JOSE Working Group M.B. Jones
Internet-Draft Microsoft
Intended status: Standards Track September 04, 2013
Expires: March 08, 2014

JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-15

Abstract

The JSON Web Algorithms (JWA) specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK) specifications. It defines several IANA registries for these identifiers.

Status of This Memo

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This Internet-Draft will expire on March 08, 2014.

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Table of Contents

1. Introduction

The JSON Web Algorithms (JWA) specification registers cryptographic algorithms and identifiers to be used with the JSON Web Signature (JWS) [JWS], JSON Web Encryption (JWE) [JWE], and JSON Web Key (JWK) [JWK] specifications. It defines several IANA registries for these identifiers. All these specifications utilize JavaScript Object Notation (JSON) [RFC4627] based data structures. This specification also describes the semantics and operations that are specific to these algorithms and key types.

Registering the algorithms and identifiers here, rather than in the JWS, JWE, and JWK specifications, is intended to allow them to remain unchanged in the face of changes in the set of Required, Recommended, Optional, and Deprecated algorithms over time. This also allows changes to the JWS, JWE, and JWK specifications without changing this document.

Names defined by this specification are short because a core goal is for the resulting representations to be compact.

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].

2. Terminology

2.1. Terms Incorporated from the JWS Specification

These terms defined by the JSON Web Signature (JWS) [JWS] 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] encoded text string representing a JSON object; the syntax of JSON objects is defined in Section 2.2 of [RFC4627].
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
Base64 encoding using the URL- and filename-safe character set defined in Section 5 of RFC 4648 [RFC4648], with all trailing '=' characters omitted (as permitted by Section 3.2). (See Appendix C of [JWS] for notes on implementing base64url encoding without padding.)
Encoded JWS Header
Base64url encoding of the 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. Examples of Collision Resistant Namespaces include: Domain Names, Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670 Recommendation series, and Universally Unique IDentifiers (UUIDs) [RFC4122]. When using an administratively delegated namespace, the definer of a name needs to take reasonable precautions to ensure they are in control of the portion of the namespace they use to define the name.

2.2. Terms Incorporated from the JWE Specification

These terms defined by the JSON Web Encryption (JWE) [JWE] 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] 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.

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

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

alg Parameter Value Digital Signature or MAC Algorithm Implementation Requirements
HS256 HMAC using SHA-256 hash algorithm Required
HS384 HMAC using SHA-384 hash algorithm Optional
HS512 HMAC using SHA-512 hash algorithm Optional
RS256 RSASSA-PKCS-v1_5 using SHA-256 hash algorithm Recommended
RS384 RSASSA-PKCS-v1_5 using SHA-384 hash algorithm Optional
RS512 RSASSA-PKCS-v1_5 using SHA-512 hash algorithm Optional
ES256 ECDSA using P-256 curve and SHA-256 hash algorithm Recommended+
ES384 ECDSA using P-384 curve and SHA-384 hash algorithm Optional
ES512 ECDSA using P-521 curve and SHA-512 hash algorithm Optional
PS256 RSASSA-PSS using SHA-256 hash algorithm and MGF1 mask generation function with SHA-256 Optional
PS384 RSASSA-PSS using SHA-384 hash algorithm and MGF1 mask generation function with SHA-384 Optional
PS512 RSASSA-PSS using SHA-512 hash algorithm and MGF1 mask generation function with SHA-512 Optional
none No digital signature or MAC value included Required

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

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

3.2. HMAC with SHA-2 Functions

Hash-based Message Authentication Codes (HMACs) enable one to use a secret plus a cryptographic hash function to generate a Message Authentication Code (MAC). This can be used to demonstrate that whoever generated the MAC was in possession of the MAC key.

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

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

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

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

Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is performed identically to the procedure for HMAC SHA-256 - just using the corresponding hash algorithms with correspondingly larger minimum key sizes and result values: 384 bits each for HMAC SHA-384 and 512 bits each for HMAC SHA-512.

