Internet Engineering Task Force (IETF) M. Jones
Request for Comments: 7518 Microsoft
Category: Standards Track May 2015
ISSN: 2070-1721
JSON Web Algorithms (JWA)
Abstract
This 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 is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7518.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Jones Standards Track [Page 1]RFC 7518 JSON Web Algorithms (JWA) May 2015
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Cryptographic Algorithms for Digital Signatures and MACs . . 6
3.1. "alg" (Algorithm) Header Parameter Values for JWS . . . . 6
3.2. HMAC with SHA-2 Functions . . . . . . . . . . . . . . . . 7
3.3. Digital Signature with RSASSA-PKCS1-v1_5 . . . . . . . . 8
3.4. Digital Signature with ECDSA . . . . . . . . . . . . . . 9
3.5. Digital Signature with RSASSA-PSS . . . . . . . . . . . . 10
3.6. Using the Algorithm "none" . . . . . . . . . . . . . . . 11
4. Cryptographic Algorithms for Key Management . . . . . . . . . 11
4.1. "alg" (Algorithm) Header Parameter Values for JWE . . . . 12
4.2. Key Encryption with RSAES-PKCS1-v1_5 . . . . . . . . . . 13
4.3. Key Encryption with RSAES OAEP . . . . . . . . . . . . . 14
4.4. Key Wrapping with AES Key Wrap . . . . . . . . . . . . . 14
4.5. Direct Encryption with a Shared Symmetric Key . . . . . . 15
4.6. Key Agreement with Elliptic Curve Diffie-Hellman
Ephemeral Static (ECDH-ES) . . . . . . . . . . . . . . . 15
4.6.1. Header Parameters Used for ECDH Key Agreement . . . . 16
4.6.1.1. "epk" (Ephemeral Public Key) Header Parameter . . 16
4.6.1.2. "apu" (Agreement PartyUInfo) Header Parameter . . 17
4.6.1.3. "apv" (Agreement PartyVInfo) Header Parameter . . 17
4.6.2. Key Derivation for ECDH Key Agreement . . . . . . . . 17
4.7. Key Encryption with AES GCM . . . . . . . . . . . . . . . 18
4.7.1. Header Parameters Used for AES GCM Key Encryption . . 19
4.7.1.1. "iv" (Initialization Vector) Header Parameter . . 19
4.7.1.2. "tag" (Authentication Tag) Header Parameter . . . 19
4.8. Key Encryption with PBES2 . . . . . . . . . . . . . . . . 20
4.8.1. Header Parameters Used for PBES2 Key Encryption . . . 20
4.8.1.1. "p2s" (PBES2 Salt Input) Header Parameter . . . . 21
4.8.1.2. "p2c" (PBES2 Count) Header Parameter . . . . . . 21
5. Cryptographic Algorithms for Content Encryption . . . . . . . 21
5.1. "enc" (Encryption Algorithm) Header Parameter Values for
JWE . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2. AES_CBC_HMAC_SHA2 Algorithms . . . . . . . . . . . . . . 22
5.2.1. Conventions Used in Defining AES_CBC_HMAC_SHA2 . . . 23
5.2.2. Generic AES_CBC_HMAC_SHA2 Algorithm . . . . . . . . . 23
5.2.2.1. AES_CBC_HMAC_SHA2 Encryption . . . . . . . . . . 23
5.2.2.2. AES_CBC_HMAC_SHA2 Decryption . . . . . . . . . . 25
5.2.3. AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . 25
5.2.4. AES_192_CBC_HMAC_SHA_384 . . . . . . . . . . . . . . 26
5.2.5. AES_256_CBC_HMAC_SHA_512 . . . . . . . . . . . . . . 26
5.2.6. Content Encryption with AES_CBC_HMAC_SHA2 . . . . . . 26
5.3. Content Encryption with AES GCM . . . . . . . . . . . . . 27
6. Cryptographic Algorithms for Keys . . . . . . . . . . . . . . 27
6.1. "kty" (Key Type) Parameter Values . . . . . . . . . . . . 28
Jones Standards Track [Page 2]RFC 7518 JSON Web Algorithms (JWA) May 2015
6.2. Parameters for Elliptic Curve Keys . . . . . . . . . . . 28
6.2.1. Parameters for Elliptic Curve Public Keys . . . . . . 28
6.2.1.1. "crv" (Curve) Parameter . . . . . . . . . . . . . 28
6.2.1.2. "x" (X Coordinate) Parameter . . . . . . . . . . 29
6.2.1.3. "y" (Y Coordinate) Parameter . . . . . . . . . . 29
6.2.2. Parameters for Elliptic Curve Private Keys . . . . . 29
6.2.2.1. "d" (ECC Private Key) Parameter . . . . . . . . . 29
6.3. Parameters for RSA Keys . . . . . . . . . . . . . . . . . 30
6.3.1. Parameters for RSA Public Keys . . . . . . . . . . . 30
6.3.1.1. "n" (Modulus) Parameter . . . . . . . . . . . . . 30
6.3.1.2. "e" (Exponent) Parameter . . . . . . . . . . . . 30
6.3.2. Parameters for RSA Private Keys . . . . . . . . . . . 30
6.3.2.1. "d" (Private Exponent) Parameter . . . . . . . . 30
6.3.2.2. "p" (First Prime Factor) Parameter . . . . . . . 31
6.3.2.3. "q" (Second Prime Factor) Parameter . . . . . . . 31
6.3.2.4. "dp" (First Factor CRT Exponent) Parameter . . . 31
6.3.2.5. "dq" (Second Factor CRT Exponent) Parameter . . . 31
6.3.2.6. "qi" (First CRT Coefficient) Parameter . . . . . 31
6.3.2.7. "oth" (Other Primes Info) Parameter . . . . . . . 31
6.4. Parameters for Symmetric Keys . . . . . . . . . . . . . . 32
6.4.1. "k" (Key Value) Parameter . . . . . . . . . . . . . . 32
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
7.1. JSON Web Signature and Encryption Algorithms Registry . . 33
7.1.1. Registration Template . . . . . . . . . . . . . . . . 34
7.1.2. Initial Registry Contents . . . . . . . . . . . . . . 35
7.2. Header Parameter Names Registration . . . . . . . . . . . 42
7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 42
7.3. JSON Web Encryption Compression Algorithms Registry . . . 43
7.3.1. Registration Template . . . . . . . . . . . . . . . . 43
7.3.2. Initial Registry Contents . . . . . . . . . . . . . . 44
7.4. JSON Web Key Types Registry . . . . . . . . . . . . . . . 44
7.4.1. Registration Template . . . . . . . . . . . . . . . . 44
7.4.2. Initial Registry Contents . . . . . . . . . . . . . . 45
7.5. JSON Web Key Parameters Registration . . . . . . . . . . 45
7.5.1. Registry Contents . . . . . . . . . . . . . . . . . . 46
7.6. JSON Web Key Elliptic Curve Registry . . . . . . . . . . 48
7.6.1. Registration Template . . . . . . . . . . . . . . . . 48
7.6.2. Initial Registry Contents . . . . . . . . . . . . . . 49
8. Security Considerations . . . . . . . . . . . . . . . . . . . 49
8.1. Cryptographic Agility . . . . . . . . . . . . . . . . . . 50
8.2. Key Lifetimes . . . . . . . . . . . . . . . . . . . . . . 50
8.3. RSAES-PKCS1-v1_5 Security Considerations . . . . . . . . 50
8.4. AES GCM Security Considerations . . . . . . . . . . . . . 50
8.5. Unsecured JWS Security Considerations . . . . . . . . . . 51
8.6. Denial-of-Service Attacks . . . . . . . . . . . . . . . . 51
8.7. Reusing Key Material when Encrypting Keys . . . . . . . . 51
8.8. Password Considerations . . . . . . . . . . . . . . . . . 52
8.9. Key Entropy and Random Values . . . . . . . . . . . . . . 52
Jones Standards Track [Page 3]RFC 7518 JSON Web Algorithms (JWA) May 2015
8.10. Differences between Digital Signatures and MACs . . . . . 52
8.11. Using Matching Algorithm Strengths . . . . . . . . . . . 53
8.12. Adaptive Chosen-Ciphertext Attacks . . . . . . . . . . . 53
8.13. Timing Attacks . . . . . . . . . . . . . . . . . . . . . 53
8.14. RSA Private Key Representations and Blinding . . . . . . 53
9. Internationalization Considerations . . . . . . . . . . . . . 53
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 53
10.1. Normative References . . . . . . . . . . . . . . . . . . 53
10.2. Informative References . . . . . . . . . . . . . . . . . 56
Appendix A. Algorithm Identifier Cross-Reference . . . . . . . . 59
A.1. Digital Signature/MAC Algorithm Identifier Cross-
Reference . . . . . . . . . . . . . . . . . . . . . . . . 60
A.2. Key Management Algorithm Identifier Cross-Reference . . . 61
A.3. Content Encryption Algorithm Identifier Cross-Reference . 62
Appendix B. Test Cases for AES_CBC_HMAC_SHA2 Algorithms . . . . 62
B.1. Test Cases for AES_128_CBC_HMAC_SHA_256 . . . . . . . . . 63
B.2. Test Cases for AES_192_CBC_HMAC_SHA_384 . . . . . . . . . 64
B.3. Test Cases for AES_256_CBC_HMAC_SHA_512 . . . . . . . . . 65
Appendix C. Example ECDH-ES Key Agreement Computation . . . . . 66
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 69
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 69
1. Introduction
This 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 JSON-based [RFC7159] 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", "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].
Jones Standards Track [Page 4]RFC 7518 JSON Web Algorithms (JWA) May 2015
The interpretation should only be applied when the terms appear in
all capital letters.
BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per
Section 2 of [JWS].
UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation
of STRING, where STRING is a sequence of zero or more Unicode
[UNICODE] characters.
ASCII(STRING) denotes the octets of the ASCII [RFC20] representation
of STRING, where STRING is a sequence of zero or more ASCII
characters.
The concatenation of two values A and B is denoted as A || B.
2. Terminology
The terms "JSON Web Signature (JWS)", "Base64url Encoding", "Header
Parameter", "JOSE Header", "JWS Payload", "JWS Protected Header",
"JWS Signature", "JWS Signing Input", and "Unsecured JWS" are defined
by the JWS specification [JWS].
