[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]
Versions: 00 01 02 03 04 05 06 07 08 09 10 11
12 13 14 15 16 17 18 19 20 21 22 23
24 25 26 27 28 29 30 31 32 33 34 35
36 37 38 39 40 RFC 7518
JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track September 15, 2013
Expires: March 19, 2014
JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-16
Abstract
The JSON Web Algorithms (JWA) specification registers cryptographic
algorithms and identifiers to be used with the JSON Web Signature
(JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK)
specifications. It defines several IANA registries for these
identifiers.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 19, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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 Expires March 19, 2014 [Page 1]
Internet-Draft JSON Web Algorithms (JWA) September 2013
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Terms Incorporated from the JWS Specification . . . . . . 5
2.2. Terms Incorporated from the JWE Specification . . . . . . 6
2.3. Terms Incorporated from the JWK Specification . . . . . . 9
2.4. Defined Terms . . . . . . . . . . . . . . . . . . . . . . 9
3. Cryptographic Algorithms for Digital Signatures and MACs . . . 9
3.1. "alg" (Algorithm) Header Parameter Values for JWS . . . . 9
3.2. HMAC with SHA-2 Functions . . . . . . . . . . . . . . . . 10
3.3. Digital Signature with RSASSA-PKCS1-V1_5 . . . . . . . . . 11
3.4. Digital Signature with ECDSA . . . . . . . . . . . . . . . 12
3.5. Digital Signature with RSASSA-PSS . . . . . . . . . . . . 14
3.6. Using the Algorithm "none" . . . . . . . . . . . . . . . . 15
4. Cryptographic Algorithms for Encryption . . . . . . . . . . . 15
4.1. "alg" (Algorithm) Header Parameter Values for JWE . . . . 15
4.2. "enc" (Encryption Method) Header Parameter Values for
JWE . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3. Key Encryption with RSAES-PKCS1-V1_5 . . . . . . . . . . . 21
4.4. Key Encryption with RSAES OAEP . . . . . . . . . . . . . . 21
4.5. Key Wrapping with AES Key Wrap . . . . . . . . . . . . . . 21
4.6. Direct Encryption with a Shared Symmetric Key . . . . . . 21
4.7. Key Agreement with Elliptic Curve Diffie-Hellman
Ephemeral Static (ECDH-ES) . . . . . . . . . . . . . . . . 22
4.7.1. Header Parameters Used for ECDH Key Agreement . . . . 22
4.7.1.1. "epk" (Ephemeral Public Key) Header Parameter . . 22
4.7.1.2. "apu" (Agreement PartyUInfo) Header Parameter . . 23
4.7.1.3. "apv" (Agreement PartyVInfo) Header Parameter . . 23
4.7.2. Key Derivation for ECDH Key Agreement . . . . . . . . 23
4.8. Key Encryption with AES GCM . . . . . . . . . . . . . . . 24
4.8.1. Header Parameters Used for AES GCM Key Encryption . . 25
4.8.1.1. "iv" (Initialization Vector) Header Parameter . . 25
4.8.1.2. "tag" (Authentication Tag) Header Parameter . . . 25
4.9. Key Encryption with PBES2 . . . . . . . . . . . . . . . . 25
4.9.1. Header Parameters Used for PBES2 Key Encryption . . . 26
4.9.1.1. "p2s" (PBES2 salt) Parameter . . . . . . . . . . . 26
4.9.1.2. "p2c" (PBES2 count) Parameter . . . . . . . . . . 26
4.10. AES_CBC_HMAC_SHA2 Algorithms . . . . . . . . . . . . . . . 26
4.10.1. Conventions Used in Defining AES_CBC_HMAC_SHA2 . . . . 27
4.10.2. Generic AES_CBC_HMAC_SHA2 Algorithm . . . . . . . . . 27
4.10.2.1. AES_CBC_HMAC_SHA2 Encryption . . . . . . . . . . . 27
4.10.2.2. AES_CBC_HMAC_SHA2 Decryption . . . . . . . . . . . 29
4.10.3. AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . 29
4.10.4. AES_192_CBC_HMAC_SHA_384 . . . . . . . . . . . . . . . 30
4.10.5. AES_256_CBC_HMAC_SHA_512 . . . . . . . . . . . . . . . 30
4.10.6. Plaintext Encryption with AES_CBC_HMAC_SHA2 . . . . . 30
Jones Expires March 19, 2014 [Page 2]
Internet-Draft JSON Web Algorithms (JWA) September 2013
4.11. Plaintext Encryption with AES GCM . . . . . . . . . . . . 31
5. Cryptographic Algorithms for Keys . . . . . . . . . . . . . . 31
5.1. "kty" (Key Type) Parameter Values . . . . . . . . . . . . 31
5.2. Parameters for Elliptic Curve Keys . . . . . . . . . . . . 32
5.2.1. Parameters for Elliptic Curve Public Keys . . . . . . 32
5.2.1.1. "crv" (Curve) Parameter . . . . . . . . . . . . . 32
5.2.1.2. "x" (X Coordinate) Parameter . . . . . . . . . . . 33
5.2.1.3. "y" (Y Coordinate) Parameter . . . . . . . . . . . 33
5.2.2. Parameters for Elliptic Curve Private Keys . . . . . . 33
5.2.2.1. "d" (ECC Private Key) Parameter . . . . . . . . . 33
5.3. Parameters for RSA Keys . . . . . . . . . . . . . . . . . 33
5.3.1. Parameters for RSA Public Keys . . . . . . . . . . . . 33
5.3.1.1. "n" (Modulus) Parameter . . . . . . . . . . . . . 33
5.3.1.2. "e" (Exponent) Parameter . . . . . . . . . . . . . 34
5.3.2. Parameters for RSA Private Keys . . . . . . . . . . . 34
5.3.2.1. "d" (Private Exponent) Parameter . . . . . . . . . 34
5.3.2.2. "p" (First Prime Factor) Parameter . . . . . . . . 34
5.3.2.3. "q" (Second Prime Factor) Parameter . . . . . . . 34
5.3.2.4. "dp" (First Factor CRT Exponent) Parameter . . . . 35
5.3.2.5. "dq" (Second Factor CRT Exponent) Parameter . . . 35
5.3.2.6. "qi" (First CRT Coefficient) Parameter . . . . . . 35
5.3.2.7. "oth" (Other Primes Info) Parameter . . . . . . . 35
5.4. Parameters for Symmetric Keys . . . . . . . . . . . . . . 36
5.4.1. "k" (Key Value) Parameter . . . . . . . . . . . . . . 36
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
6.1. JSON Web Signature and Encryption Algorithms Registry . . 37
6.1.1. Template . . . . . . . . . . . . . . . . . . . . . . . 38
6.1.2. Initial Registry Contents . . . . . . . . . . . . . . 38
6.2. JWE Header Parameter Names Registration . . . . . . . . . 43
6.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 43
6.3. JSON Web Encryption Compression Algorithms Registry . . . 44
6.3.1. Registration Template . . . . . . . . . . . . . . . . 44
6.3.2. Initial Registry Contents . . . . . . . . . . . . . . 45
6.4. JSON Web Key Types Registry . . . . . . . . . . . . . . . 45
6.4.1. Registration Template . . . . . . . . . . . . . . . . 45
6.4.2. Initial Registry Contents . . . . . . . . . . . . . . 46
6.5. JSON Web Key Parameters Registration . . . . . . . . . . . 46
6.5.1. Registry Contents . . . . . . . . . . . . . . . . . . 46
6.6. JSON Web Key Elliptic Curve Registry . . . . . . . . . . . 48
6.6.1. Registration Template . . . . . . . . . . . . . . . . 48
6.6.2. Initial Registry Contents . . . . . . . . . . . . . . 49
7. Security Considerations . . . . . . . . . . . . . . . . . . . 49
7.1. Algorithms and Key Sizes will be Deprecated . . . . . . . 50
7.2. Key Lifetimes . . . . . . . . . . . . . . . . . . . . . . 50
7.3. RSAES-PKCS1-v1_5 Security Considerations . . . . . . . . . 50
7.4. AES GCM Security Considerations . . . . . . . . . . . . . 50
7.5. Plaintext JWS Security Considerations . . . . . . . . . . 51
7.6. Denial of Service Attacks . . . . . . . . . . . . . . . . 51
Jones Expires March 19, 2014 [Page 3]
Internet-Draft JSON Web Algorithms (JWA) September 2013
7.7. Reusing Key Material when Encrypting Keys . . . . . . . . 52
7.8. Password Considerations . . . . . . . . . . . . . . . . . 52
8. Internationalization Considerations . . . . . . . . . . . . . 52
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.1. Normative References . . . . . . . . . . . . . . . . . . . 53
9.2. Informative References . . . . . . . . . . . . . . . . . . 55
Appendix A. Digital Signature/MAC Algorithm Identifier
Cross-Reference . . . . . . . . . . . . . . . . . . . 56
Appendix B. Encryption Algorithm Identifier Cross-Reference . . . 57
Appendix C. Test Cases for AES_CBC_HMAC_SHA2 Algorithms . . . . . 58
C.1. Test Cases for AES_128_CBC_HMAC_SHA_256 . . . . . . . . . 59
C.2. Test Cases for AES_192_CBC_HMAC_SHA_384 . . . . . . . . . 60
C.3. Test Cases for AES_256_CBC_HMAC_SHA_512 . . . . . . . . . 61
Appendix D. Example ECDH-ES Key Agreement Computation . . . . . . 62
Appendix E. Acknowledgements . . . . . . . . . . . . . . . . . . 64
Appendix F. Document History . . . . . . . . . . . . . . . . . . 65
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 72
Jones Expires March 19, 2014 [Page 4]
Internet-Draft JSON Web Algorithms (JWA) September 2013
1. Introduction
The JSON Web Algorithms (JWA) specification registers cryptographic
algorithms and identifiers to be used with the JSON Web Signature
(JWS) [JWS], JSON Web Encryption (JWE) [JWE], and JSON Web Key (JWK)
[JWK] specifications. It defines several IANA registries for these
identifiers. All these specifications utilize JavaScript Object
Notation (JSON) [RFC4627] based data structures. This specification
also describes the semantics and operations that are specific to
these algorithms and key types.
Registering the algorithms and identifiers here, rather than in the
JWS, JWE, and JWK specifications, is intended to allow them to remain
unchanged in the face of changes in the set of Required, Recommended,
Optional, and Deprecated algorithms over time. This also allows
changes to the JWS, JWE, and JWK specifications without changing this
document.
Names defined by this specification are short because a core goal is
for the resulting representations to be compact.
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in Key words for use in
RFCs to Indicate Requirement Levels [RFC2119]. If these words are
used without being spelled in uppercase then they are to be
interpreted with their normal natural language meanings.
2. Terminology
2.1. Terms Incorporated from the JWS Specification
These terms defined by the JSON Web Signature (JWS) [JWS]
specification are incorporated into this specification:
JSON Web Signature (JWS) A data structure representing a digitally
signed or MACed message. The structure represents three values:
the JWS Header, the JWS Payload, and the JWS Signature.
JSON Text Object A UTF-8 [RFC3629] encoded text string representing
a JSON object; the syntax of JSON objects is defined in Section
2.2 of [RFC4627].
Jones Expires March 19, 2014 [Page 5]
Internet-Draft JSON Web Algorithms (JWA) September 2013
JWS Header A JSON Text Object (or JSON Text Objects, when using the
JWS JSON Serialization) that describes the digital signature or
MAC operation applied to create the JWS Signature value. The
members of the JWS Header object(s) are Header Parameters.
JWS Payload The sequence of octets to be secured -- a.k.a., the
message. The payload can contain an arbitrary sequence of octets.
JWS Signature A sequence of octets containing the cryptographic
material that ensures the integrity of the JWS Protected Header
and the JWS Payload. The JWS Signature value is a digital
signature or MAC value calculated over the JWS Signing Input using
the parameters specified in the JWS Header.
JWS Protected Header A JSON Text Object that contains the portion of
the JWS Header that is integrity protected. For the JWS Compact
Serialization, this comprises the entire JWS Header. For the JWS
JSON Serialization, this is one component of the JWS Header.
Base64url Encoding Base64 encoding using the URL- and filename-safe
character set defined in Section 5 of RFC 4648 [RFC4648], with all
trailing '=' characters omitted (as permitted by Section 3.2).
(See Appendix C of [JWS] for notes on implementing base64url
encoding without padding.)
Encoded JWS Header Base64url encoding of the JWS Protected Header.
Encoded JWS Payload Base64url encoding of the JWS Payload.
Encoded JWS Signature Base64url encoding of the JWS Signature.
JWS Signing Input The concatenation of the Encoded JWS Header, a
period ('.') character, and the Encoded JWS Payload.
2.2. Terms Incorporated from the JWE Specification
These terms defined by the JSON Web Encryption (JWE) [JWE]
specification are incorporated into this specification:
JSON Web Encryption (JWE) A data structure representing an encrypted
message. The structure represents five values: the JWE Header,
the JWE Encrypted Key, the JWE Initialization Vector, the JWE
Ciphertext, and the JWE Authentication Tag.
Authenticated Encryption An Authenticated Encryption algorithm is
one that provides an integrated content integrity check.
Authenticated Encryption algorithms accept two inputs, the
Plaintext and the Additional Authenticated Data value, and produce
Jones Expires March 19, 2014 [Page 6]
Internet-Draft JSON Web Algorithms (JWA) September 2013
two outputs, the Ciphertext and the Authentication Tag value. AES
Galois/Counter Mode (GCM) is one such algorithm.
Plaintext The sequence of octets to be encrypted -- a.k.a., the
message. The plaintext can contain an arbitrary sequence of
octets.
Ciphertext An encrypted representation of the Plaintext.
Additional Authenticated Data (AAD) An input to an Authenticated
Encryption operation that is integrity protected but not
encrypted.
Authentication Tag An output of an Authenticated Encryption
operation that ensures the integrity of the Ciphertext and the
Additional Authenticated Data. Note that some algorithms may not
use an Authentication Tag, in which case this value is the empty
octet sequence.
Content Encryption Key (CEK) A symmetric key for the Authenticated
Encryption algorithm used to encrypt the Plaintext for the
recipient to produce the Ciphertext and the Authentication Tag.
JWE Header A JSON Text Object (or JSON Text Objects, when using the
JWE JSON Serialization) that describes the encryption operations
applied to create the JWE Encrypted Key, the JWE Ciphertext, and
the JWE Authentication Tag. The members of the JWE Header
object(s) are Header Parameters.
JWE Encrypted Key The result of encrypting the Content Encryption
Key (CEK) with the intended recipient's key using the specified
algorithm. Note that for some algorithms, the JWE Encrypted Key
value is specified as being the empty octet sequence.
JWE Initialization Vector A sequence of octets containing the
Initialization Vector used when encrypting the Plaintext. Note
that some algorithms may not use an Initialization Vector, in
which case this value is the empty octet sequence.
JWE Ciphertext A sequence of octets containing the Ciphertext for a
JWE.
JWE Authentication Tag A sequence of octets containing the
Authentication Tag for a JWE.
