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

Abstract

JSON Web Encryption (JWE) is a means of representing encrypted content using JavaScript Object Notation (JSON) based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification. Related digital signature and MAC capabilities are described in the separate JSON Web Signature (JWS) specification.

Status of this Memo

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Copyright Notice

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Table of Contents

1.  Introduction
    1.1.  Notational Conventions
2.  Terminology
3.  JSON Web Encryption (JWE) Overview
    3.1.  Example JWE
4.  JWE Header
    4.1.  Reserved Header Parameter Names
        4.1.1.  "alg" (Algorithm) Header Parameter
        4.1.2.  "enc" (Encryption Method) Header Parameter
        4.1.3.  "epk" (Ephemeral Public Key) Header Parameter
        4.1.4.  "zip" (Compression Algorithm) Header Parameter
        4.1.5.  "jku" (JWK Set URL) Header Parameter
        4.1.6.  "jwk" (JSON Web Key) Header Parameter
        4.1.7.  "x5u" (X.509 URL) Header Parameter
        4.1.8.  "x5t" (X.509 Certificate Thumbprint) Header Parameter
        4.1.9.  "x5c" (X.509 Certificate Chain) Header Parameter
        4.1.10.  "kid" (Key ID) Header Parameter
        4.1.11.  "typ" (Type) Header Parameter
        4.1.12.  "cty" (Content Type) Header Parameter
        4.1.13.  "apu" (Agreement PartyUInfo) Header Parameter
        4.1.14.  "crit" (Critical) Header Parameter
    4.2.  Public Header Parameter Names
    4.3.  Private Header Parameter Names
5.  Producing and Consuming JWEs
    5.1.  Message Encryption
    5.2.  Message Decryption
    5.3.  String Comparison Rules
6.  Cryptographic Algorithms
    6.1.  CEK Encryption
7.  Key Identification
8.  JWE JSON Serialization
9.  Implementation Considerations
10.  IANA Considerations
    10.1.  Registration of JWE Header Parameter Names
        10.1.1.  Registry Contents
    10.2.  JSON Web Signature and Encryption Type Values Registration
        10.2.1.  Registry Contents
    10.3.  Media Type Registration
        10.3.1.  Registry Contents
11.  Security Considerations
12.  References
    12.1.  Normative References
    12.2.  Informative References
Appendix A.  JWE Examples
    A.1.  Example JWE using RSAES OAEP and AES GCM
        A.1.1.  JWE Header
        A.1.2.  Encoded JWE Header
        A.1.3.  Content Encryption Key (CEK)
        A.1.4.  Key Encryption
        A.1.5.  Encoded JWE Encrypted Key
        A.1.6.  Initialization Vector
        A.1.7.  Additional Authenticated Data
        A.1.8.  Plaintext Encryption
        A.1.9.  Encoded JWE Ciphertext
        A.1.10.  Encoded JWE Authentication Tag
        A.1.11.  Complete Representation
        A.1.12.  Validation
    A.2.  Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256
        A.2.1.  JWE Header
        A.2.2.  Encoded JWE Header
        A.2.3.  Content Encryption Key (CEK)
        A.2.4.  Key Encryption
        A.2.5.  Encoded JWE Encrypted Key
        A.2.6.  Initialization Vector
        A.2.7.  Additional Authenticated Data
        A.2.8.  Plaintext Encryption
        A.2.9.  Encoded JWE Ciphertext
        A.2.10.  Encoded JWE Authentication Tag
        A.2.11.  Complete Representation
        A.2.12.  Validation
    A.3.  Example JWE using AES Key Wrap and AES GCM
        A.3.1.  JWE Header
        A.3.2.  Encoded JWE Header
        A.3.3.  Content Encryption Key (CEK)
        A.3.4.  Key Encryption
        A.3.5.  Encoded JWE Encrypted Key
        A.3.6.  Initialization Vector
        A.3.7.  Additional Authenticated Data
        A.3.8.  Plaintext Encryption
        A.3.9.  Encoded JWE Ciphertext
        A.3.10.  Encoded JWE Authentication Tag
        A.3.11.  Complete Representation
        A.3.12.  Validation
    A.4.  Example JWE Using JWE JSON Serialization
        A.4.1.  JWE Per-Recipient Unprotected Headers
        A.4.2.  JWE Protected Header
        A.4.3.  JWE Unprotected Header
        A.4.4.  Complete JWE Header Values
        A.4.5.  Additional Authenticated Data
        A.4.6.  Plaintext Encryption
        A.4.7.  Encoded JWE Ciphertext
        A.4.8.  Encoded JWE Authentication Tag
        A.4.9.  Complete JWE JSON Serialization Representation
Appendix B.  Example AES_128_CBC_HMAC_SHA_256 Computation
    B.1.  Extract MAC_KEY and ENC_KEY from Key
    B.2.  Encrypt Plaintext to Create Ciphertext
    B.3.  64 Bit Big Endian Representation of AAD Length
    B.4.  Initialization Vector Value
    B.5.  Create Input to HMAC Computation
    B.6.  Compute HMAC Value
    B.7.  Truncate HMAC Value to Create Authentication Tag
Appendix C.  Acknowledgements
Appendix D.  Document History
§  Authors' Addresses

1.  Introduction

JSON Web Encryption (JWE) is a means of representing encrypted content using JavaScript Object Notation (JSON) [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) based data structures. The JWE cryptographic mechanisms encrypt and provide integrity protection for arbitrary sequences of octets.

Two closely related representations for JWE objects are defined. The JWE Compact Serialization is a compact, URL-safe representation intended for space constrained environments such as HTTP Authorization headers and URI query parameters. The JWE JSON Serialization represents JWE objects as JSON objects and enables the same content to be encrypted to multiple parties. Both share the same cryptographic underpinnings.

Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) specification. Related digital signature and MAC capabilities are described in the separate JSON Web Signature (JWS) [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) specification.

1.1.  Notational Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in Key words for use in RFCs to Indicate Requirement Levels [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

2.  Terminology

JSON Web Encryption (JWE)

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

Authenticated Encryption

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

Plaintext

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

Ciphertext

An encrypted representation of the Plaintext.

Additional Authenticated Data (AAD)

An input to an Authenticated Encryption operation that is integrity protected but not encrypted.

