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Keywords: JavaScript Object Notation, JSON, JSON Object Signing and Encryption, JOSE, JSON Web Signature, JWS, JSON Web Encryption, JWE, JSON Web Key, JWK, JSON Web Algorithms, JWA
Internet Engineering Task Force (IETF) M. Jones
Request for Comments: 7516 Microsoft
Category: Standards Track J. Hildebrand
ISSN: 2070-1721 Cisco
May 2015
JSON Web Encryption (JWE)
Abstract
JSON Web Encryption (JWE) represents encrypted content using
JSON-based data structures. Cryptographic algorithms and identifiers
for use with this specification are described in the separate JSON
Web Algorithms (JWA) specification and IANA registries defined by
that specification. Related digital signature and Message
Authentication Code (MAC) capabilities are described in the separate
JSON Web Signature (JWS) specification.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7516.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Jones & Hildebrand Standards Track [Page 1]
RFC 7516 JSON Web Encryption (JWE) May 2015
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. JSON Web Encryption (JWE) Overview . . . . . . . . . . . . . 8
3.1. JWE Compact Serialization Overview . . . . . . . . . . . 8
3.2. JWE JSON Serialization Overview . . . . . . . . . . . . . 9
3.3. Example JWE . . . . . . . . . . . . . . . . . . . . . . . 10
4. JOSE Header . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Registered Header Parameter Names . . . . . . . . . . . . 11
4.1.1. "alg" (Algorithm) Header Parameter . . . . . . . . . 12
4.1.2. "enc" (Encryption Algorithm) Header Parameter . . . . 12
4.1.3. "zip" (Compression Algorithm) Header Parameter . . . 12
4.1.4. "jku" (JWK Set URL) Header Parameter . . . . . . . . 13
4.1.5. "jwk" (JSON Web Key) Header Parameter . . . . . . . . 13
4.1.6. "kid" (Key ID) Header Parameter . . . . . . . . . . . 13
4.1.7. "x5u" (X.509 URL) Header Parameter . . . . . . . . . 13
4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter . . 13
4.1.9. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header
Parameter . . . . . . . . . . . . . . . . . . . . . . 14
4.1.10. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint)
Header Parameter . . . . . . . . . . . . . . . . . . 14
4.1.11. "typ" (Type) Header Parameter . . . . . . . . . . . . 14
4.1.12. "cty" (Content Type) Header Parameter . . . . . . . . 14
4.1.13. "crit" (Critical) Header Parameter . . . . . . . . . 14
4.2. Public Header Parameter Names . . . . . . . . . . . . . . 14
4.3. Private Header Parameter Names . . . . . . . . . . . . . 15
5. Producing and Consuming JWEs . . . . . . . . . . . . . . . . 15
5.1. Message Encryption . . . . . . . . . . . . . . . . . . . 15
5.2. Message Decryption . . . . . . . . . . . . . . . . . . . 17
5.3. String Comparison Rules . . . . . . . . . . . . . . . . . 20
6. Key Identification . . . . . . . . . . . . . . . . . . . . . 20
7. Serializations . . . . . . . . . . . . . . . . . . . . . . . 20
7.1. JWE Compact Serialization . . . . . . . . . . . . . . . . 20
7.2. JWE JSON Serialization . . . . . . . . . . . . . . . . . 20
7.2.1. General JWE JSON Serialization Syntax . . . . . . . . 21
7.2.2. Flattened JWE JSON Serialization Syntax . . . . . . . 23
8. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . 24
9. Distinguishing between JWS and JWE Objects . . . . . . . . . 24
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
10.1. JSON Web Signature and Encryption Header Parameters
Registration . . . . . . . . . . . . . . . . . . . . . . 25
10.1.1. Registry Contents . . . . . . . . . . . . . . . . . 25
11. Security Considerations . . . . . . . . . . . . . . . . . . . 27
11.1. Key Entropy and Random Values . . . . . . . . . . . . . 27
11.2. Key Protection . . . . . . . . . . . . . . . . . . . . . 27
11.3. Using Matching Algorithm Strengths . . . . . . . . . . . 28
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11.4. Adaptive Chosen-Ciphertext Attacks . . . . . . . . . . . 28
11.5. Timing Attacks . . . . . . . . . . . . . . . . . . . . . 28
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
12.1. Normative References . . . . . . . . . . . . . . . . . . 29
12.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. JWE Examples . . . . . . . . . . . . . . . . . . . . 32
A.1. Example JWE using RSAES-OAEP and AES GCM . . . . . . . . 32
A.1.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . 32
A.1.2. Content Encryption Key (CEK) . . . . . . . . . . . . 32
A.1.3. Key Encryption . . . . . . . . . . . . . . . . . . . 33
A.1.4. Initialization Vector . . . . . . . . . . . . . . . . 34
A.1.5. Additional Authenticated Data . . . . . . . . . . . . 35
A.1.6. Content Encryption . . . . . . . . . . . . . . . . . 35
A.1.7. Complete Representation . . . . . . . . . . . . . . . 36
A.1.8. Validation . . . . . . . . . . . . . . . . . . . . . 36
A.2. Example JWE using RSAES-PKCS1-v1_5 and
AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . 36
A.2.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . 37
A.2.2. Content Encryption Key (CEK) . . . . . . . . . . . . 37
A.2.3. Key Encryption . . . . . . . . . . . . . . . . . . . 38
A.2.4. Initialization Vector . . . . . . . . . . . . . . . . 39
A.2.5. Additional Authenticated Data . . . . . . . . . . . . 40
A.2.6. Content Encryption . . . . . . . . . . . . . . . . . 40
A.2.7. Complete Representation . . . . . . . . . . . . . . . 40
A.2.8. Validation . . . . . . . . . . . . . . . . . . . . . 41
A.3. Example JWE Using AES Key Wrap and
AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . 41
A.3.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . 41
A.3.2. Content Encryption Key (CEK) . . . . . . . . . . . . 42
A.3.3. Key Encryption . . . . . . . . . . . . . . . . . . . 42
A.3.4. Initialization Vector . . . . . . . . . . . . . . . . 42
A.3.5. Additional Authenticated Data . . . . . . . . . . . . 43
A.3.6. Content Encryption . . . . . . . . . . . . . . . . . 43
A.3.7. Complete Representation . . . . . . . . . . . . . . . 43
A.3.8. Validation . . . . . . . . . . . . . . . . . . . . . 44
A.4. Example JWE Using General JWE JSON Serialization . . . . 44
A.4.1. JWE Per-Recipient Unprotected Headers . . . . . . . . 45
A.4.2. JWE Protected Header . . . . . . . . . . . . . . . . 45
A.4.3. JWE Shared Unprotected Header . . . . . . . . . . . . 45
A.4.4. Complete JOSE Header Values . . . . . . . . . . . . . 45
A.4.5. Additional Authenticated Data . . . . . . . . . . . . 46
A.4.6. Content Encryption . . . . . . . . . . . . . . . . . 46
A.4.7. Complete JWE JSON Serialization Representation . . . 47
A.5. Example JWE Using Flattened JWE JSON Serialization . . . 47
Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation . . . . 48
B.1. Extract MAC_KEY and ENC_KEY from Key . . . . . . . . . . 48
B.2. Encrypt Plaintext to Create Ciphertext . . . . . . . . . 49
B.3. 64-Bit Big-Endian Representation of AAD Length . . . . . 49
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RFC 7516 JSON Web Encryption (JWE) May 2015
B.4. Initialization Vector Value . . . . . . . . . . . . . . . 49
B.5. Create Input to HMAC Computation . . . . . . . . . . . . 50
B.6. Compute HMAC Value . . . . . . . . . . . . . . . . . . . 50
B.7. Truncate HMAC Value to Create Authentication Tag . . . . 50
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction
JSON Web Encryption (JWE) represents encrypted content using JSON-
based data structures [RFC7159]. The JWE cryptographic mechanisms
encrypt and provide integrity protection for an arbitrary sequence of
octets.
Two closely related serializations for JWEs are defined. The JWE
Compact Serialization is a compact, URL-safe representation intended
for space constrained environments such as HTTP Authorization headers
and URI query parameters. The JWE JSON Serialization represents JWEs
as JSON objects and enables the same content to be encrypted to
multiple parties. Both share the same cryptographic underpinnings.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate JSON Web Algorithms (JWA)
[JWA] specification and IANA registries defined by that
specification. Related digital signature and MAC capabilities are
described in the separate JSON Web Signature (JWS) [JWS]
specification.
Names defined by this specification are short because a core goal is
for the resulting representations to be compact.
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
"Key words for use in RFCs to Indicate Requirement Levels" [RFC2119].
The interpretation should only be applied when the terms appear in
all capital letters.
BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per
Section 2 of [JWS].
UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation
of STRING, where STRING is a sequence of zero or more Unicode
[UNICODE] characters.
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RFC 7516 JSON Web Encryption (JWE) May 2015
ASCII(STRING) denotes the octets of the ASCII [RFC20] representation
of STRING, where STRING is a sequence of zero or more ASCII
characters.
The concatenation of two values A and B is denoted as A || B.
2. Terminology
The terms "JSON Web Signature (JWS)", "Base64url Encoding",
"Collision-Resistant Name", "Header Parameter", "JOSE Header", and
"StringOrURI" are defined by the JWS specification [JWS].
The terms "Ciphertext", "Digital Signature", "Initialization Vector
(IV)", "Message Authentication Code (MAC)", and "Plaintext" are
defined by the "Internet Security Glossary, Version 2" [RFC4949].
These terms are defined by this specification:
JSON Web Encryption (JWE)
A data structure representing an encrypted and integrity-protected
message.
Authenticated Encryption with Associated Data (AEAD)
An AEAD algorithm is one that encrypts the plaintext, allows
Additional Authenticated Data to be specified, and provides an
integrated content integrity check over the ciphertext and
Additional Authenticated Data. AEAD algorithms accept two inputs,
the plaintext and the Additional Authenticated Data value, and
produce two outputs, the ciphertext and the Authentication Tag
value. AES Galois/Counter Mode (GCM) is one such algorithm.