Jones Expires March 19, 2014 [Page 7]
Internet-Draft JSON Web Algorithms (JWA) September 2013
JWE Protected Header A JSON Text Object that contains the portion of
the JWE Header that is integrity protected. For the JWE Compact
Serialization, this comprises the entire JWE Header. For the JWE
JSON Serialization, this is one component of the JWE Header.
Encoded JWE Header Base64url encoding of the JWE Protected Header.
Encoded JWE Encrypted Key Base64url encoding of the JWE Encrypted
Key.
Encoded JWE Initialization Vector Base64url encoding of the JWE
Initialization Vector.
Encoded JWE Ciphertext Base64url encoding of the JWE Ciphertext.
Encoded JWE Authentication Tag Base64url encoding of the JWE
Authentication Tag.
Key Management Mode A method of determining the Content Encryption
Key (CEK) value to use. Each algorithm used for determining the
CEK value uses a specific Key Management Mode. Key Management
Modes employed by this specification are Key Encryption, Key
Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping,
and Direct Encryption.
Key Encryption A Key Management Mode in which the Content Encryption
Key (CEK) value is encrypted to the intended recipient using an
asymmetric encryption algorithm.
Key Wrapping A Key Management Mode in which the Content Encryption
Key (CEK) value is encrypted to the intended recipient using a
symmetric key wrapping algorithm.
Direct Key Agreement A Key Management Mode in which a key agreement
algorithm is used to agree upon the Content Encryption Key (CEK)
value.
Key Agreement with Key Wrapping A Key Management Mode in which a key
agreement algorithm is used to agree upon a symmetric key used to
encrypt the Content Encryption Key (CEK) value to the intended
recipient using a symmetric key wrapping algorithm.
Direct Encryption A Key Management Mode in which the Content
Encryption Key (CEK) value used is the secret symmetric key value
shared between the parties.
Jones Expires March 19, 2014 [Page 8]
Internet-Draft JSON Web Algorithms (JWA) September 2013
2.3. Terms Incorporated from the JWK Specification
These terms defined by the JSON Web Key (JWK) [JWK] specification are
incorporated into this specification:
JSON Web Key (JWK) A JSON object that represents a cryptographic
key.
JSON Web Key Set (JWK Set) A JSON object that contains an array of
JWKs as the value of its "keys" member.
2.4. Defined Terms
These terms are defined for use by this specification:
Header Parameter A name/value pair that is member of a JWS Header or
JWE Header.
Header Parameter Name The name of a member of a JSON object
representing a JWS Header or JWE Header.
Header Parameter Value The value of a member of a JSON object
representing a JWS Header or JWE Header.
3. Cryptographic Algorithms for Digital Signatures and MACs
JWS uses cryptographic algorithms to digitally sign or create a
Message Authentication Codes (MAC) of the contents of the JWS Header
and the JWS Payload.
3.1. "alg" (Algorithm) Header Parameter Values for JWS
The table below is the set of "alg" (algorithm) header parameter
values defined by this specification for use with JWS, each of which
is explained in more detail in the following sections:
Jones Expires March 19, 2014 [Page 9]
Internet-Draft JSON Web Algorithms (JWA) September 2013
+-----------+--------------------------------------+----------------+
| alg | Digital Signature or MAC Algorithm | Implementation |
| Parameter | | Requirements |
| Value | | |
+-----------+--------------------------------------+----------------+
| HS256 | HMAC using SHA-256 hash algorithm | Required |
| HS384 | HMAC using SHA-384 hash algorithm | Optional |
| HS512 | HMAC using SHA-512 hash algorithm | Optional |
| RS256 | RSASSA-PKCS-v1_5 using SHA-256 hash | Recommended |
| | algorithm | |
| RS384 | RSASSA-PKCS-v1_5 using SHA-384 hash | Optional |
| | algorithm | |
| RS512 | RSASSA-PKCS-v1_5 using SHA-512 hash | Optional |
| | algorithm | |
| ES256 | ECDSA using P-256 curve and SHA-256 | Recommended+ |
| | hash algorithm | |
| ES384 | ECDSA using P-384 curve and SHA-384 | Optional |
| | hash algorithm | |
| ES512 | ECDSA using P-521 curve and SHA-512 | Optional |
| | hash algorithm | |
| PS256 | RSASSA-PSS using SHA-256 hash | Optional |
| | algorithm and MGF1 mask generation | |
| | function with SHA-256 | |
| PS384 | RSASSA-PSS using SHA-384 hash | Optional |
| | algorithm and MGF1 mask generation | |
| | function with SHA-384 | |
| PS512 | RSASSA-PSS using SHA-512 hash | Optional |
| | algorithm and MGF1 mask generation | |
| | function with SHA-512 | |
| none | No digital signature or MAC value | Optional |
| | included | |
+-----------+--------------------------------------+----------------+
The use of "+" in the Implementation Requirements indicates that the
requirement strength is likely to be increased in a future version of
the specification.
See Appendix A for a table cross-referencing the digital signature
and MAC "alg" (algorithm) values used in this specification with the
equivalent identifiers used by other standards and software packages.
3.2. HMAC with SHA-2 Functions
Hash-based Message Authentication Codes (HMACs) enable one to use a
secret plus a cryptographic hash function to generate a Message
Authentication Code (MAC). This can be used to demonstrate that
whoever generated the MAC was in possession of the MAC key.
Jones Expires March 19, 2014 [Page 10]
Internet-Draft JSON Web Algorithms (JWA) September 2013
The algorithm for implementing and validating HMACs is provided in
RFC 2104 [RFC2104]. This section defines the use of the HMAC SHA-
256, HMAC SHA-384, and HMAC SHA-512 functions [SHS]. The "alg"
(algorithm) header parameter values "HS256", "HS384", and "HS512" are
used in the JWS Header to indicate that the Encoded JWS Signature
contains a base64url encoded HMAC value using the respective hash
function.
A key of the same size as the hash output (for instance, 256 bits for
"HS256") or larger MUST be used with this algorithm.
The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the
hash algorithm "H", using the octets of the ASCII [USASCII]
representation of the JWS Signing Input as the "text" value, and
using the shared key. The HMAC output value is the JWS Signature.
The JWS signature is base64url encoded to produce the Encoded JWS
Signature.
The HMAC SHA-256 MAC for a JWS is validated by computing an HMAC
value per RFC 2104, using SHA-256 as the hash algorithm "H", using
the octets of the ASCII representation of the received JWS Signing
Input as the "text" value, and using the shared key. This computed
HMAC value is then compared to the result of base64url decoding the
received Encoded JWS signature. Alternatively, the computed HMAC
value can be base64url encoded and compared to the received Encoded
JWS Signature, as this comparison produces the same result as
comparing the unencoded values. In either case, if the values match,
the HMAC has been validated.
Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is
performed identically to the procedure for HMAC SHA-256 - just using
the corresponding hash algorithms with correspondingly larger minimum
key sizes and result values: 384 bits each for HMAC SHA-384 and 512
bits each for HMAC SHA-512.
An example using this algorithm is shown in Appendix A.1 of [JWS].
3.3. Digital Signature with RSASSA-PKCS1-V1_5
This section defines the use of the RSASSA-PKCS1-V1_5 digital
signature algorithm as defined in Section 8.2 of RFC 3447 [RFC3447]
(commonly known as PKCS #1), using SHA-256, SHA-384, or SHA-512 [SHS]
as the hash functions. The "alg" (algorithm) header parameter values
"RS256", "RS384", and "RS512" are used in the JWS Header to indicate
that the Encoded JWS Signature contains a base64url encoded RSASSA-
PKCS1-V1_5 digital signature using the respective hash function.
A key of size 2048 bits or larger MUST be used with these algorithms.
Jones Expires March 19, 2014 [Page 11]
Internet-Draft JSON Web Algorithms (JWA) September 2013
The RSASSA-PKCS1-V1_5 SHA-256 digital signature is generated as
follows:
1. Generate a digital signature of the octets of the ASCII
representation of the JWS Signing Input using RSASSA-PKCS1-V1_5-
SIGN and the SHA-256 hash function with the desired private key.
The output will be an octet sequence.
2. Base64url encode the resulting octet sequence.
The output is the Encoded JWS Signature for that JWS.
The RSASSA-PKCS1-V1_5 SHA-256 digital signature for a JWS is
validated as follows:
1. Take the Encoded JWS Signature and base64url decode it into an
octet sequence. If decoding fails, the validation has failed.
2. Submit the octets of the ASCII representation of the JWS Signing
Input and the public key corresponding to the private key used by
the signer to the RSASSA-PKCS1-V1_5-VERIFY algorithm using SHA-
256 as the hash function.
Signing with the RSASSA-PKCS1-V1_5 SHA-384 and RSASSA-PKCS1-V1_5 SHA-
512 algorithms is performed identically to the procedure for RSASSA-
PKCS1-V1_5 SHA-256 - just using the corresponding hash algorithms
instead of SHA-256.
An example using this algorithm is shown in Appendix A.2 of [JWS].
3.4. Digital Signature with ECDSA
The Elliptic Curve Digital Signature Algorithm (ECDSA) [DSS] provides
for the use of Elliptic Curve cryptography, which is able to provide
equivalent security to RSA cryptography but using shorter key sizes
and with greater processing speed. This means that ECDSA digital
signatures will be substantially smaller in terms of length than
equivalently strong RSA digital signatures.
This specification defines the use of ECDSA with the P-256 curve and
the SHA-256 cryptographic hash function, ECDSA with the P-384 curve
and the SHA-384 hash function, and ECDSA with the P-521 curve and the
SHA-512 hash function. The P-256, P-384, and P-521 curves are
defined in [DSS]. The "alg" (algorithm) header parameter values
"ES256", "ES384", and "ES512" are used in the JWS Header to indicate
that the Encoded JWS Signature contains a base64url encoded ECDSA
P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512 digital
signature, respectively.
Jones Expires March 19, 2014 [Page 12]
Internet-Draft JSON Web Algorithms (JWA) September 2013
The ECDSA P-256 SHA-256 digital signature is generated as follows:
1. Generate a digital signature of the octets of the ASCII
representation of the JWS Signing Input using ECDSA P-256 SHA-256
with the desired private key. The output will be the pair (R,
S), where R and S are 256 bit unsigned integers.
2. Turn R and S into octet sequences in big endian order, with each
array being be 32 octets long. The octet sequence
representations MUST NOT be shortened to omit any leading zero
octets contained in the values.
3. Concatenate the two octet sequences in the order R and then S.
(Note that many ECDSA implementations will directly produce this
concatenation as their output.)
4. Base64url encode the resulting 64 octet sequence.
The output is the Encoded JWS Signature for the JWS.
The ECDSA P-256 SHA-256 digital signature for a JWS is validated as
follows:
1. Take the Encoded JWS Signature and base64url decode it into an
octet sequence. If decoding fails, the validation has failed.
2. The output of the base64url decoding MUST be a 64 octet sequence.
If decoding does not result in a 64 octet sequence, the
validation has failed.
3. Split the 64 octet sequence into two 32 octet sequences. The
first array will be R and the second S (with both being in big
endian octet order).
4. Submit the octets of the ASCII representation of the JWS Signing
Input R, S and the public key (x, y) to the ECDSA P-256 SHA-256
validator.
Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512
algorithms is performed identically to the procedure for ECDSA P-256
SHA-256 - just using the corresponding hash algorithms with
correspondingly larger result values. For ECDSA P-384 SHA-384, R and
S will be 384 bits each, resulting in a 96 octet sequence. For ECDSA
P-521 SHA-512, R and S will be 521 bits each, resulting in a 132
octet sequence.
Examples using these algorithms are shown in Appendices A.3 and A.4
of [JWS].
Jones Expires March 19, 2014 [Page 13]
Internet-Draft JSON Web Algorithms (JWA) September 2013
3.5. Digital Signature with RSASSA-PSS
This section defines the use of the RSASSA-PSS digital signature
algorithm as defined in Section 8.1 of RFC 3447 [RFC3447] with the
MGF1 mask generation function, always using the same hash function
for both the RSASSA-PSS hash function and the MGF1 hash function.
Use of SHA-256, SHA-384, and SHA-512 as these hash functions is
defined. The size of the salt value is the same size as the hash
function output. All other algorithm parameters use the defaults
specified in Section A.2.3 of RFC 3447. The "alg" (algorithm) header
parameter values "PS256", "PS384", and "PS512" are used in the JWS
Header to indicate that the Encoded JWS Signature contains a
base64url encoded RSASSA-PSS digital signature using the respective
hash function in both roles.
A key of size 2048 bits or larger MUST be used with this algorithm.
The RSASSA-PSS SHA-256 digital signature is generated as follows:
1. Generate a digital signature of the octets of the ASCII
representation of the JWS Signing Input using RSASSA-PSS-SIGN,
the SHA-256 hash function, and the MGF1 mask generation function
with SHA-256 with the desired private key. The output will be an
octet sequence.
2. Base64url encode the resulting octet sequence.
The output is the Encoded JWS Signature for that JWS.
The RSASSA-PSS SHA-256 digital signature for a JWS is validated as
follows:
1. Take the Encoded JWS Signature and base64url decode it into an
octet sequence. If decoding fails, the validation has failed.
2. Submit the octets of the ASCII representation of the JWS Signing
Input and the public key corresponding to the private key used by
the signer to the RSASSA-PSS-VERIFY algorithm using SHA-256 as
the hash function and using MGF1 as the mask generation function
with SHA-256.
Signing with the RSASSA-PSS SHA-384 and RSASSA-PSS SHA-512 algorithms
is performed identically to the procedure for RSASSA-PSS SHA-256 -
just using the alternative hash algorithm in both roles.
Jones Expires March 19, 2014 [Page 14]
Internet-Draft JSON Web Algorithms (JWA) September 2013
3.6. Using the Algorithm "none"
JWSs MAY also be created that do not provide integrity protection.
Such a JWS is called a "Plaintext JWS". Plaintext JWSs MUST use the
"alg" value "none", and are formatted identically to other JWSs, but
with the empty string for its JWS Signature value. See Section 7.5
for security considerations associated with using this algorithm.
4. Cryptographic Algorithms for Encryption
JWE uses cryptographic algorithms to encrypt the Content Encryption
Key (CEK) and the Plaintext.
4.1. "alg" (Algorithm) Header Parameter Values for JWE
The table below is the set of "alg" (algorithm) header parameter
values that are defined by this specification for use with JWE.
These algorithms are used to encrypt the CEK, producing the JWE
Encrypted Key, or to use key agreement to agree upon the CEK.
