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JSON Web Algorithms (JWA)

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JSON Web Algorithms (JWA)

Abstract

The JSON Web Algorithms (JWA) specification enumerates cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications.

(draft 16)

1. Introduction

The JSON Web Algorithms (JWA) specification enumerates 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. All these specifications utilize JavaScript Object Notation (JSON) [RFC4627] based data structures. This specification also describes the semantics and operations that are specific to these algorithms and algorithm families.

Enumerating the algorithms and identifiers for them in this specification, 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.

(draft 04 : http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-1 )

1.1. Notational Conventions

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

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-1.1 )

2. Terminology

(draft 02)

2.1. Terms Incorporated from the JWS Specification

These terms defined by the JSON Web Signature (JWS) [JWS] specification are incorporated into this specification:

JWS
JSON Web Signature
JSON Web Signature (JWS)
A data structure cryptographically securing a JWS Header and a JWS Payload with a JWS Signature value.
JWS Header
A string representing a JavaScript Object Notation (JSON) [RFC4627] object that describes the digital signature or MAC operation applied to create the JWS Signature value.
JWS Payload
The bytes to be secured – a.k.a., the message. The payload can contain an arbitrary sequence of bytes.
JWS Signature
A byte array containing the cryptographic material that secures the contents of the JWS Header and the JWS Payload.
Base64url Encoding
The URL- and filename-safe Base64 encoding described in RFC 4648 [RFC4648], Section 5, with the (non URL- safe) ‘=’ padding characters omitted, as permitted by Section 3.2. (See Appendix C of [JWS] for notes on implementing base64url encoding without padding.)
Encoded JWS Header
Base64url encoding of the bytes of the UTF-8 [RFC3629] representation of the JWS Header.
Encoded JWS Payload
Base64url encoding of the JWS Payload.
Encoded JWS Signature
Base64url encoding of the JWS Signature.
JWS Secured Input
The concatenation of the Encoded JWS Header, a period (‘.’) character, and the Encoded JWS Payload.
Collision Resistant Namespace

A namespace that allows names to be allocated in a manner such that they are highly unlikely to collide with other names. For instance, collision resistance can be achieved through administrative delegation of portions of the namespace or through use of collision-resistant name allocation functions.

Examples of Collision Resistant Namespaces include: Domain Names, Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670 Recommendation series, and Universally Unique IDentifiers (UUIDs) [RFC4122].

When using an administratively delegated namespace, the definer of a name needs to take reasonable precautions to ensure they are in control of the portion of the namespace they use to define the name.

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-2.1 )

2.2. Terms Incorporated from the JWE Specification

These terms defined by the JSON Web Encryption (JWE) [JWE] specification are incorporated into this specification:

JWE
JSON Web Encryption
JSON Web Encryption (JWE)
A data structure representing an encrypted version of a Plaintext. The structure consists of four parts: the JWE Header, the JWE Encrypted Key, the JWE Ciphertext, and the JWE Integrity Value.
Plaintext
The bytes to be encrypted – a.k.a., the message. The plaintext can contain an arbitrary sequence of bytes.
Ciphertext
The encrypted version of the Plaintext.
CEK
Content Encryption Key
Content Encryption Key (CEK)
A symmetric key used to encrypt the Plaintext for the recipient to produce the Ciphertext.
CIK
Content Integrity Key
Content Integrity Key (CIK)
A key used with a MAC function to ensure the integrity of the Ciphertext and the parameters used to create it.
CMK
Content Master Key
Content Master Key (CMK)
A key from which the CEK and CIK are derived. When key wrapping or key encryption are employed, the CMK is randomly generated and encrypted to the recipient as the JWE Encrypted Key. When key agreement is employed, the CMK is the result of the key agreement algorithm.
JWE Header
A string representing a JSON object that describes the encryption operations applied to create the JWE Encrypted Key, the JWE Ciphertext, and the JWE Integrity Value.
JWE Encrypted Key
When key wrapping or key encryption are employed, the Content Master Key (CMK) is encrypted with the intended recipient’s key and the resulting encrypted content is recorded as a byte array, which is referred to as the JWE Encrypted Key. Otherwise, when key agreement is employed, the JWE Encrypted Key is the empty byte array.
JWE Ciphertext
A byte array containing the Ciphertext.
JWE Integrity Value
A byte array containing a MAC value that ensures the integrity of the Ciphertext and the parameters used to create it.
Encoded JWE Header
Base64url encoding of the bytes of the UTF-8 [RFC3629] representation of the JWE Header.
Encoded JWE Encrypted Key
Base64url encoding of the JWE Encrypted Key.
Encoded JWE Ciphertext
Base64url encoding of the JWE Ciphertext.
Encoded JWE Integrity Value
Base64url encoding of the JWE Integrity Value.
AEAD Algorithm
An Authenticated Encryption with Associated Data (AEAD) [RFC5116] encryption algorithm is one that provides an integrated content integrity check. AES Galois/Counter Mode (GCM) is one such algorithm.

(draft 04 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-2.2 )

2.3. Terms Incorporated from the JWK Specification

These terms defined by the JSON Web Key (JWK) [JWK] specification are incorporated into this specification:

JWK
JSON Web Key
JSON Web Key (JWK)
A JSON data structure that represents a public key.
JWK Set
JSON Web Key Set (JWK Set)
A JSON object that contains an array of JWKs as a member.

(draft 04 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-2.3 )

2.4. Defined Terms

These terms are defined for use by this specification:

Header Parameter Name
The name of a member of the JSON object representing a JWS Header or JWE Header.
Header Parameter Value
The value of a member of the JSON object representing a JWS Header or JWE Header.

(draft 04 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-2.4 )

3. Cryptographic Algorithms for JWS

JWS uses cryptographic algorithms to digitally sign or create a Message Authentication Codes (MAC) of the contents of the JWS Header and the JWS Payload. The use of the following algorithms for producing JWSs is defined in this section.

(draft 04, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-3 )

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 Parameter Value Digital Signature or MAC Algorithm Implementation Requirements
HS256 HMAC using SHA-256 hash algorithm REQUIRED
HS384 HMAC using SHA-384 hash algorithm OPTIONAL
HS512 HMAC using SHA-512 hash algorithm OPTIONAL
RS256 RSASSA using SHA-256 hash algorithm RECOMMENDED
RS384 RSASSA using SHA-384 hash algorithm OPTIONAL
RS512 RSASSA using SHA-512 hash algorithm OPTIONAL
ES256 ECDSA using P-256 curve and SHA-256 hash algorithm RECOMMENDED+
ES384 ECDSA using P-384 curve and SHA-384 hash algorithm OPTIONAL
ES512 ECDSA using P-521 curve and SHA-512 hash algorithm OPTIONAL
none No digital signature or MAC value included REQUIRED

All the names are short because a core goal of JWS is for the representations to be compact. However, there is no a priori length restriction on “alg” values.

The use of “+” in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.

See Appendix A for a table cross-referencing the digital signature and MAC “alg” (algorithm) values used in this specification with the equivalent identifiers used by other standards and software packages.

(draft 04 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-3.1 )

3.2. MAC with HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512

Hash-based Message Authentication Codes (HMACs) enable one to use a secret plus a cryptographic hash function to generate a Message Authentication Code (MAC). This can be used to demonstrate that the MAC matches the hashed content, in this case the JWS Secured Input, which therefore demonstrates that whoever generated the MAC was in possession of the secret. The means of exchanging the shared key is outside the scope of this specification.

The algorithm for implementing and validating HMACs is provided in RFC 2104 [RFC2104]. This section defines the use of the HMAC SHA- 256, HMAC SHA-384, and HMAC SHA-512 functions [SHS]. The “alg” (algorithm) header parameter values “HS256”, “HS384”, and “HS512” are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded HMAC value using the respective hash function.

A key of the same size as the hash output (for instance, 256 bits for “HS256”) or larger MUST be used with this algorithm.

The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the hash algorithm “H”, using the bytes of the ASCII [USASCII] representation of the JWS Secured Input as the “text” value, and using the shared key. The HMAC output value is the JWS Signature. The JWS signature is base64url encoded to produce the Encoded JWS Signature.

The HMAC SHA-256 MAC for a JWS is validated by computing an HMAC value per RFC 2104, using SHA-256 as the hash algorithm “H”, using the bytes of the ASCII representation of the received JWS Secured input as the “text” value, and using the shared key. This computed HMAC value is then compared to the result of base64url decoding the received Encoded JWS signature. Alternatively, the computed HMAC value can be base64url encoded and compared to the received Encoded JWS Signature, as this comparison produces the same result as comparing the unencoded values. In either case, if the values match, the HMAC has been validated. If the validation fails, the JWS MUST be rejected.

Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is performed identically to the procedure for HMAC SHA-256 - just using the corresponding hash algorithm 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].

(draft 06 http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-3.2 )

3.3. Digital Signature with RSA SHA-256, RSA SHA-384, or RSA SHA-512

This section defines the use of the RSASSA-PKCS1-V1_5 digital signature algorithm as defined in Section 8.2 of RFC 3447 [RFC3447], (commonly known as PKCS #1), using SHA-256, SHA-384, or SHA-512 [SHS] as the hash functions. The “alg” (algorithm) header parameter values “RS256”, “RS384”, and “RS512” are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded RSA digital signature using the respective hash function.

A key of size 2048 bits or larger MUST be used with these algorithms.

The RSA SHA-256 digital signature is generated as follows:

  1. Generate a digital signature of the bytes of the ASCII representation of the JWS Secured Input using RSASSA-PKCS1-V1_5-SIGN and the SHA-256 hash function with the desired private key. The output will be a byte array.
  2. Base64url encode the resulting byte array.

The output is the Encoded JWS Signature for that JWS.

The RSA SHA-256 digital signature for a JWS is validated as follows:

  1. Take the Encoded JWS Signature and base64url decode it into a byte array. If decoding fails, the JWS MUST be rejected.
  2. Submit the bytes of the ASCII representation of the JWS Secured Input and the public key corresponding to the private key used by the signer to the RSASSA-PKCS1-V1_5-VERIFY algorithm using SHA- 256 as the hash function.
  3. If the validation fails, the JWS MUST be rejected.

Signing with the RSA SHA-384 and RSA SHA-512 algorithms is performed identically to the procedure for RSA SHA-256 - just using the corresponding hash algorithm with correspondingly larger result values: 384 bits for RSA SHA-384 and 512 bits for RSA SHA-512.

An example using this algorithm is shown in Appendix A.2 of [JWS].

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-3.3 )

3.4. Digital Signature with ECDSA P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512

The Elliptic Curve Digital Signature Algorithm (ECDSA) [DSS] provides for the use of Elliptic Curve cryptography, which is able to provide equivalent security to RSA cryptography but using shorter key sizes and with greater processing speed. This means that ECDSA digital signatures will be substantially smaller in terms of length than equivalently strong RSA digital signatures.

This specification defines the use of ECDSA with the P-256 curve and the SHA-256 cryptographic hash function, ECDSA with the P-384 curve and the SHA-384 hash function, and ECDSA with the P-521 curve and the SHA-512 hash function. The P-256, P-384, and P-521 curves are defined in [DSS]. The “alg” (algorithm) header parameter values “ES256”, “ES384”, and “ES512” are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded ECDSA P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512 digital signature, respectively.

The ECDSA P-256 SHA-256 digital signature is generated as follows:

  1. Generate a digital signature of the bytes of the ASCII representation of the JWS Secured 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 byte arrays in big endian order, with each array being be 32 bytes long. The array representations MUST not be shortened to omit any leading zero bytes contained in the values.
  3. Concatenate the two byte arrays in the order R and then S. (Note that many ECDSA implementations will directly produce this concatenation as their output.)
  4. Base64url encode the resulting 64 byte array.

