JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track March 2, 2014
Expires: September 3, 2014

JSON Web Algorithms (JWA)
draft-ietf-jose-json-web-algorithms-22

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

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on September 3, 2014.

Copyright Notice

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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) [RFC7158] 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", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in Key words for use in RFCs to Indicate Requirement Levels [RFC2119]. If these words are used without being spelled in uppercase then they are to be interpreted with their normal natural language meanings.

BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per Section 2.

UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation of STRING.

ASCII(STRING) denotes the octets of the ASCII [USASCII] representation of STRING.

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

2. Terminology

These terms defined by the JSON Web Signature (JWS) [JWS] specification are incorporated into this specification: "JSON Web Signature (JWS)", "JWS Header", "JWS Payload", "JWS Signature", "JWS Protected Header", "Base64url Encoding", and "JWS Signing Input".

These terms defined by the JSON Web Encryption (JWE) [JWE] specification are incorporated into this specification: "JSON Web Encryption (JWE)", "Authenticated Encryption", "Plaintext", "Ciphertext", "Additional Authenticated Data (AAD)", "Authentication Tag", "Content Encryption Key (CEK)", "JWE Header", "JWE Encrypted Key", "JWE Initialization Vector", "JWE Ciphertext", "JWE Authentication Tag", "JWE Protected Header", "Key Management Mode", "Key Encryption", "Key Wrapping", "Direct Key Agreement", "Key Agreement with Key Wrapping", and "Direct Encryption".

These terms defined by the JSON Web Key (JWK) [JWK] specification are incorporated into this specification: "JSON Web Key (JWK)" and "JSON Web Key Set (JWK Set)".

These terms are defined for use by this specification:

Header Parameter

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

3. Cryptographic Algorithms for Digital Signatures and MACs

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 Required
HS384 HMAC using SHA-384 Optional
HS512 HMAC using SHA-512 Optional
RS256 RSASSA-PKCS-v1_5 using SHA-256 Recommended
RS384 RSASSA-PKCS-v1_5 using SHA-384 Optional
RS512 RSASSA-PKCS-v1_5 using SHA-512 Optional
ES256 ECDSA using P-256 and SHA-256 Recommended+
ES384 ECDSA using P-384 and SHA-384 Optional
ES512 ECDSA using P-521 and SHA-512 Optional
PS256 RSASSA-PSS using SHA-256 and MGF1 with SHA-256 Optional
PS384 RSASSA-PSS using SHA-384 and MGF1 with SHA-384 Optional
PS512 RSASSA-PSS using SHA-512 and MGF1 with SHA-512 Optional
none No digital signature or MAC performed Optional

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

See Appendix A.1 for a table cross-referencing the JWS digital signature and MAC alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.

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].

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 JWS Signing Input as the "text" value, and using the shared key. The HMAC output value is the JWS Signature.

The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is an HMAC value computed using the corresponding algorithm:

alg Parameter Value MAC Algorithm
HS256 HMAC using SHA-256
HS384 HMAC using SHA-384
HS512 HMAC using SHA-512

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

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

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

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-2 [SHS] hash functions.

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

The RSASSA-PKCS1-V1_5 SHA-256 digital signature is generated as follows: Generate a digital signature of the JWS Signing Input using RSASSA-PKCS1-V1_5-SIGN and the SHA-256 hash function with the desired private key. This is the JWS Signature value.

The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is a digital signature value computed using the corresponding algorithm:

alg Parameter Value Digital Signature Algorithm
RS256 RSASSA-PKCS-v1_5 using SHA-256
RS384 RSASSA-PKCS-v1_5 using SHA-384
RS512 RSASSA-PKCS-v1_5 using SHA-512

The RSASSA-PKCS1-V1_5 SHA-256 digital signature for a JWS is validated as follows: Submit the JWS Signing Input, the JWS Signature, and the public key corresponding to the private key used by the signer to the RSASSA-PKCS1-V1_5-VERIFY algorithm using SHA-256 as the hash function.

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

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

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

  1. Generate a digital signature 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 octet sequence 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. The resulting 64 octet sequence is the JWS Signature value.

The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is a digital signature value computed using the corresponding algorithm:

alg Parameter Value Digital Signature Algorithm
ES256 ECDSA using P-256 and SHA-256
ES384 ECDSA using P-384 and SHA-384
ES512 ECDSA using P-521 and SHA-512

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

  1. The JWS Signature value MUST be a 64 octet sequence. If it is not a 64 octet sequence, the validation has failed.
  2. 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).
  3. Submit the JWS Signing Input R, S and the public key (x, y) to the ECDSA P-256 SHA-256 validator.