Additional Authenticated Data (AAD)
An input to an AEAD operation that is integrity protected but not
encrypted.
Authentication Tag
An output of an AEAD operation that ensures the integrity of the
ciphertext and the Additional Authenticated Data. Note that some
algorithms may not use an Authentication Tag, in which case this
value is the empty octet sequence.
Content Encryption Key (CEK)
A symmetric key for the AEAD algorithm used to encrypt the
plaintext to produce the ciphertext and the Authentication Tag.
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RFC 7516 JSON Web Encryption (JWE) May 2015
JWE Encrypted Key
Encrypted Content Encryption Key value. Note that for some
algorithms, the JWE Encrypted Key value is specified as being the
empty octet sequence.
JWE Initialization Vector
Initialization Vector value used when encrypting the plaintext.
Note that some algorithms may not use an Initialization Vector, in
which case this value is the empty octet sequence.
JWE AAD
Additional value to be integrity protected by the authenticated
encryption operation. This can only be present when using the JWE
JSON Serialization. (Note that this can also be achieved when
using either the JWE Compact Serialization or the JWE JSON
Serialization by including the AAD value as an integrity-protected
Header Parameter value, but at the cost of the value being double
base64url encoded.)
JWE Ciphertext
Ciphertext value resulting from authenticated encryption of the
plaintext with Additional Authenticated Data.
JWE Authentication Tag
Authentication Tag value resulting from authenticated encryption
of the plaintext with Additional Authenticated Data.
JWE Protected Header
JSON object that contains the Header Parameters that are integrity
protected by the authenticated encryption operation. These
parameters apply to all recipients of the JWE. For the JWE
Compact Serialization, this comprises the entire JOSE Header. For
the JWE JSON Serialization, this is one component of the JOSE
Header.
JWE Shared Unprotected Header
JSON object that contains the Header Parameters that apply to all
recipients of the JWE that are not integrity protected. This can
only be present when using the JWE JSON Serialization.
JWE Per-Recipient Unprotected Header
JSON object that contains Header Parameters that apply to a single
recipient of the JWE. These Header Parameter values are not
integrity protected. This can only be present when using the JWE
JSON Serialization.
JWE Compact Serialization
A representation of the JWE as a compact, URL-safe string.
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RFC 7516 JSON Web Encryption (JWE) May 2015
JWE JSON Serialization
A representation of the JWE as a JSON object. The JWE JSON
Serialization enables the same content to be encrypted to multiple
parties. This representation is neither optimized for compactness
nor URL safe.
Key Management Mode
A method of determining the Content Encryption Key value to use.
Each algorithm used for determining the CEK value uses a specific
Key Management Mode. Key Management Modes employed by this
specification are Key Encryption, Key Wrapping, Direct Key
Agreement, Key Agreement with Key Wrapping, and Direct Encryption.
Key Encryption
A Key Management Mode in which the CEK value is encrypted to the
intended recipient using an asymmetric encryption algorithm.
Key Wrapping
A Key Management Mode in which the CEK value is encrypted to the
intended recipient using a symmetric key wrapping algorithm.
Direct Key Agreement
A Key Management Mode in which a key agreement algorithm is used
to agree upon the CEK value.
Key Agreement with Key Wrapping
A Key Management Mode in which a key agreement algorithm is used
to agree upon a symmetric key used to encrypt the CEK value to the
intended recipient using a symmetric key wrapping algorithm.
Direct Encryption
A Key Management Mode in which the CEK value used is the secret
symmetric key value shared between the parties.
Jones & Hildebrand Standards Track [Page 7]
RFC 7516 JSON Web Encryption (JWE) May 2015
3. JSON Web Encryption (JWE) Overview
JWE represents encrypted content using JSON data structures and
base64url encoding. These JSON data structures MAY contain
whitespace and/or line breaks before or after any JSON values or
structural characters, in accordance with Section 2 of RFC 7159
[RFC7159]. A JWE represents these logical values (each of which is
defined in Section 2):
o JOSE Header
o JWE Encrypted Key
o JWE Initialization Vector
o JWE AAD
o JWE Ciphertext
o JWE Authentication Tag
For a JWE, the JOSE Header members are the union of the members of
these values (each of which is defined in Section 2):
o JWE Protected Header
o JWE Shared Unprotected Header
o JWE Per-Recipient Unprotected Header
JWE utilizes authenticated encryption to ensure the confidentiality
and integrity of the plaintext and the integrity of the JWE Protected
Header and the JWE AAD.
This document defines two serializations for JWEs: a compact, URL-
safe serialization called the JWE Compact Serialization and a JSON
serialization called the JWE JSON Serialization. In both
serializations, the JWE Protected Header, JWE Encrypted Key, JWE
Initialization Vector, JWE Ciphertext, and JWE Authentication Tag are
base64url encoded, since JSON lacks a way to directly represent
arbitrary octet sequences. When present, the JWE AAD is also
base64url encoded.
3.1. JWE Compact Serialization Overview
In the JWE Compact Serialization, no JWE Shared Unprotected Header or
JWE Per-Recipient Unprotected Header are used. In this case, the
JOSE Header and the JWE Protected Header are the same.
Jones & Hildebrand Standards Track [Page 8]
RFC 7516 JSON Web Encryption (JWE) May 2015
In the JWE Compact Serialization, a JWE is represented as the
concatenation:
BASE64URL(UTF8(JWE Protected Header)) || '.' ||
BASE64URL(JWE Encrypted Key) || '.' ||
BASE64URL(JWE Initialization Vector) || '.' ||
BASE64URL(JWE Ciphertext) || '.' ||
BASE64URL(JWE Authentication Tag)
See Section 7.1 for more information about the JWE Compact
Serialization.
3.2. JWE JSON Serialization Overview
In the JWE JSON Serialization, one or more of the JWE Protected
Header, JWE Shared Unprotected Header, and JWE Per-Recipient
Unprotected Header MUST be present. In this case, the members of the
JOSE Header are the union of the members of the JWE Protected Header,
JWE Shared Unprotected Header, and JWE Per-Recipient Unprotected
Header values that are present.
In the JWE JSON Serialization, a JWE is represented as a JSON object
containing some or all of these eight members:
"protected", with the value BASE64URL(UTF8(JWE Protected Header))
"unprotected", with the value JWE Shared Unprotected Header
"header", with the value JWE Per-Recipient Unprotected Header
"encrypted_key", with the value BASE64URL(JWE Encrypted Key)
"iv", with the value BASE64URL(JWE Initialization Vector)
"ciphertext", with the value BASE64URL(JWE Ciphertext)
"tag", with the value BASE64URL(JWE Authentication Tag)
"aad", with the value BASE64URL(JWE AAD)
The six base64url-encoded result strings and the two unprotected JSON
object values are represented as members within a JSON object. The
inclusion of some of these values is OPTIONAL. The JWE JSON
Serialization can also encrypt the plaintext to multiple recipients.
See Section 7.2 for more information about the JWE JSON
Serialization.
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RFC 7516 JSON Web Encryption (JWE) May 2015
3.3. Example JWE
This example encrypts the plaintext "The true sign of intelligence is
not knowledge but imagination." to the recipient.
The following example JWE Protected Header declares that:
o The Content Encryption Key is encrypted to the recipient using the
RSAES-OAEP [RFC3447] algorithm to produce the JWE Encrypted Key.
o Authenticated encryption is performed on the plaintext using the
AES GCM [AES] [NIST.800-38D] algorithm with a 256-bit key to
produce the ciphertext and the Authentication Tag.
{"alg":"RSA-OAEP","enc":"A256GCM"}
Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
Header)) gives this value:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
The remaining steps to finish creating this JWE are:
o Generate a random Content Encryption Key (CEK).
o Encrypt the CEK with the recipient's public key using the RSAES-
OAEP algorithm to produce the JWE Encrypted Key.
o Base64url-encode the JWE Encrypted Key.
o Generate a random JWE Initialization Vector.
o Base64url-encode the JWE Initialization Vector.
o Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))).
o Perform authenticated encryption on the plaintext with the AES GCM
algorithm using the CEK as the encryption key, the JWE
Initialization Vector, and the Additional Authenticated Data
value, requesting a 128-bit Authentication Tag output.
o Base64url-encode the ciphertext.
o Base64url-encode the Authentication Tag.
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RFC 7516 JSON Web Encryption (JWE) May 2015
o Assemble the final representation: The Compact Serialization of
this result is the string BASE64URL(UTF8(JWE Protected Header)) ||
'.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE
Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.'
|| BASE64URL(JWE Authentication Tag).
The final result in this example (with line breaks for display
purposes only) is:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
6UklfCpIMfIjf7iGdXKHzg.
48V1_ALb6US04U3b.
5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
SdiwkIr3ajwQzaBtQD_A.
XFBoMYUZodetZdvTiFvSkQ
See Appendix A.1 for the complete details of computing this JWE. See
Appendix A for additional examples, including examples using the JWE
JSON Serialization in Sections A.4 and A.5.
4. JOSE Header
For a JWE, the members of the JSON object(s) representing the JOSE
Header describe the encryption applied to the plaintext and
optionally additional properties of the JWE. The Header Parameter
names within the JOSE Header MUST be unique, just as described in
Section 4 of [JWS]. The rules about handling Header Parameters that
are not understood by the implementation are also the same. The
classes of Header Parameter names are likewise the same.
4.1. Registered Header Parameter Names
The following Header Parameter names for use in JWEs are registered
in the IANA "JSON Web Signature and Encryption Header Parameters"
registry established by [JWS], with meanings as defined below.
As indicated by the common registry, JWSs and JWEs share a common
Header Parameter space; when a parameter is used by both
specifications, its usage must be compatible between the
specifications.
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RFC 7516 JSON Web Encryption (JWE) May 2015
4.1.1. "alg" (Algorithm) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "alg" Header Parameter defined in Section 4.1.1 of [JWS], except
that the Header Parameter identifies the cryptographic algorithm used
to encrypt or determine the value of the CEK. The encrypted content
is not usable if the "alg" value does not represent a supported
algorithm, or if the recipient does not have a key that can be used
with that algorithm.