The output is the Encoded JWS Signature for the JWS.

The ECDSA P-256 SHA-256 digital signature for a JWS is validated as follows:

  1. Take the Encoded JWS Signature and base64url decode it into a byte array. If decoding fails, the JWS MUST be rejected.
  2. The output of the base64url decoding MUST be a 64 byte array. If decoding does not result in a 64 byte array, the JWS MUST be rejected.
  3. Split the 64 byte array into two 32 byte arrays. The first array will be R and the second S (with both being in big endian byte order).
  4. Submit the bytes of the ASCII representation of the JWS Secured Input R, S and the public key (x, y) to the ECDSA P-256 SHA-256 validator.
  5. If the validation fails, the JWS MUST be rejected.

Note that ECDSA digital signature contains a value referred to as K, which is a random number generated for each digital signature instance. This means that two ECDSA digital signatures using exactly the same input parameters will output different signature values because their K values will be different. A consequence of this is that one cannot validate an ECDSA signature by recomputing the signature and comparing the results.

Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 algorithms is performed identically to the procedure for ECDSA P-256 SHA-256 - just using the corresponding hash algorithm with correspondingly larger result values. For ECDSA P-384 SHA-384, R and S will be 384 bits each, resulting in a 96 byte array. For ECDSA P-521 SHA-512, R and S will be 521 bits each, resulting in a 132 byte array.

Examples using these algorithms are shown in Appendices A.3 and A.4 of [JWS].

(draft 06 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-3.4 )

3.5. Using the Algorithm “none”

JWSs MAY also be created that do not provide integrity protection. Such a JWS is called a “Plaintext JWS”. Plaintext JWSs MUST use the “alg” value “none”, and are formatted identically to other JWSs, but with an empty JWS Signature value.

(draft04 http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-3.5 )

3.6. Additional Digital Signature/MAC Algorithms and Parameters

Additional algorithms MAY be used to protect JWSs with corresponding “alg” (algorithm) header parameter values being defined to refer to them. New “alg” header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 or be a URI that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML DSIG [RFC3275], XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124], and related specifications as “alg” values.

As indicated by the common registry, JWSs and JWEs share a common “alg” value space. The values used by the two specifications MUST be distinct, as the “alg” value MAY be used to determine whether the object is a JWS or JWE.

Likewise, additional reserved header parameter names MAY be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS]. As indicated by the common registry, JWSs and JWEs share a common header parameter space; when a parameter is used by both specifications, its usage must be compatible between the specifications.

(draft 04 http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-04#section-3.6 )

3.7. Additional Digital Signature/MAC Algorithms and Parameters

Additional algorithms MAY be used to protect JWSs with corresponding “alg” (algorithm) header parameter values being defined to refer to them.

New “alg” header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 or be a value that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML DSIG [RFC3275], XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124], and related specifications as “alg” values.

As indicated by the common registry, JWSs and JWEs share a common “alg” value space. The values used by the two specifications MUST be distinct, as the “alg” value can be used to determine whether the object is a JWS or JWE.

Likewise, additional reserved Header Parameter Names can be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS]. As indicated by the common registry, JWSs and JWEs share a common header parameter space; when a parameter is used by both specifications, its usage must be compatible between the specifications.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-3.7 )

4. Cryptographic Algorithms for JWE

JWE uses cryptographic algorithms to encrypt the Content Master Key (CMK) and the Plaintext. This section specifies a set of specific algorithms for these purposes.

4.1. “alg” (Algorithm) Header Parameter Values for JWE

Note

  • キー(CMK)の暗号手順

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 CMK, producing the JWE Encrypted Key, or to use key agreement to agree upon the CMK.

alg Parameter Value Key Management Algorithm Additional Header Parameters Implementation Requirements
RSA1_5 RSAES-PKCS1-V1_ 5[RFC3447] (none) Required
RSA-OAEP RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with the default parameters specified by RFC 3447 in Section A.2.1 (none) Optional
A128KW Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using the default initial value specified in Section 2.2.3.1 and using 128 bit keys (none) Recommended
A192KW AES Key Wrap Algorithm using the default initial value specified in Section 2.2.3.1 and using 192 bit keys (none) Optional
A256KW AES Key Wrap Algorithm using the default initial value specified in Section 2.2.3.1 and using 256 bit keys (none) Recommended
dir Direct use of a shared symmetric key as the Content Encryption Key (CEK) for the content encryption step (rather than using the symmetric key to wrap the CEK) (none) Recommended
ECDH-ES Elliptic Curve Diffie-Hellman Ephemeral Static [RFC6090] key agreement using the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A], with the agreed-upon key being used directly as the Content Encryption Key (CEK) (rather than being used to wrap the CEK), as specified in Section 4.7 “epk”, “apu”, “apv” Recommended+
ECDH-ES+A128KW Elliptic Curve Diffie-Hellman Ephemeral Static key agreement per “ECDH-ES” and Section 4.7, where the agreed-upon key is used to wrap the Content Encryption Key (CEK) with the “A128KW” function (rather than being used directly as the CEK) “epk”, “apu”, “apv” Recommended
ECDH-ES+A192KW Elliptic Curve Diffie-Hellman Ephemeral Static key agreement, where the agreed-upon key is used to wrap the Content Encryption Key (CEK) with the “A192KW” function (rather than being used directly as the CEK) “epk”, “apu”, “apv” Optional
ECDH-ES+A256KW Elliptic Curve Diffie-Hellman Ephemeral Static key agreement, where the agreed-upon key is used to wrap the Content Encryption Key (CEK) with the “A256KW” function (rather than being used directly as the CEK) “epk”, “apu”, “apv” Recommended
A128GCMKW AES in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 bit keys “iv”, “tag” Optional
A192GCMKW AES GCM using 192 bit keys “iv”, “tag” Optional
A256GCMKW AES GCM using 256 bit keys “iv”, “tag” Optional
PBES2-HS256+A128K W PBES2 [RFC2898] with HMAC SHA-256 as the PRF and AES Key Wrap [RFC3394] using 128 bit keys for the encryption scheme “p2s”, “p2c” Optional
PBES2-HS384+A192K W PBES2 with HMAC SHA-256 as the PRF and AES Key Wrap using 192 bit keys for the encryption scheme “p2s”, “p2c” Optional
PBES2-HS512+A256K W PBES2 with HMAC SHA-256 as the PRF and AES Key Wrap using 256 bit keys for the encryption scheme “p2s”, “p2c” Optional

The Additional Header Parameters column indicates

what additional Header Parameters are used by the algorithm, beyond “alg”, which all use. All but “dir” and “ECDH-ES” also produce a JWE Encrypted Key value.

The use of “+” in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.

Note

4.2. “enc” (Encryption Method) Header Parameter Values for JWE

The table below is the set of “enc” (encryption method) header parameter values that are defined by this specification for use with JWE.

These algorithms are used to encrypt the Plaintext, which produces the Ciphertext.

enc Parameter Value Content Encryption Algorithm Additional Header Parameters Implementatio nRequirements
A128CBC-HS2 56

The AES_128_CBC_HMAC_SHA_2 56 authenticated

encryption algorithm, as defined in Section 4.10.3. This algorithm uses a 256 bit key.
(none) Required
A192CBC-HS3 84

The AES_192_CBC_HMAC_SHA_3 84 authenticated

encryption algorithm, as defined in Section 4.10.4. This algorithm uses a 384 bit key.
(none) Optional
A256CBC-HS5 12

The AES_256_CBC_HMAC_SHA_5 12 authenticated

encryption algorithm, as defined in Section 4.10.5. This algorithm uses a 512 bit key.
(none) Required
A128GCM AES in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 bit keys (none) Recommended
A192GCM AES GCM using 192 bit keys (none) Optional
A256GCM AES GCM using 256 bit keys (none) Recommended

The Additional Header Parameters column indicates what additional Header Parameters are used by the algorithm, beyond “enc”, which all use. All also use a JWE Initialization Vector value and produce JWE Ciphertext and JWE Authentication Tag values.

See Appendix B for a table cross-referencing the encryption “alg” (algorithm) and “enc” (encryption method) values used in this specification with the equivalent identifiers used by other standards and software packages.

( draft 16 , https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-16#section-4.2 )

4.3. Key Encryption with RSAES-PKCS1-V1_5

This section defines the specifics of encrypting a JWE CMK with RSAES-PKCS1-V1_5 [RFC3447]. The “alg” header parameter value “RSA1_5” is used in this case.

A key of size 2048 bits or larger MUST be used with this algorithm.

An example using this algorithm is shown in Appendix A.2 of [JWE].

4.4. Key Encryption with RSAES OAEP

This section defines the specifics of encrypting a JWE CMK with RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with the default parameters specified by RFC 3447 in Section A.2.1. The “alg” header parameter value “RSA-OAEP” is used in this case.

A key of size 2048 bits or larger MUST be used with this algorithm.

An example using this algorithm is shown in Appendix A.1 of [JWE].

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.4 )

4.5. Key Encryption with AES Key Wrap

This section defines the specifics of encrypting a JWE CMK with the Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using 128 or 256 bit keys. The “alg” header parameter values “A128KW” or “A256KW” are used in this case.

An example using this algorithm is shown in Appendix A.3 of [JWE].

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.5 )

4.6. Direct Encryption with a Shared Symmetric Key

This section defines the specifics of directly performing symmetric key encryption without performing a key wrapping step. In this case, the shared symmetric key is used directly as the Content Master Key (CMK) value for the “enc” algorithm. An empty byte array is used as the JWE Encrypted Key value. The “alg” header parameter value “dir” is used in this case.

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.6 )

4.7. Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static (ECDH-ES)

This section defines the specifics of key agreement with Elliptic Curve Diffie-Hellman Ephemeral Static [RFC6090], and using 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 Master Key (CMK) for the “enc” algorithm, or (2) as a symmetric key used to wrap the CMK with either the “A128KW” or “A256KW” algorithms. The “alg” header parameter values “ECDH-ES”, “ECDH-ES+A128KW”, and “ECDH-ES+A256KW” are respectively used in this case.

In the direct case, the output of the Concat KDF MUST be a key of the same length as that used by the “enc” algorithm; in this case, the empty byte array is used as the JWE Encrypted Key value. In the key wrap case, the output of the Concat KDF MUST be a key of the length needed for the specified key wrap algorithm, either 128 or 256 bits respectively.

A new “epk” (ephemeral public key) value MUST be generated for each key agreement transaction.

(draft 06 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.7 )

4.7.1. Key Derivation for “ECDH-ES”

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 a byte array.
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”, and “ECDH-ES+A256KW”, this is 128 and 256, respectively.
AlgorithmID
This is set to the concatenation of keydatalen represented as a 32 bit big endian integer and the bytes of the UTF-8 representation of the “alg” header parameter value.
PartyUInfo
If an “apu” (agreement PartyUInfo) header parameter is present, this is set to the result of base64url decoding the “apu” value; otherwise, it is set to the empty byte string.
PartyVInfo
If an “apv” (agreement PartyVInfo) header parameter is present, this is set to the result of base64url decoding the “apv” value; otherwise, it is set to the empty byte string.
SuppPubInfo
This is set to the empty byte string.
SuppPrivInfo
This is set to the empty byte string.

For all three “alg” values, the digest function used is SHA-256.