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

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 and SHA-2 hash functions, always using the same hash function for both the RSASSA-PSS hash function and the MGF1 hash function. The size of the salt value is the same size as the hash function output. All other algorithm parameters use the defaults specified in Section A.2.3 of RFC 3447.

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

The RSASSA-PSS SHA-256 digital signature is generated as follows: Generate a digital signature of the JWS Signing Input using RSASSA-PSS-SIGN, the SHA-256 hash function, and the MGF1 mask generation function with SHA-256 with the desired private key. This is the JWS signature value.

The following alg (algorithm) Header Parameter values are used to indicate that the JWS Signature is a digital signature value computed using the corresponding algorithm:

alg Parameter Value Digital Signature Algorithm
PS256 RSASSA-PSS using SHA-256 and MGF1 with SHA-256
PS384 RSASSA-PSS using SHA-384 and MGF1 with SHA-384
PS512 RSASSA-PSS using SHA-512 and MGF1 with SHA-512

The RSASSA-PSS SHA-256 digital signature for a JWS is validated as follows: Submit the JWS Signing Input, the JWS Signature, and the public key corresponding to the private key used by the signer to the RSASSA-PSS-VERIFY algorithm using SHA-256 as the hash function and using MGF1 as the mask generation function with SHA-256.

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

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". A Plaintext JWS MUST use the alg value none, and is formatted identically to other JWSs, but MUST use the empty octet sequence as its JWS Signature value. Receivers MUST verify that the JWS Signature value is the empty octet sequence. See Section 8.5 for security considerations associated with using this algorithm.

4. Cryptographic Algorithms for Key Management

JWE uses cryptographic algorithms to encrypt or determine the Content Encryption Key (CEK).

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 (none) Required
RSA-OAEP RSAES using OAEP with default parameters (none) Optional
A128KW AES Key Wrap with default initial value using 128 bit key (none) Recommended
A192KW AES Key Wrap with default initial value using 192 bit key (none) Optional
A256KW AES Key Wrap with default initial value using 256 bit key (none) Recommended
dir Direct use of a shared symmetric key as the CEK (none) Recommended
ECDH-ES Elliptic Curve Diffie-Hellman Ephemeral Static key agreement using Concat KDF epk, apu, apv Recommended+
ECDH-ES+A128KW ECDH-ES using Concat KDF and CEK wrapped with A128KW epk, apu, apv Recommended
ECDH-ES+A192KW ECDH-ES using Concat KDF and CEK wrapped with A192KW epk, apu, apv Optional
ECDH-ES+A256KW ECDH-ES using Concat KDF and CEK wrapped with A256KW epk, apu, apv Recommended
A128GCMKW Key wrapping with AES GCM using 128 bit key iv, tag Optional
A192GCMKW Key wrapping with AES GCM using 192 bit key iv, tag Optional
A256GCMKW Key wrapping with AES GCM using 256 bit key iv, tag Optional
PBES2-HS256+A128KW PBES2 with HMAC SHA-256 and A128KW wrapping p2s, p2c Optional
PBES2-HS384+A192KW PBES2 with HMAC SHA-384 and A192KW wrapping p2s, p2c Optional
PBES2-HS512+A256KW PBES2 with HMAC SHA-512 and A256KW wrapping p2s, p2c Optional

The 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.

See Appendix A.2 for a table cross-referencing the JWE alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.

4.2. 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 for this algorithm.

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

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

4.3. 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. (Those default parameters are using a hash function of SHA-1 and a mask generation function of MGF1 with SHA-1.) The alg Header Parameter value RSA-OAEP is used for this algorithm.

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

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

4.4. 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.

The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm and key size:

alg Parameter Value Key Management Algorithm
A128KW AES Key Wrap with default initial value using 128 bit key
A192KW AES Key Wrap with default initial value using 192 bit key
A256KW AES Key Wrap with default initial value using 256 bit key

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

4.5. 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.

Refer to the security considerations on key lifetimes in Section 8.2 and AES GCM in Section 8.4 when considering utilizing direct encryption.

4.6. 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:

  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.

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

In Direct Key Agreement mode, the output of the Concat KDF MUST be a key of the same length as that used by the enc algorithm. In this case, the empty octet sequence is used as the JWE Encrypted Key value. The alg Header Parameter value ECDH-ES is used in the Direct Key Agreement mode.

In Key Agreement with Key Wrapping mode, the output of the Concat KDF MUST be a key of the length needed for the specified key wrapping algorithm. In this case, the JWE Encrypted Key is the CEK wrapped with the agreed upon key.

