JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track E. Rescorla
Expires: March 7, 2014 RTFM
J. Hildebrand
Cisco
September 3, 2013
JSON Web Encryption (JWE)
draft-ietf-jose-json-web-encryption-15
Abstract
JSON Web Encryption (JWE) represents encrypted content using
JavaScript Object Notation (JSON) based data structures.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate JSON Web Algorithms (JWA)
specification and IANA registries defined by that specification.
Related digital signature and MAC capabilities are described in the
separate JSON Web Signature (JWS) specification.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 7, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Jones, et al. Expires March 7, 2014 [Page 1]
Internet-Draft JWE September 2013
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. JSON Web Encryption (JWE) Overview . . . . . . . . . . . . . . 8
3.1. Example JWE . . . . . . . . . . . . . . . . . . . . . . . 9
4. JWE Header . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Reserved Header Parameter Names . . . . . . . . . . . . . 11
4.1.1. "alg" (Algorithm) Header Parameter . . . . . . . . . . 11
4.1.2. "enc" (Encryption Method) Header Parameter . . . . . . 11
4.1.3. "zip" (Compression Algorithm) Header Parameter . . . . 12
4.1.4. "jku" (JWK Set URL) Header Parameter . . . . . . . . . 12
4.1.5. "jwk" (JSON Web Key) Header Parameter . . . . . . . . 12
4.1.6. "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 12
4.1.7. "x5t" (X.509 Certificate Thumbprint) Header
Parameter . . . . . . . . . . . . . . . . . . . . . . 13
4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter . . . 13
4.1.9. "kid" (Key ID) Header Parameter . . . . . . . . . . . 14
4.1.10. "typ" (Type) Header Parameter . . . . . . . . . . . . 14
4.1.11. "cty" (Content Type) Header Parameter . . . . . . . . 14
4.1.12. "crit" (Critical) Header Parameter . . . . . . . . . . 15
4.2. Public Header Parameter Names . . . . . . . . . . . . . . 15
4.3. Private Header Parameter Names . . . . . . . . . . . . . . 15
5. Producing and Consuming JWEs . . . . . . . . . . . . . . . . . 16
5.1. Message Encryption . . . . . . . . . . . . . . . . . . . . 16
5.2. Message Decryption . . . . . . . . . . . . . . . . . . . . 18
5.3. String Comparison Rules . . . . . . . . . . . . . . . . . 20
6. Key Identification . . . . . . . . . . . . . . . . . . . . . . 20
7. Serializations . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1. JWE Compact Serialization . . . . . . . . . . . . . . . . 21
7.2. JWE JSON Serialization . . . . . . . . . . . . . . . . . . 21
8. Distinguishing Between JWS and JWE Objects . . . . . . . . . . 24
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
9.1. Registration of JWE Header Parameter Names . . . . . . . . 25
9.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 25
10. Security Considerations . . . . . . . . . . . . . . . . . . . 26
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
11.1. Normative References . . . . . . . . . . . . . . . . . . . 27
11.2. Informative References . . . . . . . . . . . . . . . . . . 28
Appendix A. JWE Examples . . . . . . . . . . . . . . . . . . . . 29
Jones, et al. Expires March 7, 2014 [Page 2]
Internet-Draft JWE September 2013
A.1. Example JWE using RSAES OAEP and AES GCM . . . . . . . . . 29
A.1.1. JWE Header . . . . . . . . . . . . . . . . . . . . . . 29
A.1.2. Encoded JWE Header . . . . . . . . . . . . . . . . . . 29
A.1.3. Content Encryption Key (CEK) . . . . . . . . . . . . . 30
A.1.4. Key Encryption . . . . . . . . . . . . . . . . . . . . 30
A.1.5. Encoded JWE Encrypted Key . . . . . . . . . . . . . . 31
A.1.6. Initialization Vector . . . . . . . . . . . . . . . . 31
A.1.7. Additional Authenticated Data . . . . . . . . . . . . 31
A.1.8. Plaintext Encryption . . . . . . . . . . . . . . . . . 31
A.1.9. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 32
A.1.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 32
A.1.11. Complete Representation . . . . . . . . . . . . . . . 32
A.1.12. Validation . . . . . . . . . . . . . . . . . . . . . . 33
A.2. Example JWE using RSAES-PKCS1-V1_5 and
AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 33
A.2.1. JWE Header . . . . . . . . . . . . . . . . . . . . . . 33
A.2.2. Encoded JWE Header . . . . . . . . . . . . . . . . . . 33
A.2.3. Content Encryption Key (CEK) . . . . . . . . . . . . . 33
A.2.4. Key Encryption . . . . . . . . . . . . . . . . . . . . 34
A.2.5. Encoded JWE Encrypted Key . . . . . . . . . . . . . . 35
A.2.6. Initialization Vector . . . . . . . . . . . . . . . . 35
A.2.7. Additional Authenticated Data . . . . . . . . . . . . 35
A.2.8. Plaintext Encryption . . . . . . . . . . . . . . . . . 35
A.2.9. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 36
A.2.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 36
A.2.11. Complete Representation . . . . . . . . . . . . . . . 36
A.2.12. Validation . . . . . . . . . . . . . . . . . . . . . . 36
A.3. Example JWE using AES Key Wrap and
AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 37
A.3.1. JWE Header . . . . . . . . . . . . . . . . . . . . . . 37
A.3.2. Encoded JWE Header . . . . . . . . . . . . . . . . . . 37
A.3.3. Content Encryption Key (CEK) . . . . . . . . . . . . . 37
A.3.4. Key Encryption . . . . . . . . . . . . . . . . . . . . 37
A.3.5. Encoded JWE Encrypted Key . . . . . . . . . . . . . . 38
A.3.6. Initialization Vector . . . . . . . . . . . . . . . . 38
A.3.7. Additional Authenticated Data . . . . . . . . . . . . 38
A.3.8. Plaintext Encryption . . . . . . . . . . . . . . . . . 38
A.3.9. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 39
A.3.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 39
A.3.11. Complete Representation . . . . . . . . . . . . . . . 39
A.3.12. Validation . . . . . . . . . . . . . . . . . . . . . . 40
A.4. Example JWE Using JWE JSON Serialization . . . . . . . . . 40
A.4.1. JWE Per-Recipient Unprotected Headers . . . . . . . . 40
A.4.2. JWE Protected Header . . . . . . . . . . . . . . . . . 40
A.4.3. JWE Unprotected Header . . . . . . . . . . . . . . . . 41
A.4.4. Complete JWE Header Values . . . . . . . . . . . . . . 41
A.4.5. Additional Authenticated Data . . . . . . . . . . . . 41
A.4.6. Plaintext Encryption . . . . . . . . . . . . . . . . . 41
Jones, et al. Expires March 7, 2014 [Page 3]
Internet-Draft JWE September 2013
A.4.7. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 42
A.4.8. Encoded JWE Authentication Tag . . . . . . . . . . . . 42
A.4.9. Complete JWE JSON Serialization Representation . . . . 42
Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation . . . . 43
B.1. Extract MAC_KEY and ENC_KEY from Key . . . . . . . . . . . 43
B.2. Encrypt Plaintext to Create Ciphertext . . . . . . . . . . 44
B.3. 64 Bit Big Endian Representation of AAD Length . . . . . . 44
B.4. Initialization Vector Value . . . . . . . . . . . . . . . 44
B.5. Create Input to HMAC Computation . . . . . . . . . . . . . 45
B.6. Compute HMAC Value . . . . . . . . . . . . . . . . . . . . 45
B.7. Truncate HMAC Value to Create Authentication Tag . . . . . 45
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 45
Appendix D. Document History . . . . . . . . . . . . . . . . . . 46
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 53
Jones, et al. Expires March 7, 2014 [Page 4]
Internet-Draft JWE September 2013
1. Introduction
JSON Web Encryption (JWE) represents encrypted content using
JavaScript Object Notation (JSON) [RFC4627] based data structures.
The JWE cryptographic mechanisms encrypt and provide integrity
protection for an arbitrary sequence of octets.
Two closely related serializations for JWE objects are defined. The
JWE Compact Serialization is a compact, URL-safe representation
intended for space constrained environments such as HTTP
Authorization headers and URI query parameters. The JWE JSON
Serialization represents JWE objects as JSON objects and enables the
same content to be encrypted to multiple parties. Both share the
same cryptographic underpinnings.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate JSON Web Algorithms (JWA)
[JWA] specification and IANA registries defined by that
specification. Related digital signature and MAC capabilities are
described in the separate JSON Web Signature (JWS) [JWS]
specification.
