JSON Web Signature (JWS)Microsoftmbj@microsoft.comhttp://self-issued.info/Ping Identityve7jtb@ve7jtb.comhttp://www.thread-safe.com/Nomura Research Instituten-sakimura@nri.co.jphttp://nat.sakimura.org/
Security
JOSE Working GroupJavaScript Object NotationJSONJSON Object Signing and EncryptionJOSEJSON Web SignatureJWSJSON Web EncryptionJWEJSON Web KeyJWKJSON Web AlgorithmsJWA
JSON Web Signature (JWS) represents
content secured with digital signatures or
Message Authentication Codes (MACs)
using JSON-based data structures.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate
JSON Web Algorithms (JWA) specification
and an IANA registry defined by that specification.
Related encryption capabilities are described in the separate
JSON Web Encryption (JWE) specification.
JSON Web Signature (JWS) represents
content secured with digital signatures or
Message Authentication Codes (MACs)
using JSON-based
data structures.
The JWS cryptographic mechanisms provide integrity protection for
an arbitrary sequence of octets.
See for a discussion on
the differences between digital signatures and MACs.
Two closely related serializations for JWSs are defined.
The JWS Compact Serialization is a compact, URL-safe representation
intended for space-constrained environments such as HTTP
Authorization headers and URI query parameters.
The JWS JSON Serialization represents JWSs as JSON objects and
enables multiple signatures and/or MACs to be applied to the same content.
Both share the same cryptographic underpinnings.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate
JSON Web Algorithms (JWA) specification
and an IANA registry defined by that specification.
Related encryption capabilities are described in the separate
JSON Web Encryption (JWE) specification.
Names defined by this specification are short because a core goal is
for the resulting representations to be compact.
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" .
The interpretation should only be applied when the terms appear in all capital
letters.
BASE64URL(OCTETS) denotes the base64url encoding of OCTETS,
per .
UTF8(STRING) denotes the octets of the
UTF-8 representation of STRING,
where STRING is a sequence of zero or more Unicode characters.
ASCII(STRING) denotes the octets of the
ASCII representation of STRING,
where STRING is a sequence of zero or more ASCII characters.
The concatenation of two values A and B
is denoted as A || B.
These terms are defined by this specification:
A data structure representing a digitally signed or MACed message.
JSON object containing the parameters
describing the cryptographic operations and parameters employed.
The JOSE (JSON Object Signing and Encryption) Header is comprised
of a set of Header Parameters.
The sequence of octets to be secured -- a.k.a. the message.
The payload can contain an arbitrary sequence of octets.
Digital signature or MAC over
the JWS Protected Header and the JWS Payload.
A name/value pair that is member of the JOSE Header.
JSON object that contains the Header Parameters that are
integrity protected by
the JWS Signature digital signature or MAC operation.
For the JWS Compact Serialization, this comprises the entire JOSE Header.
For the JWS JSON Serialization, this is one component of the JOSE Header.
JSON object that contains the Header Parameters that are not
integrity protected.
This can only be present when using the JWS JSON Serialization.
Base64 encoding using the URL- and filename-safe
character set defined in Section 5 of RFC 4648,
with all trailing '=' characters omitted (as permitted by Section 3.2)
and without the inclusion of any line breaks, whitespace, or other additional characters.
Note that the base64url encoding of the empty octet sequence
is the empty string.
(See for notes on
implementing base64url encoding without padding.)
The input to the digital signature or MAC computation.
Its value is
ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload)).
A representation of the JWS as a compact, URL-safe string.
A representation of the JWS as a JSON object.
Unlike the JWS Compact Serialization,
the JWS JSON Serialization
enables multiple digital signatures and/or MACs to
be applied to the same content.
This representation is neither optimized for compactness nor URL-safe.
A JWS that provides no integrity protection.
Unsecured JWSs use the alg
value none.
A name in a namespace that enables names to be allocated in a manner
such that they are highly unlikely to collide with other names.
Examples of collision-resistant namespaces include:
Domain Names,
Object Identifiers (OIDs) as defined in the ITU-T X.660
and X.670 Recommendation series, and
Universally Unique IDentifiers (UUIDs)
.
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.
A JSON string value, with the additional requirement that
while arbitrary string values MAY be used, any value
containing a ":" character MUST be a URI
.
StringOrURI values are compared as case-sensitive strings
with no transformations or canonicalizations applied.
The terms "JSON Web Encryption (JWE)",
"JWE Compact Serialization",
and "JWE JSON Serialization" are defined by
the JWE specification .
The terms "Digital Signature"
and "Message Authentication Code (MAC)" are defined by
the "Internet Security Glossary, Version 2".
JWS represents digitally signed or MACed content using JSON data
structures and base64url encoding.
These JSON data structures MAY contain whitespace and/or line breaks
before or after any JSON values or structural characters,
in accordance with Section 2 of RFC 7159.