The terms "JSON Web Encryption (JWE)", "Additional Authenticated Data
(AAD)", "Authentication Tag", "Content Encryption Key (CEK)", "Direct
Encryption", "Direct Key Agreement", "JWE Authentication Tag", "JWE
Ciphertext", "JWE Encrypted Key", "JWE Initialization Vector", "JWE
Protected Header", "Key Agreement with Key Wrapping", "Key
Encryption", "Key Management Mode", and "Key Wrapping" are defined by
the JWE specification [JWE].
The terms "JSON Web Key (JWK)" and "JWK Set" are defined by the JWK
specification [JWK].
The terms "Ciphertext", "Digital Signature", "Initialization Vector",
"Message Authentication Code (MAC)", and "Plaintext" are defined by
the "Internet Security Glossary, Version 2" [RFC4949].
This term is defined by this specification:
Base64urlUInt
The representation of a positive or zero integer value 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 needed to represent the
value. Zero is represented as BASE64URL(single zero-valued
octet), which is "AA".
Jones Standards Track [Page 5]RFC 7518 JSON Web Algorithms (JWA) May 2015
3. Cryptographic Algorithms for Digital Signatures and MACs
JWS uses cryptographic algorithms to digitally sign or create a MAC
of the contents of the JWS Protected 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:
+--------------+-------------------------------+--------------------+
| "alg" Param | Digital Signature or MAC | Implementation |
| Value | Algorithm | Requirements |
+--------------+-------------------------------+--------------------+
| HS256 | HMAC using SHA-256 | Required |
| HS384 | HMAC using SHA-384 | Optional |
| HS512 | HMAC using SHA-512 | Optional |
| RS256 | RSASSA-PKCS1-v1_5 using | Recommended |
| | SHA-256 | |
| RS384 | RSASSA-PKCS1-v1_5 using | Optional |
| | SHA-384 | |
| RS512 | RSASSA-PKCS1-v1_5 using | Optional |
| | SHA-512 | |
| ES256 | ECDSA using P-256 and SHA-256 | Recommended+ |
| ES384 | ECDSA using P-384 and SHA-384 | Optional |
| ES512 | ECDSA using P-521 and SHA-512 | Optional |
| PS256 | RSASSA-PSS using SHA-256 and | Optional |
| | MGF1 with SHA-256 | |
| PS384 | RSASSA-PSS using SHA-384 and | Optional |
| | MGF1 with SHA-384 | |
| PS512 | RSASSA-PSS using SHA-512 and | Optional |
| | MGF1 with SHA-512 | |
| none | No digital signature or MAC | Optional |
| | performed | |
+--------------+-------------------------------+--------------------+
The use of "+" in the Implementation Requirements column indicates
that the requirement strength is likely to be increased in a future
version of the specification.
See Appendix A.1 for a table cross-referencing the JWS digital
signature and MAC "alg" (algorithm) values defined in this
specification with the equivalent identifiers used by other standards
and software packages.
Jones Standards Track [Page 6]
RFC 7518 JSON Web Algorithms (JWA) May 2015
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 MAC. This
can be used to demonstrate that whoever generated the MAC was in
possession of the MAC key. The algorithm for implementing and
validating HMACs is provided in RFC 2104 [RFC2104].
A key of the same size as the hash output (for instance, 256 bits for
"HS256") or larger MUST be used with this algorithm. (This
requirement is based on Section 5.3.4 (Security Effect of the HMAC
Key) of NIST SP 800-117 [NIST.800-107], which states that the
effective security strength is the minimum of the security strength
of the key and two times the size of the internal hash value.)
The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the
hash algorithm "H", using the JWS Signing Input as the "text" value,
and using the shared key. The HMAC output value is the JWS
Signature.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWS Signature is an HMAC value computed using the
corresponding algorithm:
+-------------------+--------------------+
| "alg" Param Value | MAC Algorithm |
+-------------------+--------------------+
| HS256 | HMAC using SHA-256 |
| HS384 | HMAC using SHA-384 |
| HS512 | HMAC using SHA-512 |
+-------------------+--------------------+
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 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 value. The
comparison of the computed HMAC value to the JWS Signature value MUST
be done in a constant-time manner to thwart timing attacks.
Alternatively, the computed HMAC value can be base64url encoded and
compared to the received encoded JWS Signature value (also in a
constant-time manner), as this comparison produces the same result as
comparing the unencoded values. In either case, if the values match,
the HMAC has been validated.
Jones Standards Track [Page 7]RFC 7518 JSON Web Algorithms (JWA) May 2015
Securing content and validation 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-2 [SHS] hash functions.
A key of size 2048 bits or larger MUST be used with these algorithms.
The RSASSA-PKCS1-v1_5 SHA-256 digital signature is generated as
follows: generate a digital signature of the JWS Signing Input using
RSASSA-PKCS1-v1_5-SIGN and the SHA-256 hash function with the desired
private key. This is the JWS Signature value.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWS Signature is a digital signature value computed
using the corresponding algorithm:
+-------------------+---------------------------------+
| "alg" Param Value | Digital Signature Algorithm |
+-------------------+---------------------------------+
| RS256 | RSASSA-PKCS1-v1_5 using SHA-256 |
| RS384 | RSASSA-PKCS1-v1_5 using SHA-384 |
| RS512 | RSASSA-PKCS1-v1_5 using SHA-512 |
+-------------------+---------------------------------+
The RSASSA-PKCS1-v1_5 SHA-256 digital signature for a JWS is
validated as follows: submit the JWS Signing Input, the JWS
Signature, 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 and validation 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].
Jones Standards Track [Page 8]RFC 7518 JSON Web Algorithms (JWA) May 2015
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 for many operations. 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 ECDSA P-256 SHA-256 digital signature is generated as follows:
1. Generate a digital signature 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. The resulting 64-octet sequence is the JWS Signature value.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWS Signature is a digital signature value computed
using the corresponding algorithm:
+-------------------+-------------------------------+
| "alg" Param Value | Digital Signature Algorithm |
+-------------------+-------------------------------+
| ES256 | ECDSA using P-256 and SHA-256 |
| ES384 | ECDSA using P-384 and SHA-384 |
| ES512 | ECDSA using P-521 and SHA-512 |
+-------------------+-------------------------------+
Jones Standards Track [Page 9]RFC 7518 JSON Web Algorithms (JWA) May 2015
The ECDSA P-256 SHA-256 digital signature for a JWS is validated as
follows:
1. The JWS Signature value MUST be a 64-octet sequence. If it is
not a 64-octet sequence, the validation has failed.
2. Split the 64-octet sequence into two 32-octet sequences. The
first octet sequence represents R and the second S. The values R
and S are represented as octet sequences using the Integer-to-
OctetString Conversion defined in Section 2.3.7 of SEC1 [SEC1]
(in big-endian octet order).
3. Submit the JWS Signing Input, R, S, and the public key (x, y) to
the ECDSA P-256 SHA-256 validator.
Signing and validation 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. (Note that the Integer-to-OctetString Conversion
defined in Section 2.3.7 of SEC1 [SEC1] used to represent R and S as
octet sequences adds zero-valued high-order padding bits when needed
to round the size up to a multiple of 8 bits; thus, each 521-bit
integer is represented using 528 bits in 66 octets.)
Examples using these algorithms are shown in Appendices A.3 and A.4
of [JWS].
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 and SHA-2 hash functions, always using
the same hash function for both the RSASSA-PSS hash function and the
MGF1 hash function. The size of the salt value is the same size as
the hash function output. All other algorithm parameters use the
defaults specified in Appendix A.2.3 of RFC 3447.
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:
generate a digital signature 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. This is the JWS
Signature value.
Jones Standards Track [Page 10]RFC 7518 JSON Web Algorithms (JWA) May 2015
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWS Signature is a digital signature value computed
using the corresponding algorithm:
+-------------------+-----------------------------------------------+
| "alg" Param Value | Digital Signature Algorithm |
+-------------------+-----------------------------------------------+
| PS256 | RSASSA-PSS using SHA-256 and MGF1 with |
| | SHA-256 |
| PS384 | RSASSA-PSS using SHA-384 and MGF1 with |
| | SHA-384 |
| PS512 | RSASSA-PSS using SHA-512 and MGF1 with |
| | SHA-512 |
+-------------------+-----------------------------------------------+
The RSASSA-PSS SHA-256 digital signature for a JWS is validated as
follows: submit the JWS Signing Input, the JWS Signature, 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 and validation 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.
3.6. Using the Algorithm "none"
JWSs MAY also be created that do not provide integrity protection.
Such a JWS is called an Unsecured JWS. An Unsecured JWS uses the
"alg" value "none" and is formatted identically to other JWSs, but
MUST use the empty octet sequence as its JWS Signature value.
Recipients MUST verify that the JWS Signature value is the empty
octet sequence.
Implementations that support Unsecured JWSs 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 Unsecured JWSs by default. In order
to mitigate downgrade attacks, applications MUST NOT signal
acceptance of Unsecured JWSs at a global level, and SHOULD signal
acceptance on a per-object basis. See Section 8.5 for security
considerations associated with using this algorithm.
4. Cryptographic Algorithms for Key Management
JWE uses cryptographic algorithms to encrypt or determine the Content
Encryption Key (CEK).