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

3.3. Digital Signature with RSASSA-PKCS1-V1_5

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

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

The RSASSA-PKCS1-V1_5 SHA-256 digital signature is generated as follows:

  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 validation has failed.
  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.

Signing with the RSASSA-PKCS1-V1_5 SHA-384 and RSASSA-PKCS1-V1_5 SHA-512 algorithms is performed identically to the procedure for RSASSA-PKCS1-V1_5 SHA-256 - just using the corresponding hash algorithms instead of SHA-256.

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

3.4. Digital Signature with ECDSA

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

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

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

  1. Generate a digital signature of the 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 validation has failed.
  2. The output of the base64url decoding MUST be a 64 octet sequence. If decoding does not result in a 64 octet sequence, the validation has failed.
  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.

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

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

3.5. Digital Signature with RSASSA-PSS

This section defines the use of the RSASSA-PSS digital signature algorithm as defined in Section 8.1 of RFC 3447 [RFC3447] with the MGF1 mask generation function, always using the same hash function for both the RSASSA-PSS hash function and the MGF1 hash function. Use of SHA-256, SHA-384, and SHA-512 as these hash functions is defined. The size of the salt value is the same size as the hash function output. All other algorithm parameters use the defaults specified in Section A.2.3 of RFC 3447. The alg (algorithm) header parameter values PS256, PS384, and PS512 are used in the JWS Header to indicate that the Encoded JWS Signature contains a base64url encoded RSASSA-PSS digital signature using the respective hash function in both roles.

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

The RSASSA-PSS SHA-256 digital signature is generated as follows:

  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 validation has failed.
  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.

Signing with the RSASSA-PSS SHA-384 and RSASSA-PSS SHA-512 algorithms is performed identically to the procedure for RSASSA-PSS SHA-256 - just using the alternative hash algorithm in both roles.

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.

4. Cryptographic Algorithms for JWE

JWE uses cryptographic algorithms to encrypt the Content Encryption Key (CEK) and the Plaintext.

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.

alg Parameter Value Key Management Algorithm Additional Header Parameters Implementation Requirements
RSA1_5 RSAES-PKCS1-V1_5 [RFC3447] (none) Required
RSA-OAEP RSAES using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with the default parameters specified by RFC 3447 in Section A.2.1 (none) Optional
A128KW Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using the default initial value specified in Section 2.2.3.1 and using 128 bit keys (none) Recommended
A192KW AES Key Wrap Algorithm using the default initial value specified in Section 2.2.3.1 and using 192 bit keys (none) Optional
A256KW AES Key Wrap Algorithm using the default initial value specified in Section 2.2.3.1 and using 256 bit keys (none) Recommended
dir Direct use of a shared symmetric key as the Content Encryption Key (CEK) for the content encryption step (rather than using the symmetric key to wrap the CEK) (none) Recommended
ECDH-ES Elliptic Curve Diffie-Hellman Ephemeral Static [RFC6090] key agreement using the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A], with the agreed-upon key being used directly as the Content Encryption Key (CEK) (rather than being used to wrap the CEK), as specified in Section 4.7 epk, apu, apv Recommended+
ECDH-ES+A128KW Elliptic Curve Diffie-Hellman Ephemeral Static key agreement per ECDH-ES and Section 4.7, where the agreed-upon key is used to wrap the Content Encryption Key (CEK) with the A128KW function (rather than being used directly as the CEK) epk, apu, apv Recommended
ECDH-ES+A192KW Elliptic Curve Diffie-Hellman Ephemeral Static key agreement, where the agreed-upon key is used to wrap the Content Encryption Key (CEK) with the A192KW function (rather than being used directly as the CEK) epk, apu, apv Optional
ECDH-ES+A256KW Elliptic Curve Diffie-Hellman Ephemeral Static key agreement, where the agreed-upon key is used to wrap the Content Encryption Key (CEK) with the A256KW function (rather than being used directly as the CEK) epk, apu, apv Recommended
A128GCMKW AES in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 bit keys iv, tag Optional
A192GCMKW AES GCM using 192 bit keys iv, tag Optional
A256GCMKW AES GCM using 256 bit keys iv, tag Optional
PBES2-HS256+A128KW PBES2 [RFC2898] with HMAC SHA-256 as the PRF and AES Key Wrap [RFC3394] using 128 bit keys for the encryption scheme p2s, p2c Optional
PBES2-HS384+A192KW PBES2 with HMAC SHA-256 as the PRF and AES Key Wrap using 192 bit keys for the encryption scheme p2s, p2c Optional
PBES2-HS512+A256KW PBES2 with HMAC SHA-256 as the PRF and AES Key Wrap using 256 bit keys for the encryption scheme p2s, p2c Optional