A JWS represents these logical values
(each of which is defined in ):
JOSE HeaderJWS PayloadJWS Signature
For a JWS,
the JOSE Header members are the union of the members of these values
(each of which is defined in ):
JWS Protected HeaderJWS Unprotected Header
This document defines two serializations for JWSs:
a compact, URL-safe serialization called the JWS Compact Serialization
and a JSON serialization called the JWS JSON Serialization.
In both serializations, the
JWS Protected Header,
JWS Payload, and
JWS Signature
are base64url encoded,
since JSON lacks a way to directly represent arbitrary octet sequences.
In the JWS Compact Serialization, no JWS Unprotected Header is used.
In this case, the JOSE Header and the JWS Protected Header are the same.
In the JWS Compact Serialization, a JWS is represented as the
concatenation:
BASE64URL(UTF8(JWS Protected Header)) || '.' ||BASE64URL(JWS Payload) || '.' ||BASE64URL(JWS Signature)
See for more information
about the JWS Compact Serialization.
In the JWS JSON Serialization, one or both of the JWS Protected Header
and JWS Unprotected Header MUST be present.
In this case, the members of the JOSE Header are the union of
the members of the JWS Protected Header and the JWS Unprotected Header
values that are present.
In the JWS JSON Serialization, a JWS is represented as a JSON object
containing some or all of these four members:
protected, with the value BASE64URL(UTF8(JWS Protected Header))header, with the value JWS Unprotected Headerpayload, with the value BASE64URL(JWS Payload)signature, with the value
BASE64URL(JWS Signature)
The three base64url-encoded result strings
and the JWS Unprotected Header value
are represented as members within a JSON object.
The inclusion of some of these values is OPTIONAL.
The JWS JSON Serialization can also represent
multiple signature and/or MAC values, rather than just one.
See for more information
about the JWS JSON Serialization.
This section provides an example of a JWS.
Its computation is described in more detail in ,
including specifying the exact octet sequences representing the JSON values used
and the key value used.
The following example JWS Protected Header declares that the
encoded object is a JSON Web Token
and the JWS Protected Header and the JWS Payload are
secured using the HMAC SHA-256
algorithm:
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The UTF-8 representation of the following JSON object is used as the JWS Payload.
(Note that the payload can be any
content and need not be a representation of a JSON object.)
Encoding this JWS Payload as
BASE64URL(JWS Payload) gives this value
(with line breaks for display purposes only):
Computing the HMAC of the JWS Signing Input
ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload))
with the HMAC SHA-256 algorithm
using the key specified in
and base64url-encoding the result
yields this BASE64URL(JWS Signature) value:
Concatenating these values in the order
Header.Payload.Signature with period ('.') characters between the
parts yields this complete JWS representation
using the JWS Compact Serialization
(with line breaks for display purposes only):
See for additional examples,
including examples using the JWS JSON Serialization
in Sections
and .
For a JWS,
the members of the JSON object(s) representing the JOSE Header describe the
digital signature or MAC applied to the
JWS Protected Header and the JWS Payload and optionally
additional properties of the JWS.
The Header Parameter names within the JOSE Header MUST be unique;
JWS parsers MUST either reject JWSs with duplicate Header Parameter names
or use a JSON parser that returns only the lexically last duplicate member name,
as specified in Section 15.12 ("The JSON Object") of
ECMAScript 5.1 .
Implementations are required to understand
the specific Header Parameters defined by this specification
that are designated as "MUST be understood"
and process them in the manner defined in this specification.
All other Header Parameters defined by this specification that
are not so designated MUST be ignored when not understood.
Unless listed as a critical Header Parameter, per ,
all Header Parameters not defined by this specification
MUST be ignored when not understood.
There are three classes of Header Parameter names:
Registered Header Parameter names, Public Header Parameter names,
and Private Header Parameter names.
The following Header Parameter names for use in JWSs are registered
in the IANA
"JSON Web Signature and Encryption Header Parameters" registry
established by
,
with meanings as defined in the subsections below.
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.
The alg (algorithm) Header Parameter
identifies the cryptographic algorithm used to
secure the JWS.
The JWS Signature value is not valid if the alg
value does not represent a supported algorithm or if there is not a
key for use with that algorithm associated with the
party that digitally signed or MACed the content.
alg values should either be
registered in the IANA
"JSON Web Signature and Encryption Algorithms" registry
established by
or be
a value that contains a Collision-Resistant Name.
The alg value is a case-sensitive ASCII string
containing a StringOrURI value.
This Header Parameter MUST be present
and MUST be understood and processed by implementations.
A list of defined alg values
for this use can be found
in the IANA "JSON Web Signature and Encryption Algorithms" registry
established by
;
the initial contents of this registry are the values defined in
Section 3.1 of
.
