JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-11

Abstract

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

Status of this Memo

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This Internet-Draft will expire on November 29, 2013.

Copyright Notice

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Table of Contents

1.  Introduction
    1.1.  Notational Conventions
2.  Terminology
    2.1.  Terms Incorporated from the JWS Specification
    2.2.  Terms Incorporated from the JWE Specification
    2.3.  Terms Incorporated from the JWK Specification
    2.4.  Defined Terms
3.  Cryptographic Algorithms for JWS
    3.1.  "alg" (Algorithm) Header Parameter Values for JWS
    3.2.  MAC with HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512
    3.3.  Digital Signature with RSASSA-PKCS1-V1_5 and SHA-256, SHA-384, or SHA-512
    3.4.  Digital Signature with ECDSA P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512
    3.5.  Digital Signature with RSASSA-PSS and SHA-256 or SHA-512
    3.6.  Using the Algorithm "none"
    3.7.  Additional Digital Signature/MAC Algorithms and Parameters
4.  Cryptographic Algorithms for JWE
    4.1.  "alg" (Algorithm) Header Parameter Values for JWE
    4.2.  "enc" (Encryption Method) Header Parameter Values for JWE
    4.3.  Key Encryption with RSAES-PKCS1-V1_5
    4.4.  Key Encryption with RSAES OAEP
    4.5.  Key Wrapping with AES Key Wrap
    4.6.  Direct Encryption with a Shared Symmetric Key
    4.7.  Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static (ECDH-ES)
        4.7.1.  Key Derivation for "ECDH-ES"
    4.8.  AES_CBC_HMAC_SHA2 Algorithms
        4.8.1.  Conventions Used in Defining AES_CBC_HMAC_SHA2
        4.8.2.  Generic AES_CBC_HMAC_SHA2 Algorithm
            4.8.2.1.  AES_CBC_HMAC_SHA2 Encryption
            4.8.2.2.  AES_CBC_HMAC_SHA2 Decryption
        4.8.3.  AES_128_CBC_HMAC_SHA_256
        4.8.4.  AES_256_CBC_HMAC_SHA_512
        4.8.5.  Plaintext Encryption with AES_CBC_HMAC_SHA2
    4.9.  Plaintext Encryption with AES GCM
    4.10.  Additional Encryption Algorithms and Parameters
5.  Cryptographic Algorithms for JWK
    5.1.  "kty" (Key Type) Parameter Values for JWK
    5.2.  JWK Parameters for Elliptic Curve Keys
        5.2.1.  JWK Parameters for Elliptic Curve Public Keys
            5.2.1.1.  "crv" (Curve) Parameter
            5.2.1.2.  "x" (X Coordinate) Parameter
            5.2.1.3.  "y" (Y Coordinate) Parameter
        5.2.2.  JWK Parameters for Elliptic Curve Private Keys
            5.2.2.1.  "d" (ECC Private Key) Parameter
    5.3.  JWK Parameters for RSA Keys
        5.3.1.  JWK Parameters for RSA Public Keys
            5.3.1.1.  "n" (Modulus) Parameter
            5.3.1.2.  "e" (Exponent) Parameter
        5.3.2.  JWK Parameters for RSA Private Keys
            5.3.2.1.  "d" (Private Exponent) Parameter
            5.3.2.2.  "p" (First Prime Factor) Parameter
            5.3.2.3.  "q" (Second Prime Factor) Parameter
            5.3.2.4.  "dp" (First Factor CRT Exponent) Parameter
            5.3.2.5.  "dq" (Second Factor CRT Exponent) Parameter
            5.3.2.6.  "qi" (First CRT Coefficient) Parameter
            5.3.2.7.  "oth" (Other Primes Info) Parameter
        5.3.3.  JWK Parameters for Symmetric Keys
            5.3.3.1.  "k" (Key Value) Parameter
    5.4.  Additional Key Types and Parameters
6.  IANA Considerations
    6.1.  JSON Web Signature and Encryption Algorithms Registry
        6.1.1.  Template
        6.1.2.  Initial Registry Contents
    6.2.  JSON Web Key Types Registry
        6.2.1.  Registration Template
        6.2.2.  Initial Registry Contents
    6.3.  JSON Web Key Parameters Registration
        6.3.1.  Registry Contents
7.  Security Considerations
8.  References
    8.1.  Normative References
    8.2.  Informative References
Appendix A.  Digital Signature/MAC Algorithm Identifier Cross-Reference
Appendix B.  Encryption Algorithm Identifier Cross-Reference
Appendix C.  Test Cases for AES_CBC_HMAC_SHA2 Algorithms
    C.1.  Test Cases for AES_128_CBC_HMAC_SHA_256
    C.2.  Test Cases for AES_256_CBC_HMAC_SHA_512
Appendix D.  Acknowledgements
Appendix E.  Document History
§  Author's Address

1.  Introduction

The JSON Web Algorithms (JWA) specification enumerates cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS) [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.), JSON Web Encryption (JWE) [JWE] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.), and JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.) specifications. All these specifications utilize JavaScript Object Notation (JSON) [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) 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.

1.1.  Notational Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in Key words for use in RFCs to Indicate Requirement Levels [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

2.  Terminology

2.1.  Terms Incorporated from the JWS Specification

These terms defined by the JSON Web Signature (JWS) [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) specification are incorporated into this specification:

JSON Web Signature (JWS)

A data structure representing a digitally signed or MACed message. The structure represents three values: the JWS Header, the JWS Payload, and the JWS Signature.

JSON Text Object

A UTF-8 [RFC3629] (Yergeau, F., “UTF-8, a transformation format of ISO 10646,” November 2003.) encoded text string representing a JSON object; the syntax of JSON objects is defined in Section 2.2 of [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.).

JWS Header

A JSON Text Object (or JSON Text Objects, when using the JWS JSON Serialization) that describes the digital signature or MAC operation applied to create the JWS Signature value. The members of the JWS Header object(s) are Header Parameters.

JWS Payload

The sequence of octets to be secured -- a.k.a., the message. The payload can contain an arbitrary sequence of octets.

JWS Signature

A sequence of octets containing the cryptographic material that ensures the integrity of the JWS Protected Header and the JWS Payload. The JWS Signature value is a digital signature or MAC value calculated over the JWS Signing Input using the parameters specified in the JWS Header.

