JOSE Working Group | M.B. Jones |
Internet-Draft | Microsoft |
Intended status: Standards Track | September 04, 2013 |
Expires: March 08, 2014 |
JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-15
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) [RFC4627] based data structures. This specification also describes the semantics and operations that are specific to these algorithms and key types.
Registering the algorithms and identifiers here, rather than in the JWS, JWE, and JWK specifications, is intended to allow them to remain unchanged in the face of changes in the set of Required, Recommended, Optional, and Deprecated algorithms over time. This also allows changes to the JWS, JWE, and JWK specifications without changing this document.
Names defined by this specification are short because a core goal is for the resulting representations to be compact.
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].
These terms defined by the JSON Web Signature (JWS) [JWS] specification are incorporated into this specification:
These terms defined by the JSON Web Encryption (JWE) [JWE] specification are incorporated into this specification:
These terms defined by the JSON Web Key (JWK) [JWK] specification are incorporated into this specification:
These terms are defined for use by this specification:
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 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-PKCS-v1_5 using SHA-256 hash algorithm | Recommended |
RS384 | RSASSA-PKCS-v1_5 using SHA-384 hash algorithm | Optional |
RS512 | RSASSA-PKCS-v1_5 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 |
PS256 | RSASSA-PSS using SHA-256 hash algorithm and MGF1 mask generation function with SHA-256 | Optional |
PS384 | RSASSA-PSS using SHA-384 hash algorithm and MGF1 mask generation function with SHA-384 | Optional |
PS512 | RSASSA-PSS using SHA-512 hash algorithm and MGF1 mask generation function with SHA-512 | Optional |
none | No digital signature or MAC value included | 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.
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.
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]. This section defines the use of the HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 functions [SHS]. The alg (algorithm) header parameter values HS256, HS384, and HS512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded HMAC value using the respective hash function.
A key of the same size as the hash output (for instance, 256 bits for HS256) or larger MUST be used with this algorithm.
The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the hash algorithm "H", using the octets of the ASCII [USASCII] representation of the JWS Signing Input as the "text" value, and using the shared key. The HMAC output value is the JWS Signature. The JWS signature is base64url encoded to produce the Encoded JWS Signature.
The HMAC SHA-256 MAC for a JWS is validated by computing an HMAC value per RFC 2104, using SHA-256 as the hash algorithm "H", using the octets of the ASCII representation of the received JWS Signing Input as the "text" value, and using the shared key. This computed HMAC value is then compared to the result of base64url decoding the received Encoded JWS signature. Alternatively, the computed HMAC value can be base64url encoded and compared to the received Encoded JWS Signature, as this comparison produces the same result as comparing the unencoded values. In either case, if the values match, the HMAC has been validated.
Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is performed identically to the procedure for HMAC SHA-256 - just using the corresponding hash algorithms with correspondingly larger minimum key sizes and result values: 384 bits each for HMAC SHA-384 and 512 bits each for HMAC SHA-512.
An example using this algorithm is shown in Appendix A.1 of [JWS].
This section defines the use of the RSASSA-PKCS1-V1_5 digital signature algorithm as defined in Section 8.2 of RFC 3447 [RFC3447] (commonly known as PKCS #1), using SHA-256, SHA-384, or SHA-512 [SHS] as the hash functions. The alg (algorithm) header parameter values RS256, RS384, and RS512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded RSASSA-PKCS1-V1_5 digital signature using the respective hash function.
A key of size 2048 bits or larger MUST be used with these algorithms.
The RSASSA-PKCS1-V1_5 SHA-256 digital signature is generated as follows:
The output is the Encoded JWS Signature for that JWS.
The RSASSA-PKCS1-V1_5 SHA-256 digital signature for a JWS is validated as follows:
Signing with the RSASSA-PKCS1-V1_5 SHA-384 and RSASSA-PKCS1-V1_5 SHA-512 algorithms is performed identically to the procedure for RSASSA-PKCS1-V1_5 SHA-256 - just using the corresponding hash algorithms instead of SHA-256.