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.7.1 )

4.7.1.1. “epk” (Ephemeral Public Key) Header Parameter

The “epk” (ephemeral public key) value created by the originator for the use in key agreement algorithms. This key is represented as a JSON Web Key [JWK] bare public key value. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.7.1.1 )

4.7.1.2. “apu” (Agreement PartyUInfo) Header Parameter

The “apu” (agreement PartyUInfo) value for key agreement algorithms using it (such as “ECDH-ES”), represented as a base64url encoded string. When used, the PartyUInfo value contains information about the sender. Use of this Header Parameter is OPTIONAL. This Header Parameter MUST be understood and processed by implementations when these algorithms are used.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.7.1.2 )

4.7.1.3. “apv” (Agreement PartyVInfo) Header Parameter

The “apv” (agreement PartyVInfo) value for key agreement algorithms using it (such as “ECDH-ES”), represented as a base64url encoded string. When used, the PartyVInfo value contains information about the receiver. Use of this Header Parameter is OPTIONAL. This Header Parameter MUST be understood and processed by implementations when these algorithms are used.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.7.1.3 )

Note

Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography ( NIST Special Publication 800-56A )

4.7.2. Key Derivation for ECDH Key Agreement

The key derivation process derives the agreed upon key from the shared secret Z established through the ECDH algorithm, per Section 6.2.2.2 of [NIST.800-56A].

Key derivation is performed using the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A], where the Digest Method is SHA-256. The Concat KDF parameters are set as follows:

Z
This is set to the representation of the shared secret Z as an octet sequence.
keydatalen
This is set to the number of bits in the desired output key. For “ECDH-ES”, this is length of the key used by the “enc” algorithm. For “ECDH-ES+A128KW”, “ECDH-ES+A192KW”, and “ECDH-ES+A256KW”, this is 128, 192, and 256, respectively.
AlgorithmID
In the Direct Key Agreement case, this is set to the octets of the UTF-8 representation of the “enc” header parameter value. In the Key Agreement with Key Wrapping case, this is set to the octets of the UTF-8 representation of the “alg” header parameter value.
PartyUInfo
The PartyUInfo value is of the form Datalen || Data, where Data is a variable-length string of zero or more octets, and Datalen is a fixed-length, big endian 32 bit counter that indicates the length (in octets) of Data, with || being concatenation. If an “apu” (agreement PartyUInfo) header parameter is present, Data is set to the result of base64url decoding the “apu” value and Datalen is set to the number of octets in Data. Otherwise, Datalen is set to 0 and Data is set to the empty octet sequence.
PartyVInfo
The PartyVInfo value is of the form Datalen || Data, where Data is a variable-length string of zero or more octets, and Datalen is a fixed-length, big endian 32 bit counter that indicates the length (in octets) of Data, with || being concatenation. If an “apv” (agreement PartyVInfo) header parameter is present, Data is set to the result of base64url decoding the “apv” value and Datalen is set to the number of octets in Data. Otherwise, Datalen is set to 0 and Data is set to the empty octet sequence.
SuppPubInfo
This is set to the keydatalen represented as a 32 bit big endian integer.
SuppPrivInfo
This is set to the empty octet sequence.

See Appendix D for an example key agreement computation using this method.

Note: The Diffie-Hellman Key Agreement Method [RFC2631] uses a key derivation function similar to the Concat KDF, but with fewer parameters. Rather than having separate PartyUInfo and PartyVInfo parameters, it uses a single PartyAInfo parameter, which is a random string provided by the sender, that contains 512 bits of information, when provided. It has no SuppPrivInfo parameter. Should it be appropriate for the application, key agreement can be performed in a manner akin to RFC 2631 by using the PartyAInfo value as the “apu” (Agreement PartyUInfo) header parameter value, when provided, and by using no “apv” (Agreement PartyVInfo) header parameter.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.7.2 )

4.8. Composite Plaintext Encryption Algorithms “A128CBC+HS256” and “A256CBC+HS512”

This section defines two composite “enc” algorithms that perform plaintext encryption using non-AEAD algorithms and add an integrity check calculation, so that the resulting composite algorithms are AEAD. These composite algorithms derive a Content Encryption Key (CEK) and a Content Integrity Key (CIK) from a Content Master Key, per Section 4.8.1. They perform block encryption with AES CBC, per Section 4.8.2. Finally, they add an integrity check using HMAC SHA-2 algorithms of matching strength, per Section 4.8.3.

A 256 bit Content Master Key (CMK) value is used with the “A128CBC+HS256” algorithm. A 512 bit Content Master Key (CMK) value is used with the “A256CBC+HS512” algorithm.

An example using this algorithm is shown in Appendix A.2 of [JWE].

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.8 )

4.8.1. Key Derivation for “A128CBC+HS256” and “A256CBC+HS512”

The key derivation process derives CEK and CIK values from the CMK. This section defines the specifics of deriving keys for the “enc” algorithms “A128CBC+HS256” and “A256CBC+HS512”.

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 or SHA-512, respectively. The Concat KDF parameters are set as follows:

Z
This is set to the Content Master Key (CMK).
keydatalen
This is set to the number of bits in the desired output key.
AlgorithmID
This is set to the concatenation of keydatalen represented as a 32 bit big endian integer and the bytes of the UTF-8 representation of the “enc” header parameter value.
PartyUInfo
If an “epu” (encryption PartyUInfo) header parameter is present, this is set to the result of base64url decoding the “epu” value; otherwise, it is set to the empty byte string.
PartyVInfo
If an “epv” (encryption PartyVInfo) header parameter is present, this is set to the result of base64url decoding the “epv” value; otherwise, it is set to the empty byte string.
SuppPubInfo
This is set to the bytes of one of the ASCII strings “Encryption” ([69, 110, 99, 114, 121, 112, 116, 105, 111, 110]) or “Integrity” ([73, 110, 116, 101, 103, 114, 105, 116, 121]) respectively, depending upon whether the CEK or CIK is being generated.
SuppPrivInfo
This is set to the empty byte string.

To compute the CEK from the CMK, the ASCII label “Encryption” is used for the SuppPubInfo value. For “A128CBC+HS256”, the keydatalen is 128 and the digest function used is SHA-256. For “A256CBC+HS512”, the keydatalen is 256 and the digest function used is SHA-512.

To compute the CIK from the CMK, the ASCII label “Integrity” is used for the SuppPubInfo value. For “A128CBC+HS256”, the keydatalen is 256 and the digest function used is SHA-256. For “A256CBC+HS512”, the keydatalen is 512 and the digest function used is SHA-512.

Example derivation computations are shown in Appendices A.4 and A.5 of [JWE].

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.8.1)

4.8.1.1. “iv” (Initialization Vector) Header Parameter

The “iv” (initialization vector) header parameter value is the base64url encoded representation of the Initialization Vector value used for the key encryption operation. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

Note

初期化ベクタ

4.8.1.2. “tag” (Authentication Tag) Header Parameter

The “tag” (authentication tag) header parameter value is the base64url encoded representation of the Authentication Tag value resulting from the key encryption operation. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.8.1.2 )

4.8.2. Encryption Calculation for “A128CBC+HS256” and “A256CBC+HS512”

This section defines the specifics of encrypting the JWE Plaintext with Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES] [NIST.800-38A] using 128 or 256 bit keys. The “enc” header parameter values “A128CBC+HS256” or “A256CBC+HS512” are respectively used in this case.

The CEK is used as the encryption key.

Use of an initialization vector of size 128 bits is REQUIRED with these algorithms.

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.8.2 )

4.8.3. Integrity Calculation for “A128CBC+HS256” and “A256CBC+HS512”

This section defines the specifics of computing the JWE Integrity Value for the “enc” algorithms “A128CBC+HS256” and “A256CBC+HS512”. This value is computed as a MAC of the JWE parameters to be secured.

The MAC input value is the bytes of the ASCII representation of the concatenation of the Encoded JWE Header, a period (‘.’) character, the Encoded JWE Encrypted Key, a second period character (‘.’), the Encoded JWE Initialization Vector, a third period (‘.’) character, and the Encoded JWE Ciphertext.

The CIK is used as the MAC key.

For “A128CBC+HS256”, HMAC SHA-256 is used as the MAC algorithm. For “A256CBC+HS512”, HMAC SHA-512 is used as the MAC algorithm.

The resulting MAC value is used as the JWE Integrity Value. The same integrity calculation is performed during decryption. During decryption, the computed integrity value must match the received JWE Integrity Value.

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.8.3 )

4.9. Plaintext Encryption with AES GCM

This section defines the specifics of encrypting the JWE Plaintext with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 or 256 bit keys. The “enc” header parameter values “A128GCM” or “A256GCM” are used in this case.

The CMK is used as the encryption key.

Use of an initialization vector of size 96 bits is REQUIRED with this algorithm.

The “additional authenticated data” parameter is used to secure the header and key values. The “additional authenticated data” value used is the bytes of the ASCII representation of the concatenation of the Encoded JWE Header, a period (‘.’) character, the Encoded JWE Encrypted Key, a second period character (‘.’), and the Encoded JWE Initialization Vector. This same “additional authenticated data” value is used when decrypting as well.

The requested size of the “authentication tag” output MUST be 128 bits, regardless of the key size.

As GCM is an AEAD algorithm, the JWE Integrity Value is set to be the “authentication tag” value produced by the encryption. During decryption, the received JWE Integrity Value is used as the “authentication tag” value.

Examples using this algorithm are shown in Appendices A.1 and A.3 of [JWE].

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-4.9)

4.9.1. Header Parameters Used for PBES2 Key Encryption

The following Header Parameters are used for Key Encryption with PBES2.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.9.1 )

4.9.1.1. “p2s” (PBES2 salt) Parameter

The “p2s” (PBES2 salt) header parameter contains the PBKDF2 salt value (s) as a base64url encoded string. This value MUST NOT be the empty string. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

The salt expands the possible keys that can be derived from a given password. [RFC2898] originally recommended a minimum salt length of 8 octets (since there is no concern here of a derived key being re- used for different purposes). The salt MUST be generated randomly; see [RFC4086] for considerations on generating random values. (https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.9.1.1 )

4.9.1.2. “p2c” (PBES2 count) Parameter

The “p2c” (PBES2 count) header parameter contains the PBKDF2 iteration count (c), as an integer. This value MUST NOT be less than 1, as per [RFC2898]. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

The iteration count adds computational expense, ideally compounded by the possible range of keys introduced by the salt. [RFC2898] originally recommended a minimum iteration count of 1000.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.9.1.2 )

4.10. AES_CBC_HMAC_SHA2 Algorithms

This section defines a family of authenticated encryption algorithms built using a composition of Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES] [NIST.800-38A] operations and HMAC [RFC2104] [SHS] operations.

This algorithm family is called AES_CBC_HMAC_SHA2. It also defines two instances of this family, one using 128 bit CBC keys and HMAC SHA-256 and the other using 256 bit CBC keys and HMAC SHA-512.

Test cases for these algorithms can be found in Appendix C.

These algorithms are based upon Authenticated Encryption with AES-CBC and HMAC-SHA [I-D.mcgrew-aead-aes-cbc-hmac-sha2], performing the same cryptographic computations, but with the Initialization Vector and Authentication Tag values remaining separate, rather than being concatenated with the Ciphertext value in the output representation.

This algorithm family is a generalization of the algorithm family in [I-D.mcgrew-aead-aes-cbc-hmac-sha2], and can be used to implement those algorithms.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-4.10 )

4.10.1. Conventions Used in Defining AES_CBC_HMAC_SHA2

We use the following notational conventions.

CBC-PKCS5-ENC(X, P) denotes the AES CBC encryption of P using PKCS #5 padding using the cipher with the key X.