The jku (JWK Set URL)
Header Parameter is a URI that refers to a
resource for a set of JSON-encoded public keys, one of which
corresponds to the key
used to digitally sign the JWS.
The keys MUST be encoded as a JWK Set .
The protocol used to acquire the resource MUST provide
integrity protection; an HTTP GET request to retrieve the
JWK Set MUST use Transport Layer Security (TLS)
; and
the identity of the server MUST be validated, as per
Section 6 of RFC 6125.
Also, see on TLS requirements.
Use of this Header Parameter is OPTIONAL.
The jwk (JSON Web Key)
Header Parameter is the public key
that corresponds to the key
used to digitally sign the JWS.
This key is represented as a JSON Web Key .
Use of this Header Parameter is OPTIONAL.
The kid (key ID) Header Parameter
is a hint indicating which key
was used to secure the JWS.
This parameter allows originators to explicitly signal a change of
key to recipients.
The structure of the
kid value is unspecified.
Its value MUST be a case-sensitive string.
Use of this Header Parameter is OPTIONAL.
When used with a JWK, the kid
value is used to match a JWK kid
parameter value.
The x5u (X.509 URL) Header Parameter
is a URI that refers to a resource for
the X.509 public key certificate or certificate chain
corresponding to the key
used to digitally sign the JWS.
The identified resource MUST provide a representation of
the certificate or certificate chain that conforms to
RFC 5280 in PEM-encoded form,
with each certificate delimited as specified in
Section 6.1 of RFC 4945.
The certificate containing the public key
corresponding to the key
used to digitally sign the JWS
MUST be the first certificate.
This MAY be followed by additional certificates, with each
subsequent certificate being the one used to certify the
previous one.
The protocol used to acquire the resource MUST provide
integrity protection; an HTTP GET request to retrieve the
certificate MUST use TLS
; and
the identity of the server MUST be validated, as per
Section 6 of RFC 6125.
Also, see on TLS requirements.
Use of this Header Parameter is OPTIONAL.
The x5c (X.509 certificate chain)
Header Parameter contains the X.509 public key
certificate or certificate chain
corresponding to the key
used to digitally sign the JWS.
The certificate or certificate chain is represented as
a JSON array of certificate value strings.
Each string in the array is a base64-encoded
(Section 4 of -- not base64url-encoded)
DER PKIX certificate value.
The certificate containing the public key
corresponding to the key
used to digitally sign the JWS
MUST be the first certificate.
This MAY be followed by additional certificates, with each
subsequent certificate being the one used to certify the
previous one.
The recipient MUST validate the certificate chain according
to RFC 5280 and
consider the certificate or certificate chain to be invalid if any
validation failure occurs.
Use of this Header Parameter is OPTIONAL.
See for an example
x5c value.
The x5t (X.509 certificate SHA-1 thumbprint)
Header Parameter is a base64url-encoded
SHA-1 thumbprint (a.k.a. digest) of the DER encoding of
the X.509 certificate
corresponding to the key
used to digitally sign the JWS.
Note that certificate thumbprints are also sometimes known as certificate fingerprints.
Use of this Header Parameter is OPTIONAL.
The x5t#S256 (X.509 certificate SHA-256 thumbprint)
Header Parameter is a base64url-encoded
SHA-256 thumbprint (a.k.a. digest) of the DER encoding of
the X.509 certificate
corresponding to the key
used to digitally sign the JWS.
Note that certificate thumbprints are also sometimes known as certificate fingerprints.
Use of this Header Parameter is OPTIONAL.
The typ (type) Header Parameter
is used by JWS applications to declare the
media type
of this complete JWS.
This is intended for use by the application when
more than one kind of object could be present in
an application data structure that can contain a JWS;
the application can use this value to disambiguate among
the different kinds of objects that might be present.
It will typically not be used by applications when
the kind of object is already known.
This parameter is ignored by JWS implementations;
any processing of this parameter is performed by the JWS application.
Use of this Header Parameter is OPTIONAL.
Per RFC 2045, all media type values,
subtype values, and parameter names are case insensitive.
However, parameter values are case sensitive unless
otherwise specified for the specific parameter.
To keep messages compact in common situations,
it is RECOMMENDED that producers omit an "application/" prefix
of a media type value in a typ
Header Parameter when no other '/' appears in the media type value.
A recipient using the media type value MUST treat it as if
"application/" were prepended to any
typ value not containing a '/'.
For instance, a typ value of
example SHOULD be used to represent
the application/example media type,
whereas the media type
application/example;part="1/2" cannot
be shortened to example;part="1/2".
The typ value
JOSE can be used by applications
to indicate that this object is a JWS or JWE using
the JWS Compact Serialization or the JWE Compact Serialization.
The typ value
JOSE+JSON can be used by applications
to indicate that this object is a JWS or JWE using
the JWS JSON Serialization or the JWE JSON Serialization.