An example using this algorithm is shown in Appendix A.2 of [JWS].
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:
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:
Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 algorithms is performed identically to the procedure for ECDSA P-256 SHA-256 - just using the corresponding hash algorithms with correspondingly larger result values. For ECDSA P-384 SHA-384, R and S will be 384 bits each, resulting in a 96 octet sequence. For ECDSA P-521 SHA-512, R and S will be 521 bits each, resulting in a 132 octet sequence.
Examples using these algorithms are shown in Appendices A.3 and A.4 of [JWS].
This section defines the use of the RSASSA-PSS digital signature algorithm as defined in Section 8.1 of RFC 3447 [RFC3447] with the MGF1 mask generation function, always using the same hash function for both the RSASSA-PSS hash function and the MGF1 hash function. Use of SHA-256, SHA-384, and SHA-512 as these hash functions is defined. The size of the salt value is the same size as the hash function output. All other algorithm parameters use the defaults specified in Section A.2.3 of RFC 3447. The alg (algorithm) header parameter values PS256, PS384, and PS512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded RSASSA-PSS digital signature using the respective hash function in both roles.
A key of size 2048 bits or larger MUST be used with this algorithm.
The RSASSA-PSS SHA-256 digital signature is generated as follows:
The output is the Encoded JWS Signature for that JWS.
The RSASSA-PSS SHA-256 digital signature for a JWS is validated as follows:
Signing with the RSASSA-PSS SHA-384 and RSASSA-PSS SHA-512 algorithms is performed identically to the procedure for RSASSA-PSS SHA-256 - just using the alternative hash algorithm in both roles.
JWSs MAY also be created that do not provide integrity protection. Such a JWS is called a "Plaintext JWS". Plaintext JWSs MUST use the alg value none, and are formatted identically to other JWSs, but with the empty string for its JWS Signature value.
JWE uses cryptographic algorithms to encrypt the Content Encryption Key (CEK) and the Plaintext.
The table below is the set of alg (algorithm) header parameter values that are defined by this specification for use with JWE. These algorithms are used to encrypt the CEK, producing the JWE Encrypted Key, or to use key agreement to agree upon the CEK.
alg Parameter 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+A128KW | 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+A192KW | 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+A256KW | 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.
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 | Implementation Requirements |
---|---|---|---|
A128CBC-HS256 | The AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 4.10.3. This algorithm uses a 256 bit key. | (none) | Required |
A192CBC-HS384 | The AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm, as defined in Section 4.10.4. This algorithm uses a 384 bit key. | (none) | Optional |
A256CBC-HS512 | The AES_256_CBC_HMAC_SHA_512 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.
This section defines the specifics of encrypting a JWE CEK with RSAES-PKCS1-V1_5 [RFC3447]. The alg header parameter value RSA1_5 is used in this case.
A key of size 2048 bits or larger MUST be used with this algorithm.
An example using this algorithm is shown in Appendix A.2 of [JWE].
This section defines the specifics of encrypting a JWE CEK with RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with the default parameters specified by RFC 3447 in Section A.2.1. 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].
This section defines the specifics of encrypting a JWE CEK with the Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using the default initial value specified in Section 2.2.3.1 using 128, 192, or 256 bit keys. The alg header parameter values A128KW, A192KW, or A256KW are respectively used in this case.
An example using this algorithm is shown in Appendix A.3 of [JWE].
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.
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: alg header parameter value ECDH-ES is used in the Direct Key Agreement mode and the values ECDH-ES+A128KW, ECDH-ES+A192KW, or ECDH-ES+A256KW are used in the Key Agreement with Key Wrapping mode.
The
In the Direct Key Agreement case, the output of the Concat KDF MUST be a key of the same length as that used by the enc algorithm; in this case, the empty octet sequence is used as the JWE Encrypted Key value. In the Key Agreement with Key Wrapping case, the output of the Concat KDF MUST be a key of the length needed for the specified key wrapping algorithm, one of 128, 192, or 256 bits respectively.