Jones Standards Track [Page 11]
RFC 7518 JSON Web Algorithms (JWA) May 2015
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" Param Value | Key Management | More | Implementation |
| | Algorithm | Header | Requirements |
| | | Params | |
+--------------------+--------------------+--------+----------------+
| RSA1_5 | RSAES-PKCS1-v1_5 | (none) | Recommended- |
| RSA-OAEP | RSAES OAEP using | (none) | Recommended+ |
| | default parameters | | |
| RSA-OAEP-256 | RSAES OAEP using | (none) | Optional |
| | SHA-256 and MGF1 | | |
| | with SHA-256 | | |
| A128KW | AES Key Wrap with | (none) | Recommended |
| | default initial | | |
| | value using | | |
| | 128-bit key | | |
| A192KW | AES Key Wrap with | (none) | Optional |
| | default initial | | |
| | value using | | |
| | 192-bit key | | |
| A256KW | AES Key Wrap with | (none) | Recommended |
| | default initial | | |
| | value using | | |
| | 256-bit key | | |
| dir | Direct use of a | (none) | Recommended |
| | shared symmetric | | |
| | key as the CEK | | |
| ECDH-ES | Elliptic Curve | "epk", | Recommended+ |
| | Diffie-Hellman | "apu", | |
| | Ephemeral Static | "apv" | |
| | key agreement | | |
| | using Concat KDF | | |
| ECDH-ES+A128KW | ECDH-ES using | "epk", | Recommended |
| | Concat KDF and CEK | "apu", | |
| | wrapped with | "apv" | |
| | "A128KW" | | |
| ECDH-ES+A192KW | ECDH-ES using | "epk", | Optional |
| | Concat KDF and CEK | "apu", | |
| | wrapped with | "apv" | |
| | "A192KW" | | |
Jones Standards Track [Page 12]
RFC 7518 JSON Web Algorithms (JWA) May 2015
| ECDH-ES+A256KW | ECDH-ES using | "epk", | Recommended |
| | Concat KDF and CEK | "apu", | |
| | wrapped with | "apv" | |
| | "A256KW" | | |
| A128GCMKW | Key wrapping with | "iv", | Optional |
| | AES GCM using | "tag" | |
| | 128-bit key | | |
| A192GCMKW | Key wrapping with | "iv", | Optional |
| | AES GCM using | "tag" | |
| | 192-bit key | | |
| A256GCMKW | Key wrapping with | "iv", | Optional |
| | AES GCM using | "tag" | |
| | 256-bit key | | |
| PBES2-HS256+A128KW | PBES2 with HMAC | "p2s", | Optional |
| | SHA-256 and | "p2c" | |
| | "A128KW" wrapping | | |
| PBES2-HS384+A192KW | PBES2 with HMAC | "p2s", | Optional |
| | SHA-384 and | "p2c" | |
| | "A192KW" wrapping | | |
| PBES2-HS512+A256KW | PBES2 with HMAC | "p2s", | Optional |
| | SHA-512 and | "p2c" | |
| | "A256KW" wrapping | | |
+--------------------+--------------------+--------+----------------+
The More Header Params 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 column 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.
See Appendix A.2 for a table cross-referencing the JWE "alg"
(algorithm) values defined in this specification with the equivalent
identifiers used by other standards and software packages.
4.2. 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" (algorithm) Header Parameter
value "RSA1_5" is used for this algorithm.
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].
Jones Standards Track [Page 13]
RFC 7518 JSON Web Algorithms (JWA) May 2015
4.3. Key Encryption with RSAES OAEP
This section defines the specifics of encrypting a JWE CEK with RSAES
using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447]. Two
sets of parameters for using OAEP are defined, which use different
hash functions. In the first case, the default parameters specified
in Appendix A.2.1 of RFC 3447 are used. (Those default parameters
are the SHA-1 hash function and the MGF1 with SHA-1 mask generation
function.) In the second case, the SHA-256 hash function and the
MGF1 with SHA-256 mask generation function are used.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWE Encrypted Key is the result of encrypting the
CEK using the corresponding algorithm:
+-------------------+-----------------------------------------------+
| "alg" Param Value | Key Management Algorithm |
+-------------------+-----------------------------------------------+
| RSA-OAEP | RSAES OAEP using default parameters |
| RSA-OAEP-256 | RSAES OAEP using SHA-256 and MGF1 with |
| | SHA-256 |
+-------------------+-----------------------------------------------+
A key of size 2048 bits or larger MUST be used with these algorithms.
(This requirement is based on Table 4 (Security-strength time frames)
of NIST SP 800-57 [NIST.800-57], which requires 112 bits of security
for new uses, and Table 2 (Comparable strengths) of the same, which
states that 2048-bit RSA keys provide 112 bits of security.)
An example using RSAES OAEP with the default parameters is shown in
Appendix A.1 of [JWE].
4.4. 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 of that
document.
Jones Standards Track [Page 14]
RFC 7518 JSON Web Algorithms (JWA) May 2015
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWE Encrypted Key is the result of encrypting the
CEK using the corresponding algorithm and key size:
+-----------------+-------------------------------------------------+
| "alg" Param | Key Management Algorithm |
| Value | |
+-----------------+-------------------------------------------------+
| A128KW | AES Key Wrap with default initial value using |
| | 128-bit key |
| A192KW | AES Key Wrap with default initial value using |
| | 192-bit key |
| A256KW | AES Key Wrap with default initial value using |
| | 256-bit key |
+-----------------+-------------------------------------------------+
An example using this algorithm is shown in Appendix A.3 of [JWE].
4.5. 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" (algorithm) Header
Parameter value "dir" is used in this case.
Refer to the security considerations on key lifetimes in Section 8.2
and AES GCM in Section 8.4 when considering utilizing direct
encryption.
4.6. 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.
A new ephemeral public key value MUST be generated for each key
agreement operation.
Jones Standards Track [Page 15]RFC 7518 JSON Web Algorithms (JWA) May 2015
In Direct Key Agreement mode, 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. The "alg" (algorithm) Header Parameter value "ECDH-ES" is
used in the Direct Key Agreement mode.
In Key Agreement with Key Wrapping mode, the output of the Concat KDF
MUST be a key of the length needed for the specified key wrapping
algorithm. In this case, the JWE Encrypted Key is the CEK wrapped
with the agreed-upon key.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWE Encrypted Key is the result of encrypting the
CEK using the result of the key agreement algorithm as the key
encryption key for the corresponding key wrapping algorithm:
+-----------------+-------------------------------------------------+
| "alg" Param | Key Management Algorithm |
| Value | |
+-----------------+-------------------------------------------------+
| ECDH-ES+A128KW | ECDH-ES using Concat KDF and CEK wrapped with |
| | "A128KW" |
| ECDH-ES+A192KW | ECDH-ES using Concat KDF and CEK wrapped with |
| | "A192KW" |
| ECDH-ES+A256KW | ECDH-ES using Concat KDF and CEK wrapped with |
| | "A256KW" |
+-----------------+-------------------------------------------------+
4.6.1. Header Parameters Used for ECDH Key Agreement
The following Header Parameter names are used for key agreement as
defined below.
4.6.1.1. "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 they can be ignored. This
Header Parameter MUST be present and MUST be understood and processed
by implementations when these algorithms are used.
Jones Standards Track [Page 16]
RFC 7518 JSON Web Algorithms (JWA) May 2015
4.6.1.2. "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 producer. Use of this Header Parameter is OPTIONAL. This Header
Parameter MUST be understood and processed by implementations when
these algorithms are used.
4.6.1.3. "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 recipient. Use of this Header Parameter is OPTIONAL. This
Header Parameter MUST be understood and processed by implementations
when these algorithms are used.
4.6.2. 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. In the Direct Key Agreement case,
Data is set to the octets of the ASCII representation of the "enc"
Header Parameter value. In the Key Agreement with Key Wrapping
case, Data is set to the octets of the ASCII representation of the
"alg" (algorithm) Header Parameter value.
Jones Standards Track [Page 17]RFC 7518 JSON Web Algorithms (JWA) May 2015
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. 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. 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 need to specify how the "apu" and "apv" Header
Parameters are used for that application. The "apu" and "apv" values
MUST be distinct, when used. 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 producer and
consumer. Alternatively, applications MAY conduct key derivation in
a manner similar to "Diffie-Hellman Key Agreement Method" [RFC2631]:
in that case, the "apu" parameter MAY either be omitted or represent
a random 512-bit value (analogous to PartyAInfo in Ephemeral-Static
mode in RFC 2631) and the "apv" parameter SHOULD NOT be present.
See Appendix C for an example key agreement computation using this
method.
4.7. 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] and [NIST.800-38D]).
Jones Standards Track [Page 18]RFC 7518 JSON Web Algorithms (JWA) May 2015
Use of an Initialization Vector (IV) of size 96 bits is REQUIRED with
this algorithm. The IV 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.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWE Encrypted Key is the result of encrypting the
CEK using the corresponding algorithm and key size:
+-------------------+---------------------------------------------+
| "alg" Param Value | Key Management Algorithm |
+-------------------+---------------------------------------------+
| A128GCMKW | Key wrapping with AES GCM using 128-bit key |
| A192GCMKW | Key wrapping with AES GCM using 192-bit key |
| A256GCMKW | Key wrapping with AES GCM using 256-bit key |
+-------------------+---------------------------------------------+
4.7.1. Header Parameters Used for AES GCM Key Encryption
The following Header Parameters are used for AES GCM key encryption.
4.7.1.1. "iv" (Initialization Vector) Header Parameter
The "iv" (initialization vector) Header Parameter value is the
base64url-encoded representation of the 96-bit IV value used for the
key encryption operation. This Header Parameter MUST be present and
MUST be understood and processed by implementations when these
algorithms are used.
4.7.1.2. "tag" (Authentication Tag) Header Parameter
The "tag" (authentication tag) Header Parameter value is the
base64url-encoded representation of the 128-bit Authentication Tag
value resulting from the key encryption operation. This Header
Parameter MUST be present and MUST be understood and processed by
implementations when these algorithms are used.
Jones Standards Track [Page 19]RFC 7518 JSON Web Algorithms (JWA) May 2015
4.8. Key Encryption with PBES2
This section defines the specifics of performing password-based
encryption of a JWE CEK, by first deriving a key encryption key from
a user-supplied password using PBES2 schemes as specified in
Section 6.2 of [RFC2898], then by encrypting the JWE CEK using the
derived key.
These algorithms use HMAC SHA-2 algorithms as the Pseudorandom
Function (PRF) for the PBKDF2 key derivation and AES Key Wrap
[RFC3394] for the encryption scheme. The PBES2 password input is an
octet sequence; if the password to be used is represented as a text
string rather than an octet sequence, the UTF-8 encoding of the text
string MUST be used as the octet sequence. The salt parameter MUST
be computed from the "p2s" (PBES2 salt input) Header Parameter value
and the "alg" (algorithm) Header Parameter value as specified in the
"p2s" definition below. The iteration count parameter MUST be
provided as the "p2c" (PBES2 count) 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.
The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWE Encrypted Key is the result of encrypting the
CEK using the result of the corresponding password-based encryption
algorithm as the key encryption key for the corresponding key
wrapping algorithm:
+--------------------+----------------------------------------------+
| "alg" Param Value | Key Management Algorithm |
+--------------------+----------------------------------------------+
| PBES2-HS256+A128KW | PBES2 with HMAC SHA-256 and "A128KW" |
| | wrapping |
| PBES2-HS384+A192KW | PBES2 with HMAC SHA-384 and "A192KW" |
| | wrapping |
| PBES2-HS512+A256KW | PBES2 with HMAC SHA-512 and "A256KW" |
| | wrapping |
+--------------------+----------------------------------------------+
See Appendix C of the JWK specification [JWK] for an example key
encryption computation using "PBES2-HS256+A128KW".
