JSON Web Algorithms (JWA)
Microsoft
mbj@microsoft.com
http://self-issued.info/
Security
JOSE Working Group
RFC
Request for Comments
I-D
Internet-Draft
JavaScript Object Notation
JSON
JSON Web Token
JWT
JSON Web Signature
JWS
JSON Web Encryption
JWE
JSON Web Key
JWK
JSON Web Algorithms
JWA
The JSON Web Algorithms (JWA) specification enumerates
cryptographic algorithms and identifiers to be used with the
JSON Web Signature (JWS),
JSON Web Encryption (JWE), and
JSON Web Key (JWK) specifications.
The JSON Web Algorithms (JWA) specification enumerates
cryptographic algorithms and identifiers to be used with the
JSON Web Signature (JWS) ,
JSON Web Encryption (JWE) , and
JSON Web Key (JWK) specifications.
All these specifications utilize
JavaScript Object Notation (JSON)
based data structures.
This specification also describes the semantics and operations
that are specific to these algorithms and algorithm families.
Enumerating the algorithms and identifiers for them in this
specification, rather than in the JWS, JWE, and JWK
specifications, is intended to allow them to remain unchanged
in the face of changes in the set of required, recommended,
optional, and deprecated algorithms over time.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" in this document are to be interpreted as
described in
Key words for use in RFCs to Indicate Requirement Levels .
These terms defined by the
JSON Web Signature (JWS)
specification are incorporated into this specification:
A data structure cryptographically securing a JWS Header
and a JWS Payload with a JWS Signature value.
A string representing a
JavaScript Object Notation (JSON)
object that describes the
digital signature or MAC operation applied to
create the JWS Signature value.
The bytes to be secured - a.k.a., the message.
The payload can contain an arbitrary sequence of bytes.
A byte array containing the cryptographic
material that secures the contents of the JWS Header
and the JWS Payload.
The URL- and filename-safe Base64 encoding
described in RFC 4648,
Section 5, with the (non URL-safe) '=' padding characters
omitted, as permitted by Section 3.2. (See Appendix C of
for notes on implementing base64url
encoding without padding.)
Base64url encoding of the bytes of the
UTF-8
representation of the JWS Header.
Base64url encoding of the JWS Payload.
Base64url encoding of the JWS Signature.
The concatenation of the Encoded JWS Header, a period ('.')
character, and the Encoded JWS Payload.
A namespace that allows names to be allocated in a manner
such that they are highly unlikely to collide with other names.
For instance, collision resistance can be achieved through
administrative delegation of portions of the namespace or
through use of collision-resistant name allocation functions.
Examples of Collision Resistant Namespaces include:
Domain Names,
Object Identifiers (OIDs) as defined in the ITU-T X.660
and X.670 Recommendation series, and
Universally Unique IDentifiers (UUIDs)
.
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.
These terms defined by the
JSON Web Encryption (JWE)
specification are incorporated into this specification:
A data structure representing an encrypted version of a
Plaintext. The structure consists of four parts: the JWE
Header, the JWE Encrypted Key, the JWE Ciphertext, and
the JWE Integrity Value.
The bytes to be encrypted - a.k.a., the message.
The plaintext can contain an arbitrary sequence of bytes.
The encrypted version of the Plaintext.
A symmetric key used to encrypt the Plaintext for the
recipient to produce the Ciphertext.
A key used with a MAC function to ensure the integrity
of the Ciphertext and the parameters used to create it.
A key from which the CEK and CIK are derived.
When key wrapping or key encryption are employed, the CMK
is randomly generated and encrypted to the recipient as
the JWE Encrypted Key.
When key agreement is employed, the CMK is the result of
the key agreement algorithm.
A string representing a JSON object that describes the
encryption operations applied to create the JWE Encrypted
Key, the JWE Ciphertext, and the JWE Integrity Value.
When key wrapping or key encryption are employed,
the Content Master Key (CMK) is encrypted with the
intended recipient's key and the resulting encrypted
content is recorded as a byte array, which is referred to
as the JWE Encrypted Key.
Otherwise, when key agreement is employed,
the JWE Encrypted Key is the empty byte array.
A byte array containing the Ciphertext.
A byte array containing a MAC value that ensures the
integrity of the Ciphertext and the parameters used to
create it.
Base64url encoding of the bytes of the
UTF-8
representation of the JWE Header.
Base64url encoding of the JWE Encrypted Key.
Base64url encoding of the JWE Ciphertext.
Base64url encoding of the JWE Integrity Value.
An Authenticated Encryption with Associated Data (AEAD)
encryption algorithm is one that
provides an integrated content integrity check. AES
Galois/Counter Mode (GCM) is one such algorithm.
These terms defined by the
JSON Web Key (JWK)
specification are incorporated into this specification:
A JSON data structure that represents a public key.
A JSON object that contains an array of JWKs as a member.
These terms are defined for use by this specification:
The name of a member of the JSON object representing a
JWS Header or JWE Header.