Names defined by this specification are short because a core goal is
for the resulting representations to be compact.
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in Key words for use in
RFCs to Indicate Requirement Levels [RFC2119].
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 with Associated Data (AEAD) An AEAD
algorithm is one that encrypts the Plaintext, allows Additional
Authenticated Data to be specified, and provides an integrated
content integrity check over the Ciphertext and Additional
Authenticated Data. AEAD algorithms accept two inputs, the
Plaintext and the Additional Authenticated Data value, and produce
two outputs, the Ciphertext and the Authentication Tag value. AES
Galois/Counter Mode (GCM) is one such algorithm.
Jones, et al. Expires March 7, 2014 [Page 5]
Internet-Draft JWE September 2013
Plaintext The sequence of octets to be encrypted -- a.k.a., the
message. The plaintext can contain an arbitrary sequence of
octets.
Ciphertext An encrypted representation of the Plaintext.
Additional Authenticated Data (AAD) An input to an AEAD operation
that is integrity protected but not encrypted.
Authentication Tag An output of an AEAD operation that ensures the
integrity of the Ciphertext and the Additional Authenticated Data.
Note that some algorithms may not use an Authentication Tag, in
which case this value is the empty octet sequence.
Content Encryption Key (CEK) A symmetric key for the AEAD algorithm
used to encrypt the Plaintext for the recipient to produce the
Ciphertext and the Authentication Tag.
JSON Text Object A UTF-8 [RFC3629] encoded text string representing
a JSON object; the syntax of JSON objects is defined in Section
2.2 of [RFC4627].
JWE Header A JSON Text Object (or JSON Text Objects, when using the
JWE JSON Serialization) that describes the encryption operations
applied to create the JWE Encrypted Key, the JWE Ciphertext, and
the JWE Authentication Tag. The members of the JWE Header
object(s) are Header Parameters.
JWE Encrypted Key The result of encrypting the Content Encryption
Key (CEK) with the intended recipient's key using the specified
algorithm. Note that for some algorithms, the JWE Encrypted Key
value is specified as being the empty octet sequence.
JWE Initialization Vector A sequence of octets containing the
Initialization Vector used when encrypting the Plaintext. Note
that some algorithms may not use an Initialization Vector, in
which case this value is the empty octet sequence.
JWE Ciphertext A sequence of octets containing the Ciphertext for a
JWE.
JWE Authentication Tag A sequence of octets containing the
Authentication Tag for a JWE.
JWE Protected Header A JSON Text Object that contains the portion of
the JWE Header that is integrity protected. For the JWE Compact
Serialization, this comprises the entire JWE Header. For the JWE
JSON Serialization, this is one component of the JWE Header.
Jones, et al. Expires March 7, 2014 [Page 6]
Internet-Draft JWE September 2013
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 Base64 encoding using the URL- and filename-safe
character set defined in Section 5 of RFC 4648 [RFC4648], with all
trailing '=' characters omitted (as permitted by Section 3.2).
(See Appendix C of [JWS] for notes on implementing base64url
encoding without padding.)
Encoded JWE Header Base64url encoding of the JWE Protected Header.
Encoded JWE Encrypted Key Base64url encoding of the JWE Encrypted
Key.
Encoded JWE Initialization Vector Base64url encoding of the JWE
Initialization Vector.
Encoded JWE Ciphertext Base64url encoding of the JWE Ciphertext.
Encoded JWE Authentication Tag Base64url encoding of the JWE
Authentication Tag.
JWE Compact Serialization A representation of the JWE as the
concatenation of the Encoded JWE Header, the Encoded JWE Encrypted
Key, the Encoded JWE Initialization Vector, the Encoded JWE
Ciphertext, and the Encoded JWE Authentication Tag in that order,
with the five strings being separated by four period ('.')
characters. This representation is compact and URL-safe.
JWE JSON Serialization A representation of the JWE as a JSON
structure containing JWE Header, Encoded JWE Encrypted Key,
Encoded JWE Initialization Vector, Encoded JWE Ciphertext, and
Encoded JWE Authentication Tag values. Unlike the JWE Compact
Serialization, the JWE JSON Serialization enables the same content
to be encrypted to multiple parties. This representation is
neither compact nor URL-safe.
Collision Resistant Namespace A namespace that allows names to be
allocated in a manner such that they are highly unlikely to
collide with other names. Examples of Collision Resistant
Namespaces include: Domain Names, Object Identifiers (OIDs) as
defined in the ITU-T X.660 and X.670 Recommendation series, and
Universally Unique IDentifiers (UUIDs) [RFC4122]. When using an
administratively delegated namespace, the definer of a name needs
to take reasonable precautions to ensure they are in control of
Jones, et al. Expires March 7, 2014 [Page 7]
Internet-Draft JWE September 2013
the portion of the namespace they use to define the name.
StringOrURI A JSON string value, with the additional requirement
that while arbitrary string values MAY be used, any value
containing a ":" character MUST be a URI [RFC3986]. StringOrURI
values are compared as case-sensitive strings with no
transformations or canonicalizations applied.
Key Management Mode A method of determining the Content Encryption
Key (CEK) value to use. Each algorithm used for determining the
CEK value uses a specific Key Management Mode. Key Management
Modes employed by this specification are Key Encryption, Key
Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping,
and Direct Encryption.
Key Encryption A Key Management Mode in which the Content Encryption
Key (CEK) value is encrypted to the intended recipient using an
asymmetric encryption algorithm.
Key Wrapping A Key Management Mode in which the Content Encryption
Key (CEK) value is encrypted to the intended recipient using a
symmetric key wrapping algorithm.
Direct Key Agreement A Key Management Mode in which a key agreement
algorithm is used to agree upon the Content Encryption Key (CEK)
value.
Key Agreement with Key Wrapping A Key Management Mode in which a key
agreement algorithm is used to agree upon a symmetric key used to
encrypt the Content Encryption Key (CEK) value to the intended
recipient using a symmetric key wrapping algorithm.
Direct Encryption A Key Management Mode in which the Content
Encryption Key (CEK) value used is the secret symmetric key value
shared between the parties.
3. JSON Web Encryption (JWE) Overview
JWE represents encrypted content using JSON data structures and
base64url encoding. Five values are represented in a JWE: the JWE
Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE
Ciphertext, and the JWE Authentication Tag. In the Compact
Serialization, the five values are base64url-encoded for
transmission, and represented as the concatenation of the encoded
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 7.2.
Jones, et al. Expires March 7, 2014 [Page 8]
Internet-Draft JWE September 2013
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 for
key encryption and AES GCM for content encryption.
The following example JWE Header declares that:
o the Content Encryption Key is encrypted to the recipient using the
RSAES OAEP algorithm to produce the JWE Encrypted Key and
o the Plaintext is encrypted using the AES GCM algorithm with a 256
bit key to produce the Ciphertext.
{"alg":"RSA-OAEP","enc":"A256GCM"}
Base64url encoding the octets of the UTF-8 representation of the JWE
Header yields this Encoded JWE Header value:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
The remaining steps to finish creating this JWE are:
o Generate a random Content Encryption Key (CEK).
o Encrypt the CEK with the recipient's public key using the RSAES
OAEP algorithm to produce the JWE Encrypted Key.
o Base64url encode the JWE Encrypted Key to produce the Encoded JWE
Encrypted Key.
o Generate a random JWE Initialization Vector.
o Base64url encode the JWE Initialization Vector to produce the
Encoded JWE Initialization Vector.
o Let the Additional Authenticated Data encryption parameter be the
octets of the ASCII representation of the Encoded JWE Header
value.
o Encrypt the Plaintext with AES GCM using the CEK as the encryption
key, the JWE Initialization Vector, and the Additional
Authenticated Data value, requesting a 128 bit Authentication Tag
Jones, et al. Expires March 7, 2014 [Page 9]
Internet-Draft JWE September 2013
output.
o Base64url encode the Ciphertext to create the Encoded JWE
Ciphertext.
o Base64url encode the Authentication Tag to create the Encoded JWE
Authentication Tag.
o Assemble the final representation: The Compact Serialization of
this result is the concatenation of the Encoded JWE Header, the
Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector,
the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag
in that order, with the five strings being separated by four
period ('.') characters.
