JSON Serialization.  (Note that this can also be achieved when
    using either the JWE Compact Serialization or the JWE JSON
    Serialization by including the AAD value as an integrity-protected
    Header Parameter value, but at the cost of the value being double
    base64url encoded.)
 JWE Ciphertext
    Ciphertext value resulting from authenticated encryption of the
    plaintext with Additional Authenticated Data.
 JWE Authentication Tag
    Authentication Tag value resulting from authenticated encryption
    of the plaintext with Additional Authenticated Data.
 JWE Protected Header
    JSON object that contains the Header Parameters that are integrity
    protected by the authenticated encryption operation.  These
    parameters apply to all recipients of the JWE.  For the JWE
    Compact Serialization, this comprises the entire JOSE Header.  For
    the JWE JSON Serialization, this is one component of the JOSE
    Header.
 JWE Shared Unprotected Header
    JSON object that contains the Header Parameters that apply to all
    recipients of the JWE that are not integrity protected.  This can
    only be present when using the JWE JSON Serialization.
 JWE Per-Recipient Unprotected Header
    JSON object that contains Header Parameters that apply to a single
    recipient of the JWE.  These Header Parameter values are not
    integrity protected.  This can only be present when using the JWE
    JSON Serialization.
 JWE Compact Serialization
    A representation of the JWE as a compact, URL-safe string.

Jones & Hildebrand Standards Track [Page 6] RFC 7516 JSON Web Encryption (JWE) May 2015

 JWE JSON Serialization
    A representation of the JWE as a JSON object.  The JWE JSON
    Serialization enables the same content to be encrypted to multiple
    parties.  This representation is neither optimized for compactness
    nor URL safe.
 Key Management Mode
    A method of determining the Content Encryption Key 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 CEK value is encrypted to the
    intended recipient using an asymmetric encryption algorithm.
 Key Wrapping
    A Key Management Mode in which the 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 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 CEK value to the
    intended recipient using a symmetric key wrapping algorithm.
 Direct Encryption
    A Key Management Mode in which the CEK value used is the secret
    symmetric key value shared between the parties.

Jones & Hildebrand Standards Track [Page 7] RFC 7516 JSON Web Encryption (JWE) May 2015

3. JSON Web Encryption (JWE) Overview

 JWE represents encrypted content using JSON data structures and
 base64url encoding.  These JSON data structures MAY contain
 whitespace and/or line breaks before or after any JSON values or
 structural characters, in accordance with Section 2 of RFC 7159
 [RFC7159].  A JWE represents these logical values (each of which is
 defined in Section 2):
 o  JOSE Header
 o  JWE Encrypted Key
 o  JWE Initialization Vector
 o  JWE AAD
 o  JWE Ciphertext
 o  JWE Authentication Tag
 For a JWE, the JOSE Header members are the union of the members of
 these values (each of which is defined in Section 2):
 o  JWE Protected Header
 o  JWE Shared Unprotected Header
 o  JWE Per-Recipient Unprotected Header
 JWE utilizes authenticated encryption to ensure the confidentiality
 and integrity of the plaintext and the integrity of the JWE Protected
 Header and the JWE AAD.
 This document defines two serializations for JWEs: a compact, URL-
 safe serialization called the JWE Compact Serialization and a JSON
 serialization called the JWE JSON Serialization.  In both
 serializations, the JWE Protected Header, JWE Encrypted Key, JWE
 Initialization Vector, JWE Ciphertext, and JWE Authentication Tag are
 base64url encoded, since JSON lacks a way to directly represent
 arbitrary octet sequences.  When present, the JWE AAD is also
 base64url encoded.

3.1. JWE Compact Serialization Overview

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

Jones & Hildebrand Standards Track [Page 8] RFC 7516 JSON Web Encryption (JWE) May 2015

 In the JWE Compact Serialization, a JWE is represented as the
 concatenation:
    BASE64URL(UTF8(JWE Protected Header)) || '.' ||
    BASE64URL(JWE Encrypted Key) || '.' ||
    BASE64URL(JWE Initialization Vector) || '.' ||
    BASE64URL(JWE Ciphertext) || '.' ||
    BASE64URL(JWE Authentication Tag)
 See Section 7.1 for more information about the JWE Compact
 Serialization.

3.2. JWE JSON Serialization Overview

 In the JWE JSON Serialization, one or more of the JWE Protected
 Header, JWE Shared Unprotected Header, and JWE Per-Recipient
 Unprotected Header MUST be present.  In this case, the members of the
 JOSE Header are the union of the members of the JWE Protected Header,
 JWE Shared Unprotected Header, and JWE Per-Recipient Unprotected
 Header values that are present.
 In the JWE JSON Serialization, a JWE is represented as a JSON object
 containing some or all of these eight members:
    "protected", with the value BASE64URL(UTF8(JWE Protected Header))
    "unprotected", with the value JWE Shared Unprotected Header
    "header", with the value JWE Per-Recipient Unprotected Header
    "encrypted_key", with the value BASE64URL(JWE Encrypted Key)
    "iv", with the value BASE64URL(JWE Initialization Vector)
    "ciphertext", with the value BASE64URL(JWE Ciphertext)
    "tag", with the value BASE64URL(JWE Authentication Tag)
    "aad", with the value BASE64URL(JWE AAD)
 The six base64url-encoded result strings and the two unprotected JSON
 object values are represented as members within a JSON object.  The
 inclusion of some of these values is OPTIONAL.  The JWE JSON
 Serialization can also encrypt the plaintext to multiple recipients.
 See Section 7.2 for more information about the JWE JSON
 Serialization.

Jones & Hildebrand Standards Track [Page 9] RFC 7516 JSON Web Encryption (JWE) May 2015

3.3. Example JWE

 This example encrypts the plaintext "The true sign of intelligence is
 not knowledge but imagination." to the recipient.
 The following example JWE Protected Header declares that:
 o  The Content Encryption Key is encrypted to the recipient using the
    RSAES-OAEP [RFC3447] algorithm to produce the JWE Encrypted Key.
 o  Authenticated encryption is performed on the plaintext using the
    AES GCM [AES] [NIST.800-38D] algorithm with a 256-bit key to
    produce the ciphertext and the Authentication Tag.
   {"alg":"RSA-OAEP","enc":"A256GCM"}
 Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
 Header)) gives this value:
   eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
 The remaining steps to finish creating this JWE are:
 o  Generate a random Content Encryption Key (CEK).
 o  Encrypt the CEK with the recipient's public key using the RSAES-
    OAEP algorithm to produce the JWE Encrypted Key.
 o  Base64url-encode the JWE Encrypted Key.
 o  Generate a random JWE Initialization Vector.
 o  Base64url-encode the JWE Initialization Vector.
 o  Let the Additional Authenticated Data encryption parameter be
    ASCII(BASE64URL(UTF8(JWE Protected Header))).
 o  Perform authenticated encryption on the plaintext with the AES GCM
    algorithm using the CEK as the encryption key, the JWE
    Initialization Vector, and the Additional Authenticated Data
    value, requesting a 128-bit Authentication Tag output.
 o  Base64url-encode the ciphertext.
 o  Base64url-encode the Authentication Tag.

Jones & Hildebrand Standards Track [Page 10] RFC 7516 JSON Web Encryption (JWE) May 2015

 o  Assemble the final representation: The Compact Serialization of
    this result is the string BASE64URL(UTF8(JWE Protected Header)) ||
    '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE
    Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.'
    || BASE64URL(JWE Authentication Tag).
 The final result in this example (with line breaks for display
 purposes only) is:
   eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
   OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
   ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
   Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
   mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
   1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
   6UklfCpIMfIjf7iGdXKHzg.
   48V1_ALb6US04U3b.
   5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
   SdiwkIr3ajwQzaBtQD_A.
   XFBoMYUZodetZdvTiFvSkQ
 See Appendix A.1 for the complete details of computing this JWE.  See
 Appendix A for additional examples, including examples using the JWE
 JSON Serialization in Sections A.4 and A.5.

4. JOSE Header

 For a JWE, the members of the JSON object(s) representing the JOSE
 Header describe the encryption applied to the plaintext and
 optionally additional properties of the JWE.  The Header Parameter
 names within the JOSE Header MUST be unique, just as described in
 Section 4 of [JWS].  The rules about handling Header Parameters that
 are not understood by the implementation are also the same.  The
 classes of Header Parameter names are likewise the same.

4.1. Registered Header Parameter Names

 The following Header Parameter names for use in JWEs are registered
 in the IANA "JSON Web Signature and Encryption Header Parameters"
 registry established by [JWS], with meanings as defined below.
 As indicated by the common registry, JWSs and JWEs share a common
 Header Parameter space; when a parameter is used by both
 specifications, its usage must be compatible between the
 specifications.