Other type values can also be used by applications.
The cty (content type) Header Parameter
is used by JWS applications to declare the
media type
of the secured content (the payload).
This is intended for use by the application when
more than one kind of object could be present in
the JWS Payload;
the application can use this value to disambiguate among
the different kinds of objects that might be present.
It will typically not be used by applications when
the kind of object is already known.
This parameter is ignored by JWS implementations;
any processing of this parameter is performed by the JWS application.
Use of this Header Parameter is OPTIONAL.
Per RFC 2045, all media type values,
subtype values, and parameter names are case insensitive.
However, parameter values are case sensitive unless
otherwise specified for the specific parameter.
To keep messages compact in common situations,
it is RECOMMENDED that producers omit an "application/" prefix
of a media type value in a cty
Header Parameter when no other '/' appears in the media type value.
A recipient using the media type value MUST treat it as if
"application/" were prepended to any
cty value not containing a '/'.
For instance, a cty value of
example SHOULD be used to represent
the application/example media type,
whereas the media type
application/example;part="1/2" cannot
be shortened to example;part="1/2".
The crit (critical) Header Parameter
indicates that extensions to
this specification and/or are being used
that MUST be understood and processed.
Its value is an array listing the Header Parameter names
present in the JOSE Header that use those extensions.
If any of the listed extension Header Parameters are not
understood and supported by the recipient, then the JWS is invalid.
Producers MUST NOT include Header Parameter names defined by
this specification or for use with JWS,
duplicate names, or
names that do not occur as Header Parameter names within the JOSE Header
in the crit list.
Producers MUST NOT use the empty list []
as the crit value.
Recipients MAY consider the JWS to be invalid if the critical list
contains any Header Parameter names defined by
this specification or for use with JWS
or if any other constraints on its use are violated.
When used, this Header Parameter MUST be integrity protected;
therefore, it MUST occur only within the JWS Protected Header.
Use of this Header Parameter is OPTIONAL.
This Header Parameter MUST be understood and processed by implementations.
Additional Header Parameter names can be defined by those
using JWSs. However, in order to prevent collisions, any new
Header Parameter name should either be registered in the IANA
"JSON Web Signature and Encryption Header Parameters" registry
established by
or be a Public Name
(a value that contains a Collision-Resistant Name).
In each case, the definer of the name
or value needs to take reasonable precautions to make sure they
are in control of the part of the namespace they use to
define the Header Parameter name.
New Header Parameters should be introduced sparingly, as
they can result in non-interoperable JWSs.
A producer and consumer of a JWS may agree to use Header Parameter names
that are Private Names (names that are
not Registered Header Parameter names ())
or Public Header Parameter names ().
Unlike Public Header Parameter names,
Private Header Parameter names are subject to collision and
should be used with caution.
To create a JWS, the following steps are performed.
The order of the steps is not significant in cases where
there are no dependencies between the inputs and outputs of the steps.
Create the content to be used as the JWS Payload.
Compute the encoded payload value BASE64URL(JWS Payload).
Create the JSON object(s) containing the desired set of Header Parameters,
which together comprise the JOSE Header
(the JWS Protected Header and/or the JWS Unprotected Header).
Compute the encoded header value BASE64URL(UTF8(JWS Protected Header)).
If the JWS Protected Header is not present
(which can only happen when using the JWS JSON Serialization
and no protected member is present),
let this value be the empty string.
Compute the JWS Signature in the manner defined for
the particular algorithm being used over the JWS Signing Input
ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload)).
The alg (algorithm) Header Parameter MUST be
present in the JOSE Header, with the algorithm value
accurately representing the algorithm used to construct
the JWS Signature.
Compute the encoded signature value BASE64URL(JWS Signature).
If the JWS JSON Serialization is being used, repeat this process
(steps 3-6)
for each digital signature or MAC operation being performed.
Create the desired serialized output.
The JWS Compact Serialization of this result is
BASE64URL(UTF8(JWS Protected Header))
|| '.' || BASE64URL(JWS Payload)
|| '.' || BASE64URL(JWS Signature).
The JWS JSON Serialization is described in .
When validating a JWS, the following steps are performed.
The order of the steps is not significant in cases where
there are no dependencies between the inputs and outputs of the steps.
If any of the listed steps fails, then the signature or MAC cannot be validated.
When there are multiple JWS Signature values,
it is an application decision which of the JWS Signature values
must successfully validate for the JWS to be accepted.
In some cases, all must successfully validate, or the JWS will be considered invalid.
In other cases, only a specific JWS Signature value
needs to be successfully validated.
However, in all cases, at least one JWS Signature value
MUST successfully validate, or the JWS MUST be considered invalid.
Parse the JWS representation to extract the serialized values
for the components of the JWS.