The final result in this example (with line breaks for display
purposes only) is:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
6UklfCpIMfIjf7iGdXKHzg.
48V1_ALb6US04U3b.
5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
SdiwkIr3ajwQzaBtQD_A.
XFBoMYUZodetZdvTiFvSkQ
See Appendix A.1 for the complete details of computing this JWE. See
Appendix A for additional examples.
4. JWE Header
The members of the JSON object(s) representing the JWE Header
describe the encryption applied to the Plaintext and optionally
additional properties of the JWE. The Header Parameter Names within
the JWE Header MUST be unique; recipients MUST either reject JWEs
with duplicate Header Parameter Names or use a JSON parser that
returns only the lexically last duplicate member name, as specified
in Section 15.12 (The JSON Object) of ECMAScript 5.1 [ECMAScript].
Implementations are required to understand the specific header
parameters defined by this specification that are designated as "MUST
be understood" and process them in the manner defined in this
specification. All other header parameters defined by this
Jones, et al. Expires March 7, 2014 [Page 10]
Internet-Draft JWE September 2013
specification that are not so designated MUST be ignored when not
understood. Unless listed as a critical header parameter, per
Section 4.1.12, all header parameters not defined by this
specification MUST be ignored when not understood.
There are three classes of Header Parameter Names: 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.
Additional reserved Header Parameter Names can be defined via the
IANA JSON Web Signature and Encryption Header Parameters registry
[JWS]. As indicated by the common registry, JWSs and JWEs share a
common header parameter space; when a parameter is used by both
specifications, its usage must be compatible between the
specifications.
4.1.1. "alg" (Algorithm) Header Parameter
The "alg" (algorithm) header parameter identifies the cryptographic
algorithm used to encrypt or determine the value of the Content
Encryption Key (CEK). The encrypted content is not usable if the
"alg" value does not represent a supported algorithm, or if the
recipient does not have a key that can be used with that algorithm.
"alg" values SHOULD either be registered in the IANA JSON Web
Signature and Encryption Algorithms registry [JWA] or be a value that
contains a Collision Resistant Namespace. The "alg" value is a case
sensitive string containing a StringOrURI value. Use of this header
parameter is REQUIRED. This header parameter MUST be understood by
implementations.
A list of defined "alg" values can be found in the IANA JSON Web
Signature and Encryption Algorithms registry [JWA]; the initial
contents of this registry are the values defined in Section 4.1 of
the JSON Web Algorithms (JWA) [JWA] specification.
4.1.2. "enc" (Encryption Method) Header Parameter
The "enc" (encryption method) header parameter identifies the content
encryption algorithm used to encrypt the Plaintext to produce the
Ciphertext. This algorithm MUST be an AEAD algorithm with a
specified key length. The recipient MUST reject the JWE if the "enc"
value does not represent a supported algorithm. "enc" values SHOULD
either be registered in the IANA JSON Web Signature and Encryption
Jones, et al. Expires March 7, 2014 [Page 11]
Internet-Draft JWE September 2013
Algorithms registry [JWA] or be a value that contains a Collision
Resistant Namespace. The "enc" value is a case sensitive string
containing a StringOrURI value. Use of this header parameter is
REQUIRED. This header parameter MUST be understood by
implementations.
A list of defined "enc" values can be found in the IANA JSON Web
Signature and Encryption Algorithms registry [JWA]; the initial
contents of this registry are the values defined in Section 4.2 of
the JSON Web Algorithms (JWA) [JWA] specification.
4.1.3. "zip" (Compression Algorithm) Header Parameter
The "zip" (compression algorithm) applied to the Plaintext before
encryption, if any. If present, the value of the "zip" header
parameter MUST be the case sensitive string "DEF". Compression is
performed with the DEFLATE [RFC1951] algorithm. If no "zip"
parameter is present, no compression is applied to the Plaintext
before encryption. This header parameter MUST be integrity
protected, and therefore MUST occur only with the JWE Protected
Header, when used. Use of this header parameter is OPTIONAL. This
header parameter MUST be understood by implementations.
4.1.4. "jku" (JWK Set URL) Header Parameter
The "jku" (JWK Set URL) header parameter is a URI [RFC3986] that
refers to a resource for a set of JSON-encoded public keys, one of
which is the key to which the JWE was encrypted; this can be used to
determine the private key needed to decrypt the JWE. The keys MUST
be encoded as a JSON Web Key Set (JWK Set) [JWK]. The protocol used
to acquire the resource MUST provide integrity protection; an HTTP
GET request to retrieve the JWK Set MUST use TLS [RFC2818] [RFC5246];
the identity of the server MUST be validated, as per Section 3.1 of
HTTP Over TLS [RFC2818]. Use of this header parameter is OPTIONAL.
4.1.5. "jwk" (JSON Web Key) Header Parameter
The "jwk" (JSON Web Key) header parameter is the public key to which
the JWE was encrypted; this can be used to determine the private key
needed to decrypt the JWE. This key is represented as a JSON Web Key
[JWK]. Use of this header parameter is OPTIONAL.
4.1.6. "x5u" (X.509 URL) Header Parameter
The "x5u" (X.509 URL) header parameter is a URI [RFC3986] that refers
to a resource for the X.509 public key certificate or certificate
chain [RFC5280] containing the key to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the
Jones, et al. Expires March 7, 2014 [Page 12]
Internet-Draft JWE September 2013
JWE. The identified resource MUST provide a representation of the
certificate or certificate chain that conforms to RFC 5280 [RFC5280]
in PEM encoded form [RFC1421]. The certificate containing the public
key to which the JWE was encrypted MUST be the first certificate.
This MAY be followed by additional certificates, with each subsequent
certificate being the one used to certify the previous one. The
protocol used to acquire the resource MUST provide integrity
protection; an HTTP GET request to retrieve the certificate MUST use
TLS [RFC2818] [RFC5246]; the identity of the server MUST be
validated, as per Section 3.1 of HTTP Over TLS [RFC2818]. Use of
this header parameter is OPTIONAL.
4.1.7. "x5t" (X.509 Certificate Thumbprint) Header Parameter
The "x5t" (X.509 Certificate Thumbprint) header parameter is a
base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER
encoding of the X.509 certificate [RFC5280] containing the key to
which the JWE was encrypted; this can be used to determine the
private key needed to decrypt the JWE. Use of this header parameter
is OPTIONAL.
If, in the future, certificate thumbprints need to be computed using
hash functions other than SHA-1, it is suggested that additional
related header parameters be defined for that purpose. For example,
it is suggested that a new "x5t#S256" (X.509 Certificate Thumbprint
using SHA-256) header parameter could be defined by registering it in
the IANA JSON Web Signature and Encryption Header Parameters registry
[JWS].
4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter
The "x5c" (X.509 Certificate Chain) header parameter contains the
X.509 public key certificate or certificate chain [RFC5280]
containing the key to which the JWE was encrypted; this can be used
to determine the private key needed to decrypt the JWE. The
certificate or certificate chain is represented as a JSON array of
certificate value strings. Each string in the array is a base64
encoded ([RFC4648] Section 4 -- not base64url encoded) DER
[ITU.X690.1994] PKIX certificate value. The certificate containing
the public key to which the JWE was encrypted MUST be the first
certificate. This MAY be followed by additional certificates, with
each subsequent certificate being the one used to certify the
previous one. Use of this header parameter is OPTIONAL.
See Appendix B of [JWS] for an example "x5c" value.
Jones, et al. Expires March 7, 2014 [Page 13]
Internet-Draft JWE September 2013
4.1.9. "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.
4.1.10. "typ" (Type) Header Parameter
The "typ" (type) header parameter MAY be used to declare the type of
this complete JWE object in an application-specific manner in
contexts where this is useful to the application. This parameter has
no effect upon the JWE processing. The type value "JOSE" MAY be used
by applications to indicate that this object is a JWS or JWE using
the JWS Compact Serialization or the JWE Compact Serialization. The
type value "JOSE+JSON" MAY be used by applications to indicate that
this object is a JWS or JWE using the JWS JSON Serialization or 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] values MAY be used as "typ" values.
"typ" values SHOULD either be registered in the IANA JSON Web
Signature and Encryption Type Values registry [JWS] or be a value
that contains a Collision Resistant Namespace.