Authentication Tag

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

Content Encryption Key (CEK)

A symmetric key for the Authenticated Encryption algorithm used to encrypt the Plaintext for the recipient to produce the Ciphertext and the Authentication Tag.

JSON Text Object

A UTF-8 [RFC3629] (Yergeau, F., “UTF-8, a transformation format of ISO 10646,” November 2003.) encoded text string representing a JSON object; the syntax of JSON objects is defined in Section 2.2 of [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.).

JWE Header

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

JWE Encrypted Key

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

JWE Initialization Vector

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

JWE Ciphertext

A sequence of octets containing the Ciphertext for a JWE.

JWE Authentication Tag

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

JWE Protected Header

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

Header Parameter

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

Header Parameter Name

The name of a member of the JWE Header.

Header Parameter Value

The value of a member of the JWE Header.

Base64url Encoding

The URL- and filename-safe Base64 encoding described in RFC 4648 (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” October 2006.) [RFC4648], Section 5, with the (non URL-safe) '=' padding characters omitted, as permitted by Section 3.2. (See Appendix C of [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) for notes on implementing base64url encoding without padding.)

Encoded JWE Header

Base64url encoding of the JWE Protected Header.

Encoded JWE Encrypted Key

Base64url encoding of the JWE Encrypted Key.

Encoded JWE Initialization Vector

Base64url encoding of the JWE Initialization Vector.

Encoded JWE Ciphertext

Base64url encoding of the JWE Ciphertext.

Encoded JWE Authentication Tag

Base64url encoding of the JWE Authentication Tag.

JWE Compact Serialization

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

JWE JSON Serialization

A representation of the JWE as a JSON structure containing JWE Header, Encoded JWE Encrypted Key, Encoded JWE Initialization Vector, Encoded JWE Ciphertext, and Encoded JWE Authentication Tag values. Unlike the JWE Compact Serialization, the JWE JSON Serialization enables the same content to be encrypted to multiple parties. This representation is neither compact nor URL-safe.

Collision Resistant Namespace

A namespace that allows names to be allocated in a manner such that they are highly unlikely to collide with other names. For instance, collision resistance can be achieved through administrative delegation of portions of the namespace or through use of collision-resistant name allocation functions. Examples of Collision Resistant Namespaces include: Domain Names, Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670 Recommendation series, and Universally Unique IDentifiers (UUIDs) [RFC4122] (Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace,” July 2005.). When using an administratively delegated namespace, the definer of a name needs to take reasonable precautions to ensure they are in control of the portion of the namespace they use to define the name.

StringOrURI

A JSON string value, with the additional requirement that while arbitrary string values MAY be used, any value containing a ":" character MUST be a URI [RFC3986] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.). StringOrURI values are compared as case-sensitive strings with no transformations or canonicalizations applied.

Key Management Mode

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

Key Encryption

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

Key Wrapping

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

Direct Key Agreement

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

Key Agreement with Key Wrapping

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

Direct Encryption

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

3.  JSON Web Encryption (JWE) Overview

JWE represents encrypted content using JSON data structures and base64url encoding. Five values are represented in a JWE: the JWE Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, and the JWE Authentication Tag. In the Compact Serialization, the five values are base64url-encoded for transmission, and represented as the concatenation of the encoded strings in that order, with the five strings being separated by four period ('.') characters. A JSON Serialization for this information is also defined in Section 8 (JWE JSON Serialization).

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

3.1.  Example JWE

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

The following example JWE Header declares that:

• the Content Encryption Key is encrypted to the recipient using the RSAES OAEP algorithm to produce the JWE Encrypted Key and
• the Plaintext is encrypted using the AES GCM algorithm with a 256 bit key to produce the Ciphertext.

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

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

  eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

The remaining steps to finish creating this JWE are:

• Generate a random Content Encryption Key (CEK).
• Encrypt the CEK with the recipient's public key using the RSAES OAEP algorithm to produce the JWE Encrypted Key.
• Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key.
• Generate a random JWE Initialization Vector.
• Base64url encode the JWE Initialization Vector to produce the Encoded JWE Initialization Vector.
• Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value.
• Encrypt the Plaintext with AES GCM using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value, requesting a 128 bit Authentication Tag output.
• Base64url encode the Ciphertext to create the Encoded JWE Ciphertext.
• Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag.
• Assemble the final representation: The Compact Serialization of this result is the concatenation of the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag in that order, with the five strings being separated by four period ('.') characters.

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

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

See Appendix A.1 (Example JWE using RSAES OAEP and AES GCM) for the complete details of computing this JWE. See Appendix A (JWE Examples) for additional examples.

4.  JWE Header

The members of the JSON object(s) represented by the JWE Header describe the encryption applied to the Plaintext and optionally additional properties of the JWE. The Header Parameter Names within the JWE Header MUST be unique; JWEs with duplicate Header Parameter Names MUST be rejected.

Implementations are required to understand the specific header parameters defined by this specification that are designated as "MUST be understood" and process them in the manner defined in this specification. All other header parameters defined by this specification that are not so designated MUST be ignored when not understood. Unless listed as a critical header parameter, per Section 4.1.14 ("crit" (Critical) Header Parameter), all other header parameters MUST be ignored when not understood.

There are two ways of distinguishing whether a header is a JWS Header or a JWE Header. The first is by examining the alg (algorithm) header parameter value. If the value represents a digital signature or MAC algorithm, or is the value none, it is for a JWS; if it represents a Key Encryption, Key Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping, or Direct Encryption algorithm, it is for a JWE. A second method is determining whether an enc (encryption method) member exists. If the enc member exists, it is a JWE; otherwise, it is a JWS. Both methods will yield the same result for all legal input values.

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

4.1.  Reserved Header Parameter Names

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

Additional reserved Header Parameter Names can be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.). As indicated by the common registry, JWSs and JWEs share a common header parameter space; when a parameter is used by both specifications, its usage must be compatible between the specifications.