The value of a member of the JSON object representing a
JWS Header or JWE Header.
JWS uses cryptographic algorithms to digitally sign or
create a Message Authentication Codes (MAC) of the contents
of the JWS Header and the JWS Payload. The
use of the following algorithms for producing JWSs is defined in
this section.
The table below is the set of
alg (algorithm) header
parameter values defined by this specification for use with JWS, each of which
is explained in more detail in the following sections:
alg Parameter Value
Digital Signature or MAC Algorithm
Implementation Requirements
HS256
HMAC using SHA-256 hash algorithm
REQUIRED
HS384
HMAC using SHA-384 hash algorithm
OPTIONAL
HS512
HMAC using SHA-512 hash algorithm
OPTIONAL
RS256
RSASSA using SHA-256 hash algorithm
RECOMMENDED
RS384
RSASSA using SHA-384 hash algorithm
OPTIONAL
RS512
RSASSA using SHA-512 hash algorithm
OPTIONAL
ES256
ECDSA using P-256 curve and SHA-256 hash algorithm
RECOMMENDED+
ES384
ECDSA using P-384 curve and SHA-384 hash algorithm
OPTIONAL
ES512
ECDSA using P-521 curve and SHA-512 hash algorithm
OPTIONAL
none
No digital signature or MAC value included
REQUIRED
All the names are short because a core goal of JWS is
for the representations to be compact. However, there is no
a priori length restriction on alg values.
The use of "+" in the Implementation Requirements
indicates that the requirement strength is likely
to be increased in a future version of the specification.
See for a table cross-referencing the
digital signature and MAC alg (algorithm)
values used in this specification
with the equivalent identifiers used by other
standards and software packages.
Hash-based Message Authentication Codes (HMACs) enable one to
use a secret plus a cryptographic hash function to generate a
Message Authentication Code (MAC). This can be used to
demonstrate that the MAC matches the hashed content, in this
case the JWS Secured Input, which therefore demonstrates that
whoever generated the MAC was in possession of the secret.
The means of exchanging the shared key is outside the scope
of this specification.
The algorithm for implementing and validating HMACs is
provided in RFC 2104. This
section defines the use of the HMAC SHA-256, HMAC SHA-384,
and HMAC SHA-512 functions . 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 bytes of the ASCII representation
of the JWS Secured 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 bytes of the ASCII representation
of the received JWS Secured input as the "text" value,
and using the shared key.
This computed HMAC value is then compared to the result of
base64url decoding the received Encoded JWS signature.
Alternatively, the computed HMAC value can be base64url encoded
and compared to the received Encoded JWS Signature,
as this comparison produces the same result as comparing
the unencoded values.
In either case, if the values match, the HMAC has been validated.
If the validation fails, the JWS MUST be rejected.
Securing content with the HMAC SHA-384 and HMAC SHA-512
algorithms is performed identically to the procedure for
HMAC SHA-256 -
just using the corresponding hash algorithm
with correspondingly larger minimum key sizes and result values:
384 bits each for HMAC SHA-384 and 512 bits each for HMAC SHA-512.
This section defines the use of the RSASSA-PKCS1-V1_5
digital signature algorithm as defined in
Section 8.2 of RFC 3447,
(commonly known as PKCS #1),
using SHA-256, SHA-384, or SHA-512
as the hash functions.
The alg (algorithm) header
parameter values RS256, RS384, and RS512 are used in the JWS Header
to indicate that the Encoded JWS Signature contains a base64url
encoded RSA digital signature using the respective hash function.
A key of size 2048 bits or larger MUST be used with these algorithms.
The RSA SHA-256 digital signature is generated as follows:
Generate a digital signature of the bytes of the ASCII representation
of the JWS Secured Input
using RSASSA-PKCS1-V1_5-SIGN
and the SHA-256 hash function with the desired private
key. The output will be a byte array.
Base64url encode the resulting byte array.
The output is the Encoded JWS Signature for that JWS.
The RSA SHA-256 digital signature for a JWS is validated as follows:
Take the Encoded JWS Signature and base64url decode it into
a byte array. If decoding fails, the JWS MUST
be rejected.
Submit the bytes of the ASCII representation of the JWS Secured 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.
If the validation fails, the JWS MUST be rejected.
Signing with the RSA SHA-384 and RSA SHA-512
algorithms is performed identically to the procedure for
RSA SHA-256 -
just using the corresponding hash algorithm
with correspondingly larger result values:
384 bits for RSA SHA-384 and 512 bits for RSA SHA-512.
The Elliptic Curve Digital Signature Algorithm (ECDSA)
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 . 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:
Generate a digital signature of the bytes of the ASCII representation
of the JWS Secured 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.
Turn R and S into byte arrays in big endian order,
with each array being be 32 bytes long.
The array representations MUST not be shortened
to omit any leading zero bytes contained in the values.
Concatenate the two byte arrays in the order R and then S.
(Note that many ECDSA implementations will directly produce
this concatenation as their output.)