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

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

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

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

enc Parameter Value Content Encryption Algorithm Additional Header Parameters Implementation Requirements
A128CBC-HS256 The AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 4.10.3. This algorithm uses a 256 bit key. (none) Required
A192CBC-HS384 The AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm, as defined in Section 4.10.4. This algorithm uses a 384 bit key. (none) Optional
A256CBC-HS512 The AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm, as defined in Section 4.10.5. This algorithm uses a 512 bit key. (none) Required
A128GCM AES in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128 bit keys (none) Recommended
A192GCM AES GCM using 192 bit keys (none) Optional
A256GCM AES GCM using 256 bit keys (none) Recommended

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

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

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]. The alg header parameter value RSA1_5 is used in this case.

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

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

4.4. Key Encryption with RSAES OAEP

This section defines the specifics of encrypting a JWE 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].

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] using the default initial value specified in Section 2.2.3.1 using 128, 192, or 256 bit keys. The alg header parameter values A128KW, A192KW, or A256KW are respectively used in this case.

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

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], in combination with the Concat KDF, as defined in Section 5.8.1 of [NIST.800-56A]. The key agreement result can be used in one of two ways: alg header parameter value ECDH-ES is used in the Direct Key Agreement mode and the values ECDH-ES+A128KW, ECDH-ES+A192KW, or ECDH-ES+A256KW are used in the Key Agreement with Key Wrapping mode.

  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 the A128KW, A192KW, or A256KW algorithms, in the Key Agreement with Key Wrapping mode.

The

In the Direct Key Agreement case, the output of the Concat KDF MUST be a key of the same length as that used by the enc algorithm; in this case, the empty octet sequence is used as the JWE Encrypted Key value. In the Key Agreement with Key Wrapping case, the output of the Concat KDF MUST be a key of the length needed for the specified key wrapping algorithm, one of 128, 192, or 256 bits respectively.

A new ephemeral public key value MUST be generated for each key agreement operation.

4.7.1. Header Parameters Used for ECDH Key Agreement

The following Header Parameter Names are reserved and are used for key agreement as defined below.

4.7.1.1. "epk" (Ephemeral Public Key) Header Parameter

The epk (ephemeral public key) value created by the originator for the use in key agreement algorithms. This key is represented as a JSON Web Key [JWK] public key value. It MUST contain only public key parameters and SHOULD contain only the minimum JWK parameters necessary to represent the key; other JWK parameters included can be checked for consistency and honored or can be ignored. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

4.7.1.2. "apu" (Agreement PartyUInfo) Header Parameter

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

4.7.1.3. "apv" (Agreement PartyVInfo) Header Parameter

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

4.7.2. Key Derivation for ECDH Key Agreement

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

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

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

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

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

4.8. Key Encryption with AES GCM

This section defines the specifics of encrypting a JWE Content Encryption Key (CEK) with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128, 192, or 256 bit keys. The alg header parameter values A128GCMKW, A192GCMKW, or A256GCMKW are respectively used in this case.

Use of an Initialization Vector of size 96 bits is REQUIRED with this algorithm. The Initialization Vector is represented in base64url encoded form as the iv (initialization vector) header parameter value.

The Additional Authenticated Data value used is the empty octet string.