Jones & Hildebrand Standards Track [Page 11] RFC 7516 JSON Web Encryption (JWE) May 2015

4.1.1. "alg" (Algorithm) Header Parameter

 This parameter has the same meaning, syntax, and processing rules as
 the "alg" Header Parameter defined in Section 4.1.1 of [JWS], except
 that the Header Parameter identifies the cryptographic algorithm used
 to encrypt or determine the value of the CEK.  The encrypted content
 is not usable if the "alg" value does not represent a supported
 algorithm, or if the recipient does not have a key that can be used
 with that algorithm.
 A list of defined "alg" values for this use can be found in the IANA
 "JSON Web Signature and Encryption Algorithms" registry established
 by [JWA]; the initial contents of this registry are the values
 defined in Section 4.1 of [JWA].

4.1.2. "enc" (Encryption Algorithm) Header Parameter

 The "enc" (encryption algorithm) Header Parameter identifies the
 content encryption algorithm used to perform authenticated encryption
 on the plaintext to produce the ciphertext and the Authentication
 Tag.  This algorithm MUST be an AEAD algorithm with a specified key
 length.  The encrypted content is not usable if the "enc" value does
 not represent a supported algorithm.  "enc" values should either be
 registered in the IANA "JSON Web Signature and Encryption Algorithms"
 registry established by [JWA] or be a value that contains a
 Collision-Resistant Name.  The "enc" value is a case-sensitive ASCII
 string containing a StringOrURI value.  This Header Parameter MUST be
 present and MUST be understood and processed by implementations.
 A list of defined "enc" values for this use can be found in the IANA
 "JSON Web Signature and Encryption Algorithms" registry established
 by [JWA]; the initial contents of this registry are the values
 defined in Section 5.1 of [JWA].

4.1.3. "zip" (Compression Algorithm) Header Parameter

 The "zip" (compression algorithm) applied to the plaintext before
 encryption, if any.  The "zip" value defined by this specification
 is:
 o  "DEF" - Compression with the DEFLATE [RFC1951] algorithm
 Other values MAY be used.  Compression algorithm values can be
 registered in the IANA "JSON Web Encryption Compression Algorithms"
 registry established by [JWA].  The "zip" value is a case-sensitive
 string.  If no "zip" parameter is present, no compression is applied
 to the plaintext before encryption.  When used, this Header Parameter
 MUST be integrity protected; therefore, it MUST occur only within the

Jones & Hildebrand Standards Track [Page 12] RFC 7516 JSON Web Encryption (JWE) May 2015

 JWE Protected Header.  Use of this Header Parameter is OPTIONAL.
 This Header Parameter MUST be understood and processed by
 implementations.

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

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

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

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

4.1.6. "kid" (Key ID) Header Parameter

 This parameter has the same meaning, syntax, and processing rules as
 the "kid" Header Parameter defined in Section 4.1.4 of [JWS], except
 that the key hint references the public key to which the JWE was
 encrypted; this can be used to determine the private key needed to
 decrypt the JWE.  This parameter allows originators to explicitly
 signal a change of key to JWE recipients.

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

 This parameter has the same meaning, syntax, and processing rules as
 the "x5u" Header Parameter defined in Section 4.1.5 of [JWS], except
 that the X.509 public key certificate or certificate chain [RFC5280]
 contains the public key to which the JWE was encrypted; this can be
 used to determine the private key needed to decrypt the JWE.

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

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

Jones & Hildebrand Standards Track [Page 13] RFC 7516 JSON Web Encryption (JWE) May 2015

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

 This parameter has the same meaning, syntax, and processing rules as
 the "x5t" Header Parameter defined in Section 4.1.7 of [JWS], except
 that the certificate referenced by the thumbprint contains the public
 key to which the JWE was encrypted; this can be used to determine the
 private key needed to decrypt the JWE.  Note that certificate
 thumbprints are also sometimes known as certificate fingerprints.

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

       Parameter
 This parameter has the same meaning, syntax, and processing rules as
 the "x5t#S256" Header Parameter defined in Section 4.1.8 of [JWS],
 except that the certificate referenced by the thumbprint contains the
 public key to which the JWE was encrypted; this can be used to
 determine the private key needed to decrypt the JWE.  Note that
 certificate thumbprints are also sometimes known as certificate
 fingerprints.

4.1.11. "typ" (Type) Header Parameter

 This parameter has the same meaning, syntax, and processing rules as
 the "typ" Header Parameter defined in Section 4.1.9 of [JWS], except
 that the type is that of this complete JWE.

4.1.12. "cty" (Content Type) Header Parameter

 This parameter has the same meaning, syntax, and processing rules as
 the "cty" Header Parameter defined in Section 4.1.10 of [JWS], except
 that the type is that of the secured content (the plaintext).

4.1.13. "crit" (Critical) Header Parameter

 This parameter has the same meaning, syntax, and processing rules as
 the "crit" Header Parameter defined in Section 4.1.11 of [JWS],
 except that Header Parameters for a JWE are being referred to, rather
 than Header Parameters for a JWS.

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 established by [JWS] or be a
 Public Name: a value that contains a Collision-Resistant Name.  In
 each case, the definer of the name or value needs to take reasonable

Jones & Hildebrand Standards Track [Page 14] RFC 7516 JSON Web Encryption (JWE) May 2015

 precautions to make sure they are in control of the part of the
 namespace they use to define the Header Parameter name.
 New Header Parameters should be introduced sparingly, as they can
 result in non-interoperable JWEs.

4.3. Private Header Parameter Names

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

5. Producing and Consuming JWEs

5.1. Message Encryption

 The message encryption process is as follows.  The order of the steps
 is not significant in cases where there are no dependencies between
 the inputs and outputs of the steps.
 1.   Determine the Key Management Mode employed by the algorithm used
      to determine the Content Encryption Key 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 CEK value.  See RFC
      4086 [RFC4086] for considerations on generating random values.
      The CEK MUST have a length equal to that required for the
      content encryption algorithm.
 3.   When Direct Key Agreement or Key Agreement with Key Wrapping are
      employed, use the key agreement algorithm to compute the value
      of the agreed upon key.  When Direct Key Agreement is employed,
      let the CEK be the agreed upon key.  When Key Agreement with Key
      Wrapping is employed, the agreed upon key will be used to wrap
      the CEK.
 4.   When Key Wrapping, Key Encryption, or Key Agreement with Key
      Wrapping are employed, encrypt the CEK to the recipient and let
      the result be the JWE Encrypted Key.
 5.   When Direct Key Agreement or Direct Encryption are employed, let
      the JWE Encrypted Key be the empty octet sequence.

Jones & Hildebrand Standards Track [Page 15] RFC 7516 JSON Web Encryption (JWE) May 2015

 6.   When Direct Encryption is employed, let the CEK be the shared
      symmetric key.
 7.   Compute the encoded key value BASE64URL(JWE Encrypted Key).
 8.   If the JWE JSON Serialization is being used, repeat this process
      (steps 1-7) for each recipient.
 9.   Generate a random JWE Initialization Vector of the correct size
      for the content encryption algorithm (if required for the
      algorithm); otherwise, let the JWE Initialization Vector be the
      empty octet sequence.
 10.  Compute the encoded Initialization Vector value BASE64URL(JWE
      Initialization Vector).
 11.  If a "zip" parameter was included, compress the plaintext using
      the specified compression algorithm and let M be the octet
      sequence representing the compressed plaintext; otherwise, let M
      be the octet sequence representing the plaintext.
 12.  Create the JSON object(s) containing the desired set of Header
      Parameters, which together comprise the JOSE Header: one or more
      of the JWE Protected Header, the JWE Shared Unprotected Header,
      and the JWE Per-Recipient Unprotected Header.
 13.  Compute the Encoded Protected Header value BASE64URL(UTF8(JWE
      Protected Header)).  If the JWE Protected Header is not present
      (which can only happen when using the JWE JSON Serialization and
      no "protected" member is present), let this value be the empty
      string.
 14.  Let the Additional Authenticated Data encryption parameter be
      ASCII(Encoded Protected Header).  However, if a JWE AAD value is
      present (which can only be the case when using the JWE JSON
      Serialization), instead let the Additional Authenticated Data
      encryption parameter be ASCII(Encoded Protected Header || '.' ||
      BASE64URL(JWE AAD)).
 15.  Encrypt M using the CEK, the JWE Initialization Vector, and the
      Additional Authenticated Data value using the specified content
      encryption algorithm to create the JWE Ciphertext value and the
      JWE Authentication Tag (which is the Authentication Tag output
      from the encryption operation).
 16.  Compute the encoded ciphertext value BASE64URL(JWE Ciphertext).