A list of defined "alg" values for this use can be found in the IANA
"JSON Web Signature and Encryption Algorithms" registry established
by [JWA]; the initial contents of this registry are the values
defined in Section 4.1 of [JWA].
4.1.2. "enc" (Encryption Algorithm) Header Parameter
The "enc" (encryption algorithm) Header Parameter identifies the
content encryption algorithm used to perform authenticated encryption
on the plaintext to produce the ciphertext and the Authentication
Tag. This algorithm MUST be an AEAD algorithm with a specified key
length. The encrypted content is not usable if the "enc" value does
not represent a supported algorithm. "enc" values should either be
registered in the IANA "JSON Web Signature and Encryption Algorithms"
registry established by [JWA] or be a value that contains a
Collision-Resistant Name. The "enc" value is a case-sensitive ASCII
string containing a StringOrURI value. This Header Parameter MUST be
present and MUST be understood and processed by implementations.
A list of defined "enc" values for this use can be found in the IANA
"JSON Web Signature and Encryption Algorithms" registry established
by [JWA]; the initial contents of this registry are the values
defined in Section 5.1 of [JWA].
4.1.3. "zip" (Compression Algorithm) Header Parameter
The "zip" (compression algorithm) applied to the plaintext before
encryption, if any. The "zip" value defined by this specification
is:
o "DEF" - Compression with the DEFLATE [RFC1951] algorithm
Other values MAY be used. Compression algorithm values can be
registered in the IANA "JSON Web Encryption Compression Algorithms"
registry established by [JWA]. The "zip" value is a case-sensitive
string. If no "zip" parameter is present, no compression is applied
to the plaintext before encryption. When used, this Header Parameter
MUST be integrity protected; therefore, it MUST occur only within the
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RFC 7516 JSON Web Encryption (JWE) May 2015
JWE Protected Header. Use of this Header Parameter is OPTIONAL.
This Header Parameter MUST be understood and processed by
implementations.
4.1.4. "jku" (JWK Set URL) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "jku" Header Parameter defined in Section 4.1.2 of [JWS], except
that the JWK Set resource contains the public key to which the JWE
was encrypted; this can be used to determine the private key needed
to decrypt the JWE.
4.1.5. "jwk" (JSON Web Key) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "jwk" Header Parameter defined in Section 4.1.3 of [JWS], except
that the key is the public key to which the JWE was encrypted; this
can be used to determine the private key needed to decrypt the JWE.
4.1.6. "kid" (Key ID) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "kid" Header Parameter defined in Section 4.1.4 of [JWS], except
that the key hint references the public key to which the JWE was
encrypted; this can be used to determine the private key needed to
decrypt the JWE. This parameter allows originators to explicitly
signal a change of key to JWE recipients.
4.1.7. "x5u" (X.509 URL) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "x5u" Header Parameter defined in Section 4.1.5 of [JWS], except
that the X.509 public key certificate or certificate chain [RFC5280]
contains the public key to which the JWE was encrypted; this can be
used to determine the private key needed to decrypt the JWE.
4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "x5c" Header Parameter defined in Section 4.1.6 of [JWS], except
that the X.509 public key certificate or certificate chain [RFC5280]
contains the public key to which the JWE was encrypted; this can be
used to determine the private key needed to decrypt the JWE.
See Appendix B of [JWS] for an example "x5c" value.
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4.1.9. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "x5t" Header Parameter defined in Section 4.1.7 of [JWS], except
that the certificate referenced by the thumbprint contains the public
key to which the JWE was encrypted; this can be used to determine the
private key needed to decrypt the JWE. Note that certificate
thumbprints are also sometimes known as certificate fingerprints.
4.1.10. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header
Parameter
This parameter has the same meaning, syntax, and processing rules as
the "x5t#S256" Header Parameter defined in Section 4.1.8 of [JWS],
except that the certificate referenced by the thumbprint contains the
public key to which the JWE was encrypted; this can be used to
determine the private key needed to decrypt the JWE. Note that
certificate thumbprints are also sometimes known as certificate
fingerprints.
4.1.11. "typ" (Type) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "typ" Header Parameter defined in Section 4.1.9 of [JWS], except
that the type is that of this complete JWE.
4.1.12. "cty" (Content Type) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "cty" Header Parameter defined in Section 4.1.10 of [JWS], except
that the type is that of the secured content (the plaintext).
4.1.13. "crit" (Critical) Header Parameter
This parameter has the same meaning, syntax, and processing rules as
the "crit" Header Parameter defined in Section 4.1.11 of [JWS],
except that Header Parameters for a JWE are being referred to, rather
than Header Parameters for a JWS.
4.2. Public Header Parameter Names
Additional Header Parameter names can be defined by those using JWEs.
However, in order to prevent collisions, any new Header Parameter
name should either be registered in the IANA "JSON Web Signature and
Encryption Header Parameters" registry established by [JWS] or be a
Public Name: a value that contains a Collision-Resistant Name. In
each case, the definer of the name or value needs to take reasonable
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precautions to make sure they are in control of the part of the
namespace they use to define the Header Parameter name.
New Header Parameters should be introduced sparingly, as they can
result in non-interoperable JWEs.
4.3. Private Header Parameter Names
A producer and consumer of a JWE may agree to use Header Parameter
names that are Private Names: names that are not Registered Header
Parameter names (Section 4.1) or Public Header Parameter names
(Section 4.2). Unlike Public Header Parameter names, Private Header
Parameter names are subject to collision and should be used with
caution.
5. Producing and Consuming JWEs
5.1. Message Encryption
The message encryption process is as follows. The order of the steps
is not significant in cases where there are no dependencies between
the inputs and outputs of the steps.
1. Determine the Key Management Mode employed by the algorithm used
to determine the Content Encryption Key value. (This is the
algorithm recorded in the "alg" (algorithm) Header Parameter of
the resulting JWE.)
2. When Key Wrapping, Key Encryption, or Key Agreement with Key
Wrapping are employed, generate a random CEK value. See RFC
4086 [RFC4086] for considerations on generating random values.
The CEK MUST have a length equal to that required for the
content encryption algorithm.
3. When Direct Key Agreement or Key Agreement with Key Wrapping are
employed, use the key agreement algorithm to compute the value
of the agreed upon key. When Direct Key Agreement is employed,
let the CEK be the agreed upon key. When Key Agreement with Key
Wrapping is employed, the agreed upon key will be used to wrap
the CEK.
4. When Key Wrapping, Key Encryption, or Key Agreement with Key
Wrapping are employed, encrypt the CEK to the recipient and let
the result be the JWE Encrypted Key.
5. When Direct Key Agreement or Direct Encryption are employed, let
the JWE Encrypted Key be the empty octet sequence.
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6. When Direct Encryption is employed, let the CEK be the shared
symmetric key.
7. Compute the encoded key value BASE64URL(JWE Encrypted Key).
8. If the JWE JSON Serialization is being used, repeat this process
(steps 1-7) for each recipient.
9. Generate a random JWE Initialization Vector of the correct size
for the content encryption algorithm (if required for the
algorithm); otherwise, let the JWE Initialization Vector be the
empty octet sequence.
10. Compute the encoded Initialization Vector value BASE64URL(JWE
Initialization Vector).
11. If a "zip" parameter was included, compress the plaintext using
the specified compression algorithm and let M be the octet
sequence representing the compressed plaintext; otherwise, let M
be the octet sequence representing the plaintext.
12. Create the JSON object(s) containing the desired set of Header
Parameters, which together comprise the JOSE Header: one or more
of the JWE Protected Header, the JWE Shared Unprotected Header,
and the JWE Per-Recipient Unprotected Header.
13. Compute the Encoded Protected Header value BASE64URL(UTF8(JWE
Protected Header)). If the JWE Protected Header is not present
(which can only happen when using the JWE JSON Serialization and
no "protected" member is present), let this value be the empty
string.
14. Let the Additional Authenticated Data encryption parameter be
ASCII(Encoded Protected Header). However, if a JWE AAD value is
present (which can only be the case when using the JWE JSON
Serialization), instead let the Additional Authenticated Data
encryption parameter be ASCII(Encoded Protected Header || '.' ||
BASE64URL(JWE AAD)).
15. Encrypt M using the CEK, the JWE Initialization Vector, and the
Additional Authenticated Data value using the specified content
encryption algorithm to create the JWE Ciphertext value and the
JWE Authentication Tag (which is the Authentication Tag output
from the encryption operation).
16. Compute the encoded ciphertext value BASE64URL(JWE Ciphertext).
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17. Compute the encoded Authentication Tag value BASE64URL(JWE
Authentication Tag).
18. If a JWE AAD value is present, compute the encoded AAD value
BASE64URL(JWE AAD).
19. Create the desired serialized output. The Compact Serialization
of this result is the string BASE64URL(UTF8(JWE Protected
Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' ||
BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE
Ciphertext) || '.' || BASE64URL(JWE Authentication Tag). The
JWE JSON Serialization is described in Section 7.2.
5.2. Message Decryption
The message decryption process is the reverse of the encryption
process. The order of the steps is not significant in cases where
there are no dependencies between the inputs and outputs of the
steps. If any of these steps fail, the encrypted content cannot be
validated.
When there are multiple recipients, it is an application decision
which of the recipients' encrypted content must successfully validate
for the JWE to be accepted. In some cases, encrypted content for all
recipients must successfully validate or the JWE will be considered
invalid. In other cases, only the encrypted content for a single
recipient needs to be successfully validated. However, in all cases,
the encrypted content for at least one recipient MUST successfully
validate or the JWE MUST be considered invalid.