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

The JWE Encrypted Key value is the Ciphertext output.

The Authentication Tag output is represented in base64url encoded form as the tag (authentication tag) header parameter value.

4.8.1. Header Parameters Used for AES GCM Key Encryption

The following Header Parameters are used for AES GCM key encryption.

4.8.1.1. "iv" (Initialization Vector) Header Parameter

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

4.8.1.2. "tag" (Authentication Tag) Header Parameter

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

4.9. Key Encryption with PBES2

The PBES2-HS256+A128KW, PBES2-HS384+A192KW, and PBES2-HS512+A256KW composite algorithms are used to perform password-based encryption of a JWE CEK, by first deriving a key encryption key from a user-supplied password, then encrypting the JWE CEK using the derived key. These algorithms are PBES2 schemes as specified in Section 6.2 of [RFC2898].

These algorithms use HMAC SHA-2 algorithms as the Pseudo-Random Function (PRF) for the PBKDF2 key derivation and AES Key Wrap [RFC3394] for the encryption scheme. The salt MUST be provided as the p2s header parameter value, and MUST be base64url decoded to obtain the value. The iteration count parameter MUST be provided as the p2c header parameter value. The algorithms respectively use HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 as the PRF and use 128, 192, and 256 bit AES Key Wrap keys. Their derived-key lengths (dkLen) respectively are 16, 24, and 32 octets.

4.9.1. Header Parameters Used for PBES2 Key Encryption

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

4.9.1.1. "p2s" (PBES2 salt) Parameter

The p2s (PBES2 salt) header parameter contains the PBKDF2 salt value, encoded using base64url. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

The salt expands the possible keys that can be derived from a given password. A salt value containing 8 or more octets MUST be used. A new salt value MUST be generated randomly for every encryption operation; see [RFC4086] for considerations on generating random values.

4.9.1.2. "p2c" (PBES2 count) Parameter

The p2c (PBES2 count) header parameter contains the PBKDF2 iteration count, represented as a positive integer. This Header Parameter is REQUIRED and MUST be understood and processed by implementations when these algorithms are used.

The iteration count adds computational expense, ideally compounded by the possible range of keys introduced by the salt. A minimum iteration count of 1000 is RECOMMENDED.

4.10. AES_CBC_HMAC_SHA2 Algorithms

This section defines a family of authenticated encryption algorithms built using a composition of Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES] [NIST.800-38A] operations and HMAC [RFC2104] [SHS] operations. This algorithm family is called AES_CBC_HMAC_SHA2. It also defines three instances of this family, the first using 128 bit CBC keys and HMAC SHA-256, the second using 192 bit CBC keys and HMAC SHA-384, and the third using 256 bit CBC keys and HMAC SHA-512. Test cases for these algorithms can be found in Appendix C.

These algorithms are based upon Authenticated Encryption with AES-CBC and HMAC-SHA [I-D.mcgrew-aead-aes-cbc-hmac-sha2], performing the same cryptographic computations, but with the Initialization Vector and Authentication Tag values remaining separate, rather than being concatenated with the Ciphertext value in the output representation. This option is discussed in Appendix B of that specification. This algorithm family is a generalization of the algorithm family in [I-D.mcgrew-aead-aes-cbc-hmac-sha2], and can be used to implement those algorithms.

4.10.1. Conventions Used in Defining AES_CBC_HMAC_SHA2

We use the following notational conventions.

4.10.2. Generic AES_CBC_HMAC_SHA2 Algorithm

This section defines AES_CBC_HMAC_SHA2 in a manner that is independent of the AES CBC key size or hash function to be used. Section 4.10.2.1 and Section 4.10.2.2 define the generic encryption and decryption algorithms. Section 4.10.3 and Section 4.10.5 define instances of AES_CBC_HMAC_SHA2 that specify those details.