Jones & Hildebrand Standards Track [Page 16] RFC 7516 JSON Web Encryption (JWE) May 2015

 17.  Compute the encoded Authentication Tag value BASE64URL(JWE
      Authentication Tag).
 18.  If a JWE AAD value is present, compute the encoded AAD value
      BASE64URL(JWE AAD).
 19.  Create the desired serialized output.  The Compact Serialization
      of this result is the string BASE64URL(UTF8(JWE Protected
      Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' ||
      BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE
      Ciphertext) || '.' || BASE64URL(JWE Authentication Tag).  The
      JWE JSON Serialization is described in Section 7.2.

5.2. Message Decryption

 The message decryption process is the reverse of the encryption
 process.  The order of the steps is not significant in cases where
 there are no dependencies between the inputs and outputs of the
 steps.  If any of these steps fail, the encrypted content cannot be
 validated.
 When there are multiple recipients, it is an application decision
 which of the recipients' encrypted content must successfully validate
 for the JWE to be accepted.  In some cases, encrypted content for all
 recipients must successfully validate or the JWE will be considered
 invalid.  In other cases, only the encrypted content for a single
 recipient needs to be successfully validated.  However, in all cases,
 the encrypted content for at least one recipient MUST successfully
 validate or the JWE MUST be considered invalid.
 1.   Parse the JWE representation to extract the serialized values
      for the components of the JWE.  When using the JWE Compact
      Serialization, these components are the base64url-encoded
      representations of the JWE Protected Header, the JWE Encrypted
      Key, the JWE Initialization Vector, the JWE Ciphertext, and the
      JWE Authentication Tag, and when using the JWE JSON
      Serialization, these components also include the base64url-
      encoded representation of the JWE AAD and the unencoded JWE
      Shared Unprotected Header and JWE Per-Recipient Unprotected
      Header values.  When using the JWE Compact Serialization, the
      JWE Protected Header, the JWE Encrypted Key, the JWE
      Initialization Vector, the JWE Ciphertext, and the JWE
      Authentication Tag are represented as base64url-encoded values
      in that order, with each value being separated from the next by
      a single period ('.') character, resulting in exactly four
      delimiting period characters being used.  The JWE JSON
      Serialization is described in Section 7.2.

Jones & Hildebrand Standards Track [Page 17] RFC 7516 JSON Web Encryption (JWE) May 2015

 2.   Base64url decode the encoded representations of the JWE
      Protected Header, the JWE Encrypted Key, the JWE Initialization
      Vector, the JWE Ciphertext, the JWE Authentication Tag, and the
      JWE AAD, following the restriction that no line breaks,
      whitespace, or other additional characters have been used.
 3.   Verify that the octet sequence resulting from decoding the
      encoded JWE Protected Header is a UTF-8-encoded representation
      of a completely valid JSON object conforming to RFC 7159
      [RFC7159]; let the JWE Protected Header be this JSON object.
 4.   If using the JWE Compact Serialization, let the JOSE Header be
      the JWE Protected Header.  Otherwise, when using the JWE JSON
      Serialization, let the JOSE Header be the union of the members
      of the JWE Protected Header, the JWE Shared Unprotected Header
      and the corresponding JWE Per-Recipient Unprotected Header, all
      of which must be completely valid JSON objects.  During this
      step, verify that the resulting JOSE Header does 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 object
      values that together comprise the JOSE Header.
 5.   Verify that the implementation understands and can process all
      fields that it is required to support, whether required by this
      specification, by the algorithms being used, or by the "crit"
      Header Parameter value, and that the values of those parameters
      are also understood and supported.
 6.   Determine the Key Management Mode employed by the algorithm
      specified by the "alg" (algorithm) Header Parameter.
 7.   Verify that the JWE uses a key known to the recipient.
 8.   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 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.
 9.   When Key Wrapping, Key Encryption, or Key Agreement with Key
      Wrapping are employed, decrypt the JWE Encrypted Key to produce
      the CEK.  The CEK MUST have a length equal to that required for
      the content encryption algorithm.  Note that when there are
      multiple recipients, each recipient will only be able to decrypt
      JWE Encrypted Key values that were encrypted to a key in that
      recipient's possession.  It is therefore normal to only be able

Jones & Hildebrand Standards Track [Page 18] RFC 7516 JSON Web Encryption (JWE) May 2015

      to decrypt one of the per-recipient JWE Encrypted Key values to
      obtain the CEK value.  Also, see Section 11.5 for security
      considerations on mitigating timing attacks.
 10.  When Direct Key Agreement or Direct Encryption are employed,
      verify that the JWE Encrypted Key value is an empty octet
      sequence.
 11.  When Direct Encryption is employed, let the CEK be the shared
      symmetric key.
 12.  Record whether the CEK could be successfully determined for this
      recipient or not.
 13.  If the JWE JSON Serialization is being used, repeat this process
      (steps 4-12) for each recipient contained in the representation.
 14.  Compute the Encoded Protected Header value BASE64URL(UTF8(JWE
      Protected Header)).  If the JWE Protected Header is not present
      (which can only happen when using the JWE JSON Serialization and
      no "protected" member is present), let this value be the empty
      string.
 15.  Let the Additional Authenticated Data encryption parameter be
      ASCII(Encoded Protected Header).  However, if a JWE AAD value is
      present (which can only be the case when using the JWE JSON
      Serialization), instead let the Additional Authenticated Data
      encryption parameter be ASCII(Encoded Protected Header || '.' ||
      BASE64URL(JWE AAD)).
 16.  Decrypt the JWE Ciphertext using the CEK, the JWE Initialization
      Vector, the Additional Authenticated Data value, and the JWE
      Authentication Tag (which is the Authentication Tag input to the
      calculation) using the specified content encryption algorithm,
      returning the decrypted plaintext and validating 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.
 17.  If a "zip" parameter was included, uncompress the decrypted
      plaintext using the specified compression algorithm.
 18.  If there was no recipient for which all of the decryption steps
      succeeded, then the JWE MUST be considered invalid.  Otherwise,
      output the plaintext.  In the JWE JSON Serialization case, also
      return a result to the application indicating for which of the
      recipients the decryption succeeded and failed.

Jones & Hildebrand Standards Track [Page 19] RFC 7516 JSON Web Encryption (JWE) May 2015

 Finally, note that it is an application decision which algorithms may
 be used in a given context.  Even if a JWE can be successfully
 decrypted, unless the algorithms used in the JWE are acceptable to
 the application, it SHOULD consider the JWE to be invalid.

5.3. String Comparison Rules

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

6. Key Identification

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

7. Serializations

 JWEs use one of two serializations: the JWE Compact Serialization or
 the JWE JSON Serialization.  Applications using this specification
 need to specify what serialization and serialization features are
 used for that application.  For instance, applications might specify
 that only the JWE JSON Serialization is used, that only JWE JSON
 Serialization support for a single recipient is used, or that support
 for multiple recipients is used.  JWE implementations only need to
 implement the features needed for the applications they are designed
 to support.

7.1. JWE Compact Serialization

 The JWE Compact Serialization represents encrypted content as a
 compact, URL-safe string.  This string is:
    BASE64URL(UTF8(JWE Protected Header)) || '.' ||
    BASE64URL(JWE Encrypted Key) || '.' ||
    BASE64URL(JWE Initialization Vector) || '.' ||
    BASE64URL(JWE Ciphertext) || '.' ||
    BASE64URL(JWE Authentication Tag)
 Only one recipient is supported by the JWE Compact Serialization and
 it provides no syntax to represent JWE Shared Unprotected Header, JWE
 Per-Recipient Unprotected Header, or JWE AAD values.

7.2. JWE JSON Serialization

 The JWE JSON Serialization represents encrypted content as a JSON
 object.  This representation is neither optimized for compactness nor
 URL safe.

Jones & Hildebrand Standards Track [Page 20] RFC 7516 JSON Web Encryption (JWE) May 2015

 Two closely related syntaxes are defined for the JWE JSON
 Serialization: a fully general syntax, with which content can be
 encrypted to more than one recipient, and a flattened syntax, which
 is optimized for the single-recipient case.

