JOSE Working Group | M.B. Jones |
Internet-Draft | Microsoft |
Intended status: Standards Track | April 26, 2013 |
Expires: October 28, 2013 |
JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-10
The JSON Web Algorithms (JWA) specification enumerates cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 28, 2013.
Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
The JSON Web Algorithms (JWA) specification enumerates cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS) [JWS], JSON Web Encryption (JWE) [JWE], and JSON Web Key (JWK) [JWK] specifications. All these specifications utilize JavaScript Object Notation (JSON) [RFC4627] based data structures. This specification also describes the semantics and operations that are specific to these algorithms and key types.
Enumerating the algorithms and identifiers for them in this specification, rather than in the JWS, JWE, and JWK specifications, is intended to allow them to remain unchanged in the face of changes in the set of required, recommended, optional, and deprecated algorithms over time.
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 use of the following algorithms for producing JWSs is defined in this section.
The table below is the set of alg (algorithm) header parameter values defined by this specification for use with JWS, each of which is explained in more detail in the following sections:
alg Parameter Value | Digital Signature or MAC Algorithm | Implementation Requirements |
---|---|---|
HS256 | HMAC using SHA-256 hash algorithm | REQUIRED |
HS384 | HMAC using SHA-384 hash algorithm | OPTIONAL |
HS512 | HMAC using SHA-512 hash algorithm | OPTIONAL |
RS256 | RSASSA using SHA-256 hash algorithm | RECOMMENDED |
RS384 | RSASSA using SHA-384 hash algorithm | OPTIONAL |
RS512 | RSASSA using SHA-512 hash algorithm | OPTIONAL |
ES256 | ECDSA using P-256 curve and SHA-256 hash algorithm | RECOMMENDED+ |
ES384 | ECDSA using P-384 curve and SHA-384 hash algorithm | OPTIONAL |
ES512 | ECDSA using P-521 curve and SHA-512 hash algorithm | OPTIONAL |
none | No digital signature or MAC value included | REQUIRED |
All the names are short because a core goal of JWS is for the representations to be compact. However, there is no a priori length restriction on alg values.
The use of "+" in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.
See Appendix A for a table cross-referencing the digital signature and MAC alg (algorithm) values used in this specification with the equivalent identifiers used by other standards and software packages.
Hash-based Message Authentication Codes (HMACs) enable one to use a secret plus a cryptographic hash function to generate a Message Authentication Code (MAC). This can be used to demonstrate that the MAC matches the hashed content, in this case the JWS Signing Input, which therefore demonstrates that whoever generated the MAC was in possession of the secret. The means of exchanging the shared key is outside the scope of this specification.
The algorithm for implementing and validating HMACs is provided in RFC 2104 [RFC2104]. This section defines the use of the HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 functions [SHS]. The alg (algorithm) header parameter values HS256, HS384, and HS512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded HMAC value using the respective hash function.
A key of the same size as the hash output (for instance, 256 bits for HS256) or larger MUST be used with this algorithm.
The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the hash algorithm "H", using the 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. If the validation fails, the JWS MUST be rejected.
Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is performed identically to the procedure for HMAC SHA-256 - just using the corresponding hash algorithm with correspondingly larger minimum key sizes and result values: 384 bits each for HMAC SHA-384 and 512 bits each for HMAC SHA-512.
An example using this algorithm is shown in Appendix A.1 of [JWS].
This section defines the use of the RSASSA-PKCS1-V1_5 digital signature algorithm as defined in Section 8.2 of RFC 3447 [RFC3447], (commonly known as PKCS #1), using SHA-256, SHA-384, or SHA-512 [SHS] as the hash functions. The alg (algorithm) header parameter values RS256, RS384, and RS512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded RSA digital signature using the respective hash function.
A key of size 2048 bits or larger MUST be used with these algorithms.
The RSA SHA-256 digital signature is generated as follows:
The output is the Encoded JWS Signature for that JWS.
The RSA SHA-256 digital signature for a JWS is validated as follows:
Signing with the RSA SHA-384 and RSA SHA-512 algorithms is performed identically to the procedure for RSA SHA-256 - just using the corresponding hash algorithm with correspondingly larger result values: 384 bits for RSA SHA-384 and 512 bits for RSA SHA-512.
An example using this algorithm is shown in Appendix A.2 of [JWS].