4.10.2.1. AES_CBC_HMAC_SHA2 Encryption

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

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

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

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

    Section 4.10.3 and Section 4.10.5). The number of octets in the input key K is the sum of MAC_KEY_LEN and ENC_KEY_LEN. When generating the secondary keys from K, MAC_KEY and ENC_KEY MUST NOT overlap. Note that the MAC key comes before the encryption key in the input key K; this is in the opposite order of the algorithm names in the identifier "AES_CBC_HMAC_SHA2".
  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] to the following data, in order:

    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.

4.10.2.2. AES_CBC_HMAC_SHA2 Decryption

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

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

4.10.3. AES_128_CBC_HMAC_SHA_256

This algorithm is a concrete instantiation of the generic AES_CBC_HMAC_SHA2 algorithm above. It uses the HMAC message authentication code [RFC2104] with the SHA-256 hash function [SHS] to provide message authentication, with the HMAC output truncated to 128 bits, corresponding to the HMAC-SHA-256-128 algorithm defined in [RFC4868]. For encryption, it uses AES in the Cipher Block Chaining (CBC) mode of operation as defined in Section 6.2 of [NIST.800-38A], with PKCS #5 padding.

The input key K is 32 octets long.

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

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

4.10.4. AES_192_CBC_HMAC_SHA_384

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

4.10.5. AES_256_CBC_HMAC_SHA_512

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

4.10.6. Plaintext Encryption with AES_CBC_HMAC_SHA2

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

4.11. Plaintext Encryption with AES GCM

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

The CEK is used as the encryption key.

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

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

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

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

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

5. Cryptographic Algorithms for JWK

A JSON Web Key (JWK) [JWK] is a JSON data structure that represents a cryptographic key. These keys can be either asymmetric or symmetric. They can hold both public and private information about the key. This section defines the parameters for keys using the algorithms specified by this document.

5.1. "kty" (Key Type) Parameter Values

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

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

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

5.2. JWK Parameters for Elliptic Curve Keys

JWKs can represent Elliptic Curve [DSS] keys. In this case, the kty member value MUST be EC.

5.2.1. JWK Parameters for Elliptic Curve Public Keys

The following 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] 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

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] keys. In this case, the kty member value MUST be RSA.

5.3.1. JWK Parameters for RSA Public Keys

The following 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. The parameter d is REQUIRED for RSA private keys. The others enable optimizations and are RECOMMENDED. If any of the others are present then all MUST be present, with the exception of oth, which MUST only be present when more than two prime factors were used.

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.

5.4. 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):

5.4.1. "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.

6. IANA Considerations

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

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

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

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

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

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. Changes of implementation requirements are only permitted on a Specification Required basis, with the new specification defining the revised implementation requirements level.

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

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, implementation requirements, and a reference to the specification that defines it.

The implementation requirements of a key type MAY be changed over time by the Designated Experts(s) as the cryptographic landscape evolves, for instance, to change the status of a key type to Deprecated, or to change the status of a key type from Optional to Recommended+ or Required. Changes of implementation requirements are only permitted on a Specification Required basis, with the new specification defining the revised implementation requirements level.

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 key type 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

This specification registers the values defined in Section 5.1.

6.3. JSON Web Key Parameters Registration

This specification registers the parameter names defined in Sections 5.2, 5.3, and 5.4 in the IANA JSON Web Key Parameters registry [JWK].

6.3.1. Registry Contents

6.4. Registration of JWE Header Parameter Names

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

6.4.1. Registry Contents

7. Security Considerations

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

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

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

Many algorithms have associated security considerations related to key lifetimes and/or the number of times that a key may be used. Those security considerations continue to apply when using those algorithms with JOSE data structures.

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

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

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

Keys used with AES GCM must follow the constraints in Section 8.3 of [NIST.800-38D], which states: "The total number of invocations of the authenticated encryption function shall not exceed 2^32, including all IV lengths and all instances of the authenticated encryption function with the given key". In accordance with this rule, AES GCM MUST NOT be used with the same key encryption key or with the same direct encryption key more than 2^32 times.