Base64url encode the resulting 64 byte array.
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:
Take the Encoded JWS Signature and base64url decode it into
a byte array. If decoding fails, the JWS MUST
be rejected.
The output of the base64url decoding MUST be a 64 byte
array.
If decoding does not result in a 64 byte array, the JWS MUST be rejected.
Split the 64 byte array into two 32 byte arrays. The first
array will be R and the second S
(with both being in big endian byte order).
Submit the bytes of the ASCII representation of the JWS Secured Input
R, S and the public key (x, y) to the ECDSA P-256
SHA-256 validator.
If the validation fails, the JWS MUST be rejected.
Note that ECDSA digital
signature contains a value referred to as K, which is a random
number generated for each digital signature instance. This
means that two ECDSA digital signatures using exactly the same
input parameters will output different signature values because
their K values will be different. A consequence of this is
that one cannot validate an ECDSA signature by recomputing
the signature and comparing the results.
Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512
algorithms is performed identically to the procedure for
ECDSA P-256 SHA-256 -
just using the corresponding hash algorithm
with correspondingly larger result values.
For ECDSA P-384 SHA-384, R and S will be 384 bits each,
resulting in a 96 byte array.
For ECDSA P-521 SHA-512, R and S will be 521 bits each,
resulting in a 132 byte array.
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 an empty JWS Signature
value.
Additional algorithms MAY be used to protect JWSs with
corresponding alg (algorithm)
header parameter values being defined to refer to them.
New alg header parameter values SHOULD
either be registered in the IANA JSON Web Signature and Encryption Algorithms
registry or be
a URI that contains a Collision Resistant Namespace.
In particular, it is permissible to use the algorithm identifiers defined in
XML DSIG,
XML DSIG 2.0,
and related specifications as
alg values.
As indicated by the common registry, JWSs and JWEs share a
common alg value space.
The values used by the two specifications MUST be distinct,
as the alg value MAY be used
to determine whether the object is a JWS or JWE.
Likewise, additional reserved header parameter names MAY be defined
via the IANA
JSON Web Signature and Encryption Header Parameters registry
.
As indicated by the common registry, JWSs and JWEs share a
common header parameter space; when a parameter is used by
both specifications, its usage must be compatible
between the specifications.
JWE uses cryptographic algorithms to encrypt the Content
Master Key (CMK) and the Plaintext. This section
specifies a set of specific algorithms for these purposes.
The table below is the set of alg (algorithm) header parameter values
that are defined by this specification for use with JWE.
These algorithms are used to encrypt the CMK, producing the
JWE Encrypted Key, or to use key agreement to agree upon the CMK.
alg Parameter Value
Key Encryption or Agreement Algorithm
Implementation Requirements
RSA1_5
RSAES-PKCS1-V1_5
REQUIRED
RSA-OAEP
RSAES using Optimal Asymmetric Encryption Padding (OAEP)
, with the
default parameters specified by RFC 3447 in Section A.2.1
OPTIONAL
ECDH-ES
Elliptic Curve Diffie-Hellman Ephemeral Static
, and using the
Concat KDF, as defined in Section 5.8.1 of ,
where the Digest Method is SHA-256 and all OtherInfo
parameters are the empty bit string
RECOMMENDED+
A128KW
Advanced Encryption Standard (AES) Key Wrap Algorithm
using 128 bit keys
RECOMMENDED
A256KW
AES Key Wrap Algorithm
using 256 bit keys
RECOMMENDED
The use of "+" in the Implementation Requirements
indicates that the requirement strength is likely
to be increased in a future version of the specification.
The table below is the set of
enc (encryption method) header parameter values that
are defined by this specification for use with JWE. These algorithms are used
to encrypt the Plaintext, which produces the Ciphertext.
enc Parameter Value
Block Encryption Algorithm
Implementation Requirements
A128CBC
Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding
using 128 bit keys
REQUIRED
A256CBC
AES in CBC mode with PKCS #5 padding
using 256 bit keys
REQUIRED
A128GCM
AES in Galois/Counter Mode (GCM)
using 128 bit keys
RECOMMENDED
A256GCM
AES GCM
using 256 bit keys
RECOMMENDED
All the names are short because a core goal of JWE is
for the representations to be compact. However, there is no
a priori length restriction on alg values.
See 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.
The table below is the set of
int (integrity algorithm) header
parameter values defined by this specification for use with JWE.
Note that these are the HMAC SHA subset of the
alg (algorithm) header parameter values
defined for use with JWS .
int Parameter Value
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
The table below is the set of
kdf (key derivation function) header
parameter values defined by this specification for use with JWE.
kdf Parameter Value
Algorithm
Implementation Requirements
CS256
Concat KDF, as defined in Section 5.8.1 of ,
with parameters per ,
using SHA-256 as the digest method
REQUIRED
CS384
Concat KDF with parameters per ,
using SHA-384 as the digest method
OPTIONAL
CS512
Concat KDF with parameters per ,
using SHA-512 as the digest method
OPTIONAL
This section defines the specifics of encrypting a JWE CMK with
RSAES-PKCS1-V1_5 .