+-------------------+-----------------+------------+----------------+
| alg Parameter | Key Management | Additional | Implementation |
| Value | Algorithm | Header | Requirements |
| | | Parameters | |
+-------------------+-----------------+------------+----------------+
| RSA1_5 | RSAES-PKCS1-V1_ | (none) | Required |
| | 5[RFC3447] | | |
| RSA-OAEP | RSAES using | (none) | Optional |
| | Optimal | | |
| | Asymmetric | | |
| | Encryption | | |
| | Padding (OAEP) | | |
| | [RFC3447], with | | |
| | the default | | |
| | parameters | | |
| | specified by | | |
| | RFC 3447 in | | |
| | Section A.2.1 | | |
Jones Expires March 19, 2014 [Page 15]
Internet-Draft JSON Web Algorithms (JWA) September 2013
| A128KW | Advanced | (none) | Recommended |
| | Encryption | | |
| | Standard (AES) | | |
| | Key Wrap | | |
| | Algorithm | | |
| | [RFC3394] using | | |
| | the default | | |
| | initial value | | |
| | specified in | | |
| | Section 2.2.3.1 | | |
| | and using 128 | | |
| | bit keys | | |
| A192KW | AES Key Wrap | (none) | Optional |
| | Algorithm using | | |
| | the default | | |
| | initial value | | |
| | specified in | | |
| | Section 2.2.3.1 | | |
| | and using 192 | | |
| | bit keys | | |
| A256KW | AES Key Wrap | (none) | Recommended |
| | Algorithm using | | |
| | the default | | |
| | initial value | | |
| | specified in | | |
| | Section 2.2.3.1 | | |
| | and using 256 | | |
| | bit keys | | |
| dir | Direct use of a | (none) | Recommended |
| | shared | | |
| | symmetric key | | |
| | as the Content | | |
| | Encryption Key | | |
| | (CEK) for the | | |
| | content | | |
| | encryption step | | |
| | (rather than | | |
| | using the | | |
| | symmetric key | | |
| | to wrap the | | |
| | CEK) | | |
Jones Expires March 19, 2014 [Page 16]
Internet-Draft JSON Web Algorithms (JWA) September 2013
| ECDH-ES | Elliptic Curve | "epk", | Recommended+ |
| | Diffie-Hellman | "apu", | |
| | Ephemeral | "apv" | |
| | Static | | |
| | [RFC6090] key | | |
| | agreement using | | |
| | the Concat KDF, | | |
| | as defined in | | |
| | Section 5.8.1 | | |
| | of | | |
| | [NIST.800-56A], | | |
| | with the | | |
| | agreed-upon key | | |
| | being used | | |
| | directly as the | | |
| | Content | | |
| | Encryption Key | | |
| | (CEK) (rather | | |
| | than being used | | |
| | to wrap the | | |
| | CEK), as | | |
| | specified in | | |
| | Section 4.7 | | |
| ECDH-ES+A128KW | Elliptic Curve | "epk", | Recommended |
| | Diffie-Hellman | "apu", | |
| | Ephemeral | "apv" | |
| | Static key | | |
| | agreement per | | |
| | "ECDH-ES" and | | |
| | Section 4.7, | | |
| | where the | | |
| | agreed-upon key | | |
| | is used to wrap | | |
| | the Content | | |
| | Encryption Key | | |
| | (CEK) with the | | |
| | "A128KW" | | |
| | function | | |
| | (rather than | | |
| | being used | | |
| | directly as the | | |
| | CEK) | | |
Jones Expires March 19, 2014 [Page 17]
Internet-Draft JSON Web Algorithms (JWA) September 2013
| ECDH-ES+A192KW | Elliptic Curve | "epk", | Optional |
| | Diffie-Hellman | "apu", | |
| | Ephemeral | "apv" | |
| | Static key | | |
| | agreement, | | |
| | where the | | |
| | agreed-upon key | | |
| | is used to wrap | | |
| | the Content | | |
| | Encryption Key | | |
| | (CEK) with the | | |
| | "A192KW" | | |
| | function | | |
| | (rather than | | |
| | being used | | |
| | directly as the | | |
| | CEK) | | |
| ECDH-ES+A256KW | Elliptic Curve | "epk", | Recommended |
| | Diffie-Hellman | "apu", | |
| | Ephemeral | "apv" | |
| | Static key | | |
| | agreement, | | |
| | where the | | |
| | agreed-upon key | | |
| | is used to wrap | | |
| | the Content | | |
| | Encryption Key | | |
| | (CEK) with the | | |
| | "A256KW" | | |
| | function | | |
| | (rather than | | |
| | being used | | |
| | directly as the | | |
| | CEK) | | |
| A128GCMKW | AES in | "iv", | Optional |
| | Galois/Counter | "tag" | |
| | Mode (GCM) | | |
| | [AES] | | |
| | [NIST.800-38D] | | |
| | using 128 bit | | |
| | keys | | |
| A192GCMKW | AES GCM using | "iv", | Optional |
| | 192 bit keys | "tag" | |
| A256GCMKW | AES GCM using | "iv", | Optional |
| | 256 bit keys | "tag" | |
Jones Expires March 19, 2014 [Page 18]
Internet-Draft JSON Web Algorithms (JWA) September 2013
| PBES2-HS256+A128K | PBES2 [RFC2898] | "p2s", | Optional |
| W | with HMAC | "p2c" | |
| | SHA-256 as the | | |
| | PRF and AES Key | | |
| | Wrap [RFC3394] | | |
| | using 128 bit | | |
| | keys for the | | |
| | encryption | | |
| | scheme | | |
| PBES2-HS384+A192K | PBES2 with HMAC | "p2s", | Optional |
| W | SHA-256 as the | "p2c" | |
| | PRF and AES Key | | |
| | Wrap using 192 | | |
| | bit keys for | | |
| | the encryption | | |
| | scheme | | |
| PBES2-HS512+A256K | PBES2 with HMAC | "p2s", | Optional |
| W | SHA-256 as the | "p2c" | |
| | PRF and AES Key | | |
| | Wrap using 256 | | |
| | bit keys for | | |
| | the encryption | | |
| | scheme | | |
+-------------------+-----------------+------------+----------------+
The Additional Header Parameters column indicates what additional
Header Parameters are used by the algorithm, beyond "alg", which all
use. All but "dir" and "ECDH-ES" also produce a JWE Encrypted Key
value.
The use of "+" in the Implementation Requirements indicates that the
requirement strength is likely to be increased in a future version of
the specification.
4.2. "enc" (Encryption Method) Header Parameter Values for JWE
The table below is the set of "enc" (encryption method) header
parameter values that are defined by this specification for use with
JWE. These algorithms are used to encrypt the Plaintext, which
produces the Ciphertext.
Jones Expires March 19, 2014 [Page 19]
Internet-Draft JSON Web Algorithms (JWA) September 2013
+-------------+------------------------+------------+---------------+
| enc | Content Encryption | Additional | Implementatio |
| Parameter | Algorithm | Header | nRequirements |
| Value | | Parameters | |
+-------------+------------------------+------------+---------------+
| A128CBC-HS2 | The | (none) | Required |
| 56 | AES_128_CBC_HMAC_SHA_2 | | |
| | 56 authenticated | | |
| | encryption algorithm, | | |
| | as defined in | | |
| | Section 4.10.3. This | | |
| | algorithm uses a 256 | | |
| | bit key. | | |
| A192CBC-HS3 | The | (none) | Optional |
| 84 | AES_192_CBC_HMAC_SHA_3 | | |
| | 84 authenticated | | |
| | encryption algorithm, | | |
| | as defined in | | |
| | Section 4.10.4. This | | |
| | algorithm uses a 384 | | |
| | bit key. | | |
| A256CBC-HS5 | The | (none) | Required |
| 12 | AES_256_CBC_HMAC_SHA_5 | | |
| | 12 authenticated | | |
| | encryption algorithm, | | |
| | as defined in | | |
| | Section 4.10.5. This | | |
| | algorithm uses a 512 | | |
| | bit key. | | |
| A128GCM | AES in Galois/Counter | (none) | Recommended |
| | Mode (GCM) [AES] | | |
| | [NIST.800-38D] using | | |
| | 128 bit keys | | |
| A192GCM | AES GCM using 192 bit | (none) | Optional |
| | keys | | |
| A256GCM | AES GCM using 256 bit | (none) | Recommended |
| | keys | | |
+-------------+------------------------+------------+---------------+
The Additional Header Parameters column indicates what additional
Header Parameters are used by the algorithm, beyond "enc", which all
use. All also use a JWE Initialization Vector value and produce JWE
Ciphertext and JWE Authentication Tag values.
See Appendix B for a table cross-referencing the encryption "alg"
(algorithm) and "enc" (encryption method) values used in this
specification with the equivalent identifiers used by other standards
and software packages.
Jones Expires March 19, 2014 [Page 20]
Internet-Draft JSON Web Algorithms (JWA) September 2013
4.3. Key Encryption with RSAES-PKCS1-V1_5
This section defines the specifics of encrypting a JWE CEK with
RSAES-PKCS1-V1_5 [RFC3447]. The "alg" header parameter value
"RSA1_5" is used in this case.
A key of size 2048 bits or larger MUST be used with this algorithm.
An example using this algorithm is shown in Appendix A.2 of [JWE].
4.4. Key Encryption with RSAES OAEP
This section defines the specifics of encrypting a JWE CEK with RSAES
using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with
the default parameters specified by RFC 3447 in Section A.2.1.
(Those default parameters are using a hash function of SHA-1 and a
mask generation function of MGF1 with SHA-1.) The "alg" header
parameter value "RSA-OAEP" is used in this case.
A key of size 2048 bits or larger MUST be used with this algorithm.
An example using this algorithm is shown in Appendix A.1 of [JWE].
4.5. Key Wrapping with AES Key Wrap
This section defines the specifics of encrypting a JWE CEK with the
Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using
the default initial value specified in Section 2.2.3.1 using 128,
192, or 256 bit keys. The "alg" header parameter values "A128KW",
"A192KW", or "A256KW" are respectively used in this case.
An example using this algorithm is shown in Appendix A.3 of [JWE].
4.6. Direct Encryption with a Shared Symmetric Key
This section defines the specifics of directly performing symmetric
key encryption without performing a key wrapping step. In this case,
the shared symmetric key is used directly as the Content Encryption
Key (CEK) value for the "enc" algorithm. An empty octet sequence is
used as the JWE Encrypted Key value. The "alg" header parameter
value "dir" is used in this case.
Refer to the security considerations on key lifetimes in Section 7.2
and AES GCM in Section 7.4 when considering utilizing direct
encryption.
Jones Expires March 19, 2014 [Page 21]
Internet-Draft JSON Web Algorithms (JWA) September 2013
4.7. Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static
(ECDH-ES)
This section defines the specifics of key agreement with Elliptic
Curve Diffie-Hellman Ephemeral Static [RFC6090], in combination with
the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A]. The
key agreement result can be used in one of two ways:
1. directly as the Content Encryption Key (CEK) for the "enc"
algorithm, in the Direct Key Agreement mode, or
2. as a symmetric key used to wrap the CEK with the "A128KW",
"A192KW", or "A256KW" algorithms, in the Key Agreement with Key
Wrapping mode.
The "alg" header parameter value "ECDH-ES" is used in the Direct Key
Agreement mode and the values "ECDH-ES+A128KW", "ECDH-ES+A192KW", or
"ECDH-ES+A256KW" are used in the Key Agreement with Key Wrapping
mode.
In the Direct Key Agreement case, the output of the Concat KDF MUST
be a key of the same length as that used by the "enc" algorithm; in
this case, the empty octet sequence is used as the JWE Encrypted Key
value. In the Key Agreement with Key Wrapping case, the output of
the Concat KDF MUST be a key of the length needed for the specified
key wrapping algorithm, one of 128, 192, or 256 bits respectively.
A new ephemeral public key value MUST be generated for each key
agreement operation.
4.7.1. Header Parameters Used for ECDH Key Agreement
The following Header Parameter Names are used for key agreement as
defined below.
4.7.1.1. "epk" (Ephemeral Public Key) Header Parameter
The "epk" (ephemeral public key) value created by the originator for
the use in key agreement algorithms. This key is represented as a
JSON Web Key [JWK] public key value. It MUST contain only public key
parameters and SHOULD contain only the minimum JWK parameters
necessary to represent the key; other JWK parameters included can be
checked for consistency and honored or can be ignored. This Header
Parameter is REQUIRED and MUST be understood and processed by
implementations when these algorithms are used.
Jones Expires March 19, 2014 [Page 22]
Internet-Draft JSON Web Algorithms (JWA) September 2013
4.7.1.2. "apu" (Agreement PartyUInfo) Header Parameter
The "apu" (agreement PartyUInfo) value for key agreement algorithms
using it (such as "ECDH-ES"), represented as a base64url encoded
string. When used, the PartyUInfo value contains information about
the sender. Use of this Header Parameter is OPTIONAL. This Header
Parameter MUST be understood and processed by implementations when
these algorithms are used.
4.7.1.3. "apv" (Agreement PartyVInfo) Header Parameter
The "apv" (agreement PartyVInfo) value for key agreement algorithms
using it (such as "ECDH-ES"), represented as a base64url encoded
string. When used, the PartyVInfo value contains information about
the receiver. Use of this Header Parameter is OPTIONAL. This Header
Parameter MUST be understood and processed by implementations when
these algorithms are used.
4.7.2. Key Derivation for ECDH Key Agreement
The key derivation process derives the agreed upon key from the
shared secret Z established through the ECDH algorithm, per Section
6.2.2.2 of [NIST.800-56A].
Key derivation is performed using the Concat KDF, as defined in
Section 5.8.1 of [NIST.800-56A], where the Digest Method is SHA-256.
The Concat KDF parameters are set as follows:
Z This is set to the representation of the shared secret Z as an
octet sequence.
keydatalen This is set to the number of bits in the desired output
key. For "ECDH-ES", this is length of the key used by the "enc"
algorithm. For "ECDH-ES+A128KW", "ECDH-ES+A192KW", and
"ECDH-ES+A256KW", this is 128, 192, and 256, respectively.
AlgorithmID The AlgorithmID value is of the form Datalen || Data,
where Data is a variable-length string of zero or more octets, and
Datalen is a fixed-length, big endian 32 bit counter that
indicates the length (in octets) of Data, with || being
concatenation. In the Direct Key Agreement case, Data is set to
the octets of the UTF-8 representation of the "enc" header
parameter value. In the Key Agreement with Key Wrapping case,
Data is set to the octets of the UTF-8 representation of the "alg"
header parameter value.
Jones Expires March 19, 2014 [Page 23]
Internet-Draft JSON Web Algorithms (JWA) September 2013
PartyUInfo The PartyUInfo value is of the form Datalen || Data,
where Data is a variable-length string of zero or more octets, and
Datalen is a fixed-length, big endian 32 bit counter that
indicates the length (in octets) of Data, with || being
concatenation. If an "apu" (agreement PartyUInfo) header
parameter is present, Data is set to the result of base64url
decoding the "apu" value and Datalen is set to the number of
octets in Data. Otherwise, Datalen is set to 0 and Data is set to
the empty octet sequence.
PartyVInfo The PartyVInfo value is of the form Datalen || Data,
where Data is a variable-length string of zero or more octets, and
Datalen is a fixed-length, big endian 32 bit counter that
indicates the length (in octets) of Data, with || being
concatenation. If an "apv" (agreement PartyVInfo) header
parameter is present, Data is set to the result of base64url
decoding the "apv" value and Datalen is set to the number of
octets in Data. Otherwise, Datalen is set to 0 and Data is set to
the empty octet sequence.