4.1.11. "cty" (Content Type) Header Parameter
The "cty" (content type) header parameter MAY be used to declare the
type of the encrypted content (the Plaintext) in an application-
specific manner in contexts where this is useful to the application.
This parameter has no effect upon the JWE processing. 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.
Jones, et al. Expires March 7, 2014 [Page 14]
Internet-Draft JWE September 2013
4.1.12. "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 ]] or
by [JWA] for use with JWE, 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 by
[JWA] for use with JWE, 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] or be a Public Name: a
value that contains a Collision Resistant Namespace. In each case,
the definer of the name or value needs to take reasonable precautions
to make sure they are in control of the part of the namespace they
use to define the Header Parameter Name.
New header parameters should be introduced sparingly, as they can
result in non-interoperable JWEs.
4.3. Private Header Parameter Names
A producer and consumer of a JWE may agree to use Header Parameter
Names that are Private Names: names that are not Reserved Names
Section 4.1 or Public Names Section 4.2. Unlike Public Names,
Jones, et al. Expires March 7, 2014 [Page 15]
Internet-Draft JWE September 2013
Private Names are subject to collision and should be used with
caution.
5. Producing and Consuming JWEs
5.1. Message Encryption
The message encryption process is as follows. The order of the steps
is not significant in cases where there are no dependencies between
the inputs and outputs of the steps.
1. Determine the Key Management Mode employed by the algorithm used
to determine the Content Encryption Key (CEK) value. (This is
the algorithm recorded in the "alg" (algorithm) header parameter
of the resulting JWE.)
2. When Key Wrapping, Key Encryption, or Key Agreement with Key
Wrapping are employed, generate a random Content Encryption Key
(CEK) value. See RFC 4086 [RFC4086] for considerations on
generating random values. The CEK MUST have a length equal to
that required for the content encryption algorithm.
3. When Direct Key Agreement or Key Agreement with Key Wrapping are
employed, use the key agreement algorithm to compute the value
of the agreed upon key. When Direct Key Agreement is employed,
let the Content Encryption Key (CEK) be the agreed upon key.
When Key Agreement with Key Wrapping is employed, the agreed
upon key will be used to wrap the CEK.
4. When Key Wrapping, Key Encryption, or Key Agreement with Key
Wrapping are employed, encrypt the CEK to the recipient and let
the result be the JWE Encrypted Key.
5. Otherwise, when Direct Key Agreement or Direct Encryption are
employed, let the JWE Encrypted Key be the empty octet sequence.
6. When Direct Encryption is employed, let the Content Encryption
Key (CEK) be the shared symmetric key.
7. 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 content encryption algorithm (if required for the
Jones, et al. Expires March 7, 2014 [Page 16]
Internet-Draft JWE September 2013
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 and no "protected" member is
present), 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 content
encryption algorithm to create the JWE Ciphertext value and the
JWE Authentication Tag (which is the Authentication Tag output
from the encryption operation).
17. 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 7.2.
Jones, et al. Expires March 7, 2014 [Page 17]
Internet-Draft JWE September 2013
5.2. Message Decryption
The message decryption process is the reverse of the encryption
process. The order of the steps is not significant in cases where
there are no dependencies between the inputs and outputs of the
steps. If any of these steps fails, the encrypted content cannot be
validated.
It is an application decision which recipients' encrypted content
must successfully validate for the JWE to be accepted. In some
cases, encrypted content for all recipients must successfully
validate or the JWE will be rejected. In other cases, only the
encrypted content for a single recipient needs to be successfully
validated. However, in all cases, the encrypted content for at least
one recipient MUST successfully validate or 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 7.2.
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 [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.
Jones, et al. Expires March 7, 2014 [Page 18]
Internet-Draft JWE September 2013
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 content encryption algorithm.
Note that when there are multiple recipients, each recipient
will only be able decrypt any JWE Encrypted Key values that were
encrypted to a key in that recipient's possession. It is
therefore normal to only be able to decrypt one of the per-
recipient JWE Encrypted Key values to obtain the CEK value. To
mitigate the attacks described in RFC 3218 [RFC3218], the
recipient MUST NOT distinguish between format, padding, and
length errors of encrypted keys. It is strongly recommended, in
the event of receiving an improperly formatted key, that the
receiver substitute a randomly generated CEK and proceed to the
next step, to mitigate timing attacks.
11. Otherwise, when Direct Key Agreement or Direct Encryption are
employed, verify that the JWE Encrypted Key value is empty octet
sequence.
12. When Direct Encryption is employed, let the Content Encryption
Key (CEK) be the shared symmetric key.
13. If the JWE JSON Serialization is being used, repeat this process
for each recipient contained in the representation until the CEK
value has been determined.
14. Let the Additional Authenticated Data encryption parameter be
the octets of the ASCII representation of the Encoded JWE Header
value. However if a top-level "aad" member is present when
using the JWE JSON Serialization, instead let the Additional
Jones, et al. Expires March 7, 2014 [Page 19]
Internet-Draft JWE September 2013
Authenticated Data encryption parameter be the octets of the
ASCII representation of the concatenation of the Encoded JWE
Header value, a period ('.') character, and the "aad" field
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 content 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].
6. Key Identification
It is necessary for the recipient of a JWE to be able to determine
the key that was employed for the encryption operation. The key
employed can be identified using the Header Parameter methods
described in Section 4.1 or can be identified using methods that are
outside the scope of this specification. Specifically, the Header
Parameters "jku", "jwk", "x5u", "x5t", "x5c", and "kid" can be used
to identify the key used. These header parameters MUST be integrity
protected if the information about the key that they convey is to be
considered trusted.
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. Validation of
the encrypted content fails when the key used cannot be determined.
Jones, et al. Expires March 7, 2014 [Page 20]
Internet-Draft JWE September 2013
The means of exchanging any shared symmetric keys used is outside the
scope of this specification.
7. Serializations
JWE objects use one of two serializations, the JWE Compact
Serialization or the JWE JSON Serialization. The JWE Compact
Serialization is mandatory to implement. Implementation of the JWE
JSON Serialization is OPTIONAL.
7.1. JWE Compact Serialization
The JWE Compact Serialization represents encrypted content as a
compact URL-safe string. This string 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. Only one recipient is
supported by the JWE Compact Serialization.
7.2. JWE JSON Serialization
The JWE JSON Serialization represents encrypted content as a JSON
object. Unlike the JWE Compact Serialization, content using the JWE
JSON Serialization can be encrypted to more than one recipient.
The representation is closely related to that used in the JWE Compact
Serialization, with the following differences for the JWE JSON
Serialization:
o Values in the JWE JSON Serialization are represented as members of
a JSON object, rather than as base64url encoded strings separated
by period ('.') characters. (However binary values and values
that are integrity protected are still base64url encoded.)
o The Encoded JWE Header value, if non-empty, is stored in the
"protected" member.
o The Encoded JWE Initialization Vector value, if non-empty, is
stored in the "iv" member.
o The Encoded JWE Ciphertext value is stored in the "ciphertext"
member.
o The Encoded JWE Authentication Tag value, if non-empty, is stored
in the "tag" member.
Jones, et al. Expires March 7, 2014 [Page 21]
Internet-Draft JWE September 2013
o The JWE can be encrypted to multiple recipients, rather than just
one. A JSON array in the "recipients" member is used to hold
values that are specific to a particular recipient, with one array
element per recipient represented. These array elements are JSON
objects.
o Each Encoded JWE Encrypted Key value, if non-empty, is stored in
the "encrypted_key" member of a JSON object that is an element of
the "recipients" array.
o Some header parameter values, such as the "alg" value and
parameters used for selecting keys, can also differ for different
recipient computations. Per-recipient header parameter values, if
present, are stored in the "header" members of the same JSON
objects that are elements of the "recipients" array.
o Some header parameters, including the "alg" parameter, can be
shared among all recipient computations. 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, if present, are JSON Text Objects
containing Header Parameters.
o Not all header parameters are integrity protected. The shared
header parameters in the "protected" member are integrity
protected, and are base64url encoded. The per-recipient header
parameters in the "header" array element members and the shared
header parameters in the "unprotected" member are not integrity
protected. These JSON Text Objects containing header parameters
that are not integrity protected are not base64url encoded.
o The header parameter values used when creating or validating per-
recipient Ciphertext and Authentication Tag values are the union
of the three sets of header parameter values that may be present:
(1) the per-recipient values in the "header" member of the
recipient's array element, (2) the shared integrity-protected
values in the "protected" member, and (3) the shared non-
integrity-protected values in the "unprotected" member. The union
of these sets of header parameters comprises the JWE Header. The
header parameter names in the three locations MUST be disjoint.
o An "aad" (Additional Authenticated Data) member can be included to
supply a base64url encoded value to be integrity protected but not
encrypted. (Note that this can also be achieved when using either
serialization by including the AAD value as a protected header
parameter value, but at the cost of the value being double
base64url encoded.)