4.8.1. Header Parameters Used for PBES2 Key Encryption
The following Header Parameters are used for Key Encryption with
PBES2.
Jones Standards Track [Page 20]
RFC 7518 JSON Web Algorithms (JWA) May 2015
4.8.1.1. "p2s" (PBES2 Salt Input) Header Parameter
The "p2s" (PBES2 salt input) Header Parameter encodes a Salt Input
value, which is used as part of the PBKDF2 salt value. The "p2s"
value is BASE64URL(Salt Input). This Header Parameter MUST be
present 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 Input value containing 8 or more octets MUST be
used. A new Salt Input value MUST be generated randomly for every
encryption operation; see RFC 4086 [RFC4086] for considerations on
generating random values. The salt value used is (UTF8(Alg) || 0x00
|| Salt Input), where Alg is the "alg" (algorithm) Header Parameter
value.
4.8.1.2. "p2c" (PBES2 Count) Header Parameter
The "p2c" (PBES2 count) Header Parameter contains the PBKDF2
iteration count, represented as a positive JSON integer. This Header
Parameter MUST be present 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.
5. Cryptographic Algorithms for Content Encryption
JWE uses cryptographic algorithms to encrypt and integrity-protect
the plaintext and to integrity-protect the Additional Authenticated
Data.
Jones Standards Track [Page 21]
RFC 7518 JSON Web Algorithms (JWA) May 2015
5.1. "enc" (Encryption Algorithm) Header Parameter Values for JWE
The table below is the set of "enc" (encryption algorithm) Header
Parameter values that are defined by this specification for use with
JWE.
+---------------+----------------------------------+----------------+
| "enc" Param | Content Encryption Algorithm | Implementation |
| Value | | Requirements |
+---------------+----------------------------------+----------------+
| A128CBC-HS256 | AES_128_CBC_HMAC_SHA_256 | Required |
| | authenticated encryption | |
| | algorithm, as defined in Section | |
| | 5.2.3 | |
| A192CBC-HS384 | AES_192_CBC_HMAC_SHA_384 | Optional |
| | authenticated encryption | |
| | algorithm, as defined in Section | |
| | 5.2.4 | |
| A256CBC-HS512 | AES_256_CBC_HMAC_SHA_512 | Required |
| | authenticated encryption | |
| | algorithm, as defined in Section | |
| | 5.2.5 | |
| A128GCM | AES GCM using 128-bit key | Recommended |
| A192GCM | AES GCM using 192-bit key | Optional |
| A256GCM | AES GCM using 256-bit key | Recommended |
+---------------+----------------------------------+----------------+
All also use a JWE Initialization Vector value and produce JWE
Ciphertext and JWE Authentication Tag values.
See Appendix A.3 for a table cross-referencing the JWE "enc"
(encryption algorithm) values defined in this specification with the
equivalent identifiers used by other standards and software packages.
5.2. AES_CBC_HMAC_SHA2 Algorithms
This section defines a family of authenticated encryption algorithms
built using a composition of AES [AES] in Cipher Block Chaining (CBC)
mode [NIST.800-38A] with PKCS #7 padding operations per Section 6.3
of [RFC5652] and HMAC ([RFC2104] and [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 B.
Jones Standards Track [Page 22]
RFC 7518 JSON Web Algorithms (JWA) May 2015
These algorithms are based upon "Authenticated Encryption with AES-
CBC and HMAC-SHA" [AEAD-CBC-SHA], performing the same cryptographic
computations, but with the Initialization Vector (IV) 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
[AEAD-CBC-SHA] and can be used to implement those algorithms.
5.2.1. Conventions Used in Defining AES_CBC_HMAC_SHA2
We use the following notational conventions.
CBC-PKCS7-ENC(X, P) denotes the AES-CBC encryption of P using PKCS
#7 padding utilizing the cipher with the key X.
MAC(Y, M) denotes the application of the MAC to the message M
using the key Y.
5.2.2. 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.
Sections 5.2.2.1 and 5.2.2.2 define the generic encryption and
decryption algorithms. Sections 5.2.3 through 5.2.5 define instances
of AES_CBC_HMAC_SHA2 that specify those details.
5.2.2.1. AES_CBC_HMAC_SHA2 Encryption
The authenticated encryption algorithm takes as input four octet
strings: a secret key K, a plaintext P, Additional Authenticated 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
Additional Authenticated 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.
ENC_KEY consists of the final ENC_KEY_LEN octets of K, in
order.
Jones Standards Track [Page 23]RFC 7518 JSON Web Algorithms (JWA) May 2015
The number of octets in the input key K MUST be the sum of
MAC_KEY_LEN and ENC_KEY_LEN. The values of these parameters are
specified by the Authenticated Encryption algorithms in Sections
5.2.3 through 5.2.5. 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 IV used is a 128-bit value generated randomly or
pseudorandomly for use in the cipher.
3. The plaintext is CBC encrypted using PKCS #7 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 the
Additional Authenticated Data A expressed as a 64-bit unsigned
big-endian integer.
5. A message Authentication Tag T is computed by applying HMAC
[RFC2104] to the following data, in order:
the Additional Authenticated 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 octets 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, Additional Authenticated Data,
Initialization Vector, and ciphertext, respectively.
MAC_KEY = initial MAC_KEY_LEN octets of K,
ENC_KEY = final ENC_KEY_LEN octets of K,
E = CBC-PKCS7-ENC(ENC_KEY, P),
M = MAC(MAC_KEY, A || IV || E || AL),
T = initial T_LEN octets of M.
Jones Standards Track [Page 24]RFC 7518 JSON Web Algorithms (JWA) May 2015
5.2.2.2. AES_CBC_HMAC_SHA2 Decryption
The authenticated decryption operation has five inputs: K, A, IV, 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 5.2.2.1.
2. The integrity and authenticity of A and E are checked by
computing an HMAC with the inputs as in Step 5 of
Section 5.2.2.1. 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 authenticated
decryption operation returns an indication that it failed, and
the operation halts. (But see Section 11.5 of [JWE] for security
considerations on thwarting timing attacks.)
3. The value E is decrypted and the PKCS #7 padding is checked and
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.
5.2.3. 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 CBC mode of operation
as defined in Section 6.2 of [NIST.800-38A], with PKCS #7 padding and
a 128-bit IV value.
The AES_CBC_HMAC_SHA2 parameters specific to AES_128_CBC_HMAC_SHA_256
are:
The input key K is 32 octets long.
ENC_KEY_LEN is 16 octets.
MAC_KEY_LEN is 16 octets.
The SHA-256 hash algorithm is used for the HMAC.
The HMAC-SHA-256 output is truncated to T_LEN=16 octets, by
stripping off the final 16 octets.
Jones Standards Track [Page 25]RFC 7518 JSON Web Algorithms (JWA) May 2015
5.2.4. 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:
The input key K is 48 octets long instead of 32.
ENC_KEY_LEN is 24 octets instead of 16.
MAC_KEY_LEN is 24 octets instead of 16.
SHA-384 is used for the HMAC instead of SHA-256.
The HMAC SHA-384 value is truncated to T_LEN=24 octets instead of
16.
5.2.5. 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:
The input key K is 64 octets long instead of 32.
ENC_KEY_LEN is 32 octets instead of 16.
MAC_KEY_LEN is 32 octets instead of 16.
SHA-512 is used for the HMAC instead of SHA-256.
The HMAC SHA-512 value is truncated to T_LEN=32 octets instead of
16.
5.2.6. Content Encryption with AES_CBC_HMAC_SHA2
This section defines the specifics of performing authenticated
encryption with the AES_CBC_HMAC_SHA2 algorithms.
The CEK is used as the secret key K.
The following "enc" (encryption algorithm) Header Parameter values
are used to indicate that the JWE Ciphertext and JWE Authentication
Tag values have been computed using the corresponding algorithm:
+---------------+---------------------------------------------------+
| "enc" Param | Content Encryption Algorithm |
| Value | |
+---------------+---------------------------------------------------+
| A128CBC-HS256 | AES_128_CBC_HMAC_SHA_256 authenticated encryption |
| | algorithm, as defined in Section 5.2.3 |
| A192CBC-HS384 | AES_192_CBC_HMAC_SHA_384 authenticated encryption |
| | algorithm, as defined in Section 5.2.4 |
| A256CBC-HS512 | AES_256_CBC_HMAC_SHA_512 authenticated encryption |
| | algorithm, as defined in Section 5.2.5 |
+---------------+---------------------------------------------------+
Jones Standards Track [Page 26]RFC 7518 JSON Web Algorithms (JWA) May 2015
5.3. Content Encryption with AES GCM
This section defines the specifics of performing authenticated
encryption with AES in Galois/Counter Mode (GCM) ([AES] and
[NIST.800-38D]).
The CEK is used as the encryption key.
Use of an IV of size 96 bits is REQUIRED with this algorithm.
The requested size of the Authentication Tag output MUST be 128 bits,
regardless of the key size.
The following "enc" (encryption algorithm) Header Parameter values
are used to indicate that the JWE Ciphertext and JWE Authentication
Tag values have been computed using the corresponding algorithm and
key size:
+-------------------+------------------------------+
| "enc" Param Value | Content Encryption Algorithm |
+-------------------+------------------------------+
| A128GCM | AES GCM using 128-bit key |
| A192GCM | AES GCM using 192-bit key |
| A256GCM | AES GCM using 256-bit key |
+-------------------+------------------------------+
An example using this algorithm is shown in Appendix A.1 of [JWE].
6. 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.
Jones Standards Track [Page 27]RFC 7518 JSON Web Algorithms (JWA) May 2015
6.1. "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.
+-------------+--------------------------------+--------------------+
| "kty" Param | Key Type | Implementation |
| Value | | Requirements |
+-------------+--------------------------------+--------------------+
| 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 column indicates
that the requirement strength is likely to be increased in a future
version of the specification.
6.2. Parameters for Elliptic Curve Keys
JWKs can represent Elliptic Curve [DSS] keys. In this case, the
"kty" member value is "EC".
6.2.1. 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 all
Elliptic Curve public keys:
o "crv"
o "x"
The following member MUST also be present for Elliptic Curve public
keys for the three curves defined in the following section:
o "y"
6.2.1.1. "crv" (Curve) Parameter
The "crv" (curve) parameter 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"
Jones Standards Track [Page 28]
RFC 7518 JSON Web Algorithms (JWA) May 2015
These values are registered in the IANA "JSON Web Key Elliptic Curve"
registry defined in Section 7.6. Additional "crv" values can be
registered by other specifications. Specifications registering
additional curves must define what parameters are used to represent
keys for the curves registered. The "crv" value is a case-sensitive
string.