SuppPubInfo This is set to the keydatalen represented as a 32 bit
big endian integer.
SuppPrivInfo This is set to the empty octet sequence.
Applications MUST specify what values should be used in the "apu" and
"apv" parameters. The "apu" and "apv" values MUST be distinct.
Applications wishing to conform to [NIST.800-56A] need to provide
values that meet the requirements of that document, e.g., by using
values that identify the sender and recipient. Alternatively,
applications MAY conduct key derivation in a manner similar to The
Diffie-Hellman Key Agreement Method [RFC2631]: In that case, the
"apu" field MAY either be omitted or represent a random 512-bit value
(analogous to PartyAInfo in Ephemeral-Static mode in [RFC2631]) and
the "apv" field should not be present.
See Appendix D for an example key agreement computation using this
method.
4.8. Key Encryption with AES GCM
This section defines the specifics of encrypting a JWE Content
Encryption Key (CEK) with Advanced Encryption Standard (AES) in
Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128, 192, or 256
bit keys. The "alg" header parameter values "A128GCMKW",
"A192GCMKW", or "A256GCMKW" are respectively used in this case.
Use of an Initialization Vector of size 96 bits is REQUIRED with this
Jones Expires March 19, 2014 [Page 24]
Internet-Draft JSON Web Algorithms (JWA) September 2013
algorithm. The Initialization Vector is represented in base64url
encoded form as the "iv" (initialization vector) header parameter
value.
The Additional Authenticated Data value used is the empty octet
string.
The requested size of the Authentication Tag output MUST be 128 bits,
regardless of the key size.
The JWE Encrypted Key value is the Ciphertext output.
The Authentication Tag output is represented in base64url encoded
form as the "tag" (authentication tag) header parameter value.
4.8.1. Header Parameters Used for AES GCM Key Encryption
The following Header Parameters are used for AES GCM key encryption.
4.8.1.1. "iv" (Initialization Vector) Header Parameter
The "iv" (initialization vector) header parameter value is the
base64url encoded representation of the Initialization Vector value
used for the key encryption operation. This Header Parameter is
REQUIRED and MUST be understood and processed by implementations when
these algorithms are used.
4.8.1.2. "tag" (Authentication Tag) Header Parameter
The "tag" (authentication tag) header parameter value is the
base64url encoded representation of the Authentication Tag value
resulting from the key encryption operation. This Header Parameter
is REQUIRED and MUST be understood and processed by implementations
when these algorithms are used.
4.9. Key Encryption with PBES2
The "PBES2-HS256+A128KW", "PBES2-HS384+A192KW", and
"PBES2-HS512+A256KW" composite algorithms are used to perform
password-based encryption of a JWE CEK, by first deriving a key
encryption key from a user-supplied password, then encrypting the JWE
CEK using the derived key. These algorithms are PBES2 schemes as
specified in Section 6.2 of [RFC2898].
These algorithms use HMAC SHA-2 algorithms as the Pseudo-Random
Function (PRF) for the PBKDF2 key derivation and AES Key Wrap
[RFC3394] for the encryption scheme. The salt MUST be provided as
the "p2s" header parameter value, and MUST be base64url decoded to
Jones Expires March 19, 2014 [Page 25]
Internet-Draft JSON Web Algorithms (JWA) September 2013
obtain the value. The iteration count parameter MUST be provided as
the "p2c" header parameter value. The algorithms respectively use
HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 as the PRF and use 128,
192, and 256 bit AES Key Wrap keys. Their derived-key lengths
respectively are 16, 24, and 32 octets.
4.9.1. Header Parameters Used for PBES2 Key Encryption
The following Header Parameters are used for Key Encryption with
PBES2.
4.9.1.1. "p2s" (PBES2 salt) Parameter
The "p2s" (PBES2 salt) header parameter contains the PBKDF2 salt
value, encoded using base64url. This Header Parameter is REQUIRED
and MUST be understood and processed by implementations when these
algorithms are used.
The salt expands the possible keys that can be derived from a given
password. A salt value containing 8 or more octets MUST be used. A
new salt value MUST be generated randomly for every encryption
operation; see [RFC4086] for considerations on generating random
values.
4.9.1.2. "p2c" (PBES2 count) Parameter
The "p2c" (PBES2 count) header parameter contains the PBKDF2
iteration count, represented as a positive integer. This Header
Parameter is REQUIRED and MUST be understood and processed by
implementations when these algorithms are used.
The iteration count adds computational expense, ideally compounded by
the possible range of keys introduced by the salt. A minimum
iteration count of 1000 is RECOMMENDED.
4.10. AES_CBC_HMAC_SHA2 Algorithms
This section defines a family of authenticated encryption algorithms
built using a composition of Advanced Encryption Standard (AES) in
Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES]
[NIST.800-38A] operations and HMAC [RFC2104] [SHS] operations. This
algorithm family is called AES_CBC_HMAC_SHA2. It also defines three
instances of this family, the first using 128 bit CBC keys and HMAC
SHA-256, the second using 192 bit CBC keys and HMAC SHA-384, and the
third using 256 bit CBC keys and HMAC SHA-512. Test cases for these
algorithms can be found in Appendix C.
These algorithms are based upon Authenticated Encryption with AES-CBC
Jones Expires March 19, 2014 [Page 26]
Internet-Draft JSON Web Algorithms (JWA) September 2013
and HMAC-SHA [I-D.mcgrew-aead-aes-cbc-hmac-sha2], performing the same
cryptographic computations, but with the Initialization Vector and
Authentication Tag values remaining separate, rather than being
concatenated with the Ciphertext value in the output representation.
This option is discussed in Appendix B of that specification. This
algorithm family is a generalization of the algorithm family in
[I-D.mcgrew-aead-aes-cbc-hmac-sha2], and can be used to implement
those algorithms.
4.10.1. Conventions Used in Defining AES_CBC_HMAC_SHA2
We use the following notational conventions.
CBC-PKCS5-ENC(X, P) denotes the AES CBC encryption of P using PKCS
#5 padding using the cipher with the key X.
MAC(Y, M) denotes the application of the Message Authentication
Code (MAC) to the message M, using the key Y.
The concatenation of two octet strings A and B is denoted as
A || B.
4.10.2. Generic AES_CBC_HMAC_SHA2 Algorithm
This section defines AES_CBC_HMAC_SHA2 in a manner that is
independent of the AES CBC key size or hash function to be used.
Section 4.10.2.1 and Section 4.10.2.2 define the generic encryption
and decryption algorithms. Section 4.10.3 and Section 4.10.5 define
instances of AES_CBC_HMAC_SHA2 that specify those details.
4.10.2.1. AES_CBC_HMAC_SHA2 Encryption
The authenticated encryption algorithm takes as input four octet
strings: a secret key K, a plaintext P, associated data A, and an
initialization vector IV. The authenticated ciphertext value E and
the authentication tag value T are provided as outputs. The data in
the plaintext are encrypted and authenticated, and the associated
data are authenticated, but not encrypted.
The encryption process is as follows, or uses an equivalent set of
steps:
1. The secondary keys MAC_KEY and ENC_KEY are generated from the
input key K as follows. Each of these two keys is an octet
string.
MAC_KEY consists of the initial MAC_KEY_LEN octets of K, in
order.
Jones Expires March 19, 2014 [Page 27]
Internet-Draft JSON Web Algorithms (JWA) September 2013
ENC_KEY consists of the final ENC_KEY_LEN octets of K, in
order.
Here we denote the number of octets in the MAC_KEY as
MAC_KEY_LEN, and the number of octets in ENC_KEY as ENC_KEY_LEN;
the values of these parameters are specified by the AEAD
algorithms (in Section 4.10.3 and Section 4.10.5). The number of
octets in the input key K is the sum of MAC_KEY_LEN and
ENC_KEY_LEN. When generating the secondary keys from K, MAC_KEY
and ENC_KEY MUST NOT overlap. 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 identifier
"AES_CBC_HMAC_SHA2".
2. The Initialization Vector (IV) used is a 128 bit value generated
randomly or pseudorandomly for use in the cipher.
3. The plaintext is CBC encrypted using PKCS #5 padding using
ENC_KEY as the key, and the IV. We denote the ciphertext output
from this step as E.
4. The octet string AL is equal to the number of bits in A expressed
as a 64-bit unsigned integer in network byte order.
5. A message authentication tag T is computed by applying HMAC
[RFC2104] to the following data, in order:
the associated data A,
the initialization vector IV,
the ciphertext E computed in the previous step, and
the octet string AL defined above.
The string MAC_KEY is used as the MAC key. We denote the output
of the MAC computed in this step as M. The first T_LEN bits of M
are used as T.
6. The Ciphertext E and the Authentication Tag T are returned as the
outputs of the authenticated encryption.
The encryption process can be illustrated as follows. Here K, P, A,
IV, and E denote the key, plaintext, associated data, initialization
vector, and ciphertext, respectively.
MAC_KEY = initial MAC_KEY_LEN bytes of K,
Jones Expires March 19, 2014 [Page 28]
Internet-Draft JSON Web Algorithms (JWA) September 2013
ENC_KEY = final ENC_KEY_LEN bytes of K,
E = CBC-PKCS5-ENC(ENC_KEY, P),
M = MAC(MAC_KEY, A || IV || E || AL),
T = initial T_LEN bytes of M.
4.10.2.2. AES_CBC_HMAC_SHA2 Decryption
The authenticated decryption operation has four inputs: K, A, E, and
T as defined above. It has only a single output, either a plaintext
value P or a special symbol FAIL that indicates that the inputs are
not authentic. The authenticated decryption algorithm is as follows,
or uses an equivalent set of steps:
1. The secondary keys MAC_KEY and ENC_KEY are generated from the
input key K as in Step 1 of Section 4.10.2.1.
2. The integrity and authenticity of A and E are checked by
computing an HMAC with the inputs as in Step 5 of
Section 4.10.2.1. The value T, from the previous step, is
compared to the first MAC_KEY length bits of the HMAC output. If
those values are identical, then A and E are considered valid,
and processing is continued. Otherwise, all of the data used in
the MAC validation are discarded, and the AEAD decryption
operation returns an indication that it failed, and the operation
halts. (But see Section 10 of [JWE] for security considerations
on thwarting timing attacks.)
3. The value E is decrypted and the PKCS #5 padding is removed. The
value IV is used as the initialization vector. The value ENC_KEY
is used as the decryption key.
4. The plaintext value is returned.
4.10.3. AES_128_CBC_HMAC_SHA_256
This algorithm is a concrete instantiation of the generic
AES_CBC_HMAC_SHA2 algorithm above. It uses the HMAC message
authentication code [RFC2104] with the SHA-256 hash function [SHS] to
provide message authentication, with the HMAC output truncated to 128
bits, corresponding to the HMAC-SHA-256-128 algorithm defined in
[RFC4868]. For encryption, it uses AES in the Cipher Block Chaining
(CBC) mode of operation as defined in Section 6.2 of [NIST.800-38A],
with PKCS #5 padding.
The input key K is 32 octets long.
Jones Expires March 19, 2014 [Page 29]
Internet-Draft JSON Web Algorithms (JWA) September 2013
The AES CBC IV is 16 octets long. ENC_KEY_LEN is 16 octets.
The SHA-256 hash algorithm is used in HMAC. MAC_KEY_LEN is 16
octets. The HMAC-SHA-256 output is truncated to T_LEN=16 octets, by
stripping off the final 16 octets.
4.10.4. AES_192_CBC_HMAC_SHA_384
AES_192_CBC_HMAC_SHA_384 is based on AES_128_CBC_HMAC_SHA_256, but
with the following differences:
A 192 bit AES CBC key is used instead of 128.
SHA-384 is used in HMAC instead of SHA-256.
ENC_KEY_LEN is 24 octets instead of 16.
MAC_KEY_LEN is 24 octets instead of 16.
The length of the input key K is 48 octets instead of 32.
The HMAC SHA-384 value is truncated to T_LEN=24 octets instead of
16.
4.10.5. AES_256_CBC_HMAC_SHA_512
AES_256_CBC_HMAC_SHA_512 is based on AES_128_CBC_HMAC_SHA_256, but
with the following differences:
A 256 bit AES CBC key is used instead of 128.
SHA-512 is used in HMAC instead of SHA-256.
ENC_KEY_LEN is 32 octets instead of 16.
MAC_KEY_LEN is 32 octets instead of 16.
The length of the input key K is 64 octets instead of 32.
The HMAC SHA-512 value is truncated to T_LEN=32 octets instead of
16.
4.10.6. Plaintext Encryption with AES_CBC_HMAC_SHA2
The algorithm value "A128CBC-HS256" is used as the "alg" value when
using AES_128_CBC_HMAC_SHA_256 with JWE. The algorithm value
"A192CBC-HS384" is used as the "alg" value when using
AES_192_CBC_HMAC_SHA_384 with JWE. The algorithm value
Jones Expires March 19, 2014 [Page 30]
Internet-Draft JSON Web Algorithms (JWA) September 2013
"A256CBC-HS512" is used as the "alg" value when using
AES_256_CBC_HMAC_SHA_512 with JWE. The Additional Authenticated Data
value used is the octets of the ASCII representation of the Encoded
JWE Header value. The JWE Initialization Vector value used is the IV
value.
4.11. Plaintext Encryption with AES GCM
This section defines the specifics of encrypting the JWE Plaintext
with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM)
[AES] [NIST.800-38D] using 128, 192, or 256 bit keys. The "enc"
header parameter values "A128GCM", "A192GCM", or "A256GCM" are
respectively used in this case.
The CEK is used as the encryption key.
Use of an initialization vector of size 96 bits is REQUIRED with this
algorithm.
The Additional Authenticated Data value used is the octets of the
ASCII representation of the Encoded JWE Header value.
The requested size of the Authentication Tag output MUST be 128 bits,
regardless of the key size.
The JWE Authentication Tag is set to be the Authentication Tag value
produced by the encryption. During decryption, the received JWE
Authentication Tag is used as the Authentication Tag value.
An example using this algorithm is shown in Appendix A.1 of [JWE].
5. Cryptographic Algorithms for Keys
A JSON Web Key (JWK) [JWK] is a JSON data structure that represents a
cryptographic key. These keys can be either asymmetric or symmetric.
They can hold both public and private information about the key.
This section defines the parameters for keys using the algorithms
specified by this document.
5.1. "kty" (Key Type) Parameter Values
The table below is the set of "kty" (key type) parameter values that
are defined by this specification for use in JWKs.
Jones Expires March 19, 2014 [Page 31]
Internet-Draft JSON Web Algorithms (JWA) September 2013
+--------------+--------------------------------+-------------------+
| kty | Key Type | Implementation |
| Parameter | | Requirements |
| Value | | |
+--------------+--------------------------------+-------------------+
| EC | Elliptic Curve [DSS] | Recommended+ |
| RSA | RSA [RFC3447] | Required |
| oct | Octet sequence (used to | Required |
| | represent symmetric keys) | |
+--------------+--------------------------------+-------------------+
The use of "+" in the Implementation Requirements indicates that the
requirement strength is likely to be increased in a future version of
the specification.