7.2.1. General JWE JSON Serialization Syntax

 The following members are defined for use in top-level JSON objects
 used for the fully general JWE JSON Serialization syntax:
 protected
    The "protected" member MUST be present and contain the value
    BASE64URL(UTF8(JWE Protected Header)) when the JWE Protected
    Header value is non-empty; otherwise, it MUST be absent.  These
    Header Parameter values are integrity protected.
 unprotected
    The "unprotected" member MUST be present and contain the value JWE
    Shared Unprotected Header when the JWE Shared Unprotected Header
    value is non-empty; otherwise, it MUST be absent.  This value is
    represented as an unencoded JSON object, rather than as a string.
    These Header Parameter values are not integrity protected.
 iv
    The "iv" member MUST be present and contain the value
    BASE64URL(JWE Initialization Vector) when the JWE Initialization
    Vector value is non-empty; otherwise, it MUST be absent.
 aad
    The "aad" member MUST be present and contain the value
    BASE64URL(JWE AAD)) when the JWE AAD value is non-empty;
    otherwise, it MUST be absent.  A JWE AAD value can be included to
    supply a base64url-encoded value to be integrity protected but not
    encrypted.
 ciphertext
    The "ciphertext" member MUST be present and contain the value
    BASE64URL(JWE Ciphertext).
 tag
    The "tag" member MUST be present and contain the value
    BASE64URL(JWE Authentication Tag) when the JWE Authentication Tag
    value is non-empty; otherwise, it MUST be absent.
 recipients
    The "recipients" member value MUST be an array of JSON objects.
    Each object contains information specific to a single recipient.
    This member MUST be present with exactly one array element per

Jones & Hildebrand Standards Track [Page 21] RFC 7516 JSON Web Encryption (JWE) May 2015

    recipient, even if some or all of the array element values are the
    empty JSON object "{}" (which can happen when all Header Parameter
    values are shared between all recipients and when no encrypted key
    is used, such as when doing Direct Encryption).
 The following members are defined for use in the JSON objects that
 are elements of the "recipients" array:
 header
    The "header" member MUST be present and contain the value JWE Per-
    Recipient Unprotected Header when the JWE Per-Recipient
    Unprotected Header value is non-empty; otherwise, it MUST be
    absent.  This value is represented as an unencoded JSON object,
    rather than as a string.  These Header Parameter values are not
    integrity protected.
 encrypted_key
    The "encrypted_key" member MUST be present and contain the value
    BASE64URL(JWE Encrypted Key) when the JWE Encrypted Key value is
    non-empty; otherwise, it MUST be absent.
 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.
 Additional members can be present in both the JSON objects defined
 above; if not understood by implementations encountering them, they
 MUST be ignored.
 Some Header Parameters, including the "alg" parameter, can be shared
 among all recipient computations.  Header Parameters in the JWE
 Protected Header and JWE Shared Unprotected Header values are shared
 among all recipients.
 The Header Parameter values used when creating or validating per-
 recipient ciphertext and Authentication Tag values are the union of
 the three sets of Header Parameter values that may be present: (1)
 the JWE Protected Header represented in the "protected" member, (2)
 the JWE Shared Unprotected Header represented in the "unprotected"
 member, and (3) the JWE Per-Recipient Unprotected Header represented
 in the "header" member of the recipient's array element.  The union
 of these sets of Header Parameters comprises the JOSE Header.  The
 Header Parameter names in the three locations MUST be disjoint.
 Each JWE Encrypted Key value is computed using the parameters of the
 corresponding JOSE Header value in the same manner as for the JWE
 Compact Serialization.  This has the desirable property that each JWE
 Encrypted Key value in the "recipients" array is identical to the

Jones & Hildebrand Standards Track [Page 22] RFC 7516 JSON Web Encryption (JWE) May 2015

 value that would have been computed for the same parameter in the JWE
 Compact Serialization.  Likewise, the JWE Ciphertext and JWE
 Authentication Tag values match those produced for the JWE Compact
 Serialization, provided that the JWE Protected Header value (which
 represents the integrity-protected Header Parameter values) matches
 that used in the JWE Compact Serialization.
 All recipients use the same JWE Protected Header, JWE Initialization
 Vector, JWE Ciphertext, and JWE Authentication Tag values, when
 present, 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 algorithm) Header
 Parameter value in the JOSE Header for each recipient and any
 parameters of that algorithm MUST be the same.
 In summary, the syntax of a JWE using the general JWE JSON
 Serialization is as follows:
   {
    "protected":"<integrity-protected shared header contents>",
    "unprotected":<non-integrity-protected shared header contents>,
    "recipients":[
     {"header":<per-recipient unprotected header 1 contents>,
      "encrypted_key":"<encrypted key 1 contents>"},
     ...
     {"header":<per-recipient unprotected header N contents>,
      "encrypted_key":"<encrypted key N contents>"}],
    "aad":"<additional authenticated data contents>",
    "iv":"<initialization vector contents>",
    "ciphertext":"<ciphertext contents>",
    "tag":"<authentication tag contents>"
   }
 See Appendix A.4 for an example JWE using the general JWE JSON
 Serialization syntax.

7.2.2. Flattened JWE JSON Serialization Syntax

 The flattened JWE JSON Serialization syntax is based upon the general
 syntax, but flattens it, optimizing it for the single-recipient case.
 It flattens it by removing the "recipients" member and instead
 placing those members defined for use in the "recipients" array (the
 "header" and "encrypted_key" members) in the top-level JSON object
 (at the same level as the "ciphertext" member).

Jones & Hildebrand Standards Track [Page 23] RFC 7516 JSON Web Encryption (JWE) May 2015

 The "recipients" member MUST NOT be present when using this syntax.
 Other than this syntax difference, JWE JSON Serialization objects
 using the flattened syntax are processed identically to those using
 the general syntax.
 In summary, the syntax of a JWE using the flattened JWE JSON
 Serialization is as follows:
   {
    "protected":"<integrity-protected header contents>",
    "unprotected":<non-integrity-protected header contents>,
    "header":<more non-integrity-protected header contents>,
    "encrypted_key":"<encrypted key contents>",
    "aad":"<additional authenticated data contents>",
    "iv":"<initialization vector contents>",
    "ciphertext":"<ciphertext contents>",
    "tag":"<authentication tag contents>"
   }
 Note that when using the flattened syntax, just as when using the
 general syntax, any unprotected Header Parameter values can reside in
 either the "unprotected" member or the "header" member, or in both.
 See Appendix A.5 for an example JWE using the flattened JWE JSON
 Serialization syntax.

8. TLS Requirements

 The Transport Layer Security (TLS) requirements for this
 specification are the same as those defined in Section 8 of [JWS].

9. Distinguishing between JWS and JWE Objects

 There are several ways of distinguishing whether an object is a JWS
 or JWE.  All these methods will yield the same result for all legal
 input values; they may yield different results for malformed inputs.
 o  If the object is using the JWS Compact Serialization or the JWE
    Compact Serialization, the number of base64url-encoded segments
    separated by period ('.') characters differs for JWSs and JWEs.
    JWSs have three segments separated by two period ('.') characters.
    JWEs have five segments separated by four period ('.') characters.
 o  If the object is using the JWS JSON Serialization or the JWE JSON
    Serialization, the members used will be different.  JWSs have a
    "payload" member and JWEs do not.  JWEs have a "ciphertext" member
    and JWSs do not.

Jones & Hildebrand Standards Track [Page 24] RFC 7516 JSON Web Encryption (JWE) May 2015

 o  The JOSE Header for a JWS can be distinguished from the JOSE
    Header for a JWE 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.  (Extracting the "alg" value to examine is
    straightforward when using the JWS Compact Serialization or the
    JWE Compact Serialization and may be more difficult when using the
    JWS JSON Serialization or the JWE JSON Serialization.)
 o  The JOSE Header for a JWS can also be distinguished from the JOSE
    Header for a JWE by determining whether an "enc" (encryption
    algorithm) member exists.  If the "enc" member exists, it is a
    JWE; otherwise, it is a JWS.