A new ephemeral public key value MUST be generated for each key agreement operation.
The following Header Parameter Names are reserved and 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 is REQUIRED 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 sender. 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 receiver. 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:
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.
This section defines the specifics of encrypting a JWE Content Encryption Key (CEK) with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128, 192, or 256 bit keys. The alg header parameter values A128GCMKW, A192GCMKW, or A256GCMKW are respectively used in this case.
Use of an Initialization Vector of size 96 bits is REQUIRED with this 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 Header Parameters are used for AES GCM key encryption.
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.
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.
The PBES2-HS256+A128KW, PBES2-HS384+A192KW, and PBES2-HS512+A256KW composite algorithms are used to perform password-based encryption of a JWE CEK, by first deriving a key encryption key from a user-supplied password, then encrypting the JWE CEK using the derived key. These algorithms are PBES2 schemes as specified in Section 6.2 of [RFC2898].
These algorithms use HMAC SHA-2 algorithms as the Pseudo-Random Function (PRF) for the PBKDF2 key derivation and AES Key Wrap [RFC3394] for the encryption scheme. The salt MUST be provided as the p2s header parameter value, and MUST be base64url decoded to obtain the value. The iteration count parameter MUST be provided as the p2c header parameter value. The algorithms respectively use HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 as the PRF and use 128, 192, and 256 bit AES Key Wrap keys. Their derived-key lengths (dkLen) respectively are 16, 24, and 32 octets.
The following Header Parameters are used for Key Encryption with PBES2.
The p2s (PBES2 salt) header parameter contains the PBKDF2 salt value, encoded using base64url. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.
The salt expands the possible keys that can be derived from a given password. A salt value containing 8 or more octets MUST be used. A new salt value MUST be generated randomly for every encryption operation; see [RFC4086] for considerations on generating random values.
The p2c (PBES2 count) header parameter contains the PBKDF2 iteration count, represented as a positive integer. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.
The iteration count adds computational expense, ideally compounded by the possible range of keys introduced by the salt. A minimum iteration count of 1000 is RECOMMENDED.
This section defines a family of authenticated encryption algorithms built using a composition of Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES] [NIST.800-38A] operations and HMAC [RFC2104] [SHS] operations. This algorithm family is called AES_CBC_HMAC_SHA2. It also defines three instances of this family, the first using 128 bit CBC keys and HMAC SHA-256, the second using 192 bit CBC keys and HMAC SHA-384, and the third using 256 bit CBC keys and HMAC SHA-512. Test cases for these algorithms can be found in Appendix C.
These algorithms are based upon Authenticated Encryption with AES-CBC 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 4.10.2.1 and Section 4.10.2.2 define the generic encryption and decryption algorithms. Section 4.10.3 and Section 4.10.5 define instances of AES_CBC_HMAC_SHA2 that specify those details.
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:
Here we denote the number of octets in the MAC_KEY as MAC_KEY_LEN, and the number of octets in ENC_KEY as ENC_KEY_LEN; the values of these parameters are specified by the AEAD algorithms (in
Section 4.10.3 and Section 4.10.5). The number of octets in the input key K is the sum of MAC_KEY_LEN and ENC_KEY_LEN. When generating the secondary keys from K, MAC_KEY and ENC_KEY MUST NOT overlap. Note that the MAC key comes before the encryption key in the input key K; this is in the opposite order of the algorithm names in the identifier "AES_CBC_HMAC_SHA2".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, associated data, initialization vector, and ciphertext, respectively.
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:
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.
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:
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.
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].
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 Parameter 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 MUST be EC.
The following members MUST be present for Elliptic Curve public keys.
The crv (curve) member identifies the cryptographic curve used with the key. Curve values from [DSS] used by this specification are: crv values MAY be used, provided they are understood by implementations using that Elliptic Curve key. The crv value is a case sensitive string.