4.1.1.  "alg" (Algorithm) Header Parameter

The alg (algorithm) header parameter identifies the cryptographic algorithm used to encrypt or determine the value of the Content Encryption Key (CEK). The algorithm specified by the alg value MUST be supported by the implementation and there MUST be a key for use with that algorithm associated with the intended recipient or the JWE MUST be rejected. alg values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) or be a value that contains a Collision Resistant Namespace. The alg value is a case sensitive string containing a StringOrURI value. Use of this header parameter is REQUIRED. This header parameter MUST be understood by implementations.

A list of defined alg values can be found in the IANA JSON Web Signature and Encryption Algorithms registry [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.); the initial contents of this registry are the values defined in Section 4.1 of the JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) specification.

4.1.2.  "enc" (Encryption Method) Header Parameter

The enc (encryption method) header parameter identifies the block encryption algorithm used to encrypt the Plaintext to produce the Ciphertext. This algorithm MUST be an Authenticated Encryption algorithm with a specified key length. The algorithm specified by the enc value MUST be supported by the implementation or the JWE MUST be rejected. enc values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) or be a value that contains a Collision Resistant Namespace. The enc value is a case sensitive string containing a StringOrURI value. Use of this header parameter is REQUIRED. This header parameter MUST be understood by implementations.

A list of defined enc values can be found in the IANA JSON Web Signature and Encryption Algorithms registry [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.); the initial contents of this registry are the values defined in Section 4.2 of the JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) specification.

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

The epk (ephemeral public key) value created by the originator for the use in key agreement algorithms. This key is represented as a JSON Web Key [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.) value. When the alg value used identifies an algorithm for which epk is a parameter, this parameter MUST be present if REQUIRED by the algorithm and this header parameter MUST be understood by implementations; otherwise, this parameter MUST be omitted.

4.1.4.  "zip" (Compression Algorithm) Header Parameter

The zip (compression algorithm) applied to the Plaintext before encryption, if any. If present, the value of the zip header parameter MUST be the case sensitive string "DEF". Compression is performed with the DEFLATE [RFC1951] (Deutsch, P., “DEFLATE Compressed Data Format Specification version 1.3,” May 1996.) algorithm. If no zip parameter is present, no compression is applied to the Plaintext before encryption. This header parameter MUST be integrity protected, and therefore MUST occur only with the JWE Protected Header, when used. Use of this header parameter is OPTIONAL. This header parameter MUST be understood by implementations.

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

The jku (JWK Set URL) header parameter is a URI [RFC3986] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) that refers to a resource for a set of JSON-encoded public keys, one of which is the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. The keys MUST be encoded as a JSON Web Key Set (JWK Set) [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.). The protocol used to acquire the resource MUST provide integrity protection; an HTTP GET request to retrieve the certificate MUST use TLS [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.) [RFC5246] (Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.2,” August 2008.); the identity of the server MUST be validated, as per Section 3.1 of HTTP Over TLS [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.). Use of this header parameter is OPTIONAL.

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

The jwk (JSON Web Key) header parameter is the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. This key is represented as a JSON Web Key [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.). Use of this header parameter is OPTIONAL.

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

The x5u (X.509 URL) header parameter is a URI [RFC3986] (Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax,” January 2005.) that refers to a resource for the X.509 public key certificate or certificate chain [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,” May 2008.) containing the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. The identified resource MUST provide a representation of the certificate or certificate chain that conforms to RFC 5280 (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,” May 2008.) [RFC5280] in PEM encoded form [RFC1421] (Linn, J., “Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures,” February 1993.). The certificate containing the public key to which the JWE was encrypted MUST be the first certificate. This MAY be followed by additional certificates, with each subsequent certificate being the one used to certify the previous one. The protocol used to acquire the resource MUST provide integrity protection; an HTTP GET request to retrieve the certificate MUST use TLS [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.) [RFC5246] (Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.2,” August 2008.); the identity of the server MUST be validated, as per Section 3.1 of HTTP Over TLS [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.). Use of this header parameter is OPTIONAL.

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

The x5t (X.509 Certificate Thumbprint) header parameter is a base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER encoding of the X.509 certificate [RFC5280] (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,” May 2008.) containing the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. Use of this header parameter is OPTIONAL.

If, in the future, certificate thumbprints need to be computed using hash functions other than SHA-1, it is suggested that additional related header parameters be defined for that purpose. For example, it is suggested that a new x5t#S256 (X.509 Certificate Thumbprint using SHA-256) header parameter could be defined by registering it in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.).

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

The x5c (X.509 Certificate Chain) header parameter contains the X.509 public key certificate or certificate chain [RFC5280] (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,” May 2008.) containing the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. The certificate or certificate chain is represented as a JSON array of certificate value strings. Each string in the array is a base64 encoded ([RFC4648] (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” October 2006.) Section 4 -- not base64url encoded) DER [ITU.X690.1994] (International Telecommunications Union, “Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER),” 1994.) PKIX certificate value. The certificate containing the public key to which the JWE was encrypted MUST be the first certificate. This MAY be followed by additional certificates, with each subsequent certificate being the one used to certify the previous one. Use of this header parameter is OPTIONAL.

See Appendix B of [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) for an example x5c value.

4.1.10.  "kid" (Key ID) Header Parameter

The kid (key ID) header parameter is a hint indicating which key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. This parameter allows originators to explicitly signal a change of key to recipients. Should the recipient be unable to locate a key corresponding to the kid value, they SHOULD treat that condition as an error. The interpretation of the kid value is unspecified. Its value MUST be a string. Use of this header parameter is OPTIONAL.

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

4.1.11.  "typ" (Type) Header Parameter

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

MIME Media Type [RFC2046] (Freed, N. and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types,” November 1996.) values MAY be used as typ values.

typ values SHOULD either be registered in the IANA JSON Web Signature and Encryption Type Values registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) or be a value that contains a Collision Resistant Namespace.

4.1.12.  "cty" (Content Type) Header Parameter

The cty (content type) header parameter is used to declare the type of the encrypted content (the Plaintext). For example, the JSON Web Token (JWT) [JWT] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Token (JWT),” May 2013.) specification uses the cty value JWT to indicate that the Plaintext is a JSON Web Token (JWT). Content type values that are not understood SHOULD be ignored. The cty value is a case sensitive string. Use of this header parameter is OPTIONAL.