SEC1 [SEC1] point compression is not supported for any of these three
curves.
6.2.1.2. "x" (X Coordinate) Parameter
The "x" (x coordinate) parameter 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.
6.2.1.3. "y" (Y Coordinate) Parameter
The "y" (y coordinate) parameter 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.
6.2.2. 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.
6.2.2.1. "d" (ECC Private Key) Parameter
The "d" (ECC private key) parameter 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 Section 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).
Jones Standards Track [Page 29]
RFC 7518 JSON Web Algorithms (JWA) May 2015
6.3. Parameters for RSA Keys
JWKs can represent RSA [RFC3447] keys. In this case, the "kty"
member value is "RSA". The semantics of the parameters defined below
are the same as those defined in Sections 3.1 and 3.2 of RFC 3447.
6.3.1. Parameters for RSA Public Keys
The following members MUST be present for RSA public keys.
6.3.1.1. "n" (Modulus) Parameter
The "n" (modulus) parameter contains the modulus value for the RSA
public key. It is represented as a Base64urlUInt-encoded value.
Note that implementers have found that some cryptographic libraries
prefix an extra zero-valued octet to the modulus representations they
return, for instance, returning 257 octets for a 2048-bit key, rather
than 256. Implementations using such libraries will need to take
care to omit the extra octet from the base64url-encoded
representation.
6.3.1.2. "e" (Exponent) Parameter
The "e" (exponent) parameter contains the exponent value for the RSA
public key. It is represented as a Base64urlUInt-encoded value.
For instance, when representing the value 65537, the octet sequence
to be base64url-encoded MUST consist of the three octets [1, 0, 1];
the resulting representation for this value is "AQAB".
6.3.2. 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.
6.3.2.1. "d" (Private Exponent) Parameter
The "d" (private exponent) parameter contains the private exponent
value for the RSA private key. It is represented as a Base64urlUInt-
encoded value.
Jones Standards Track [Page 30]
RFC 7518 JSON Web Algorithms (JWA) May 2015
6.3.2.2. "p" (First Prime Factor) Parameter
The "p" (first prime factor) parameter contains the first prime
factor. It is represented as a Base64urlUInt-encoded value.
6.3.2.3. "q" (Second Prime Factor) Parameter
The "q" (second prime factor) parameter contains the second prime
factor. It is represented as a Base64urlUInt-encoded value.
6.3.2.4. "dp" (First Factor CRT Exponent) Parameter
The "dp" (first factor CRT exponent) parameter contains the Chinese
Remainder Theorem (CRT) exponent of the first factor. It is
represented as a Base64urlUInt-encoded value.
6.3.2.5. "dq" (Second Factor CRT Exponent) Parameter
The "dq" (second factor CRT exponent) parameter contains the CRT
exponent of the second factor. It is represented as a Base64urlUInt-
encoded value.
6.3.2.6. "qi" (First CRT Coefficient) Parameter
The "qi" (first CRT coefficient) parameter contains the CRT
coefficient of the second factor. It is represented as a
Base64urlUInt-encoded value.
6.3.2.7. "oth" (Other Primes Info) Parameter
The "oth" (other primes info) parameter 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.
For more information on this case, see the description of the
OtherPrimeInfo parameters in Appendix A.1.2 of RFC 3447 [RFC3447],
upon which the following parameters are modeled. If the consumer of
a JWK does not support private keys with more than two primes and it
encounters a private key that includes the "oth" parameter, then it
MUST NOT use the key. Each array element MUST be an object with the
following members.
6.3.2.7.1. "r" (Prime Factor)
The "r" (prime factor) parameter within an "oth" array member
represents the value of a subsequent prime factor. It is represented
as a Base64urlUInt-encoded value.
Jones Standards Track [Page 31]
RFC 7518 JSON Web Algorithms (JWA) May 2015
6.3.2.7.2. "d" (Factor CRT Exponent)
The "d" (factor CRT exponent) parameter within an "oth" array member
represents the CRT exponent of the corresponding prime factor. It is
represented as a Base64urlUInt-encoded value.
6.3.2.7.3. "t" (Factor CRT Coefficient)
The "t" (factor CRT coefficient) parameter within an "oth" array
member represents the CRT coefficient of the corresponding prime
factor. It is represented as a Base64urlUInt-encoded value.
6.4. Parameters for Symmetric Keys
When the JWK "kty" member value is "oct" (octet sequence), the member
"k" (see Section 6.4.1) 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.
6.4.1. "k" (Key Value) Parameter
The "k" (key value) parameter 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.
7. IANA Considerations
The following registration procedure is used for all the registries
established by this specification.
The registration procedure for values is Specification Required
[RFC5226] after a three-week review period on the
jose-reg-review@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 Experts may approve registration
once they are satisfied that such a specification will be published.
Registration requests sent to the mailing list for review should use
an appropriate subject (e.g., "Request to register algorithm:
example").
Within the review period, the Designated Experts 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.
Jones Standards Track [Page 32]
RFC 7518 JSON Web Algorithms (JWA) May 2015
Registration requests that are undetermined for a period longer than
21 days can be brought to the IESG's attention (using the
iesg@ietf.org mailing list) for resolution.
Criteria that should be applied by the Designated Experts include
determining whether the proposed registration duplicates existing
functionality, whether it is likely to be of general applicability or
useful only for a single application, and whether the registration
description is clear.
IANA must only accept registry updates from the Designated Experts
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
Experts.
7.1. 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 algorithm) Header Parameters. The
registry records the algorithm name, the algorithm description, the
algorithm usage locations, the implementation requirements, the
change controller, and a reference to the specification that defines
it. The same algorithm name can be registered multiple times,
provided that the sets of usage locations are disjoint.
It is suggested that the length of the key be included in the
algorithm name when multiple variations of algorithms are being
registered that use keys of different lengths and the key lengths for
each need to be fixed (for instance, because they will be created by
key derivation functions). This allows readers of the JSON text to
more easily make security decisions.
The Designated Experts should perform reasonable due diligence that
algorithms being registered either are currently considered
cryptographically credible or are being registered as Deprecated or
Prohibited.
Jones Standards Track [Page 33]
RFC 7518 JSON Web Algorithms (JWA) May 2015
The implementation requirements of an algorithm may be changed over
time as the cryptographic landscape 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 after review by the Designated Experts, with the new
specification defining the revised implementation requirements level.
7.1.1. Registration Template
Algorithm Name:
The name requested (e.g., "HS256"). This name is a case-sensitive
ASCII string. Names may not match other registered names in a
case-insensitive manner unless the Designated Experts state that
there is a compelling reason to allow an exception.
Algorithm Description:
Brief description of the algorithm (e.g., "HMAC using SHA-256").
Algorithm Usage Location(s):
The algorithm usage locations. This must be one or more of the
values "alg" or "enc" if the algorithm is to be used with JWS or
JWE. The value "JWK" is used if the algorithm identifier will be
used as a JWK "alg" member value, but will not be used with JWS or
JWE; this could be the case, for instance, for non-authenticated
encryption algorithms. Other values may be used with the approval
of a Designated Expert.
JOSE Implementation Requirements:
The algorithm implementation requirements for JWS and JWE, which
must be one the words Required, Recommended, Optional, Deprecated,
or Prohibited. 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. Any
identifiers registered for non-authenticated encryption algorithms
or other algorithms that are otherwise unsuitable for direct use
as JWS or JWE algorithms must be registered as "Prohibited".
Change Controller:
For Standards Track RFCs, list the "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.
Jones Standards Track [Page 34]RFC 7518 JSON Web Algorithms (JWA) May 2015
Specification Document(s):
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
Algorithm Analysis Documents(s):
References to a publication or publications in well-known
cryptographic conferences, by national standards bodies, or by
other authoritative sources analyzing the cryptographic soundness
of the algorithm to be registered. The Designated Experts may
require convincing evidence of the cryptographic soundness of a
new algorithm to be provided with the registration request unless
the algorithm is being registered as Deprecated or Prohibited.
Having gone through working group and IETF review, the initial
registrations made by this document are exempt from the need to
provide this information.
7.1.2. Initial Registry Contents
o Algorithm Name: "HS256"
o Algorithm Description: HMAC using SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 3.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "HS384"
o Algorithm Description: HMAC using SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "HS512"
o Algorithm Description: HMAC using SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 35]RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "RS256"
o Algorithm Description: RSASSA-PKCS1-v1_5 using SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 3.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RS384"
o Algorithm Description: RSASSA-PKCS1-v1_5 using SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RS512"
o Algorithm Description: RSASSA-PKCS1-v1_5 using SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ES256"
o Algorithm Description: ECDSA using P-256 and SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 3.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ES384"
o Algorithm Description: ECDSA using P-384 and SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ES512"
o Algorithm Description: ECDSA using P-521 and SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 36]
RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "PS256"
o Algorithm Description: RSASSA-PSS using SHA-256 and MGF1 with
SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PS384"
o Algorithm Description: RSASSA-PSS using SHA-384 and MGF1 with
SHA-384
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PS512"
o Algorithm Description: RSASSA-PSS using SHA-512 and MGF1 with
SHA-512
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "none"
o Algorithm Description: No digital signature or MAC performed
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 3.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RSA1_5"
o Algorithm Description: RSAES-PKCS1-v1_5
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended-
o Change Controller: IESG
o Specification Document(s): Section 4.2 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 37]RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "RSA-OAEP"
o Algorithm Description: RSAES OAEP using default parameters
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 4.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "RSA-OAEP-256"
o Algorithm Description: RSAES OAEP using SHA-256 and MGF1 with
SHA-256
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A128KW"
o Algorithm Description: AES Key Wrap using 128-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192KW"
o Algorithm Description: AES Key Wrap using 192-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256KW"
o Algorithm Description: AES Key Wrap using 256-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "dir"
o Algorithm Description: Direct use of a shared symmetric key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 38]RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "ECDH-ES"
o Algorithm Description: ECDH-ES using Concat KDF
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES+A128KW"
o Algorithm Description: ECDH-ES using Concat KDF and "A128KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES+A192KW"
o Algorithm Description: ECDH-ES using Concat KDF and "A192KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "ECDH-ES+A256KW"
o Algorithm Description: ECDH-ES using Concat KDF and "A256KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 4.6 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A128GCMKW"
o Algorithm Description: Key wrapping with AES GCM using 128-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.7 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 39]RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "A192GCMKW"
o Algorithm Description: Key wrapping with AES GCM using 192-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.7 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256GCMKW"
o Algorithm Description: Key wrapping with AES GCM using 256-bit key
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.7 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PBES2-HS256+A128KW"
o Algorithm Description: PBES2 with HMAC SHA-256 and "A128KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PBES2-HS384+A192KW"
o Algorithm Description: PBES2 with HMAC SHA-384 and "A192KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "PBES2-HS512+A256KW"
o Algorithm Description: PBES2 with HMAC SHA-512 and "A256KW"
wrapping
o Algorithm Usage Location(s): "alg"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 4.8 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 40]RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "A128CBC-HS256"
o Algorithm Description: AES_128_CBC_HMAC_SHA_256 authenticated
encryption algorithm
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 5.2.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192CBC-HS384"
o Algorithm Description: AES_192_CBC_HMAC_SHA_384 authenticated
encryption algorithm
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 5.2.4 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A256CBC-HS512"
o Algorithm Description: AES_256_CBC_HMAC_SHA_512 authenticated
encryption algorithm
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 5.2.5 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A128GCM"
o Algorithm Description: AES GCM using 128-bit key
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 5.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
o Algorithm Name: "A192GCM"
o Algorithm Description: AES GCM using 192-bit key
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 5.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
Jones Standards Track [Page 41]RFC 7518 JSON Web Algorithms (JWA) May 2015
o Algorithm Name: "A256GCM"
o Algorithm Description: AES GCM using 256-bit key
o Algorithm Usage Location(s): "enc"
o JOSE Implementation Requirements: Recommended
o Change Controller: IESG
o Specification Document(s): Section 5.3 of RFC 7518
o Algorithm Analysis Documents(s): n/a
7.2. Header Parameter Names Registration
This section registers the Header Parameter names defined in Sections
4.6.1, 4.7.1, and 4.8.1 of this specification in the IANA "JSON Web
Signature and Encryption Header Parameters" registry established by
[JWS].