Jones, et al. Expires March 7, 2014 [Page 22]
Internet-Draft JWE September 2013
o The "recipients" array MUST always be present, even if the array
elements contain only the empty JSON object "{}" (which can happen
when all header parameter values are shared between all recipients
and when no encrypted key is used, such as when doing Direct
Encryption).
The syntax of a JWE using the JWE JSON Serialization is as follows:
{"protected":<integrity-protected shared header contents>",
"unprotected":<non-integrity-protected shared header contents>",
"recipients":[
{"header":"<per-recipient unprotected header 1 contents>",
"encrypted_key":"<encrypted key 1 contents>"},
...
{"header":"<per-recipient unprotected header N contents>",
"encrypted_key":"<encrypted key N contents>"}],
"aad":"<additional authenticated data contents>",
"iv":"<initialization vector contents>",
"ciphertext":"<ciphertext contents>",
"tag":"<authentication tag contents>"
}
Of these members, only the "ciphertext" member MUST be present. The
"iv", "tag", and "encrypted_key" members MUST be present when
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
Jones, et al. Expires March 7, 2014 [Page 23]
Internet-Draft JWE September 2013
Ciphertext and JWE Authentication Tag values match those produced for
the JWE Compact Serialization, provided that the Encoded JWE Header
value (which represents the integrity-protected header parameter
values) matches that used in the JWE Compact Serialization.
All recipients use the same JWE Protected Header, JWE Initialization
Vector, JWE Ciphertext, and JWE Authentication Tag values, resulting
in potentially significant space savings if the message is large.
Therefore, all header parameters that specify the treatment of the
Plaintext value MUST be the same for all recipients. This primarily
means that the "enc" (encryption method) header parameter value in
the JWE Header for each recipient and any parameters of that
algorithm MUST be the same.
See Appendix A.4 for an example of computing a JWE using the JWE JSON
Serialization.
8. Distinguishing Between JWS and JWE Objects
There are several ways of distinguishing whether an object is a JWS
or JWE object. All these methods will yield the same result for all
legal input values.
o If the object is using the JWS Compact Serialization or the JWE
Compact Serialization, the number of base64url encoded segments
separated by period ('.') characters differs for JWSs and JWEs.
JWSs have three segments separated by two period ('.') characters.
JWEs have five segments separated by four period ('.') characters.
o If the object is using the JWS JSON Serialization or the JWE JSON
Serialization, the members used will be different. JWSs have a
"signatures" member and JWEs do not. JWEs have a "recipients"
member and JWSs do not.
o A JWS Header can be distinguished from a JWE header by examining
the "alg" (algorithm) header parameter value. If the value
represents a digital signature or MAC algorithm, or is the value
"none", it is for a JWS; if it represents a Key Encryption, Key
Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping,
or Direct Encryption algorithm, it is for a JWE.
o A JWS Header can also be distinguished from a JWE header by
determining whether an "enc" (encryption method) member exists.
If the "enc" member exists, it is a JWE; otherwise, it is a JWS.
Jones, et al. Expires March 7, 2014 [Page 24]
Internet-Draft JWE September 2013
9. IANA Considerations
9.1. Registration of JWE Header Parameter Names
This specification registers the Header Parameter Names defined in
Section 4.1 in the IANA JSON Web Signature and Encryption Header
Parameters registry [JWS].
9.1.1. Registry Contents
o Header Parameter Name: "alg"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.1 of [[ this document ]]
o Header Parameter Name: "enc"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.2 of [[ this document ]]
o Header Parameter Name: "zip"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.3 of [[ this document ]]
o Header Parameter Name: "jku"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.4 of [[ this document ]]
o Header Parameter Name: "jwk"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification document(s): Section 4.1.5 of [[ this document ]]
o Header Parameter Name: "x5u"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.6 of [[ this document ]]
o Header Parameter Name: "x5t"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.7 of [[ this document ]]
o Header Parameter Name: "x5c"
Jones, et al. Expires March 7, 2014 [Page 25]
Internet-Draft JWE September 2013
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.8 of [[ this document ]]
o Header Parameter Name: "kid"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.9 of [[ this document ]]
o Header Parameter Name: "typ"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.10 of [[ this document ]]
o Header Parameter Name: "cty"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.11 of [[ this document ]]
o Header Parameter Name: "crit"
o Header Parameter Usage Location(s): JWE
o Change Controller: IETF
o Specification Document(s): Section 4.1.12 of [[ this document ]]
10. Security Considerations
All of the security issues faced by any cryptographic application
must be faced by a JWS/JWE/JWK agent. Among these issues are
protecting the user's private and symmetric keys, preventing various
attacks, and helping the user avoid mistakes such as inadvertently
encrypting a message for the wrong recipient. The entire list of
security considerations is beyond the scope of this document.
All the security considerations in the JWS specification also apply
to this specification. Likewise, all the security considerations in
XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313] also apply, other
than those that are XML specific.
When decrypting, particular care must be taken not to allow the JWE
recipient to be used as an oracle for decrypting messages. RFC 3218
[RFC3218] should be consulted for specific countermeasures to attacks
on RSAES-PKCS1-V1_5. An attacker might modify the contents of the
"alg" parameter from "RSA-OAEP" to "RSA1_5" in order to generate a
formatting error that can be detected and used to recover the CEK
even if RSAES OAEP was used to encrypt the CEK. It is therefore
particularly important to report all formatting errors to the CEK,
Additional Authenticated Data, or ciphertext as a single error when
Jones, et al. Expires March 7, 2014 [Page 26]
Internet-Draft JWE September 2013
the encrypted content is rejected.
11. References
11.1. Normative References
[ECMAScript]
Ecma International, "ECMAScript Language Specification,
5.1 Edition", ECMA 262, June 2011.
[ITU.X690.1994]
International Telecommunications Union, "Information
Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, 1994.
[JWA] Jones, M., "JSON Web Algorithms (JWA)",
draft-ietf-jose-json-web-algorithms (work in progress),
September 2013.
[JWK] Jones, M., "JSON Web Key (JWK)",
draft-ietf-jose-json-web-key (work in progress),
September 2013.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", draft-ietf-jose-json-web-signature (work
in progress), September 2013.
[RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic
Mail: Part I: Message Encryption and Authentication
Procedures", RFC 1421, February 1993.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
version 1.3", RFC 1951, May 1996.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
Jones, et al. Expires March 7, 2014 [Page 27]
Internet-Draft JWE September 2013
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[W3C.CR-xmlenc-core1-20120313]
Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch,
"XML Encryption Syntax and Processing Version 1.1", World
Wide Web Consortium CR CR-xmlenc-core1-20120313,
March 2012,
<http://www.w3.org/TR/2012/CR-xmlenc-core1-20120313>.
11.2. Informative References
[I-D.mcgrew-aead-aes-cbc-hmac-sha2]
McGrew, D. and K. Paterson, "Authenticated Encryption with
AES-CBC and HMAC-SHA",
draft-mcgrew-aead-aes-cbc-hmac-sha2-01 (work in progress),
October 2012.
[I-D.rescorla-jsms]
Rescorla, E. and J. Hildebrand, "JavaScript Message
Security Format", draft-rescorla-jsms-00 (work in
progress), March 2011.
[JSE] Bradley, J. and N. Sakimura (editor), "JSON Simple
Encryption", September 2010.
[RFC3218] Rescorla, E., "Preventing the Million Message Attack on
Cryptographic Message Syntax", RFC 3218, January 2002.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Jones, et al. Expires March 7, 2014 [Page 28]
Internet-Draft JWE September 2013
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009.
Appendix A. JWE Examples
This section provides examples of JWE computations.