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:
Note that ECDSA digital signature contains a value referred to as K, which is a random number generated for each digital signature instance. This means that two ECDSA digital signatures using exactly the same input parameters will output different signature values because their K values will be different. A consequence of this is that one cannot validate an ECDSA signature by recomputing the signature and comparing the results.
Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 algorithms is performed identically to the procedure for ECDSA P-256 SHA-256 - just using the corresponding hash algorithm with correspondingly larger result values. For ECDSA P-384 SHA-384, R and S will be 384 bits each, resulting in a 96 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].
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.
Additional algorithms MAY be used to protect JWSs with corresponding alg (algorithm) header parameter values being defined to refer to them. New alg header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 or be a value that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML DSIG [RFC3275], XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124], and related specifications as alg values.
As indicated by the common registry, JWSs and JWEs share a common alg value space. The values used by the two specifications MUST be distinct, as the alg value can be used to determine whether the object is a JWS or JWE.
Likewise, additional reserved Header Parameter Names MAY be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS]. As indicated by the common registry, JWSs and JWEs share a common header parameter space; when a parameter is used by both specifications, its usage must be compatible between the specifications.
JWE uses cryptographic algorithms to encrypt the Content Encryption Key (CEK) and the Plaintext. This section specifies a set of specific algorithms for these purposes.
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 | Implementation Requirements |
---|---|---|
RSA1_5 | RSAES-PKCS1-V1_5 [RFC3447] | REQUIRED |
RSA-OAEP | RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with the default parameters specified by RFC 3447 in Section A.2.1 | 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 | RECOMMENDED |
A256KW | AES Key Wrap Algorithm using the default initial value specified in Section 2.2.3.1 and using 256 bit keys | RECOMMENDED |
dir | Direct use of a shared symmetric key as the Content Encryption Key (CEK) for the block encryption step (rather than using the symmetric key to wrap the CEK) | 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 | RECOMMENDED+ |
ECDH-ES+A128KW | Elliptic Curve Diffie-Hellman Ephemeral Static key agreement per ECDH-ES and Section 4.7, but 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) | RECOMMENDED |
ECDH-ES+A256KW | Elliptic Curve Diffie-Hellman Ephemeral Static key agreement per ECDH-ES and Section 4.7, but 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) | RECOMMENDED |
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 | Block Encryption Algorithm | Implementation Requirements |
---|---|---|
A128CBC-HS256 | The AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 4.8.3. This algorithm uses a 256 bit key. | REQUIRED |
A256CBC-HS512 | The AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm, as defined in Section 4.8.4. This algorithm uses a 512 bit key. | REQUIRED |
A128GCM | AES in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 bit keys | RECOMMENDED |
A256GCM | AES GCM using 256 bit keys | RECOMMENDED |
All the names are short because a core goal of JWE is for the representations to be compact. However, there is no a priori length restriction on alg 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 or 256 bit keys. The alg header parameter values A128KW or A256KW are used in this case.
An example using this algorithm is shown in Appendix A.3 of [JWE].
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], and using the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A]. The key agreement result can be used in one of two ways: alg header parameter value ECDH-ES is used in the Direct Key Agreement mode and the values ECDH-ES+A128KW and 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, either 128 or 256 bits respectively.
A new epk (ephemeral public key) value MUST be generated for each key agreement transaction.
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:
This section defines a family of authenticated encryption algorithms built using a composition of Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES] [NIST.800-38A] operations and HMAC [RFC2104] [SHS] operations. This algorithm family is called AES_CBC_HMAC_SHA2. It also defines two instances of this family, one using 128 bit CBC keys and HMAC SHA-256 and the other using 256 bit CBC keys and HMAC SHA-512. Test cases for these algorithms can be found in Appendix C.
These algorithms are based upon Authenticated Encryption with AES-CBC and HMAC-SHA [I-D.mcgrew-aead-aes-cbc-hmac-sha2], performing the same cryptographic computations, but with the Initialization Vector and Authentication Tag values remaining separate, rather than being concatenated with the Ciphertext value in the output representation. This algorithm family is a generalization of the algorithm family in [I-D.mcgrew-aead-aes-cbc-hmac-sha2], and can be used to implement those algorithms.
