| JOSE Working Group | M. Jones |
| Internet-Draft | Microsoft |
| Intended status: Standards Track | December 30, 2014 |
| Expires: July 3, 2015 |
JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-39
The JSON Web Algorithms (JWA) specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications. It defines several IANA registries for these identifiers.
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The JSON Web Algorithms (JWA) specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS) [JWS], JSON Web Encryption (JWE) [JWE], and JSON Web Key (JWK) [JWK] specifications. It defines several IANA registries for these identifiers. All these specifications utilize JavaScript Object Notation (JSON) [RFC7159] based data structures. This specification also describes the semantics and operations that are specific to these algorithms and key types.
Registering the algorithms and identifiers here, rather than in the JWS, JWE, and JWK specifications, is intended to allow them to remain unchanged in the face of changes in the set of Required, Recommended, Optional, and Deprecated algorithms over time. This also allows changes to the JWS, JWE, and JWK specifications without changing this document.
Names defined by this specification are short because a core goal is for the resulting representations to be compact.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in Key words for use in RFCs to Indicate Requirement Levels [RFC2119]. If these words are used without being spelled in uppercase then they are to be interpreted with their normal natural language meanings.
BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per Section 2 of [JWS].
UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation of STRING.
ASCII(STRING) denotes the octets of the ASCII [RFC20] representation of STRING.
The concatenation of two values A and B is denoted as A || B.
These terms defined by the JSON Web Signature (JWS) [JWS] specification are incorporated into this specification: "JSON Web Signature (JWS)", "Base64url Encoding", "Header Parameter", "JOSE Header", "JWS Payload", "JWS Protected Header", "JWS Signature", "JWS Signing Input", and "Unsecured JWS".
These terms defined by the JSON Web Encryption (JWE) [JWE] specification are incorporated into this specification: "JSON Web Encryption (JWE)", "Additional Authenticated Data (AAD)", "Authentication Tag", "Content Encryption Key (CEK)", "Direct Encryption", "Direct Key Agreement", "JWE Authentication Tag", "JWE Ciphertext", "JWE Encrypted Key", "JWE Initialization Vector", "JWE Protected Header", "Key Agreement with Key Wrapping", "Key Encryption", "Key Management Mode", and "Key Wrapping".
These terms defined by the JSON Web Key (JWK) [JWK] specification are incorporated into this specification: "JSON Web Key (JWK)" and "JSON Web Key Set (JWK Set)".
These terms defined by the Internet Security Glossary, Version 2 [RFC4949] are incorporated into this specification: "Ciphertext", "Digital Signature", "Message Authentication Code (MAC)", and "Plaintext".
This term is defined by this specification:
JWS uses cryptographic algorithms to digitally sign or create a Message Authentication Code (MAC) of the contents of the JWS Protected Header and the JWS Payload.
The table below is the set of alg (algorithm) header parameter values defined by this specification for use with JWS, each of which is explained in more detail in the following sections:
| alg Param Value | Digital Signature or MAC Algorithm | Implementation Requirements |
|---|---|---|
| HS256 | HMAC using SHA-256 | Required |
| HS384 | HMAC using SHA-384 | Optional |
| HS512 | HMAC using SHA-512 | Optional |
| RS256 | RSASSA-PKCS-v1_5 using SHA-256 | Recommended |
| RS384 | RSASSA-PKCS-v1_5 using SHA-384 | Optional |
| RS512 | RSASSA-PKCS-v1_5 using SHA-512 | Optional |
| ES256 | ECDSA using P-256 and SHA-256 | Recommended+ |
| ES384 | ECDSA using P-384 and SHA-384 | Optional |
| ES512 | ECDSA using P-521 and SHA-512 | Optional |
| PS256 | RSASSA-PSS using SHA-256 and MGF1 with SHA-256 | Optional |
| PS384 | RSASSA-PSS using SHA-384 and MGF1 with SHA-384 | Optional |
| PS512 | RSASSA-PSS using SHA-512 and MGF1 with SHA-512 | Optional |
| none | No digital signature or MAC performed | Optional |
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.1 for a table cross-referencing the JWS digital signature and MAC alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.
Hash-based Message Authentication Codes (HMACs) enable one to use a secret plus a cryptographic hash function to generate a Message Authentication Code (MAC). This can be used to demonstrate that whoever generated the MAC was in possession of the MAC key. The algorithm for implementing and validating HMACs is provided in RFC 2104 [RFC2104].
A key of the same size as the hash output (for instance, 256 bits for HS256) or larger MUST be used with this algorithm. (This requirement is based on Section 5.3.4 (Security Effect of the HMAC Key) of NIST SP 800-117 [NIST.800-107], which states that the effective security strength is the minimum of the security strength of the key and two times the size of the internal hash value.)
The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the hash algorithm "H", using the JWS Signing Input as the "text" value, and using the shared key. The HMAC output value is the JWS Signature.
The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is an HMAC value computed using the corresponding algorithm:
| alg Param Value | MAC Algorithm |
|---|---|
| HS256 | HMAC using SHA-256 |
| HS384 | HMAC using SHA-384 |
| HS512 | HMAC using SHA-512 |
The HMAC SHA-256 MAC for a JWS is validated by computing an HMAC value per RFC 2104, using SHA-256 as the hash algorithm "H", using the received JWS Signing Input as the "text" value, and using the shared key. This computed HMAC value is then compared to the result of base64url decoding the received encoded JWS Signature value. The comparison of the computed HMAC value to the JWS Signature value MUST be done in a constant-time manner to thwart timing attacks. Alternatively, the computed HMAC value can be base64url encoded and compared to the received encoded JWS Signature value (also in a constant-time manner), as this comparison produces the same result as comparing the unencoded values. In either case, if the values match, the HMAC has been validated.
Securing content and validation with the HMAC SHA-384 and HMAC SHA-512 algorithms is performed identically to the procedure for HMAC SHA-256 -- just using the corresponding hash algorithms with correspondingly larger minimum key sizes and result values: 384 bits each for HMAC SHA-384 and 512 bits each for HMAC SHA-512.
An example using this algorithm is shown in Appendix A.1 of [JWS].
This section defines the use of the RSASSA-PKCS1-V1_5 digital signature algorithm as defined in Section 8.2 of RFC 3447 [RFC3447] (commonly known as PKCS #1), using SHA-2 [SHS] hash functions.