The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the result of the key agreement algorithm as the key encryption key for the corresponding key wrapping algorithm:

alg Parameter Value Key Management Algorithm
ECDH-ES+A128KW ECDH-ES using Concat KDF and CEK wrapped with A128KW
ECDH-ES+A192KW ECDH-ES using Concat KDF and CEK wrapped with A192KW
ECDH-ES+A256KW ECDH-ES using Concat KDF and CEK wrapped with A256KW

4.6.1. Header Parameters Used for ECDH Key Agreement

The following Header Parameter names are used for key agreement as defined below.

4.6.1.1. "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 MUST be present and MUST be understood and processed by implementations when these algorithms are used.

4.6.1.2. "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.

4.6.1.3. "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.

4.6.2. 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

The AlgorithmID 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. In the Direct Key Agreement case, Data is set to the octets of the UTF-8 representation of the enc Header Parameter value. In the Key Agreement with Key Wrapping case, Data 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. 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. 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.

Applications need to specify how the apu and apv parameters are used for that application. The apu and apv values MUST be distinct, when used. Applications wishing to conform to [NIST.800-56A] need to provide values that meet the requirements of that document, e.g., by using values that identify the sender and recipient. Alternatively, applications MAY conduct key derivation in a manner similar to The Diffie-Hellman Key Agreement Method [RFC2631]: In that case, the apu field MAY either be omitted or represent a random 512-bit value (analogous to PartyAInfo in Ephemeral-Static mode in [RFC2631]) and the apv field SHOULD NOT be present.

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

4.7. 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].

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

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

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

The JWE Encrypted Key value is the Ciphertext output.

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

The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the corresponding algorithm and key size:

alg Parameter Value Key Management Algorithm
A128GCMKW Key wrapping with AES GCM using 128 bit key
A192GCMKW Key wrapping with AES GCM using 192 bit key
A256GCMKW Key wrapping with AES GCM using 256 bit key

4.7.1. Header Parameters Used for AES GCM Key Encryption

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

4.7.1.1. "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 MUST be present and MUST be understood and processed by implementations when these algorithms are used.

4.7.1.2. "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 MUST be present and MUST be understood and processed by implementations when these algorithms are used.

4.8. Key Encryption with PBES2

This section defines the specifies of performing password-based encryption of a JWE CEK, by first deriving a key encryption key from a user-supplied password using PBES2 schemes as specified in Section 6.2 of [RFC2898], then by encrypting the JWE CEK using the derived key.

These algorithms use HMAC SHA-2 algorithms as the Pseudo-Random Function (PRF) for the PBKDF2 key derivation and AES Key Wrap [RFC3394] for the encryption scheme. The PBES2 password input is an octet sequence; if the password to be used is represented as a text string rather than an octet sequence, the UTF-8 encoding of the text string MUST be used as the octet sequence. The salt parameter MUST be computed from the p2s (PBES2 salt input) Header Parameter value and the alg (algorithm) Header Parameter value as specified in the p2s definition below. The iteration count parameter MUST be provided as the p2c Header Parameter value. The algorithms respectively use HMAC SHA-256, HMAC SHA-384, and HMAC SHA-512 as the PRF and use 128, 192, and 256 bit AES Key Wrap keys. Their derived-key lengths respectively are 16, 24, and 32 octets.

The following alg (algorithm) Header Parameter values are used to indicate that the JWE Encrypted Key is the result of encrypting the CEK using the result of the corresponding password-based encryption algorithm as the key encryption key for the corresponding key wrapping algorithm:

alg Parameter Value Key Management Algorithm
PBES2-HS256+A128KW PBES2 with HMAC SHA-256 and A128KW wrapping
PBES2-HS384+A192KW PBES2 with HMAC SHA-384 and A192KW wrapping
PBES2-HS512+A256KW PBES2 with HMAC SHA-512 and A256KW wrapping

See Appendix C of JSON Web Key (JWK) [JWK] for an example key encryption computation using PBES2-HS256+A128KW.

4.8.1. Header Parameters Used for PBES2 Key Encryption

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

4.8.1.1. "p2s" (PBES2 salt input) Parameter

The p2s (PBES2 salt input) Header Parameter encodes a Salt Input value, which is used as part of the PBKDF2 salt value. The p2s value is BASE64URL(Salt Input). This Header Parameter MUST be present and MUST be understood and processed by implementations when these algorithms are used.

The salt expands the possible keys that can be derived from a given password. A Salt Input value containing 8 or more octets MUST be used. A new Salt Input value MUST be generated randomly for every encryption operation; see [RFC4086] for considerations on generating random values. The salt value used is (UTF8(Alg) || 0x00 || Salt Input), where Alg is the alg Header Parameter value.