5.2. Parameters for Elliptic Curve Keys
JWKs can represent Elliptic Curve [DSS] keys. In this case, the
"kty" member value MUST be "EC".
5.2.1. Parameters for Elliptic Curve Public Keys
An elliptic curve public key is represented by a pair of coordinates
drawn from a finite field, which together define a point on an
elliptic curve. The following members MUST be present for elliptic
curve public keys:
o "crv"
o "x"
o "y"
5.2.1.1. "crv" (Curve) Parameter
The "crv" (curve) member identifies the cryptographic curve used with
the key. Curve values from [DSS] used by this specification are:
o "P-256"
o "P-384"
o "P-521"
These values are registered in the IANA JSON Web Key Elliptic Curve
registry defined in Section 6.6. Additional "crv" values MAY be
used, provided they are understood by implementations using that
Elliptic Curve key. The "crv" value is a case sensitive string.
Jones Expires March 19, 2014 [Page 32]
Internet-Draft JSON Web Algorithms (JWA) September 2013
5.2.1.2. "x" (X Coordinate) Parameter
The "x" (x coordinate) member contains the x coordinate for the
elliptic curve point. It is represented as the base64url encoding of
the octet string representation of the coordinate, as defined in
Section 2.3.5 of SEC1 [SEC1]. The length of this octet string MUST
be the full size of a coordinate for the curve specified in the "crv"
parameter. For example, if the value of "crv" is "P-521", the octet
string must be 66 octets long.
5.2.1.3. "y" (Y Coordinate) Parameter
The "y" (y coordinate) member contains the y coordinate for the
elliptic curve point. It is represented as the base64url encoding of
the octet string representation of the coordinate, as defined in
Section 2.3.5 of SEC1 [SEC1]. The length of this octet string MUST
be the full size of a coordinate for the curve specified in the "crv"
parameter. For example, if the value of "crv" is "P-521", the octet
string must be 66 octets long.
5.2.2. Parameters for Elliptic Curve Private Keys
In addition to the members used to represent Elliptic Curve public
keys, the following member MUST be present to represent Elliptic
Curve private keys.
5.2.2.1. "d" (ECC Private Key) Parameter
The "d" (ECC private key) member contains the Elliptic Curve private
key value. It is represented as the base64url encoding of the octet
string representation of the private key value, as defined in
Sections C.4 and 2.3.7 of SEC1 [SEC1]. The length of this octet
string MUST be ceiling(log-base-2(n)/8) octets (where n is the order
of the curve).
5.3. Parameters for RSA Keys
JWKs can represent RSA [RFC3447] keys. In this case, the "kty"
member value MUST be "RSA".
5.3.1. Parameters for RSA Public Keys
The following members MUST be present for RSA public keys.
5.3.1.1. "n" (Modulus) Parameter
The "n" (modulus) member contains the modulus value for the RSA
public key. It is represented as the base64url encoding of the
Jones Expires March 19, 2014 [Page 33]
Internet-Draft JSON Web Algorithms (JWA) September 2013
value's unsigned big endian representation as an octet sequence. The
octet sequence MUST utilize the minimum number of octets to represent
the value.
5.3.1.2. "e" (Exponent) Parameter
The "e" (exponent) member contains the exponent value for the RSA
public key. It is represented as the base64url encoding of the
value's unsigned big endian representation as an octet sequence. The
octet sequence MUST utilize the minimum number of octets to represent
the value. For instance, when representing the value 65537, the
octet sequence to be base64url encoded MUST consist of the three
octets [1, 0, 1].
5.3.2. Parameters for RSA Private Keys
In addition to the members used to represent RSA public keys, the
following members are used to represent RSA private keys. The
parameter "d" is REQUIRED for RSA private keys. The others enable
optimizations and SHOULD be included by producers of JWKs
representing RSA private keys. If the producer includes any of the
other private key parameters, then all of the others MUST be present,
with the exception of "oth", which MUST only be present when more
than two prime factors were used. The consumer of a JWK MAY choose
to accept an RSA private key that does not contain a complete set of
the private key parameters other than "d", including JWKs in which
"d" is the only RSA private key parameter included.
5.3.2.1. "d" (Private Exponent) Parameter
The "d" (private exponent) member contains the private exponent value
for the RSA private key. It is represented as the base64url encoding
of the value's unsigned big endian representation as an octet
sequence. The octet sequence MUST utilize the minimum number of
octets to represent the value.
5.3.2.2. "p" (First Prime Factor) Parameter
The "p" (first prime factor) member contains the first prime factor,
a positive integer. It is represented as the base64url encoding of
the value's unsigned big endian representation as an octet sequence.
The octet sequence MUST utilize the minimum number of octets to
represent the value.
5.3.2.3. "q" (Second Prime Factor) Parameter
The "q" (second prime factor) member contains the second prime
factor, a positive integer. It is represented as the base64url
Jones Expires March 19, 2014 [Page 34]
Internet-Draft JSON Web Algorithms (JWA) September 2013
encoding of the value's unsigned big endian representation as an
octet sequence. The octet sequence MUST utilize the minimum number
of octets to represent the value.
5.3.2.4. "dp" (First Factor CRT Exponent) Parameter
The "dp" (first factor CRT exponent) member contains the Chinese
Remainder Theorem (CRT) exponent of the first factor, a positive
integer. It is represented as the base64url encoding of the value's
unsigned big endian representation as an octet sequence. The octet
sequence MUST utilize the minimum number of octets to represent the
value.
5.3.2.5. "dq" (Second Factor CRT Exponent) Parameter
The "dq" (second factor CRT exponent) member contains the Chinese
Remainder Theorem (CRT) exponent of the second factor, a positive
integer. It is represented as the base64url encoding of the value's
unsigned big endian representation as an octet sequence. The octet
sequence MUST utilize the minimum number of octets to represent the
value.
5.3.2.6. "qi" (First CRT Coefficient) Parameter
The "dp" (first CRT coefficient) member contains the Chinese
Remainder Theorem (CRT) coefficient of the second factor, a positive
integer. It is represented as the base64url encoding of the value's
unsigned big endian representation as an octet sequence. The octet
sequence MUST utilize the minimum number of octets to represent the
value.
5.3.2.7. "oth" (Other Primes Info) Parameter
The "oth" (other primes info) member contains an array of information
about any third and subsequent primes, should they exist. When only
two primes have been used (the normal case), this parameter MUST be
omitted. When three or more primes have been used, the number of
array elements MUST be the number of primes used minus two. Each
array element MUST be an object with the following members:
5.3.2.7.1. "r" (Prime Factor)
The "r" (prime factor) parameter within an "oth" array member
represents the value of a subsequent prime factor, a positive
integer. It is represented as the base64url encoding of the value's
unsigned big endian representation as an octet sequence. The octet
sequence MUST utilize the minimum number of octets to represent the
value.
Jones Expires March 19, 2014 [Page 35]
Internet-Draft JSON Web Algorithms (JWA) September 2013
5.3.2.7.2. "d" (Factor CRT Exponent)
The "d" (Factor CRT Exponent) parameter within an "oth" array member
represents the CRT exponent of the corresponding prime factor, a
positive integer. It is represented as the base64url encoding of the
value's unsigned big endian representation as an octet sequence. The
octet sequence MUST utilize the minimum number of octets to represent
the value.
5.3.2.7.3. "t" (Factor CRT Coefficient)
The "t" (factor CRT coefficient) parameter within an "oth" array
member represents the CRT coefficient of the corresponding prime
factor, a positive integer. It is represented as the base64url
encoding of the value's unsigned big endian representation as an
octet sequence. The octet sequence MUST utilize the minimum number
of octets to represent the value.
5.4. Parameters for Symmetric Keys
When the JWK "kty" member value is "oct" (octet sequence), the member
"k" is used to represent a symmetric key (or another key whose value
is a single octet sequence). An "alg" member SHOULD also be present
to identify the algorithm intended to be used with the key, unless
the application uses another means or convention to determine the
algorithm used.
5.4.1. "k" (Key Value) Parameter
The "k" (key value) member contains the value of the symmetric (or
other single-valued) key. It is represented as the base64url
encoding of the octet sequence containing the key value.
6. IANA Considerations
The following registration procedure is used for all the registries
established by this specification.
Values are registered with a Specification Required [RFC5226] after a
two-week review period on the [TBD]@ietf.org mailing list, on the
advice of one or more Designated Experts. However, to allow for the
allocation of values prior to publication, the Designated Expert(s)
may approve registration once they are satisfied that such a
specification will be published.
Registration requests must be sent to the [TBD]@ietf.org mailing list
for review and comment, with an appropriate subject (e.g., "Request
Jones Expires March 19, 2014 [Page 36]
Internet-Draft JSON Web Algorithms (JWA) September 2013
for access token type: example"). [[ Note to the RFC Editor: The name
of the mailing list should be determined in consultation with the
IESG and IANA. Suggested name: jose-reg-review. ]]
Within the review period, the Designated Expert(s) will either
approve or deny the registration request, communicating this decision
to the review list and IANA. Denials should include an explanation
and, if applicable, suggestions as to how to make the request
successful. Registration requests that are undetermined for a period
longer than 21 days can be brought to the IESG's attention (using the
iesg@iesg.org mailing list) for resolution.
Criteria that should be applied by the Designated Expert(s) includes
determining whether the proposed registration duplicates existing
functionality, determining whether it is likely to be of general
applicability or whether it is useful only for a single application,
and whether the registration makes sense.
IANA must only accept registry updates from the Designated Expert(s)
and should direct all requests for registration to the review mailing
list.
It is suggested that multiple Designated Experts be appointed who are
able to represent the perspectives of different applications using
this specification, in order to enable broadly-informed review of
registration decisions. In cases where a registration decision could
be perceived as creating a conflict of interest for a particular
Expert, that Expert should defer to the judgment of the other
Expert(s).
6.1. JSON Web Signature and Encryption Algorithms Registry
This specification establishes the IANA JSON Web Signature and
Encryption Algorithms registry for values of the JWS and JWE "alg"
(algorithm) and "enc" (encryption method) header parameters. The
registry records the algorithm name, the algorithm usage locations
from the set "alg" and "enc", implementation requirements, and a
reference to the specification that defines it. The same algorithm
name MAY be registered multiple times, provided that the sets of
usage locations are disjoint.
It is suggested that when algorithms can use keys of different
lengths, that the length of the key be included in the algorithm
name. This allows readers of the JSON text to easily make security
consideration decisions.
The implementation requirements of an algorithm MAY be changed over
time by the Designated Experts(s) as the cryptographic landscape
Jones Expires March 19, 2014 [Page 37]
Internet-Draft JSON Web Algorithms (JWA) September 2013
evolves, for instance, to change the status of an algorithm to
Deprecated, or to change the status of an algorithm from Optional to
Recommended+ or Required. Changes of implementation requirements are
only permitted on a Specification Required basis, with the new
specification defining the revised implementation requirements level.
6.1.1. Template
Algorithm Name:
The name requested (e.g., "example"). This name is case
sensitive. Names may not match other registered names in a case
insensitive manner unless the Designated Expert(s) state that
there is a compelling reason to allow an exception in this
particular case.
Algorithm Usage Location(s):
The algorithm usage, which must be one or more of the values "alg"
or "enc".
Implementation Requirements:
The algorithm implementation requirements, which must be one the
words Required, Recommended, Optional, or Deprecated. Optionally,
the word can be followed by a "+" or "-". The use of "+"
indicates that the requirement strength is likely to be increased
in a future version of the specification. The use of "-"
indicates that the requirement strength is likely to be decreased
in a future version of the specification.
Change Controller:
For Standards Track RFCs, state "IESG". For others, give the name
of the responsible party. Other details (e.g., postal address,
email address, home page URI) may also be included.
Specification Document(s):
Reference to the document(s) that specify the parameter,
preferably including URI(s) that can be used to retrieve copies of
the document(s). An indication of the relevant sections may also
be included but is not required.
6.1.2. Initial Registry Contents
o Algorithm Name: "HS256"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
Jones Expires March 19, 2014 [Page 38]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Algorithm Name: "HS384"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "HS512"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "RS256"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "RS384"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "RS512"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "ES256"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "ES384"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "ES512"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
Jones Expires March 19, 2014 [Page 39]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "PS256"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "PS384"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "PS512"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "none"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [[ this document ]]
o Algorithm Name: "RSA1_5"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "RSA-OAEP"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "A128KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "A192KW"
o Algorithm Usage Location(s): "alg"
Jones Expires March 19, 2014 [Page 40]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "A256KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "dir"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "ECDH-ES"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "ECDH-ES+A128KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "ECDH-ES+A192KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "ECDH-ES+A256KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this document ]]
o Algorithm Name: "A128GCMKW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of [[ this document ]]
Jones Expires March 19, 2014 [Page 41]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Algorithm Name: "A192GCMKW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of [[ this document ]]
o Algorithm Name: "A256GCMKW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of [[ this document ]]
o Algorithm Name: "PBES2-HS256+A128KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.9 of [[ this document ]]
o Algorithm Name: "PBES2-HS384+A192KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.9 of [[ this document ]]
o Algorithm Name: "PBES2-HS512+A256KW"
o Algorithm Usage Location(s): "alg"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.9 of [[ this document ]]
o Algorithm Name: "A128CBC-HS256"
o Algorithm Usage Location(s): "enc"
o Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 4.2 of [[ this document ]]
o Algorithm Name: "A192CBC-HS384"
o Algorithm Usage Location(s): "enc"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.2 of [[ this document ]]
o Algorithm Name: "A256CBC-HS512"
o Algorithm Usage Location(s): "enc"
o Implementation Requirements: Required
o Change Controller: IESG
Jones Expires March 19, 2014 [Page 42]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Specification Document(s): Section 4.2 of [[ this document ]]
o Algorithm Name: "A128GCM"
o Algorithm Usage Location(s): "enc"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.2 of [[ this document ]]
o Algorithm Name: "A192GCM"
o Algorithm Usage Location(s): "enc"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.2 of [[ this document ]]
o Algorithm Name: "A256GCM"
o Algorithm Usage Location(s): "enc"
o Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.2 of [[ this document ]]
6.2. JWE Header Parameter Names Registration
This specification registers the Header Parameter Names defined in
Section 4.7.1, Section 4.8.1, and Section 4.9.1 in the IANA JSON Web
Signature and Encryption Header Parameters registry defined in [JWS].
6.2.1. Registry Contents
o Header Parameter Name: "epk"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.1 of [[ this document ]]
o Header Parameter Name: "apu"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.2 of [[ this document ]]
o Header Parameter Name: "apv"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.3 of [[ this document ]]
o Header Parameter Name: "iv"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
Jones Expires March 19, 2014 [Page 43]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Specification Document(s): Section 4.8.1.1 of [[ this document ]]
o Header Parameter Name: "tag"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.8.1.2 of [[ this document ]]
o Header Parameter Name: "p2s"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.9.1.1 of [[ this document ]]
o Header Parameter Name: "p2c"
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.9.1.2 of [[ this document ]]
6.3. JSON Web Encryption Compression Algorithms Registry
This specification establishes the IANA JSON Web Encryption
Compression Algorithms registry for JWE "zip" member values. The
registry records the compression algorithm value and a reference to
the specification that defines it.