A.1. Example JWE using RSAES OAEP and AES GCM
This example encrypts the plaintext "The true sign of intelligence is
not knowledge but imagination." to the recipient using RSAES OAEP for
key encryption and AES GCM for content encryption. The
representation of this plaintext is:
[84, 104, 101, 32, 116, 114, 117, 101, 32, 115, 105, 103, 110, 32,
111, 102, 32, 105, 110, 116, 101, 108, 108, 105, 103, 101, 110, 99,
101, 32, 105, 115, 32, 110, 111, 116, 32, 107, 110, 111, 119, 108,
101, 100, 103, 101, 32, 98, 117, 116, 32, 105, 109, 97, 103, 105,
110, 97, 116, 105, 111, 110, 46]
A.1.1. JWE Header
The following example JWE Header declares that:
o the Content Encryption Key is encrypted to the recipient using the
RSAES OAEP algorithm to produce the JWE Encrypted Key and
o the Plaintext is encrypted using the AES GCM algorithm with a 256
bit key to produce the Ciphertext.
{"alg":"RSA-OAEP","enc":"A256GCM"}
A.1.2. Encoded JWE Header
Base64url encoding the octets of the UTF-8 representation of the JWE
Header yields this Encoded JWE Header value:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
Jones, et al. Expires March 7, 2014 [Page 29]
Internet-Draft JWE September 2013
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. This example uses the RSA
key represented in JSON Web Key [JWK] format below (with line breaks
for display purposes only):
{"kty":"RSA",
"n":"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW
cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S
psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a
sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS
tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj
YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw",
"e":"AQAB",
"d":"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N
WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9
3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk
qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl
t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd
VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ"
}
The resulting JWE Encrypted Key value is:
[56, 163, 154, 192, 58, 53, 222, 4, 105, 218, 136, 218, 29, 94, 203,
22, 150, 92, 129, 94, 211, 232, 53, 89, 41, 60, 138, 56, 196, 216,
82, 98, 168, 76, 37, 73, 70, 7, 36, 8, 191, 100, 136, 196, 244, 220,
145, 158, 138, 155, 4, 117, 141, 230, 199, 247, 173, 45, 182, 214,
74, 177, 107, 211, 153, 11, 205, 196, 171, 226, 162, 128, 171, 182,
13, 237, 239, 99, 193, 4, 91, 219, 121, 223, 107, 167, 61, 119, 228,
173, 156, 137, 134, 200, 80, 219, 74, 253, 56, 185, 91, 177, 34, 158,
89, 154, 205, 96, 55, 18, 138, 43, 96, 218, 215, 128, 124, 75, 138,
243, 85, 25, 109, 117, 140, 26, 155, 249, 67, 167, 149, 231, 100, 6,
41, 65, 214, 251, 232, 87, 72, 40, 182, 149, 154, 168, 31, 193, 126,
215, 89, 28, 111, 219, 125, 182, 139, 235, 195, 197, 23, 234, 55, 58,
63, 180, 68, 202, 206, 149, 75, 205, 248, 176, 67, 39, 178, 60, 98,
193, 32, 238, 122, 96, 158, 222, 57, 183, 111, 210, 55, 188, 215,
206, 180, 166, 150, 166, 106, 250, 55, 229, 72, 40, 69, 214, 216,
Jones, et al. Expires March 7, 2014 [Page 30]
Internet-Draft JWE September 2013
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 this 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,
Jones, et al. Expires March 7, 2014 [Page 31]
Internet-Draft JWE September 2013
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
Jones, et al. Expires March 7, 2014 [Page 32]
Internet-Draft JWE September 2013
A.1.12. Validation
This example illustrates the process of creating a JWE with RSAES
OAEP for key encryption and AES GCM for content encryption. These
results can be used to validate JWE decryption implementations for
these algorithms. Note that since the RSAES OAEP computation
includes random values, the encryption results above will not be
completely reproducible. However, since the AES GCM computation is
deterministic, the JWE Encrypted Ciphertext values will be the same
for all encryptions performed using these inputs.
A.2. Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256
This example encrypts the plaintext "Live long and prosper." to the
recipient using RSAES-PKCS1-V1_5 for key encryption and
AES_128_CBC_HMAC_SHA_256 for content encryption. The representation
of this plaintext is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
112, 114, 111, 115, 112, 101, 114, 46]
A.2.1. JWE Header
The following example JWE Header (with line breaks for display
purposes only) declares that:
o the Content Encryption Key is encrypted to the recipient using the
RSAES-PKCS1-V1_5 algorithm to produce the JWE Encrypted Key and
o the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
algorithm to produce the Ciphertext.
{"alg":"RSA1_5","enc":"A128CBC-HS256"}
A.2.2. Encoded JWE Header
Base64url encoding the octets of the UTF-8 representation of the JWE
Header yields this Encoded JWE Header value:
eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
A.2.3. Content Encryption Key (CEK)
Generate a 256 bit random Content Encryption Key (CEK). In this
example, the key value is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
Jones, et al. Expires March 7, 2014 [Page 33]
Internet-Draft JWE September 2013
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. This example
uses the RSA key represented in JSON Web Key [JWK] format below (with
line breaks for display purposes only):
{"kty":"RSA",
"n":"sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl
UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre
cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_
7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI
Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU
7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw",
"e":"AQAB",
"d":"VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq
1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry
nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_
0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj
-VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj
T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ"
}
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]
Jones, et al. Expires March 7, 2014 [Page 34]
Internet-Draft JWE September 2013
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 this Encoded JWE Initialization
Vector value:
AxY8DCtDaGlsbGljb3RoZQ
A.2.7. Additional Authenticated Data
Let the Additional Authenticated Data encryption parameter be the
octets of the ASCII representation of the Encoded JWE Header value.
This AAD value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
120, 88, 122, 85, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105,
74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85,
50, 73, 110, 48]
A.2.8. Plaintext Encryption
Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256 using the CEK as
the encryption key, the JWE Initialization Vector, and the Additional
Authenticated Data value above. The steps for doing this using the
values from Appendix A.3 are detailed in Appendix B. The resulting
Ciphertext is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102]
Jones, et al. Expires March 7, 2014 [Page 35]
Internet-Draft JWE September 2013
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 for key encryption and AES_CBC_HMAC_SHA2 for content
encryption. These results can be used to validate JWE decryption
implementations for these algorithms. Note that since the RSAES-
Jones, et al. Expires March 7, 2014 [Page 36]
Internet-Draft JWE September 2013
PKCS1-V1_5 computation includes random values, the encryption results
above will not be completely reproducible. However, since the AES
CBC computation is deterministic, the JWE Encrypted Ciphertext values
will be the same for all encryptions performed using these inputs.
A.3. Example JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256
This example encrypts the plaintext "Live long and prosper." to the
recipient using AES Key Wrap for key encryption and AES GCM for
content encryption. The representation of this plaintext is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
112, 114, 111, 115, 112, 101, 114, 46]
A.3.1. JWE Header
The following example JWE Header declares that:
o the Content Encryption Key is encrypted to the recipient using the
AES Key Wrap algorithm with a 128 bit key to produce the JWE
Encrypted Key and
o the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
algorithm to produce the Ciphertext.
{"alg":"A128KW","enc":"A128CBC-HS256"}
A.3.2. Encoded JWE Header
Base64url encoding the octets of the UTF-8 representation of the JWE
Header yields this Encoded JWE Header value:
eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
A.3.3. Content Encryption Key (CEK)
Generate a 256 bit random Content Encryption Key (CEK). In this
example, the value is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
44, 207]
A.3.4. Key Encryption
Encrypt the CEK with the shared symmetric key using the AES Key Wrap
algorithm to produce the JWE Encrypted Key. This example uses the
Jones, et al. Expires March 7, 2014 [Page 37]
Internet-Draft JWE September 2013
symmetric key represented in JSON Web Key [JWK] format below:
{"kty":"oct",
"k":"GawgguFyGrWKav7AX4VKUg"
}
The resulting JWE Encrypted Key value is:
[232, 160, 123, 211, 183, 76, 245, 132, 200, 128, 123, 75, 190, 216,
22, 67, 201, 138, 193, 186, 9, 91, 122, 31, 246, 90, 28, 139, 57, 3,
76, 124, 193, 11, 98, 37, 173, 61, 104, 57]
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 this 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
Jones, et al. Expires March 7, 2014 [Page 38]
Internet-Draft JWE September 2013
values from this example are detailed in Appendix B. The resulting
Ciphertext is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102]
The resulting Authentication Tag value is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
194, 85]
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
Jones, et al. Expires March 7, 2014 [Page 39]
Internet-Draft JWE September 2013
A.3.12. Validation
This example illustrates the process of creating a JWE with AES Key
Wrap for key encryption and AES GCM for content encryption. These
results can be used to validate JWE decryption implementations for
these algorithms. Also, since both the AES Key Wrap and AES GCM
computations are deterministic, the resulting JWE value will be the
same for all encryptions performed using these inputs. Since the
computation is reproducible, these results can also be used to
validate JWE encryption implementations for these algorithms.