4.8.1.2. "p2c" (PBES2 count) Parameter

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

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

5. Cryptographic Algorithms for Content Encryption

JWE uses cryptographic algorithms to encrypt the Plaintext.

5.1. "enc" (Encryption Algorithm) Header Parameter Values for JWE

The table below is the set of enc (encryption algorithm) 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 AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 5.2.3 (none) Required
A192CBC-HS384 AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm, as defined in Section 5.2.4 (none) Optional
A256CBC-HS512 AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm, as defined in Section 5.2.5 (none) Required
A128GCM AES GCM using 128 bit key (none) Recommended
A192GCM AES GCM using 192 bit key (none) Optional
A256GCM AES GCM using 256 bit key (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 A.3 for a table cross-referencing the JWE enc (encryption algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.

5.2. 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 B.

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

5.2.1. Conventions Used in Defining AES_CBC_HMAC_SHA2

We use the following notational conventions.

5.2.2. 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 5.2.2.1 and Section 5.2.2.2 define the generic encryption and decryption algorithms. Section 5.2.3 and Section 5.2.5 define instances of AES_CBC_HMAC_SHA2 that specify those details.

5.2.2.1. 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 5.2.3 and Section 5.2.5). 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.

5.2.2.2. 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 5.2.2.1.
  2. The integrity and authenticity of A and E are checked by computing an HMAC with the inputs as in Step 5 of Section 5.2.2.1. 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.

5.2.3. 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 and a 128 bit initialization vector (IV) value.

The AES_CBC_HMAC_SHA2 parameters specific to AES_128_CBC_HMAC_SHA_256 are:

5.2.4. 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:

5.2.5. 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:

5.2.6. Content Encryption with AES_CBC_HMAC_SHA2

The following enc (encryption algorithm) Header Parameter values are used to indicate that the JWE Ciphertext and JWE Authentication Tag values have been computed using the corresponding algorithm:

enc Parameter Value Content Encryption Algorithm
A128CBC-HS256 AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm, as defined in Section 5.2.3
A192CBC-HS384 AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm, as defined in Section 5.2.4
A256CBC-HS512 AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm, as defined in Section 5.2.5

5.3. Content 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]. 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 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.

The following enc (encryption algorithm) Header Parameter values are used to indicate that the JWE Ciphertext and JWE Authentication Tag values have been computed using the corresponding algorithm and key size:

enc Parameter Value Content Encryption Algorithm
A128GCM AES GCM using 128 bit key
A192GCM AES GCM using 192 bit key
A256GCM AES GCM using 256 bit key

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

6. Cryptographic Algorithms for Keys

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.

6.1. "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.

6.2. Parameters for Elliptic Curve Keys

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

6.2.1. Parameters for Elliptic Curve Public Keys

An elliptic curve public key is represented by a pair of coordinates drawn from a finite field, which together define a point on an elliptic curve. The following members MUST be present for elliptic curve public keys:

SEC1 [SEC1] point compression is not supported for any values.

6.2.1.1. "crv" (Curve) Parameter

The crv (curve) member identifies the cryptographic curve used with the key. Curve values from [DSS] used by this specification are: Section 7.6. 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.

These values are registered in the IANA JSON Web Key Elliptic Curve registry defined in

6.2.1.2. "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 octet string representation of the coordinate, as defined in Section 2.3.5 of SEC1 [SEC1]. The length of this octet string MUST be the full size of a coordinate for the curve specified in the crv parameter. For example, if the value of crv is P-521, the octet string must be 66 octets long.

6.2.1.3. "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 octet string representation of the coordinate, as defined in Section 2.3.5 of SEC1 [SEC1]. The length of this octet string MUST be the full size of a coordinate for the curve specified in the crv parameter. For example, if the value of crv is P-521, the octet string must be 66 octets long.

6.2.2. 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.

6.2.2.1. "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 octet string representation of the private key value, as defined in Sections C.4 and 2.3.7 of SEC1 [SEC1]. The length of this octet string MUST be ceiling(log-base-2(n)/8) octets (where n is the order of the curve).

6.3. Parameters for RSA Keys

JWKs can represent RSA [RFC3447] keys. In this case, the kty member value MUST be RSA.

6.3.1. Parameters for RSA Public Keys

The following members MUST be present for RSA public keys.

6.3.1.1. "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 octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.1.2. "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 octet sequence 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].