6.3.1. Registration Template
Compression Algorithm Value:
The name requested (e.g., "example"). Because a core goal of this
specification is for the resulting representations to be compact,
it is RECOMMENDED that the name be short -- not to exceed 8
characters without a compelling reason to do so. This name is
case sensitive. Names may not match other registered names in a
case insensitive manner unless the Designated Expert(s) state that
there is a compelling reason to allow an exception in this
particular case.
Change Controller:
For Standards Track RFCs, state "IESG". For others, give the name
of the responsible party. Other details (e.g., postal address,
email address, home page URI) may also be included.
Specification Document(s):
Reference to the document(s) that specify the parameter,
preferably including URI(s) that can be used to retrieve copies of
the document(s). An indication of the relevant sections may also
be included but is not required.
Jones Expires March 19, 2014 [Page 44]
Internet-Draft JSON Web Algorithms (JWA) September 2013
6.3.2. Initial Registry Contents
o Compression Algorithm Value: "DEF"
o Change Controller: IESG
o Specification Document(s): JSON Web Encryption (JWE) [JWE]
6.4. JSON Web Key Types Registry
This specification establishes the IANA JSON Web Key Types registry
for values of the JWK "kty" (key type) parameter. The registry
records the "kty" value, implementation requirements, and a reference
to the specification that defines it.
The implementation requirements of a key type MAY be changed over
time by the Designated Experts(s) as the cryptographic landscape
evolves, for instance, to change the status of a key type to
Deprecated, or to change the status of a key type from Optional to
Recommended+ or Required. Changes of implementation requirements are
only permitted on a Specification Required basis, with the new
specification defining the revised implementation requirements level.
6.4.1. Registration Template
"kty" Parameter Value:
The name requested (e.g., "example"). Because a core goal of this
specification is for the resulting representations to be compact,
it is RECOMMENDED that the name be short -- not to exceed 8
characters without a compelling reason to do so. This name is
case sensitive. Names may not match other registered names in a
case insensitive manner unless the Designated Expert(s) state that
there is a compelling reason to allow an exception in this
particular case.
Change Controller:
For Standards Track RFCs, state "IESG". For others, give the name
of the responsible party. Other details (e.g., postal address,
email address, home page URI) may also be included.
Implementation Requirements:
The key type implementation requirements, which must be one the
words Required, Recommended, Optional, or Deprecated. Optionally,
the word can be followed by a "+" or "-". The use of "+"
indicates that the requirement strength is likely to be increased
in a future version of the specification. The use of "-"
indicates that the requirement strength is likely to be decreased
in a future version of the specification.
Jones Expires March 19, 2014 [Page 45]
Internet-Draft JSON Web Algorithms (JWA) September 2013
Specification Document(s):
Reference to the document(s) that specify the parameter,
preferably including URI(s) that can be used to retrieve copies of
the document(s). An indication of the relevant sections may also
be included but is not required.
6.4.2. Initial Registry Contents
This specification registers the values defined in Section 5.1.
o "kty" Parameter Value: "EC"
o Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 5.2 of [[ this document ]]
o "kty" Parameter Value: "RSA"
o Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 5.3 of [[ this document ]]
o "kty" Parameter Value: "oct"
o Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 5.4 of [[ this document ]]
6.5. JSON Web Key Parameters Registration
This specification registers the parameter names defined in Sections
5.2, 5.3, and 5.4 in the IANA JSON Web Key Parameters registry
defined in [JWK].
6.5.1. Registry Contents
o Parameter Name: "crv"
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 5.2.1.1 of [[ this document ]]
o Parameter Name: "x"
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 5.2.1.2 of [[ this document ]]
o Parameter Name: "y"
Jones Expires March 19, 2014 [Page 46]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 5.2.1.3 of [[ this document ]]
o Parameter Name: "d"
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.2.2.1 of [[ this document ]]
o Parameter Name: "n"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 5.3.1.1 of [[ this document ]]
o Parameter Name: "e"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 5.3.1.2 of [[ this document ]]
o Parameter Name: "d"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.1 of [[ this document ]]
o Parameter Name: "p"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.2 of [[ this document ]]
o Parameter Name: "q"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.3 of [[ this document ]]
o Parameter Name: "dp"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.4 of [[ this document ]]
Jones Expires March 19, 2014 [Page 47]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Parameter Name: "dq"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.5 of [[ this document ]]
o Parameter Name: "qi"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.6 of [[ this document ]]
o Parameter Name: "oth"
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.3.2.7 of [[ this document ]]
o Parameter Name: "k"
o Used with "kty" Value(s): "oct"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 5.4.1 of [[ this document ]]
6.6. JSON Web Key Elliptic Curve Registry
This specification establishes the IANA JSON Web Key Elliptic Curve
registry for JWK "crv" member values. The registry records the curve
name, implementation requirements, and a reference to the
specification that defines it. This specification registers the
parameter names defined in Section 5.2.1.1.
The implementation requirements of a curve MAY be changed over time
by the Designated Experts(s) as the cryptographic landscape evolves,
for instance, to change the status of a curve to Deprecated, or to
change the status of a curve from Optional to Recommended+ or
Required. Changes of implementation requirements are only permitted
on a Specification Required basis, with the new specification
defining the revised implementation requirements level.
6.6.1. Registration Template
Curve Name:
The name requested (e.g., "example"). Because a core goal of this
specification is for the resulting representations to be compact,
it is RECOMMENDED that the name be short -- not to exceed 8
characters without a compelling reason to do so. This name is
case sensitive. Names may not match other registered names in a
Jones Expires March 19, 2014 [Page 48]
Internet-Draft JSON Web Algorithms (JWA) September 2013
case insensitive manner unless the Designated Expert(s) state that
there is a compelling reason to allow an exception in this
particular case.
Implementation Requirements:
The curve implementation requirements, which must be one the words
Required, Recommended, Optional, or Deprecated. Optionally, the
word can be followed by a "+" or "-". The use of "+" indicates
that the requirement strength is likely to be increased in a
future version of the specification. The use of "-" indicates
that the requirement strength is likely to be decreased in a
future version of the specification.
Change Controller:
For Standards Track RFCs, state "IESG". For others, give the name
of the responsible party. Other details (e.g., postal address,
email address, home page URI) may also be included.
Specification Document(s):
Reference to the document(s) that specify the parameter,
preferably including URI(s) that can be used to retrieve copies of
the document(s). An indication of the relevant sections may also
be included but is not required.
6.6.2. Initial Registry Contents
o Curve Name: "P-256"
o Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 5.2.1.1 of [[ this document ]]
o Curve Name: "P-384"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 5.2.1.1 of [[ this document ]]
o Curve Name: "P-521"
o Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 5.2.1.1 of [[ this document ]]
7. Security Considerations
All of the security issues faced by any cryptographic application
must be faced by a JWS/JWE/JWK agent. Among these issues are
protecting the user's private and symmetric keys, preventing various
attacks, and helping the user avoid mistakes such as inadvertently
Jones Expires March 19, 2014 [Page 49]
Internet-Draft JSON Web Algorithms (JWA) September 2013
encrypting a message for the wrong recipient. The entire list of
security considerations is beyond the scope of this document, but
some significant considerations are listed here.
The security considerations in [AES], [DSS], [JWE], [JWK], [JWS],
[NIST.800-38A], [NIST.800-38D], [NIST.800-56A], [RFC2104], [RFC3394],
[RFC3447], [RFC5116], [RFC6090], and [SHS] apply to this
specification.
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.
7.1. Algorithms and Key Sizes will be Deprecated
Eventually the algorithms and/or key sizes currently described in
this specification will no longer be considered sufficiently secure
and will be removed. Therefore, implementers and deployments must be
prepared for this eventuality.
7.2. Key Lifetimes
Many algorithms have associated security considerations related to
key lifetimes and/or the number of times that a key may be used.
Those security considerations continue to apply when using those
algorithms with JOSE data structures.
7.3. RSAES-PKCS1-v1_5 Security Considerations
While Section 8 of RFC 3447 [RFC3447] explicitly calls for people not
to adopt RSASSA-PKCS-v1_5 for new applications and instead requests
that people transition to RSASSA-PSS, this specification does include
RSASSA-PKCS-v1_5, for interoperability reasons, because it commonly
implemented.
Keys used with RSAES-PKCS1-v1_5 must follow the constraints in
Section 7.2 of RFC 3447 [RFC3447]. In particular, keys with a low
public key exponent value must not be used.
7.4. AES GCM Security Considerations
Keys used with AES GCM must follow the constraints in Section 8.3 of
[NIST.800-38D], which states: "The total number of invocations of the
authenticated encryption function shall not exceed 2^32, including
all IV lengths and all instances of the authenticated encryption
function with the given key". In accordance with this rule, AES GCM
MUST NOT be used with the same key value more than 2^32 times.
Jones Expires March 19, 2014 [Page 50]
Internet-Draft JSON Web Algorithms (JWA) September 2013
An Initialization Vector value MUST never be used multiple times with
the same AES GCM key. One way to prevent this is to store a counter
with the key and increment it with every use. The counter can also
be used to prevent exceeding the 2^32 limit above.
This security consideration does not apply to the composite AES-CBC
HMAC SHA-2 or AES Key Wrap algorithms.
7.5. Plaintext JWS Security Considerations
Plaintext JWSs (JWSs that use the "alg" value "none") provide no
integrity protection. Thus, they must only be used in contexts where
the payload is secured by means other than a digital signature or MAC
value, or need not be secured.
Implementations that support plaintext JWS objects MUST NOT accept
such objects as valid unless the application specifies that it is
acceptable for a specific object to not be integrity-protected.
Implementations MUST NOT accept plaintext JWS objects by default.
For example, the "verify" method of a hypothetical JWS software
library might have a Boolean "acceptUnsigned" parameter that
indicates "none" is an acceptable "alg" value. As another example,
the "verify" method might take a list of algorithms that are
acceptable to the application as a parameter and would reject
plaintext JWS values if "none" is not in that list.
In order to mitigate downgrade attacks, applications MUST NOT signal
acceptance of plaintext JWS objects at a global level, and SHOULD
signal acceptance on a per-object basis. For example, suppose an
application accepts JWS objects over two channels, (1) HTTP and (2)
HTTPS with client authentication. It requires a JWS signature on
objects received over HTTP, but accepts plaintext JWS objects over
HTTPS. If the application were to globally indicate that "none" is
acceptable, then an attacker could provide it with an unsigned object
over HTTP and still have that object successfully validate. Instead,
the application needs to indicate acceptance of "none" for each
object received over HTTPS (e.g., by setting "acceptUnsigned" to
"true" for the first hypothetical JWS software library above), but
not for each object received over HTTP.
7.6. Denial of Service Attacks
Receiving agents that validate signatures and sending agents that
encrypt messages need to be cautious of cryptographic processing
usage when validating signatures and encrypting messages using keys
larger than those mandated in this specification. An attacker could
send certificates with keys that would result in excessive
cryptographic processing, for example, keys larger than those
Jones Expires March 19, 2014 [Page 51]
Internet-Draft JSON Web Algorithms (JWA) September 2013
mandated in this specification, which could swamp the processing
element. Agents that use such keys without first validating the
certificate to a trust anchor are advised to have some sort of
cryptographic resource management system to prevent such attacks.
7.7. Reusing Key Material when Encrypting Keys
It is NOT RECOMMENDED to reuse the same key material (Key Encryption
Key, Content Encryption Key, Initialization Vector, etc.) to encrypt
multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK
Set object multiple times. One suggestion for preventing re-use is
to always generate a new set key material for each encryption
operation, based on the considerations noted in this document as well
as from [RFC4086].
7.8. Password Considerations
While convenient for end users, passwords are vulnerable to a number
of attacks. To help mitigate some of these limitations, this
document applies principles from [RFC2898] to derive cryptographic
keys from user-supplied passwords.
However, the strength of the password still has a significant impact.
A high-entry password has greater resistance to dictionary attacks.
[NIST-800-63-1] contains guidelines for estimating password entropy,
which can help applications and users generate stronger passwords.
An ideal password is one that is as large (or larger) than the
derived key length but less than the PRF's block size. Passwords
larger than the PRF's block size are first hashed, which reduces an
attacker's effective search space to the length of the hash algorithm
(32 octets for HMAC SHA-256). It is RECOMMENDED that the password be
no longer than 64 octets long for "PBES2-HS512+A256KW".
Still, care needs to be taken in where and how password-based
encryption is used. Such algorithms MUST NOT be used where the
attacker can make an indefinite number of attempts to circumvent the
protection.
8. Internationalization Considerations
Passwords obtained from users are likely to require preparation and
normalization to account for differences of octet sequences generated
by different input devices, locales, etc. It is RECOMMENDED that
applications to perform the steps outlined in
[I-D.melnikov-precis-saslprepbis] to prepare a password supplied
directly by a user before performing key derivation and encryption.
Jones Expires March 19, 2014 [Page 52]
Internet-Draft JSON Web Algorithms (JWA) September 2013
9. References
9.1. Normative References
[AES] National Institute of Standards and Technology (NIST),
"Advanced Encryption Standard (AES)", FIPS PUB 197,
November 2001.
[DSS] National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", FIPS PUB 186-4, July 2013.
[I-D.melnikov-precis-saslprepbis]
Saint-Andre, P. and A. Melnikov, "Preparation and
Comparison of Internationalized Strings Representing
Simple User Names and Passwords",
draft-melnikov-precis-saslprepbis-04 (work in progress),
September 2012.
[JWE] Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
Encryption (JWE)", draft-ietf-jose-json-web-encryption
(work in progress), September 2013.
[JWK] Jones, M., "JSON Web Key (JWK)",
draft-ietf-jose-json-web-key (work in progress),
September 2013.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", draft-ietf-jose-json-web-signature (work
in progress), September 2013.
[NIST.800-38A]
National Institute of Standards and Technology (NIST),
"Recommendation for Block Cipher Modes of Operation",
NIST PUB 800-38A, December 2001.
[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,
December 2001.
[NIST.800-56A]
National Institute of Standards and Technology (NIST),
"Recommendation for Pair-Wise Key Establishment Schemes
Using Discrete Logarithm Cryptography", NIST Special
Publication 800-56A, Revision 2, May 2013.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Jones Expires March 19, 2014 [Page 53]
Internet-Draft JSON Web Algorithms (JWA) September 2013
Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography
Specification Version 2.0", RFC 2898, September 2000.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, September 2002.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, January 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090, February 2011.
[SEC1] Standards for Efficient Cryptography Group, "SEC 1:
Elliptic Curve Cryptography", May 2009.
[SHS] National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", FIPS PUB 180-3, October 2008.
[USASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
Jones Expires March 19, 2014 [Page 54]
Internet-Draft JSON Web Algorithms (JWA) September 2013
9.2. Informative References
[CanvasApp]
Facebook, "Canvas Applications", 2010.
[I-D.mcgrew-aead-aes-cbc-hmac-sha2]
McGrew, D., Foley, J., and K. Paterson, "Authenticated
Encryption with AES-CBC and HMAC-SHA",
draft-mcgrew-aead-aes-cbc-hmac-sha2-02 (work in progress),
July 2013.
[I-D.miller-jose-jwe-protected-jwk]
Miller, M., "Using JavaScript Object Notation (JSON) Web
Encryption (JWE) for Protecting JSON Web Key (JWK)
Objects", draft-miller-jose-jwe-protected-jwk-02 (work in
progress), June 2013.
[I-D.rescorla-jsms]
Rescorla, E. and J. Hildebrand, "JavaScript Message
Security Format", draft-rescorla-jsms-00 (work in
progress), March 2011.
[JCA] Oracle, "Java Cryptography Architecture", 2013.
[JSE] Bradley, J. and N. Sakimura (editor), "JSON Simple
Encryption", September 2010.
[JSS] Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
September 2010.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
Signatures", January 2011.
[NIST-800-63-1]
National Institute of Standards and Technology (NIST),
"Electronic Authentication Guideline", NIST 800-63-1,
December 2011.
[RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method",
RFC 2631, June 1999.
[RFC3275] Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup
Language) XML-Signature Syntax and Processing", RFC 3275,
March 2002.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Jones Expires March 19, 2014 [Page 55]
Internet-Draft JSON Web Algorithms (JWA) September 2013
Version 2.1", RFC 3447, February 2003.
[W3C.CR-xmldsig-core2-20120124]
Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P.,
Hirsch, F., Cantor, S., and T. Roessler, "XML Signature
Syntax and Processing Version 2.0", World Wide Web
Consortium CR CR-xmldsig-core2-20120124, January 2012,
<http://www.w3.org/TR/2012/CR-xmldsig-core2-20120124>.
[W3C.CR-xmlenc-core1-20120313]
Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch,
"XML Encryption Syntax and Processing Version 1.1", World
Wide Web Consortium CR CR-xmlenc-core1-20120313,
March 2012,
<http://www.w3.org/TR/2012/CR-xmlenc-core1-20120313>.
[W3C.REC-xmlenc-core-20021210]
Eastlake, D. and J. Reagle, "XML Encryption Syntax and
Processing", World Wide Web Consortium Recommendation REC-
xmlenc-core-20021210, December 2002,
<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.
Appendix A. Digital Signature/MAC Algorithm Identifier Cross-Reference
This appendix contains a table cross-referencing the digital
signature and MAC "alg" (algorithm) values used in this specification
with the equivalent identifiers used by other standards and software
packages. See XML DSIG [RFC3275], XML DSIG 2.0
[W3C.CR-xmldsig-core2-20120124], and Java Cryptography Architecture
[JCA] for more information about the names defined by those
documents.
+-----+---------------------------------+-----------+---------------+
| JWS | XML DSIG | JCA | OID |
+-----+---------------------------------+-----------+---------------+
| HS2 | http://www.w3.org/2001/04/xmlds | HmacSHA25 | 1.2.840.11354 |
| 56 | ig-more#hmac-sha256 | 6 | 9.2.9 |
| HS3 | http://www.w3.org/2001/04/xmlds | HmacSHA38 | 1.2.840.11354 |
| 84 | ig-more#hmac-sha384 | 4 | 9.2.10 |
| HS5 | http://www.w3.org/2001/04/xmlds | HmacSHA51 | 1.2.840.11354 |
| 12 | ig-more#hmac-sha512 | 2 | 9.2.11 |
| RS2 | http://www.w3.org/2001/04/xmlds | SHA256wit | 1.2.840.11354 |
| 56 | ig-more#rsa-sha256 | hRSA | 9.1.1.11 |
| RS3 | http://www.w3.org/2001/04/xmlds | SHA384wit | 1.2.840.11354 |
| 84 | ig-more#rsa-sha384 | hRSA | 9.1.1.12 |
| RS5 | http://www.w3.org/2001/04/xmlds | SHA512wit | 1.2.840.11354 |
| 12 | ig-more#rsa-sha512 | hRSA | 9.1.1.13 |
Jones Expires March 19, 2014 [Page 56]
Internet-Draft JSON Web Algorithms (JWA) September 2013
| ES2 | http://www.w3.org/2001/04/xmlds | SHA256wit | 1.2.840.10045 |
| 56 | ig-more#ecdsa-sha256 | hECDSA | .4.3.2 |
| ES3 | http://www.w3.org/2001/04/xmlds | SHA384wit | 1.2.840.10045 |
| 84 | ig-more#ecdsa-sha384 | hECDSA | .4.3.3 |
| ES5 | http://www.w3.org/2001/04/xmlds | SHA512wit | 1.2.840.10045 |
| 12 | ig-more#ecdsa-sha512 | hECDSA | .4.3.4 |
| PS2 | http://www.w3.org/2007/05/xmlds | | 1.2.840.11354 |
| 56 | ig-more#sha256-rsa-MGF1 | | 9.1.1.10 |
| PS3 | http://www.w3.org/2007/05/xmlds | | 1.2.840.11354 |
| 84 | ig-more#sha384-rsa-MGF1 | | 9.1.1.10 |
| PS5 | http://www.w3.org/2007/05/xmlds | | 1.2.840.11354 |
| 12 | ig-more#sha512-rsa-MGF1 | | 9.1.1.10 |
+-----+---------------------------------+-----------+---------------+
Appendix B. Encryption Algorithm Identifier Cross-Reference
This appendix contains a table cross-referencing the "alg"
(algorithm) and "enc" (encryption method) values used in this
specification with the equivalent identifiers used by other standards
and software packages. See XML Encryption
[W3C.REC-xmlenc-core-20021210], XML Encryption 1.1
[W3C.CR-xmlenc-core1-20120313], and Java Cryptography Architecture
[JCA] for more information about the names defined by those
documents.
For the composite algorithms "A128CBC-HS256", "A192CBC-HS384", and
"A256CBC-HS512", the corresponding AES CBC algorithm identifiers are
listed.
+--------+-----------------------+-------------------+--------------+
| JWE | XML ENC | JCA | OID |
+--------+-----------------------+-------------------+--------------+
| RSA1_5 | http://www.w3.org/200 | RSA/ECB/PKCS1Padd | 1.2.840.1135 |
| | 1/04/xmlenc#rsa-1_5 | ing | 49.1.1.1 |
| RSA-OA | http://www.w3.org/200 | RSA/ECB/OAEPWithS | 1.2.840.1135 |
| EP | 1/04/xmlenc#rsa-oaep- | HA-1AndMGF1Paddin | 49.1.1.7 |
| | mgf1p | g | |
| ECDH-E | http://www.w3.org/200 | | 1.3.132.1.12 |
| S | 9/xmlenc11#ECDH-ES | | |
| A128KW | http://www.w3.org/200 | | 2.16.840.1.1 |
| | 1/04/xmlenc#kw-aes128 | | 01.3.4.1.5 |
| A192KW | http://www.w3.org/200 | | 2.16.840.1.1 |
| | 1/04/xmlenc#kw-aes192 | | 01.3.4.1.25 |
| A256KW | http://www.w3.org/200 | | 2.16.840.1.1 |
| | 1/04/xmlenc#kw-aes256 | | 01.3.4.1.45 |
Jones Expires March 19, 2014 [Page 57]
Internet-Draft JSON Web Algorithms (JWA) September 2013
| A128CB | http://www.w3.org/200 | AES/CBC/PKCS5Padd | 2.16.840.1.1 |
| C-HS25 | 1/04/xmlenc#aes128-cb | ing | 01.3.4.1.2 |
| 6 | c | | |
| A192CB | http://www.w3.org/200 | AES/CBC/PKCS5Padd | 2.16.840.1.1 |
| C-HS38 | 1/04/xmlenc#aes192-cb | ing | 01.3.4.1.22 |
| 4 | c | | |
| A256CB | http://www.w3.org/200 | AES/CBC/PKCS5Padd | 2.16.840.1.1 |
| C-HS51 | 1/04/xmlenc#aes256-cb | ing | 01.3.4.1.42 |
| 2 | c | | |
| A128GC | http://www.w3.org/200 | AES/GCM/NoPadding | 2.16.840.1.1 |
| M | 9/xmlenc11#aes128-gcm | | 01.3.4.1.6 |
| A192GC | http://www.w3.org/200 | AES/GCM/NoPadding | 2.16.840.1.1 |
| M | 9/xmlenc11#aes192-gcm | | 01.3.4.1.26 |
| A256GC | http://www.w3.org/200 | AES/GCM/NoPadding | 2.16.840.1.1 |
| M | 9/xmlenc11#aes256-gcm | | 01.3.4.1.46 |
+--------+-----------------------+-------------------+--------------+
Appendix C. Test Cases for AES_CBC_HMAC_SHA2 Algorithms
The following test cases can be used to validate implementations of
the AES_CBC_HMAC_SHA2 algorithms defined in Section 4.10. They are
also intended to correspond to test cases that may appear in a future
version of [I-D.mcgrew-aead-aes-cbc-hmac-sha2], demonstrating that
the cryptographic computations performed are the same.
The variable names are those defined in Section 4.10. All values are
hexadecimal.
Jones Expires March 19, 2014 [Page 58]
Internet-Draft JSON Web Algorithms (JWA) September 2013
C.1. Test Cases for AES_128_CBC_HMAC_SHA_256
AES_128_CBC_HMAC_SHA_256
K = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
ENC_KEY = 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
P = 41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65
IV = 1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04
A = 54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
4b 65 72 63 6b 68 6f 66 66 73
AL = 00 00 00 00 00 00 01 50
E = c8 0e df a3 2d df 39 d5 ef 00 c0 b4 68 83 42 79
a2 e4 6a 1b 80 49 f7 92 f7 6b fe 54 b9 03 a9 c9
a9 4a c9 b4 7a d2 65 5c 5f 10 f9 ae f7 14 27 e2
fc 6f 9b 3f 39 9a 22 14 89 f1 63 62 c7 03 23 36
09 d4 5a c6 98 64 e3 32 1c f8 29 35 ac 40 96 c8
6e 13 33 14 c5 40 19 e8 ca 79 80 df a4 b9 cf 1b
38 4c 48 6f 3a 54 c5 10 78 15 8e e5 d7 9d e5 9f
bd 34 d8 48 b3 d6 95 50 a6 76 46 34 44 27 ad e5
4b 88 51 ff b5 98 f7 f8 00 74 b9 47 3c 82 e2 db
M = 65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4
e6 e5 45 82 47 65 15 f0 ad 9f 75 a2 b7 1c 73 ef
T = 65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4
Jones Expires March 19, 2014 [Page 59]
Internet-Draft JSON Web Algorithms (JWA) September 2013
C.2. Test Cases for AES_192_CBC_HMAC_SHA_384
K = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17
ENC_KEY = 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27
28 29 2a 2b 2c 2d 2e 2f
P = 41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65
IV = 1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04
A = 54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
4b 65 72 63 6b 68 6f 66 66 73
AL = 00 00 00 00 00 00 01 50
E = ea 65 da 6b 59 e6 1e db 41 9b e6 2d 19 71 2a e5
d3 03 ee b5 00 52 d0 df d6 69 7f 77 22 4c 8e db
00 0d 27 9b dc 14 c1 07 26 54 bd 30 94 42 30 c6
57 be d4 ca 0c 9f 4a 84 66 f2 2b 22 6d 17 46 21
4b f8 cf c2 40 0a dd 9f 51 26 e4 79 66 3f c9 0b
3b ed 78 7a 2f 0f fc bf 39 04 be 2a 64 1d 5c 21
05 bf e5 91 ba e2 3b 1d 74 49 e5 32 ee f6 0a 9a
c8 bb 6c 6b 01 d3 5d 49 78 7b cd 57 ef 48 49 27
f2 80 ad c9 1a c0 c4 e7 9c 7b 11 ef c6 00 54 e3
M = 84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
75 16 80 39 cc c7 33 d7 45 94 f8 86 b3 fa af d4
86 f2 5c 71 31 e3 28 1e 36 c7 a2 d1 30 af de 57
T = 84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
75 16 80 39 cc c7 33 d7
Jones Expires March 19, 2014 [Page 60]
Internet-Draft JSON Web Algorithms (JWA) September 2013
C.3. Test Cases for AES_256_CBC_HMAC_SHA_512
K = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
ENC_KEY = 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
P = 41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65
IV = 1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04
A = 54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
4b 65 72 63 6b 68 6f 66 66 73
AL = 00 00 00 00 00 00 01 50
E = 4a ff aa ad b7 8c 31 c5 da 4b 1b 59 0d 10 ff bd
3d d8 d5 d3 02 42 35 26 91 2d a0 37 ec bc c7 bd
82 2c 30 1d d6 7c 37 3b cc b5 84 ad 3e 92 79 c2
e6 d1 2a 13 74 b7 7f 07 75 53 df 82 94 10 44 6b
36 eb d9 70 66 29 6a e6 42 7e a7 5c 2e 08 46 a1
1a 09 cc f5 37 0d c8 0b fe cb ad 28 c7 3f 09 b3
a3 b7 5e 66 2a 25 94 41 0a e4 96 b2 e2 e6 60 9e
31 e6 e0 2c c8 37 f0 53 d2 1f 37 ff 4f 51 95 0b
be 26 38 d0 9d d7 a4 93 09 30 80 6d 07 03 b1 f6
M = 4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5
fd 30 a5 65 c6 16 ff b2 f3 64 ba ec e6 8f c4 07
53 bc fc 02 5d de 36 93 75 4a a1 f5 c3 37 3b 9c
T = 4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5
Jones Expires March 19, 2014 [Page 61]
Internet-Draft JSON Web Algorithms (JWA) September 2013
Appendix D. Example ECDH-ES Key Agreement Computation
This example uses ECDH-ES Key Agreement and the Concat KDF to derive
the Content Encryption Key (CEK) in the manner described in
Section 4.7. In this example, the ECDH-ES Direct Key Agreement mode
("alg" value "ECDH-ES") is used to produce an agreed upon key for AES
GCM with 128 bit keys ("enc" value "A128GCM").
In this example, a sender Alice is encrypting content to a recipient
Bob. The sender (Alice) generates an ephemeral key for the key
agreement computation. Alice's ephemeral key (in JWK format) used
for the key agreement computation in this example (including the
private part) is:
{"kty":"EC",
"crv":"P-256",
"x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
"y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps",
"d":"0_NxaRPUMQoAJt50Gz8YiTr8gRTwyEaCumd-MToTmIo"
}
The recipient's (Bob's) key (in JWK format) used for the key
agreement computation in this example (including the private part)
is:
{"kty":"EC",
"crv":"P-256",
"x":"weNJy2HscCSM6AEDTDg04biOvhFhyyWvOHQfeF_PxMQ",
"y":"e8lnCO-AlStT-NJVX-crhB7QRYhiix03illJOVAOyck",
"d":"VEmDZpDXXK8p8N0Cndsxs924q6nS1RXFASRl6BfUqdw"
}
Header parameter values used in this example are as follows. In this
example, the "apu" (agreement PartyUInfo) parameter value is the
base64url encoding of the UTF-8 string "Alice" and the "apv"
(agreement PartyVInfo) parameter value is the base64url encoding of
the UTF-8 string "Bob". The "epk" parameter is used to communicate
the sender's (Alice's) ephemeral public key value to the recipient
(Bob).