A.4. Example JWE Using JWE JSON Serialization
This section contains an example using the JWE JSON Serialization.
This example demonstrates the capability for encrypting the same
plaintext to multiple recipients.
Two recipients are present in this example. The algorithm and key
used for the first recipient are the same as that used in
Appendix A.2. The algorithm and key used for the second recipient
are the same as that used in Appendix A.3. The resulting JWE
Encrypted Key values are therefore the same; those computations are
not repeated here.
The Plaintext, the Content Encryption Key (CEK), Initialization
Vector, and JWE Protected Header are shared by all recipients (which
must be the case, since the Ciphertext and Authentication Tag are
also shared).
A.4.1. JWE Per-Recipient Unprotected Headers
The first recipient uses the RSAES-PKCS1-V1_5 algorithm to encrypt
the Content Encryption Key (CEK). The second uses AES Key Wrap to
encrypt the CEK. Key ID values are supplied for both keys. The two
per-recipient header values used to represent these algorithms and
Key IDs are:
{"alg":"RSA1_5","kid":"2011-04-29"}
and:
{"alg":"A128KW","kid":"7"}
A.4.2. JWE Protected Header
The Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
algorithm to produce the common JWE Ciphertext and JWE Authentication
Tag values. The JWE Protected Header value representing this is:
Jones, et al. Expires March 7, 2014 [Page 40]
Internet-Draft JWE September 2013
{"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 are detailed in Appendix B. The resulting
Ciphertext is:
Jones, et al. Expires March 7, 2014 [Page 41]
Internet-Draft JWE September 2013
[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):
Jones, et al. Expires March 7, 2014 [Page 42]
Internet-Draft JWE September 2013
{"protected":
"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
"unprotected":
{"jku":"https://server.example.com/keys.jwks"},
"recipients":[
{"header":
{"alg":"RSA1_5"},
"encrypted_key":
"UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-
kFm1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKx
GHZ7PcHALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3
YvkkysZIFNPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPh
cCdZ6XDP0_F8rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPg
wCp6X-nZZd9OHBv-B3oWh2TbqmScqXMR4gp_A"},
{"header":
{"alg":"A128KW"},
"encrypted_key":
"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"}],
"iv":
"AxY8DCtDaGlsbGljb3RoZQ",
"ciphertext":
"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
"tag":
"Mz-VPPyU4RlcuYv1IwIvzw"
}
Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation
This example shows the steps in the AES_128_CBC_HMAC_SHA_256
authenticated encryption computation using the values from the
example in Appendix A.3. As described where this algorithm is
defined in Sections 4.8 and 4.8.3 of JWA, the AES_CBC_HMAC_SHA2
family of algorithms are implemented using Advanced Encryption
Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5
padding to perform the encryption and an HMAC SHA-2 function to
perform the integrity calculation - in this case, HMAC SHA-256.
B.1. Extract MAC_KEY and ENC_KEY from Key
The 256 bit AES_128_CBC_HMAC_SHA_256 key K used in this example is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
44, 207]
Use the first 128 bits of this key as the HMAC SHA-256 key MAC_KEY,
which is:
Jones, et al. Expires March 7, 2014 [Page 43]
Internet-Draft JWE September 2013
[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,
Jones, et al. Expires March 7, 2014 [Page 44]
Internet-Draft JWE September 2013
101]
B.5. Create Input to HMAC Computation
Concatenate the AAD, the Initialization Vector, the Ciphertext, and
the AL value. The result of this concatenation is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
110, 48, 3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111,
116, 104, 101, 40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24,
152, 230, 6, 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215,
104, 143, 112, 56, 102, 0, 0, 0, 0, 0, 0, 1, 152]
B.6. Compute HMAC Value
Compute the HMAC SHA-256 of the concatenated value above. This
result M is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
194, 85, 9, 84, 229, 201, 219, 135, 44, 252, 145, 102, 179, 140, 105,
86, 229, 116]
B.7. Truncate HMAC Value to Create Authentication Tag
Use the first half (128 bits) of the HMAC output M as the
Authentication Tag output T. This truncated value is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
194, 85]
Appendix C. Acknowledgements
Solutions for encrypting JSON content were also explored by JSON
Simple Encryption [JSE] and JavaScript Message Security Format
[I-D.rescorla-jsms], both of which significantly influenced this
draft. This draft attempts to explicitly reuse as many of the
relevant concepts from XML Encryption 1.1
[W3C.CR-xmlenc-core1-20120313] and RFC 5652 [RFC5652] as possible,
while utilizing simple, compact JSON-based data structures.
Special thanks are due to John Bradley and Nat Sakimura for the
discussions that helped inform the content of this specification and
to Eric Rescorla and Joe Hildebrand for allowing the reuse of text
from [I-D.rescorla-jsms] in this document.
Jones, et al. Expires March 7, 2014 [Page 45]
Internet-Draft JWE September 2013
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 ]]
-15
o Clarified that it is an application decision which recipients'
encrypted content must successfully validate for the JWE to be
accepted, addressing issue #35.
o Changes to address editorial issues #34, #164, and #169.
-14
o Clarified that the "protected", "unprotected", "header", "iv",
"tag", and "encrypted_key" parameters are to be omitted in the JWE
JSON Serialization when their values would be empty. Stated that
the "recipients" array must always be present.
-13
o Added an "aad" (Additional Authenticated Data) member for the JWE
JSON Serialization, enabling Additional Authenticated Data to be
supplied that is not double base64url encoded, addressing issue
#29.
-12
o Clarified that the "typ" and "cty" header parameters are used in
an application-specific manner and have no effect upon the JWE
Jones, et al. Expires March 7, 2014 [Page 46]
Internet-Draft JWE September 2013
processing.
o Replaced the MIME types "application/jwe+json" and
"application/jwe" with "application/jose+json" and
"application/jose".
o Stated that recipients MUST either reject JWEs with duplicate
Header Parameter Names or use a JSON parser that returns only the
lexically last duplicate member name.
o Moved the "epk", "apu", and "apv" Header Parameter definitions to
be with the algorithm descriptions that use them.
o Added a Serializations section with parallel treatment of the JWE
Compact Serialization and the JWE JSON Serialization and also
moved the former Implementation Considerations content there.
o Restored use of the term "AEAD".
o Changed terminology from "block encryption" to "content
encryption".
-11
o Added Key Identification section.
o Removed the Encrypted Key value from the AAD computation since it
is already effectively integrity protected by the encryption
process. The AAD value now only contains the representation of
the JWE Encrypted Header.
o For the JWE JSON Serialization, enable header parameter values to
be specified in any of three parameters: the "protected" member
that is integrity protected and shared among all recipients, the
"unprotected" member that is not integrity protected and shared
among all recipients, and the "header" member that is not
integrity protected and specific to a particular recipient. (This
does not affect the JWE Compact Serialization, in which all header
parameter values are in a single integrity protected JWE Header
value.)
o Shortened the names "authentication_tag" to "tag" and
"initialization_vector" to "iv" in the JWE JSON Serialization,
addressing issue #20.
o Removed "apv" (agreement PartyVInfo) since it is no longer used.
Jones, et al. Expires March 7, 2014 [Page 47]
Internet-Draft JWE September 2013
o Removed suggested compact serialization for multiple recipients.
o Changed the MIME type name "application/jwe-js" to
"application/jwe+json", addressing issue #22.
o Tightened the description of the "crit" (critical) header
parameter.
-10
o Changed the JWE processing rules for multiple recipients so that a
single AAD value contains the header parameters and encrypted key
values for all the recipients, enabling AES GCM to be safely used
for multiple recipients.
o Added an appendix suggesting a possible compact serialization for
JWEs with multiple recipients.