6.3.2. 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 SHOULD be included by producers of JWKs representing RSA private keys. If the producer includes any of the other private key parameters, then all of the others MUST be present, with the exception of oth, which MUST only be present when more than two prime factors were used. The consumer of a JWK MAY choose to accept an RSA private key that does not contain a complete set of the private key parameters other than d, including JWKs in which d is the only RSA private key parameter included.

6.3.2.1. "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 octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.2. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.3. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.4. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.5. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.6. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.7. "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:

6.3.2.7.1. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.7.2. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.3.2.7.3. "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. The octet sequence MUST utilize the minimum number of octets to represent the value.

6.4. Parameters for Symmetric Keys

When the JWK kty member value is oct (octet sequence), the member k is used to represent a symmetric key (or another key whose value is a single octet sequence). An alg member SHOULD also be present to identify the algorithm intended to be used with the key, unless the application uses another means or convention to determine the algorithm used.

6.4.1. "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.

7. 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 the 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. Registration requests that are undetermined for a period longer than 21 days can be brought to the IESG's attention (using the iesg@iesg.org mailing list) for resolution.

Criteria that should be applied by the Designated Expert(s) includes determining whether the proposed registration duplicates existing functionality, determining whether it is likely to be of general applicability or whether it is useful only for a single application, and whether the registration makes sense.

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

It is suggested that multiple Designated Experts be appointed who are able to represent the perspectives of different applications using this specification, in order to enable broadly-informed review of registration decisions. In cases where a registration decision could be perceived as creating a conflict of interest for a particular Expert, that Expert should defer to the judgment of the other Expert(s).

7.1. 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 algorithm) Header Parameters. The registry records the algorithm name, the algorithm usage locations, implementation requirements, and a reference to the specification that defines it. The same algorithm name can be registered multiple times, provided that the sets of usage locations are disjoint.

It is suggested that when algorithms can use keys of different lengths, that the length of the key be included in the algorithm name. This allows readers of the JSON text to easily make security consideration decisions.

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.

7.1.1. Registration Template

Algorithm Name:

The name requested (e.g., "example"). This name is case-sensitive. Names may not match other registered names in a case-insensitive manner unless the Designated Expert(s) state that there is a compelling reason to allow an exception in this particular case.
Algorithm Description:

Brief description of the Algorithm (e.g., "Example description").
Algorithm Usage Location(s):

The algorithm usage location. This must be one or more of the values alg or enc if the algorithm is to be used with JWS or JWE. The value JWK is used if the algorithm identifier will be used as a JWK alg member value, but will not be used with JWS or JWE; this could be the case, for instance, for non-authenticated encryption algorithms. Other values may be used with the approval of a Designated Expert.
JOSE Implementation Requirements:

The algorithm implementation requirements for JWS and JWE, which must be one the words Required, Recommended, Optional, Deprecated, or Prohibited. 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. Any identifiers registered for non-authenticated encryption algorithms or other algorithms that are otherwise unsuitable for direct use as JWS or JWE algorithms must be registered as "Prohibited".
Change Controller:

For Standards Track RFCs, state "IESG". 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.

7.1.2. Initial Registry Contents

7.2. JWE Header Parameter Names Registration

This specification registers the Header Parameter names defined in Section 4.6.1, Section 4.7.1, and Section 4.8.1 in the IANA JSON Web Signature and Encryption Header Parameters registry defined in [JWS].

7.2.1. Registry Contents

7.3. JSON Web Encryption Compression Algorithms Registry

This specification establishes the IANA JSON Web Encryption Compression Algorithms registry for JWE zip member values. The registry records the compression algorithm value and a reference to the specification that defines it.

7.3.1. Registration Template

Compression Algorithm Value:

The name requested (e.g., "example"). Because a core goal of this specification is for the resulting representations to be compact, it is RECOMMENDED that the name be short -- not to exceed 8 characters without a compelling reason to do so. This name is case-sensitive. Names may not match other registered names in a case-insensitive manner unless the Designated Expert(s) state that there is a compelling reason to allow an exception in this particular case.
Compression Algorithm Description:

Brief description of the compression algorithm (e.g., "Example description").
Change Controller:

For Standards Track RFCs, state "IESG". 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.

7.3.2. Initial Registry Contents

7.4. 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.

7.4.1. Registration Template

"kty" Parameter Value:

The name requested (e.g., "example"). Because a core goal of this specification is for the resulting representations to be compact, it is RECOMMENDED that the name be short -- not to exceed 8 characters without a compelling reason to do so. This name is case-sensitive. Names may not match other registered names in a case-insensitive manner unless the Designated Expert(s) state that there is a compelling reason to allow an exception in this particular case.
Key Type Description:

Brief description of the Key Type (e.g., "Example description").
Change Controller:

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

The key type implementation requirements for JWS and JWE, which must be one the words Required, Recommended, Optional, Deprecated, or Prohibited. 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.