10. IANA Considerations

10.1. JSON Web Signature and Encryption Header Parameters Registration

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

10.1.1. Registry Contents

 o  Header Parameter Name: "alg"
 o  Header Parameter Description: Algorithm
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.1 of RFC 7516
 o  Header Parameter Name: "enc"
 o  Header Parameter Description: Encryption Algorithm
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.2 of RFC 7516
 o  Header Parameter Name: "zip"
 o  Header Parameter Description: Compression Algorithm
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.3 of RFC 7516

Jones & Hildebrand Standards Track [Page 25] RFC 7516 JSON Web Encryption (JWE) May 2015

 o  Header Parameter Name: "jku"
 o  Header Parameter Description: JWK Set URL
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.4 of RFC 7516
 o  Header Parameter Name: "jwk"
 o  Header Parameter Description: JSON Web Key
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.5 of RFC 7516
 o  Header Parameter Name: "kid"
 o  Header Parameter Description: Key ID
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.6 of RFC 7516
 o  Header Parameter Name: "x5u"
 o  Header Parameter Description: X.509 URL
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.7 of RFC 7516
 o  Header Parameter Name: "x5c"
 o  Header Parameter Description: X.509 Certificate Chain
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.8 of RFC 7516
 o  Header Parameter Name: "x5t"
 o  Header Parameter Description: X.509 Certificate SHA-1 Thumbprint
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.9 of RFC 7516
 o  Header Parameter Name: "x5t#S256"
 o  Header Parameter Description: X.509 Certificate SHA-256 Thumbprint
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.10 of RFC 7516
 o  Header Parameter Name: "typ"
 o  Header Parameter Description: Type
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.11 of RFC 7516

Jones & Hildebrand Standards Track [Page 26] RFC 7516 JSON Web Encryption (JWE) May 2015

 o  Header Parameter Name: "cty"
 o  Header Parameter Description: Content Type
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.12 of RFC 7516
 o  Header Parameter Name: "crit"
 o  Header Parameter Description: Critical
 o  Header Parameter Usage Location(s): JWE
 o  Change Controller: IESG
 o  Specification Document(s): Section 4.1.13 of RFC 7516

11. Security Considerations

 All of the security issues that are pertinent to any cryptographic
 application must be addressed by JWS/JWE/JWK agents.  Among these
 issues are protecting the user's asymmetric private and symmetric
 secret keys and employing countermeasures to various attacks.
 All the security considerations in the JWS specification also apply
 to this specification.  Likewise, all the security considerations in
 XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411] also apply, other
 than those that are XML specific.

11.1. Key Entropy and Random Values

 See Section 10.1 of [JWS] for security considerations on key entropy
 and random values.  In addition to the uses of random values listed
 there, note that random values are also used for Content Encryption
 Keys (CEKs) and Initialization Vectors (IVs) when performing
 encryption.

11.2. Key Protection

 See Section 10.2 of [JWS] for security considerations on key
 protection.  In addition to the keys listed there that must be
 protected, implementations performing encryption must protect the key
 encryption key and the Content Encryption Key.  Compromise of the key
 encryption key may result in the disclosure of all contents protected
 with that key.  Similarly, compromise of the Content Encryption Key
 may result in disclosure of the associated encrypted content.

Jones & Hildebrand Standards Track [Page 27] RFC 7516 JSON Web Encryption (JWE) May 2015

11.3. Using Matching Algorithm Strengths

 Algorithms of matching strengths should be used together whenever
 possible.  For instance, when AES Key Wrap is used with a given key
 size, using the same key size is recommended when AES GCM is also
 used.  If the key encryption and content encryption algorithms are
 different, the effective security is determined by the weaker of the
 two algorithms.
 Also, see RFC 3766 [RFC3766] for information on determining strengths
 for public keys used for exchanging symmetric keys.

11.4. Adaptive Chosen-Ciphertext Attacks

 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" Header Parameter from "RSA-OAEP" to "RSA1_5" in order to
 generate a formatting error that can be detected and used to recover
 the CEK even if RSAES-OAEP was used to encrypt the CEK.  It is
 therefore particularly important to report all formatting errors to
 the CEK, Additional Authenticated Data, or ciphertext as a single
 error when the encrypted content is rejected.
 Additionally, this type of attack can be prevented by restricting the
 use of a key to a limited set of algorithms -- usually one.  This
 means, for instance, that if the key is marked as being for
 "RSA-OAEP" only, any attempt to decrypt a message using the "RSA1_5"
 algorithm with that key should fail immediately due to invalid use of
 the key.

11.5. Timing Attacks

 To mitigate the attacks described in RFC 3218 [RFC3218], the
 recipient MUST NOT distinguish between format, padding, and length
 errors of encrypted keys.  It is strongly recommended, in the event
 of receiving an improperly formatted key, that the recipient
 substitute a randomly generated CEK and proceed to the next step, to
 mitigate timing attacks.

Jones & Hildebrand Standards Track [Page 28] RFC 7516 JSON Web Encryption (JWE) May 2015

12. References

12.1. Normative References

 [JWA]      Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
            DOI 10.17487/RFC7518, May 2015,
            <http://www.rfc-editor.org/info/rfc7518>.
 [JWK]      Jones, M., "JSON Web Key (JWK)", RFC 7517,
            DOI 10.17487/RFC7517, May 2015,
            <http://www.rfc-editor.org/info/rfc7517>.
 [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
            Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
            2015, <http://www.rfc-editor.org/info/rfc7515>.
 [RFC1951]  Deutsch, P., "DEFLATE Compressed Data Format Specification
            version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
            <http://www.rfc-editor.org/info/rfc1951>.
 [RFC20]    Cerf, V., "ASCII format for Network Interchange", STD 80,
            RFC 20, DOI 10.17487/RFC0020, October 1969,
            <http://www.rfc-editor.org/info/rfc20>.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
            2003, <http://www.rfc-editor.org/info/rfc3629>.
 [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
            FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
            <http://www.rfc-editor.org/info/rfc4949>.
 [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, DOI 10.17487/RFC5280, May 2008,
            <http://www.rfc-editor.org/info/rfc5280>.
 [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
            Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
            2014, <http://www.rfc-editor.org/info/rfc7159>.

Jones & Hildebrand Standards Track [Page 29] RFC 7516 JSON Web Encryption (JWE) May 2015

 [UNICODE]  The Unicode Consortium, "The Unicode Standard",
            <http://www.unicode.org/versions/latest/>.

12.2. Informative References

 [AES]      National Institute of Standards and Technology (NIST),
            "Advanced Encryption Standard (AES)", FIPS PUB 197,
            November 2001, <http://csrc.nist.gov/publications/
            fips/fips197/fips-197.pdf>.
 [JSE]      Bradley, J. and N. Sakimura (editor), "JSON Simple
            Encryption", September 2010,
            <http://jsonenc.info/enc/1.0/>.
 [JSMS]     Rescorla, E. and J. Hildebrand, "JavaScript Message
            Security Format", Work in Progress,
            draft-rescorla-jsms-00, March 2011.
 [NIST.800-38D]
            National Institute of Standards and Technology (NIST),
            "Recommendation for Block Cipher Modes of Operation:
            Galois/Counter Mode (GCM) and GMAC", NIST PUB 800-38D,
            November 2007, <http://csrc.nist.gov/publications/
            nistpubs/800-38D/SP-800-38D.pdf>.
 [RFC3218]  Rescorla, E., "Preventing the Million Message Attack on
            Cryptographic Message Syntax", RFC 3218,
            DOI 10.17487/RFC3218, January 2002,
            <http://www.rfc-editor.org/info/rfc3218>.
 [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography
            Standards (PKCS) #1: RSA Cryptography Specifications
            Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February
            2003, <http://www.rfc-editor.org/info/rfc3447>.
 [RFC3766]  Orman, H. and P. Hoffman, "Determining Strengths For
            Public Keys Used For Exchanging Symmetric Keys", BCP 86,
            RFC 3766, DOI 10.17487/RFC3766, April 2004,
            <http://www.rfc-editor.org/info/rfc3766>.
 [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
            "Randomness Requirements for Security", BCP 106, RFC 4086,
            DOI 10.17487/RFC4086, June 2005,
            <http://www.rfc-editor.org/info/rfc4086>.

Jones & Hildebrand Standards Track [Page 30] RFC 7516 JSON Web Encryption (JWE) May 2015

 [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
            RFC 5652, DOI 10.17487/RFC5652, September 2009,
            <http://www.rfc-editor.org/info/rfc5652>.
 [W3C.REC-xmlenc-core1-20130411]
            Eastlake, D., Reagle, J., Hirsch, F., and T. Roessler,
            "XML Encryption Syntax and Processing Version 1.1", World
            Wide Web Consortium Recommendation
            REC-xmlenc-core1-20130411, April 2013,
            <http://www.w3.org/TR/2013/REC-xmlenc-core1-20130411/>.

Jones & Hildebrand Standards Track [Page 31] RFC 7516 JSON Web Encryption (JWE) May 2015

Appendix A. JWE Examples

 This section provides examples of JWE computations.