7.2.1. Registry Contents
o Header Parameter Name: "epk"
o Header Parameter Description: Ephemeral Public Key
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.6.1.1 of RFC 7518
o Header Parameter Name: "apu"
o Header Parameter Description: Agreement PartyUInfo
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.6.1.2 of RFC 7518
o Header Parameter Name: "apv"
o Header Parameter Description: Agreement PartyVInfo
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.6.1.3 of RFC 7518
o Header Parameter Name: "iv"
o Header Parameter Description: Initialization Vector
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.1 of RFC 7518
o Header Parameter Name: "tag"
o Header Parameter Description: Authentication Tag
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.7.1.2 of RFC 7518
Jones Standards Track [Page 42]
RFC 7518 JSON Web Algorithms (JWA) May 2015
o Header Parameter Name: "p2s"
o Header Parameter Description: PBES2 Salt Input
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.8.1.1 of RFC 7518
o Header Parameter Name: "p2c"
o Header Parameter Description: PBES2 Count
o Header Parameter Usage Location(s): JWE
o Change Controller: IESG
o Specification Document(s): Section 4.8.1.2 of RFC 7518
7.3. 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.
7.3.1. Registration Template
Compression Algorithm Value:
The name requested (e.g., "DEF"). 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 Experts state that
there is a compelling reason to allow an exception.
Compression Algorithm Description:
Brief description of the compression algorithm (e.g., "DEFLATE").
Change Controller:
For Standards Track RFCs, list "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 or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
Jones Standards Track [Page 43]RFC 7518 JSON Web Algorithms (JWA) May 2015
7.3.2. Initial Registry Contents
o Compression Algorithm Value: "DEF"
o Compression Algorithm Description: DEFLATE
o Change Controller: IESG
o Specification Document(s): JSON Web Encryption (JWE) [JWE]
7.4. 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 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 after review by the Designated Experts, with the new
specification defining the revised implementation requirements level.
7.4.1. Registration Template
"kty" Parameter Value:
The name requested (e.g., "EC"). 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 Experts state that
there is a compelling reason to allow an exception.
Key Type Description:
Brief description of the Key Type (e.g., "Elliptic Curve").
Change Controller:
For Standards Track RFCs, list "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.
Jones Standards Track [Page 44]RFC 7518 JSON Web Algorithms (JWA) May 2015
JOSE Implementation Requirements:
The key type implementation requirements for JWS and JWE, which
must be one the words Required, Recommended, Optional, Deprecated,
or Prohibited. 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.
Specification Document(s):
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
7.4.2. Initial Registry Contents
This section registers the values defined in Section 6.1.
o "kty" Parameter Value: "EC"
o Key Type Description: Elliptic Curve
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 6.2 of RFC 7518
o "kty" Parameter Value: "RSA"
o Key Type Description: RSA
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 6.3 of RFC 7518
o "kty" Parameter Value: "oct"
o Key Type Description: Octet Sequence
o JOSE Implementation Requirements: Required
o Change Controller: IESG
o Specification Document(s): Section 6.4 of RFC 7518
7.5. JSON Web Key Parameters Registration
This section registers the parameter names defined in Sections 6.2,
6.3, and 6.4 of this specification in the IANA "JSON Web Key
Parameters" registry established by [JWK].
Jones Standards Track [Page 45]RFC 7518 JSON Web Algorithms (JWA) May 2015
7.5.1. Registry Contents
o Parameter Name: "crv"
o Parameter Description: Curve
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.1 of RFC 7518
o Parameter Name: "x"
o Parameter Description: X Coordinate
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.2 of RFC 7518
o Parameter Name: "y"
o Parameter Description: Y Coordinate
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.3 of RFC 7518
o Parameter Name: "d"
o Parameter Description: ECC Private Key
o Used with "kty" Value(s): "EC"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.2.2.1 of RFC 7518
o Parameter Name: "n"
o Parameter Description: Modulus
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.3.1.1 of RFC 7518
o Parameter Name: "e"
o Parameter Description: Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Public
o Change Controller: IESG
o Specification Document(s): Section 6.3.1.2 of RFC 7518
Jones Standards Track [Page 46]
RFC 7518 JSON Web Algorithms (JWA) May 2015
o Parameter Name: "d"
o Parameter Description: Private Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.1 of RFC 7518
o Parameter Name: "p"
o Parameter Description: First Prime Factor
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.2 of RFC 7518
o Parameter Name: "q"
o Parameter Description: Second Prime Factor
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.3 of RFC 7518
o Parameter Name: "dp"
o Parameter Description: First Factor CRT Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.4 of RFC 7518
o Parameter Name: "dq"
o Parameter Description: Second Factor CRT Exponent
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.5 of RFC 7518
o Parameter Name: "qi"
o Parameter Description: First CRT Coefficient
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.6 of RFC 7518
Jones Standards Track [Page 47]
RFC 7518 JSON Web Algorithms (JWA) May 2015
o Parameter Name: "oth"
o Parameter Description: Other Primes Info
o Used with "kty" Value(s): "RSA"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.3.2.7 of RFC 7518
o Parameter Name: "k"
o Parameter Description: Key Value
o Used with "kty" Value(s): "oct"
o Parameter Information Class: Private
o Change Controller: IESG
o Specification Document(s): Section 6.4.1 of RFC 7518
7.6. JSON Web Key Elliptic Curve Registry
This section 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 6.2.1.1.
The implementation requirements of a curve may be changed over time
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
after review by the Designated Experts, with the new specification
defining the revised implementation requirements level.
7.6.1. Registration Template
Curve Name:
The name requested (e.g., "P-256"). 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 Experts state that
there is a compelling reason to allow an exception.
Curve Description:
Brief description of the curve (e.g., "P-256 Curve").
JOSE Implementation Requirements:
The curve implementation requirements for JWS and JWE, which must
be one the words Required, Recommended, Optional, Deprecated, or
Prohibited. Optionally, the word can be followed by a "+" or "-".
Jones Standards Track [Page 48]RFC 7518 JSON Web Algorithms (JWA) May 2015
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, list "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 or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
7.6.2. Initial Registry Contents
o Curve Name: "P-256"
o Curve Description: P-256 Curve
o JOSE Implementation Requirements: Recommended+
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.1 of RFC 7518
o Curve Name: "P-384"
o Curve Description: P-384 Curve
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.1 of RFC 7518
o Curve Name: "P-521"
o Curve Description: P-521 Curve
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 6.2.1.1 of RFC 7518
8. Security Considerations
All of the security issues that are pertinent to any cryptographic
application must be addressed by JWS/JWE/JWK agents. Among these
issues are protecting the user's asymmetric private and symmetric
secret keys and employing countermeasures to various attacks.
The security considerations in [AES], [DSS], [JWE], [JWK], [JWS],
[NIST.800-38D], [NIST.800-56A], [NIST.800-107], [RFC2104], [RFC3394],
[RFC3447], [RFC5116], [RFC6090], and [SHS] apply to this
specification.
Jones Standards Track [Page 49]RFC 7518 JSON Web Algorithms (JWA) May 2015
8.1. Cryptographic Agility
Implementers should be aware that cryptographic algorithms become
weaker with time. As new cryptanalysis techniques are developed and
computing performance improves, the work factor to break a particular
cryptographic algorithm will be reduced. Therefore, implementers and
deployments must be prepared for the set of algorithms that are
supported and used to change over time. Thus, cryptographic
algorithm implementations should be modular, allowing new algorithms
to be readily inserted.
8.2. 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. See NIST SP 800-57
[NIST.800-57] for specific guidance on key lifetimes.
8.3. RSAES-PKCS1-v1_5 Security Considerations
While Section 8 of RFC 3447 [RFC3447] explicitly calls for people not
to adopt RSASSA-PKCS1-v1_5 for new applications and instead requests
that people transition to RSASSA-PSS, this specification does include
RSASSA-PKCS1-v1_5, for interoperability reasons, because it is
commonly implemented.
Keys used with RSAES-PKCS1-v1_5 must follow the constraints in
Section 7.2 of RFC 3447. Also, keys with a low public key exponent
value, as described in Section 3 of "Twenty Years of Attacks on the
RSA Cryptosystem" [Boneh99], must not be used.
8.4. 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.
An IV value MUST NOT ever 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.
Jones Standards Track [Page 50]
RFC 7518 JSON Web Algorithms (JWA) May 2015
8.5. Unsecured JWS Security Considerations
Unsecured JWSs (JWSs that use the "alg" value "none") provide no
integrity protection. Thus, they must only be used in contexts in
which the payload is secured by means other than a digital signature
or MAC value, or they need not be secured.