JWS Protected Header

A JSON Text Object that contains the portion of the JWS Header that is integrity protected. For the JWS Compact Serialization, this comprises the entire JWS Header. For the JWS JSON Serialization, this is one component of the JWS Header.

Base64url Encoding

The URL- and filename-safe Base64 encoding described in RFC 4648 (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” October 2006.) [RFC4648], Section 5, with the (non URL-safe) '=' padding characters omitted, as permitted by Section 3.2. (See Appendix C of [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.) for notes on implementing base64url encoding without padding.)

Encoded JWS Header

Base64url encoding of the JWS Protected Header.

Encoded JWS Payload

Base64url encoding of the JWS Payload.

Encoded JWS Signature

Base64url encoding of the JWS Signature.

JWS Signing Input

The concatenation of the Encoded JWS Header, a period ('.') character, and the Encoded JWS Payload.

Collision Resistant Namespace

A namespace that allows names to be allocated in a manner such that they are highly unlikely to collide with other names. For instance, collision resistance can be achieved through administrative delegation of portions of the namespace or through use of collision-resistant name allocation functions. Examples of Collision Resistant Namespaces include: Domain Names, Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670 Recommendation series, and Universally Unique IDentifiers (UUIDs) [RFC4122] (Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace,” July 2005.). When using an administratively delegated namespace, the definer of a name needs to take reasonable precautions to ensure they are in control of the portion of the namespace they use to define the name.

2.2.  Terms Incorporated from the JWE Specification

These terms defined by the JSON Web Encryption (JWE) [JWE] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.) specification are incorporated into this specification:

JSON Web Encryption (JWE)

A data structure representing an encrypted message. The structure represents five values: the JWE Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, and the JWE Authentication Tag.

Authenticated Encryption

An Authenticated Encryption algorithm is one that provides an integrated content integrity check. Authenticated Encryption algorithms accept two inputs, the Plaintext and the Additional Authenticated Data value, and produce two outputs, the Ciphertext and the Authentication Tag value. AES Galois/Counter Mode (GCM) is one such algorithm.

Plaintext

The sequence of octets to be encrypted -- a.k.a., the message. The plaintext can contain an arbitrary sequence of octets.

Ciphertext

An encrypted representation of the Plaintext.

Additional Authenticated Data (AAD)

An input to an Authenticated Encryption operation that is integrity protected but not encrypted.

Authentication Tag

An output of an Authenticated Encryption operation that ensures the integrity of the Ciphertext and the Additional Authenticated Data. Note that some algorithms may not use an Authentication Tag, in which case this value is the empty octet sequence.

Content Encryption Key (CEK)

A symmetric key for the Authenticated Encryption algorithm used to encrypt the Plaintext for the recipient to produce the Ciphertext and the Authentication Tag.

JWE Header

A JSON Text Object (or JSON Text Objects, when using the JWE JSON Serialization) that describes the encryption operations applied to create the JWE Encrypted Key, the JWE Ciphertext, and the JWE Authentication Tag. The members of the JWE Header object(s) are Header Parameters.

JWE Encrypted Key

The result of encrypting the Content Encryption Key (CEK) with the intended recipient's key using the specified algorithm. Note that for some algorithms, the JWE Encrypted Key value is specified as being the empty octet sequence.

JWE Initialization Vector

A sequence of octets containing the Initialization Vector used when encrypting the Plaintext. Note that some algorithms may not use an Initialization Vector, in which case this value is the empty octet sequence.

JWE Ciphertext

A sequence of octets containing the Ciphertext for a JWE.

JWE Authentication Tag

A sequence of octets containing the Authentication Tag for a JWE.

JWE Protected Header

A JSON Text Object that contains the portion of the JWE Header that is integrity protected. For the JWE Compact Serialization, this comprises the entire JWE Header. For the JWE JSON Serialization, this is one component of the JWE Header.

Encoded JWE Header

Base64url encoding of the JWE Protected Header.

Encoded JWE Encrypted Key

Base64url encoding of the JWE Encrypted Key.

Encoded JWE Initialization Vector

Base64url encoding of the JWE Initialization Vector.

Encoded JWE Ciphertext

Base64url encoding of the JWE Ciphertext.

Encoded JWE Authentication Tag

Base64url encoding of the JWE Authentication Tag.

Key Management Mode

A method of determining the Content Encryption Key (CEK) value to use. Each algorithm used for determining the CEK value uses a specific Key Management Mode. Key Management Modes employed by this specification are Key Encryption, Key Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping, and Direct Encryption.

Key Encryption

A Key Management Mode in which the Content Encryption Key (CEK) value is encrypted to the intended recipient using an asymmetric encryption algorithm.

Key Wrapping

A Key Management Mode in which the Content Encryption Key (CEK) value is encrypted to the intended recipient using a symmetric key wrapping algorithm.

Direct Key Agreement

A Key Management Mode in which a key agreement algorithm is used to agree upon the Content Encryption Key (CEK) value.

Key Agreement with Key Wrapping

A Key Management Mode in which a key agreement algorithm is used to agree upon a symmetric key used to encrypt the Content Encryption Key (CEK) value to the intended recipient using a symmetric key wrapping algorithm.

Direct Encryption

A Key Management Mode in which the Content Encryption Key (CEK) value used is the secret symmetric key value shared between the parties.

2.3.  Terms Incorporated from the JWK Specification

These terms defined by the JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.) specification are incorporated into this specification:

JSON Web Key (JWK)

A JSON object that represents a cryptographic key.

JSON Web Key Set (JWK Set)

A JSON object that contains an array of JWKs as the value of its keys member.

2.4.  Defined Terms

These terms are defined for use by this specification:

Header Parameter

A name/value pair that is member of a JWS Header or JWE Header.

Header Parameter Name

The name of a member of a JSON object representing a JWS Header or JWE Header.

Header Parameter Value

The value of a member of a JSON object representing a JWS Header or JWE Header.

3.  Cryptographic Algorithms for JWS

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

3.1.  "alg" (Algorithm) Header Parameter Values for JWS

The table below is the set of alg (algorithm) header parameter values defined by this specification for use with JWS, each of which is explained in more detail in the following sections:

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 (Digital Signature/MAC Algorithm Identifier Cross-Reference) 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.