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 4.8.2.1 and Section 4.8.2.2 define the generic encryption and decryption algorithms. Section 4.8.3 and Section 4.8.4 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 4.8.3 and Section 4.8.4). The number of octets in the input key K is the sum of MAC_KEY_LEN and ENC_KEY_LEN. When generating the secondary keys from K, MAC_KEY and ENC_KEY MUST NOT overlap. Note that the MAC key comes before the encryption key in the input key K; this is in the opposite order of the algorithm names in the identifier "AES_CBC_HMAC_SHA2".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_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 A256CBC-HS512 is used as the alg value when using AES_256_CBC_HMAC_SHA_512 with JWE. In both cases, the Additional Authenticated Data value used is the concatenation of the Encoded JWE Header value, a period ('.') character, and the Encoded JWE Encrypted Key. 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 or 256 bit keys. The enc header parameter values A128GCM or A256GCM are 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 parameter is used to secure the header and key values. (The Additional Authenticated Data value used is the octets of the ASCII representation of the concatenation of the Encoded JWE Header, a period ('.') character, and the Encoded JWE Encrypted Key per Section 5 of the JWE specification.) This same Additional Authenticated Data value is used when decrypting as well.
The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size.
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].
Additional algorithms MAY be used to protect JWEs with corresponding alg (algorithm) and enc (encryption method) header parameter values being defined to refer to them. New alg and enc header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 or be a value that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313], and related specifications as alg and enc values.
As indicated by the common registry, JWSs and JWEs share a common alg value space. The values used by the two specifications MUST be distinct, as the alg value can be used to determine whether the object is a JWS or JWE.
Likewise, additional reserved Header Parameter Names MAY be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS]. As indicated by the common registry, JWSs and JWEs share a common header parameter space; when a parameter is used by both specifications, its usage must be compatible between the specifications.
A JSON Web Key (JWK) [JWK] is a JavaScript Object Notation (JSON) [RFC4627] data structure that represents a cryptographic key. A JSON Web Key Set (JWK Set) is a JSON data structure for representing a set of JWKs. This section specifies a set of key types to be used for those keys and the key type specific parameters for representing those keys. Parameters are defined for public, private, and symmetric keys.
The table below is the set of kty (key type) parameter values that are defined by this specification for use in JWKs.
kty Parameter Value | Key Type | Implementation Requirements |
---|---|---|
EC | Elliptic Curve [DSS] key type | RECOMMENDED+ |
RSA | RSA [RFC3447] key type | REQUIRED |
oct | Octet sequence key type (used to represent symmetric keys) | RECOMMENDED+ |
All the names are short because a core goal of JWK is for the representations to be compact. However, there is no a priori length restriction on kty values.
The use of "+" in the Implementation Requirements indicates that the requirement strength is likely to be increased in a future version of the specification.
JWKs can represent Elliptic Curve [DSS] keys. In this case, the kty member value MUST be EC.
These 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.
These 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. All are REQUIRED for RSA private keys except for oth, which is sometimes REQUIRED and sometimes MUST NOT be present, as described below.
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.
Keys using additional key types can be represented using JWK data structures with corresponding kty (key type) parameter values being defined to refer to them. New kty parameter values SHOULD either be registered in the IANA JSON Web Key Types registry Section 6.2 or be a value that contains a Collision Resistant Namespace.
Likewise, parameters for representing keys for additional key types or additional key properties SHOULD either be registered in the IANA JSON Web Key Parameters registry [JWK] or be a value that contains a Collision Resistant Namespace.
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.
This specification establishes the IANA JSON Web Key Types registry for values of the JWK kty (key type) parameter. The registry records the kty value and a reference to the specification that defines it. This specification registers the values defined in Section 5.1.
This specification registers the parameter names defined in Sections 5.2, 5.3, and 5.3.3 in the IANA JSON Web Key Parameters registry [JWK].
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.
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-PKCS1 for new applications and instead requests that people transition to RSASSA-PSS, this specification does include RSASSA-PKCS1, 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.
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.
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 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 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 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 |
This appendix contains a table cross-referencing the alg (algorithm) and enc (encryption method) values used in this specification with the equivalent identifiers used by other standards and software packages. See XML Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313], and Java Cryptography Architecture [JCA] for more information about the names defined by those documents.
For the composite algorithms A128CBC-HS256 and A256CBC-HS512, the corresponding AES CBC algorithm identifiers are listed.
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 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 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 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 4.8. 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 4.8. 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 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
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.
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, 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 ]]
-10
-09
-08
-07
-06
-05
-04
-03
-02
-01
-00