MAC(Y, M) denotes the application of the Message Authentication Code (MAC) to the message M, using the key Y.

The concatenation of two octet strings A and B is denoted as A || B.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-4.10.1 )

4.10.2. Generic AES_CBC_HMAC_SHA2 Algorithm

This section defines AES_CBC_HMAC_SHA2 in a manner that is independent of the AES CBC key size or hash function to be used.

Section 4.10.2.1 and Section 4.10.2.2 define the generic encryption and decryption algorithms.

Section 4.10.3 and Section 4.10.4 define instances of AES_CBC_HMAC_SHA2 t hat specify those details.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-4.10.2 )

4.10.2.1. AES_CBC_HMAC_SHA2 Encryption

The authenticated encryption algorithm takes as input four octet strings: a secret key K, a plaintext P, associated data A, and an initialization vector IV.

The authenticated ciphertext value E and the authentication tag value T are provided as outputs.

The data in the plaintext are encrypted and authenticated, and the associated data are authenticated, but not encrypted.

The encryption process is as follows, or uses an equivalent set of steps:

  1. The secondary keys MAC_KEY and ENC_KEY are generated from the input key K as follows.

    Each of these two keys is an octet string.

    MAC_KEY consists of the initial MAC_KEY_LEN octets of K, in order.

    ENC_KEY consists of the final ENC_KEY_LEN octets of K, in order.

    Here we denote the number of octets in the MAC_KEY as MAC_KEY_LEN, and the number of octets in ENC_KEY as ENC_KEY_LEN; the values of these parameters are specified by the AEAD algorithms (in Section 4.10.3 and Section 4.10.4).

    The number of octets in the input key K is the sum of MAC_KEY_LEN and ENC_KEY_LEN. When generating the secondary keys from K, MAC_KEY and ENC_KEY MUST NOT overlap.

    Note that the MAC key comes before the encryption key in the input key K; this is in the opposite order of the algorithm names in the identifier “AES_CBC_HMAC_SHA2”.

    Note

    K (Secret Key ) = MAC_KEY + ENC_KEY

    MAC_KEY

    ENC_KEY

    <— MAC_KEY_LEN –> <– ENC_KEY_LEN –>

    IV = 128 bit (16 octet )

  2. The Initialization Vector (IV) used is a 128 bit value generated randomly or pseudorandomly for use in the cipher.

    Note

    IVは固定で128bit(16octet)

  3. The plaintext is CBC encrypted using PKCS #5 padding using ENC_KEY as the key, and the IV. We denote the ciphertext output from this step as E.

    Note

    • プレーンテキストを ENC_KEYとIVを使って PKCS#5 パディングでCBC暗号化。
  4. The octet string AL is equal to the number of bits in A expressed as a 64-bit unsigned integer in network byte order.

    Note

    • AL は 関連データ(A)のビット長。のオクテット数。
  5. A message authentication tag T is computed by applying HMAC [RFC2104] to the following data, in order:

    the associated data A,

    the initialization vector IV,

    the ciphertext E computed in the previous step, and

    the octet string AL defined above.

    The string MAC_KEY is used as the MAC key. We denote the output of the MAC computed in this step as M.

    The first T_LEN bits of M are used as T.

    Note

    • T_LENは実際のアルゴリズムで異なります。
  6. The Ciphertext E and the Authentication Tag T are returned as the outputs of the authenticated encryption.

The encryption process can be illustrated as follows.

Here K, P, A, IV, and E denote the key, plaintext, associated data, initialization vector, and ciphertext, respectively.

MAC_KEY = initial MAC_KEY_LEN bytes of K,

ENC_KEY = final ENC_KEY_LEN bytes of K,

E = CBC-PKCS5-ENC(ENC_KEY, P),

M = MAC(MAC_KEY, A || IV || E || AL),

T = initial T_LEN bytes of M.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-4.10.2.1 )

4.10.2.2. AES_CBC_HMAC_SHA2 Decryption

The authenticated decryption operation has four inputs: K, A, E, and T as defined above.

It has only a single output, either a plaintext value P or a special symbol FAIL that indicates that the inputs are not authentic.

The authenticated decryption algorithm is as follows, or uses an equivalent set of steps:

  1. The secondary keys MAC_KEY and ENC_KEY are generated from the input key K as in Step 1 of Section 4.10.2.1.
  2. The integrity and authenticity of A and E are checked by computing an HMAC with the inputs as in Step 5 of Section 4.10.2.1. The value T, from the previous step, is compared to the first MAC_KEY length bits of the HMAC output. If those values are identical, then A and E are considered valid, and processing is continued. Otherwise, all of the data used in the MAC validation are discarded, and the AEAD decryption operation returns an indication that it failed, and the operation halts. (But see Section 10 of [JWE] for security considerations on thwarting timing attacks.)
  3. The value E is decrypted and the PKCS #5 padding is removed. The value IV is used as the initialization vector. The value ENC_KEY is used as the decryption key.
  4. The plaintext value is returned.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-4.10.2.2 )

4.10.3. AES_128_CBC_HMAC_SHA_256

This algorithm is a concrete instantiation of the generic AES_CBC_HMAC_SHA2 algorithm above.

It uses the HMAC message authentication code [RFC2104] with the SHA-256 hash function [SHS] to provide message authentication, with the HMAC output truncated to 128 bits, corresponding to the HMAC-SHA-256-128 algorithm defined in [RFC4868].

For encryption, it uses AES in the Cipher Block Chaining (CBC) mode of operation as defined in Section 6.2 of [NIST.800-38A], with PKCS #5 padding.

The input key K is 32 octets long.

The AES CBC IV is 16 octets long. ENC_KEY_LEN is 16 octets.

The SHA-256 hash algorithm is used in HMAC. MAC_KEY_LEN is 16 octets.

The HMAC-SHA-256 output is truncated to T_LEN=16 octets, by stripping off the final 16 octets.

K (Secret Key ) = MAC_KEY + ENC_KEY (32 octet )

+----------------------+----------------------+
| MAC_KEY              | ENC_KEY              |
+----------------------+----------------------+

<--- MAC_KEY_LEN(16)--> <-- ENC_KEY_LEN(16) -->

IV = 128 bit (16 octet )

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-13#section-4.10.3 )

4.10.4. AES_192_CBC_HMAC_SHA_384

AES_192_CBC_HMAC_SHA_384 is based on AES_128_CBC_HMAC_SHA_256, but with the following differences:

A 192 bit AES CBC key is used instead of 128.

SHA-384 is used in HMAC instead of SHA-256.

ENC_KEY_LEN is 24 octets instead of 16.

MAC_KEY_LEN is 24 octets instead of 16.

The length of the input key K is 48 octets instead of 32.

The HMAC SHA-384 value is truncated to T_LEN=24 octets instead of 16.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.10.4 )

4.10.5. AES_256_CBC_HMAC_SHA_512

AES_256_CBC_HMAC_SHA_512 is based on AES_128_CBC_HMAC_SHA_256, but with the following differences:

A 256 bit AES CBC key is used instead of 128.

SHA-512 is used in HMAC instead of SHA-256.

ENC_KEY_LEN is 32 octets instead of 16.

MAC_KEY_LEN is 32 octets instead of 16.

The length of the input key K is 64 octets instead of 32.

The HMAC SHA-512 value is truncated to T_LEN=32 octets instead of 16.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.10.5 )

4.10.6. Plaintext Encryption with AES_CBC_HMAC_SHA2

The algorithm value “A128CBC-HS256” is used as the “alg” value when using AES_128_CBC_HMAC_SHA_256 with JWE. The algorithm value “A192CBC-HS384” is used as the “alg” value when using AES_192_CBC_HMAC_SHA_384 with JWE. The algorithm value “A256CBC-HS512” is used as the “alg” value when using AES_256_CBC_HMAC_SHA_512 with JWE. The Additional Authenticated Data value used is the octets of the ASCII representation of the Encoded JWE Header value. The JWE Initialization Vector value used is the IV value.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.10.6 )

4.11. Plaintext Encryption with AES GCM

This section defines the specifics of encrypting the JWE Plaintext with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128, 192, or 256 bit keys. The “enc” header parameter values “A128GCM”, “A192GCM”, or “A256GCM” are respectively used in this case.

The CEK is used as the encryption key.

Use of an initialization vector of size 96 bits is REQUIRED with this algorithm.

The Additional Authenticated Data value used is the octets of the ASCII representation of the Encoded JWE Header value.

The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size.

The JWE Authentication Tag is set to be the Authentication Tag value produced by the encryption. During decryption, the received JWE Authentication Tag is used as the Authentication Tag value.

An example using this algorithm is shown in Appendix A.1 of [JWE].

(https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.11 )

4.12. Additional Encryption Algorithms and Parameters

Additional algorithms MAY be used to protect JWEs with corresponding “alg” (algorithm) and “enc” (encryption method) header parameter values being defined to refer to them. New “alg” and “enc” header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 or be a value that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313], and related specifications as “alg” and “enc” values.

As indicated by the common registry, JWSs and JWEs share a common “alg” value space. The values used by the two specifications MUST be distinct, as the “alg” value can be used to determine whether the object is a JWS or JWE.

Likewise, additional reserved Header Parameter Names can be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS]. As indicated by the common registry, JWSs and JWEs share a common header parameter space; when a parameter is used by both specifications, its usage must be compatible between the specifications.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-4.12 )

5. Cryptographic Algorithms for JWK

A JSON Web Key (JWK) [JWK] is a JavaScript Object Notation (JSON) [RFC4627] data structure that represents a cryptographic key.

A JSON Web Key Set (JWK Set) is a JSON data structure for representing a set of JWKs. This section specifies a set of key types to be used for those keys and the key type specific parameters for representing those keys.

Parameters are defined for public, private, and symmetric keys.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5 )

5.1. “kty” (Key Type) Parameter Values for JWK

The table below is the set of “kty” (key type) parameter values that are defined by this specification for use in JWKs.

kty Parameter Value Key Type Implementation Requirements
EC Elliptic Curve [DSS] key type RECOMMENDED+
RSA RSA [RFC3447] key type REQUIRED
oct Octet sequence key type (used to represent symmetric keys) RECOMMENDED+

All the names are short because a core goal of JWK is for the representations to be compact. However, there is no a priori length restriction on “kty” values.

The use of “+” in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.1 )

5.2. JWK Parameters for Elliptic Curve Keys

JWKs can represent Elliptic Curve [DSS] keys. In this case, the “kty” member value MUST be “EC”. Furthermore, these additional members MUST be present:

5.2.1. “crv” (Curve) Parameter

The “crv” (curve) member identifies the cryptographic curve used with the key. Curve values from [DSS] used by this specification are:

  • “P-256”
  • “P-384”
  • “P-521”

Additional “crv” values MAY be used, provided they are understood by implementations using that Elliptic Curve key. The “crv” value is a case sensitive string.