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

Hash-based Message Authentication Codes (HMACs) enable one to use a secret plus a cryptographic hash function to generate a Message Authentication Code (MAC). This can be used to demonstrate that the MAC matches the hashed content, in this case the JWS 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 (Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” February 1997.) [RFC2104]. This section defines the use of the HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 functions [SHS] (National Institute of Standards and Technology, “Secure Hash Standard (SHS),” October 2008.). 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] (American National Standards Institute, “Coded Character Set -- 7-bit American Standard Code for Information Interchange,” 1986.) 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] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.).

3.3.  Digital Signature with RSASSA-PKCS1-V1_5 and SHA-256, SHA-384, or SHA-512

This section defines the use of the RSASSA-PKCS1-V1_5 digital signature algorithm as defined in Section 8.2 of RFC 3447 (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.) [RFC3447] (commonly known as PKCS #1), using SHA-256, SHA-384, or SHA-512 [SHS] (National Institute of Standards and Technology, “Secure Hash Standard (SHS),” October 2008.) 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:

1. Generate a digital signature of the octets of the ASCII representation of the JWS Signing Input using RSASSA-PKCS1-V1_5-SIGN and the SHA-256 hash function with the desired private key. The output will be an octet sequence.
2. Base64url encode the resulting octet sequence.

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:

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

Signing with the 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 algorithm with correspondingly larger result values: 384 bits for RSASSA-PKCS1-V1_5 SHA-384 and 512 bits for RSASSA-PKCS1-V1_5 SHA-512.

An example using this algorithm is shown in Appendix A.2 of [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.).

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

The Elliptic Curve Digital Signature Algorithm (ECDSA) [DSS] (National Institute of Standards and Technology, “Digital Signature Standard (DSS),” June 2009.) 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] (National Institute of Standards and Technology, “Digital Signature Standard (DSS),” June 2009.). The alg (algorithm) header parameter values ES256, ES384, and ES512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded ECDSA P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512 digital signature, respectively.

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

1. Generate a digital signature of the octets of the ASCII representation of the JWS Signing Input using ECDSA P-256 SHA-256 with the desired private key. The output will be the pair (R, S), where R and S are 256 bit unsigned integers.
2. Turn R and S into octet sequences in big endian order, with each array being be 32 octets long. The array representations MUST NOT be shortened to omit any leading zero octets contained in the values.
3. Concatenate the two octet sequences in the order R and then S. (Note that many ECDSA implementations will directly produce this concatenation as their output.)
4. Base64url encode the resulting 64 octet sequence.

The output is the Encoded JWS Signature for the JWS.

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

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

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

Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512 algorithms is performed identically to the procedure for ECDSA P-256 SHA-256 - just using the corresponding hash algorithm with correspondingly larger result values. For ECDSA P-384 SHA-384, R and S will be 384 bits each, resulting in a 96 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] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.).

3.5.  Digital Signature with RSASSA-PSS and SHA-256 or SHA-512

This section defines the use of the RSASSA-PSS digital signature algorithm as defined in Section 8.1 of RFC 3447 (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.) [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 both SHA-256 and SHA-512 as these hash functions is defined. All other algorithm parameters use the defaults specified in Section A.2.3 of RFC 3447. The alg (algorithm) header parameter values PS256 and PS512 is 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:

1. Generate a digital signature of the octets of the ASCII representation of the JWS Signing Input using RSASSA-PSS-SIGN, the SHA-256 hash function, and the MGF1 mask generation function with SHA-256 with the desired private key. The output will be an octet sequence.
2. Base64url encode the resulting octet sequence.

The output is the Encoded JWS Signature for that JWS.

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

1. Take the Encoded JWS Signature and base64url decode it into an octet sequence. If decoding fails, the JWS MUST be rejected.
2. Submit the octets of the ASCII representation of the JWS Signing Input and the public key corresponding to the private key used by the signer to the RSASSA-PSS-VERIFY algorithm using SHA-256 as the hash function and using MGF1 as the mask generation function with SHA-256.
3. If the validation fails, the JWS MUST be rejected.

Signing with the RSASSA-PSS SHA-512 algorithm is performed identically to the procedure for RSASSA-PSS SHA-256 - just using the alternative hash algorithm in both roles.

3.6.  Using the Algorithm "none"

JWSs MAY also be created that do not provide integrity protection. Such a JWS is called 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.

3.7.  Additional Digital Signature/MAC Algorithms and Parameters

Additional algorithms MAY be used to protect JWSs with corresponding alg (algorithm) header parameter values being defined to refer to them. New alg header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 (JSON Web Signature and Encryption Algorithms Registry) or be a value that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML DSIG (Eastlake, D., Reagle, J., and D. Solo, “(Extensible Markup Language) XML-Signature Syntax and Processing,” March 2002.) [RFC3275], XML DSIG 2.0 (Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P., Hirsch, F., Cantor, S., and T. Roessler, “XML Signature Syntax and Processing Version 2.0,” January 2012.) [W3C.CR‑xmldsig‑core2‑20120124], and related specifications as alg values.

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

Likewise, additional reserved Header Parameter Names can be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.). 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.

4.  Cryptographic Algorithms for JWE

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.

4.1.  "alg" (Algorithm) Header Parameter Values for JWE

The table below is the set of alg (algorithm) header parameter values that are defined by this specification for use with JWE. These algorithms are used to encrypt the CEK, producing the JWE Encrypted Key, or to use key agreement to agree upon the CEK.

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

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

The table below is the set of enc (encryption method) header parameter values that are defined by this specification for use with JWE. These algorithms are used to encrypt the Plaintext, which produces the Ciphertext.

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 (Encryption Algorithm Identifier Cross-Reference) 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.

4.3.  Key Encryption with RSAES-PKCS1-V1_5

This section defines the specifics of encrypting a JWE CEK with RSAES-PKCS1-V1_5 [RFC3447] (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.). 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] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.).

4.4.  Key Encryption with RSAES OAEP

This section defines the specifics of encrypting a JWE CEK with RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447] (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.), 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] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.).

4.5.  Key Wrapping with AES Key Wrap

This section defines the specifics of encrypting a JWE CEK with the Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] (Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” September 2002.) 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] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.).