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

 This example encrypts the plaintext "The true sign of intelligence is
 not knowledge but imagination." to the recipient using RSAES-OAEP for
 key encryption and AES GCM for content encryption.  The
 representation of this plaintext (using JSON array notation) is:
 [84, 104, 101, 32, 116, 114, 117, 101, 32, 115, 105, 103, 110, 32,
 111, 102, 32, 105, 110, 116, 101, 108, 108, 105, 103, 101, 110, 99,
 101, 32, 105, 115, 32, 110, 111, 116, 32, 107, 110, 111, 119, 108,
 101, 100, 103, 101, 32, 98, 117, 116, 32, 105, 109, 97, 103, 105,
 110, 97, 116, 105, 111, 110, 46]

A.1.1. JOSE Header

 The following example JWE Protected Header declares that:
 o  The Content Encryption Key is encrypted to the recipient using the
    RSAES-OAEP algorithm to produce the JWE Encrypted Key.
 o  Authenticated encryption is performed on the plaintext using the
    AES GCM algorithm with a 256-bit key to produce the ciphertext and
    the Authentication Tag.
   {"alg":"RSA-OAEP","enc":"A256GCM"}
 Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
 Header)) gives this value:
   eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

A.1.2. Content Encryption Key (CEK)

 Generate a 256-bit random CEK.  In this example, the value (using
 JSON array notation) 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]

Jones & Hildebrand Standards Track [Page 32] RFC 7516 JSON Web Encryption (JWE) May 2015

A.1.3. Key Encryption

 Encrypt the CEK with the recipient's public key using the RSAES-OAEP
 algorithm to produce the JWE Encrypted Key.  This example uses the
 RSA key represented in JSON Web Key [JWK] format below (with line
 breaks within values for display purposes only):
   {"kty":"RSA",
    "n":"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW
         cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S
         psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a
         sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS
         tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj
         YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw",
    "e":"AQAB",
    "d":"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N
         WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9
         3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk
         qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl
         t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd
         VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ",
    "p":"1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ-
         SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf
         fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0",
    "q":"wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm
         UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX
         IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc",
    "dp":"ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL
         hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827
         rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE",
    "dq":"Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj
         ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB
         UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis",
    "qi":"VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7
         AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3
         eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY"
   }

Jones & Hildebrand Standards Track [Page 33] RFC 7516 JSON Web Encryption (JWE) May 2015

 The resulting JWE Encrypted Key value is:
 [56, 163, 154, 192, 58, 53, 222, 4, 105, 218, 136, 218, 29, 94, 203,
 22, 150, 92, 129, 94, 211, 232, 53, 89, 41, 60, 138, 56, 196, 216,
 82, 98, 168, 76, 37, 73, 70, 7, 36, 8, 191, 100, 136, 196, 244, 220,
 145, 158, 138, 155, 4, 117, 141, 230, 199, 247, 173, 45, 182, 214,
 74, 177, 107, 211, 153, 11, 205, 196, 171, 226, 162, 128, 171, 182,
 13, 237, 239, 99, 193, 4, 91, 219, 121, 223, 107, 167, 61, 119, 228,
 173, 156, 137, 134, 200, 80, 219, 74, 253, 56, 185, 91, 177, 34, 158,
 89, 154, 205, 96, 55, 18, 138, 43, 96, 218, 215, 128, 124, 75, 138,
 243, 85, 25, 109, 117, 140, 26, 155, 249, 67, 167, 149, 231, 100, 6,
 41, 65, 214, 251, 232, 87, 72, 40, 182, 149, 154, 168, 31, 193, 126,
 215, 89, 28, 111, 219, 125, 182, 139, 235, 195, 197, 23, 234, 55, 58,
 63, 180, 68, 202, 206, 149, 75, 205, 248, 176, 67, 39, 178, 60, 98,
 193, 32, 238, 122, 96, 158, 222, 57, 183, 111, 210, 55, 188, 215,
 206, 180, 166, 150, 166, 106, 250, 55, 229, 72, 40, 69, 214, 216,
 104, 23, 40, 135, 212, 28, 127, 41, 80, 175, 174, 168, 115, 171, 197,
 89, 116, 92, 103, 246, 83, 216, 182, 176, 84, 37, 147, 35, 45, 219,
 172, 99, 226, 233, 73, 37, 124, 42, 72, 49, 242, 35, 127, 184, 134,
 117, 114, 135, 206]
 Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
 this value (with line breaks for display purposes only):
   OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
   ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
   Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
   mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
   1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
   6UklfCpIMfIjf7iGdXKHzg

A.1.4. Initialization Vector

 Generate a random 96-bit JWE Initialization Vector.  In this example,
 the value is:
 [227, 197, 117, 252, 2, 219, 233, 68, 180, 225, 77, 219]
 Encoding this JWE Initialization Vector as BASE64URL(JWE
 Initialization Vector) gives this value:
   48V1_ALb6US04U3b

Jones & Hildebrand Standards Track [Page 34] RFC 7516 JSON Web Encryption (JWE) May 2015

A.1.5. Additional Authenticated Data

 Let the Additional Authenticated Data encryption parameter be
 ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:
 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
 116, 84, 48, 70, 70, 85, 67, 73, 115, 73, 109, 86, 117, 89, 121, 73,
 54, 73, 107, 69, 121, 78, 84, 90, 72, 81, 48, 48, 105, 102, 81]

A.1.6. Content Encryption

 Perform authenticated encryption on the plaintext with the AES GCM
 algorithm using the CEK as the encryption key, the JWE Initialization
 Vector, and the Additional Authenticated Data value above, requesting
 a 128-bit Authentication Tag output.  The resulting ciphertext is:
 [229, 236, 166, 241, 53, 191, 115, 196, 174, 43, 73, 109, 39, 122,
 233, 96, 140, 206, 120, 52, 51, 237, 48, 11, 190, 219, 186, 80, 111,
 104, 50, 142, 47, 167, 59, 61, 181, 127, 196, 21, 40, 82, 242, 32,
 123, 143, 168, 226, 73, 216, 176, 144, 138, 247, 106, 60, 16, 205,
 160, 109, 64, 63, 192]
 The resulting Authentication Tag value is:
 [92, 80, 104, 49, 133, 25, 161, 215, 173, 101, 219, 211, 136, 91,
 210, 145]
 Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
 value (with line breaks for display purposes only):
   5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
   SdiwkIr3ajwQzaBtQD_A
 Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
 Tag) gives this value:
   XFBoMYUZodetZdvTiFvSkQ

Jones & Hildebrand Standards Track [Page 35] RFC 7516 JSON Web Encryption (JWE) May 2015

A.1.7. Complete Representation

 Assemble the final representation: The Compact Serialization of this
 result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
 BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
 Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
 Authentication Tag).
 The final result in this example (with line breaks for display
 purposes only) is:
   eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
   OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
   ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
   Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
   mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
   1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
   6UklfCpIMfIjf7iGdXKHzg.
   48V1_ALb6US04U3b.
   5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
   SdiwkIr3ajwQzaBtQD_A.
   XFBoMYUZodetZdvTiFvSkQ

A.1.8. Validation

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

A.2. Example JWE using RSAES-PKCS1-v1_5 and AES_128_CBC_HMAC_SHA_256

 This example encrypts the plaintext "Live long and prosper." to the
 recipient using RSAES-PKCS1-v1_5 for key encryption and
 AES_128_CBC_HMAC_SHA_256 for content encryption.  The representation
 of this plaintext (using JSON array notation) is:
 [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
 112, 114, 111, 115, 112, 101, 114, 46]

Jones & Hildebrand Standards Track [Page 36] RFC 7516 JSON Web Encryption (JWE) May 2015

A.2.1. JOSE Header

 The following example JWE Protected Header declares that:
 o  The Content Encryption Key is encrypted to the recipient using the
    RSAES-PKCS1-v1_5 algorithm to produce the JWE Encrypted Key.
 o  Authenticated encryption is performed on the plaintext using the
    AES_128_CBC_HMAC_SHA_256 algorithm to produce the ciphertext and
    the Authentication Tag.
   {"alg":"RSA1_5","enc":"A128CBC-HS256"}
 Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
 Header)) gives this value:
   eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.2.2. Content Encryption Key (CEK)

 Generate a 256-bit random 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]

Jones & Hildebrand Standards Track [Page 37] RFC 7516 JSON Web Encryption (JWE) May 2015