An example means of preventing accepting Unsecured JWSs by default is
for the "verify" method of a hypothetical JWS software library to
have a Boolean "acceptUnsecured" 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 Unsecured JWS values if
"none" is not in that list.
The following example illustrates the reasons for not accepting
Unsecured JWSs at a global level. Suppose an application accepts
JWSs over two channels, (1) HTTP and (2) HTTPS with client
authentication. It requires a JWS Signature on objects received over
HTTP, but accepts Unsecured JWSs over HTTPS. If the application were
to globally indicate that "none" is acceptable, then an attacker
could provide it with an Unsecured JWS 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 "acceptUnsecured" to "true" for the first
hypothetical JWS software library above), but not for each object
received over HTTP.
8.6. 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
supply content using keys that would result in excessive
cryptographic processing, for example, keys larger than those
mandated in this specification. Implementations should set and
enforce upper limits on the key sizes they accept. Section 5.6.1
(Comparable Algorithm Strengths) of NIST SP 800-57 [NIST.800-57]
contains statements on largest approved key sizes that may be
applicable.
8.7. Reusing Key Material when Encrypting Keys
It is NOT RECOMMENDED to reuse the same entire set of 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
Jones Standards Track [Page 51]
RFC 7518 JSON Web Algorithms (JWA) May 2015
preventing reuse is to always generate at least one new piece of key
material for each encryption operation (e.g., a new Content
Encryption Key, a new IV, and/or a new PBES2 Salt), based on the
considerations noted in this document as well as from RFC 4086
[RFC4086].
8.8. Password Considerations
Passwords are vulnerable to a number of attacks. To help mitigate
some of these limitations, this document applies principles from RFC
2898 [RFC2898] to derive cryptographic keys from user-supplied
passwords.
However, the strength of the password still has a significant impact.
A high-entropy password has greater resistance to dictionary attacks.
[NIST.800-63-2] contains guidelines for estimating password entropy,
which can help applications and users generate stronger passwords.
An ideal password is one that is as large as (or larger than) the
derived key length. However, passwords larger than a certain
algorithm-specific size are first hashed, which reduces an attacker's
effective search space to the length of the hash algorithm. It is
RECOMMENDED that a password used for "PBES2-HS256+A128KW" be no
shorter than 16 octets and no longer than 128 octets and a password
used for "PBES2-HS512+A256KW" be no shorter than 32 octets and no
longer than 128 octets long.
Still, care needs to be taken in where and how password-based
encryption is used. These algorithms can still be susceptible to
dictionary-based attacks if the iteration count is too small; this is
of particular concern if these algorithms are used to protect data
that an attacker can have indefinite number of attempts to circumvent
the protection, such as protected data stored on a file system.
8.9. Key Entropy and Random Values
See Section 10.1 of [JWS] for security considerations on key entropy
and random values.
8.10. Differences between Digital Signatures and MACs
See Section 10.5 of [JWS] for security considerations on differences
between digital signatures and MACs.
Jones Standards Track [Page 52]
RFC 7518 JSON Web Algorithms (JWA) May 2015
8.11. Using Matching Algorithm Strengths
See Section 11.3 of [JWE] for security considerations on using
matching algorithm strengths.
8.12. Adaptive Chosen-Ciphertext Attacks
See Section 11.4 of [JWE] for security considerations on adaptive
chosen-ciphertext attacks.
8.13. Timing Attacks
See Section 10.9 of [JWS] and Section 11.5 of [JWE] for security
considerations on timing attacks.
8.14. RSA Private Key Representations and Blinding
See Section 9.3 of [JWK] for security considerations on RSA private
key representations and blinding.
9. 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 perform the steps outlined in [PRECIS] to prepare a
password supplied directly by a user before performing key derivation
and encryption.
10. References
10.1. Normative References
[AES] National Institute of Standards and Technology (NIST),
"Advanced Encryption Standard (AES)", FIPS PUB 197,
November 2001, <http://csrc.nist.gov/publications/
fips/fips197/fips-197.pdf>.
[Boneh99] "Twenty Years of Attacks on the RSA Cryptosystem", Notices
of the American Mathematical Society (AMS), Vol. 46,
No. 2, pp. 203-213, 1999, <http://crypto.stanford.edu/
~dabo/pubs/papers/RSA-survey.pdf>.
Jones Standards Track [Page 53]RFC 7518 JSON Web Algorithms (JWA) May 2015
[DSS] National Institute of Standards and Technology (NIST),
"Digital Signature Standard (DSS)", FIPS PUB 186-4, July
2013, <http://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.186-4.pdf>.
[JWE] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<http://www.rfc-editor.org/info/rfc7516>.
[JWK] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[NIST.800-38A]
National Institute of Standards and Technology (NIST),
"Recommendation for Block Cipher Modes of Operation", NIST
Special Publication 800-38A, December 2001,
<http://csrc.nist.gov/publications/nistpubs/800-38a/
sp800-38a.pdf>.
[NIST.800-38D]
National Institute of Standards and Technology (NIST),
"Recommendation for Block Cipher Modes of Operation:
Galois/Counter Mode (GCM) and GMAC", NIST Special
Publication 800-38D, December 2001,
<http://csrc.nist.gov/publications/nistpubs/800-38D/
SP-800-38D.pdf>.
[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,
<http://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-56Ar2.pdf>.
[NIST.800-57]
National Institute of Standards and Technology (NIST),
"Recommendation for Key Management - Part 1: General
(Revision 3)", NIST Special Publication 800-57, Part 1,
Revision 3, July 2012, <http://csrc.nist.gov/publications/
nistpubs/800-57/sp800-57_part1_rev3_general.pdf>.
Jones Standards Track [Page 54]RFC 7518 JSON Web Algorithms (JWA) May 2015
[RFC20] Cerf, V., "ASCII format for Network Interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<http://www.rfc-editor.org/info/rfc20>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
Keyed-Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<http://www.rfc-editor.org/info/rfc2104>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography
Specification Version 2.0", RFC 2898,
DOI 10.17487/RFC2898, September 2000,
<http://www.rfc-editor.org/info/rfc2898>.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
September 2002, <http://www.rfc-editor.org/info/rfc3394>.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February
2003, <http://www.rfc-editor.org/info/rfc3447>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256,
HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007,
<http://www.rfc-editor.org/info/rfc4868>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<http://www.rfc-editor.org/info/rfc4949>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<http://www.rfc-editor.org/info/rfc5652>.
Jones Standards Track [Page 55]RFC 7518 JSON Web Algorithms (JWA) May 2015
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090,
DOI 10.17487/RFC6090, February 2011,
<http://www.rfc-editor.org/info/rfc6090>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.
[SEC1] Standards for Efficient Cryptography Group, "SEC 1:
Elliptic Curve Cryptography", Version 2.0, May 2009,
<http://www.secg.org/sec1-v2.pdf>.
[SHS] National Institute of Standards and Technology (NIST),
"Secure Hash Standard (SHS)", FIPS PUB 180-4, March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>.
[UNICODE] The Unicode Consortium, "The Unicode Standard",
<http://www.unicode.org/versions/latest/>.
10.2. Informative References
[AEAD-CBC-SHA]
McGrew, D., Foley, J., and K. Paterson, "Authenticated
Encryption with AES-CBC and HMAC-SHA", Work in Progress,
draft-mcgrew-aead-aes-cbc-hmac-sha2-05, July 2014.
[CanvasApp]
Facebook, "Canvas Applications", 2010,
<http://developers.facebook.com/docs/authentication/
canvas>.
[JCA] Oracle, "Java Cryptography Architecture (JCA) Reference
Guide", 2014, <http://docs.oracle.com/javase/8/docs/techno
tes/guides/security/crypto/CryptoSpec.html>.
[JSE] Bradley, J. and N. Sakimura (editor), "JSON Simple
Encryption", September 2010,
<http://jsonenc.info/enc/1.0/>.
[JSMS] Rescorla, E. and J. Hildebrand, "JavaScript Message
Security Format", Work in Progress,
draft-rescorla-jsms-00, March 2011.
[JSS] Bradley, J. and N. Sakimura, Ed., "JSON Simple Sign 1.0",
Draft 01, September 2010, <http://jsonenc.info/jss/1.0/>.
Jones Standards Track [Page 56]RFC 7518 JSON Web Algorithms (JWA) May 2015
[JWE-JWK] Miller, M., "Using JavaScript Object Notation (JSON) Web
Encryption (JWE) for Protecting JSON Web Key (JWK)
Objects", Work in Progress,
draft-miller-jose-jwe-protected-jwk-02, June 2013.
[MagicSignatures]
Panzer, J., Ed., Laurie, B., and D. Balfanz, "Magic
Signatures", January 2011,
<http://salmon-protocol.googlecode.com/svn/trunk/
draft-panzer-magicsig-01.html>.
[NIST.800-107]
National Institute of Standards and Technology (NIST),
"Recommendation for Applications Using Approved Hash
Algorithms", NIST Special Publication 800-107, Revision 1,
August 2012, <http://csrc.nist.gov/publications/
nistpubs/800-107-rev1/sp800-107-rev1.pdf>.
[NIST.800-63-2]
National Institute of Standards and Technology (NIST),
"Electronic Authentication Guideline", NIST Special
Publication 800-63-2, August 2013,
<http://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-63-2.pdf>.
[PRECIS] Saint-Andre, P. and A. Melnikov, "Preparation,
Enforcement, and Comparison of Internationalized Strings
Representing Usernames and Passwords", Work in Progress,
draft-ietf-precis-saslprepbis-16, April 2015.
[RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method",
RFC 2631, DOI 10.17487/RFC2631, June 1999,
<http://www.rfc-editor.org/info/rfc2631>.
[RFC3275] Eastlake 3rd, D., Reagle, J., and D. Solo, "(Extensible
Markup Language) XML-Signature Syntax and Processing",
RFC 3275, DOI 10.17487/RFC3275, March 2002,
<http://www.rfc-editor.org/info/rfc3275>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<http://www.rfc-editor.org/info/rfc5116>.
Jones Standards Track [Page 57]RFC 7518 JSON Web Algorithms (JWA) May 2015
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[W3C.NOTE-xmldsig-core2-20130411]
Eastlake, D., Reagle, J., Solo, D., Hirsch, F., Roessler,
T., Yiu, K., Datta, P., and S. Cantor, "XML Signature
Syntax and Processing Version 2.0", World Wide Web
Consortium Note NOTE-xmldsig-core2-20130411, April 2013,
<http://www.w3.org/TR/2013/NOTE-xmldsig-core2-20130411/>.