4.6.  Direct Encryption with a Shared Symmetric Key

This section defines the specifics of directly performing symmetric key encryption without performing a key wrapping step. In this case, the shared symmetric key is used directly as the Content 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.

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

This section defines the specifics of key agreement with Elliptic Curve Diffie-Hellman Ephemeral Static [RFC6090] (McGrew, D., Igoe, K., and M. Salter, “Fundamental Elliptic Curve Cryptography Algorithms,” February 2011.), and using the Concat KDF, as defined in Section 5.8.1 of [NIST.800‑56A] (National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised),” March 2007.). The key agreement result can be used in one of two ways:

1. directly as the Content Encryption Key (CEK) for the enc algorithm, in the Direct Key Agreement mode, or
2. as a symmetric key used to wrap the CEK with either the A128KW or A256KW algorithms, in the Key Agreement with Key Wrapping mode.

The 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.

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.

4.7.1.  Key Derivation for "ECDH-ES"

The key derivation process derives the agreed upon key from the shared secret Z established through the ECDH algorithm, per Section 6.2.2.2 of [NIST.800‑56A] (National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised),” March 2007.).

Key derivation is performed using the Concat KDF, as defined in Section 5.8.1 of [NIST.800‑56A] (National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised),” March 2007.), where the Digest Method is SHA-256. The Concat KDF parameters are set as follows:

Z

This is set to the representation of the shared secret Z as an octet sequence.

keydatalen

This is set to the number of bits in the desired output key. For ECDH-ES, this is length of the key used by the enc algorithm. For ECDH-ES+A128KW, and ECDH-ES+A256KW, this is 128 and 256, respectively.

AlgorithmID

This is set to the octets of the UTF-8 representation of the alg header parameter value.

PartyUInfo

PartyUInfo contains a random data value provided by the sender. If provided, this value MUST contain at least 512 bits and a unique value SHOULD be used for each recipient. Use of PartyUInfo is OPTIONAL when a different ephemeral key is used for each key agreement transaction. The PartyUInfo value is of the form Datalen || Data, where Data is a variable-length string of zero or more octets, and Datalen is a fixed-length, big endian 32 bit counter that indicates the length (in octets) of Data, with || being concatenation. If an apu (agreement PartyUInfo) header parameter is present, Data is set to the result of base64url decoding the apu value and Datalen is set to the number of octets in Data. Otherwise, Datalen is set to 0 and Data is set to the empty octet sequence.

PartyVInfo

This is set to the empty octet sequence.

SuppPubInfo

This is set to the keydatalen represented as a 32 bit big endian integer.

SuppPrivInfo

This is set to the empty octet sequence.

4.8.  AES_CBC_HMAC_SHA2 Algorithms

This section defines a family of authenticated encryption algorithms built using a composition of Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) [NIST.800‑38A] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation,” December 2001.) operations and HMAC [RFC2104] (Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” February 1997.) [SHS] (National Institute of Standards and Technology, “Secure Hash Standard (SHS),” October 2008.) 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 (Test Cases for AES_CBC_HMAC_SHA2 Algorithms).

These algorithms are based upon Authenticated Encryption with AES-CBC and HMAC-SHA (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.) [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] (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.), and can be used to implement those algorithms.

4.8.1.  Conventions Used in Defining AES_CBC_HMAC_SHA2

We use the following notational conventions.

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

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

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

4.8.2.  Generic AES_CBC_HMAC_SHA2 Algorithm

This section defines AES_CBC_HMAC_SHA2 in a manner that is independent of the AES CBC key size or hash function to be used. Section 4.8.2.1 (AES_CBC_HMAC_SHA2 Encryption) and Section 4.8.2.2 (AES_CBC_HMAC_SHA2 Decryption) define the generic encryption and decryption algorithms. Section 4.8.3 (AES_128_CBC_HMAC_SHA_256) and Section 4.8.4 (AES_256_CBC_HMAC_SHA_512) define instances of AES_CBC_HMAC_SHA2 that specify those details.

4.8.2.1.  AES_CBC_HMAC_SHA2 Encryption

The authenticated encryption algorithm takes as input four octet strings: a secret key K, a plaintext P, associated data A, and an initialization vector IV. The authenticated ciphertext value E and the authentication tag value T are provided as outputs. The data in the plaintext are encrypted and authenticated, and the associated data are authenticated, but not encrypted.

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

1. The secondary keys MAC_KEY and ENC_KEY are generated from the input key K as follows. Each of these two keys is an octet string.

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

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

   Here we denote the number of octets in the MAC_KEY as MAC_KEY_LEN, and the number of octets in ENC_KEY as ENC_KEY_LEN; the values of these parameters are specified by the AEAD algorithms (in Section 4.8.3 (AES_128_CBC_HMAC_SHA_256) and Section 4.8.4 (AES_256_CBC_HMAC_SHA_512)). 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".
2. The Initialization Vector (IV) used is a 128 bit value generated randomly or pseudorandomly for use in the cipher.
3. The plaintext is CBC encrypted using PKCS #5 padding using ENC_KEY as the key, and the IV. We denote the ciphertext output from this step as E.
4. The octet string AL is equal to the number of bits in A expressed as a 64-bit unsigned integer in network byte order.
5. A message authentication tag T is computed by applying HMAC [RFC2104] (Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” February 1997.) to the following data, in order:

   the associated data A,

   the initialization vector IV,

   the ciphertext E computed in the previous step, and

   the octet string AL defined above.

   The string MAC_KEY is used as the MAC key. We denote the output of the MAC computed in this step as M. The first T_LEN bits of M are used as T.
6. The Ciphertext E and the Authentication Tag T are returned as the outputs of the authenticated encryption.

The encryption process can be illustrated as follows. Here K, P, A, IV, and E denote the key, plaintext, associated data, initialization vector, and ciphertext, respectively.

MAC_KEY = initial MAC_KEY_LEN bytes of K,

ENC_KEY = final ENC_KEY_LEN bytes of K,

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

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

T = initial T_LEN bytes of M.