7.4.2. Initial Registry Contents

This specification registers the values defined in Section 6.1.

7.5. JSON Web Key Parameters Registration

This specification registers the parameter names defined in Sections 6.2, 6.3, and 6.4 in the IANA JSON Web Key Parameters registry defined in [JWK].

7.5.1. Registry Contents

7.6. JSON Web Key Elliptic Curve Registry

This specification establishes the IANA JSON Web Key Elliptic Curve registry for JWK crv member values. The registry records the curve name, implementation requirements, and a reference to the specification that defines it. This specification registers the parameter names defined in Section 6.2.1.1.

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

7.6.1. Registration Template

Curve Name:

The name requested (e.g., "example"). Because a core goal of this specification is for the resulting representations to be compact, it is RECOMMENDED that the name be short -- not to exceed 8 characters without a compelling reason to do so. This name is case-sensitive. Names may not match other registered names in a case-insensitive manner unless the Designated Expert(s) state that there is a compelling reason to allow an exception in this particular case.
Curve Description:

Brief description of the curve (e.g., "Example description").
JOSE Implementation Requirements:

The curve implementation requirements for JWS and JWE, which must be one the words Required, Recommended, Optional, Deprecated, or Prohibited. 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 "IESG". 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.

7.6.2. Initial Registry Contents

8. 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.

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.

8.1. Algorithms and Key Sizes will be Deprecated

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

8.2. Key Lifetimes

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.

8.3. RSAES-PKCS1-v1_5 Security Considerations

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.

8.4. AES GCM Security Considerations

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

An Initialization Vector value MUST never be used multiple times with the same AES GCM key. One way to prevent this is to store a counter with the key and increment it with every use. The counter can also be used to prevent exceeding the 2^32 limit above.

This security consideration does not apply to the composite AES-CBC HMAC SHA-2 or AES Key Wrap algorithms.

8.5. Plaintext JWS Security Considerations

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.

Implementations that support plaintext JWS objects MUST NOT accept such objects as valid unless the application specifies that it is acceptable for a specific object to not be integrity-protected. Implementations MUST NOT accept plaintext JWS objects by default. For example, the "verify" method of a hypothetical JWS software library might have a Boolean "acceptUnsigned" parameter that indicates none is an acceptable alg value. As another example, the "verify" method might take a list of algorithms that are acceptable to the application as a parameter and would reject plaintext JWS values if none is not in that list.

In order to mitigate downgrade attacks, applications MUST NOT signal acceptance of plaintext JWS objects at a global level, and SHOULD signal acceptance on a per-object basis. For example, suppose an application accepts JWS objects over two channels, (1) HTTP and (2) HTTPS with client authentication. It requires a JWS signature on objects received over HTTP, but accepts plaintext JWS objects over HTTPS. If the application were to globally indicate that none is acceptable, then an attacker could provide it with an unsigned object over HTTP and still have that object successfully validate. Instead, the application needs to indicate acceptance of none for each object received over HTTPS (e.g., by setting "acceptUnsigned" to "true" for the first hypothetical JWS software library above), but not for each object received over HTTP.

8.6. Differences between Digital Signatures and MACs

While in many cases, MACs and digital signatures can be used for integrity checking, there are some significant differences between the security properties that each of them provides. These need to be taken into consideration when designing protocols and selecting the algorithms to be used in protocols.

Both signatures and MACs provide for integrity checking -- verifying that the message has not been modified since the integrity value was computed. However, MACs provide for origination identification only under specific circumstances. It can normally be assumed that a private key used for a signature is only in the hands of a single entity (although perhaps a distributed entity, in the case of replicated servers); however, a MAC key needs to be in the hands of all the entities that use it for integrity computation and checking. This means that origination can only be determined if a MAC key is known only to two entities and the receiver knows that it did not create the message. MAC validation cannot be used to prove origination to a third party.

8.7. Denial of Service Attacks

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.

8.8. 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].

8.9. Password Considerations

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-entropy password has greater resistance to dictionary attacks. [NIST-800-63-1] contains guidelines for estimating password entropy, which can help applications and users generate stronger passwords.

An ideal password is one that is as large as (or larger than) the derived key length. However, passwords larger than a certain algorithm-specific size are first hashed, which reduces an attacker's effective search space to the length of the hash algorithm. It is RECOMMENDED that a password used for PBES2-HS256+A128KW be no shorter than 16 octets and no longer than 128 octets and a password used for PBES2-HS512+A256KW be no shorter than 32 octets and no longer than 128 octets long.