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

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

7.1. Reusing Key Material when Encrypting Keys

It is NOT RECOMMENDED to reuse the same key material (Key Encryption Key, Content Encryption Key, Initialization Vector, etc.) to encrypt multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK Set object multiple times. One suggestion for preventing re-use is to always generate a new set key material for each encryption operation, based on the considerations noted in this document as well as from [RFC4086].

7.2. Password Considerations

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

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

An ideal password is one that is as large (or larger) than the derived key length but less than the PRF's block size. Passwords larger than the PRF's block size are first hashed, which reduces an attacker's effective search space to the length of the hash algorithm (32 octets for HMAC SHA-256). It is RECOMMENDED that the password be no longer than 64 octets long for PBES2-HS512+A256KW.

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

8. Internationalization Considerations

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

9. References

9.1. Normative References

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

9.2. Informative References

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

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

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

Algorithm JWS XML DSIG JCA OID
HMAC using SHA-256 hash algorithm HS256 http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 HmacSHA256 1.2.840.113549.2.9
HMAC using SHA-384 hash algorithm HS384 http://www.w3.org/2001/04/xmldsig-more#hmac-sha384 HmacSHA384 1.2.840.113549.2.10
HMAC using SHA-512 hash algorithm HS512 http://www.w3.org/2001/04/xmldsig-more#hmac-sha512 HmacSHA512 1.2.840.113549.2.11
RSASSA-PKCS-v1_5 using SHA-256 hash algorithm RS256 http://www.w3.org/2001/04/xmldsig-more#rsa-sha256 SHA256withRSA 1.2.840.113549.1.1.11
RSASSA-PKCS-v1_5 using SHA-384 hash algorithm RS384 http://www.w3.org/2001/04/xmldsig-more#rsa-sha384 SHA384withRSA 1.2.840.113549.1.1.12
RSASSA-PKCS-v1_5 using SHA-512 hash algorithm RS512 http://www.w3.org/2001/04/xmldsig-more#rsa-sha512 SHA512withRSA 1.2.840.113549.1.1.13
ECDSA using P-256 curve and SHA-256 hash algorithm ES256 http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256 SHA256withECDSA 1.2.840.10045.4.3.2
ECDSA using P-384 curve and SHA-384 hash algorithm ES384 http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384 SHA384withECDSA 1.2.840.10045.4.3.3
ECDSA using P-521 curve and SHA-512 hash algorithm ES512 http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512 SHA512withECDSA 1.2.840.10045.4.3.4
RSASSA-PSS using SHA-256 hash algorithm and MGF1 mask generation function with SHA-256 PS256
RSASSA-PSS using SHA-384 hash algorithm and MGF1 mask generation function with SHA-384 PS384
RSASSA-PSS using SHA-512 hash algorithm and MGF1 mask generation function with SHA-512 PS512

Appendix B. Encryption Algorithm Identifier Cross-Reference

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

For the composite algorithms A128CBC-HS256, A192CBC-HS384, and A256CBC-HS512, the corresponding AES CBC algorithm identifiers are listed.