4.8.2.2.  AES_CBC_HMAC_SHA2 Decryption

The authenticated decryption operation has four inputs: K, A, E, and T as defined above. It has only a single output, either a plaintext value P or a special symbol FAIL that indicates that the inputs are not authentic. The authenticated decryption algorithm is as follows, or uses an equivalent set of steps:

1. The secondary keys MAC_KEY and ENC_KEY are generated from the input key K as in Step 1 of Section 4.8.2.1 (AES_CBC_HMAC_SHA2 Encryption).
2. The integrity and authenticity of A and E are checked by computing an HMAC with the inputs as in Step 5 of Section 4.8.2.1 (AES_CBC_HMAC_SHA2 Encryption). The value T, from the previous step, is compared to the first MAC_KEY length bits of the HMAC output. If those values are identical, then A and E are considered valid, and processing is continued. Otherwise, all of the data used in the MAC validation are discarded, and the AEAD decryption operation returns an indication that it failed, and the operation halts. (But see Section 10 of [JWE] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.) for security considerations on thwarting timing attacks.)
3. The value E is decrypted and the PKCS #5 padding is removed. The value IV is used as the initialization vector. The value ENC_KEY is used as the decryption key.
4. The plaintext value is returned.

4.8.3.  AES_128_CBC_HMAC_SHA_256

This algorithm is a concrete instantiation of the generic AES_CBC_HMAC_SHA2 algorithm above. It uses the HMAC message authentication code [RFC2104] (Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” February 1997.) with the SHA-256 hash function [SHS] (National Institute of Standards and Technology, “Secure Hash Standard (SHS),” October 2008.) to provide message authentication, with the HMAC output truncated to 128 bits, corresponding to the HMAC-SHA-256-128 algorithm defined in [RFC4868] (Kelly, S. and S. Frankel, “Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec,” May 2007.). For encryption, it uses AES in the cipher block chaining (CBC) mode of operation as defined in Section 6.2 of [NIST.800‑38A] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation,” December 2001.), 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.

4.8.4.  AES_256_CBC_HMAC_SHA_512

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

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

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

ENC_KEY_LEN is 32 octets.

MAC_KEY_LEN is 32 octets.

The length of the input key K is 64 octets.

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

4.8.5.  Plaintext Encryption with AES_CBC_HMAC_SHA2

The algorithm value A128CBC-HS256 is used as the alg value when using AES_128_CBC_HMAC_SHA_256 with JWE. The algorithm value 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.

4.9.  Plaintext Encryption with AES GCM

This section defines the specifics of encrypting the JWE Plaintext with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [AES] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.) [NIST.800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.) 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 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] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.).

4.10.  Additional Encryption Algorithms and Parameters

Additional algorithms MAY be used to protect JWEs with corresponding alg (algorithm) and enc (encryption method) header parameter values being defined to refer to them. New alg and enc header parameter values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry Section 6.1 (JSON Web Signature and Encryption Algorithms Registry) or be a value that contains a Collision Resistant Namespace. In particular, it is permissible to use the algorithm identifiers defined in XML Encryption (Eastlake, D. and J. Reagle, “XML Encryption Syntax and Processing,” December 2002.) [W3C.REC‑xmlenc‑core‑20021210], XML Encryption 1.1 (Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, “XML Encryption Syntax and Processing Version 1.1,” March 2012.) [W3C.CR‑xmlenc‑core1‑20120313], and related specifications as alg and enc values.

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

Likewise, additional reserved Header Parameter Names can be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.). 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.

5.  Cryptographic Algorithms for JWK

A JSON Web Key (JWK) [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.) is a JavaScript Object Notation (JSON) [RFC4627] (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) 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.

5.1.  "kty" (Key Type) Parameter Values for JWK

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

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.

5.2.  JWK Parameters for Elliptic Curve Keys

JWKs can represent Elliptic Curve [DSS] (National Institute of Standards and Technology, “Digital Signature Standard (DSS),” June 2009.) keys. In this case, the kty member value MUST be EC.

5.2.1.  JWK Parameters for Elliptic Curve Public Keys

These members MUST be present for Elliptic Curve public keys:

5.2.1.1.  "crv" (Curve) Parameter

The crv (curve) member identifies the cryptographic curve used with the key. Curve values from [DSS] (National Institute of Standards and Technology, “Digital Signature Standard (DSS),” June 2009.) used by this specification are:

• P-256
• P-384
• P-521

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

5.2.1.2.  "x" (X Coordinate) Parameter

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

5.2.1.3.  "y" (Y Coordinate) Parameter

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

5.2.2.  JWK Parameters for Elliptic Curve Private Keys

In addition to the members used to represent Elliptic Curve public keys, the following member MUST be present to represent Elliptic Curve private keys:

5.2.2.1.  "d" (ECC Private Key) Parameter

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

5.3.  JWK Parameters for RSA Keys

JWKs can represent RSA [RFC3447] (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.) keys. In this case, the kty member value MUST be RSA.

5.3.1.  JWK Parameters for RSA Public Keys

These members MUST be present for RSA public keys:

5.3.1.1.  "n" (Modulus) Parameter

The n (modulus) member contains the modulus value for the RSA public key. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence. The array representation MUST NOT be shortened to omit any leading zero octets. For instance, when representing 2048 bit integers, the octet sequence to be base64url encoded MUST contain 256 octets, including any leading zero octets.

5.3.1.2.  "e" (Exponent) Parameter

The e (exponent) member contains the exponent value for the RSA public key. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence. The array representation MUST utilize the minimum number of octets to represent the value. For instance, when representing the value 65537, the octet sequence to be base64url encoded MUST consist of the three octets [1, 0, 1].

5.3.2.  JWK Parameters for RSA Private Keys

In addition to the members used to represent RSA public keys, the following members are used to represent RSA private keys. All are REQUIRED for RSA private keys except for oth, which is sometimes REQUIRED and sometimes MUST NOT be present, as described below.

5.3.2.1.  "d" (Private Exponent) Parameter

The d (private exponent) member contains the private exponent value for the RSA private key. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence. The array representation MUST NOT be shortened to omit any leading zero octets. For instance, when representing 2048 bit integers, the octet sequence to be base64url encoded MUST contain 256 octets, including any leading zero octets.

5.3.2.2.  "p" (First Prime Factor) Parameter

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

5.3.2.3.  "q" (Second Prime Factor) Parameter

The q (second prime factor) member contains the second prime factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.

5.3.2.4.  "dp" (First Factor CRT Exponent) Parameter

The dp (first factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the first factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.