Still, care needs to be taken in where and how password-based encryption is used. These algorithms can still be susceptible to dictionary-based attacks if the iteration count is too small; this is of particular concern if these algorithms are used to protect data that an attacker can have indefinite number of attempts to circumvent the protection, such as protected data stored on a file system.

9. 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.ietf-precis-saslprepbis] to prepare a password supplied directly by a user before performing key derivation and encryption.

10. References

10.1. Normative References

[AES] National Institute of Standards and Technology (NIST), "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001.
[DSS] National Institute of Standards and Technology, "Digital Signature Standard (DSS)", FIPS PUB 186-4, July 2013.
[JWE] Jones, M., Rescorla, E. and J. Hildebrand, "JSON Web Encryption (JWE)", Internet-Draft draft-ietf-jose-json-web-encryption, March 2014.
[JWK] Jones, M., "JSON Web Key (JWK)", Internet-Draft draft-ietf-jose-json-web-key, March 2014.
[JWS] Jones, M., Bradley, J. and N. Sakimura, "JSON Web Signature (JWS)", Internet-Draft draft-ietf-jose-json-web-signature, March 2014.
[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.
[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.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.
[RFC6090] McGrew, D., Igoe, K. and M. Salter, "Fundamental Elliptic Curve Cryptography Algorithms", RFC 6090, February 2011.
[RFC7158] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7158, March 2014.
[SEC1] Standards for Efficient Cryptography Group, "SEC 1: Elliptic Curve Cryptography", May 2009.
[SHS] National Institute of Standards and Technology, "Secure Hash Standard (SHS)", FIPS PUB 180-3, October 2008.
[USASCII] American National Standards Institute, "Coded Character Set -- 7-bit American Standard Code for Information Interchange", ANSI X3.4, 1986.

10.2. Informative References

[CanvasApp] Facebook, , "Canvas Applications", 2010.
[I-D.ietf-precis-saslprepbis] Saint-Andre, P. and A. Melnikov, "Preparation and Comparison of Internationalized Strings Representing Usernames and Passwords", Internet-Draft draft-ietf-precis-saslprepbis-06, December 2013.
[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-sha2-04, February 2014.
[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.
[I-D.rescorla-jsms] Rescorla, E. and J. Hildebrand, "JavaScript Message Security Format", Internet-Draft draft-rescorla-jsms-00, March 2011.
[JCA] Oracle, , "Java Cryptography Architecture", 2013.
[JSE] Bradley, J. and N. Sakimura (editor), "JSON Simple Encryption", September 2010.
[JSS] Bradley, J. and N. Sakimura (editor), "JSON Simple Sign", September 2010.
[MagicSignatures] Panzer (editor), J., Laurie, B. and D. Balfanz, "Magic Signatures", January 2011.
[NIST-800-63-1] National Institute of Standards and Technology (NIST), "Electronic Authentication Guideline", NIST 800-63-1, December 2011.
[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.
[RFC4086] Eastlake, D., Schiller, J. and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005.
[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.
[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.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.
[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.

Appendix A. Algorithm Identifier Cross-Reference

This appendix contains tables cross-referencing the cryptographic algorithm identifier values defined in this specification with the equivalent identifiers used by other standards and software packages. See XML DSIG [RFC3275], XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124], 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.

A.1. Digital Signature/MAC Algorithm Identifier Cross-Reference

This section contains a table cross-referencing the JWS digital signature and MAC alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.

JWS XML DSIG JCA OID
HS256 http://www.w3.org/2001/04/xmldsig-more#hmac-sha256 HmacSHA256 1.2.840.113549.2.9
HS384 http://www.w3.org/2001/04/xmldsig-more#hmac-sha384 HmacSHA384 1.2.840.113549.2.10
HS512 http://www.w3.org/2001/04/xmldsig-more#hmac-sha512 HmacSHA512 1.2.840.113549.2.11
RS256 http://www.w3.org/2001/04/xmldsig-more#rsa-sha256 SHA256withRSA 1.2.840.113549.1.1.11
RS384 http://www.w3.org/2001/04/xmldsig-more#rsa-sha384 SHA384withRSA 1.2.840.113549.1.1.12
RS512 http://www.w3.org/2001/04/xmldsig-more#rsa-sha512 SHA512withRSA 1.2.840.113549.1.1.13
ES256 http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256 SHA256withECDSA 1.2.840.10045.4.3.2
ES384 http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384 SHA384withECDSA 1.2.840.10045.4.3.3
ES512 http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512 SHA512withECDSA 1.2.840.10045.4.3.4
PS256 http://www.w3.org/2007/05/xmldsig-more#sha256-rsa-MGF1 SHA256withRSAandMGF1 1.2.840.113549.1.1.10
PS384 http://www.w3.org/2007/05/xmldsig-more#sha384-rsa-MGF1 SHA384withRSAandMGF1 1.2.840.113549.1.1.10
PS512 http://www.w3.org/2007/05/xmldsig-more#sha512-rsa-MGF1 SHA512withRSAandMGF1 1.2.840.113549.1.1.10