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

4.1.13.  "apu" (Agreement PartyUInfo) Header Parameter

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

4.1.14.  "crit" (Critical) Header Parameter

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

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

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

4.2.  Public Header Parameter Names

Additional Header Parameter Names can be defined by those using JWEs. However, in order to prevent collisions, any new Header Parameter Name SHOULD either be registered in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) or be a Public Name: a value that contains a Collision Resistant Namespace. In each case, the definer of the name or value needs to take reasonable precautions to make sure they are in control of the part of the namespace they use to define the Header Parameter Name.

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

4.3.  Private Header Parameter Names

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

5.  Producing and Consuming JWEs

5.1.  Message Encryption

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

1. Determine the Key Management Mode employed by the algorithm used to determine the Content Encryption Key (CEK) value. (This is the algorithm recorded in the alg (algorithm) header parameter of the resulting JWE.)
2. When Key Wrapping, Key Encryption, or Key Agreement with Key Wrapping are employed, generate a random Content Encryption Key (CEK) value. See RFC 4086 (Eastlake, D., Schiller, J., and S. Crocker, “Randomness Requirements for Security,” June 2005.) [RFC4086] for considerations on generating random values. The CEK MUST have a length equal to that required for the block encryption algorithm.
3. When Direct Key Agreement or Key Agreement with Key Wrapping are employed, use the key agreement algorithm to compute the value of the agreed upon key. When Direct Key Agreement is employed, let the Content Encryption Key (CEK) be the agreed upon key. When Key Agreement with Key Wrapping is employed, the agreed upon key will be used to wrap the CEK.
4. When Key Wrapping, Key Encryption, or Key Agreement with Key Wrapping are employed, encrypt the CEK to the recipient (see Section 6.1 (CEK Encryption)) and let the result be the JWE Encrypted Key.
5. Otherwise, when Direct Key Agreement or Direct Encryption are employed, let the JWE Encrypted Key be the empty octet sequence.
6. When Direct Encryption is employed, let the Content Encryption Key (CEK) be the shared symmetric key.
7. Base64url encode the JWE Encrypted Key to create the Encoded JWE Encrypted Key.
8. If the JWE JSON Serialization is being used, repeat this process for each recipient.
9. Generate a random JWE Initialization Vector of the correct size for the block encryption algorithm (if required for the algorithm); otherwise, let the JWE Initialization Vector be the empty octet sequence.
10. Base64url encode the JWE Initialization Vector to create the Encoded JWE Initialization Vector.
11. Compress the Plaintext if a zip parameter was included.
12. Serialize the (compressed) Plaintext into an octet sequence M.
13. Create a JWE Header containing the encryption parameters used. Note that white space is explicitly allowed in the representation and no canonicalization need be performed before encoding.
14. Base64url encode the octets of the UTF-8 representation of the JWE Protected Header to create the Encoded JWE Header. If the JWE Protected Header is not present (which can only happen when using the JWE JSON Serialization), let the Encoded JWE Header be the empty string.
15. Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value.
16. Encrypt M using the CEK, the JWE Initialization Vector, and the Additional Authenticated Data value using the specified block encryption algorithm to create the JWE Ciphertext value and the JWE Authentication Tag (which is the Authentication Tag output from the encryption operation).
17. Base64url encode the JWE Ciphertext to create the Encoded JWE Ciphertext.
18. Base64url encode the JWE Authentication Tag to create the Encoded JWE Authentication Tag.
19. The five encoded parts are result values used in both the JWE Compact Serialization and the JWE JSON Serialization representations.
20. Create the desired serialized output. The JWE Compact Serialization of this result is the concatenation of the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag in that order, with the five strings being separated by four period ('.') characters. The JWE JSON Serialization is described in Section 8 (JWE JSON Serialization).

5.2.  Message Decryption

The message decryption process is the reverse of the encryption process. The order of the steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. If any of these steps fails, the JWE MUST be rejected.

1. Parse the serialized input to determine the values of the JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag. When using the JWE Compact Serialization, the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag are represented as text strings in that order, separated by four period ('.') characters. The JWE JSON Serialization is described in Section 8 (JWE JSON Serialization).
2. The Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag MUST be successfully base64url decoded following the restriction that no padding characters have been used.
3. The resulting JWE Protected Header MUST be a completely valid JSON object conforming to RFC 4627 (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) [RFC4627].
4. If using the JWE Compact Serialization, let the JWE Header be the JWE Protected Header; otherwise, when using the JWE JSON Serialization, let the JWE Header be the union of the members of the JWE Protected Header, the members of the unprotected value, and the members of the corresponding header value, all of which must be completely valid JSON objects.
5. The resulting JWE Header MUST NOT contain duplicate Header Parameter Names. When using the JWE JSON Serialization, this restriction includes that the same Header Parameter Name also MUST NOT occur in distinct JSON Text Object values that together comprise the JWE Header.
6. The resulting JWE Header MUST be validated to only include parameters and values whose syntax and semantics are both understood and supported or that are specified as being ignored when not understood.
7. Determine the Key Management Mode employed by the algorithm specified by the alg (algorithm) header parameter.
8. Verify that the JWE uses a key known to the recipient.
9. When Direct Key Agreement or Key Agreement with Key Wrapping are employed, use the key agreement algorithm to compute the value of the agreed upon key. When Direct Key Agreement is employed, let the Content Encryption Key (CEK) be the agreed upon key. When Key Agreement with Key Wrapping is employed, the agreed upon key will be used to decrypt the JWE Encrypted Key.
10. When Key Wrapping, Key Encryption, or Key Agreement with Key Wrapping are employed, decrypt the JWE Encrypted Key to produce the Content Encryption Key (CEK). The CEK MUST have a length equal to that required for the block encryption algorithm. Note that when there are multiple recipients, each recipient will only be able decrypt any JWE Encrypted Key values that were encrypted to a key in that recipient's possession. It is therefore normal to only be able to decrypt one of the per-recipient JWE Encrypted Key values to obtain the CEK value. To mitigate against attacks described in RFC 3218 (Rescorla, E., “Preventing the Million Message Attack on Cryptographic Message Syntax,” January 2002.) [RFC3218], the recipient MUST NOT distinguish between format, padding, and length errors of encrypted keys. It is strongly recommended, in the event of receiving an improperly formatted key, that the receiver substitute a randomly generated CEK and proceed to the next step, to mitigate timing attacks.
11. Otherwise, when Direct Key Agreement or Direct Encryption are employed, verify that the JWE Encrypted Key value is empty octet sequence.
12. When Direct Encryption is employed, let the Content Encryption Key (CEK) be the shared symmetric key.
13. If the JWE JSON Serialization is being used, repeat this process for each recipient contained in the representation until the CEK value has been determined.
14. Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value.
15. Decrypt the JWE Ciphertext using the CEK, the JWE Initialization Vector, the Additional Authenticated Data value, and the JWE Authentication Tag (which is the Authentication Tag input to the calculation) using the specified block encryption algorithm, returning the decrypted plaintext and verifying the JWE Authentication Tag in the manner specified for the algorithm, rejecting the input without emitting any decrypted output if the JWE Authentication Tag is incorrect.
16. Uncompress the decrypted plaintext if a zip parameter was included.
17. Output the resulting Plaintext.