-09
o Added JWE JSON Serialization, as specified by
draft-jones-jose-jwe-json-serialization-04.
o Registered "application/jwe-js" MIME type and "JWE-JS" typ header
parameter value.
o Defined that the default action for header parameters that are not
understood is to ignore them unless specifically designated as
"MUST be understood" or included in the new "crit" (critical)
header parameter list. This addressed issue #6.
o Corrected "x5c" description. This addressed issue #12.
o Changed from using the term "byte" to "octet" when referring to 8
bit values.
o Added Key Management Mode definitions to terminology section and
used the defined terms to provide clearer key management
instructions. This addressed issue #5.
o Added text about preventing the recipient from behaving as an
oracle during decryption, especially when using RSAES-PKCS1-V1_5.
o Changed from using the term "Integrity Value" to "Authentication
Tag".
o Changed member name from "integrity_value" to "authentication_tag"
in the JWE JSON Serialization.
Jones, et al. Expires March 7, 2014 [Page 48]
Internet-Draft JWE September 2013
o Removed Initialization Vector from the AAD value since it is
already integrity protected by all of the authenticated encryption
algorithms specified in the JWA specification.
o Replaced "A128CBC+HS256" and "A256CBC+HS512" with "A128CBC-HS256"
and "A256CBC-HS512". The new algorithms perform the same
cryptographic computations as [I-D.mcgrew-aead-aes-cbc-hmac-sha2],
but with the Initialization Vector and Authentication Tag values
remaining separate from the Ciphertext value in the output
representation. Also deleted the header parameters "epu"
(encryption PartyUInfo) and "epv" (encryption PartyVInfo), since
they are no longer used.
-08
o Replaced uses of the term "AEAD" with "Authenticated Encryption",
since the term AEAD in the RFC 5116 sense implied the use of a
particular data representation, rather than just referring to the
class of algorithms that perform authenticated encryption with
associated data.
o Applied editorial improvements suggested by Jeff Hodges and Hannes
Tschofenig. Many of these simplified the terminology used.
o Clarified statements of the form "This header parameter is
OPTIONAL" to "Use of this header parameter is OPTIONAL".
o Added a Header Parameter Usage Location(s) field to the IANA JSON
Web Signature and Encryption Header Parameters registry.
o Added seriesInfo information to Internet Draft references.
-07
o Added a data length prefix to PartyUInfo and PartyVInfo values.
o Updated values for example AES CBC calculations.
o Made several local editorial changes to clean up loose ends left
over from to the decision to only support block encryption methods
providing integrity. One of these changes was to explicitly state
that the "enc" (encryption method) algorithm must be an
Authenticated Encryption algorithm with a specified key length.
-06
o Removed the "int" and "kdf" parameters and defined the new
composite Authenticated Encryption algorithms "A128CBC+HS256" and
Jones, et al. Expires March 7, 2014 [Page 49]
Internet-Draft JWE September 2013
"A256CBC+HS512" to replace the former uses of AES CBC, which
required the use of separate integrity and key derivation
functions.
o Included additional values in the Concat KDF calculation -- the
desired output size and the algorithm value, and optionally
PartyUInfo and PartyVInfo values. Added the optional header
parameters "apu" (agreement PartyUInfo), "apv" (agreement
PartyVInfo), "epu" (encryption PartyUInfo), and "epv" (encryption
PartyVInfo). Updated the KDF examples accordingly.
o Promoted Initialization Vector from being a header parameter to
being a top-level JWE element. This saves approximately 16 bytes
in the compact serialization, which is a significant savings for
some use cases. Promoting the Initialization Vector out of the
header also avoids repeating this shared value in the JSON
serialization.
o Changed "x5c" (X.509 Certificate Chain) representation from being
a single string to being an array of strings, each containing a
single base64 encoded DER certificate value, representing elements
of the certificate chain.
o Added an AES Key Wrap example.
o Reordered the encryption steps so CMK creation is first, when
required.
o Correct statements in examples about which algorithms produce
reproducible results.
-05
o Support both direct encryption using a shared or agreed upon
symmetric key, and the use of a shared or agreed upon symmetric
key to key wrap the CMK.
o Added statement that "StringOrURI values are compared as case-
sensitive strings with no transformations or canonicalizations
applied".
o Updated open issues.
o Indented artwork elements to better distinguish them from the body
text.
-04
Jones, et al. Expires March 7, 2014 [Page 50]
Internet-Draft JWE September 2013
o Refer to the registries as the primary sources of defined values
and then secondarily reference the sections defining the initial
contents of the registries.
o Normatively reference XML Encryption 1.1
[W3C.CR-xmlenc-core1-20120313] for its security considerations.
o Reference draft-jones-jose-jwe-json-serialization instead of
draft-jones-json-web-encryption-json-serialization.
o Described additional open issues.
o Applied editorial suggestions.
-03
o Added the "kdf" (key derivation function) header parameter to
provide crypto agility for key derivation. The default KDF
remains the Concat KDF with the SHA-256 digest function.
o Reordered encryption steps so that the Encoded JWE Header is
always created before it is needed as an input to the
Authenticated Encryption "additional authenticated data"
parameter.
o Added the "cty" (content type) header parameter for declaring type
information about the secured content, as opposed to the "typ"
(type) header parameter, which declares type information about
this object.
o Moved description of how to determine whether a header is for a
JWS or a JWE from the JWT spec to the JWE spec.
o Added complete encryption examples for both Authenticated
Encryption and non-Authenticated Encryption algorithms.
o Added complete key derivation examples.
o Added "Collision Resistant Namespace" to the terminology section.
o Reference ITU.X690.1994 for DER encoding.
o Added Registry Contents sections to populate registry values.
o Numerous editorial improvements.
-02
Jones, et al. Expires March 7, 2014 [Page 51]
Internet-Draft JWE September 2013
o When using Authenticated Encryption algorithms (such as AES GCM),
use the "additional authenticated data" parameter to provide
integrity for the header, encrypted key, and ciphertext and use
the resulting "authentication tag" value as the JWE Authentication
Tag.
o Defined KDF output key sizes.
o Generalized text to allow key agreement to be employed as an
alternative to key wrapping or key encryption.
o Changed compression algorithm from gzip to DEFLATE.
o Clarified that it is an error when a "kid" value is included and
no matching key is found.
o Clarified that JWEs with duplicate Header Parameter Names MUST be
rejected.
o Clarified the relationship between "typ" header parameter values
and MIME types.
o Registered application/jwe MIME type and "JWE" typ header
parameter value.
o Simplified JWK terminology to get replace the "JWK Key Object" and
"JWK Container Object" terms with simply "JSON Web Key (JWK)" and
"JSON Web Key Set (JWK Set)" and to eliminate potential confusion
between single keys and sets of keys. As part of this change, the
Header Parameter Name for a public key value was changed from
"jpk" (JSON Public Key) to "jwk" (JSON Web Key).
o Added suggestion on defining additional header parameters such as
"x5t#S256" in the future for certificate thumbprints using hash
algorithms other than SHA-1.
o Specify RFC 2818 server identity validation, rather than RFC 6125
(paralleling the same decision in the OAuth specs).
o Generalized language to refer to Message Authentication Codes
(MACs) rather than Hash-based Message Authentication Codes (HMACs)
unless in a context specific to HMAC algorithms.
o Reformatted to give each header parameter its own section heading.
-01
Jones, et al. Expires March 7, 2014 [Page 52]
Internet-Draft JWE September 2013
o Added an integrity check for non-Authenticated Encryption
algorithms.
o Added "jpk" and "x5c" header parameters for including JWK public
keys and X.509 certificate chains directly in the header.
o Clarified that this specification is defining the JWE Compact
Serialization. Referenced the new JWE-JS spec, which defines the
JWE JSON Serialization.
o Added text "New header parameters should be introduced sparingly
since an implementation that does not understand a parameter MUST
reject the JWE".
o Clarified that the order of the encryption and decryption steps is
not significant in cases where there are no dependencies between
the inputs and outputs of the steps.
o Made other editorial improvements suggested by JOSE working group
participants.
-00
o Created the initial IETF draft based upon
draft-jones-json-web-encryption-02 with no normative changes.
o Changed terminology to no longer call both digital signatures and
HMACs "signatures".
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
Eric Rescorla
RTFM, Inc.
Email: ekr@rtfm.com
Jones, et al. Expires March 7, 2014 [Page 53]
Internet-Draft JWE September 2013
Joe Hildebrand
Cisco Systems, Inc.
Email: jhildebr@cisco.com
Jones, et al. Expires March 7, 2014 [Page 54]