1. Parse the JWE representation to extract the serialized values
for the components of the JWE. When using the JWE Compact
Serialization, these components are the base64url-encoded
representations of the JWE Protected Header, the JWE Encrypted
Key, the JWE Initialization Vector, the JWE Ciphertext, and the
JWE Authentication Tag, and when using the JWE JSON
Serialization, these components also include the base64url-
encoded representation of the JWE AAD and the unencoded JWE
Shared Unprotected Header and JWE Per-Recipient Unprotected
Header values. When using the JWE Compact Serialization, the
JWE Protected Header, the JWE Encrypted Key, the JWE
Initialization Vector, the JWE Ciphertext, and the JWE
Authentication Tag are represented as base64url-encoded values
in that order, with each value being separated from the next by
a single period ('.') character, resulting in exactly four
delimiting period characters being used. The JWE JSON
Serialization is described in Section 7.2.
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2. Base64url decode the encoded representations of the JWE
Protected Header, the JWE Encrypted Key, the JWE Initialization
Vector, the JWE Ciphertext, the JWE Authentication Tag, and the
JWE AAD, following the restriction that no line breaks,
whitespace, or other additional characters have been used.
3. Verify that the octet sequence resulting from decoding the
encoded JWE Protected Header is a UTF-8-encoded representation
of a completely valid JSON object conforming to RFC 7159
[RFC7159]; let the JWE Protected Header be this JSON object.
4. If using the JWE Compact Serialization, let the JOSE Header be
the JWE Protected Header. Otherwise, when using the JWE JSON
Serialization, let the JOSE Header be the union of the members
of the JWE Protected Header, the JWE Shared Unprotected Header
and the corresponding JWE Per-Recipient Unprotected Header, all
of which must be completely valid JSON objects. During this
step, verify that the resulting JOSE Header does not contain
duplicate Header Parameter names. When using the JWE JSON
Serialization, this restriction includes that the same Header
Parameter name also MUST NOT occur in distinct JSON object
values that together comprise the JOSE Header.
5. Verify that the implementation understands and can process all
fields that it is required to support, whether required by this
specification, by the algorithms being used, or by the "crit"
Header Parameter value, and that the values of those parameters
are also understood and supported.
6. Determine the Key Management Mode employed by the algorithm
specified by the "alg" (algorithm) Header Parameter.
7. Verify that the JWE uses a key known to the recipient.
8. When Direct Key Agreement or Key Agreement with Key Wrapping are
employed, use the key agreement algorithm to compute the value
of the agreed upon key. When Direct Key Agreement is employed,
let the CEK be the agreed upon key. When Key Agreement with Key
Wrapping is employed, the agreed upon key will be used to
decrypt the JWE Encrypted Key.
9. When Key Wrapping, Key Encryption, or Key Agreement with Key
Wrapping are employed, decrypt the JWE Encrypted Key to produce
the CEK. The CEK MUST have a length equal to that required for
the content encryption algorithm. Note that when there are
multiple recipients, each recipient will only be able to decrypt
JWE Encrypted Key values that were encrypted to a key in that
recipient's possession. It is therefore normal to only be able
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to decrypt one of the per-recipient JWE Encrypted Key values to
obtain the CEK value. Also, see Section 11.5 for security
considerations on mitigating timing attacks.
10. When Direct Key Agreement or Direct Encryption are employed,
verify that the JWE Encrypted Key value is an empty octet
sequence.
11. When Direct Encryption is employed, let the CEK be the shared
symmetric key.
12. Record whether the CEK could be successfully determined for this
recipient or not.
13. If the JWE JSON Serialization is being used, repeat this process
(steps 4-12) for each recipient contained in the representation.
14. Compute the Encoded Protected Header value BASE64URL(UTF8(JWE
Protected Header)). If the JWE Protected Header is not present
(which can only happen when using the JWE JSON Serialization and
no "protected" member is present), let this value be the empty
string.
15. Let the Additional Authenticated Data encryption parameter be
ASCII(Encoded Protected Header). However, if a JWE AAD value is
present (which can only be the case when using the JWE JSON
Serialization), instead let the Additional Authenticated Data
encryption parameter be ASCII(Encoded Protected Header || '.' ||
BASE64URL(JWE AAD)).
16. Decrypt the JWE Ciphertext using the CEK, the JWE Initialization
Vector, the Additional Authenticated Data value, and the JWE
Authentication Tag (which is the Authentication Tag input to the
calculation) using the specified content encryption algorithm,
returning the decrypted plaintext and validating the JWE
Authentication Tag in the manner specified for the algorithm,
rejecting the input without emitting any decrypted output if the
JWE Authentication Tag is incorrect.
17. If a "zip" parameter was included, uncompress the decrypted
plaintext using the specified compression algorithm.
18. If there was no recipient for which all of the decryption steps
succeeded, then the JWE MUST be considered invalid. Otherwise,
output the plaintext. In the JWE JSON Serialization case, also
return a result to the application indicating for which of the
recipients the decryption succeeded and failed.
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Finally, note that it is an application decision which algorithms may
be used in a given context. Even if a JWE can be successfully
decrypted, unless the algorithms used in the JWE are acceptable to
the application, it SHOULD consider the JWE to be invalid.
5.3. String Comparison Rules
The string comparison rules for this specification are the same as
those defined in Section 5.3 of [JWS].
6. Key Identification
The key identification methods for this specification are the same as
those defined in Section 6 of [JWS], except that the key being
identified is the public key to which the JWE was encrypted.
7. Serializations
JWEs use one of two serializations: the JWE Compact Serialization or
the JWE JSON Serialization. Applications using this specification
need to specify what serialization and serialization features are
used for that application. For instance, applications might specify
that only the JWE JSON Serialization is used, that only JWE JSON
Serialization support for a single recipient is used, or that support
for multiple recipients is used. JWE implementations only need to
implement the features needed for the applications they are designed
to support.
7.1. JWE Compact Serialization
The JWE Compact Serialization represents encrypted content as a
compact, URL-safe string. This string is:
BASE64URL(UTF8(JWE Protected Header)) || '.' ||
BASE64URL(JWE Encrypted Key) || '.' ||
BASE64URL(JWE Initialization Vector) || '.' ||
BASE64URL(JWE Ciphertext) || '.' ||
BASE64URL(JWE Authentication Tag)
Only one recipient is supported by the JWE Compact Serialization and
it provides no syntax to represent JWE Shared Unprotected Header, JWE
Per-Recipient Unprotected Header, or JWE AAD values.
7.2. JWE JSON Serialization
The JWE JSON Serialization represents encrypted content as a JSON
object. This representation is neither optimized for compactness nor
URL safe.
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Two closely related syntaxes are defined for the JWE JSON
Serialization: a fully general syntax, with which content can be
encrypted to more than one recipient, and a flattened syntax, which
is optimized for the single-recipient case.
7.2.1. General JWE JSON Serialization Syntax
The following members are defined for use in top-level JSON objects
used for the fully general JWE JSON Serialization syntax:
protected
The "protected" member MUST be present and contain the value
BASE64URL(UTF8(JWE Protected Header)) when the JWE Protected
Header value is non-empty; otherwise, it MUST be absent. These
Header Parameter values are integrity protected.
unprotected
The "unprotected" member MUST be present and contain the value JWE
Shared Unprotected Header when the JWE Shared Unprotected Header
value is non-empty; otherwise, it MUST be absent. This value is
represented as an unencoded JSON object, rather than as a string.
These Header Parameter values are not integrity protected.
iv
The "iv" member MUST be present and contain the value
BASE64URL(JWE Initialization Vector) when the JWE Initialization
Vector value is non-empty; otherwise, it MUST be absent.
aad
The "aad" member MUST be present and contain the value
BASE64URL(JWE AAD)) when the JWE AAD value is non-empty;
otherwise, it MUST be absent. A JWE AAD value can be included to
supply a base64url-encoded value to be integrity protected but not
encrypted.
ciphertext
The "ciphertext" member MUST be present and contain the value
BASE64URL(JWE Ciphertext).
tag
The "tag" member MUST be present and contain the value
BASE64URL(JWE Authentication Tag) when the JWE Authentication Tag
value is non-empty; otherwise, it MUST be absent.
recipients
The "recipients" member value MUST be an array of JSON objects.
Each object contains information specific to a single recipient.
This member MUST be present with exactly one array element per
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recipient, even if some or all of the array element values are the
empty JSON object "{}" (which can happen when all Header Parameter
values are shared between all recipients and when no encrypted key
is used, such as when doing Direct Encryption).
The following members are defined for use in the JSON objects that
are elements of the "recipients" array:
header
The "header" member MUST be present and contain the value JWE Per-
Recipient Unprotected Header when the JWE Per-Recipient
Unprotected Header value is non-empty; otherwise, it MUST be
absent. This value is represented as an unencoded JSON object,
rather than as a string. These Header Parameter values are not
integrity protected.
encrypted_key
The "encrypted_key" member MUST be present and contain the value
BASE64URL(JWE Encrypted Key) when the JWE Encrypted Key value is
non-empty; otherwise, it MUST be absent.
At least one of the "header", "protected", and "unprotected" members
MUST be present so that "alg" and "enc" Header Parameter values are
conveyed for each recipient computation.
Additional members can be present in both the JSON objects defined
above; if not understood by implementations encountering them, they
MUST be ignored.
Some Header Parameters, including the "alg" parameter, can be shared
among all recipient computations. Header Parameters in the JWE
Protected Header and JWE Shared Unprotected Header values are shared
among all recipients.
The Header Parameter values used when creating or validating per-
recipient ciphertext and Authentication Tag values are the union of
the three sets of Header Parameter values that may be present: (1)
the JWE Protected Header represented in the "protected" member, (2)
the JWE Shared Unprotected Header represented in the "unprotected"
member, and (3) the JWE Per-Recipient Unprotected Header represented
in the "header" member of the recipient's array element. The union
of these sets of Header Parameters comprises the JOSE Header. The
Header Parameter names in the three locations MUST be disjoint.