A.2. Key Management Algorithm Identifier Cross-Reference

This section contains a table cross-referencing the JWE alg (algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.

JWE XML ENC JCA OID
RSA1_5 http://www.w3.org/2001/04/xmlenc#rsa-1_5 RSA/ECB/PKCS1Padding 1.2.840.113549.1.1.1
RSA-OAEP http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p RSA/ECB/OAEPWithSHA-1AndMGF1Padding 1.2.840.113549.1.1.7
ECDH-ES http://www.w3.org/2009/xmlenc11#ECDH-ES 1.3.132.1.12
A128KW http://www.w3.org/2001/04/xmlenc#kw-aes128 2.16.840.1.101.3.4.1.5
A192KW http://www.w3.org/2001/04/xmlenc#kw-aes192 2.16.840.1.101.3.4.1.25
A256KW http://www.w3.org/2001/04/xmlenc#kw-aes256 2.16.840.1.101.3.4.1.45

A.3. Content Encryption Algorithm Identifier Cross-Reference

This section contains a table cross-referencing the JWE enc (encryption algorithm) values defined in this specification with the equivalent identifiers used by other standards and software packages.

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

JWE XML ENC JCA OID
A128CBC-HS256 http://www.w3.org/2001/04/xmlenc#aes128-cbc AES/CBC/PKCS5Padding 2.16.840.1.101.3.4.1.2
A192CBC-HS384 http://www.w3.org/2001/04/xmlenc#aes192-cbc AES/CBC/PKCS5Padding 2.16.840.1.101.3.4.1.22
A256CBC-HS512 http://www.w3.org/2001/04/xmlenc#aes256-cbc AES/CBC/PKCS5Padding 2.16.840.1.101.3.4.1.42
A128GCM http://www.w3.org/2009/xmlenc11#aes128-gcm AES/GCM/NoPadding 2.16.840.1.101.3.4.1.6
A192GCM http://www.w3.org/2009/xmlenc11#aes192-gcm AES/GCM/NoPadding 2.16.840.1.101.3.4.1.26
A256GCM http://www.w3.org/2009/xmlenc11#aes256-gcm AES/GCM/NoPadding 2.16.840.1.101.3.4.1.46

Appendix B. 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 5.2. They are also intended to correspond to test cases that may appear in a future version of [I-D.mcgrew-aead-aes-cbc-hmac-sha2], demonstrating that the cryptographic computations performed are the same.

The variable names are those defined in Section 5.2. All values are hexadecimal.

B.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

B.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

B.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 C. 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 4.6. In this example, the ECDH-ES Direct Key Agreement mode (alg value ECDH-ES) is used to produce an agreed upon key for AES GCM with a 128 bit key (enc value A128GCM).

In this example, a 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 32 bit big endian value 7 - [0, 0, 0, 7] - the number of octets in the AlgorithmID content "A128GCM", followed, by 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:
[0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]

Concatenating the round number 1 ([0, 0, 0, 1]), Z, and the OtherInfo value results in the Concat KDF round 1 hash input of:
[0, 0, 0, 1,
158, 86, 217, 29, 129, 113, 53, 211, 114, 131, 66, 131, 191, 132, 38, 156, 251, 49, 110, 163, 218, 128, 106, 72, 246, 218, 167, 121, 140, 254, 144, 196,
0, 0, 0, 7, 65, 49, 50, 56, 71, 67, 77, 0, 0, 0, 5, 65, 108, 105, 99, 101, 0, 0, 0, 3, 66, 111, 98, 0, 0, 0, 128]

The resulting derived key, which is the first 128 bits of the round 1 hash output is:
[86, 170, 141, 234, 248, 35, 109, 32, 92, 34, 40, 205, 113, 167, 16, 26]

The base64url encoded representation of this derived key is:

  VqqN6vgjbSBcIijNcacQGg

Appendix D. 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, Vladimir Dzhuvinov, 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 E. Document History

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

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Author's Address

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