5.2.1.1. “crv” (Curve) Parameter

The “crv” (curve) member identifies the cryptographic curve used with the key. Curve values from [DSS] used by this specification are:

o “P-256”

o “P-384”

o “P-521”

Additional “crv” values MAY be used, provided they are understood by implementations using that Elliptic Curve key. The “crv” value is a case sensitive string. (https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-5.2.1.1)

5.2.1.2. “x” (X Coordinate) Parameter

The “x” (x coordinate) member contains the x coordinate for the elliptic curve point. It is represented as the base64url encoding of the coordinate’s big endian representation as an octet sequence. The array representation MUST NOT be shortened to omit any leading zero octets contained in the value. For instance, when representing 521 bit integers, the octet sequence to be base64url encoded MUST contain 66 octets, including any leading zero octets.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-5.2.1.2 )

5.2.1.3. “y” (Y Coordinate) Parameter

The “y” (y coordinate) member contains the y coordinate for the elliptic curve point. It is represented as the base64url encoding of the coordinate’s big endian representation as an octet sequence. The array representation MUST NOT be shortened to omit any leading zero octets contained in the value. For instance, when representing 521 bit integers, the octet sequence to be base64url encoded MUST contain 66 octets, including any leading zero octets.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-5.2.1.3 )

5.2.2. “x” (X Coordinate) Parameter

The “x” (x coordinate) member contains the x coordinate for the elliptic curve point. It is represented as the base64url encoding of the coordinate’s big endian representation as a byte array. The array representation MUST not be shortened to omit any leading zero bytes contained in the value. For instance, when representing 521 bit integers, the byte array to be base64url encoded MUST contain 66 bytes, including any leading zero bytes.

5.2.2.1. “d” (ECC Private Key) Parameter

The “d” (ECC private key) member contains the Elliptic Curve private key value. It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence. The array representation MUST NOT be shortened to omit any leading zero octets. For instance, when representing 521 bit integers, the octet sequence to be base64url encoded MUST contain 66 octets, including any leading zero octets.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-5.2.2.1 )

5.2.3. “y” (Y Coordinate) Parameter

The “y” (y coordinate) member contains the y coordinate for the elliptic curve point. It is represented as the base64url encoding of the coordinate’s big endian representation as a byte array. The array representation MUST not be shortened to omit any leading zero bytes contained in the value. For instance, when representing 521 bit integers, the byte array to be base64url encoded MUST contain 66 bytes, including any leading zero bytes.

5.3. JWK Parameters for RSA Keys

JWKs can represent RSA [RFC3447] keys. In this case, the “kty” member value MUST be “RSA”.

Furthermore, these additional members MUST be present:

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3 )

5.3.1. JWK Parameters for RSA Public Keys

These members MUST be present for RSA public keys:

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.1 )

5.3.1.1. “n” (Modulus) Parameter
The “n” (modulus) member contains the modulus value

for the RSA public key.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

The array representation MUST NOT be shortened to omit any leading zero octets. For instance, when representing 2048 bit integers, the octet sequence to be base64url encoded MUST contain 256 octets, including any leading zero octets.

Note

  • mod -> n に変更

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.1.1 )

5.3.1.2. “e” (Exponent) Parameter

The “e” (exponent) member contains the exponent value for the RSA public key.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

The array representation MUST utilize the minimum number of octets to represent the value.

For instance, when representing the value 65537, the octet sequence to be base64url encoded MUST consist of the three octets [1, 0, 1].

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.1.2 )

5.3.2. JWK 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.

All are REQUIRED for RSA private keys except for “oth”, which is sometimes REQUIRED and sometimes MUST NOT be present, as described below.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2 )

5.3.2.1. “d” (Private Exponent) Parameter

The “d” (private exponent) member contains the private exponent value for the RSA private key.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence. The array representation MUST NOT be shortened to omit any leading zero octets. For instance, when representing 2048 bit integers, the octet sequence to be base64url encoded MUST contain 256 octets, including any leading zero octets.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.1 )

5.3.2.2. “p” (First Prime Factor) Parameter

The “p” (first prime factor) member contains the first prime factor, a positive integer. It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.2 )

5.3.2.3. “q” (Second Prime Factor) Parameter

The “q” (second prime factor) member contains the second prime factor, a positive integer.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.3 )

5.3.2.4. “dp” (First Factor CRT Exponent) Parameter

The “dp” (first factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the first factor, a positive integer.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.4 )

5.3.2.5. “dq” (Second Factor CRT Exponent) Parameter

The “dq” (second factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the second factor, a positive integer.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.5 )

5.3.2.6. “qi” (First CRT Coefficient) Parameter

The “dp” (first CRT coefficient) member contains the Chinese Remainder Theorem (CRT) coefficient of the second factor, a positive integer.

It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

(http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.6 )

5.3.2.7. “oth” (Other Primes Info) Parameter

The “oth” (other primes info) member contains an array of information about any third and subsequent primes, should they exist. When only two primes have been used (the normal case), this parameter MUST be omitted. When three or more primes have been used, the number of array elements MUST be the number of primes used minus two. Each array element MUST be an object with the following members:

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.7 )

5.3.2.7.1. “r” (Prime Factor)

The “r” (prime factor) parameter within an “oth” array member represents the value of a subsequent prime factor, a positive integer. It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.7.1 )

5.3.2.7.2. “d” (Factor CRT Exponent)

The “d” (Factor CRT Exponent) parameter within an “oth” array member represents the CRT exponent of the corresponding prime factor, a positive integer. It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.7.2 )

5.3.2.7.3. “t” (Factor CRT Coefficient)

The “t” (factor CRT coefficient) parameter within an “oth” array member represents the CRT coefficient of the corresponding prime factor, a positive integer. It is represented as the base64url encoding of the value’s unsigned big endian representation as an octet sequence.

( http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-11#section-5.3.2.7.3 )

5.4. Additional Key Algorithm Families and Parameters

Public keys using additional algorithm families MAY be represented using JWK data structures with corresponding “alg” (algorithm family) parameter values being defined to refer to them. New “alg” parameter values SHOULD either be registered in the IANA JSON Web Key Algorithm Families registry Section 6.2 or be a URI that contains a Collision Resistant Namespace.

Likewise, parameters for representing keys for additional algorithm families or additional key properties SHOULD either be registered in the IANA JSON Web Key Parameters registry [JWK] or be a URI that contains a Collision Resistant Namespace.

(draft 05 , http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-05#section-5.4 )

The “k” (key value) member contains the value of the symmetric (or other single-valued) key. It is represented as the base64url encoding of the octet sequence containing the key value.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-5.3.3.1 )

5.4. Additional Key Types and Parameters

Keys using additional key types can be represented using JWK data structures with corresponding “kty” (key type) parameter values being defined to refer to them. New “kty” parameter values SHOULD either be registered in the IANA JSON Web Key Types registry Section 6.2 or be a value that contains a Collision Resistant Namespace.

Likewise, parameters for representing keys for additional key types or additional key properties SHOULD either be registered in the IANA JSON Web Key Parameters registry [JWK] or be a value that contains a Collision Resistant Namespace.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-5.4 )

6. IANA Considerations

The following registration procedure is used for all the registries established by this specification.

Values are registered with a Specification Required [RFC5226] after a two-week review period on the [TBD]@ietf.org mailing list, on the advice of one or more Designated Experts. However, to allow for the allocation of values prior to publication, the Designated Expert(s) may approve registration once they are satisfied that such a specification will be published.

Registration requests must be sent to the [TBD]@ietf.org mailing list for review and comment, with an appropriate subject (e.g., “Request for access token type: example”). [[ Note to RFC-EDITOR: The name of the mailing list should be determined in consultation with the IESG and IANA. Suggested name: jose-reg-review. ]]

Within the review period, the Designated Expert(s) will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful.

IANA must only accept registry updates from the Designated Expert(s) and should direct all requests for registration to the review mailing list.

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#section-6 )

6.1. JSON Web Signature and Encryption Algorithms Registry

This specification establishes the IANA JSON Web Signature and Encryption Algorithms registry for values of the JWS and JWE “alg” (algorithm) and “enc” (encryption method) header parameters. The registry records the algorithm name, the algorithm usage locations from the set “alg” and “enc”, implementation requirements, and a reference to the specification that defines it. The same algorithm name MAY be registered multiple times, provided that the sets of usage locations are disjoint. The implementation requirements of an algorithm MAY be changed over time by the Designated Experts(s) 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.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.1 )

6.1.1. Template

Algorithm Name:
The name requested (e.g., “example”). This name is case sensitive. Names that match other registered names in a case insensitive manner SHOULD NOT be accepted.
Algorithm Usage Location(s):
The algorithm usage, which must be one or more of the values “alg” or “enc”.
Implementation Requirements:
The algorithm implementation requirements, which must be one the words REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED. Optionally, the word can be followed by a “+” or “-”. The use of “+” indicates that the requirement strength is likely to be increased in a future version of the specification. The use of “-” indicates that the requirement strength is likely to be decreased in a future version of the specification.
Change Controller:
For Standards Track RFCs, state “IETF”. For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.
Specification Document(s):
Reference to the document(s) that specify the parameter, preferably including URI(s) that can be used to retrieve copies of the document(s). An indication of the relevant sections may also be included but is not required.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.1.1 )

6.1.2. Initial Registry Contents

  • Algorithm Name: “HS256”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: REQUIRED
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “HS384”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “HS512”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “RS256”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “RS384”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “RS512”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “ES256”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED+
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “ES384”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “ES512”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “PS256”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “PS384”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “PS512”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “none”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: REQUIRED
  • Change Controller: IETF
  • Specification Document(s): Section 3.1 of [[ this document ]]
  • Algorithm Name: “RSA1_5”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: REQUIRED
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “RSA-OAEP”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “A128KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “A192KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “A256KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “dir”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “ECDH-ES”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED+
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “ECDH-ES+A128KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “ECDH-ES+A192KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “ECDH-ES+A256KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.1 of [[ this document ]]
  • Algorithm Name: “A128GCMKW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.8 of [[ this document ]]
  • Algorithm Name: “A192GCMKW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.8 of [[ this document ]]
  • Algorithm Name: “A256GCMKW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.8 of [[ this document ]]
  • Algorithm Name: “PBES2-HS256+A128KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.9 of [[ this document ]]
  • Algorithm Name: “PBES2-HS256+A192KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.9 of [[ this document ]]
  • Algorithm Name: “PBES2-HS256+A256KW”
  • Algorithm Usage Location(s): “alg”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.9 of [[ this document ]]
  • Algorithm Name: “A128CBC-HS256”
  • Algorithm Usage Location(s): “enc”
  • Implementation Requirements: REQUIRED
  • Change Controller: IETF
  • Specification Document(s): Section 4.2 of [[ this document ]]
  • Algorithm Name: “A192CBC-HS384”
  • Algorithm Usage Location(s): “enc”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.2 of [[ this document ]]
  • Algorithm Name: “A256CBC-HS512”
  • Algorithm Usage Location(s): “enc”
  • Implementation Requirements: REQUIRED
  • Change Controller: IETF
  • Specification Document(s): Section 4.2 of [[ this document ]]
  • Algorithm Name: “A128GCM”
  • Algorithm Usage Location(s): “enc”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.2 of [[ this document ]]
  • Algorithm Name: “A192GCM”
  • Algorithm Usage Location(s): “enc”
  • Implementation Requirements: OPTIONAL
  • Change Controller: IETF
  • Specification Document(s): Section 4.2 of [[ this document ]]
  • Algorithm Name: “A256GCM”
  • Algorithm Usage Location(s): “enc”
  • Implementation Requirements: RECOMMENDED
  • Change Controller: IETF
  • Specification Document(s): Section 4.2 of [[ this document ]]

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.1.2 )

6.2. 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 and a reference to the specification that defines it. This specification registers the values defined in Section 5.1.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.2 )

6.2.1. Registration Template

“kty” Parameter Value:
The name requested (e.g., “example”). This name is case sensitive. Names that match other registered names in a case insensitive manner SHOULD NOT be accepted.
Change Controller:
For Standards Track RFCs, state “IETF”. For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.
Implementation Requirements:
The algorithm implementation requirements, which must be one the words REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED. Optionally, the word can be followed by a “+” or “-”. The use of “+” indicates that the requirement strength is likely to be increased in a future version of the specification. The use of “-” indicates that the requirement strength is likely to be decreased in a future version of the specification.
Specification Document(s):
Reference to the document(s) that specify the parameter, preferably including URI(s) that can be used to retrieve copies of the document(s). An indication of the relevant sections may also be included but is not required.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.2.1 )

6.2.2. Initial Registry Contents

  • “kty” Parameter Value: “EC”
  • Implementation Requirements: RECOMMENDED+
  • Change Controller: IETF
  • Specification Document(s): Section 5.2 of [[ this document ]]
  • “kty” Parameter Value: “RSA”
  • Implementation Requirements: REQUIRED
  • Change Controller: IETF
  • Specification Document(s): Section 5.3 of [[ this document ]]
  • “kty” Parameter Value: “oct”
  • Implementation Requirements: RECOMMENDED+
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.3 of [[ this document ]]

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.2.2 )

6.3. JSON Web Key Parameters Registration

This specification registers the parameter names defined in Sections 5.2, 5.3, and 5.3.3 in the IANA JSON Web Key Parameters registry [JWK].