Each JWE Encrypted Key value is computed using the parameters of the
corresponding JOSE Header value in the same manner as for the JWE
Compact Serialization. This has the desirable property that each JWE
Encrypted Key value in the "recipients" array is identical to the
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value that would have been computed for the same parameter in the JWE
Compact Serialization. Likewise, the JWE Ciphertext and JWE
Authentication Tag values match those produced for the JWE Compact
Serialization, provided that the JWE Protected Header value (which
represents the integrity-protected Header Parameter values) matches
that used in the JWE Compact Serialization.
All recipients use the same JWE Protected Header, JWE Initialization
Vector, JWE Ciphertext, and JWE Authentication Tag values, when
present, resulting in potentially significant space savings if the
message is large. Therefore, all Header Parameters that specify the
treatment of the plaintext value MUST be the same for all recipients.
This primarily means that the "enc" (encryption algorithm) Header
Parameter value in the JOSE Header for each recipient and any
parameters of that algorithm MUST be the same.
In summary, the syntax of a JWE using the general JWE JSON
Serialization is as follows:
{
"protected":"<integrity-protected shared header contents>",
"unprotected":<non-integrity-protected shared header contents>,
"recipients":[
{"header":<per-recipient unprotected header 1 contents>,
"encrypted_key":"<encrypted key 1 contents>"},
...
{"header":<per-recipient unprotected header N contents>,
"encrypted_key":"<encrypted key N contents>"}],
"aad":"<additional authenticated data contents>",
"iv":"<initialization vector contents>",
"ciphertext":"<ciphertext contents>",
"tag":"<authentication tag contents>"
}
See Appendix A.4 for an example JWE using the general JWE JSON
Serialization syntax.
7.2.2. Flattened JWE JSON Serialization Syntax
The flattened JWE JSON Serialization syntax is based upon the general
syntax, but flattens it, optimizing it for the single-recipient case.
It flattens it by removing the "recipients" member and instead
placing those members defined for use in the "recipients" array (the
"header" and "encrypted_key" members) in the top-level JSON object
(at the same level as the "ciphertext" member).
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The "recipients" member MUST NOT be present when using this syntax.
Other than this syntax difference, JWE JSON Serialization objects
using the flattened syntax are processed identically to those using
the general syntax.
In summary, the syntax of a JWE using the flattened JWE JSON
Serialization is as follows:
{
"protected":"<integrity-protected header contents>",
"unprotected":<non-integrity-protected header contents>,
"header":<more non-integrity-protected header contents>,
"encrypted_key":"<encrypted key contents>",
"aad":"<additional authenticated data contents>",
"iv":"<initialization vector contents>",
"ciphertext":"<ciphertext contents>",
"tag":"<authentication tag contents>"
}
Note that when using the flattened syntax, just as when using the
general syntax, any unprotected Header Parameter values can reside in
either the "unprotected" member or the "header" member, or in both.
See Appendix A.5 for an example JWE using the flattened JWE JSON
Serialization syntax.
8. TLS Requirements
The Transport Layer Security (TLS) requirements for this
specification are the same as those defined in Section 8 of [JWS].
9. Distinguishing between JWS and JWE Objects
There are several ways of distinguishing whether an object is a JWS
or JWE. All these methods will yield the same result for all legal
input values; they may yield different results for malformed inputs.
o If the object is using the JWS Compact Serialization or the JWE
Compact Serialization, the number of base64url-encoded segments
separated by period ('.') characters differs for JWSs and JWEs.
JWSs have three segments separated by two period ('.') characters.
JWEs have five segments separated by four period ('.') characters.
o If the object is using the JWS JSON Serialization or the JWE JSON
Serialization, the members used will be different. JWSs have a
"payload" member and JWEs do not. JWEs have a "ciphertext" member
and JWSs do not.
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o The JOSE Header for a JWS can be distinguished from the JOSE
Header for a JWE by examining the "alg" (algorithm) Header
Parameter value. If the value represents a digital signature or
MAC algorithm, or is the value "none", it is for a JWS; if it
represents a Key Encryption, Key Wrapping, Direct Key Agreement,
Key Agreement with Key Wrapping, or Direct Encryption algorithm,
it is for a JWE. (Extracting the "alg" value to examine is
straightforward when using the JWS Compact Serialization or the
JWE Compact Serialization and may be more difficult when using the
JWS JSON Serialization or the JWE JSON Serialization.)
o The JOSE Header for a JWS can also be distinguished from the JOSE
Header for a JWE by determining whether an "enc" (encryption
algorithm) member exists. If the "enc" member exists, it is a
JWE; otherwise, it is a JWS.
10. IANA Considerations
10.1. JSON Web Signature and Encryption Header Parameters Registration
This section registers the Header Parameter names defined in
Section 4.1 in the IANA "JSON Web Signature and Encryption Header
Parameters" registry established by [JWS].
10.1.1. Registry Contents
o Header Parameter Name: "alg"
o Header Parameter Description: Algorithm
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.1 of RFC 7516
o Header Parameter Name: "enc"
o Header Parameter Description: Encryption Algorithm
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.2 of RFC 7516
o Header Parameter Name: "zip"
o Header Parameter Description: Compression Algorithm
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.3 of RFC 7516
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o Header Parameter Name: "jku"
o Header Parameter Description: JWK Set URL
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.4 of RFC 7516
o Header Parameter Name: "jwk"
o Header Parameter Description: JSON Web Key
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.5 of RFC 7516
o Header Parameter Name: "kid"
o Header Parameter Description: Key ID
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.6 of RFC 7516
o Header Parameter Name: "x5u"
o Header Parameter Description: X.509 URL
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.7 of RFC 7516
o Header Parameter Name: "x5c"
o Header Parameter Description: X.509 Certificate Chain
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.8 of RFC 7516
o Header Parameter Name: "x5t"
o Header Parameter Description: X.509 Certificate SHA-1 Thumbprint
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.9 of RFC 7516
o Header Parameter Name: "x5t#S256"
o Header Parameter Description: X.509 Certificate SHA-256 Thumbprint
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.10 of RFC 7516
o Header Parameter Name: "typ"
o Header Parameter Description: Type
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.11 of RFC 7516
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o Header Parameter Name: "cty"
o Header Parameter Description: Content Type
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.12 of RFC 7516
o Header Parameter Name: "crit"
o Header Parameter Description: Critical
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.1.13 of RFC 7516
11. Security Considerations
All of the security issues that are pertinent to any cryptographic
application must be addressed by JWS/JWE/JWK agents. Among these
issues are protecting the user's asymmetric private and symmetric
secret keys and employing countermeasures to various attacks.
All the security considerations in the JWS specification also apply
to this specification. Likewise, all the security considerations in
XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411] also apply, other
than those that are XML specific.
11.1. Key Entropy and Random Values
See Section 10.1 of [JWS] for security considerations on key entropy
and random values. In addition to the uses of random values listed
there, note that random values are also used for Content Encryption
Keys (CEKs) and Initialization Vectors (IVs) when performing
encryption.
11.2. Key Protection
See Section 10.2 of [JWS] for security considerations on key
protection. In addition to the keys listed there that must be
protected, implementations performing encryption must protect the key
encryption key and the Content Encryption Key. Compromise of the key
encryption key may result in the disclosure of all contents protected
with that key. Similarly, compromise of the Content Encryption Key
may result in disclosure of the associated encrypted content.
Jones & Hildebrand Standards Track [Page 27]
RFC 7516 JSON Web Encryption (JWE) May 2015
11.3. Using Matching Algorithm Strengths
Algorithms of matching strengths should be used together whenever
possible. For instance, when AES Key Wrap is used with a given key
size, using the same key size is recommended when AES GCM is also
used. If the key encryption and content encryption algorithms are
different, the effective security is determined by the weaker of the
two algorithms.
Also, see RFC 3766 [RFC3766] for information on determining strengths
for public keys used for exchanging symmetric keys.
11.4. Adaptive Chosen-Ciphertext Attacks
When decrypting, particular care must be taken not to allow the JWE
recipient to be used as an oracle for decrypting messages. RFC 3218
[RFC3218] should be consulted for specific countermeasures to attacks
on RSAES-PKCS1-v1_5. An attacker might modify the contents of the
"alg" Header Parameter from "RSA-OAEP" to "RSA1_5" in order to
generate a formatting error that can be detected and used to recover
the CEK even if RSAES-OAEP was used to encrypt the CEK. It is
therefore particularly important to report all formatting errors to
the CEK, Additional Authenticated Data, or ciphertext as a single
error when the encrypted content is rejected.
Additionally, this type of attack can be prevented by restricting the
use of a key to a limited set of algorithms -- usually one. This
means, for instance, that if the key is marked as being for
"RSA-OAEP" only, any attempt to decrypt a message using the "RSA1_5"
algorithm with that key should fail immediately due to invalid use of
the key.
11.5. Timing Attacks
To mitigate the attacks described in RFC 3218 [RFC3218], the
recipient MUST NOT distinguish between format, padding, and length
errors of encrypted keys. It is strongly recommended, in the event
of receiving an improperly formatted key, that the recipient
substitute a randomly generated CEK and proceed to the next step, to
mitigate timing attacks.
Jones & Hildebrand Standards Track [Page 28]
RFC 7516 JSON Web Encryption (JWE) May 2015
12. References
12.1. Normative References
[JWA] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<http://www.rfc-editor.org/info/rfc7518>.
[JWK] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
<http://www.rfc-editor.org/info/rfc1951>.
[RFC20] Cerf, V., "ASCII format for Network Interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<http://www.rfc-editor.org/info/rfc20>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<http://www.rfc-editor.org/info/rfc4949>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.
Jones & Hildebrand Standards Track [Page 29]
RFC 7516 JSON Web Encryption (JWE) May 2015
[UNICODE] The Unicode Consortium, "The Unicode Standard",
<http://www.unicode.org/versions/latest/>.
12.2. Informative References
[AES] National Institute of Standards and Technology (NIST),
"Advanced Encryption Standard (AES)", FIPS PUB 197,
November 2001, <http://csrc.nist.gov/publications/
fips/fips197/fips-197.pdf>.
[JSE] Bradley, J. and N. Sakimura (editor), "JSON Simple
Encryption", September 2010,
<http://jsonenc.info/enc/1.0/>.