A key of size 2048 bits or larger MUST be used with these algorithms.
The RSASSA-PKCS1-V1_5 SHA-256 digital signature is generated as follows: Generate a digital signature of the JWS Signing Input using RSASSA-PKCS1-V1_5-SIGN and the SHA-256 hash function with the desired private key. This is the JWS Signature value.
The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is a digital signature value computed using the corresponding algorithm:
| alg Param Value | Digital Signature Algorithm |
|---|---|
| RS256 | RSASSA-PKCS-v1_5 using SHA-256 |
| RS384 | RSASSA-PKCS-v1_5 using SHA-384 |
| RS512 | RSASSA-PKCS-v1_5 using SHA-512 |
The RSASSA-PKCS1-V1_5 SHA-256 digital signature for a JWS is validated as follows: Submit the JWS Signing Input, the JWS Signature, and the public key corresponding to the private key used by the signer to the RSASSA-PKCS1-V1_5-VERIFY algorithm using SHA-256 as the hash function.
Signing and validation with the RSASSA-PKCS1-V1_5 SHA-384 and RSASSA-PKCS1-V1_5 SHA-512 algorithms is performed identically to the procedure for RSASSA-PKCS1-V1_5 SHA-256 -- just using the corresponding hash algorithms instead of SHA-256.
An example using this algorithm is shown in Appendix A.2 of [JWS].
The Elliptic Curve Digital Signature Algorithm (ECDSA) [DSS] provides for the use of Elliptic Curve cryptography, which is able to provide equivalent security to RSA cryptography but using shorter key sizes and with greater processing speed for many operations. This means that ECDSA digital signatures will be substantially smaller in terms of length than equivalently strong RSA digital signatures.
This specification defines the use of ECDSA with the P-256 curve and the SHA-256 cryptographic hash function, ECDSA with the P-384 curve and the SHA-384 hash function, and ECDSA with the P-521 curve and the SHA-512 hash function. The P-256, P-384, and P-521 curves are defined in [DSS].
The ECDSA P-256 SHA-256 digital signature is generated as follows:
The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is a digital signature value computed using the corresponding algorithm:
| alg Param Value | Digital Signature Algorithm |
|---|---|
| ES256 | ECDSA using P-256 and SHA-256 |
| ES384 | ECDSA using P-384 and SHA-384 |
| ES512 | ECDSA using P-521 and SHA-512 |
The ECDSA P-256 SHA-256 digital signature for a JWS is validated as follows:
Signing and validation with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 algorithms is performed identically to the procedure for ECDSA P-256 SHA-256 -- just using the corresponding hash algorithms with correspondingly larger result values. For ECDSA P-384 SHA-384, R and S will be 384 bits each, resulting in a 96 octet sequence. For ECDSA P-521 SHA-512, R and S will be 521 bits each, resulting in a 132 octet sequence. (Note that the Integer-to-OctetString Conversion defined in Section 2.3.7 of SEC1 [SEC1] used to represent R and S as octet sequences adds zero-valued high-order padding bits when needed to round the size up to a multiple of 8 bits; thus, each 521-bit integer is represented using 528 bits in 66 octets.)
Examples using these algorithms are shown in Appendices A.3 and A.4 of [JWS].
This section defines the use of the RSASSA-PSS digital signature algorithm as defined in Section 8.1 of RFC 3447 [RFC3447] with the MGF1 mask generation function and SHA-2 hash functions, always using the same hash function for both the RSASSA-PSS hash function and the MGF1 hash function. The size of the salt value is the same size as the hash function output. All other algorithm parameters use the defaults specified in Section A.2.3 of RFC 3447.
A key of size 2048 bits or larger MUST be used with this algorithm.
The RSASSA-PSS SHA-256 digital signature is generated as follows: Generate a digital signature of the JWS Signing Input using RSASSA-PSS-SIGN, the SHA-256 hash function, and the MGF1 mask generation function with SHA-256 with the desired private key. This is the JWS signature value.
The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is a digital signature value computed using the corresponding algorithm:
| alg Param Value | Digital Signature Algorithm |
|---|---|
| PS256 | RSASSA-PSS using SHA-256 and MGF1 with SHA-256 |
| PS384 | RSASSA-PSS using SHA-384 and MGF1 with SHA-384 |
| PS512 | RSASSA-PSS using SHA-512 and MGF1 with SHA-512 |
The RSASSA-PSS SHA-256 digital signature for a JWS is validated as follows: Submit the JWS Signing Input, the JWS Signature, and the public key corresponding to the private key used by the signer to the RSASSA-PSS-VERIFY algorithm using SHA-256 as the hash function and using MGF1 as the mask generation function with SHA-256.
Signing and validation with the RSASSA-PSS SHA-384 and RSASSA-PSS SHA-512 algorithms is performed identically to the procedure for RSASSA-PSS SHA-256 -- just using the alternative hash algorithm in both roles.
JWSs MAY also be created that do not provide integrity protection. Such a JWS is called an Unsecured JWS. An Unsecured JWS uses the alg value none and is formatted identically to other JWSs, but MUST use the empty octet sequence as its JWS Signature value. Recipients MUST verify that the JWS Signature value is the empty octet sequence.
Implementations that support Unsecured JWSs MUST NOT accept such objects as valid unless the application specifies that it is acceptable for a specific object to not be integrity protected. Implementations MUST NOT accept Unsecured JWSs by default. In order to mitigate downgrade attacks, applications MUST NOT signal acceptance of Unsecured JWSs at a global level, and SHOULD signal acceptance on a per-object basis. See Section 8.5 for security considerations associated with using this algorithm.
JWE uses cryptographic algorithms to encrypt or determine the Content Encryption Key (CEK).