Additional
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.
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.
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 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.
JWKs can represent RSA [RFC3447] keys. In this case, the kty member value MUST be RSA.
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 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.
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].
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 are RECOMMENDED. If any of the others are present then all 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 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.
The p (first prime factor) member contains the first prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.
The 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.
The dp (first factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the first factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.
The dq (second factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the second factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.
The dp (first CRT coefficient) member contains the Chinese Remainder Theorem (CRT) coefficient of the second factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.
The 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:
The r (prime factor) parameter within an oth array member represents the value of a subsequent prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.
The d (Factor CRT Exponent) parameter within an oth array member represents the CRT exponent of the corresponding prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.
The 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.
When the JWK kty member value is oct (octet sequence), the following member is used to represent a symmetric key (or another key whose value is a single octet sequence):
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 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.
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. Changes of implementation requirements are only permitted on a Specification Required basis, with the new specification defining the revised implementation requirements level.
This specification establishes the IANA JSON Web Key Types registry for values of the JWK kty (key type) parameter. The registry records the kty value, implementation requirements, and a reference to the specification that defines it.
The implementation requirements of a key type MAY be changed over time by the Designated Experts(s) as the cryptographic landscape evolves, for instance, to change the status of a key type to Deprecated, or to change the status of a key type from Optional to Recommended+ or Required. Changes of implementation requirements are only permitted on a Specification Required basis, with the new specification defining the revised implementation requirements level.
This specification registers the values defined in Section 5.1.
This specification registers the parameter names defined in Sections 5.2, 5.3, and 5.4 in the IANA JSON Web Key Parameters registry [JWK].
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].
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.
It is NOT RECOMMENDED to reuse the same key material (Key Encryption Key, Content Encryption Key, Initialization Vector, etc.) to encrypt multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK Set object multiple times. One suggestion for preventing re-use is to always generate a new set key material for each encryption operation, based on the considerations noted in this document as well as from [RFC4086].
While convenient for end users, passwords are vulnerable to a number of attacks. To help mitigate some of these limitations, this document applies principles from [RFC2898] to derive cryptographic keys from user-supplied passwords.
However, the strength of the password still has a significant impact. A high-entry password has greater resistance to dictionary attacks. [NIST-800-63-1] contains guidelines for estimating password entropy, which can help applications and users generate stronger passwords.
An ideal password is one that is as large (or larger) than the derived key length but less than the PRF's block size. Passwords larger than the PRF's block size are first hashed, which reduces an attacker's effective search space to the length of the hash algorithm (32 octets for HMAC SHA-256). It is RECOMMENDED that the password be no longer than 64 octets long for PBES2-HS512+A256KW.
Still, care needs to be taken in where and how password-based encryption is used. Such algorithms MUST NOT be used where the attacker can make an indefinite number of attempts to circumvent the protection.
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.
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.