[JSMS] Rescorla, E. and J. Hildebrand, "JavaScript Message
Security Format", Work in Progress,
draft-rescorla-jsms-00, March 2011.
[NIST.800-38D]
National Institute of Standards and Technology (NIST),
"Recommendation for Block Cipher Modes of Operation:
Galois/Counter Mode (GCM) and GMAC", NIST PUB 800-38D,
November 2007, <http://csrc.nist.gov/publications/
nistpubs/800-38D/SP-800-38D.pdf>.
[RFC3218] Rescorla, E., "Preventing the Million Message Attack on
Cryptographic Message Syntax", RFC 3218,
DOI 10.17487/RFC3218, January 2002,
<http://www.rfc-editor.org/info/rfc3218>.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February
2003, <http://www.rfc-editor.org/info/rfc3447>.
[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For
Public Keys Used For Exchanging Symmetric Keys", BCP 86,
RFC 3766, DOI 10.17487/RFC3766, April 2004,
<http://www.rfc-editor.org/info/rfc3766>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>.
Jones & Hildebrand Standards Track [Page 30]
RFC 7516 JSON Web Encryption (JWE) May 2015
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://www.rfc-editor.org/info/rfc5652>.
[W3C.REC-xmlenc-core1-20130411]
Eastlake, D., Reagle, J., Hirsch, F., and T. Roessler,
"XML Encryption Syntax and Processing Version 1.1", World
Wide Web Consortium Recommendation
REC-xmlenc-core1-20130411, April 2013,
<http://www.w3.org/TR/2013/REC-xmlenc-core1-20130411/>.
Jones & Hildebrand Standards Track [Page 31]
RFC 7516 JSON Web Encryption (JWE) May 2015
Appendix A. JWE Examples
This section provides examples of JWE computations.
A.1. Example JWE using RSAES-OAEP and AES GCM
This example encrypts the plaintext "The true sign of intelligence is
not knowledge but imagination." to the recipient using RSAES-OAEP for
key encryption and AES GCM for content encryption. The
representation of this plaintext (using JSON array notation) is:
[84, 104, 101, 32, 116, 114, 117, 101, 32, 115, 105, 103, 110, 32,
111, 102, 32, 105, 110, 116, 101, 108, 108, 105, 103, 101, 110, 99,
101, 32, 105, 115, 32, 110, 111, 116, 32, 107, 110, 111, 119, 108,
101, 100, 103, 101, 32, 98, 117, 116, 32, 105, 109, 97, 103, 105,
110, 97, 116, 105, 111, 110, 46]
A.1.1. JOSE Header
The following example JWE Protected Header declares that:
o The Content Encryption Key is encrypted to the recipient using the
RSAES-OAEP algorithm to produce the JWE Encrypted Key.
o Authenticated encryption is performed on the plaintext using the
AES GCM algorithm with a 256-bit key to produce the ciphertext and
the Authentication Tag.
{"alg":"RSA-OAEP","enc":"A256GCM"}
Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
Header)) gives this value:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
A.1.2. Content Encryption Key (CEK)
Generate a 256-bit random CEK. In this example, the value (using
JSON array notation) is:
[177, 161, 244, 128, 84, 143, 225, 115, 63, 180, 3, 255, 107, 154,
212, 246, 138, 7, 110, 91, 112, 46, 34, 105, 47, 130, 203, 46, 122,
234, 64, 252]
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A.1.3. Key Encryption
Encrypt the CEK with the recipient's public key using the RSAES-OAEP
algorithm to produce the JWE Encrypted Key. This example uses the
RSA key represented in JSON Web Key [JWK] format below (with line
breaks within values for display purposes only):
{"kty":"RSA",
"n":"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW
cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S
psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a
sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS
tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj
YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw",
"e":"AQAB",
"d":"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N
WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9
3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk
qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl
t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd
VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ",
"p":"1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ-
SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf
fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0",
"q":"wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm
UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX
IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc",
"dp":"ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL
hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827
rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE",
"dq":"Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj
ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB
UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis",
"qi":"VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7
AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3
eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY"
}
Jones & Hildebrand Standards Track [Page 33]
RFC 7516 JSON Web Encryption (JWE) May 2015
The resulting JWE Encrypted Key value is:
[56, 163, 154, 192, 58, 53, 222, 4, 105, 218, 136, 218, 29, 94, 203,
22, 150, 92, 129, 94, 211, 232, 53, 89, 41, 60, 138, 56, 196, 216,
82, 98, 168, 76, 37, 73, 70, 7, 36, 8, 191, 100, 136, 196, 244, 220,
145, 158, 138, 155, 4, 117, 141, 230, 199, 247, 173, 45, 182, 214,
74, 177, 107, 211, 153, 11, 205, 196, 171, 226, 162, 128, 171, 182,
13, 237, 239, 99, 193, 4, 91, 219, 121, 223, 107, 167, 61, 119, 228,
173, 156, 137, 134, 200, 80, 219, 74, 253, 56, 185, 91, 177, 34, 158,
89, 154, 205, 96, 55, 18, 138, 43, 96, 218, 215, 128, 124, 75, 138,
243, 85, 25, 109, 117, 140, 26, 155, 249, 67, 167, 149, 231, 100, 6,
41, 65, 214, 251, 232, 87, 72, 40, 182, 149, 154, 168, 31, 193, 126,
215, 89, 28, 111, 219, 125, 182, 139, 235, 195, 197, 23, 234, 55, 58,
63, 180, 68, 202, 206, 149, 75, 205, 248, 176, 67, 39, 178, 60, 98,
193, 32, 238, 122, 96, 158, 222, 57, 183, 111, 210, 55, 188, 215,
206, 180, 166, 150, 166, 106, 250, 55, 229, 72, 40, 69, 214, 216,
104, 23, 40, 135, 212, 28, 127, 41, 80, 175, 174, 168, 115, 171, 197,
89, 116, 92, 103, 246, 83, 216, 182, 176, 84, 37, 147, 35, 45, 219,
172, 99, 226, 233, 73, 37, 124, 42, 72, 49, 242, 35, 127, 184, 134,
117, 114, 135, 206]
Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
this value (with line breaks for display purposes only):
OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
6UklfCpIMfIjf7iGdXKHzg
A.1.4. Initialization Vector
Generate a random 96-bit JWE Initialization Vector. In this example,
the value is:
[227, 197, 117, 252, 2, 219, 233, 68, 180, 225, 77, 219]
Encoding this JWE Initialization Vector as BASE64URL(JWE
Initialization Vector) gives this value:
48V1_ALb6US04U3b
Jones & Hildebrand Standards Track [Page 34]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.1.5. Additional Authenticated Data
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
116, 84, 48, 70, 70, 85, 67, 73, 115, 73, 109, 86, 117, 89, 121, 73,
54, 73, 107, 69, 121, 78, 84, 90, 72, 81, 48, 48, 105, 102, 81]
A.1.6. Content Encryption
Perform authenticated encryption on the plaintext with the AES GCM
algorithm using the CEK as the encryption key, the JWE Initialization
Vector, and the Additional Authenticated Data value above, requesting
a 128-bit Authentication Tag output. The resulting ciphertext is:
[229, 236, 166, 241, 53, 191, 115, 196, 174, 43, 73, 109, 39, 122,
233, 96, 140, 206, 120, 52, 51, 237, 48, 11, 190, 219, 186, 80, 111,
104, 50, 142, 47, 167, 59, 61, 181, 127, 196, 21, 40, 82, 242, 32,
123, 143, 168, 226, 73, 216, 176, 144, 138, 247, 106, 60, 16, 205,
160, 109, 64, 63, 192]
The resulting Authentication Tag value is:
[92, 80, 104, 49, 133, 25, 161, 215, 173, 101, 219, 211, 136, 91,
210, 145]
Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
value (with line breaks for display purposes only):
5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
SdiwkIr3ajwQzaBtQD_A
Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
Tag) gives this value:
XFBoMYUZodetZdvTiFvSkQ
Jones & Hildebrand Standards Track [Page 35]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.1.7. Complete Representation
Assemble the final representation: The Compact Serialization of this
result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
Authentication Tag).
The final result in this example (with line breaks for display
purposes only) is:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ.
OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe
ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb
Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV
mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8
1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi
6UklfCpIMfIjf7iGdXKHzg.
48V1_ALb6US04U3b.
5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji
SdiwkIr3ajwQzaBtQD_A.
XFBoMYUZodetZdvTiFvSkQ
A.1.8. Validation
This example illustrates the process of creating a JWE with
RSAES-OAEP for key encryption and AES GCM for content encryption.
These results can be used to validate JWE decryption implementations
for these algorithms. Note that since the RSAES-OAEP computation
includes random values, the encryption results above will not be
completely reproducible. However, since the AES GCM computation is
deterministic, the JWE Encrypted Ciphertext values will be the same
for all encryptions performed using these inputs.
A.2. Example JWE using RSAES-PKCS1-v1_5 and AES_128_CBC_HMAC_SHA_256
This example encrypts the plaintext "Live long and prosper." to the
recipient using RSAES-PKCS1-v1_5 for key encryption and
AES_128_CBC_HMAC_SHA_256 for content encryption. The representation
of this plaintext (using JSON array notation) is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
112, 114, 111, 115, 112, 101, 114, 46]
Jones & Hildebrand Standards Track [Page 36]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.2.1. JOSE Header
The following example JWE Protected Header declares that:
o The Content Encryption Key is encrypted to the recipient using the
RSAES-PKCS1-v1_5 algorithm to produce the JWE Encrypted Key.
o Authenticated encryption is performed on the plaintext using the
AES_128_CBC_HMAC_SHA_256 algorithm to produce the ciphertext and
the Authentication Tag.