5.3.  String Comparison Rules

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

Comparisons between JSON strings and other Unicode strings MUST be performed by comparing Unicode code points without normalization as specified in the String Comparison Rules in Section 5.3 of [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.).

6.  Cryptographic Algorithms

JWE uses cryptographic algorithms to encrypt the Plaintext and the Content Encryption Key (CEK) and to provide integrity protection for the JWE Protected Header and JWE Ciphertext. The JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) specification specifies a set of cryptographic algorithms and identifiers to be used with this specification and defines registries for additional such algorithms. Specifically, Section 4.1 specifies a set of alg (algorithm) header parameter values and Section 4.2 specifies a set of enc (encryption method) header parameter values intended for use this specification. It also describes the semantics and operations that are specific to these algorithms.

6.1.  CEK Encryption

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

• Asymmetric encryption under the recipient's public key.
• Symmetric encryption under a key shared between the sender and receiver.
• Symmetric encryption under a key agreed upon between the sender and receiver.

See the algorithms registered for enc usage in the IANA JSON Web Signature and Encryption Algorithms registry [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) and Section 4.1 of the JSON Web Algorithms (JWA) [JWA] (Jones, M., “JSON Web Algorithms (JWA),” May 2013.) specification for lists of encryption algorithms that can be used for CEK encryption.

7.  Key Identification

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

8.  JWE JSON Serialization

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

The representation is closely related to that used in the JWE Compact Serialization, with the following differences for the JWE JSON Serialization:

• Values in the JWE JSON Serialization are represented as members of a JSON object, rather than as base64url encoded strings separated by period ('.') characters. (However binary values and values that are integrity protected are still base64url encoded.)
• The Encoded JWE Header value, if non-empty, is stored in the protected member.
• The Encoded JWE Initialization Vector value is stored in the iv member.
• The Encoded JWE Ciphertext value is stored in the ciphertext member.
• The Encoded JWE Authentication Tag value is stored in the tag member.
• The JWE can be encrypted to multiple recipients, rather than just one. A JSON array in the recipients member is used to hold values that are specific to a particular recipient, with one array element per recipient represented. These array elements are JSON objects.
• Each Encoded JWE Encrypted Key value is stored in the encrypted_key member of a JSON object that is an element of the recipients array.
• Some header parameter values, such as the alg value and parameters used for selecting keys, can also differ for different recipient computations. Per-recipient header parameter values are stored in the header members of the same JSON objects that are elements of the recipients array.
• Some header parameters, including the alg parameter, can be shared among all recipient computations. These header parameters are stored in either of two top-level member(s) of the JSON object: the protected member and the unprotected member. The values of these members are JSON Text Objects containing Header Parameters.
• Not all header parameters are integrity protected. The shared header parameters in the protected member are integrity protected, and are base64url encoded. The per-recipient header parameters in the header array element members and the shared header parameters in the unprotected member are not integrity protected. These JSON Text Objects containing header parameters that are not integrity protected are not base64url encoded.
• The header parameter values used when creating or validating per-recipient Ciphertext and Authentication Tag values are the union of the three sets of header parameter values that may be present: (1) the per-recipient values in the header member of the recipient's array element, (2) the shared integrity-protected values in the protected member, and (3) the shared non-integrity-protected values in the unprotected member. The union of these sets of header parameters comprises the JWE Header. The header parameter names in the three locations MUST be disjoint.

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

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

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

The contents of the Encoded JWE Encrypted Key, Encoded JWE Initialization Vector, Encoded JWE Ciphertext, and Encoded JWE Authentication Tag values are exactly as defined in the rest of this specification. They are interpreted and validated in the same manner, with each corresponding Encoded JWE Encrypted Key, Encoded JWE Initialization Vector, Encoded JWE Ciphertext, Encoded JWE Authentication Tag, and set of header parameter values being created and validated together. The JWE Header values used are the union of the header parameters in the protected, unprotected, and corresponding header members, as described earlier.

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

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

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

9.  Implementation Considerations

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

10.  IANA Considerations

10.1.  Registration of JWE Header Parameter Names

This specification registers the Header Parameter Names defined in Section 4.1 (Reserved Header Parameter Names) in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.).

10.1.1.  Registry Contents

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

• Header Parameter Name: enc
• Header Parameter Usage Location(s): JWE
• Change Controller: IETF
• Specification Document(s): Section 4.1.2 ("enc" (Encryption Method) Header Parameter) of [[ this document ]]

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

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

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

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

• Header Parameter Name: x5u
• Header Parameter Usage Location(s): JWE
• Change Controller: IETF
• Specification Document(s): Section 4.1.7 ("x5u" (X.509 URL) Header Parameter) of [[ this document ]]

• Header Parameter Name: x5t
• Header Parameter Usage Location(s): JWE
• Change Controller: IETF
• Specification Document(s): Section 4.1.8 ("x5t" (X.509 Certificate Thumbprint) Header Parameter) of [[ this document ]]

• Header Parameter Name: x5c
• Header Parameter Usage Location(s): JWE
• Change Controller: IETF
• Specification Document(s): Section 4.1.9 ("x5c" (X.509 Certificate Chain) Header Parameter) of [[ this document ]]

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

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

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

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

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

10.2.  JSON Web Signature and Encryption Type Values Registration

10.2.1.  Registry Contents

This specification registers the JWE and JWE+JSON type values in the IANA JSON Web Signature and Encryption Type Values registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.):

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

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

10.3.  Media Type Registration

10.3.1.  Registry Contents

This specification registers the application/jwe and application/jwe+json Media Types [RFC2046] (Freed, N. and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types,” November 1996.) in the MIME Media Type registry [RFC4288] (Freed, N. and J. Klensin, “Media Type Specifications and Registration Procedures,” December 2005.) to indicate, respectively, that the content is a JWE using the JWE Compact Serialization or a JWE using the JWE JSON Serialization.