5.3.2.5.  "dq" (Second Factor CRT Exponent) Parameter

The dq (second factor CRT exponent) member contains the Chinese Remainder Theorem (CRT) exponent of the second factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.

5.3.2.6.  "qi" (First CRT Coefficient) Parameter

The dp (first CRT coefficient) member contains the Chinese Remainder Theorem (CRT) coefficient of the second factor, a positive integer. It is represented as the base64url encoding of the value's unsigned big endian representation as an octet sequence.

5.3.2.7.  "oth" (Other Primes Info) Parameter

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

5.3.2.7.1.  "r" (Prime Factor)

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

5.3.2.7.2.  "d" (Factor CRT Exponent)

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

5.3.2.7.3.  "t" (Factor CRT Coefficient)

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

5.3.3.  JWK Parameters for Symmetric Keys

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):

5.3.3.1.  "k" (Key Value) Parameter

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.

5.4.  Additional Key Types and Parameters

Keys using additional key types can be represented using JWK data structures with corresponding kty (key type) parameter values being defined to refer to them. New kty parameter values SHOULD either be registered in the IANA JSON Web Key Types registry Section 6.2 (JSON Web Key Types Registry) 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] (Jones, M., “JSON Web Key (JWK),” May 2013.) or be a value that contains a Collision Resistant Namespace.

6.  IANA Considerations

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

Values are registered with a Specification Required [RFC5226] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” May 2008.) 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.

6.1.  JSON Web Signature and Encryption Algorithms Registry

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

6.1.1.  Template

Algorithm Name:

The name requested (e.g., "example"). This name is case sensitive. Names that match other registered names in a case insensitive manner SHOULD NOT be accepted.

Algorithm Usage Location(s):

The algorithm usage, which must be one or more of the values alg or enc.

Implementation Requirements:

The algorithm implementation requirements, which must be one the words REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED. Optionally, the word can be followed by a "+" or "-". The use of "+" indicates that the requirement strength is likely to be increased in a future version of the specification. The use of "-" indicates that the requirement strength is likely to be decreased in a future version of the specification.

Change Controller:

For Standards Track RFCs, state "IETF". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.

Specification Document(s):

Reference to the document(s) that specify the parameter, preferably including URI(s) that can be used to retrieve copies of the document(s). An indication of the relevant sections may also be included but is not required.

6.1.2.  Initial Registry Contents

• Algorithm Name: HS256
• Algorithm Usage Location(s): alg
• Implementation Requirements: REQUIRED
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: HS384
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: HS512
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: RS256
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: RS384
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: RS512
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: ES256
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED+
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: ES384
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: ES512
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: PS256
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: PS512
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: none
• Algorithm Usage Location(s): alg
• Implementation Requirements: REQUIRED
• Change Controller: IETF
• Specification Document(s): Section 3.1 ("alg" (Algorithm) Header Parameter Values for JWS) of [[ this document ]]

• Algorithm Name: RSA1_5
• Algorithm Usage Location(s): alg
• Implementation Requirements: REQUIRED
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: RSA-OAEP
• Algorithm Usage Location(s): alg
• Implementation Requirements: OPTIONAL
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: A128KW
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: A256KW
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: dir
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: ECDH-ES
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED+
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: ECDH-ES+A128KW
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: ECDH-ES+A256KW
• Algorithm Usage Location(s): alg
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.1 ("alg" (Algorithm) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: A128CBC-HS256
• Algorithm Usage Location(s): enc
• Implementation Requirements: REQUIRED
• Change Controller: IETF
• Specification Document(s): Section 4.2 ("enc" (Encryption Method) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: A256CBC-HS512
• Algorithm Usage Location(s): enc
• Implementation Requirements: REQUIRED
• Change Controller: IETF
• Specification Document(s): Section 4.2 ("enc" (Encryption Method) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: A128GCM
• Algorithm Usage Location(s): enc
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.2 ("enc" (Encryption Method) Header Parameter Values for JWE) of [[ this document ]]

• Algorithm Name: A256GCM
• Algorithm Usage Location(s): enc
• Implementation Requirements: RECOMMENDED
• Change Controller: IETF
• Specification Document(s): Section 4.2 ("enc" (Encryption Method) Header Parameter Values for JWE) of [[ this document ]]

6.2.  JSON Web Key Types Registry

This specification establishes the IANA JSON Web Key Types registry for values of the JWK kty (key type) parameter. The registry records the kty value and a reference to the specification that defines it. This specification registers the values defined in Section 5.1 ("kty" (Key Type) Parameter Values for JWK).

6.2.1.  Registration Template

"kty" Parameter Value:

The name requested (e.g., "example"). This name is case sensitive. Names that match other registered names in a case insensitive manner SHOULD NOT be accepted.

Change Controller:

For Standards Track RFCs, state "IETF". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.

Implementation Requirements:

The algorithm implementation requirements, which must be one the words REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED. Optionally, the word can be followed by a "+" or "-". The use of "+" indicates that the requirement strength is likely to be increased in a future version of the specification. The use of "-" indicates that the requirement strength is likely to be decreased in a future version of the specification.

Specification Document(s):

Reference to the document(s) that specify the parameter, preferably including URI(s) that can be used to retrieve copies of the document(s). An indication of the relevant sections may also be included but is not required.

6.2.2.  Initial Registry Contents

• "kty" Parameter Value: EC
• Implementation Requirements: RECOMMENDED+
• Change Controller: IETF
• Specification Document(s): Section 5.1 ("kty" (Key Type) Parameter Values for JWK) of [[ this document ]]

• "kty" Parameter Value: RSA
• Implementation Requirements: REQUIRED
• Change Controller: IETF
• Specification Document(s): Section 5.1 ("kty" (Key Type) Parameter Values for JWK) of [[ this document ]]

• "kty" Parameter Value: oct
• Implementation Requirements: RECOMMENDED+
• Change Controller: IETF
• Specification Document(s): Section 5.1 ("kty" (Key Type) Parameter Values for JWK) of [[ this document ]]

6.3.  JSON Web Key Parameters Registration

This specification registers the parameter names defined in Sections 5.2 (JWK Parameters for Elliptic Curve Keys), 5.3 (JWK Parameters for RSA Keys), and 5.3.3 (JWK Parameters for Symmetric Keys) in the IANA JSON Web Key Parameters registry [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.).