When using the JWS Compact Serialization,
these components are
the base64url-encoded representations of
the JWS Protected Header,
the JWS Payload, and
the JWS Signature,
and when using the JWS JSON Serialization,
these components also include the unencoded JWS Unprotected Header value.
When using the JWS Compact Serialization,
the JWS Protected Header,
the JWS Payload, and
the JWS Signature
are represented as base64url-encoded values in that order,
with each value being separated from the next by a single period ('.') character,
resulting in exactly two delimiting period characters being used.
The JWS JSON Serialization
is described in .
Base64url-decode the encoded representation of the
JWS Protected Header,
following the restriction that no line breaks, whitespace, or
other additional characters have been used.
Verify that the resulting octet sequence
is a UTF-8-encoded representation of
a completely valid JSON object
conforming to RFC 7159;
let the JWS Protected Header be this JSON object.
If using the JWS Compact Serialization, let the JOSE Header be the
JWS Protected Header.
Otherwise, when using the JWS JSON Serialization,
let the JOSE Header be the union of
the members of the corresponding JWS Protected Header
and JWS Unprotected Header,
all of which must be completely valid JSON objects.
During this step,
verify that the resulting JOSE Header does not contain duplicate
Header Parameter names.
When using the JWS JSON Serialization, this restriction includes
that the same Header Parameter name also MUST NOT occur in
distinct JSON object values that together comprise the JOSE Header.
Verify that the implementation understands and can process
all fields that it is required to support,
whether required by this specification,
by the algorithm being used,
or by the crit Header Parameter value,
and that the values of those parameters are also understood and supported.
Base64url-decode the encoded representation of the
JWS Payload,
following the restriction that no line breaks, whitespace, or other additional characters have been used.
Base64url-decode the encoded representation of the
JWS Signature,
following the restriction that no line breaks, whitespace, or other additional characters have been used.
Validate the JWS Signature
against the JWS Signing Input
ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload))
in the manner defined for the algorithm being used, which
MUST be accurately represented by the value of the alg (algorithm)
Header Parameter, which MUST be present.
See for security considerations on algorithm validation.
Record whether the validation succeeded or not.
If the JWS JSON Serialization is being used, repeat this process
(steps 4-8)
for each digital signature or MAC value contained in the representation.
If none of the validations in step 9
succeeded, then the JWS MUST be considered invalid.
Otherwise, in the JWS JSON Serialization case, return a result to the application
indicating which of the validations succeeded and failed.
In the JWS Compact Serialization case, the result
can simply indicate whether or not the JWS was successfully validated.
Finally, note that it is an application decision which algorithms
may be used in a given context.
Even if a JWS can be successfully validated,
unless the algorithm(s) used in the JWS are acceptable
to the application, it SHOULD consider the JWS to be invalid.
Processing a JWS inevitably requires comparing known strings
to members and values in JSON objects. For example, in checking what the
algorithm is, the Unicode string
alg will be
checked against the member names in the JOSE Header
to see if there is a matching Header Parameter name.
The same process is then used to determine if the value
of the alg Header Parameter
represents a supported algorithm.
The JSON rules for doing member name comparison are described in
Section 8.3 of RFC 7159.
Since the only string comparison operations that are performed are
equality and inequality, the same rules can be used for comparing
both member names and member values against known strings.
These comparison rules MUST be used for all JSON string comparisons
except in cases where the definition of the member explicitly calls out that
a different comparison rule is to be used for that member value.
Only the typ and cty
member values defined in this specification do not use these comparison rules.
Some applications may include case-insensitive information in
a case-sensitive value, such as including a DNS name as part of
a kid (key ID) value.
In those cases, the application may need to define a convention
for the canonical case to use for representing the case-insensitive portions,
such as lowercasing them, if more than one party might need to
produce the same value so that they can be compared.
(However, if all other parties consume whatever value the producing party
emitted verbatim without attempting to compare it to an independently produced
value, then the case used by the producer will not matter.)
Also, see the JSON security considerations in and
the Unicode security considerations in .
It is necessary for the recipient of a JWS to be able to determine
the key that was employed for the digital signature or MAC operation.
The key employed can be identified using the
Header Parameter methods described in or can be identified
using methods that are outside the scope of this specification.
Specifically, the Header Parameters
jku,
jwk,
kid,
x5u,
x5c,
x5t,
and x5t#S256
can be used to identify the key used.
These Header Parameters MUST be integrity protected if the
information that they convey is to be utilized in a trust decision;
however, if the only information used in the trust decision is a key,
these parameters need not be integrity protected,
since changing them in a way that causes a different key to be used
will cause the validation to fail.
The producer SHOULD include sufficient information in the Header Parameters
to identify the key used, unless the application uses another means
or convention to determine the key used.
Validation of the signature or MAC fails when
the algorithm used requires a key
(which is true of all algorithms except for none) and
the key used cannot be determined.