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.3 )

6.3.1. Registry Contents

  • Parameter Name: “crv”
  • Parameter Information Class: Public
  • Change Controller: IETF
  • Specification Document(s): Section 5.2.1.1 of [[ this document ]]
  • Parameter Name: “x”
  • Parameter Information Class: Public
  • Change Controller: IETF
  • Specification Document(s): Section 5.2.1.2 of [[ this document ]]
  • Parameter Name: “y”
  • Parameter Information Class: Public
  • Change Controller: IETF
  • Specification Document(s): Section 5.2.1.3 of [[ this document ]]
  • Parameter Name: “d”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.2.2.1 of [[ this document ]]
  • Parameter Name: “n”
  • Parameter Information Class: Public
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.1.1 of [[ this document ]]
  • Parameter Name: “e”
  • Parameter Information Class: Public
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.1.2 of [[ this document ]]
  • Parameter Name: “d”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.1 of [[ this document ]]
  • Parameter Name: “p”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.2 of [[ this document ]]
  • Parameter Name: “q”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.3 of [[ this document ]]
  • Parameter Name: “dp”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.4 of [[ this document ]]
  • Parameter Name: “dq”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.5 of [[ this document ]]
  • Parameter Name: “qi”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.6 of [[ this document ]]
  • Parameter Name: “oth”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.2.7 of [[ this document ]]
  • Parameter Name: “k”
  • Parameter Information Class: Private
  • Change Controller: IETF
  • Specification Document(s): Section 5.3.3.1 of [[ this document ]]

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.3.1 )

6.4. Registration of JWE Header Parameter Names

This specification registers the Header Parameter Names defined in Section 4.7.1, Section 4.8.1, and Section 4.9.1 in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS].

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.4 )

6.4.1. Registry Contents

  • Header Parameter Name: “epk”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.7.1.1 of [[ this document ]]
  • Header Parameter Name: “apu”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.7.1.2 of [[ this document ]]
  • Header Parameter Name: “apv”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.7.1.3 of [[ this document ]]
  • Header Parameter Name: “iv”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.8.1.1 of [[ this document ]]
  • Header Parameter Name: “tag”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.8.1.2 of [[ this document ]]
  • Header Parameter Name: “p2s”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.9.1.1 of [[ this document ]]
  • Header Parameter Name: “p2c”
  • Header Parameter Usage Location(s): JWE
  • Change Controller: IETF
  • Specification Document(s): Section 4.9.1.2 of [[ this document ]]

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-6.4.1 )

7. Security Considerations

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

The security considerations in [AES], [DSS], [JWE], [JWK], [JWS], [NIST.800-38A], [NIST.800-38D], [NIST.800-56A], [RFC2104], [RFC3394], [RFC3447], [RFC5116], [RFC6090], and [SHS] apply to this specification.

Eventually the algorithms and/or key sizes currently described in this specification will no longer be considered sufficiently secure and will be removed. Therefore, implementers and deployments must be prepared for this eventuality.

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.

Algorithms of matching strengths should be used together whenever possible. For instance, when AES Key Wrap is used with a given key size, using the same key size is recommended when AES GCM is also used.

While Section 8 of RFC 3447 [RFC3447] explicitly calls for people not to adopt RSASSA-PKCS-v1_5 for new applications and instead requests that people transition to RSASSA-PSS, this specification does include RSASSA-PKCS-v1_5, for interoperability reasons, because it commonly implemented.

Keys used with RSAES-PKCS1-v1_5 must follow the constraints in Section 7.2 of RFC 3447 [RFC3447]. In particular, keys with a low public key exponent value must not be used.

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 encryption key or with the same direct encryption key more than 2^32 times.

Plaintext JWSs (JWSs that use the “alg” value “none”) provide no integrity protection. Thus, they must only be used in contexts where the payload is secured by means other than a digital signature or MAC value, or need not be secured.

Receiving agents that validate signatures and sending agents that encrypt messages need to be cautious of cryptographic processing usage when validating signatures and encrypting messages using keys larger than those mandated in this specification. An attacker could send certificates with keys that would result in excessive cryptographic processing, for example, keys larger than those mandated in this specification, which could swamp the processing element. Agents that use such keys without first validating the certificate to a trust anchor are advised to have some sort of cryptographic resource management system to prevent such attacks.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-7 )

7.1. Reusing Key Material when Encrypting Keys

It is NOT RECOMMENDED to reuse the same key material ( Key Encryption Key, Content Master Key, Initialization Vector, etc.) to encrypt multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK Set object multiple times.

One suggestion for preventing re-use is to always generate a new set key material for each encryption operation, based on the considerations noted in this document as well as from [RFC4086].

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-7.1 )

7.2. Password Considerations

While convenient for end users, passwords are vulnerable to a number of attacks. To help mitigate some of these limitations, this document applies principles from [RFC2898] to derive cryptographic keys from user-supplied passwords.

However, the strength of the password still has a significant impact. A high-entry password has greater resistance to dictionary attacks. [NIST-800-63-1] contains guidelines for estimating password entropy, which can help applications and users generate stronger passwords.

An ideal password is one that is as large (or larger) than the derived key length but less than the PRF’s block size. Passwords larger than the PRF’s block size are first hashed, which reduces an attacker’s effective search space to the length of the hash algorithm (32 octets for HMAC SHA-256). It is RECOMMENDED that the password be no longer than 64 octets long for “PBES2-HS256+A256KW”.

Still, care needs to be taken in where and how password-based encryption is used. Such algorithms MUST NOT be used where the attacker can make an indefinite number of attempts to circumvent the protection.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-7.2)

8. Internationalization Considerations

Passwords obtained from users are likely to require preparation and normalization to account for differences of octet sequences generated by different input devices, locales, etc. It is RECOMMENDED that applications to perform the steps outlined in [I-D.melnikov-precis-saslprepbis] to prepare a password supplied directly by a user before performing key derivation and encryption.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-8 )

9. References

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-9 )

9.1. Normative References

[AES]
National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES)”, FIPS PUB 197, November 2001.
[DSS]
National Institute of Standards and Technology, “Digital Signature Standard (DSS)”, FIPS PUB 186-3, June 2009.
[I-D.melnikov-precis-saslprepbis]
Saint-Andre, P. and A. Melnikov, “Preparation and Comparison of Internationalized Strings Representing Simple User Names and Passwords”, draft-melnikov-precis-saslprepbis-04 (work in progress), September 2012.
[JWE]
Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE)”, draft-ietf-jose-json-web-encryption (work in progress), July 2013.
[JWK]
Jones, M., “JSON Web Key (JWK)”, draft-ietf-jose-json-web-key (work in progress), July 2013.
[JWS]
Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS)”, draft-ietf-jose-json-web-signature (work in progress), July 2013.
[NIST.800-38A]
National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation”, NIST PUB 800-38A, December 2001.
[NIST.800-38D]
National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC”, NIST PUB 800-38D, December 2001.
[NIST.800-56A]
National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography”, NIST Special Publication 800-56A, Revision 2, May 2013.
[RFC2104]
Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed- Hashing for Message Authentication”, RFC 2104, February 1997.
[RFC2119]
Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, March 1997.
[RFC2898]
Kaliski, B., “PKCS #5: Password-Based Cryptography Specification Version 2.0”, RFC 2898, September 2000.
[RFC3394]
Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm”, RFC 3394, September 2002.
[RFC3629]
Yergeau, F., “UTF-8, a transformation format of ISO 10646”, STD 63, RFC 3629, November 2003.
[RFC4086]
Eastlake, D., Schiller, J., and S. Crocker, “Randomness Requirements for Security”, BCP 106, RFC 4086, June 2005.
[RFC4627]
Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON)”, RFC 4627, July 2006.
[RFC4648]
Josefsson, S., “The Base16, Base32, and Base64 Data Encodings”, RFC 4648, October 2006.
[RFC4868]
Kelly, S. and S. Frankel, “Using HMAC-SHA-256, HMAC-SHA- 384, and HMAC-SHA-512 with IPsec”, RFC 4868, May 2007.
[RFC5116]
McGrew, D., “An Interface and Algorithms for Authenticated Encryption”, RFC 5116, January 2008.
[RFC5226]
Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs”, BCP 26, RFC 5226, May 2008.
[RFC6090]
McGrew, D., Igoe, K., and M. Salter, “Fundamental Elliptic Curve Cryptography Algorithms”, RFC 6090, February 2011.
[SHS]
National Institute of Standards and Technology, “Secure Hash Standard (SHS)”, FIPS PUB 180-3, October 2008.
[USASCII]
American National Standards Institute, “Coded Character Set – 7-bit American Standard Code for Information Interchange”, ANSI X3.4, 1986.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-9.1 )

9.2. Informative References

[CanvasApp]
Facebook, “Canvas Applications”, 2010.
[I-D.mcgrew-aead-aes-cbc-hmac-sha2]
McGrew, D., Foley, J., and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA”, draft-mcgrew-aead-aes-cbc-hmac-sha2-02 (work in progress), July 2013.
[I-D.miller-jose-jwe-protected-jwk]
Miller, M., “Using JavaScript Object Notation (JSON) Web Encryption (JWE) for Protecting JSON Web Key (JWK) Objects”, draft-miller-jose-jwe-protected-jwk-02 (work in progress), June 2013.
[I-D.rescorla-jsms]
Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format”, draft-rescorla-jsms-00 (work in progress), March 2011.
[JCA]
Oracle, “Java Cryptography Architecture”, 2011.
[JSE]
Bradley, J. and N. Sakimura (editor), “JSON Simple Encryption”, September 2010.
[JSS]
Bradley, J. and N. Sakimura (editor), “JSON Simple Sign”, September 2010.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, “Magic Signatures”, January 2011.
[NIST-800-63-1]
National Institute of Standards and Technology (NIST), “Electronic Authentication Guideline”, NIST 800-63-1, December 2011.
[RFC2631]
Rescorla, E., “Diffie-Hellman Key Agreement Method”, RFC 2631, June 1999.
[RFC3275]
Eastlake, D., Reagle, J., and D. Solo, “(Extensible Markup Language) XML-Signature Syntax and Processing”, RFC 3275, March 2002.
[RFC3447]
Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1”, RFC 3447, February 2003.
[RFC4122]
Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace”, RFC 4122, July 2005.
[W3C.CR-xmldsig-core2-20120124]
Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P., Hirsch, F., Cantor, S., and T. Roessler, “XML Signature Syntax and Processing Version 2.0”, World Wide Web Consortium CR CR-xmldsig-core2-20120124, January 2012, <http://www.w3.org/TR/2012/CR-xmldsig-core2-20120124>.
[W3C.CR-xmlenc-core1-20120313]
Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, “XML Encryption Syntax and Processing Version 1.1”, World Wide Web Consortium CR CR-xmlenc-core1-20120313, March 2012, <http://www.w3.org/TR/2012/CR-xmlenc-core1-20120313>.
[W3C.REC-xmlenc-core-20021210]
Eastlake, D. and J. Reagle, “XML Encryption Syntax and Processing”, World Wide Web Consortium Recommendation REC- xmlenc-core-20021210, December 2002, <http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#section-9.2 )

Appendix A. Digital Signature/MAC Algorithm Identifier Cross-Reference

This appendix contains a table cross-referencing the digital signature and MAC “alg” (algorithm) values used in this specification with the equivalent identifiers used by other standards and software packages. See XML DSIG [RFC3275], XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124], and Java Cryptography Architecture [JCA] for more information about the names defined by those documents.