The table below is the set of alg (algorithm) Header Parameter values that are defined by this specification for use with JWE. These algorithms are used to encrypt the CEK, producing the JWE Encrypted Key, or to use key agreement to agree upon the CEK.
| alg Param Value | Key Management Algorithm | More Header Params | Implementation Requirements |
|---|---|---|---|
| RSA1_5 | RSAES-PKCS1-V1_5 | (none) | Recommended- |
| RSA-OAEP | RSAES OAEP using default parameters | (none) | Recommended+ |
| RSA-OAEP-256 | RSAES OAEP using SHA-256 and MGF1 with SHA-256 | (none) | Optional |
| A128KW | AES Key Wrap with default initial value using 128 bit key | (none) | Recommended |
| A192KW | AES Key Wrap with default initial value using 192 bit key | (none) | Optional |
| A256KW | AES Key Wrap with default initial value using 256 bit key | (none) | Recommended |
| dir | Direct use of a shared symmetric key as the CEK | (none) | Recommended |
| ECDH-ES | Elliptic Curve Diffie-Hellman Ephemeral Static key agreement using Concat KDF | epk, apu, apv | Recommended+ |
| ECDH-ES+A128KW | ECDH-ES using Concat KDF and CEK wrapped with A128KW | epk, apu, apv | Recommended |
| ECDH-ES+A192KW | ECDH-ES using Concat KDF and CEK wrapped with A192KW | epk, apu, apv | Optional |
| ECDH-ES+A256KW | ECDH-ES using Concat KDF and CEK wrapped with A256KW | epk, apu, apv | Recommended |
| A128GCMKW | Key wrapping with AES GCM using 128 bit key | iv, tag | Optional |
| A192GCMKW | Key wrapping with AES GCM using 192 bit key | iv, tag | Optional |
| A256GCMKW | Key wrapping with AES GCM using 256 bit key | iv, tag | Optional |
| PBES2-HS256+A128KW | PBES2 with HMAC SHA-256 and A128KW wrapping | p2s, p2c | Optional |
| PBES2-HS384+A192KW | PBES2 with HMAC SHA-384 and A192KW wrapping | p2s, p2c | Optional |
| PBES2-HS512+A256KW | PBES2 with HMAC SHA-512 and A256KW wrapping | p2s, p2c | Optional |
The More Header Params column indicates what additional Header Parameters are used by the algorithm, beyond alg, which all use. All but dir and ECDH-ES also produce a JWE Encrypted Key value.
The use of "+" in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.
See Appendix A.2 for a table cross-referencing the JWE alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.
This section defines the specifics of encrypting a JWE CEK with RSAES-PKCS1-V1_5 [RFC3447]. The alg Header Parameter value RSA1_5 is used for this algorithm.
A key of size 2048 bits or larger MUST be used with this algorithm.
An example using this algorithm is shown in Appendix A.2 of [JWE].
This section defines the specifics of encrypting a JWE CEK with RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447]. Two sets of parameters for using OAEP are defined, which use different hash functions. In the first case, the default parameters specified by RFC 3447 in Section A.2.1 are used. (Those default parameters are the SHA-1 hash function and the MGF1 with SHA-1 mask generation function.) In the second case, the SHA-256 hash function and the MGF1 with SHA-256 mask generation function are used.
The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm:
| alg Param Value | Key Management Algorithm |
|---|---|
| RSA-OAEP | RSAES OAEP using default parameters |
| RSA-OAEP-256 | RSAES OAEP using SHA-256 and MGF1 with SHA-256 |
A key of size 2048 bits or larger MUST be used with these algorithms. (This requirement is based on Table 4 (Security-strength time frames) of NIST SP 800-57 [NIST.800-57], which requires 112 bits of security for new uses, and Table 2 (Comparable strengths) of the same, which states that 2048 bit RSA keys provide 112 bits of security.)
An example using RSAES OAEP with the default parameters is shown in Appendix A.1 of [JWE].
This section defines the specifics of encrypting a JWE CEK with the Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using the default initial value specified in Section 2.2.3.1.
The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm and key size:
| alg Param Value | Key Management Algorithm |
|---|---|
| A128KW | AES Key Wrap with default initial value using 128 bit key |
| A192KW | AES Key Wrap with default initial value using 192 bit key |
| A256KW | AES Key Wrap with default initial value using 256 bit key |
An example using this algorithm is shown in Appendix A.3 of [JWE].
This section defines the specifics of directly performing symmetric key encryption without performing a key wrapping step. In this case, the shared symmetric key is used directly as the Content Encryption Key (CEK) value for the enc algorithm. An empty octet sequence is used as the JWE Encrypted Key value. The alg Header Parameter value dir is used in this case.
Refer to the security considerations on key lifetimes in Section 8.2 and AES GCM in Section 8.4 when considering utilizing direct encryption.
This section defines the specifics of key agreement with Elliptic Curve Diffie-Hellman Ephemeral Static [RFC6090], in combination with the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A]. The key agreement result can be used in one of two ways:
A new ephemeral public key value MUST be generated for each key agreement operation.
In Direct Key Agreement mode, the output of the Concat KDF MUST be a key of the same length as that used by the enc algorithm. In this case, the empty octet sequence is used as the JWE Encrypted Key value. The alg Header Parameter value ECDH-ES is used in the Direct Key Agreement mode.
In Key Agreement with Key Wrapping mode, the output of the Concat KDF MUST be a key of the length needed for the specified key wrapping algorithm. In this case, the JWE Encrypted Key is the CEK wrapped with the agreed upon key.
The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the result of the key agreement algorithm as the key encryption key for the corresponding key wrapping algorithm:
| alg Param Value | Key Management Algorithm |
|---|---|
| ECDH-ES+A128KW | ECDH-ES using Concat KDF and CEK wrapped with A128KW |
| ECDH-ES+A192KW | ECDH-ES using Concat KDF and CEK wrapped with A192KW |
| ECDH-ES+A256KW | ECDH-ES using Concat KDF and CEK wrapped with A256KW |
The following Header Parameter names are used for key agreement as defined below.
The epk (ephemeral public key) value created by the originator for the use in key agreement algorithms. This key is represented as a JSON Web Key [JWK] public key value. It MUST contain only public key parameters and SHOULD contain only the minimum JWK parameters necessary to represent the key; other JWK parameters included can be checked for consistency and honored or can be ignored. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
The apu (agreement PartyUInfo) value for key agreement algorithms using it (such as ECDH-ES), represented as a base64url encoded string. When used, the PartyUInfo value contains information about the producer. Use of this Header Parameter is OPTIONAL. This Header Parameter MUST be understood and processed by implementations when these algorithms are used.
The apv (agreement PartyVInfo) value for key agreement algorithms using it (such as ECDH-ES), represented as a base64url encoded string. When used, the PartyVInfo value contains information about the recipient. Use of this Header Parameter is OPTIONAL. This Header Parameter MUST be understood and processed by implementations when these algorithms are used.