[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>.
[W3C.REC-xmlenc-core1-20130411]
Eastlake, D., Reagle, J., Hirsch, F., and T. Roessler,
"XML Encryption Syntax and Processing Version 1.1", World
Wide Web Consortium Recommendation REC-xmlenc-
core1-20130411, April 2013,
<http://www.w3.org/TR/2013/REC-xmlenc-core1-20130411/>.
Jones Standards Track [Page 58]RFC 7518 JSON Web Algorithms (JWA) May 2015
Appendix A. Algorithm Identifier Cross-Reference
This appendix contains tables cross-referencing the cryptographic
algorithm identifier values defined in this specification with the
equivalent identifiers used by other standards and software packages.
See XML DSIG [RFC3275], XML DSIG 2.0
[W3C.NOTE-xmldsig-core2-20130411], XML Encryption
[W3C.REC-xmlenc-core-20021210], XML Encryption 1.1
[W3C.REC-xmlenc-core1-20130411], and Java Cryptography Architecture
[JCA] for more information about the names defined by those
documents.
Jones Standards Track [Page 59]
RFC 7518 JSON Web Algorithms (JWA) May 2015
A.1. Digital Signature/MAC Algorithm Identifier Cross-Reference
This section contains a table cross-referencing the JWS digital
signature and MAC "alg" (algorithm) values defined in this
specification with the equivalent identifiers used by other standards
and software packages.
+-------------------------------------------------------------------+
| JWS | XML DSIG |
| | JCA | OID |
+-------------------------------------------------------------------+
| HS256 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 |
| | HmacSHA256 | 1.2.840.113549.2.9 |
+-------------------------------------------------------------------+
| HS384 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha384 |
| | HmacSHA384 | 1.2.840.113549.2.10 |
+-------------------------------------------------------------------+
| HS512 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha512 |
| | HmacSHA512 | 1.2.840.113549.2.11 |
+-------------------------------------------------------------------+
| RS256 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha256 |
| | SHA256withRSA | 1.2.840.113549.1.1.11 |
+-------------------------------------------------------------------+
| RS384 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha384 |
| | SHA384withRSA | 1.2.840.113549.1.1.12 |
+-------------------------------------------------------------------+
| RS512 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha512 |
| | SHA512withRSA | 1.2.840.113549.1.1.13 |
+-------------------------------------------------------------------+
| ES256 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256 |
| | SHA256withECDSA | 1.2.840.10045.4.3.2 |
+-------------------------------------------------------------------+
| ES384 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384 |
| | SHA384withECDSA | 1.2.840.10045.4.3.3 |
+-------------------------------------------------------------------+
| ES512 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512 |
| | SHA512withECDSA | 1.2.840.10045.4.3.4 |
+-------------------------------------------------------------------+
| PS256 | http://www.w3.org/2007/05/xmldsig-more#sha256-rsa-MGF1 |
| | SHA256withRSAandMGF1 | 1.2.840.113549.1.1.10 |
+-------------------------------------------------------------------+
| PS384 | http://www.w3.org/2007/05/xmldsig-more#sha384-rsa-MGF1 |
| | SHA384withRSAandMGF1 | 1.2.840.113549.1.1.10 |
+-------------------------------------------------------------------+
| PS512 | http://www.w3.org/2007/05/xmldsig-more#sha512-rsa-MGF1 |
| | SHA512withRSAandMGF1 | 1.2.840.113549.1.1.10 |
+-------------------------------------------------------------------+
Jones Standards Track [Page 60]
RFC 7518 JSON Web Algorithms (JWA) May 2015
A.2. Key Management Algorithm Identifier Cross-Reference
This section contains a table cross-referencing the JWE "alg"
(algorithm) values defined in this specification with the equivalent
identifiers used by other standards and software packages.
+-------------------------------------------------------------------+
| JWE | XML ENC |
| | JCA | OID |
+-------------------------------------------------------------------+
| RSA1_5 | http://www.w3.org/2001/04/xmlenc#rsa-1_5 |
| | RSA/ECB/PKCS1Padding | 1.2.840.113549.1.1.1 |
+-------------------------------------------------------------------+
| RSA-OAEP | http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p |
| | RSA/ECB/OAEPWithSHA-1AndMGF1Padding | 1.2.840.113549.1.1.7 |
+-------------------------------------------------------------------+
| RSA-OAEP-256 | http://www.w3.org/2009/xmlenc11#rsa-oaep |
| | & http://www.w3.org/2009/xmlenc11#mgf1sha256 |
| | RSA/ECB/OAEPWithSHA-256AndMGF1Padding | |
| | & MGF1ParameterSpec.SHA256 | 1.2.840.113549.1.1.7 |
+-------------------------------------------------------------------+
| ECDH-ES | http://www.w3.org/2009/xmlenc11#ECDH-ES |
| | ECDH | 1.3.132.1.12 |
+-------------------------------------------------------------------+
| A128KW | http://www.w3.org/2001/04/xmlenc#kw-aes128 |
| | AESWrap | 2.16.840.1.101.3.4.1.5 |
+-------------------------------------------------------------------+
| A192KW | http://www.w3.org/2001/04/xmlenc#kw-aes192 |
| | AESWrap | 2.16.840.1.101.3.4.1.25 |
+-------------------------------------------------------------------+
| A256KW | http://www.w3.org/2001/04/xmlenc#kw-aes256 |
| | AESWrap | 2.16.840.1.101.3.4.1.45 |
+-------------------------------------------------------------------+
Jones Standards Track [Page 61]
RFC 7518 JSON Web Algorithms (JWA) May 2015
A.3. Content Encryption Algorithm Identifier Cross-Reference
This section contains a table cross-referencing the JWE "enc"
(encryption algorithm) values defined in this specification with the
equivalent identifiers used by other standards and software packages.
For the composite algorithms "A128CBC-HS256", "A192CBC-HS384", and
"A256CBC-HS512", the corresponding AES-CBC algorithm identifiers are
listed.
+-------------------------------------------------------------------+
| JWE | XML ENC |
| | JCA | OID |
+-------------------------------------------------------------------+
| A128CBC-HS256 | http://www.w3.org/2001/04/xmlenc#aes128-cbc |
| | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.2 |
+-------------------------------------------------------------------+
| A192CBC-HS384 | http://www.w3.org/2001/04/xmlenc#aes192-cbc |
| | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.22 |
+-------------------------------------------------------------------+
| A256CBC-HS512 | http://www.w3.org/2001/04/xmlenc#aes256-cbc |
| | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.42 |
+-------------------------------------------------------------------+
| A128GCM | http://www.w3.org/2009/xmlenc11#aes128-gcm |
| | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.6 |
+-------------------------------------------------------------------+
| A192GCM | http://www.w3.org/2009/xmlenc11#aes192-gcm |
| | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.26 |
+-------------------------------------------------------------------+
| A256GCM | http://www.w3.org/2009/xmlenc11#aes256-gcm |
| | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.46 |
+-------------------------------------------------------------------+
Appendix B. 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 5.2. They are
also intended to correspond to test cases that may appear in a future
version of [AEAD-CBC-SHA], demonstrating that the cryptographic
computations performed are the same.
The variable names are those defined in Section 5.2. All values are
hexadecimal.
Jones Standards Track [Page 62]
RFC 7518 JSON Web Algorithms (JWA) May 2015
B.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 Standards Track [Page 63]RFC 7518 JSON Web Algorithms (JWA) May 2015
B.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 Standards Track [Page 64]RFC 7518 JSON Web Algorithms (JWA) May 2015
B.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 Standards Track [Page 65]RFC 7518 JSON Web Algorithms (JWA) May 2015
Appendix C. Example ECDH-ES Key Agreement Computation
This example uses ECDH-ES Key Agreement and the Concat KDF to derive
the CEK in the manner described in Section 4.6. 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 a 128-bit key ("enc"
value "A128GCM").
In this example, a producer Alice is encrypting content to a consumer
Bob. The producer (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 consumer'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. The
"apu" (agreement PartyUInfo) Header Parameter value is the base64url
encoding of the UTF-8 string "Alice" and the "apv" (agreement
PartyVInfo) Header Parameter value is the base64url encoding of the
UTF-8 string "Bob". The "epk" (ephemeral public key) Header
Parameter is used to communicate the producer's (Alice's) ephemeral
public key value to the consumer (Bob).
Jones Standards Track [Page 66]RFC 7518 JSON Web Algorithms (JWA) May 2015
{"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 following the octet sequence (using JSON array
notation):
[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 ASCII 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].
Jones Standards Track [Page 67]RFC 7518 JSON Web Algorithms (JWA) May 2015
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:
[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:
VqqN6vgjbSBcIijNcacQGg
Jones Standards Track [Page 68]RFC 7518 JSON Web Algorithms (JWA) May 2015
Acknowledgements
Solutions for signing and encrypting JSON content were previously
explored by "Magic Signatures" [MagicSignatures], "JSON Simple Sign
1.0" [JSS], "Canvas Applications" [CanvasApp], "JSON Simple
Encryption" [JSE], and "JavaScript Message Security Format" [JSMS],
all of which influenced this document.
The "Authenticated Encryption with AES-CBC and HMAC-SHA"
[AEAD-CBC-SHA] 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 [AEAD-CBC-SHA] by John Foley.
Matt Miller wrote "Using JavaScript Object Notation (JSON) Web
Encryption (JWE) for Protecting JSON Web Key (JWK) Objects"
[JWE-JWK], upon which the password-based encryption content of this
document is based.
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, Carsten Bormann, John Bradley, Brian
Campbell, Alissa Cooper, Breno de Medeiros, Vladimir Dzhuvinov, Roni
Even, Stephen Farrell, Yaron Y. Goland, Dick Hardt, Joe Hildebrand,
Jeff Hodges, Edmund Jay, Charlie Kaufman, Barry Leiba, James Manger,
Matt Miller, Kathleen Moriarty, Tony Nadalin, Axel Nennker, John
Panzer, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat Sakimura,
Jim Schaad, Hannes Tschofenig, and Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
Sean Turner, Stephen Farrell, and Kathleen Moriarty served as
Security Area Directors during the creation of this specification.
Author's Address
Michael B. Jones
Microsoft
EMail: mbj@microsoft.com
URI: http://self-issued.info/
Jones Standards Track [Page 69]