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

• Type Name: application
• Subtype Name: jwe+json
• Required Parameters: n/a
• Optional Parameters: n/a
• Encoding considerations: application/jwe+json values are represented as a JSON Object; UTF-8 encoding SHOULD be employed for the JSON object.
• Security Considerations: See the Security Considerations section of [[ this document ]]
• Interoperability Considerations: n/a
• Published Specification: [[ this document ]]
• Applications that use this media type: TBD
• Additional Information: Magic number(s): n/a, File extension(s): n/a, Macintosh file type code(s): n/a
• Person & email address to contact for further information: Michael B. Jones, mbj@microsoft.com
• Intended Usage: COMMON
• Restrictions on Usage: none
• Author: Michael B. Jones, mbj@microsoft.com
• Change Controller: IETF

11.  Security Considerations

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

All the security considerations in the JWS specification also apply to this specification. Likewise, all the security considerations in XML Encryption 1.1 (Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, “XML Encryption Syntax and Processing Version 1.1,” March 2012.) [W3C.CR‑xmlenc‑core1‑20120313] also apply, other than those that are XML specific.

When decrypting, particular care must be taken not to allow the JWE recipient to be used as an oracle for decrypting messages. RFC 3218 (Rescorla, E., “Preventing the Million Message Attack on Cryptographic Message Syntax,” January 2002.) [RFC3218] should be consulted for specific countermeasures to attacks on RSAES-PKCS1-V1_5. An attacker might modify the contents of the alg parameter from RSA-OAEP to RSA1_5 in order to generate a formatting error that can be detected and used to recover the CEK even if RSAES OAEP was used to encrypt the CEK. It is therefore particularly important to report all formatting errors to the CEK, Additional Authenticated Data, or ciphertext as a single error when the JWE is rejected.

12.  References

12.1. Normative References

12.2. Informative References

Appendix A.  JWE Examples

This section provides examples of JWE computations.

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

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

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

A.1.1.  JWE Header

The following example JWE Header declares that:

• the Content Encryption Key is encrypted to the recipient using the RSAES OAEP algorithm to produce the JWE Encrypted Key and
• the Plaintext is encrypted using the AES GCM algorithm with a 256 bit key to produce the Ciphertext.

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

A.1.2.  Encoded JWE Header

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

  eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ

A.1.3.  Content Encryption Key (CEK)

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

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

A.1.4.  Key Encryption

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

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]

A.1.5.  Encoded JWE Encrypted Key

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

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

A.1.6.  Initialization Vector

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

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

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

  48V1_ALb6US04U3b

A.1.7.  Additional Authenticated Data

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

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

A.1.8.  Plaintext Encryption

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

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

The resulting Authentication Tag value is:

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

A.1.9.  Encoded JWE Ciphertext

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

  5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
  SdiwkIr3ajwQzaBtQD_A

A.1.10.  Encoded JWE Authentication Tag

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

  XFBoMYUZodetZdvTiFvSkQ

A.1.11.  Complete Representation

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

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

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

A.1.12.  Validation

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

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

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

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

A.2.1.  JWE Header

The following example JWE Header (with line breaks for display purposes only) declares that:

• the Content Encryption Key is encrypted to the recipient using the RSAES-PKCS1-V1_5 algorithm to produce the JWE Encrypted Key and
• the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the Ciphertext.

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

A.2.2.  Encoded JWE Header

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

  eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.2.3.  Content Encryption Key (CEK)

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

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

A.2.4.  Key Encryption

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

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]

A.2.5.  Encoded JWE Encrypted Key

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

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

A.2.6.  Initialization Vector

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

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

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

  AxY8DCtDaGlsbGljb3RoZQ

A.2.7.  Additional Authenticated Data

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

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

A.2.8.  Plaintext Encryption

Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above. The steps for doing this using the values from Appendix A.3 (Example JWE using AES Key Wrap and AES GCM) are detailed in Appendix B (Example AES_128_CBC_HMAC_SHA_256 Computation). 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]

A.2.9.  Encoded JWE Ciphertext

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

  KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

A.2.10.  Encoded JWE Authentication Tag

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

  9hH0vgRfYgPnAHOd8stkvw

A.2.11.  Complete Representation

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

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

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

A.2.12.  Validation

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

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

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

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

A.3.1.  JWE Header

The following example JWE Header declares that:

• the Content Encryption Key is encrypted to the recipient using the AES Key Wrap algorithm with a 128 bit key to produce the JWE Encrypted Key and
• the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the Ciphertext.

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

A.3.2.  Encoded JWE Header

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

  eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.3.3.  Content Encryption Key (CEK)

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

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

A.3.4.  Key Encryption

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

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

The resulting JWE Encrypted Key value is:

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

A.3.5.  Encoded JWE Encrypted Key

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

  6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ

A.3.6.  Initialization Vector

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

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

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

  AxY8DCtDaGlsbGljb3RoZQ

A.3.7.  Additional Authenticated Data

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

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

A.3.8.  Plaintext Encryption

Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above. The steps for doing this using the values from this example are detailed in Appendix B (Example AES_128_CBC_HMAC_SHA_256 Computation). 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]

A.3.9.  Encoded JWE Ciphertext

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

  KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

A.3.10.  Encoded JWE Authentication Tag

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

  U0m_YmjN04DJvceFICbCVQ

A.3.11.  Complete Representation

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

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

  eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
  6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.
  AxY8DCtDaGlsbGljb3RoZQ.
  KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
  U0m_YmjN04DJvceFICbCVQ

A.3.12.  Validation

This example illustrates the process of creating a JWE with symmetric key wrap and AES_CBC_HMAC_SHA2. These results can be used to validate JWE decryption implementations for these algorithms. Also, since both the AES Key Wrap and AES GCM computations are deterministic, the resulting JWE value will be the same for all encryptions performed using these inputs. Since the computation is reproducible, these results can also be used to validate JWE encryption implementations for these algorithms.