Algorithm | JWS | XML DSIG | JCA | OID |
---|---|---|---|---|
HMAC using SHA-256 hash algorithm | HS256 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 | HmacSHA256 | 1.2.840.113549.2.9 |
HMAC using SHA-384 hash algorithm | HS384 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha384 | HmacSHA384 | 1.2.840.113549.2.10 |
HMAC using SHA-512 hash algorithm | HS512 | http://www.w3.org/2001/04/xmldsig-more#hmac-sha512 | HmacSHA512 | 1.2.840.113549.2.11 |
RSASSA-PKCS-v1_5 using SHA-256 hash algorithm | RS256 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha256 | SHA256withRSA | 1.2.840.113549.1.1.11 |
RSASSA-PKCS-v1_5 using SHA-384 hash algorithm | RS384 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha384 | SHA384withRSA | 1.2.840.113549.1.1.12 |
RSASSA-PKCS-v1_5 using SHA-512 hash algorithm | RS512 | http://www.w3.org/2001/04/xmldsig-more#rsa-sha512 | SHA512withRSA | 1.2.840.113549.1.1.13 |
ECDSA using P-256 curve and SHA-256 hash algorithm | ES256 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256 | SHA256withECDSA | 1.2.840.10045.4.3.2 |
ECDSA using P-384 curve and SHA-384 hash algorithm | ES384 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384 | SHA384withECDSA | 1.2.840.10045.4.3.3 |
ECDSA using P-521 curve and SHA-512 hash algorithm | ES512 | http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512 | SHA512withECDSA | 1.2.840.10045.4.3.4 |
RSASSA-PSS using SHA-256 hash algorithm and MGF1 mask generation function with SHA-256 | PS256 | |||
RSASSA-PSS using SHA-384 hash algorithm and MGF1 mask generation function with SHA-384 | PS384 | |||
RSASSA-PSS using SHA-512 hash algorithm and MGF1 mask generation function with SHA-512 | PS512 |
This appendix contains a table cross-referencing the alg (algorithm) and enc (encryption method) values used in this specification with the equivalent identifiers used by other standards and software packages. See XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313], and Java Cryptography Architecture [JCA] for more information about the names defined by those documents.
For the composite algorithms A128CBC-HS256, A192CBC-HS384, and A256CBC-HS512, the corresponding AES CBC algorithm identifiers are listed.
Algorithm | JWE | XML ENC | JCA |
---|---|---|---|
RSAES-PKCS1-V1_5 | RSA1_5 | http://www.w3.org/2001/04/xmlenc#rsa-1_5 | RSA/ECB/PKCS1Padding |
RSAES using Optimal Asymmetric Encryption Padding (OAEP) | RSA-OAEP | http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p | RSA/ECB/OAEPWithSHA-1AndMGF1Padding |
Elliptic Curve Diffie-Hellman Ephemeral Static | ECDH-ES | http://www.w3.org/2009/xmlenc11#ECDH-ES | |
Advanced Encryption Standard (AES) Key Wrap Algorithm using 128 bit keys | A128KW | http://www.w3.org/2001/04/xmlenc#kw-aes128 | |
AES Key Wrap Algorithm using 192 bit keys | A192KW | http://www.w3.org/2001/04/xmlenc#kw-aes192 | |
AES Key Wrap Algorithm using 256 bit keys | A256KW | http://www.w3.org/2001/04/xmlenc#kw-aes256 | |
AES in Cipher Block Chaining (CBC) mode with PKCS #5 padding using 128 bit keys | A128CBC-HS256 | http://www.w3.org/2001/04/xmlenc#aes128-cbc | AES/CBC/PKCS5Padding |
AES in CBC mode with PKCS #5 padding using 192 bit keys | A192CBC-HS384 | http://www.w3.org/2001/04/xmlenc#aes192-cbc | AES/CBC/PKCS5Padding |
AES in CBC mode with PKCS #5 padding using 256 bit keys | A256CBC-HS512 | http://www.w3.org/2001/04/xmlenc#aes256-cbc | AES/CBC/PKCS5Padding |
AES in Galois/Counter Mode (GCM) using 128 bit keys | A128GCM | http://www.w3.org/2009/xmlenc11#aes128-gcm | AES/GCM/NoPadding |
AES GCM using 192 bit keys | A192GCM | http://www.w3.org/2009/xmlenc11#aes192-gcm | AES/GCM/NoPadding |
AES GCM using 256 bit keys | A256GCM | http://www.w3.org/2009/xmlenc11#aes256-gcm | AES/GCM/NoPadding |
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.
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 4.7. 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:
Concatenating the parameters AlgorithmID through SuppPubInfo results in an otherInfo value of:
[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,
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:
[186, 193, 41, 192, 82, 2, 254, 170, 230, 4, 76, 103, 180, 92, 49, 48]
The base64url encoded representation of this derived key is:
usEpwFIC_qrmBExntFwxMA
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.
[[ to be removed by the RFC editor before publication as an RFC ]]
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