Algor ithm JWS XML DSIG JCA OID

HMAC using SHA-2 56

hash algo

rithm

HS2 56 http://www.w3.org/2001/04/ xmldsig-more#hmac-sha256 HmacSHA2 56 1.2.840.113 549.2.9

HMAC using SHA-3 84

hash algo

rithm

HS3 84 http://www.w3.org/2001/04/ xmldsig-more#hmac-sha384 HmacSHA3 84 1.2.840.113 549.2.10

HMAC using SHA-5 12

hash algo

rithm

HS5 12 http://www.w3.org/2001/04/ xmldsig-more#hmac-sha512 HmacSHA5 12 1.2.840.113 549.2.11

RSASS A

usin

gSHA- 256

has

h alg orith m

RS2 56 http://www.w3.org/2001/04/ xmldsig-more#rsa-sha256 SHA256wi thRSA 1.2.840.113 549.1.1.11

RSASS A

usin

gSHA- 384

has

h alg orith m

RS3 84 http://www.w3.org/2001/04/ xmldsig-more#rsa-sha384 SHA384wi thRSA 1.2.840.113 549.1.1.12

RSASS A

usin

gSHA- 512

has

h alg orith m

RS5 12 http://www.w3.org/2001/04/ xmldsig-more#rsa-sha512 SHA512wi thRSA 1.2.840.113 549.1.1.13

ECDSA using P-256 curve and SHA-2 56

hash algo

rithm

ES2 56 http://www.w3.org/2001/04/ xmldsig-more#ecdsa-sha256 SHA256wi thECDSA 1.2.840.100 45.4.3.2

ECDSA using P-384 curve and SHA-3 84

hash algo

rithm

ES3 84 http://www.w3.org/2001/04/ xmldsig-more#ecdsa-sha384 SHA384wi thECDSA 1.2.840.100 45.4.3.3

ECDSA using P-521 curve and SHA-5 12

hash algo

rithm

ES5 12 http://www.w3.org/2001/04/ xmldsig-more#ecdsa-sha512 SHA512wi thECDSA 1.2.840.100 45.4.3.4

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#appendix-A )

Appendix B. Encryption Algorithm Identifier Cross-Reference

This appendix contains a table cross-referencing the “alg” (algorithm) and “enc” (encryption method) values used in this specification with the equivalent identifiers used by other standards and software packages. See XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313], and Java Cryptography Architecture [JCA] for more information about the names defined by those documents.

For the composite algorithms “A128CBC+HS256” and “A256CBC+HS512”, the corresponding AES CBC algorithm identifiers are listed.

Algorith m JWE XML ENC JCA
RSAES-PK CS1-V1_5 RSA1_5 http://www.w3.org/2001/0 4/xmlenc#rsa-1_5 RSA/ECB/PKCS1Paddi ng

RSAES using Optimal Asymmetr ic

Encrypt
ion
Paddin

g (OAEP)

RSA-OA EP http://www.w3.org/2001/0 4/xmlenc#rsa-oaep-mgf1p RSA/ECB/OAEPWithSH A-1AndMGF1Padding

Elliptic Curve Diffie-H ellman

Ephemer

alStatic

ECDH-E S http://www.w3.org/2009/x mlenc11#ECDH-ES  

Advanced Encrypti on

Standar
d(AES)
Key Wra

pAlgorit hmusing

128 bi

t keys

A128KW http://www.w3.org/2001/0 4/xmlenc#kw-aes128  

AES Key Wrap Algorith musing

256 bit keys
A256KW http://www.w3.org/2001/0 4/xmlenc#kw-aes256  
AES in Cipher Block Chaining (CBC) mode with PKCS #5 padding using 128 bit keys A128CB C+HS25 6 http://www.w3.org/2001/0 4/xmlenc#aes128-cbc AES/CBC/PKCS5Paddi ng
AES in CBC mode with PKCS #5 padding using 256 bit keys A256CB C+HS51 2 http://www.w3.org/2001/0 4/xmlenc#aes256-cbc AES/CBC/PKCS5Paddi ng

AES in Galois/C ounter

Mode (GCM) using 128 bit keys
A128GC M http://www.w3.org/2009/x mlenc11#aes128-gcm AES/GCM/NoPadding
AES GCM using 256 bit keys A256GC M http://www.w3.org/2009/x mlenc11#aes256-gcm AES/GCM/NoPadding

(draft 06, http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-06#appendix-B )

Appendix C. Test Cases for AES_CBC_HMAC_SHA2 Algorithms

The following test cases can be used to validate implementations of the AES_CBC_HMAC_SHA2 algorithms defined in Section 4.10. They are also intended to correspond to test cases that may appear in a future version of [I-D.mcgrew-aead-aes-cbc-hmac-sha2], demonstrating that the cryptographic computations performed are the same.

The variable names are those defined in Section 4.10. All values are hexadecimal.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-C )

C.1. Test Cases for AES_128_CBC_HMAC_SHA_256

AES_128_CBC_HMAC_SHA_256

  K =       00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
            10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f

  MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f

  ENC_KEY = 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f

  P =       41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
            6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
            69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
            74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
            65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
            6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
            20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
            75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65

  IV =      1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04

  A =       54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
            69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
            4b 65 72 63 6b 68 6f 66 66 73

  AL =      00 00 00 00 00 00 01 50

  E =       c8 0e df a3 2d df 39 d5 ef 00 c0 b4 68 83 42 79
            a2 e4 6a 1b 80 49 f7 92 f7 6b fe 54 b9 03 a9 c9
            a9 4a c9 b4 7a d2 65 5c 5f 10 f9 ae f7 14 27 e2
            fc 6f 9b 3f 39 9a 22 14 89 f1 63 62 c7 03 23 36
            09 d4 5a c6 98 64 e3 32 1c f8 29 35 ac 40 96 c8
            6e 13 33 14 c5 40 19 e8 ca 79 80 df a4 b9 cf 1b
            38 4c 48 6f 3a 54 c5 10 78 15 8e e5 d7 9d e5 9f
            bd 34 d8 48 b3 d6 95 50 a6 76 46 34 44 27 ad e5
            4b 88 51 ff b5 98 f7 f8 00 74 b9 47 3c 82 e2 db

  M =       65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4
            e6 e5 45 82 47 65 15 f0 ad 9f 75 a2 b7 1c 73 ef

  T =       65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-C.1 )

C.2. Test Cases for AES_192_CBC_HMAC_SHA_384

K =       00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
          10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
          20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f

MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
          10 11 12 13 14 15 16 17

ENC_KEY = 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27
          28 29 2a 2b 2c 2d 2e 2f

P =       41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
          6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
          69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
          74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
          65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
          6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
          20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
          75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65

IV =      1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04

A =       54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
          69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
          4b 65 72 63 6b 68 6f 66 66 73

AL =      00 00 00 00 00 00 01 50

E =       ea 65 da 6b 59 e6 1e db 41 9b e6 2d 19 71 2a e5
          d3 03 ee b5 00 52 d0 df d6 69 7f 77 22 4c 8e db
          00 0d 27 9b dc 14 c1 07 26 54 bd 30 94 42 30 c6
          57 be d4 ca 0c 9f 4a 84 66 f2 2b 22 6d 17 46 21
          4b f8 cf c2 40 0a dd 9f 51 26 e4 79 66 3f c9 0b
          3b ed 78 7a 2f 0f fc bf 39 04 be 2a 64 1d 5c 21
          05 bf e5 91 ba e2 3b 1d 74 49 e5 32 ee f6 0a 9a
          c8 bb 6c 6b 01 d3 5d 49 78 7b cd 57 ef 48 49 27
          f2 80 ad c9 1a c0 c4 e7 9c 7b 11 ef c6 00 54 e3

M =       84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
          75 16 80 39 cc c7 33 d7 45 94 f8 86 b3 fa af d4
          86 f2 5c 71 31 e3 28 1e 36 c7 a2 d1 30 af de 57

T =       84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
          75 16 80 39 cc c7 33 d7

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-C.2 )

C.3. Test Cases for AES_256_CBC_HMAC_SHA_512

K =       00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
          10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
          20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
          30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f

MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
          10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f

ENC_KEY = 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
          30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f

P =       41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
          6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
          69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
          74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
          65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
          6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
          20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
          75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65

IV =      1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04

A =       54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
          69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
          4b 65 72 63 6b 68 6f 66 66 73

AL =      00 00 00 00 00 00 01 50

E =       4a ff aa ad b7 8c 31 c5 da 4b 1b 59 0d 10 ff bd
          3d d8 d5 d3 02 42 35 26 91 2d a0 37 ec bc c7 bd
          82 2c 30 1d d6 7c 37 3b cc b5 84 ad 3e 92 79 c2
          e6 d1 2a 13 74 b7 7f 07 75 53 df 82 94 10 44 6b
          36 eb d9 70 66 29 6a e6 42 7e a7 5c 2e 08 46 a1
          1a 09 cc f5 37 0d c8 0b fe cb ad 28 c7 3f 09 b3
          a3 b7 5e 66 2a 25 94 41 0a e4 96 b2 e2 e6 60 9e
          31 e6 e0 2c c8 37 f0 53 d2 1f 37 ff 4f 51 95 0b
          be 26 38 d0 9d d7 a4 93 09 30 80 6d 07 03 b1 f6

M =       4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
          2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5
          fd 30 a5 65 c6 16 ff b2 f3 64 ba ec e6 8f c4 07
          53 bc fc 02 5d de 36 93 75 4a a1 f5 c3 37 3b 9c

T =       4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
          2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-C.3 )

Appendix D. Example ECDH-ES Key Agreement Computation

This example uses ECDH-ES Key Agreement and the Concat KDF to derive the Content Encryption Key (CEK) in the manner described in Section 4.7. In this example, the ECDH-ES Direct Key Agreement mode (“alg” value “ECDH-ES”) is used to produce an agreed upon key for AES GCM with 128 bit keys (“enc” value “A128GCM”).