A.2.3. Key Encryption

 Encrypt the CEK with the recipient's public key using the
 RSAES-PKCS1-v1_5 algorithm to produce the JWE Encrypted Key.  This
 example uses the RSA key represented in JSON Web Key [JWK] format
 below (with line breaks within values for display purposes only):
   {"kty":"RSA",
    "n":"sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl
         UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre
         cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_
         7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI
         Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU
         7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw",
    "e":"AQAB",
    "d":"VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq
         1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry
         nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_
         0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj
         -VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj
         T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ",
    "p":"9gY2w6I6S6L0juEKsbeDAwpd9WMfgqFoeA9vEyEUuk4kLwBKcoe1x4HG68
         ik918hdDSE9vDQSccA3xXHOAFOPJ8R9EeIAbTi1VwBYnbTp87X-xcPWlEP
         krdoUKW60tgs1aNd_Nnc9LEVVPMS390zbFxt8TN_biaBgelNgbC95sM",
    "q":"uKlCKvKv_ZJMVcdIs5vVSU_6cPtYI1ljWytExV_skstvRSNi9r66jdd9-y
         BhVfuG4shsp2j7rGnIio901RBeHo6TPKWVVykPu1iYhQXw1jIABfw-MVsN
         -3bQ76WLdt2SDxsHs7q7zPyUyHXmps7ycZ5c72wGkUwNOjYelmkiNS0",
    "dp":"w0kZbV63cVRvVX6yk3C8cMxo2qCM4Y8nsq1lmMSYhG4EcL6FWbX5h9yuv
         ngs4iLEFk6eALoUS4vIWEwcL4txw9LsWH_zKI-hwoReoP77cOdSL4AVcra
         Hawlkpyd2TWjE5evgbhWtOxnZee3cXJBkAi64Ik6jZxbvk-RR3pEhnCs",
    "dq":"o_8V14SezckO6CNLKs_btPdFiO9_kC1DsuUTd2LAfIIVeMZ7jn1Gus_Ff
         7B7IVx3p5KuBGOVF8L-qifLb6nQnLysgHDh132NDioZkhH7mI7hPG-PYE_
         odApKdnqECHWw0J-F0JWnUd6D2B_1TvF9mXA2Qx-iGYn8OVV1Bsmp6qU",
    "qi":"eNho5yRBEBxhGBtQRww9QirZsB66TrfFReG_CcteI1aCneT0ELGhYlRlC
         tUkTRclIfuEPmNsNDPbLoLqqCVznFbvdB7x-Tl-m0l_eFTj2KiqwGqE9PZ
         B9nNTwMVvH3VRRSLWACvPnSiwP8N5Usy-WRXS-V7TbpxIhvepTfE0NNo"
   }

Jones & Hildebrand Standards Track [Page 38] RFC 7516 JSON Web Encryption (JWE) May 2015

 The resulting JWE Encrypted Key value is:
 [80, 104, 72, 58, 11, 130, 236, 139, 132, 189, 255, 205, 61, 86, 151,
 176, 99, 40, 44, 233, 176, 189, 205, 70, 202, 169, 72, 40, 226, 181,
 156, 223, 120, 156, 115, 232, 150, 209, 145, 133, 104, 112, 237, 156,
 116, 250, 65, 102, 212, 210, 103, 240, 177, 61, 93, 40, 71, 231, 223,
 226, 240, 157, 15, 31, 150, 89, 200, 215, 198, 203, 108, 70, 117, 66,
 212, 238, 193, 205, 23, 161, 169, 218, 243, 203, 128, 214, 127, 253,
 215, 139, 43, 17, 135, 103, 179, 220, 28, 2, 212, 206, 131, 158, 128,
 66, 62, 240, 78, 186, 141, 125, 132, 227, 60, 137, 43, 31, 152, 199,
 54, 72, 34, 212, 115, 11, 152, 101, 70, 42, 219, 233, 142, 66, 151,
 250, 126, 146, 141, 216, 190, 73, 50, 177, 146, 5, 52, 247, 28, 197,
 21, 59, 170, 247, 181, 89, 131, 241, 169, 182, 246, 99, 15, 36, 102,
 166, 182, 172, 197, 136, 230, 120, 60, 58, 219, 243, 149, 94, 222,
 150, 154, 194, 110, 227, 225, 112, 39, 89, 233, 112, 207, 211, 241,
 124, 174, 69, 221, 179, 107, 196, 225, 127, 167, 112, 226, 12, 242,
 16, 24, 28, 120, 182, 244, 213, 244, 153, 194, 162, 69, 160, 244,
 248, 63, 165, 141, 4, 207, 249, 193, 79, 131, 0, 169, 233, 127, 167,
 101, 151, 125, 56, 112, 111, 248, 29, 232, 90, 29, 147, 110, 169,
 146, 114, 165, 204, 71, 136, 41, 252]
 Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
 this value (with line breaks for display purposes only):
   UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm
   1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc
   HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF
   NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8
   rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv
   -B3oWh2TbqmScqXMR4gp_A

A.2.4. Initialization Vector

 Generate a random 128-bit JWE Initialization Vector.  In this
 example, the value is:
 [3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
 101]
 Encoding this JWE Initialization Vector as BASE64URL(JWE
 Initialization Vector) gives this value:
   AxY8DCtDaGlsbGljb3RoZQ

Jones & Hildebrand Standards Track [Page 39] RFC 7516 JSON Web Encryption (JWE) May 2015

A.2.5. Additional Authenticated Data

 Let the Additional Authenticated Data encryption parameter be
 ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:
 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
 120, 88, 122, 85, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105,
 74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85,
 50, 73, 110, 48]

A.2.6. Content Encryption

 Perform authenticated encryption on the plaintext with the
 AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption
 key, the JWE Initialization Vector, and the Additional Authenticated
 Data value above.  The steps for doing this using the values from
 Appendix A.3 are detailed in Appendix B.  The resulting ciphertext
 is:
 [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
 112, 56, 102]
 The resulting Authentication Tag value is:
 [246, 17, 244, 190, 4, 95, 98, 3, 231, 0, 115, 157, 242, 203, 100,
 191]
 Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
 value:
   KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
 Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
 Tag) gives this value:
   9hH0vgRfYgPnAHOd8stkvw

A.2.7. Complete Representation

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

Jones & Hildebrand Standards Track [Page 40] RFC 7516 JSON Web Encryption (JWE) May 2015

 The final result in this example (with line breaks for display
 purposes only) is:
   eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
   UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm
   1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc
   HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF
   NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8
   rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv
   -B3oWh2TbqmScqXMR4gp_A.
   AxY8DCtDaGlsbGljb3RoZQ.
   KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
   9hH0vgRfYgPnAHOd8stkvw

A.2.8. Validation

 This example illustrates the process of creating a JWE with
 RSAES-PKCS1-v1_5 for key encryption and AES_CBC_HMAC_SHA2 for content
 encryption.  These results can be used to validate JWE decryption
 implementations for these algorithms.  Note that since the
 RSAES-PKCS1-v1_5 computation includes random values, the encryption
 results above will not be completely reproducible.  However, since
 the AES-CBC computation is deterministic, the JWE Encrypted
 Ciphertext values will be the same for all encryptions performed
 using these inputs.

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

 This example encrypts the plaintext "Live long and prosper." to the
 recipient using AES Key Wrap for key encryption and
 AES_128_CBC_HMAC_SHA_256 for content encryption.  The representation
 of this plaintext (using JSON array notation) 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. JOSE Header

 The following example JWE Protected 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.
 o  Authenticated encryption is performed on the plaintext using the
    AES_128_CBC_HMAC_SHA_256 algorithm to produce the ciphertext and
    the Authentication Tag.
   {"alg":"A128KW","enc":"A128CBC-HS256"}

Jones & Hildebrand Standards Track [Page 41] RFC 7516 JSON Web Encryption (JWE) May 2015

 Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
 Header)) gives this value:
   eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.3.2. Content Encryption Key (CEK)

 Generate a 256-bit random CEK.  In this example, the value is:
 [4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
 206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
 44, 207]

A.3.3. Key Encryption

 Encrypt the CEK with the shared symmetric key using the AES Key Wrap
 algorithm to produce the JWE Encrypted Key.  This example uses the
 symmetric key represented in JSON Web Key [JWK] format below:
   {"kty":"oct",
    "k":"GawgguFyGrWKav7AX4VKUg"
   }
 The resulting JWE Encrypted Key value is:
 [232, 160, 123, 211, 183, 76, 245, 132, 200, 128, 123, 75, 190, 216,
 22, 67, 201, 138, 193, 186, 9, 91, 122, 31, 246, 90, 28, 139, 57, 3,
 76, 124, 193, 11, 98, 37, 173, 61, 104, 57]
 Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
 this value:
   6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ

A.3.4. Initialization Vector

 Generate a random 128-bit JWE Initialization Vector.  In this
 example, the value is:
 [3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
 101]
 Encoding this JWE Initialization Vector as BASE64URL(JWE
 Initialization Vector) gives this value:
   AxY8DCtDaGlsbGljb3RoZQ

Jones & Hildebrand Standards Track [Page 42] RFC 7516 JSON Web Encryption (JWE) May 2015

A.3.5. Additional Authenticated Data

 Let the Additional Authenticated Data encryption parameter be
 ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:
 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
 83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
 110, 48]

A.3.6. Content Encryption

 Perform authenticated encryption on the plaintext with the
 AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption
 key, the JWE Initialization Vector, and the Additional Authenticated
 Data value above.  The steps for doing this using the values from
 this example are detailed in Appendix B.  The resulting ciphertext
 is:
 [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
 112, 56, 102]
 The resulting Authentication Tag value is:
 [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
 194, 85]
 Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
 value:
   KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
 Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
 Tag) gives this value:
   U0m_YmjN04DJvceFICbCVQ

A.3.7. Complete Representation

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

Jones & Hildebrand Standards Track [Page 43] RFC 7516 JSON Web Encryption (JWE) May 2015

 The final result in this example (with line breaks for display
 purposes only) is:
   eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
   6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.
   AxY8DCtDaGlsbGljb3RoZQ.
   KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
   U0m_YmjN04DJvceFICbCVQ

A.3.8. Validation

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

A.4. Example JWE Using General JWE JSON Serialization

 This section contains an example using the general JWE JSON
 Serialization syntax.  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 CEK, JWE 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).