The means of exchanging any shared symmetric keys used
is outside the scope of this specification.
Also, see for
notes on possible key selection algorithms.
JWSs use one of two serializations: the
JWS Compact Serialization
or the
JWS JSON Serialization.
Applications using this specification need to specify what serialization
and serialization features are used for that application.
For instance, applications might specify
that only the JWS JSON Serialization is used,
that only JWS JSON Serialization support for a single signature or MAC value is used,
or that support for multiple signatures and/or MAC values is used.
JWS implementations only need to implement the features needed
for the applications they are designed to support.
The JWS Compact Serialization represents digitally signed or MACed
content as a compact, URL-safe string.
This string is:
BASE64URL(UTF8(JWS Protected Header)) || '.' ||BASE64URL(JWS Payload) || '.' ||BASE64URL(JWS Signature)
Only one signature/MAC is supported by the JWS Compact Serialization
and it provides no syntax to represent a JWS Unprotected Header value.
The JWS JSON Serialization represents digitally signed or MACed
content as a JSON object.
This representation is neither optimized for compactness nor URL-safe.
Two closely related syntaxes are defined for the JWS JSON Serialization:
a fully general syntax,
with which content can be secured with more than one
digital signature and/or MAC operation,
and a flattened syntax, which is optimized for
the single digital signature or MAC case.
The following members are defined for use in
top-level JSON objects used for the
fully general JWS JSON Serialization syntax:
The payload member MUST be present and contain the value
BASE64URL(JWS Payload).
The signatures member value MUST be
an array of JSON objects.
Each object represents a signature or MAC over the JWS Payload
and the JWS Protected Header.
The following members are defined for use in
the JSON objects that are elements of
the signatures array:
The protected member MUST be present and contain the value
BASE64URL(UTF8(JWS Protected Header)) when the JWS Protected Header
value is non-empty; otherwise, it MUST be absent.
These Header Parameter values are integrity protected.
The header member MUST be present and contain the value
JWS Unprotected Header when the JWS Unprotected Header
value is non-empty; otherwise, it MUST be absent.
This value is represented as an unencoded JSON object,
rather than as a string.
These Header Parameter values are not integrity protected.
The signature member MUST be present and contain the value
BASE64URL(JWS Signature).
At least one of the
protected and
header
members MUST be present for each signature/MAC computation
so that an alg
Header Parameter value is conveyed.
Additional members can be present in both the JSON objects defined above;
if not understood by implementations encountering them, they MUST be ignored.
The Header Parameter values used when creating or validating
individual signature or MAC values are
the union of the two sets of Header Parameter values that may be present:
(1) the JWS Protected Header
represented in the protected
member of the signature/MAC's array element, and
(2) the JWS Unprotected Header
in the header
member of the signature/MAC's array element.
The union of these sets of Header Parameters comprises the JOSE Header.
The Header Parameter names in the two locations MUST be disjoint.
Each JWS Signature value is computed using the
parameters of the corresponding JOSE Header value
in the same manner as for the JWS Compact Serialization.
This has the desirable property that each
JWS Signature value represented
in the signatures array
is identical to the value
that would have been computed for the same parameter
in the JWS Compact Serialization,
provided that the JWS Protected Header value
for that signature/MAC computation
(which represents the integrity-protected Header Parameter values)
matches that used in
the JWS Compact Serialization.
See for an example
JWS using the general JWS JSON Serialization syntax.
The flattened JWS JSON Serialization syntax is based upon
the general syntax but flattens it,
optimizing it for the single digital signature/MAC case.
It flattens it by removing
the signatures member and
instead placing those members defined for use in
the signatures array
(the protected,
header, and
signature members)
in the top-level JSON object
(at the same level as the payload member).
The signatures member MUST NOT
be present when using this syntax.
Other than this syntax difference, JWS JSON Serialization objects
using the flattened syntax are processed identically to those
using the general syntax.
See for an example
JWS using the flattened JWS JSON Serialization syntax.
Implementations supporting the jku and/or
x5u Header Parameters MUST support TLS.
Which TLS version(s) ought to be implemented will vary over
time and depend on the widespread deployment and known
security vulnerabilities at the time of implementation.
At the time of this writing,
TLS version 1.2
is the most recent version.
To protect against information disclosure and tampering,
confidentiality protection MUST be applied using TLS
with a ciphersuite that provides confidentiality and
integrity protection.
See current publications by the IETF TLS working group,
including RFC 6176,
for guidance on the ciphersuites currently considered to be appropriate for use.
Also, see "Recommendations for Secure Use of
Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)"
for recommendations on improving the security of software and services using TLS.
Whenever TLS is used, the identity of the service provider encoded
in the TLS server certificate MUST be verified using the procedures
described in Section 6 of RFC 6125.
The following registration procedure is used for all the
registries established by this specification.