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:
Applications need to specify how the apu and apv parameters are used for that application. The apu and apv values MUST be distinct, when used. Applications wishing to conform to [NIST.800-56A] need to provide values that meet the requirements of that document, e.g., by using values that identify the producer and consumer. Alternatively, applications MAY conduct key derivation in a manner similar to The Diffie-Hellman Key Agreement Method [RFC2631]: In that case, the apu field MAY either be omitted or represent a random 512-bit value (analogous to PartyAInfo in Ephemeral-Static mode in RFC 2631) and the apv field SHOULD NOT be present.
See Appendix C for an example key agreement computation using this method.
This section defines the specifics of encrypting a JWE Content Encryption Key (CEK) with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [15, 17].
Use of an Initialization Vector of size 96 bits is REQUIRED with this algorithm. The Initialization Vector is represented in base64url encoded form as the iv (initialization vector) Header Parameter value.
The Additional Authenticated Data value used is the empty octet string.
The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size.
The JWE Encrypted Key value is the Ciphertext output.
The Authentication Tag output is represented in base64url encoded form as the tag (authentication tag) Header Parameter value.
The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm and key size:
| alg Param Value | Key Management Algorithm |
|---|---|
| A128GCMKW | Key wrapping with AES GCM using 128 bit key |
| A192GCMKW | Key wrapping with AES GCM using 192 bit key |
| A256GCMKW | Key wrapping with AES GCM using 256 bit key |
The following Header Parameters are used for AES GCM key encryption.
The iv (initialization vector) Header Parameter value is the base64url encoded representation of the 96 bit Initialization Vector value used for the key encryption operation. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
The tag (authentication tag) Header Parameter value is the base64url encoded representation of the 128 bit Authentication Tag value resulting from the key encryption operation. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
This section defines the specifics of performing password-based encryption of a JWE CEK, by first deriving a key encryption key from a user-supplied password using PBES2 schemes as specified in Section 6.2 of [RFC2898], then by encrypting the JWE CEK using the derived key.
These algorithms use HMAC SHA-2 algorithms as the Pseudo-Random Function (PRF) for the PBKDF2 key derivation and AES Key Wrap [RFC3394] for the encryption scheme. The PBES2 password input is an octet sequence; if the password to be used is represented as a text string rather than an octet sequence, the UTF-8 encoding of the text string MUST be used as the octet sequence. The salt parameter MUST be computed from the p2s (PBES2 salt input) Header Parameter value and the alg (algorithm) Header Parameter value as specified in the p2s definition below. The iteration count parameter MUST be provided as the p2c Header Parameter value. The algorithms respectively use HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 as the PRF and use 128, 192, and 256 bit AES Key Wrap keys. Their derived-key lengths respectively are 16, 24, and 32 octets.
The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the result of the corresponding password-based encryption algorithm as the key encryption key for the corresponding key wrapping algorithm:
| alg Param Value | Key Management Algorithm |
|---|---|
| PBES2-HS256+A128KW | PBES2 with HMAC SHA-256 and A128KW wrapping |
| PBES2-HS384+A192KW | PBES2 with HMAC SHA-384 and A192KW wrapping |
| PBES2-HS512+A256KW | PBES2 with HMAC SHA-512 and A256KW wrapping |
See Appendix C of JSON Web Key (JWK) [JWK] for an example key encryption computation using PBES2-HS256+A128KW.
The following Header Parameters are used for Key Encryption with PBES2.
The p2s (PBES2 salt input) Header Parameter encodes a Salt Input value, which is used as part of the PBKDF2 salt value. The p2s value is BASE64URL(Salt Input). This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
The salt expands the possible keys that can be derived from a given password. A Salt Input value containing 8 or more octets MUST be used. A new Salt Input value MUST be generated randomly for every encryption operation; see RFC 4086 [RFC4086] for considerations on generating random values. The salt value used is (UTF8(Alg) || 0x00 || Salt Input), where Alg is the alg Header Parameter value.
The p2c (PBES2 count) Header Parameter contains the PBKDF2 iteration count, represented as a positive JSON integer. This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.
The iteration count adds computational expense, ideally compounded by the possible range of keys introduced by the salt. A minimum iteration count of 1000 is RECOMMENDED.
JWE uses cryptographic algorithms to encrypt and integrity protect the Plaintext and to also integrity protect additional authenticated data.
The table below is the set of enc (encryption algorithm) Header Parameter values that are defined by this specification for use with JWE.
| enc Param Value | Content Encryption Algorithm | Implementation Requirements |
|---|---|---|
| A128CBC-HS256 | AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 5.2.3 | Required |
| A192CBC-HS384 | AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm, as defined in Section 5.2.4 | Optional |
| A256CBC-HS512 | AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm, as defined in Section 5.2.5 | Required |
| A128GCM | AES GCM using 128 bit key | Recommended |
| A192GCM | AES GCM using 192 bit key | Optional |
| A256GCM | AES GCM using 256 bit key | Recommended |
All also use a JWE Initialization Vector value and produce JWE Ciphertext and JWE Authentication Tag values.
See Appendix A.3 for a table cross-referencing the JWE enc (encryption algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.
This section defines a family of authenticated encryption algorithms built using a composition of Advanced Encryption Standard (AES) [AES] in Cipher Block Chaining (CBC) mode [NIST.800-38A] with PKCS #7 padding [RFC5652], Section 6.3 operations and HMAC [1, 13] operations. This algorithm family is called AES_CBC_HMAC_SHA2. It also defines three instances of this family, the first using 128 bit CBC keys and HMAC SHA-256, the second using 192 bit CBC keys and HMAC SHA-384, and the third using 256 bit CBC keys and HMAC SHA-512. Test cases for these algorithms can be found in Appendix B.
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 option is discussed in Appendix B of that specification. This algorithm family is a generalization of the algorithm family in [I-D.mcgrew-aead-aes-cbc-hmac-sha2], and can be used to implement those algorithms.
We use the following notational conventions.
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 5.2.2.1 and Section 5.2.2.2 define the generic encryption and decryption algorithms. Sections 5.2.3 through 5.2.5 define instances of AES_CBC_HMAC_SHA2 that specify those details.