Algorithm JWE XML ENC JCA
RSAES-PKCS1-V1_5 RSA1_5 http://www.w3.org/2001/04/xmlenc#rsa-1_5 RSA/ECB/PKCS1Padding
RSAES using Optimal Asymmetric Encryption Padding (OAEP) RSA-OAEP http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p RSA/ECB/OAEPWithSHA-1AndMGF1Padding
Elliptic Curve Diffie-Hellman Ephemeral Static ECDH-ES http://www.w3.org/2009/xmlenc11#ECDH-ES
Advanced Encryption Standard (AES) Key Wrap Algorithm using 128 bit keys A128KW http://www.w3.org/2001/04/xmlenc#kw-aes128
AES Key Wrap Algorithm using 192 bit keys A192KW http://www.w3.org/2001/04/xmlenc#kw-aes192
AES Key Wrap Algorithm using 256 bit keys A256KW http://www.w3.org/2001/04/xmlenc#kw-aes256
AES in Cipher Block Chaining (CBC) mode with PKCS #5 padding using 128 bit keys A128CBC-HS256 http://www.w3.org/2001/04/xmlenc#aes128-cbc AES/CBC/PKCS5Padding
AES in CBC mode with PKCS #5 padding using 192 bit keys A192CBC-HS384 http://www.w3.org/2001/04/xmlenc#aes192-cbc AES/CBC/PKCS5Padding
AES in CBC mode with PKCS #5 padding using 256 bit keys A256CBC-HS512 http://www.w3.org/2001/04/xmlenc#aes256-cbc AES/CBC/PKCS5Padding
AES in Galois/Counter Mode (GCM) using 128 bit keys A128GCM http://www.w3.org/2009/xmlenc11#aes128-gcm AES/GCM/NoPadding
AES GCM using 192 bit keys A192GCM http://www.w3.org/2009/xmlenc11#aes192-gcm AES/GCM/NoPadding
AES GCM using 256 bit keys A256GCM http://www.w3.org/2009/xmlenc11#aes256-gcm AES/GCM/NoPadding

Appendix C. Test Cases for AES_CBC_HMAC_SHA2 Algorithms

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

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

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_192_CBC_HMAC_SHA_384

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

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

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

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

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

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

  AL =      00 00 00 00 00 00 01 50

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

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

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

C.3. Test Cases for AES_256_CBC_HMAC_SHA_512

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

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

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

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

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

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

  AL =      00 00 00 00 00 00 01 50

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

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

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

Appendix D. Example ECDH-ES Key Agreement Computation

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

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

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

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

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

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

  {"alg":"ECDH-ES",
   "enc":"A128GCM",
   "apu":"QWxpY2U",
   "apv":"Qm9i",
   "epk":
    {"kty":"EC",
     "crv":"P-256",
     "x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
     "y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps"
    }
  }

The resulting Concat KDF [NIST.800-56A] parameter values are:

Z
This is set to the ECDH-ES key agreement output. (This value is often not directly exposed by libraries, due to NIST security requirements, and only serves as an input to a KDF.) In this example, Z is the octet sequence:
[158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132, 38, 156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121, 140, 254, 144, 196].
keydatalen
This value is 128 - the number of bits in the desired output key (because A128GCM uses a 128 bit key).
AlgorithmID
This is set to the octets representing the UTF-8 string "A128GCM" - [65, 49, 50, 56, 71, 67, 77].
PartyUInfo
This is set to the octets representing the 32 bit big endian value 5 - [0, 0, 0, 5] - the number of octets in the PartyUInfo content "Alice", followed, by the octets representing the UTF-8 string "Alice" - [65, 108, 105, 99, 101].
PartyVInfo
This is set to the octets representing the 32 bit big endian value 3 - [0, 0, 0, 3] - the number of octets in the PartyUInfo content "Bob", followed, by the octets representing the UTF-8 string "Bob" - [66, 111, 98].
SuppPubInfo
This is set to the octets representing the 32 bit big endian value 128 - [0, 0, 0, 128] - the keydatalen value.
SuppPrivInfo
This is set to the empty octet sequence.

Concatenating the parameters AlgorithmID through SuppPubInfo results in an otherInfo value of:
[65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]

Concatenating the round number 1 ([0, 0, 0, 1]), Z, and the otherInfo value results in the Concat KDF round 1 hash input of:
[0, 0, 0, 1,
158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132, 38, 156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121, 140, 254, 144, 196,
65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]

The resulting derived key, which is the first 128 bits of the round 1 hash output is:
[186, 193, 41, 192, 82, 2, 254, 170, 230, 4, 76, 103, 180, 92, 49, 48]

The base64url encoded representation of this derived key is:

  usEpwFIC_qrmBExntFwxMA

Appendix E. Acknowledgements

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

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

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

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

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

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

Appendix F. Document History

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

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-11

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Author's Address

Michael B. Jones Microsoft EMail: mbj@microsoft.com URI: http://self-issued.info/