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.
This section defines the specifics of encrypting a JWE CMK with
RSAES using Optimal Asymmetric Encryption Padding (OAEP)
, 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.
This section defines the specifics of agreeing upon a JWE CMK with
Elliptic Curve Diffie-Hellman Ephemeral Static ,
and using the
Concat KDF, as defined in Section 5.8.1 of ,
where the Digest Method is SHA-256 and all OtherInfo
parameters are the empty bit string.
The alg header parameter value
ECDH-ES is used in this case.
The output of the Concat KDF MUST be a key of the
same length as that used by the
enc algorithm.
A new epk (ephemeral public key)
value MUST be generated for each key agreement transaction.
This section defines the specifics of encrypting a JWE CMK with
the Advanced Encryption Standard (AES) Key Wrap Algorithm
using 128 or 256 bit keys.
The alg header parameter values
A128KW or A256KW
are used in this case.
This section defines the specifics of encrypting the JWE Plaintext with
Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding
using 128 or 256 bit keys.
The enc header parameter values
A128CBC or A256CBC
are used in this case.
Use of an initialization vector of size 128 bits is
REQUIRED with this algorithm.
This section defines the specifics of encrypting the JWE Plaintext with
Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM)
using 128 or 256 bit keys.
The enc header parameter values
A128GCM or A256GCM
are used in this case.
Use of an initialization vector of size 96 bits is
REQUIRED with this algorithm.
The "additional authenticated data" parameter is used to
secure the header and key values, as specified for
AEAD algorithms in Section 5 of .
The requested size of the "authentication tag" output MUST be
128 bits, regardless of the key size.
As GCM is an AEAD algorithm, the JWE Integrity Value is set
to be the "authentication tag" value produced by the encryption.
This section defines the specifics of computing a JWE Integrity Value with
HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512 .
Other than as stated below, these computations are performed
identically to those specified in .
A key of the same size as the hash output (for instance, 256
bits for HS256) MUST
be used with this algorithm.
Per Section 9 of , the JWS Secured Input value
used contains the header, encrypted key, and ciphertext.
The key derivation process derives CEK and CIK values from the CMK.
It uses as a primitive a Key Derivation Function (KDF)
which notionally takes three arguments:
The master key used to compute the
individual use keys
The use key label, used to differentiate
individual use keys
The desired length of the use key
This section defines the specifics of using the Concat KDF, as
defined in Section 5.8.1 of , where the Digest
Method is one of SHA-256, SHA-384, or SHA-512,
the SuppPubInfo parameter is the Label, and
the remaining OtherInfo parameters are the empty bit string.
The kdf (key derivation function) header parameter values
CS256, CS384, and
CS512 are respectively used in the JWE Header
to indicate the use of the Concat KDF as above with the respective digest methods.
If the kdf header parameter is omitted when an
AEAD enc algorithm is not used, this is equivalent
to specifying use of the CS256 key derivation function.
To compute the CEK from the CMK, the ASCII label "Encryption"
([69, 110, 99, 114, 121, 112, 116, 105, 111, 110])
is used.
Use the key size for the enc
algorithm as the CEK desired key length.
To compute the CIK from the CMK, the ASCII label "Integrity"
([73, 110, 116, 101, 103, 114, 105, 116, 121])
is used.
Use the minimum key size for the int
algorithm (for instance, 256 bits for HS256)
as the CIK desired key length.
Additional algorithms MAY be used to protect JWEs with
corresponding alg (algorithm),
enc (encryption method), and
int (integrity algorithm)
header parameter values being
defined to refer to them. New
alg,
enc, and
int
header parameter values SHOULD
either be registered in the IANA JSON Web Signature and Encryption Algorithms
registry or be
a URI that contains a Collision Resistant Namespace.
In particular, it is permissible to use the algorithm identifiers defined in
XML Encryption,
XML Encryption 1.1,
and related specifications as
alg,
enc, and
int values.
As indicated by the common registry, JWSs and JWEs share a
common alg value space.
The values used by the two specifications MUST be distinct,
as the alg value MAY be used
to determine whether the object is a JWS or JWE.
Likewise, additional reserved header parameter names MAY be defined
via the IANA JSON Web Signature and Encryption Header Parameters registry
.
As indicated by the common registry, JWSs and JWEs share a
common header parameter space; when a parameter is used by
both specifications, its usage must be compatible
between the specifications.
A JSON Web Key (JWK) is a
JavaScript Object Notation (JSON)
data structure that represents a public key. A JSON Web Key Set
(JWK Set) is a JSON data structure for representing a set of JWKs.
This section specifies a set of algorithm families to be used
for those public keys and the algorithm family specific
parameters for representing those keys.