The authenticated encryption algorithm takes as input four octet strings: a secret key K, a plaintext P, additional authenticated data A, and an initialization vector IV. The authenticated ciphertext value E and the authentication tag value T are provided as outputs. The data in the plaintext are encrypted and authenticated, and the additional authenticated data are authenticated, but not encrypted.
The encryption process is as follows, or uses an equivalent set of steps:
The number of octets in the input key K MUST be the sum of MAC_KEY_LEN and ENC_KEY_LEN. The values of these parameters are specified by the Authenticated Encryption algorithms in Sections
5.2.3 through 5.2.5. Note that the MAC key comes before the encryption key in the input key K; this is in the opposite order of the algorithm names in the identifier "AES_CBC_HMAC_SHA2".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.
The encryption process can be illustrated as follows. Here K, P, A, IV, and E denote the key, plaintext, additional authenticated data, initialization vector, and ciphertext, respectively.
The authenticated decryption operation has five inputs: K, A, IV, E, and T as defined above. It has only a single output, either a plaintext value P or a special symbol FAIL that indicates that the inputs are not authentic. The authenticated decryption algorithm is as follows, or uses an equivalent set of steps:
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 #7 padding and a 128 bit initialization vector (IV) value.
The AES_CBC_HMAC_SHA2 parameters specific to AES_128_CBC_HMAC_SHA_256 are:
AES_192_CBC_HMAC_SHA_384 is based on AES_128_CBC_HMAC_SHA_256, but with the following differences:
AES_256_CBC_HMAC_SHA_512 is based on AES_128_CBC_HMAC_SHA_256, but with the following differences:
This section defines the specifics of performing authenticated encryption with the AES_CBC_HMAC_SHA2 algorithms.
The CEK is used as the secret key K.
The following enc (encryption algorithm) Header Parameter values are used to indicate that the JWE Ciphertext and JWE Authentication Tag values have been computed using the corresponding algorithm:
| enc Param Value | Content Encryption Algorithm |
|---|---|
| A128CBC-HS256 | AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 5.2.3 |
| A192CBC-HS384 | AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm, as defined in Section 5.2.4 |
| A256CBC-HS512 | AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm, as defined in Section 5.2.5 |
This section defines the specifics of performing authenticated encryption with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [15, 17].
The CEK is used as the encryption key.
Use of an initialization vector of size 96 bits is REQUIRED with this algorithm.
The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size.
The following enc (encryption algorithm) Header Parameter values are used to indicate that the JWE Ciphertext and JWE Authentication Tag values have been computed using the corresponding algorithm and key size:
| enc Param Value | Content Encryption Algorithm |
|---|---|
| A128GCM | AES GCM using 128 bit key |
| A192GCM | AES GCM using 192 bit key |
| A256GCM | AES GCM using 256 bit key |
An example using this algorithm is shown in Appendix A.1 of [JWE].
A JSON Web Key (JWK) [JWK] is a JSON data structure that represents a cryptographic key. These keys can be either asymmetric or symmetric. They can hold both public and private information about the key. This section defines the parameters for keys using the algorithms specified by this document.
The table below is the set of kty (key type) parameter values that are defined by this specification for use in JWKs.
| kty Param Value | Key Type | Implementation Requirements |
|---|---|---|
| EC | Elliptic Curve [DSS] | Recommended+ |
| RSA | RSA [RFC3447] | Required |
| oct | Octet sequence (used to represent symmetric keys) | Required |
The use of "+" in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.
JWKs can represent Elliptic Curve [DSS] keys. In this case, the kty member value is EC.
An elliptic curve public key is represented by a pair of coordinates drawn from a finite field, which together define a point on an elliptic curve. The following members MUST be present for all elliptic curve public keys:
The following member MUST also be present for elliptic curve public keys for the three curves defined in the following section:
The crv (curve) member identifies the cryptographic curve used with the key. Curve values from [DSS] used by this specification are:
These values are registered in the IANA JSON Web Key Elliptic Curve registry defined in Section 7.6. Additional crv values can be registered by other specifications. Specifications registering additional curves must define what parameters are used to represent keys for the curves registered. The crv value is a case-sensitive string.
SEC1 [SEC1] point compression is not supported for any of these three curves.
The x (x coordinate) member contains the x coordinate for the elliptic curve point. It is represented as the base64url encoding of the octet string representation of the coordinate, as defined in Section 2.3.5 of SEC1 [SEC1]. The length of this octet string MUST be the full size of a coordinate for the curve specified in the crv parameter. For example, if the value of crv is P-521, the octet string must be 66 octets long.
The y (y coordinate) member contains the y coordinate for the elliptic curve point. It is represented as the base64url encoding of the octet string representation of the coordinate, as defined in Section 2.3.5 of SEC1 [SEC1]. The length of this octet string MUST be the full size of a coordinate for the curve specified in the crv parameter. For example, if the value of crv is P-521, the octet string must be 66 octets long.
In addition to the members used to represent Elliptic Curve public keys, the following member MUST be present to represent Elliptic Curve private keys.
The d (ECC private key) member contains the Elliptic Curve private key value. It is represented as the base64url encoding of the octet string representation of the private key value, as defined in Section 2.3.7 of SEC1 [SEC1]. The length of this octet string MUST be ceiling(log-base-2(n)/8) octets (where n is the order of the curve).
JWKs can represent RSA [RFC3447] keys. In this case, the kty member value is RSA. The semantics of the parameters defined below are the same as those defined in Sections 3.1 and 3.2 of RFC 3447.
The following members MUST be present for RSA public keys.
The n (modulus) member contains the modulus value for the RSA public key. It is represented as a Base64urlUInt encoded value.
Note that implementers have found that some cryptographic libraries prefix an extra zero-valued octet to the modulus representations they return, for instance, returning 257 octets for a 2048 bit key, rather than 256. Implementations using such libraries will need to take care to omit the extra octet from the base64url encoded representation.
The e (exponent) member contains the exponent value for the RSA public key. It is represented as a Base64urlUInt encoded value.
For instance, when representing the value 65537, the octet sequence to be base64url encoded MUST consist of the three octets [1, 0, 1]; the resulting representation for this value is "AQAB".
In addition to the members used to represent RSA public keys, the following members are used to represent RSA private keys. The parameter d is REQUIRED for RSA private keys. The others enable optimizations and SHOULD be included by producers of JWKs representing RSA private keys. If the producer includes any of the other private key parameters, then all of the others MUST be present, with the exception of oth, which MUST only be present when more than two prime factors were used.