Values are registered on a Specification Required
basis
after a three-week review period on the jose-reg-review@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 Experts may approve registration once they are
satisfied that such a specification will be published.
Registration requests sent to the mailing list for review should use
an appropriate subject (e.g., "Request to register header parameter: example").
Within the review period, the Designated Experts 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@ietf.org mailing list) for resolution.
Criteria that should be applied by the Designated Experts includes
determining whether the proposed registration duplicates existing functionality,
whether it is likely to be of general applicability
or useful only for a single application,
and whether the registration description is clear.
IANA must only accept registry updates from the Designated Experts 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 Experts.
This specification establishes the
IANA "JSON Web Signature and Encryption Header Parameters" registry
for Header Parameter names.
The registry records the Header Parameter name
and a reference to the specification that defines it.
The same Header Parameter name can be registered multiple times,
provided that the parameter usage is compatible
between the specifications.
Different registrations of the same Header Parameter name
will typically use different
Header Parameter Usage Locations values.
The name requested (e.g., "kid").
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 Experts state that there is a compelling reason
to allow an exception.
Brief description of the Header Parameter (e.g., "Key ID").
The Header Parameter usage locations, which should be one or more of the values
JWS or
JWE.
For Standards Track RFCs, list the "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.
Reference to the document or documents that specify the parameter,
preferably including URIs that
can be used to retrieve copies of the documents.
An indication of the relevant
sections may also be included but is not required.
This section registers the Header Parameter names defined in
in this registry.
Header Parameter Name: alg
Header Parameter Description: Algorithm
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: jku
Header Parameter Description: JWK Set URL
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: jwk
Header Parameter Description: JSON Web Key
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: kid
Header Parameter Description: Key ID
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: x5u
Header Parameter Description: X.509 URL
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: x5c
Header Parameter Description: X.509 Certificate Chain
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: x5t
Header Parameter Description: X.509 Certificate SHA-1 Thumbprint
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: x5t#S256
Header Parameter Description: X.509 Certificate SHA-256 Thumbprint
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: typ
Header Parameter Description: Type
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: cty
Header Parameter Description: Content Type
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
Header Parameter Name: crit
Header Parameter Description: Critical
Header Parameter Usage Location(s): JWS
Change Controller: IESG
Specification Document(s): of RFC 7515
This section registers the
application/jose
media type
in the "Media Types" registry
in the manner described in RFC 6838,
which can be used to indicate that the content is
a JWS or JWE using
the JWS Compact Serialization or the JWE Compact
Serialization. This section also registers
the
application/jose+json
media type in the "Media Types" registry,
which can be used to indicate that the content is
a JWS or JWE using
the JWS JSON Serialization or the JWE JSON Serialization.
Type name: application
Subtype name: jose
Required parameters: n/a
Optional parameters: n/a
Encoding considerations: 8bit;
application/jose values are encoded as a
series of base64url-encoded values (some of which may be the
empty string), each separated from the next by a single period ('.') character.
Security considerations: See the Security Considerations
section of RFC 7515.
Interoperability considerations: n/a
Published specification: RFC 7515
Applications that use this media type:
OpenID Connect, Mozilla Persona, Salesforce, Google, Android,
Windows Azure, Xbox One, Amazon Web Services,
and numerous others that use JWTs
Fragment identifier considerations: n/a
Additional information:Magic number(s): n/aFile extension(s): n/aMacintosh file type code(s): n/a
Person & email address to contact for further information:
Michael B. Jones, mbj@microsoft.com
Intended usage: COMMON
Restrictions on usage: none
Author: Michael B. Jones, mbj@microsoft.com
Change Controller: IESG
Provisional registration? No
Type name: application
Subtype name: jose+json
Required parameters: n/a
Optional parameters: n/a
Encoding considerations: 8bit;
application/jose+json values are represented as a JSON Object;
UTF-8 encoding SHOULD be employed for the JSON object.
Security considerations: See the Security Considerations
section of RFC 7515
Interoperability considerations: n/a
Published specification: RFC 7515
Applications that use this media type:
Nimbus JOSE + JWT library
Fragment identifier considerations: n/a
Additional information:Magic number(s): n/aFile extension(s): n/aMacintosh file type code(s): n/a
Person & email address to contact for further information:
Michael B. Jones, mbj@microsoft.com
Intended usage: COMMON
Restrictions on usage: none
Author: Michael B. Jones, mbj@microsoft.com
Change Controller: IESG
Provisional registration? No
All of the security issues that are pertinent to any cryptographic application
must be addressed by JWS/JWE/JWK agents. Among these issues are protecting
the user's asymmetric private and symmetric secret keys and
employing countermeasures to various attacks.
All the security considerations in
"XML Signature
Syntax and Processing Version 2.0",
also apply to this specification, other than those that are XML specific.