The table below is the set of
alg (algorithm family) parameter
values that are defined by this specification for use in JWKs.
alg Parameter Value
Algorithm Family
Implementation Requirements
EC
Elliptic Curve key family
RECOMMENDED+
RSA
RSA key family
REQUIRED
All the names are short because a core goal of JWK is
for the representations to be compact. However, there is no
a priori length restriction on alg values.
The use of "+" in the Implementation Requirements
indicates that the requirement strength is likely
to be increased in a future version of the specification.
JWKs can represent Elliptic Curve keys. In
this case, the alg
member value MUST be EC.
Furthermore, these additional members MUST be present:
The crv (curve) member identifies
the cryptographic curve used with the key. Curve values
from used by this specification are:
P-256
P-384
P-521
Additional crv values MAY be used, provided
they are understood by implementations using that Elliptic Curve key.
The crv value is a case sensitive string.
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 a byte array.
The array representation MUST not be shortened
to omit any leading zero bytes contained in the value.
For instance, when representing 521 bit integers,
the byte array to be base64url encoded MUST contain 66 bytes,
including any leading zero bytes.
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 a byte array.
The array representation MUST not be shortened
to omit any leading zero bytes contained in the value.
For instance, when representing 521 bit integers,
the byte array to be base64url encoded MUST contain 66 bytes,
including any leading zero bytes.
JWKs can represent RSA keys. In
this case, the alg
member value MUST be RSA.
Furthermore, these additional members MUST be present:
The mod (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 a byte array.
The array representation MUST not be shortened
to omit any leading zero bytes.
For instance, when representing 2048 bit integers,
the byte array to be base64url encoded MUST contain 256 bytes,
including any leading zero bytes.
The exp (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 a byte array.
The array representation MUST utilize the minimum
number of bytes to represent the value.
For instance, when representing the value 65537,
the byte array to be base64url encoded MUST consist of the
three bytes [1, 0, 1].
Public keys using additional algorithm families MAY be
represented using JWK data structures with corresponding
alg (algorithm family) parameter
values being defined to refer to them.
New alg parameter values SHOULD
either be registered in the
IANA JSON Web Key Algorithm Families registry or be
a URI that contains a Collision Resistant Namespace.
Likewise, parameters for representing keys for additional
algorithm families or additional key properties
SHOULD either be registered in the
IANA JSON Web Key Parameters registry or be
a URI that contains a Collision Resistant Namespace.
The following registration procedure is used for all the
registries established by this specification.
Values are registered with a Specification Required
after a two week review period on the [TBD]@ietf.org mailing
list, on the advice of one or more Designated Experts. However, to allow for the
allocation of values prior to publication, the Designated Expert(s) may approve
registration once they are satisfied that such a specification will be published.
Registration requests must be sent to the [TBD]@ietf.org mailing list for review and
comment, with an appropriate subject (e.g., "Request for access token type: example").
[[ Note to RFC-EDITOR: The name of the mailing list should be determined in consultation
with the IESG and IANA. Suggested name: jose-reg-review. ]]
Within the review period, the Designated Expert(s) will either approve or
deny the registration request, communicating this decision to the review list and IANA.
Denials should include an explanation and, if applicable, suggestions as to how to make
the request successful.
IANA must only accept registry updates from the Designated Expert(s), and should direct
all requests for registration to the review mailing list.
This specification establishes the
IANA JSON Web Signature and Encryption Algorithms registry
for values of the JWS and JWE
alg (algorithm),
enc (encryption method), and
int (integrity algorithm)
header parameters.
The registry records the algorithm name,
the algorithm usage locations from the set
alg,
enc, and
int,
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.
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.
The algorithm usage, which must be one or more of the values
alg,
enc,
int, or
kdf.
The algorithm implementation requirements, which must be one the words
REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED.
Optionally, the word may 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.
For standards-track RFCs, state "IETF". For others, give the name of the
responsible party. Other details (e.g., postal address, e-mail address, home page
URI) may also be included.
Reference to the document that specifies the parameter, preferably including a URI that
can be used to retrieve a copy of the document. An indication of the relevant
sections may also be included, but is not required.
Algorithm Name: HS256
Algorithm Usage Location(s): alg,
int
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s):
and of [[ this document ]]
Algorithm Name: HS384
Algorithm Usage Location(s): alg,
int
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s):
and of [[ this document ]]
Algorithm Name: HS512
Algorithm Usage Location(s): alg,
int
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s):
and of [[ this document ]]
Algorithm Name: RS256
Algorithm Usage Location(s): alg
Implementation Requirements: RECOMMENDED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: RS384
Algorithm Usage Location(s): alg
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: RS512
Algorithm Usage Location(s): alg
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: ES256
Algorithm Usage Location(s): alg
Implementation Requirements: RECOMMENDED+
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: ES384
Algorithm Usage Location(s): alg
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: ES512
Algorithm Usage Location(s): alg
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: none
Algorithm Usage Location(s): alg
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: RSA1_5
Algorithm Usage Location(s): alg
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: RSA-OAEP
Algorithm Usage Location(s): alg
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: ECDH-ES
Algorithm Usage Location(s): alg
Implementation Requirements: RECOMMENDED+
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: A128KW
Algorithm Usage Location(s): alg
Implementation Requirements: RECOMMENDED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: A256KW
Algorithm Usage Location(s): alg
Implementation Requirements: RECOMMENDED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: A128CBC
Algorithm Usage Location(s): enc
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: A256CBC
Algorithm Usage Location(s): enc
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: A128GCM
Algorithm Usage Location(s): enc
Implementation Requirements: RECOMMENDED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: A256GCM
Algorithm Usage Location(s): enc
Implementation Requirements: RECOMMENDED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: CS256
Algorithm Usage Location(s): kdf
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: CS384
Algorithm Usage Location(s): kdf
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Algorithm Name: CS512
Algorithm Usage Location(s): kdf
Implementation Requirements: OPTIONAL
Change Controller: IETF
Specification Document(s): of [[ this document ]]
This specification establishes the
IANA JSON Web Key Algorithm Families registry
for values of the JWK
alg (algorithm family) parameter.