6.3.1.  Registry Contents

• Parameter Name: crv
• Parameter Information Class: Public
• Change Controller: IETF
• Specification Document(s): Section 5.2.1.1 ("crv" (Curve) Parameter) of [[ this document ]]

• Parameter Name: x
• Parameter Information Class: Public
• Change Controller: IETF
• Specification Document(s): Section 5.2.1.2 ("x" (X Coordinate) Parameter) of [[ this document ]]

• Parameter Name: y
• Parameter Information Class: Public
• Change Controller: IETF
• Specification Document(s): Section 5.2.1.3 ("y" (Y Coordinate) Parameter) of [[ this document ]]

• Parameter Name: d
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.2.2.1 ("d" (ECC Private Key) Parameter) of [[ this document ]]

• Parameter Name: n
• Parameter Information Class: Public
• Change Controller: IETF
• Specification Document(s): Section 5.3.1.1 ("n" (Modulus) Parameter) of [[ this document ]]

• Parameter Name: e
• Parameter Information Class: Public
• Change Controller: IETF
• Specification Document(s): Section 5.3.1.2 ("e" (Exponent) Parameter) of [[ this document ]]

• Parameter Name: d
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.1 ("d" (Private Exponent) Parameter) of [[ this document ]]

• Parameter Name: p
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.2 ("p" (First Prime Factor) Parameter) of [[ this document ]]

• Parameter Name: q
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.3 ("q" (Second Prime Factor) Parameter) of [[ this document ]]

• Parameter Name: dp
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.4 ("dp" (First Factor CRT Exponent) Parameter) of [[ this document ]]

• Parameter Name: dq
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.5 ("dq" (Second Factor CRT Exponent) Parameter) of [[ this document ]]

• Parameter Name: qi
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.6 ("qi" (First CRT Coefficient) Parameter) of [[ this document ]]

• Parameter Name: oth
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.2.7 ("oth" (Other Primes Info) Parameter) of [[ this document ]]

• Parameter Name: k
• Parameter Information Class: Private
• Change Controller: IETF
• Specification Document(s): Section 5.3.3.1 ("k" (Key Value) Parameter) of [[ this document ]]

7.  Security Considerations

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

The security considerations in [AES] (National Institute of Standards and Technology (NIST), “Advanced Encryption Standard (AES),” November 2001.), [DSS] (National Institute of Standards and Technology, “Digital Signature Standard (DSS),” June 2009.), [JWE] (Jones, M., Rescorla, E., and J. Hildebrand, “JSON Web Encryption (JWE),” May 2013.), [JWK] (Jones, M., “JSON Web Key (JWK),” May 2013.), [JWS] (Jones, M., Bradley, J., and N. Sakimura, “JSON Web Signature (JWS),” May 2013.), [NIST.800‑38A] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation,” December 2001.), [NIST.800‑38D] (National Institute of Standards and Technology (NIST), “Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC,” December 2001.), [NIST.800‑56A] (National Institute of Standards and Technology (NIST), “Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised),” March 2007.), [RFC2104] (Krawczyk, H., Bellare, M., and R. Canetti, “HMAC: Keyed-Hashing for Message Authentication,” February 1997.), [RFC3394] (Schaad, J. and R. Housley, “Advanced Encryption Standard (AES) Key Wrap Algorithm,” September 2002.), [RFC3447] (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.), [RFC5116] (McGrew, D., “An Interface and Algorithms for Authenticated Encryption,” January 2008.), [RFC6090] (McGrew, D., Igoe, K., and M. Salter, “Fundamental Elliptic Curve Cryptography Algorithms,” February 2011.), and [SHS] (National Institute of Standards and Technology, “Secure Hash Standard (SHS),” October 2008.) 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] (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.) 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] (Jonsson, J. and B. Kaliski, “Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1,” February 2003.). 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.

8.  References

8.1. Normative References

8.2. Informative References

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

This appendix contains a table cross-referencing the digital signature and MAC alg (algorithm) values used in this specification with the equivalent identifiers used by other standards and software packages. See XML DSIG (Eastlake, D., Reagle, J., and D. Solo, “(Extensible Markup Language) XML-Signature Syntax and Processing,” March 2002.) [RFC3275], XML DSIG 2.0 (Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P., Hirsch, F., Cantor, S., and T. Roessler, “XML Signature Syntax and Processing Version 2.0,” January 2012.) [W3C.CR‑xmldsig‑core2‑20120124], and Java Cryptography Architecture (Oracle, “Java Cryptography Architecture,” 2011.) [JCA] for more information about the names defined by those documents.

Appendix B.  Encryption Algorithm Identifier Cross-Reference

This appendix contains a table cross-referencing the alg (algorithm) and enc (encryption method) values used in this specification with the equivalent identifiers used by other standards and software packages. See XML Encryption (Eastlake, D. and J. Reagle, “XML Encryption Syntax and Processing,” December 2002.) [W3C.REC‑xmlenc‑core‑20021210], XML Encryption 1.1 (Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, “XML Encryption Syntax and Processing Version 1.1,” March 2012.) [W3C.CR‑xmlenc‑core1‑20120313], and Java Cryptography Architecture (Oracle, “Java Cryptography Architecture,” 2011.) [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.

Appendix C.  Test Cases for AES_CBC_HMAC_SHA2 Algorithms

The following test cases can be used to validate implementations of the AES_CBC_HMAC_SHA2 algorithms defined in Section 4.8 (AES_CBC_HMAC_SHA2 Algorithms). 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] (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.), demonstrating that the cryptographic computations performed are the same.

The variable names are those defined in Section 4.8 (AES_CBC_HMAC_SHA2 Algorithms). All values are hexadecimal.