{"alg":"RSA1_5","enc":"A128CBC-HS256"}
Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
Header)) gives this value:
eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
A.2.2. Content Encryption Key (CEK)
Generate a 256-bit random CEK. In this example, the key value is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
44, 207]
Jones & Hildebrand Standards Track [Page 37]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.2.3. Key Encryption
Encrypt the CEK with the recipient's public key using the
RSAES-PKCS1-v1_5 algorithm to produce the JWE Encrypted Key. This
example uses the RSA key represented in JSON Web Key [JWK] format
below (with line breaks within values for display purposes only):
{"kty":"RSA",
"n":"sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl
UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre
cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_
7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI
Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU
7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw",
"e":"AQAB",
"d":"VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq
1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry
nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_
0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj
-VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj
T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ",
"p":"9gY2w6I6S6L0juEKsbeDAwpd9WMfgqFoeA9vEyEUuk4kLwBKcoe1x4HG68
ik918hdDSE9vDQSccA3xXHOAFOPJ8R9EeIAbTi1VwBYnbTp87X-xcPWlEP
krdoUKW60tgs1aNd_Nnc9LEVVPMS390zbFxt8TN_biaBgelNgbC95sM",
"q":"uKlCKvKv_ZJMVcdIs5vVSU_6cPtYI1ljWytExV_skstvRSNi9r66jdd9-y
BhVfuG4shsp2j7rGnIio901RBeHo6TPKWVVykPu1iYhQXw1jIABfw-MVsN
-3bQ76WLdt2SDxsHs7q7zPyUyHXmps7ycZ5c72wGkUwNOjYelmkiNS0",
"dp":"w0kZbV63cVRvVX6yk3C8cMxo2qCM4Y8nsq1lmMSYhG4EcL6FWbX5h9yuv
ngs4iLEFk6eALoUS4vIWEwcL4txw9LsWH_zKI-hwoReoP77cOdSL4AVcra
Hawlkpyd2TWjE5evgbhWtOxnZee3cXJBkAi64Ik6jZxbvk-RR3pEhnCs",
"dq":"o_8V14SezckO6CNLKs_btPdFiO9_kC1DsuUTd2LAfIIVeMZ7jn1Gus_Ff
7B7IVx3p5KuBGOVF8L-qifLb6nQnLysgHDh132NDioZkhH7mI7hPG-PYE_
odApKdnqECHWw0J-F0JWnUd6D2B_1TvF9mXA2Qx-iGYn8OVV1Bsmp6qU",
"qi":"eNho5yRBEBxhGBtQRww9QirZsB66TrfFReG_CcteI1aCneT0ELGhYlRlC
tUkTRclIfuEPmNsNDPbLoLqqCVznFbvdB7x-Tl-m0l_eFTj2KiqwGqE9PZ
B9nNTwMVvH3VRRSLWACvPnSiwP8N5Usy-WRXS-V7TbpxIhvepTfE0NNo"
}
Jones & Hildebrand Standards Track [Page 38]
RFC 7516 JSON Web Encryption (JWE) May 2015
The resulting JWE Encrypted Key value is:
[80, 104, 72, 58, 11, 130, 236, 139, 132, 189, 255, 205, 61, 86, 151,
176, 99, 40, 44, 233, 176, 189, 205, 70, 202, 169, 72, 40, 226, 181,
156, 223, 120, 156, 115, 232, 150, 209, 145, 133, 104, 112, 237, 156,
116, 250, 65, 102, 212, 210, 103, 240, 177, 61, 93, 40, 71, 231, 223,
226, 240, 157, 15, 31, 150, 89, 200, 215, 198, 203, 108, 70, 117, 66,
212, 238, 193, 205, 23, 161, 169, 218, 243, 203, 128, 214, 127, 253,
215, 139, 43, 17, 135, 103, 179, 220, 28, 2, 212, 206, 131, 158, 128,
66, 62, 240, 78, 186, 141, 125, 132, 227, 60, 137, 43, 31, 152, 199,
54, 72, 34, 212, 115, 11, 152, 101, 70, 42, 219, 233, 142, 66, 151,
250, 126, 146, 141, 216, 190, 73, 50, 177, 146, 5, 52, 247, 28, 197,
21, 59, 170, 247, 181, 89, 131, 241, 169, 182, 246, 99, 15, 36, 102,
166, 182, 172, 197, 136, 230, 120, 60, 58, 219, 243, 149, 94, 222,
150, 154, 194, 110, 227, 225, 112, 39, 89, 233, 112, 207, 211, 241,
124, 174, 69, 221, 179, 107, 196, 225, 127, 167, 112, 226, 12, 242,
16, 24, 28, 120, 182, 244, 213, 244, 153, 194, 162, 69, 160, 244,
248, 63, 165, 141, 4, 207, 249, 193, 79, 131, 0, 169, 233, 127, 167,
101, 151, 125, 56, 112, 111, 248, 29, 232, 90, 29, 147, 110, 169,
146, 114, 165, 204, 71, 136, 41, 252]
Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
this value (with line breaks for display purposes only):
UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm
1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc
HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF
NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8
rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv
-B3oWh2TbqmScqXMR4gp_A
A.2.4. Initialization Vector
Generate a random 128-bit JWE Initialization Vector. In this
example, the value is:
[3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
101]
Encoding this JWE Initialization Vector as BASE64URL(JWE
Initialization Vector) gives this value:
AxY8DCtDaGlsbGljb3RoZQ
Jones & Hildebrand Standards Track [Page 39]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.2.5. Additional Authenticated Data
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69,
120, 88, 122, 85, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105,
74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85,
50, 73, 110, 48]
A.2.6. Content Encryption
Perform authenticated encryption on the plaintext with the
AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption
key, the JWE Initialization Vector, and the Additional Authenticated
Data value above. The steps for doing this using the values from
Appendix A.3 are detailed in Appendix B. The resulting ciphertext
is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102]
The resulting Authentication Tag value is:
[246, 17, 244, 190, 4, 95, 98, 3, 231, 0, 115, 157, 242, 203, 100,
191]
Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
value:
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
Tag) gives this value:
9hH0vgRfYgPnAHOd8stkvw
A.2.7. Complete Representation
Assemble the final representation: The Compact Serialization of this
result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
Authentication Tag).
Jones & Hildebrand Standards Track [Page 40]
RFC 7516 JSON Web Encryption (JWE) May 2015
The final result in this example (with line breaks for display
purposes only) is:
eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm
1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc
HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF
NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8
rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv
-B3oWh2TbqmScqXMR4gp_A.
AxY8DCtDaGlsbGljb3RoZQ.
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
9hH0vgRfYgPnAHOd8stkvw
A.2.8. Validation
This example illustrates the process of creating a JWE with
RSAES-PKCS1-v1_5 for key encryption and AES_CBC_HMAC_SHA2 for content
encryption. These results can be used to validate JWE decryption
implementations for these algorithms. Note that since the
RSAES-PKCS1-v1_5 computation includes random values, the encryption
results above will not be completely reproducible. However, since
the AES-CBC computation is deterministic, the JWE Encrypted
Ciphertext values will be the same for all encryptions performed
using these inputs.
A.3. Example JWE Using AES Key Wrap and AES_128_CBC_HMAC_SHA_256
This example encrypts the plaintext "Live long and prosper." to the
recipient using AES Key Wrap for key encryption and
AES_128_CBC_HMAC_SHA_256 for content encryption. The representation
of this plaintext (using JSON array notation) is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
112, 114, 111, 115, 112, 101, 114, 46]
A.3.1. JOSE Header
The following example JWE Protected Header declares that:
o The Content Encryption Key is encrypted to the recipient using the
AES Key Wrap algorithm with a 128-bit key to produce the JWE
Encrypted Key.
o Authenticated encryption is performed on the plaintext using the
AES_128_CBC_HMAC_SHA_256 algorithm to produce the ciphertext and
the Authentication Tag.
{"alg":"A128KW","enc":"A128CBC-HS256"}
Jones & Hildebrand Standards Track [Page 41]
RFC 7516 JSON Web Encryption (JWE) May 2015
Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
Header)) gives this value:
eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
A.3.2. Content Encryption Key (CEK)
Generate a 256-bit random CEK. In this example, the value is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
44, 207]
A.3.3. Key Encryption
Encrypt the CEK with the shared symmetric key using the AES Key Wrap
algorithm to produce the JWE Encrypted Key. This example uses the
symmetric key represented in JSON Web Key [JWK] format below:
{"kty":"oct",
"k":"GawgguFyGrWKav7AX4VKUg"
}
The resulting JWE Encrypted Key value is:
[232, 160, 123, 211, 183, 76, 245, 132, 200, 128, 123, 75, 190, 216,
22, 67, 201, 138, 193, 186, 9, 91, 122, 31, 246, 90, 28, 139, 57, 3,
76, 124, 193, 11, 98, 37, 173, 61, 104, 57]
Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives
this value:
6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ
A.3.4. Initialization Vector
Generate a random 128-bit JWE Initialization Vector. In this
example, the value is:
[3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
101]
Encoding this JWE Initialization Vector as BASE64URL(JWE
Initialization Vector) gives this value:
AxY8DCtDaGlsbGljb3RoZQ
Jones & Hildebrand Standards Track [Page 42]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.3.5. Additional Authenticated Data
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
110, 48]
A.3.6. Content Encryption
Perform authenticated encryption on the plaintext with the
AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption
key, the JWE Initialization Vector, and the Additional Authenticated
Data value above. The steps for doing this using the values from
this example are detailed in Appendix B. The resulting ciphertext
is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102]
The resulting Authentication Tag value is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
194, 85]
Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
value:
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
Tag) gives this value:
U0m_YmjN04DJvceFICbCVQ
A.3.7. Complete Representation
Assemble the final representation: The Compact Serialization of this
result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' ||
BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization
Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE
Authentication Tag).
Jones & Hildebrand Standards Track [Page 43]
RFC 7516 JSON Web Encryption (JWE) May 2015
The final result in this example (with line breaks for display
purposes only) is:
eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.
6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.
AxY8DCtDaGlsbGljb3RoZQ.
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.