In this example, a sender Alice is encrypting content to a recipient Bob. The sender (Alice) generates an ephemeral key for the key agreement computation. Alice’s ephemeral key (in JWK format) used for the key agreement computation in this example (including the private part) is:

{"kty":"EC",
 "crv":"P-256",
 "x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
 "y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps",
 "d":"0_NxaRPUMQoAJt50Gz8YiTr8gRTwyEaCumd-MToTmIo"
}

The recipient’s (Bob’s) key (in JWK format) used for the key agreement computation in this example (including the private part) is:

{"kty":"EC",
 "crv":"P-256",
 "x":"weNJy2HscCSM6AEDTDg04biOvhFhyyWvOHQfeF_PxMQ",
 "y":"e8lnCO-AlStT-NJVX-crhB7QRYhiix03illJOVAOyck",
 "d":"VEmDZpDXXK8p8N0Cndsxs924q6nS1RXFASRl6BfUqdw"
}

Header parameter values used in this example are as follows. In this example, the “apu” (agreement PartyUInfo) parameter value is the base64url encoding of the UTF-8 string “Alice” and the “apv” (agreement PartyVInfo) parameter value is the base64url encoding of the UTF-8 string “Bob”. The “epk” parameter is used to communicate the sender’s (Alice’s) ephemeral public key value to the recipient (Bob).

{"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.)
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 UTF-8 string
“A128GCM” - [65, 49, 50, 56, 71, 67, 77].
PartyUInfo This is set to the octets representing the 32 bit big
endian value 5 - [0, 0, 0, 5] - the number of octets in the PartyUInfo content “Alice”, followed, by the octets representing the UTF-8 string “Alice” - [65, 108, 105, 99, 101].
PartyVInfo This is set to the octets representing the 32 bit big
endian value 3 - [0, 0, 0, 3] - the number of octets in the PartyUInfo content “Bob”, followed, by the octets representing the UTF-8 string “Bob” - [66, 111, 98].
SuppPubInfo This is set to the octets representing the 32 bit big
endian value 128 - [0, 0, 0, 128] - the keydatalen value.

SuppPrivInfo This is set to the empty octet sequence.

The resulting derived key, represented as a base64url encoded value is:

jSNmj9QK9ZGQJ2xg5_TJpA

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-D )

Appendix E. Acknowledgements

Solutions for signing and encrypting JSON content were previously explored by Magic Signatures [MagicSignatures], JSON Simple Sign [JSS], Canvas Applications [CanvasApp], JSON Simple Encryption [JSE], and JavaScript Message Security Format [I-D.rescorla-jsms], all of which influenced this draft.

The Authenticated Encryption with AES-CBC and HMAC-SHA [I-D.mcgrew-aead-aes-cbc-hmac-sha2] specification, upon which the AES_CBC_HMAC_SHA2 algorithms are based, was written by David A. McGrew and Kenny Paterson. The test cases for AES_CBC_HMAC_SHA2 are based upon those for [I-D.mcgrew-aead-aes-cbc-hmac-sha2] by John Foley.

Matt Miller wrote Using JavaScript Object Notation (JSON) Web Encryption (JWE) for Protecting JSON Web Key (JWK) Objects [I-D.miller-jose-jwe-protected-jwk], which the password-based encryption content of this draft is based upon.

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

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

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

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-E )

Appendix F. Document History

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

-14

o Removed “PBKDF2” key type and added “p2s” and “p2c” header
parameters for use with the PBES2 algorithms.
o Made the RSA private key parameters that are there to enable
optimizations be RECOMMENDED rather than REQUIRED.
o Added algorithm identifiers for AES algorithms using 192 bit keys
and for RSASSA-PSS using HMAC SHA-384.
o Added security considerations about key lifetimes, addressing
issue #18.

o Added an example ECDH-ES key agreement computation.

-13

o Added key encryption with AES GCM as specified in
draft-jones-jose-aes-gcm-key-wrap-01, addressing issue #13.
o Added security considerations text limiting the number of times
that an AES GCM key can be used for key encryption or direct encryption, per Section 8.3 of NIST SP 800-38D, addressing issue #28.
o Added password-based key encryption as specified in
draft-miller-jose-jwe-protected-jwk-02.

-12

o In the Direct Key Agreement case, the Concat KDF AlgorithmID is
set to the octets of the UTF-8 representation of the “enc” header parameter value.

o Restored the “apv” (agreement PartyVInfo) parameter.

o Moved the “epk”, “apu”, and “apv” Header Parameter definitions to
be with the algorithm descriptions that use them.
o Changed terminology from “block encryption” to “content
encryption”.

-11

o Removed the Encrypted Key value from the AAD computation since it
is already effectively integrity protected by the encryption process. The AAD value now only contains the representation of the JWE Encrypted Header.

o Removed “apv” (agreement PartyVInfo) since it is no longer used.

o Added more information about the use of PartyUInfo during key
agreement.
o Use the keydatalen as the SuppPubInfo value for the Concat KDF
when doing key agreement, as RFC 2631 does.
o Added algorithm identifiers for RSASSA-PSS with SHA-256 and SHA-
o Added a Parameter Information Class value to the JSON Web Key
Parameters registry, which registers whether the parameter conveys public or private information.

-10

o Changed the JWE processing rules for multiple recipients so that a
single AAD value contains the header parameters and encrypted key values for all the recipients, enabling AES GCM to be safely used for multiple recipients.

-09

o Expanded the scope of the JWK parameters to include private and
symmetric key representations, as specified by draft-jones-jose-json-private-and-symmetric-key-00.

o Changed term “JWS Secured Input” to “JWS Signing Input”.

o Changed from using the term “byte” to “octet” when referring to 8
bit values.
o Specified that AES Key Wrap uses the default initial value
specified in Section 2.2.3.1 of RFC 3394. This addressed issue #19.
o Added Key Management Mode definitions to terminology section and
used the defined terms to provide clearer key management instructions. This addressed issue #5.
o Replaced “A128CBC+HS256” and “A256CBC+HS512” with “A128CBC-HS256”
and “A256CBC-HS512”. The new algorithms perform the same cryptographic computations as [I-D.mcgrew-aead-aes-cbc-hmac-sha2], but with the Initialization Vector and Authentication Tag values remaining separate from the Ciphertext value in the output representation. Also deleted the header parameters “epu” (encryption PartyUInfo) and “epv” (encryption PartyVInfo), since they are no longer used.
o Changed from using the term “Integrity Value” to “Authentication
Tag”.

-08

o Changed the name of the JWK key type parameter from “alg” to
“kty”.
o Replaced uses of the term “AEAD” with “Authenticated Encryption”,
since the term AEAD in the RFC 5116 sense implied the use of a particular data representation, rather than just referring to the class of algorithms that perform authenticated encryption with associated data.
o Applied editorial improvements suggested by Jeff Hodges. Many of
these simplified the terminology used.

o Added seriesInfo information to Internet Draft references.

-07

o Added a data length prefix to PartyUInfo and PartyVInfo values.

o Changed the name of the JWK RSA modulus parameter from “mod” to
“n” and the name of the JWK RSA exponent parameter from “xpo” to “e”, so that the identifiers are the same as those used in RFC 3447.
o Made several local editorial changes to clean up loose ends left
over from to the decision to only support block encryption methods providing integrity.

-06

o Removed the “int” and “kdf” parameters and defined the new
composite Authenticated Encryption algorithms “A128CBC+HS256” and “A256CBC+HS512” to replace the former uses of AES CBC, which required the use of separate integrity and key derivation functions.
o Included additional values in the Concat KDF calculation – the
desired output size and the algorithm value, and optionally PartyUInfo and PartyVInfo values. Added the optional header parameters “apu” (agreement PartyUInfo), “apv” (agreement PartyVInfo), “epu” (encryption PartyUInfo), and “epv” (encryption PartyVInfo).
o Changed the name of the JWK RSA exponent parameter from “exp” to
“xpo” so as to allow the potential use of the name “exp” for a future extension that might define an expiration parameter for keys. (The “exp” name is already used for this purpose in the JWT specification.)
o Applied changes made by the RFC Editor to RFC 6749’s registry
language to this specification.

-05

o Support both direct encryption using a shared or agreed upon
symmetric key, and the use of a shared or agreed upon symmetric key to key wrap the CMK. Specifically, added the “alg” values “dir”, “ECDH-ES+A128KW”, and “ECDH-ES+A256KW” to finish filling in this set of capabilities.

o Updated open issues.

-04

o Added text requiring that any leading zero bytes be retained in
base64url encoded key value representations for fixed-length values.
o Added this language to Registration Templates: “This name is case
sensitive. Names that match other registered names in a case insensitive manner SHOULD NOT be accepted.”

o Described additional open issues.

o Applied editorial suggestions.

-03

o Always use a 128 bit “authentication tag” size for AES GCM,
regardless of the key size.
o Specified that use of a 128 bit IV is REQUIRED with AES CBC. It
was previously RECOMMENDED.
o Removed key size language for ECDSA algorithms, since the key size
is implied by the algorithm being used.
o Stated that the “int” key size must be the same as the hash output
size (and not larger, as was previously allowed) so that its size is defined for key generation purposes.
o Added the “kdf” (key derivation function) header parameter to
provide crypto agility for key derivation. The default KDF remains the Concat KDF with the SHA-256 digest function.

o Clarified that the “mod” and “exp” values are unsigned.

o Added Implementation Requirements columns to algorithm tables and
Implementation Requirements entries to algorithm registries.

o Changed AES Key Wrap to RECOMMENDED.

o Moved registries JSON Web Signature and Encryption Header
Parameters and JSON Web Signature and Encryption Type Values to the JWS specification.

o Moved JSON Web Key Parameters registry to the JWK specification.

o Changed registration requirements from RFC Required to
Specification Required with Expert Review.

o Added Registration Template sections for defined registries.

o Added Registry Contents sections to populate registry values.

o No longer say “the UTF-8 representation of the JWS Secured Input
(which is the same as the ASCII representation)”. Just call it “the ASCII representation of the JWS Secured Input”.

o Added “Collision Resistant Namespace” to the terminology section.

o Numerous editorial improvements.

-02

o For AES GCM, use the “additional authenticated data” parameter to
provide integrity for the header, encrypted key, and ciphertext and use the resulting “authentication tag” value as the JWE Authentication Tag.
o Defined minimum required key sizes for algorithms without
specified key sizes.

o Defined KDF output key sizes.

o Specified the use of PKCS #5 padding with AES CBC.

o Generalized text to allow key agreement to be employed as an
alternative to key wrapping or key encryption.

o Clarified that ECDH-ES is a key agreement algorithm.

o Required implementation of AES-128-KW and AES-256-KW.

o Removed the use of “A128GCM” and “A256GCM” for key wrapping.

o Removed “A512KW” since it turns out that it’s not a standard
algorithm.
o Clarified the relationship between “typ” header parameter values
and MIME types.
o Generalized language to refer to Message Authentication Codes
(MACs) rather than Hash-based Message Authentication Codes (HMACs) unless in a context specific to HMAC algorithms.
o Established registries: JSON Web Signature and Encryption Header
Parameters, JSON Web Signature and Encryption Algorithms, JSON Web Signature and Encryption “typ” Values, JSON Web Key Parameters, and JSON Web Key Algorithm Families.

o Moved algorithm-specific definitions from JWK to JWA.

o Reformatted to give each member definition its own section
heading.

-01

o Moved definition of “alg”:”none” for JWSs here from the JWT
specification since this functionality is likely to be useful in more contexts that just for JWTs.
o Added Advanced Encryption Standard (AES) Key Wrap Algorithm using
512 bit keys (“A512KW”).
o Added text “Alternatively, the Encoded JWS Signature MAY be
base64url decoded to produce the JWS Signature and this value can be compared with the computed HMAC value, as this comparison produces the same result as comparing the encoded values”.

o Corrected the Magic Signatures reference.

o Made other editorial improvements suggested by JOSE working group
participants.

-00

o Created the initial IETF draft based upon
draft-jones-json-web-signature-04 and draft-jones-json-web-encryption-02 with no normative changes.
o Changed terminology to no longer call both digital signatures and
HMACs “signatures”.

( https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-14#appendix-F )

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