The d (private exponent) member contains the private exponent value for the RSA private key. It is represented as a Base64urlUInt encoded value.
The p (first prime factor) member contains the first prime factor. It is represented as a Base64urlUInt encoded value.
The q (second prime factor) member contains the second prime factor. It is represented as a Base64urlUInt encoded value.
The dp (first factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the first factor. It is represented as a Base64urlUInt encoded value.
The dq (second factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the second factor. It is represented as a Base64urlUInt encoded value.
The qi (first CRT coefficient) member contains the Chinese Remainder Theorem (CRT) coefficient of the second factor. It is represented as a Base64urlUInt encoded value.
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. For more information on this case, see the description of the OtherPrimeInfo parameters in Section A.1.2 of RFC 3447 [RFC3447], upon which the following parameters are modelled. If the consumer of a JWK does not support private keys with more than two primes and it encounters a private key that includes the oth parameter, then it MUST NOT use the key. Each array element MUST be an object with the following members:
The r (prime factor) parameter within an oth array member represents the value of a subsequent prime factor. It is represented as a Base64urlUInt encoded value.
The d (Factor CRT Exponent) parameter within an oth array member represents the CRT exponent of the corresponding prime factor. It is represented as a Base64urlUInt encoded value.
The t (factor CRT coefficient) parameter within an oth array member represents the CRT coefficient of the corresponding prime factor. It is represented as a Base64urlUInt encoded value.
When the JWK kty member value is oct (octet sequence), the member k is used to represent a symmetric key (or another key whose value is a single octet sequence). An alg member SHOULD also be present to identify the algorithm intended to be used with the key, unless the application uses another means or convention to determine the algorithm used.
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.
The following registration procedure is used for all the registries established by this specification.
Values are registered on a Specification Required [RFC5226] basis after a three-week review period on the jose-reg-review@ietf.org mailing list, on the advice of one or more Designated Experts. However, to allow for the allocation of values prior to publication, the Designated Expert(s) may approve registration once they are satisfied that such a specification will be published.
Registration requests must be sent to the jose-reg-review@ietf.org mailing list for review and comment, with an appropriate subject (e.g., "Request to register algorithm: example").
Within the review period, the Designated Expert(s) will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Registration requests that are undetermined for a period longer than 21 days can be brought to the IESG's attention (using the iesg@ietf.org mailing list) for resolution.
Criteria that should be applied by the Designated Expert(s) includes determining whether the proposed registration duplicates existing functionality, determining whether it is likely to be of general applicability or whether it is useful only for a single application, and whether the registration description is clear.
IANA must only accept registry updates from the Designated Expert(s) and should direct all requests for registration to the review mailing list.
It is suggested that multiple Designated Experts be appointed who are able to represent the perspectives of different applications using this specification, in order to enable broadly-informed review of registration decisions. In cases where a registration decision could be perceived as creating a conflict of interest for a particular Expert, that Expert should defer to the judgment of the other Expert(s).
[[ Note to the RFC Editor and IANA: Pearl Liang of ICANN had requested that the draft supply the following proposed registry description information. It is to be used for all registries established by this specification.
]]
This specification establishes the IANA JSON Web Signature and Encryption Algorithms registry for values of the JWS and JWE alg (algorithm) and enc (encryption algorithm) Header Parameters. The registry records the algorithm name, the algorithm usage locations, implementation requirements, and a reference to the specification that defines it. The same algorithm name can be registered multiple times, provided that the sets of usage locations are disjoint.
It is suggested that when multiple variations of algorithms are being registered that use keys of different lengths and the key lengths for each need to be fixed (for instance, because they will be created by key derivation functions), that the length of the key be included in the algorithm name. This allows readers of the JSON text to more easily make security decisions.
The Designated Expert(s) should perform reasonable due diligence that algorithms being registered are either currently considered cryptographically credible or are being registered as Deprecated or Prohibited.
The implementation requirements of an algorithm may be changed over time as the cryptographic landscape evolves, for instance, to change the status of an algorithm to Deprecated, or to change the status of an algorithm from Optional to Recommended+ or Required. Changes of implementation requirements are only permitted on a Specification Required basis after review by the Designated Experts(s), with the new specification defining the revised implementation requirements level.
This specification registers the Header Parameter names defined in Section 4.6.1, Section 4.7.1, and Section 4.8.1 in the IANA JSON Web Signature and Encryption Header Parameters registry defined in [JWS].
This specification establishes the IANA JSON Web Encryption Compression Algorithms registry for JWE zip member values. The registry records the compression algorithm value and a reference to the specification that defines it.
This specification establishes the IANA JSON Web Key Types registry for values of the JWK kty (key type) parameter. The registry records the kty value, implementation requirements, and a reference to the specification that defines it.
The implementation requirements of a key type may be changed over time as the cryptographic landscape evolves, for instance, to change the status of a key type to Deprecated, or to change the status of a key type from Optional to Recommended+ or Required. Changes of implementation requirements are only permitted on a Specification Required basis after review by the Designated Experts(s), with the new specification defining the revised implementation requirements level.
This specification registers the values defined in Section 6.1.
This specification registers the parameter names defined in Sections 6.2, 6.3, and 6.4 in the IANA JSON Web Key Parameters registry defined in [JWK].
This specification establishes the IANA JSON Web Key Elliptic Curve registry for JWK crv member values. The registry records the curve name, implementation requirements, and a reference to the specification that defines it. This specification registers the parameter names defined in Section 6.2.1.1.
The implementation requirements of a curve may be changed over time as the cryptographic landscape evolves, for instance, to change the status of a curve to Deprecated, or to change the status of a curve from Optional to Recommended+ or Required. Changes of implementation requirements are only permitted on a Specification Required basis after review by the Designated Experts(s), with the new specification defining the revised implementation requirements level.
All of the security issues that are pertinent to any cryptographic application must be addressed by JWS/JWE/JWK agents. Among these issues are protecting the user's asymmetric private and symmetric secret keys and employing countermeasures to various attacks.
The security considerations in [AES], [DSS], [JWE], [JWK], [JWS], [NIST.800-38D], [NIST.800-56A], [NIST.800-107], [RFC2104], [RFC3394], [RFC3447], [RFC5116], [RFC6090], and [SHS] apply to this specification.