C.1.  Test Cases for AES_128_CBC_HMAC_SHA_256

AES_128_CBC_HMAC_SHA_256

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

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

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

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

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

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

  AL =      00 00 00 00 00 00 01 50

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

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

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

C.2.  Test Cases for AES_256_CBC_HMAC_SHA_512

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

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

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

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

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

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

  AL =      00 00 00 00 00 00 01 50

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

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

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

Appendix D.  Acknowledgements

Solutions for signing and encrypting JSON content were previously explored by Magic Signatures (Panzer (editor), J., Laurie, B., and D. Balfanz, “Magic Signatures,” January 2011.) [MagicSignatures], JSON Simple Sign (Bradley, J. and N. Sakimura (editor), “JSON Simple Sign,” September 2010.) [JSS], Canvas Applications (Facebook, “Canvas Applications,” 2010.) [CanvasApp], JSON Simple Encryption (Bradley, J. and N. Sakimura (editor), “JSON Simple Encryption,” September 2010.) [JSE], and JavaScript Message Security Format (Rescorla, E. and J. Hildebrand, “JavaScript Message Security Format,” March 2011.) [I‑D.rescorla‑jsms], all of which influenced this draft.

The Authenticated Encryption with AES-CBC and HMAC-SHA (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.) [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] (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.) 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.

Appendix E.  Document History

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

-11

• Removed the Encrypted Key value from the AAD computation since it is already effectively integrity protected by the encryption process. The AAD value now only contains the representation of the JWE Encrypted Header.
• Removed apv (agreement PartyVInfo) since it is no longer used.
• Added more information about the use of PartyUInfo during key agreement.
• Use the keydatalen as the SuppPubInfo value for the Concat KDF when doing key agreement, as RFC 2631 does.
• Added algorithm identifiers for RSASSA-PSS with SHA-256 and SHA-512.
• Added a Parameter Information Class value to the JSON Web Key Parameters registry, which registers whether the parameter conveys public or private information.

-10

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

-09

• Expanded the scope of the JWK parameters to include private and symmetric key representations, as specified by draft-jones-jose-json-private-and-symmetric-key-00.
• Changed term "JWS Secured Input" to "JWS Signing Input".
• Changed from using the term "byte" to "octet" when referring to 8 bit values.
• Specified that AES Key Wrap uses the default initial value specified in Section 2.2.3.1 of RFC 3394. This addressed issue #19.
• Added Key Management Mode definitions to terminology section and used the defined terms to provide clearer key management instructions. This addressed issue #5.
• Replaced A128CBC+HS256 and A256CBC+HS512 with A128CBC-HS256 and A256CBC-HS512. The new algorithms perform the same cryptographic computations as [I‑D.mcgrew‑aead‑aes‑cbc‑hmac‑sha2] (McGrew, D. and K. Paterson, “Authenticated Encryption with AES-CBC and HMAC-SHA,” October 2012.), but with the Initialization Vector and Authentication Tag values remaining separate from the Ciphertext value in the output representation. Also deleted the header parameters epu (encryption PartyUInfo) and epv (encryption PartyVInfo), since they are no longer used.
• Changed from using the term "Integrity Value" to "Authentication Tag".

-08

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

-07

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

-06

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

-05

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

-04

• Added text requiring that any leading zero bytes be retained in base64url encoded key value representations for fixed-length values.
• Added this language to Registration Templates: "This name is case sensitive. Names that match other registered names in a case insensitive manner SHOULD NOT be accepted."
• Described additional open issues.
• Applied editorial suggestions.

-03

• Always use a 128 bit "authentication tag" size for AES GCM, regardless of the key size.
• Specified that use of a 128 bit IV is REQUIRED with AES CBC. It was previously RECOMMENDED.
• Removed key size language for ECDSA algorithms, since the key size is implied by the algorithm being used.
• Stated that the int key size must be the same as the hash output size (and not larger, as was previously allowed) so that its size is defined for key generation purposes.
• Added the kdf (key derivation function) header parameter to provide crypto agility for key derivation. The default KDF remains the Concat KDF with the SHA-256 digest function.
• Clarified that the mod and exp values are unsigned.
• Added Implementation Requirements columns to algorithm tables and Implementation Requirements entries to algorithm registries.
• Changed AES Key Wrap to RECOMMENDED.
• Moved registries JSON Web Signature and Encryption Header Parameters and JSON Web Signature and Encryption Type Values to the JWS specification.
• Moved JSON Web Key Parameters registry to the JWK specification.
• Changed registration requirements from RFC Required to Specification Required with Expert Review.
• Added Registration Template sections for defined registries.
• Added Registry Contents sections to populate registry values.
• No longer say "the UTF-8 representation of the JWS Secured Input (which is the same as the ASCII representation)". Just call it "the ASCII representation of the JWS Secured Input".
• Added "Collision Resistant Namespace" to the terminology section.
• Numerous editorial improvements.

-02

• For AES GCM, use the "additional authenticated data" parameter to provide integrity for the header, encrypted key, and ciphertext and use the resulting "authentication tag" value as the JWE Authentication Tag.
• Defined minimum required key sizes for algorithms without specified key sizes.
• Defined KDF output key sizes.
• Specified the use of PKCS #5 padding with AES CBC.
• Generalized text to allow key agreement to be employed as an alternative to key wrapping or key encryption.
• Clarified that ECDH-ES is a key agreement algorithm.
• Required implementation of AES-128-KW and AES-256-KW.
• Removed the use of A128GCM and A256GCM for key wrapping.
• Removed A512KW since it turns out that it's not a standard algorithm.
• Clarified the relationship between typ header parameter values and MIME types.
• Generalized language to refer to Message Authentication Codes (MACs) rather than Hash-based Message Authentication Codes (HMACs) unless in a context specific to HMAC algorithms.
• Established registries: JSON Web Signature and Encryption Header Parameters, JSON Web Signature and Encryption Algorithms, JSON Web Signature and Encryption "typ" Values, JSON Web Key Parameters, and JSON Web Key Algorithm Families.
• Moved algorithm-specific definitions from JWK to JWA.
• Reformatted to give each member definition its own section heading.

-01

• Moved definition of "alg":"none" for JWSs here from the JWT specification since this functionality is likely to be useful in more contexts that just for JWTs.
• Added Advanced Encryption Standard (AES) Key Wrap Algorithm using 512 bit keys (A512KW).
• Added text "Alternatively, the Encoded JWS Signature MAY be base64url decoded to produce the JWS Signature and this value can be compared with the computed HMAC value, as this comparison produces the same result as comparing the encoded values".
• Corrected the Magic Signatures reference.
• Made other editorial improvements suggested by JOSE working group participants.

-00

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

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