The registry records the alg value
and a reference to the specification that defines it.
This specification registers the values defined in
.
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.
For standards-track RFCs, state "IETF". For others, give the name of the
responsible party. Other details (e.g., postal address, e-mail address, home page
URI) may also be included.
The algorithm implementation requirements, which must be one the words
REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED.
Optionally, the word may 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.
Reference to the document that specifies the parameter, preferably including a URI that
can be used to retrieve a copy of the document. An indication of the relevant
sections may also be included, but is not required.
"alg" Parameter Value: EC
Implementation Requirements: RECOMMENDED+
Change Controller: IETF
Specification Document(s): of [[ this document ]]
"alg" Parameter Value: RSA
Implementation Requirements: REQUIRED
Change Controller: IETF
Specification Document(s): of [[ this document ]]
This specification registers the parameter names defined in
and in the
IANA JSON Web Key Parameters registry .
Parameter Name: crv
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Parameter Name: x
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Parameter Name: y
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Parameter Name: mod
Change Controller: IETF
Specification Document(s): of [[ this document ]]
Parameter Name: exp
Change Controller: IETF
Specification Document(s): of [[ this document ]]
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 key, 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 concerns are
listed here.
The security considerations in
,
,
,
,
,
,
,
,
,
,
,
,
, and
apply to this specification.
Eventually the algorithms and/or key sizes currently described
in this specification will no longer be considered
sufficiently secure and will be removed. Therefore,
implementers and deployments must be prepared for this
eventuality.
Algorithms of matching strength should be used together whenever possible.
For instance, when AES Key Wrap is used with a given key size,
using the same key size for AES CBC or GCM is recommended.
Likewise, when AES CBC is used with a 128 bit key, using HMAC SHA-256
as the integrity algorithm is recommended, whereas when
AES CBC is used with a 256 bit key, using HMAC SHA-512
as the integrity algorithm is recommended.
While Section 8 of RFC 3447
explicitly calls for people not to adopt RSASSA-PKCS1 for new
applications and instead requests that people transition to
RSASSA-PSS, this specification does include RSASSA-PKCS1, for
interoperability reasons, because it commonly implemented.
Keys used with RSAES-PKCS1-v1_5 must follow the constraints in
Section 7.2 of RFC 3447 . In particular, keys with
a low public key exponent value must not be used.
Plaintext JWSs (JWSs that use the alg
value none) provide no integrity protection.
Thus, they must only be used in contexts where the payload is secured by
means other than a digital signature or MAC value, or need not be secured.
Receiving agents that validate signatures and sending agents that
encrypt messages need to be cautious of cryptographic processing
usage when validating signatures and encrypting messages using keys
larger than those mandated in this specification. An attacker could
send certificates with keys that would result in excessive
cryptographic processing, for example, keys larger than those
mandated in this specification, which could swamp the processing
element. Agents that use such keys without first validating the
certificate to a trust anchor are advised to have some sort of
cryptographic resource management system to prevent such attacks.
[[ to be removed by the RFC editor before publication as an RFC ]]
The following items remain to be considered or done in this draft:
Should we use the alg value
as the AlgorithmID input to the Concat KDF when doing key agreement?
Or is an AlgorithmID value unnecessary in the way that we
are using Concat for key agreement?
Similarly, should we use a combination of the
enc and int values
as the AlgorithmID input to the Concat KDF when doing key derivation?
Or is an AlgorithmID value unnecessary in the way that we
are using Concat for key derivation?
Do we need non-empty PartyUInfo and PartyVInfo values when using
the Concat KDF for key agreement? Or given that we already require the
use of a random unique Ephemeral Public Key (EPK), is this superfluous, as
duplicate keys will not be generated unless a duplicate EPK is used?
If we do decide we need PartyUInfo and PartyVInfo values, how can we
dynamically generate them from information already carried in the header,
rather than requiring that they be explicitly passed as header parameters?