A.4.  Example JWE Using JWE JSON Serialization

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

Two recipients are present in this example. The algorithm and key used for the first recipient are the same as that used in Appendix A.2 (Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256). The algorithm and key used for the second recipient are the same as that used in Appendix A.3 (Example JWE using AES Key Wrap and AES GCM). The resulting JWE Encrypted Key values are therefore the same; those computations are not repeated here.

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

A.4.1.  JWE Per-Recipient Unprotected Headers

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

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

and:

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

A.4.2.  JWE Protected Header

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

  {"enc":"A128CBC-HS256"}

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

  eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0

A.4.3.  JWE Unprotected Header

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

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

A.4.4.  Complete JWE Header Values

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

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

and:

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

A.4.5.  Additional Authenticated Data

Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Protected Header value. This AAD value is:

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

A.4.6.  Plaintext Encryption

Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above. The steps for doing this using the values from Appendix A.3 (Example JWE using AES Key Wrap and AES GCM) are detailed in Appendix B (Example AES_128_CBC_HMAC_SHA_256 Computation). 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]

A.4.7.  Encoded JWE Ciphertext

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

  KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY

A.4.8.  Encoded JWE Authentication Tag

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

  Mz-VPPyU4RlcuYv1IwIvzw

A.4.9.  Complete JWE JSON Serialization Representation

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

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

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 (Example JWE using AES Key Wrap and AES GCM). As described where this algorithm is defined in Sections 4.8 and 4.8.3 of JWA, the AES_CBC_HMAC_SHA2 family of algorithms are implemented using Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding to perform the encryption and an HMAC SHA-2 function to perform the integrity calculation - in this case, HMAC SHA-256.

B.1.  Extract MAC_KEY and ENC_KEY from Key

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

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

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

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

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

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

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

B.2.  Encrypt Plaintext to Create Ciphertext

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

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

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

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

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

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

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

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

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

B.4.  Initialization Vector Value

The Initialization Vector value used in this example is:

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

B.5.  Create Input to HMAC Computation

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

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

B.6.  Compute HMAC Value

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

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

B.7.  Truncate HMAC Value to Create Authentication Tag

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

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

Appendix C.  Acknowledgements

Solutions for encrypting JSON content were also explored by JSON Simple Encryption (Bradley, J. and N. Sakimura (editor), “JSON Simple Encryption,” September 2010.) [JSE] and JavaScript Message Security Format (Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format,” March 2011.) [I‑D.rescorla‑jsms], both of which significantly influenced this draft. This draft attempts to explicitly reuse as many of the relevant concepts from XML Encryption 1.1 (Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, “XML Encryption Syntax and Processing Version 1.1,” March 2012.) [W3C.CR‑xmlenc‑core1‑20120313] and RFC 5652 (Housley, R., “Cryptographic Message Syntax (CMS),” September 2009.) [RFC5652] as possible, while utilizing simple compact JSON-based data structures.

Special thanks are due to John Bradley and Nat Sakimura for the discussions that helped inform the content of this specification and to Eric Rescorla and Joe Hildebrand for allowing the reuse of text from [I‑D.rescorla‑jsms] (Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format,” March 2011.) in this document.

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

This specification is the work of the JOSE Working Group, which includes dozens of active and dedicated participants. In particular, the following individuals contributed ideas, feedback, and wording that influenced this specification:

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

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

Appendix D.  Document History

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

-11

• Added Key Identification section.
• Removed the Encrypted Key value from the AAD computation since it is already effectively integrity protected by the encryption process. The AAD value now only contains the representation of the JWE Encrypted Header.
• For the JWE JSON Serialization, enable header parameter values to be specified in any of three parameters: the protected member that is integrity protected and shared among all recipients, the unprotected member that is not integrity protected and shared among all recipients, and the header member that is not integrity protected and specific to a particular recipient. (This does not affect the JWE Compact Serialization, in which all header parameter values are in a single integrity protected JWE Header value.)
• Shortened the names authentication_tag to tag and initialization_vector to iv in the JWE JSON Serialization, addressing issue #20.
• Removed apv (agreement PartyVInfo) since it is no longer used.
• Removed suggested compact serialization for multiple recipients.
• Changed the MIME type name application/jwe-js to application/jwe+json, addressing issue #22.
• Tightened the description of the crit (critical) header parameter.

-10

• Changed the JWE processing rules for multiple recipients so that a single AAD value contains the header parameters and encrypted key values for all the recipients, enabling AES GCM to be safely used for multiple recipients.
• Added an appendix suggesting a possible compact serialization for JWEs with multiple recipients.

-09

• Added JWE JSON Serialization, as specified by draft-jones-jose-jwe-json-serialization-04.
• Registered application/jwe-js MIME type and JWE-JS typ header parameter value.
• Defined that the default action for header parameters that are not understood is to ignore them unless specifically designated as "MUST be understood" or included in the new crit (critical) header parameter list. This addressed issue #6.
• Corrected x5c description. This addressed issue #12.
• Changed from using the term "byte" to "octet" when referring to 8 bit values.
• Added Key Management Mode definitions to terminology section and used the defined terms to provide clearer key management instructions. This addressed issue #5.
• Added text about preventing the recipient from behaving as an oracle during decryption, especially when using RSAES-PKCS1-V1_5.
• Changed from using the term "Integrity Value" to "Authentication Tag".
• Changed member name from integrity_value to authentication_tag in the JWE JSON Serialization.
• Removed Initialization Vector from the AAD value since it is already integrity protected by all of the authenticated encryption algorithms specified in the JWA specification.
• Replaced A128CBC+HS256 and A256CBC+HS512 with A128CBC-HS256 and A256CBC-HS512. The new algorithms perform the same cryptographic computations as [I‑D.mcgrew‑aead‑aes‑cbc‑hmac‑sha2] (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.), but with the Initialization Vector and Authentication Tag values remaining separate from the Ciphertext value in the output representation. Also deleted the header parameters epu (encryption PartyUInfo) and epv (encryption PartyVInfo), since they are no longer used.