Jones & Hildebrand Standards Track [Page 44] RFC 7516 JSON Web Encryption (JWE) May 2015

A.4.1. JWE Per-Recipient Unprotected Headers

 The first recipient uses the RSAES-PKCS1-v1_5 algorithm to encrypt
 the CEK.  The second uses AES Key Wrap to encrypt the CEK.  Key ID
 values are supplied for both keys.  The two JWE Per-Recipient
 Unprotected 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

 Authenticated encryption is performed on the plaintext using the
 AES_128_CBC_HMAC_SHA_256 algorithm to produce the common JWE
 Ciphertext and JWE Authentication Tag values.  The JWE Protected
 Header value representing this is:
   {"enc":"A128CBC-HS256"}
 Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
 Header)) gives this value:
   eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.4.3. JWE Shared Unprotected Header

 This JWE uses the "jku" Header Parameter to reference a JWK Set.
 This is represented in the following JWE Shared Unprotected Header
 value as:
   {"jku":"https://server.example.com/keys.jwks"}

A.4.4. Complete JOSE Header Values

 Combining the JWE Per-Recipient Unprotected Header, JWE Protected
 Header, and JWE Shared Unprotected Header values supplied, the JOSE
 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"}

Jones & Hildebrand Standards Track [Page 45] RFC 7516 JSON Web Encryption (JWE) May 2015

 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
 ASCII(BASE64URL(UTF8(JWE Protected Header))).  This value is:
 [101, 121, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73,
 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48]

A.4.6. Content Encryption

 Perform authenticated encryption on the plaintext with the
 AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption
 key, the JWE Initialization Vector, and the Additional Authenticated
 Data value above.  The steps for doing this using the values from
 Appendix A.3 are detailed in Appendix B.  The resulting ciphertext
 is:
 [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
 112, 56, 102]
 The resulting Authentication Tag value is:
 [51, 63, 149, 60, 252, 148, 225, 25, 92, 185, 139, 245, 35, 2, 47,
 207]
 Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
 value:
   KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
 Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
 Tag) gives this value:
   Mz-VPPyU4RlcuYv1IwIvzw

Jones & Hildebrand Standards Track [Page 46] RFC 7516 JSON Web Encryption (JWE) May 2015

A.4.7. Complete JWE JSON Serialization Representation

 The complete JWE JSON Serialization for these values is as follows
 (with line breaks within values for display purposes only):
   {
    "protected":
     "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
    "unprotected":
     {"jku":"https://server.example.com/keys.jwks"},
    "recipients":[
     {"header":
       {"alg":"RSA1_5","kid":"2011-04-29"},
      "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","kid":"7"},
      "encrypted_key":
       "6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"}],
    "iv":
     "AxY8DCtDaGlsbGljb3RoZQ",
    "ciphertext":
     "KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
    "tag":
     "Mz-VPPyU4RlcuYv1IwIvzw"
   }

A.5. Example JWE Using Flattened JWE JSON Serialization

 This section contains an example using the flattened JWE JSON
 Serialization syntax.  This example demonstrates the capability for
 encrypting the plaintext to a single recipient in a flattened JSON
 structure.
 The values in this example are the same as those for the second
 recipient of the previous example in Appendix A.4.

Jones & Hildebrand Standards Track [Page 47] RFC 7516 JSON Web Encryption (JWE) May 2015

 The complete JWE JSON Serialization for these values is as follows
 (with line breaks within values for display purposes only):
   {
    "protected":
     "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
    "unprotected":
     {"jku":"https://server.example.com/keys.jwks"},
    "header":
     {"alg":"A128KW","kid":"7"},
    "encrypted_key":
     "6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ",
    "iv":
     "AxY8DCtDaGlsbGljb3RoZQ",
    "ciphertext":
     "KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
    "tag":
     "Mz-VPPyU4RlcuYv1IwIvzw"
   }

Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation

 This example shows the steps in the AES_128_CBC_HMAC_SHA_256
 authenticated encryption computation using the values from the
 example in Appendix A.3.  As described where this algorithm is
 defined in Sections 5.2 and 5.2.3 of JWA, the AES_CBC_HMAC_SHA2
 family of algorithms are implemented using Advanced Encryption
 Standard (AES) in Cipher Block Chaining (CBC) mode with Public-Key
 Cryptography Standards (PKCS) #7 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
 (using JSON array notation) 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]

Jones & Hildebrand Standards Track [Page 48] RFC 7516 JSON Web Encryption (JWE) May 2015

 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 CBC mode using PKCS #7 padding
 using the ENC_KEY above.  The plaintext in this example is:
 [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
 112, 114, 111, 115, 112, 101, 114, 46]
 The encryption result is as follows, which is the ciphertext output:
 [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
 112, 56, 102]

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

 The Additional Authenticated Data (AAD) in this example is:
 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
 83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
 110, 48]
 This AAD is 51-bytes long, which is 408-bits long.  The octet string
 AL, which is the number of bits in AAD expressed as a big-endian
 64-bit unsigned integer is:
 [0, 0, 0, 0, 0, 0, 1, 152]

B.4. Initialization Vector Value

 The Initialization Vector value used in this example is:
 [3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
 101]

Jones & Hildebrand Standards Track [Page 49] RFC 7516 JSON Web Encryption (JWE) May 2015

B.5. Create Input to HMAC Computation

 Concatenate the AAD, the Initialization Vector, the ciphertext, and
 the AL value.  The result of this concatenation is:
 [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
 83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
 110, 48, 3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111,
 116, 104, 101, 40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24,
 152, 230, 6, 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215,
 104, 143, 112, 56, 102, 0, 0, 0, 0, 0, 0, 1, 152]

B.6. Compute HMAC Value

 Compute the HMAC SHA-256 of the concatenated value above.  This
 result M is:
 [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
 194, 85, 9, 84, 229, 201, 219, 135, 44, 252, 145, 102, 179, 140, 105,
 86, 229, 116]

B.7. Truncate HMAC Value to Create Authentication Tag

 Use the first half (128 bits) of the HMAC output M as the
 Authentication Tag output T.  This truncated value is:
 [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
 194, 85]

Acknowledgements

 Solutions for encrypting JSON content were also explored by "JSON
 Simple Encryption" [JSE] and "JavaScript Message Security Format"
 [JSMS], both of which significantly influenced this document.  This
 document attempts to explicitly reuse as many of the relevant
 concepts from XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411] and
 RFC 5652 [RFC5652] as possible, while utilizing simple, compact JSON-
 based data structures.
 Special thanks are due to John Bradley, Eric Rescorla, and Nat
 Sakimura for the discussions that helped inform the content of this
 specification; to Eric Rescorla and Joe Hildebrand for allowing the
 reuse of text from [JSMS] in this document; and to Eric Rescorla for
 co-authoring many drafts of this specification.
 Thanks to Axel Nennker, Emmanuel Raviart, Brian Campbell, and Edmund
 Jay for validating the examples in this specification.

Jones & Hildebrand Standards Track [Page 50] RFC 7516 JSON Web Encryption (JWE) May 2015

 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, Alissa Cooper, Breno de
 Medeiros, Stephen Farrell, Dick Hardt, Jeff Hodges, Russ Housley,
 Edmund Jay, Scott Kelly, Stephen Kent, Barry Leiba, James Manger,
 Matt Miller, Kathleen Moriarty, Tony Nadalin, Hideki Nara, Axel
 Nennker, Ray Polk, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat
 Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner.
 Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
 Sean Turner, Stephen Farrell, and Kathleen Moriarty served as
 Security Area Directors during the creation of this specification.

Authors' Addresses

 Michael B. Jones
 Microsoft
 EMail: mbj@microsoft.com
 URI:   http://self-issued.info/
 Joe Hildebrand
 Cisco Systems, Inc.
 EMail: jhildebr@cisco.com

Jones & Hildebrand Standards Track [Page 51]

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