Similarly, do we need non-empty PartyUInfo and PartyVInfo values when using
the Concat KDF for key derivation? Or given that we already require the
use of a random unique Content Master Key (CMK), is this superfluous, as
duplicate keys will not be generated unless a duplicate CMK is used?
If we do decide we need PartyUInfo and PartyVInfo values, how can we
dynamically generate them from information already carried in the header,
rather than requiring that they be explicitly passed as header parameters?
Do we want to add AES ECB as a (non-authenticated) key wrap algorithm?
Is there any problem with doing key wrap without an integrity check,
given that a separate integrity check already covers the wrapped key?
Do we want to add the ability to perform symmetric encryption
directly with a shared key, without using a CMK?
This would save space and time in the single recipient case.
It would also be parallel to the current treatment of key agreement,
which doesn't use a CMK.
Secure Hash Standard (SHS)
National Institute of Standards and
Technology
Digital Signature Standard (DSS)
National Institute of Standards and
Technology
Advanced Encryption Standard (AES)
National Institute of Standards and Technology (NIST)
Recommendation for Block Cipher Modes of Operation
National Institute of Standards and Technology (NIST)
Recommendation for Block Cipher Modes of Operation:
Galois/Counter Mode (GCM) and GMAC
National Institute of Standards and Technology (NIST)
Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography (Revised)
National Institute of Standards and Technology (NIST)
JSON Web Signature (JWS)
Microsoft
mbj@microsoft.com
http://self-issued.info/
Ping Identity
ve7jtb@ve7jtb.com
Nomura Research Institute
n-sakimura@nri.co.jp
JSON Web Encryption (JWE)
Microsoft
mbj@microsoft.com
http://self-issued.info/
RTFM, Inc.
ekr@rtfm.com
Cisco Systems, Inc.
jhildebr@cisco.com
JSON Web Key (JWK)
Microsoft
mbj@microsoft.com
http://self-issued.info/
Coded Character Set -- 7-bit American Standard Code for Information Interchange
American National Standards Institute
Magic Signatures
JSON Simple Sign
independent
Nomura Research Institute
JSON Simple Encryption
independent
Nomura Research Institute
Canvas Applications
Java Cryptography Architecture
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,
XML DSIG 2.0,
and Java Cryptography Architecture
for more information about the names defined by those
documents.
Algorithm
JWS
XML DSIG
JCA
OID
HMAC using SHA-256 hash algorithm
HS256
http://www.w3.org/2001/04/xmldsig-more#hmac-sha256
HmacSHA256
1.2.840.113549.2.9
HMAC using SHA-384 hash algorithm
HS384
http://www.w3.org/2001/04/xmldsig-more#hmac-sha384
HmacSHA384
1.2.840.113549.2.10
HMAC using SHA-512 hash algorithm
HS512
http://www.w3.org/2001/04/xmldsig-more#hmac-sha512
HmacSHA512
1.2.840.113549.2.11
RSASSA using SHA-256 hash algorithm
RS256
http://www.w3.org/2001/04/xmldsig-more#rsa-sha256
SHA256withRSA
1.2.840.113549.1.1.11
RSASSA using SHA-384 hash algorithm
RS384
http://www.w3.org/2001/04/xmldsig-more#rsa-sha384
SHA384withRSA
1.2.840.113549.1.1.12
RSASSA using SHA-512 hash algorithm
RS512
http://www.w3.org/2001/04/xmldsig-more#rsa-sha512
SHA512withRSA
1.2.840.113549.1.1.13
ECDSA using P-256 curve and SHA-256 hash algorithm
ES256
http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256
SHA256withECDSA
1.2.840.10045.4.3.2
ECDSA using P-384 curve and SHA-384 hash algorithm
ES384
http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384
SHA384withECDSA
1.2.840.10045.4.3.3
ECDSA using P-521 curve and SHA-512 hash algorithm
ES512
http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512
SHA512withECDSA
1.2.840.10045.4.3.4
This appendix contains a table cross-referencing the alg (algorithm) and enc (encryption method)
values used in this specification with the equivalent
identifiers used by other standards and software packages.
See
XML Encryption,
XML Encryption 1.1,
and Java Cryptography Architecture for more
information about the names defined by those documents.