-08

• Replaced uses of the term "AEAD" with "Authenticated Encryption", since the term AEAD in the RFC 5116 sense implied the use of a particular data representation, rather than just referring to the class of algorithms that perform authenticated encryption with associated data.
• Applied editorial improvements suggested by Jeff Hodges and Hannes Tschofenig. Many of these simplified the terminology used.
• Clarified statements of the form "This header parameter is OPTIONAL" to "Use of this header parameter is OPTIONAL".
• Added a Header Parameter Usage Location(s) field to the IANA JSON Web Signature and Encryption Header Parameters registry.
• Added seriesInfo information to Internet Draft references.

-07

• Added a data length prefix to PartyUInfo and PartyVInfo values.
• Updated values for example AES CBC calculations.
• Made several local editorial changes to clean up loose ends left over from to the decision to only support block encryption methods providing integrity. One of these changes was to explicitly state that the enc (encryption method) algorithm must be an Authenticated Encryption algorithm with a specified key length.

-06

• Removed the int and kdf parameters and defined the new composite Authenticated Encryption algorithms A128CBC+HS256 and A256CBC+HS512 to replace the former uses of AES CBC, which required the use of separate integrity and key derivation functions.
• Included additional values in the Concat KDF calculation -- the desired output size and the algorithm value, and optionally PartyUInfo and PartyVInfo values. Added the optional header parameters apu (agreement PartyUInfo), apv (agreement PartyVInfo), epu (encryption PartyUInfo), and epv (encryption PartyVInfo). Updated the KDF examples accordingly.
• Promoted Initialization Vector from being a header parameter to being a top-level JWE element. This saves approximately 16 bytes in the compact serialization, which is a significant savings for some use cases. Promoting the Initialization Vector out of the header also avoids repeating this shared value in the JSON serialization.
• Changed x5c (X.509 Certificate Chain) representation from being a single string to being an array of strings, each containing a single base64 encoded DER certificate value, representing elements of the certificate chain.
• Added an AES Key Wrap example.
• Reordered the encryption steps so CMK creation is first, when required.
• Correct statements in examples about which algorithms produce reproducible results.

-05

• Support both direct encryption using a shared or agreed upon symmetric key, and the use of a shared or agreed upon symmetric key to key wrap the CMK.
• Added statement that "StringOrURI values are compared as case-sensitive strings with no transformations or canonicalizations applied".
• Updated open issues.
• Indented artwork elements to better distinguish them from the body text.

-04

• Refer to the registries as the primary sources of defined values and then secondarily reference the sections defining the initial contents of the registries.
• Normatively reference XML Encryption 1.1 (Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, “XML Encryption Syntax and Processing Version 1.1,” March 2012.) [W3C.CR‑xmlenc‑core1‑20120313] for its security considerations.
• Reference draft-jones-jose-jwe-json-serialization instead of draft-jones-json-web-encryption-json-serialization.
• Described additional open issues.
• Applied editorial suggestions.

-03

• Added the kdf (key derivation function) header parameter to provide crypto agility for key derivation. The default KDF remains the Concat KDF with the SHA-256 digest function.
• Reordered encryption steps so that the Encoded JWE Header is always created before it is needed as an input to the Authenticated Encryption "additional authenticated data" parameter.
• Added the cty (content type) header parameter for declaring type information about the secured content, as opposed to the typ (type) header parameter, which declares type information about this object.
• Moved description of how to determine whether a header is for a JWS or a JWE from the JWT spec to the JWE spec.
• Added complete encryption examples for both Authenticated Encryption and non-Authenticated Encryption algorithms.
• Added complete key derivation examples.
• Added "Collision Resistant Namespace" to the terminology section.
• Reference ITU.X690.1994 for DER encoding.
• Added Registry Contents sections to populate registry values.
• Numerous editorial improvements.

-02

• When using Authenticated Encryption algorithms (such as AES GCM), use the "additional authenticated data" parameter to provide integrity for the header, encrypted key, and ciphertext and use the resulting "authentication tag" value as the JWE Authentication Tag.
• Defined KDF output key sizes.
• Generalized text to allow key agreement to be employed as an alternative to key wrapping or key encryption.
• Changed compression algorithm from gzip to DEFLATE.
• Clarified that it is an error when a kid value is included and no matching key is found.
• Clarified that JWEs with duplicate Header Parameter Names MUST be rejected.
• Clarified the relationship between typ header parameter values and MIME types.
• Registered application/jwe MIME type and "JWE" typ header parameter value.
• Simplified JWK terminology to get replace the "JWK Key Object" and "JWK Container Object" terms with simply "JSON Web Key (JWK)" and "JSON Web Key Set (JWK Set)" and to eliminate potential confusion between single keys and sets of keys. As part of this change, the Header Parameter Name for a public key value was changed from jpk (JSON Public Key) to jwk (JSON Web Key).
• Added suggestion on defining additional header parameters such as x5t#S256 in the future for certificate thumbprints using hash algorithms other than SHA-1.
• Specify RFC 2818 server identity validation, rather than RFC 6125 (paralleling the same decision in the OAuth specs).
• Generalized language to refer to Message Authentication Codes (MACs) rather than Hash-based Message Authentication Codes (HMACs) unless in a context specific to HMAC algorithms.
• Reformatted to give each header parameter its own section heading.

-01

• Added an integrity check for non-Authenticated Encryption algorithms.
• Added jpk and x5c header parameters for including JWK public keys and X.509 certificate chains directly in the header.
• Clarified that this specification is defining the JWE Compact Serialization. Referenced the new JWE-JS spec, which defines the JWE JSON Serialization.
• Added text "New header parameters should be introduced sparingly since an implementation that does not understand a parameter MUST reject the JWE".
• Clarified that the order of the encryption and decryption steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps.
• Made other editorial improvements suggested by JOSE working group participants.

-00

• Created the initial IETF draft based upon draft-jones-json-web-encryption-02 with no normative changes.
• Changed terminology to no longer call both digital signatures and HMACs "signatures".

Authors' Addresses