Implementers should be aware that cryptographic algorithms become weaker with time. As new cryptanalysis techniques are developed and computing performance improves, the work factor to break a particular cryptographic algorithm will be reduced. Therefore, implementers and deployments must be prepared for the set of algorithms that are supported and used to change over time. Thus, cryptographic algorithm implementations should be modular, allowing new algorithms to be readily inserted.
Many algorithms have associated security considerations related to key lifetimes and/or the number of times that a key may be used. Those security considerations continue to apply when using those algorithms with JOSE data structures. See NIST SP 800-57 [NIST.800-57] for specific guidance on key lifetimes.
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 is commonly implemented.
Keys used with RSAES-PKCS1-v1_5 must follow the constraints in Section 7.2 of RFC 3447. Also, keys with a low public key exponent value, as described in Section 3 of Twenty years of attacks on the RSA cryptosystem [Boneh99], must not be used.
Keys used with AES GCM must follow the constraints in Section 8.3 of [NIST.800-38D], which states: "The total number of invocations of the authenticated encryption function shall not exceed 2^32, including all IV lengths and all instances of the authenticated encryption function with the given key". In accordance with this rule, AES GCM MUST NOT be used with the same key value more than 2^32 times.
An Initialization Vector value MUST NOT ever be used multiple times with the same AES GCM key. One way to prevent this is to store a counter with the key and increment it with every use. The counter can also be used to prevent exceeding the 2^32 limit above.
This security consideration does not apply to the composite AES-CBC HMAC SHA-2 or AES Key Wrap algorithms.
Unsecured JWSs (JWSs that use the alg value none) provide no integrity protection. Thus, they must only be used in contexts in which the payload is secured by means other than a digital signature or MAC value, or need not be secured.
An example means of preventing accepting Unsecured JWSs by default is for the "verify" method of a hypothetical JWS software library to have a Boolean "acceptUnsecured" parameter that indicates none is an acceptable alg value. As another example, the "verify" method might take a list of algorithms that are acceptable to the application as a parameter and would reject Unsecured JWS values if none is not in that list.
The following example illustrates the reasons for not accepting Unsecured JWSs at a global level. Suppose an application accepts JWSs over two channels, (1) HTTP and (2) HTTPS with client authentication. It requires a JWS signature on objects received over HTTP, but accepts Unsecured JWSs over HTTPS. If the application were to globally indicate that none is acceptable, then an attacker could provide it with an Unsecured JWS over HTTP and still have that object successfully validate. Instead, the application needs to indicate acceptance of none for each object received over HTTPS (e.g., by setting "acceptUnsecured" to "true" for the first hypothetical JWS software library above), but not for each object received over HTTP.
Receiving agents that validate signatures and sending agents that encrypt messages need to be cautious of cryptographic processing usage when validating signatures and encrypting messages using keys larger than those mandated in this specification. An attacker could supply content using keys that would result in excessive cryptographic processing, for example, keys larger than those mandated in this specification. Implementations should set and enforce upper limits on the key sizes they accept. Section 5.6.1 (Comparable Algorithm Strengths) of NIST SP 800-57 [NIST.800-57] contains statements on largest approved key sizes that may be applicable.
It is NOT RECOMMENDED to reuse the same entire set of key material (Key Encryption Key, Content Encryption Key, Initialization Vector, etc.) to encrypt multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK Set object multiple times. One suggestion for preventing re-use is to always generate at least one new piece of key material for each encryption operation (e.g., a new Content Encryption Key, a new Initialization Vector, and/or a new PBES2 Salt), based on the considerations noted in this document as well as from RFC 4086 [RFC4086].
Passwords are vulnerable to a number of attacks. To help mitigate some of these limitations, this document applies principles from RFC 2898 [RFC2898] to derive cryptographic keys from user-supplied passwords.
However, the strength of the password still has a significant impact. A high-entropy password has greater resistance to dictionary attacks. [NIST.800-63-1] contains guidelines for estimating password entropy, which can help applications and users generate stronger passwords.
An ideal password is one that is as large as (or larger than) the derived key length. However, passwords larger than a certain algorithm-specific size are first hashed, which reduces an attacker's effective search space to the length of the hash algorithm. It is RECOMMENDED that a password used for PBES2-HS256+A128KW be no shorter than 16 octets and no longer than 128 octets and a password used for PBES2-HS512+A256KW be no shorter than 32 octets and no longer than 128 octets long.
Still, care needs to be taken in where and how password-based encryption is used. These algorithms can still be susceptible to dictionary-based attacks if the iteration count is too small; this is of particular concern if these algorithms are used to protect data that an attacker can have indefinite number of attempts to circumvent the protection, such as protected data stored on a file system.
See Section 10.1 of [JWS] for security considerations on key entropy and random values.
See Section 10.5 of [JWS] for security considerations on differences between digital signatures and MACs.
See Section 11.3 of [JWE] for security considerations on using matching algorithm strengths.
See Section 11.4 of [JWE] for security considerations on adaptive chosen-ciphertext attacks.
See Section 10.9 of [JWS] and Section 11.5 of [JWE] for security considerations on timing attacks.
See Section 9.3 of [JWK] for security considerations on RSA private key representations and blinding.
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.ietf-precis-saslprepbis] to prepare a password supplied directly by a user before performing key derivation and encryption.
This appendix contains tables cross-referencing the cryptographic algorithm identifier values defined in this specification with the equivalent identifiers used by other standards and software packages. See XML DSIG [RFC3275], XML DSIG 2.0 [W3C.NOTE-xmldsig-core2-20130411], XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411], and Java Cryptography Architecture [JCA] for more information about the names defined by those documents.