Algorithm
JWE
XML ENC
JCA
RSAES-PKCS1-V1_5
RSA1_5
http://www.w3.org/2001/04/xmlenc#rsa-1_5
RSA/None/PKCS1Padding
RSAES using Optimal Asymmetric Encryption Padding (OAEP)
RSA-OAEP
http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p
RSA/None/OAEPWithSHA-1AndMGF1Padding
Elliptic Curve Diffie-Hellman Ephemeral Static
ECDH-ES
http://www.w3.org/2009/xmlenc11#ECDH-ES
Advanced Encryption Standard (AES) Key Wrap Algorithm
using 128 bit keys
A128KW
http://www.w3.org/2001/04/xmlenc#kw-aes128
AES Key Wrap Algorithm
using 256 bit keys
A256KW
http://www.w3.org/2001/04/xmlenc#kw-aes256
AES in Cipher Block Chaining (CBC) mode with PKCS #5 padding
using 128 bit keys
A128CBC
http://www.w3.org/2001/04/xmlenc#aes128-cbc
AES/CBC/PKCS5Padding
AES in CBC mode with PKCS #5 padding
using 256 bit keys
A256CBC
http://www.w3.org/2001/04/xmlenc#aes256-cbc
AES/CBC/PKCS5Padding
AES in Galois/Counter Mode (GCM)
using 128 bit keys
A128GCM
http://www.w3.org/2009/xmlenc11#aes128-gcm
AES/GCM/NoPadding
AES GCM
using 256 bit keys
A256GCM
http://www.w3.org/2009/xmlenc11#aes256-gcm
AES/GCM/NoPadding
Solutions for signing and encrypting JSON content were
previously explored by Magic
Signatures, JSON Simple Sign,
Canvas Applications, JSON Simple Encryption, and JavaScript Message Security
Format, all of which influenced this draft. Dirk
Balfanz, John Bradley, Yaron Y. Goland, John Panzer, Nat
Sakimura, and Paul Tarjan all made significant contributions
to the design of this specification and its related
specifications.
[[ to be removed by the RFC editor before publication as an RFC ]]
-04
Added text requiring that any leading zero bytes be retained in
base64url encoded key value representations for fixed-length values.
Added this language to Registration Templates:
"This name is case sensitive. Names that match other registered names
in a case insensitive manner SHOULD NOT be accepted."
Described additional open issues.
Applied editorial suggestions.
-03
Always use a 128 bit "authentication tag" size for
AES GCM, regardless of the key size.
Specified that use of a 128 bit IV is REQUIRED with AES CBC.
It was previously RECOMMENDED.
Removed key size language for ECDSA algorithms, since the
key size is implied by the algorithm being used.
Stated that the int key size
must be the same as the hash output size (and not larger,
as was previously allowed) so that its size is defined for
key generation purposes.
Added the kdf (key derivation function) header parameter
to provide crypto agility for key derivation.
The default KDF remains the Concat KDF with the SHA-256 digest function.
Clarified that the mod and
exp values are unsigned.
Added Implementation Requirements columns to algorithm tables
and Implementation Requirements entries to algorithm registries.
Changed AES Key Wrap to RECOMMENDED.
Moved registries
JSON Web Signature and Encryption Header Parameters and
JSON Web Signature and Encryption Type Values
to the JWS specification.
Moved JSON Web Key Parameters registry to the JWK specification.
Changed registration requirements from RFC Required to
Specification Required with Expert Review.
Added Registration Template sections for defined registries.
Added Registry Contents sections to populate registry values.
No longer say "the UTF-8 representation of the JWS Secured Input
(which is the same as the ASCII representation)". Just call it
"the ASCII representation of the JWS Secured Input".
Added "Collision Resistant Namespace" to the terminology section.
Numerous editorial improvements.
-02
For AES GCM,
use the "additional authenticated data" parameter
to provide integrity for the header, encrypted key, and
ciphertext and use the resulting "authentication tag"
value as the JWE Integrity Value.
Defined minimum required key sizes for algorithms
without specified key sizes.
Defined KDF output key sizes.
Specified the use of PKCS #5 padding with AES-CBC.
Generalized text to allow key agreement to be employed
as an alternative to key wrapping or key encryption.
Clarified that ECDH-ES is a key agreement algorithm.
Required implementation of AES-128-KW and AES-256-KW.
Removed the use of A128GCM and
A256GCM for key wrapping.
Removed A512KW since it turns
out that it's not a standard algorithm.
Clarified the relationship between
typ header parameter values
and MIME types.
Generalized language to refer to Message Authentication Codes (MACs)
rather than Hash-based Message Authentication Codes (HMACs)
unless in a context specific to HMAC algorithms.
Established registries:
JSON Web Signature and Encryption Header Parameters,
JSON Web Signature and Encryption Algorithms,
JSON Web Signature and Encryption "typ" Values,
JSON Web Key Parameters, and
JSON Web Key Algorithm Families.
Moved algorithm-specific definitions from JWK to JWA.
Reformatted to give each member definition its own section heading.
-01
Moved definition of "alg":"none" for JWSs here from the JWT
specification since this functionality is likely to be
useful in more contexts that just for JWTs.
Added Advanced Encryption Standard (AES) Key Wrap Algorithm
using 512 bit keys (A512KW).
Added text "Alternatively, the Encoded JWS Signature MAY be base64url
decoded to produce the JWS Signature and this value can
be compared with the computed HMAC value, as this
comparison produces the same result as comparing the
encoded values".
Corrected the Magic Signatures reference.
Made other editorial improvements suggested by JOSE
working group participants.
-00
Created the initial IETF draft based upon
draft-jones-json-web-signature-04 and
draft-jones-json-web-encryption-02 with no normative changes.
Changed terminology to no longer call both digital
signatures and HMACs "signatures".