Jones Expires March 19, 2014 [Page 62]
Internet-Draft JSON Web Algorithms (JWA) September 2013
{"alg":"ECDH-ES",
"enc":"A128GCM",
"apu":"QWxpY2U",
"apv":"Qm9i",
"epk":
{"kty":"EC",
"crv":"P-256",
"x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
"y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps"
}
}
The resulting Concat KDF [NIST.800-56A] parameter values are:
Z This is set to the ECDH-ES key agreement output. (This value is
often not directly exposed by libraries, due to NIST security
requirements, and only serves as an input to a KDF.) In this
example, Z is the octet sequence:
[158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132,
38, 156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121,
140, 254, 144, 196].
keydatalen This value is 128 - the number of bits in the desired
output key (because "A128GCM" uses a 128 bit key).
AlgorithmID This is set to the octets representing the 32 bit big
endian value 7 - [0, 0, 0, 7] - the number of octets in the
AlgorithmID content "A128GCM", followed, by the octets
representing the UTF-8 string "A128GCM" - [65, 49, 50, 56, 71, 67,
77].
PartyUInfo This is set to the octets representing the 32 bit big
endian value 5 - [0, 0, 0, 5] - the number of octets in the
PartyUInfo content "Alice", followed, by the octets representing
the UTF-8 string "Alice" - [65, 108, 105, 99, 101].
PartyVInfo This is set to the octets representing the 32 bit big
endian value 3 - [0, 0, 0, 3] - the number of octets in the
PartyUInfo content "Bob", followed, by the octets representing the
UTF-8 string "Bob" - [66, 111, 98].
SuppPubInfo This is set to the octets representing the 32 bit big
endian value 128 - [0, 0, 0, 128] - the keydatalen value.
SuppPrivInfo This is set to the empty octet sequence.
Concatenating the parameters AlgorithmID through SuppPubInfo results
in an OtherInfo value of:
Jones Expires March 19, 2014 [Page 63]
Internet-Draft JSON Web Algorithms (JWA) September 2013
[0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105,
99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]
Concatenating the round number 1 ([0, 0, 0, 1]), Z, and the OtherInfo
value results in the Concat KDF round 1 hash input of:
[0, 0, 0, 1,
158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132, 38,
156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121, 140,
254, 144, 196,
0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99,
101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]
The resulting derived key, which is the first 128 bits of the round 1
hash output is:
[86, 170, 141, 234, 248, 35, 109, 32, 92, 34, 40, 205, 113, 167, 16,
26]
The base64url encoded representation of this derived key is:
usEpwFIC_qrmBExntFwxMA
Appendix E. Acknowledgements
Solutions for signing and encrypting JSON content were previously
explored by Magic Signatures [MagicSignatures], JSON Simple Sign
[JSS], Canvas Applications [CanvasApp], JSON Simple Encryption [JSE],
and JavaScript Message Security Format [I-D.rescorla-jsms], all of
which influenced this draft.
The Authenticated Encryption with AES-CBC and HMAC-SHA
[I-D.mcgrew-aead-aes-cbc-hmac-sha2] specification, upon which the
AES_CBC_HMAC_SHA2 algorithms are based, was written by David A.
McGrew and Kenny Paterson. The test cases for AES_CBC_HMAC_SHA2 are
based upon those for [I-D.mcgrew-aead-aes-cbc-hmac-sha2] by John
Foley.
Matt Miller wrote Using JavaScript Object Notation (JSON) Web
Encryption (JWE) for Protecting JSON Web Key (JWK) Objects
[I-D.miller-jose-jwe-protected-jwk], which the password-based
encryption content of this draft is based upon.
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:
Dirk Balfanz, Richard Barnes, John Bradley, Brian Campbell, Breno de
Jones Expires March 19, 2014 [Page 64]
Internet-Draft JSON Web Algorithms (JWA) September 2013
Medeiros, Yaron Y. Goland, Dick Hardt, Jeff Hodges, Edmund Jay, James
Manger, Matt Miller, Tony Nadalin, Axel Nennker, John Panzer,
Emmanuel Raviart, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and
Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
Sean Turner and Stephen Farrell served as Security area directors
during the creation of this specification.
Appendix F. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-16
o Added a DataLen prefix to the AlgorithmID value in the Concat KDF
computation.
o Added OIDs for encryption algorithms, additional signature
algorithm OIDs, and additional XML DSIG/ENC URIs in the algorithm
cross-reference tables.
o Changes to address editorial and minor issues #28, #36, #39, #52,
#53, #55, #127, #128, #136, #137, #141, #150, #151, #152, and
#155.
-15
o Changed statements about rejecting JWSs to statements about
validation failing, addressing issue #35.
o Stated that changes of implementation requirements are only
permitted on a Specification Required basis, addressing issue #38.
o Made "oct" a required key type, addressing issue #40.
o Updated the example ECDH-ES key agreement values.
o Changes to address editorial and minor issues #34, #37, #49, #63,
#123, #124, #125, #130, #132, #133, #138, #139, #140, #142, #143,
#144, #145, #148, #149, #150, and #162.
-14
o Removed "PBKDF2" key type and added "p2s" and "p2c" header
parameters for use with the PBES2 algorithms.
Jones Expires March 19, 2014 [Page 65]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Made the RSA private key parameters that are there to enable
optimizations be RECOMMENDED rather than REQUIRED.
o Added algorithm identifiers for AES algorithms using 192 bit keys
and for RSASSA-PSS using HMAC SHA-384.
o Added security considerations about key lifetimes, addressing
issue #18.
o Added an example ECDH-ES key agreement computation.
-13
o Added key encryption with AES GCM as specified in
draft-jones-jose-aes-gcm-key-wrap-01, addressing issue #13.
o Added security considerations text limiting the number of times
that an AES GCM key can be used for key encryption or direct
encryption, per Section 8.3 of NIST SP 800-38D, addressing issue
#28.
o Added password-based key encryption as specified in
draft-miller-jose-jwe-protected-jwk-02.
-12
o In the Direct Key Agreement case, the Concat KDF AlgorithmID is
set to the octets of the UTF-8 representation of the "enc" header
parameter value.
o Restored the "apv" (agreement PartyVInfo) parameter.
o Moved the "epk", "apu", and "apv" Header Parameter definitions to
be with the algorithm descriptions that use them.
o Changed terminology from "block encryption" to "content
encryption".
-11
o Removed the Encrypted Key value from the AAD computation since it
is already effectively integrity protected by the encryption
process. The AAD value now only contains the representation of
the JWE Encrypted Header.
o Removed "apv" (agreement PartyVInfo) since it is no longer used.
Jones Expires March 19, 2014 [Page 66]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Added more information about the use of PartyUInfo during key
agreement.
o Use the keydatalen as the SuppPubInfo value for the Concat KDF
when doing key agreement, as RFC 2631 does.
o Added algorithm identifiers for RSASSA-PSS with SHA-256 and SHA-
512.
o Added a Parameter Information Class value to the JSON Web Key
Parameters registry, which registers whether the parameter conveys
public or private information.
-10
o Changed the JWE processing rules for multiple recipients so that a
single AAD value contains the header parameters and encrypted key
values for all the recipients, enabling AES GCM to be safely used
for multiple recipients.
-09
o Expanded the scope of the JWK parameters to include private and
symmetric key representations, as specified by
draft-jones-jose-json-private-and-symmetric-key-00.
o Changed term "JWS Secured Input" to "JWS Signing Input".
o Changed from using the term "byte" to "octet" when referring to 8
bit values.
o Specified that AES Key Wrap uses the default initial value
specified in Section 2.2.3.1 of RFC 3394. This addressed issue
#19.
o Added Key Management Mode definitions to terminology section and
used the defined terms to provide clearer key management
instructions. This addressed issue #5.
o Replaced "A128CBC+HS256" and "A256CBC+HS512" with "A128CBC-HS256"
and "A256CBC-HS512". The new algorithms perform the same
cryptographic computations as [I-D.mcgrew-aead-aes-cbc-hmac-sha2],
but with the Initialization Vector and Authentication Tag values
remaining separate from the Ciphertext value in the output
representation. Also deleted the header parameters "epu"
(encryption PartyUInfo) and "epv" (encryption PartyVInfo), since
they are no longer used.
Jones Expires March 19, 2014 [Page 67]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Changed from using the term "Integrity Value" to "Authentication
Tag".
-08
o Changed the name of the JWK key type parameter from "alg" to
"kty".
o Replaced uses of the term "AEAD" with "Authenticated Encryption",
since the term AEAD in the RFC 5116 sense implied the use of a
particular data representation, rather than just referring to the
class of algorithms that perform authenticated encryption with
associated data.
o Applied editorial improvements suggested by Jeff Hodges. Many of
these simplified the terminology used.
o Added seriesInfo information to Internet Draft references.
-07
o Added a data length prefix to PartyUInfo and PartyVInfo values.
o Changed the name of the JWK RSA modulus parameter from "mod" to
"n" and the name of the JWK RSA exponent parameter from "xpo" to
"e", so that the identifiers are the same as those used in RFC
3447.
o Made several local editorial changes to clean up loose ends left
over from to the decision to only support block encryption methods
providing integrity.
-06
o Removed the "int" and "kdf" parameters and defined the new
composite Authenticated Encryption algorithms "A128CBC+HS256" and
"A256CBC+HS512" to replace the former uses of AES CBC, which
required the use of separate integrity and key derivation
functions.
o Included additional values in the Concat KDF calculation -- the
desired output size and the algorithm value, and optionally
PartyUInfo and PartyVInfo values. Added the optional header
parameters "apu" (agreement PartyUInfo), "apv" (agreement
PartyVInfo), "epu" (encryption PartyUInfo), and "epv" (encryption
PartyVInfo).
Jones Expires March 19, 2014 [Page 68]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Changed the name of the JWK RSA exponent parameter from "exp" to
"xpo" so as to allow the potential use of the name "exp" for a
future extension that might define an expiration parameter for
keys. (The "exp" name is already used for this purpose in the JWT
specification.)
o Applied changes made by the RFC Editor to RFC 6749's registry
language to this specification.
-05
o Support both direct encryption using a shared or agreed upon
symmetric key, and the use of a shared or agreed upon symmetric
key to key wrap the CMK. Specifically, added the "alg" values
"dir", "ECDH-ES+A128KW", and "ECDH-ES+A256KW" to finish filling in
this set of capabilities.
o Updated open issues.
-04
o Added text requiring that any leading zero bytes be retained in
base64url encoded key value representations for fixed-length
values.
o Added this language to Registration Templates: "This name is case
sensitive. Names that match other registered names in a case
insensitive manner SHOULD NOT be accepted."
o Described additional open issues.
o Applied editorial suggestions.
-03
o Always use a 128 bit "authentication tag" size for AES GCM,
regardless of the key size.
o Specified that use of a 128 bit IV is REQUIRED with AES CBC. It
was previously RECOMMENDED.
o Removed key size language for ECDSA algorithms, since the key size
is implied by the algorithm being used.
o Stated that the "int" key size must be the same as the hash output
size (and not larger, as was previously allowed) so that its size
is defined for key generation purposes.
Jones Expires March 19, 2014 [Page 69]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Added the "kdf" (key derivation function) header parameter to
provide crypto agility for key derivation. The default KDF
remains the Concat KDF with the SHA-256 digest function.
o Clarified that the "mod" and "exp" values are unsigned.
o Added Implementation Requirements columns to algorithm tables and
Implementation Requirements entries to algorithm registries.
o Changed AES Key Wrap to RECOMMENDED.
o Moved registries JSON Web Signature and Encryption Header
Parameters and JSON Web Signature and Encryption Type Values to
the JWS specification.
o Moved JSON Web Key Parameters registry to the JWK specification.
o Changed registration requirements from RFC Required to
Specification Required with Expert Review.
o Added Registration Template sections for defined registries.
o Added Registry Contents sections to populate registry values.
o No longer say "the UTF-8 representation of the JWS Secured Input
(which is the same as the ASCII representation)". Just call it
"the ASCII representation of the JWS Secured Input".
o Added "Collision Resistant Namespace" to the terminology section.
o Numerous editorial improvements.
-02
o For AES GCM, use the "additional authenticated data" parameter to
provide integrity for the header, encrypted key, and ciphertext
and use the resulting "authentication tag" value as the JWE
Authentication Tag.
o Defined minimum required key sizes for algorithms without
specified key sizes.
o Defined KDF output key sizes.
o Specified the use of PKCS #5 padding with AES CBC.
o Generalized text to allow key agreement to be employed as an
alternative to key wrapping or key encryption.
Jones Expires March 19, 2014 [Page 70]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Clarified that ECDH-ES is a key agreement algorithm.
o Required implementation of AES-128-KW and AES-256-KW.
o Removed the use of "A128GCM" and "A256GCM" for key wrapping.
o Removed "A512KW" since it turns out that it's not a standard
algorithm.
o Clarified the relationship between "typ" header parameter values
and MIME types.
o Generalized language to refer to Message Authentication Codes
(MACs) rather than Hash-based Message Authentication Codes (HMACs)
unless in a context specific to HMAC algorithms.
o Established registries: JSON Web Signature and Encryption Header
Parameters, JSON Web Signature and Encryption Algorithms, JSON Web
Signature and Encryption "typ" Values, JSON Web Key Parameters,
and JSON Web Key Algorithm Families.
o Moved algorithm-specific definitions from JWK to JWA.
o Reformatted to give each member definition its own section
heading.
-01
o Moved definition of "alg":"none" for JWSs here from the JWT
specification since this functionality is likely to be useful in
more contexts that just for JWTs.
o Added Advanced Encryption Standard (AES) Key Wrap Algorithm using
512 bit keys ("A512KW").
o Added text "Alternatively, the Encoded JWS Signature MAY be
base64url decoded to produce the JWS Signature and this value can
be compared with the computed HMAC value, as this comparison
produces the same result as comparing the encoded values".
o Corrected the Magic Signatures reference.
o Made other editorial improvements suggested by JOSE working group
participants.
-00
Jones Expires March 19, 2014 [Page 71]
Internet-Draft JSON Web Algorithms (JWA) September 2013
o Created the initial IETF draft based upon
draft-jones-json-web-signature-04 and
draft-jones-json-web-encryption-02 with no normative changes.
o Changed terminology to no longer call both digital signatures and
HMACs "signatures".
Author's Address
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
Jones Expires March 19, 2014 [Page 72]
Html markup produced by rfcmarkup 1.129b, available from
https://tools.ietf.org/tools/rfcmarkup/