This section contains a table cross-referencing the JWS digital signature and MAC alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.
| JWS | XML DSIG | JCA | OID |
|---|---|---|---|
| HS256 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 | HmacSHA256 | 1.2.840.113549.2.9 |
| HS384 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha384 | HmacSHA384 | 1.2.840.113549.2.10 |
| HS512 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha512 | HmacSHA512 | 1.2.840.113549.2.11 |
| RS256 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha256 | SHA256withRSA | 1.2.840.113549.1.1.11 |
| RS384 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha384 | SHA384withRSA | 1.2.840.113549.1.1.12 |
| RS512 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha512 | SHA512withRSA | 1.2.840.113549.1.1.13 |
| ES256 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256 | SHA256withECDSA | 1.2.840.10045.4.3.2 |
| ES384 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384 | SHA384withECDSA | 1.2.840.10045.4.3.3 |
| ES512 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512 | SHA512withECDSA | 1.2.840.10045.4.3.4 |
| PS256 | http://www.w3.org/2007/05/xmldsig-more#sha256-rsa-MGF1 | SHA256withRSAandMGF1 | 1.2.840.113549.1.1.10 |
| PS384 | http://www.w3.org/2007/05/xmldsig-more#sha384-rsa-MGF1 | SHA384withRSAandMGF1 | 1.2.840.113549.1.1.10 |
| PS512 | http://www.w3.org/2007/05/xmldsig-more#sha512-rsa-MGF1 | SHA512withRSAandMGF1 | 1.2.840.113549.1.1.10 |
This section contains a table cross-referencing the JWE alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.
| JWE | XML ENC | JCA | OID |
|---|---|---|---|
| RSA1_5 | http://www.w3.org/2001/04/xmlenc#rsa-1_5 | RSA/ECB/PKCS1Padding | 1.2.840.113549.1.1.1 |
| RSA-OAEP | http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p | RSA/ECB/OAEPWithSHA-1AndMGF1Padding | 1.2.840.113549.1.1.7 |
| RSA-OAEP-256 | http://www.w3.org/2009/xmlenc11#rsa-oaep & http://www.w3.org/2009/xmlenc11#mgf1sha256 | RSA/ECB/OAEPWithSHA-256AndMGF1Padding & MGF1ParameterSpec.SHA256 | 1.2.840.113549.1.1.7 |
| ECDH-ES | http://www.w3.org/2009/xmlenc11#ECDH-ES | ECDH | 1.3.132.1.12 |
| A128KW | http://www.w3.org/2001/04/xmlenc#kw-aes128 | AESWrap | 2.16.840.1.101.3.4.1.5 |
| A192KW | http://www.w3.org/2001/04/xmlenc#kw-aes192 | AESWrap | 2.16.840.1.101.3.4.1.25 |
| A256KW | http://www.w3.org/2001/04/xmlenc#kw-aes256 | AESWrap | 2.16.840.1.101.3.4.1.45 |
This section contains a table cross-referencing the JWE enc (encryption algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.
For the composite algorithms A128CBC-HS256, A192CBC-HS384, and A256CBC-HS512, the corresponding AES CBC algorithm identifiers are listed.
| JWE | XML ENC | JCA | OID |
|---|---|---|---|
| A128CBC-HS256 | http://www.w3.org/2001/04/xmlenc#aes128-cbc | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.2 |
| A192CBC-HS384 | http://www.w3.org/2001/04/xmlenc#aes192-cbc | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.22 |
| A256CBC-HS512 | http://www.w3.org/2001/04/xmlenc#aes256-cbc | AES/CBC/PKCS5Padding | 2.16.840.1.101.3.4.1.42 |
| A128GCM | http://www.w3.org/2009/xmlenc11#aes128-gcm | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.6 |
| A192GCM | http://www.w3.org/2009/xmlenc11#aes192-gcm | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.26 |
| A256GCM | http://www.w3.org/2009/xmlenc11#aes256-gcm | AES/GCM/NoPadding | 2.16.840.1.101.3.4.1.46 |
The following test cases can be used to validate implementations of the AES_CBC_HMAC_SHA2 algorithms defined in Section 5.2. They are also intended to correspond to test cases that may appear in a future version of [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 5.2. All values are hexadecimal.
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
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
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
This example uses ECDH-ES Key Agreement and the Concat KDF to derive the Content Encryption Key (CEK) in the manner described in Section 4.6. In this example, the ECDH-ES Direct Key Agreement mode (alg value ECDH-ES) is used to produce an agreed upon key for AES GCM with a 128 bit key (enc value A128GCM).
In this example, a producer Alice is encrypting content to a consumer Bob. The producer (Alice) generates an ephemeral key for the key agreement computation. Alice's ephemeral key (in JWK format) used for the key agreement computation in this example (including the private part) is:
{"kty":"EC",
"crv":"P-256",
"x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
"y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps",
"d":"0_NxaRPUMQoAJt50Gz8YiTr8gRTwyEaCumd-MToTmIo"
}
The consumer's (Bob's) key (in JWK format) used for the key agreement computation in this example (including the private part) is:
{"kty":"EC",
"crv":"P-256",
"x":"weNJy2HscCSM6AEDTDg04biOvhFhyyWvOHQfeF_PxMQ",
"y":"e8lnCO-AlStT-NJVX-crhB7QRYhiix03illJOVAOyck",
"d":"VEmDZpDXXK8p8N0Cndsxs924q6nS1RXFASRl6BfUqdw"
}
Header Parameter values used in this example are as follows. 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 producer's (Alice's) ephemeral public key value to the consumer (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:
Concatenating the parameters AlgorithmID through SuppPubInfo results in an OtherInfo value of:
[0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]
Concatenating the round number 1 ([0, 0, 0, 1]), Z, and the OtherInfo value results in the Concat KDF round 1 hash input of:
[0, 0, 0, 1,
158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132, 38, 156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121, 140, 254, 144, 196,
0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]
The resulting derived key, which is the first 128 bits of the round 1 hash output is:
[86, 170, 141, 234, 248, 35, 109, 32, 92, 34, 40, 205, 113, 167, 16, 26]
The base64url encoded representation of this derived key is:
VqqN6vgjbSBcIijNcacQGg
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, Carsten Bormann, John Bradley, Brian Campbell, Alissa Cooper, Breno de Medeiros, Vladimir Dzhuvinov, Roni Even, Stephen Farrell, Yaron Y. Goland, Dick Hardt, Joe Hildebrand, Jeff Hodges, Edmund Jay, Charlie Kaufman, Barry Leiba, James Manger, Matt Miller, Kathleen Moriarty, Tony Nadalin, Axel Nennker, John Panzer, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and Sean Turner, Stephen Farrell, and Kathleen Moriarty served as Security area directors during the creation of this specification.
[[ to be removed by the RFC Editor before publication as an RFC ]]
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