U0m_YmjN04DJvceFICbCVQ
A.3.8. Validation
This example illustrates the process of creating a JWE with AES Key
Wrap for key encryption and AES GCM for content encryption. These
results can be used to validate JWE decryption implementations for
these algorithms. Also, since both the AES Key Wrap and AES GCM
computations are deterministic, the resulting JWE value will be the
same for all encryptions performed using these inputs. Since the
computation is reproducible, these results can also be used to
validate JWE encryption implementations for these algorithms.
A.4. Example JWE Using General JWE JSON Serialization
This section contains an example using the general JWE JSON
Serialization syntax. This example demonstrates the capability for
encrypting the same plaintext to multiple recipients.
Two recipients are present in this example. The algorithm and key
used for the first recipient are the same as that used in
Appendix A.2. The algorithm and key used for the second recipient
are the same as that used in Appendix A.3. The resulting JWE
Encrypted Key values are therefore the same; those computations are
not repeated here.
The plaintext, the CEK, JWE Initialization Vector, and JWE Protected
Header are shared by all recipients (which must be the case, since
the ciphertext and Authentication Tag are also shared).
Jones & Hildebrand Standards Track [Page 44]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.4.1. JWE Per-Recipient Unprotected Headers
The first recipient uses the RSAES-PKCS1-v1_5 algorithm to encrypt
the CEK. The second uses AES Key Wrap to encrypt the CEK. Key ID
values are supplied for both keys. The two JWE Per-Recipient
Unprotected Header values used to represent these algorithms and key
IDs are:
{"alg":"RSA1_5","kid":"2011-04-29"}
and
{"alg":"A128KW","kid":"7"}
A.4.2. JWE Protected Header
Authenticated encryption is performed on the plaintext using the
AES_128_CBC_HMAC_SHA_256 algorithm to produce the common JWE
Ciphertext and JWE Authentication Tag values. The JWE Protected
Header value representing this is:
{"enc":"A128CBC-HS256"}
Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected
Header)) gives this value:
eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
A.4.3. JWE Shared Unprotected Header
This JWE uses the "jku" Header Parameter to reference a JWK Set.
This is represented in the following JWE Shared Unprotected Header
value as:
{"jku":"https://server.example.com/keys.jwks"}
A.4.4. Complete JOSE Header Values
Combining the JWE Per-Recipient Unprotected Header, JWE Protected
Header, and JWE Shared Unprotected Header values supplied, the JOSE
Header values used for the first and second recipient, respectively,
are:
{"alg":"RSA1_5",
"kid":"2011-04-29",
"enc":"A128CBC-HS256",
"jku":"https://server.example.com/keys.jwks"}
Jones & Hildebrand Standards Track [Page 45]
RFC 7516 JSON Web Encryption (JWE) May 2015
and
{"alg":"A128KW",
"kid":"7",
"enc":"A128CBC-HS256",
"jku":"https://server.example.com/keys.jwks"}
A.4.5. Additional Authenticated Data
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is:
[101, 121, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73,
52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48]
A.4.6. Content Encryption
Perform authenticated encryption on the plaintext with the
AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption
key, the JWE Initialization Vector, and the Additional Authenticated
Data value above. The steps for doing this using the values from
Appendix A.3 are detailed in Appendix B. The resulting ciphertext
is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102]
The resulting Authentication Tag value is:
[51, 63, 149, 60, 252, 148, 225, 25, 92, 185, 139, 245, 35, 2, 47,
207]
Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this
value:
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication
Tag) gives this value:
Mz-VPPyU4RlcuYv1IwIvzw
Jones & Hildebrand Standards Track [Page 46]
RFC 7516 JSON Web Encryption (JWE) May 2015
A.4.7. Complete JWE JSON Serialization Representation
The complete JWE JSON Serialization for these values is as follows
(with line breaks within values for display purposes only):
{
"protected":
"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
"unprotected":
{"jku":"https://server.example.com/keys.jwks"},
"recipients":[
{"header":
{"alg":"RSA1_5","kid":"2011-04-29"},
"encrypted_key":
"UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-
kFm1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKx
GHZ7PcHALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3
YvkkysZIFNPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPh
cCdZ6XDP0_F8rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPg
wCp6X-nZZd9OHBv-B3oWh2TbqmScqXMR4gp_A"},
{"header":
{"alg":"A128KW","kid":"7"},
"encrypted_key":
"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"}],
"iv":
"AxY8DCtDaGlsbGljb3RoZQ",
"ciphertext":
"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
"tag":
"Mz-VPPyU4RlcuYv1IwIvzw"
}
A.5. Example JWE Using Flattened JWE JSON Serialization
This section contains an example using the flattened JWE JSON
Serialization syntax. This example demonstrates the capability for
encrypting the plaintext to a single recipient in a flattened JSON
structure.
The values in this example are the same as those for the second
recipient of the previous example in Appendix A.4.
Jones & Hildebrand Standards Track [Page 47]
RFC 7516 JSON Web Encryption (JWE) May 2015
The complete JWE JSON Serialization for these values is as follows
(with line breaks within values for display purposes only):
{
"protected":
"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
"unprotected":
{"jku":"https://server.example.com/keys.jwks"},
"header":
{"alg":"A128KW","kid":"7"},
"encrypted_key":
"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ",
"iv":
"AxY8DCtDaGlsbGljb3RoZQ",
"ciphertext":
"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
"tag":
"Mz-VPPyU4RlcuYv1IwIvzw"
}
Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation
This example shows the steps in the AES_128_CBC_HMAC_SHA_256
authenticated encryption computation using the values from the
example in Appendix A.3. As described where this algorithm is
defined in Sections 5.2 and 5.2.3 of JWA, the AES_CBC_HMAC_SHA2
family of algorithms are implemented using Advanced Encryption
Standard (AES) in Cipher Block Chaining (CBC) mode with Public-Key
Cryptography Standards (PKCS) #7 padding to perform the encryption
and an HMAC SHA-2 function to perform the integrity calculation -- in
this case, HMAC SHA-256.
B.1. Extract MAC_KEY and ENC_KEY from Key
The 256 bit AES_128_CBC_HMAC_SHA_256 key K used in this example
(using JSON array notation) is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
206, 107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156,
44, 207]
Use the first 128 bits of this key as the HMAC SHA-256 key MAC_KEY,
which is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106,
206]
Jones & Hildebrand Standards Track [Page 48]
RFC 7516 JSON Web Encryption (JWE) May 2015
Use the last 128 bits of this key as the AES-CBC key ENC_KEY, which
is:
[107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156, 44,
207]
Note that the MAC key comes before the encryption key in the input
key K; this is in the opposite order of the algorithm names in the
identifiers "AES_128_CBC_HMAC_SHA_256" and "A128CBC-HS256".
B.2. Encrypt Plaintext to Create Ciphertext
Encrypt the plaintext with AES in CBC mode using PKCS #7 padding
using the ENC_KEY above. The plaintext in this example is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32,
112, 114, 111, 115, 112, 101, 114, 46]
The encryption result is as follows, which is the ciphertext output:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6,
75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102]
B.3. 64-Bit Big-Endian Representation of AAD Length
The Additional Authenticated Data (AAD) in this example is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
110, 48]
This AAD is 51-bytes long, which is 408-bits long. The octet string
AL, which is the number of bits in AAD expressed as a big-endian
64-bit unsigned integer is:
[0, 0, 0, 0, 0, 0, 1, 152]
B.4. Initialization Vector Value
The Initialization Vector value used in this example is:
[3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104,
101]
Jones & Hildebrand Standards Track [Page 49]
RFC 7516 JSON Web Encryption (JWE) May 2015
B.5. Create Input to HMAC Computation
Concatenate the AAD, the Initialization Vector, the ciphertext, and
the AL value. The result of this concatenation is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73,
110, 48, 3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111,
116, 104, 101, 40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24,
152, 230, 6, 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215,
104, 143, 112, 56, 102, 0, 0, 0, 0, 0, 0, 1, 152]
B.6. Compute HMAC Value
Compute the HMAC SHA-256 of the concatenated value above. This
result M is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
194, 85, 9, 84, 229, 201, 219, 135, 44, 252, 145, 102, 179, 140, 105,
86, 229, 116]
B.7. Truncate HMAC Value to Create Authentication Tag
Use the first half (128 bits) of the HMAC output M as the
Authentication Tag output T. This truncated value is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38,
194, 85]
Acknowledgements
Solutions for encrypting JSON content were also explored by "JSON
Simple Encryption" [JSE] and "JavaScript Message Security Format"
[JSMS], both of which significantly influenced this document. This
document attempts to explicitly reuse as many of the relevant
concepts from XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411] and
RFC 5652 [RFC5652] as possible, while utilizing simple, compact JSON-
based data structures.
Special thanks are due to John Bradley, Eric Rescorla, and Nat
Sakimura for the discussions that helped inform the content of this
specification; to Eric Rescorla and Joe Hildebrand for allowing the
reuse of text from [JSMS] in this document; and to Eric Rescorla for
co-authoring many drafts of this specification.
Thanks to Axel Nennker, Emmanuel Raviart, Brian Campbell, and Edmund
Jay for validating the examples in this specification.
Jones & Hildebrand Standards Track [Page 50]
RFC 7516 JSON Web Encryption (JWE) May 2015
This specification is the work of the JOSE working group, which
includes dozens of active and dedicated participants. In particular,
the following individuals contributed ideas, feedback, and wording
that influenced this specification:
Richard Barnes, John Bradley, Brian Campbell, Alissa Cooper, Breno de
Medeiros, Stephen Farrell, Dick Hardt, Jeff Hodges, Russ Housley,
Edmund Jay, Scott Kelly, Stephen Kent, Barry Leiba, James Manger,
Matt Miller, Kathleen Moriarty, Tony Nadalin, Hideki Nara, Axel
Nennker, Ray Polk, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat
Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
Sean Turner, Stephen Farrell, and Kathleen Moriarty served as
Security Area Directors during the creation of this specification.
Authors' Addresses
Michael B. Jones
Microsoft
EMail: mbj@microsoft.com
URI: http://self-issued.info/
Joe Hildebrand
Cisco Systems, Inc.
EMail: jhildebr@cisco.com
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