Likewise, many of the best practices documented in
"XML Signature Best Practices"
also apply to this specification,
other than those that are XML specific.
Keys are only as strong as the amount of entropy used to
generate them. A minimum of 128 bits of entropy should be
used for all keys, and depending upon the application context,
more may be required.
Implementations must randomly generate public/private key pairs,
MAC keys, and padding values.
The use of inadequate pseudorandom number
generators (PRNGs) to generate cryptographic keys can result in
little or no security. An attacker may find it much easier to
reproduce the PRNG environment that produced the keys, searching the
resulting small set of possibilities rather than brute-force
searching the whole key space. The generation of quality random
numbers is difficult.
RFC 4086 offers important guidance in
this area.
Implementations must protect the signer's private key. Compromise of
the signer's private key permits an attacker to masquerade as the signer.
Implementations must protect the MAC key.
Compromise of the MAC key may result in undetectable
modification of the authenticated content.
The key management technique employed to obtain public keys
must authenticate the origin of the key;
otherwise, it is unknown what party signed the message.
Likewise, the key management technique employed to distribute MAC
keys must provide data origin authentication;
otherwise, the contents are delivered with integrity from an unknown
source.
See Section 8.1 of for security considerations on
cryptographic agility.
While MACs and digital signatures can both 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.
Validation of a MAC only provides corroboration that the message
was generated by one of the parties that knows the symmetric MAC key.
This means that origination can only be determined if a MAC key is known only
to two entities and the recipient knows that it did not create the message.
MAC validation cannot be used to prove origination to a third party.
The digital signature representations for some algorithms include
information about the algorithm used inside the signature value.
For instance, signatures produced with RSASSA-PKCS1-v1_5
encode the hash function used, and many libraries
actually use the hash algorithm specified inside the signature
when validating the signature.
When using such libraries, as part of the algorithm validation
performed, implementations MUST ensure
that the algorithm information encoded in the signature
corresponds to that specified with the
alg Header Parameter.
If this is not done, an attacker could claim to have used
a strong hash algorithm while actually using a weak one
represented in the signature value.
In some usages of JWS, there is a risk of algorithm substitution attacks,
in which an attacker can use an existing digital signature value with a different
signature algorithm to make it appear that a signer has signed something
that it has not. These attacks have been discussed in detail in the
context of Cryptographic Message Syntax (CMS) .
This risk arises when all of the following are true:
Verifiers of a signature support multiple algorithms.
Given an existing signature, an attacker can find another payload
that produces the same signature value with a different algorithm.
The payload crafted by the attacker is valid in the application context.
There are several ways for an application to mitigate algorithm substitution attacks:
Use only digital signature algorithms that are not vulnerable to substitution attacks.
Substitution attacks are only feasible if an attacker can compute
pre-images for a hash function accepted by the recipient.
All JWA-defined signature algorithms use SHA-2 hashes, for which there are
no known pre-image attacks, as of the time of this writing.
Require that the alg Header Parameter be
carried in the JWS Protected Header.
(This is always the case when using the JWS Compact Serialization
and is the approach taken by CMS .)
Include a field containing the algorithm in the application payload,
and require that it be matched with the alg
Header Parameter during verification.
(This is the approach taken by PKIX .)
Creators of JWSs should not allow third parties to insert
arbitrary content into the message without adding entropy
not controlled by the third party.
When cryptographic algorithms are implemented in such a way
that successful operations take a different amount of time
than unsuccessful operations, attackers may be able to
use the time difference to obtain information about the keys
employed. Therefore, such timing differences must be avoided.
While not directly in scope for this specification, note that
applications using JWS (or JWE) objects can thwart replay attacks
by including a unique message identifier as integrity-protected content
in the JWS (or JWE) message and having the recipient verify that
the message has not been previously received or acted upon.
A SHA-1 hash is used when computing
x5t (X.509 certificate SHA-1 thumbprint) values,
for compatibility reasons. Should an effective means of producing
SHA-1 hash collisions be developed and should an attacker wish to
interfere with the use of a known certificate on a given system,
this could be accomplished by creating another certificate whose
SHA-1 hash value is the same and adding it to the certificate
store used by the intended victim. A prerequisite to this
attack succeeding is the attacker having write access to the
intended victim's certificate store.
Alternatively, the x5t#S256
(X.509 certificate SHA-256 thumbprint) Header Parameter
could be used instead of x5t.
However, at the time of this writing, no development platform
is known to support SHA-256 certificate thumbprints.
Strict JSON validation is a security requirement.
If malformed JSON is received, then the intent of the producer
is impossible to reliably discern.
Ambiguous and potentially exploitable situations could arise
if the JSON parser used does not reject malformed JSON syntax.
In particular, any JSON inputs not conforming to the JSON-text syntax
defined in RFC 7159 MUST be rejected in their entirety by JSON parsers.
Section 4 of "The JavaScript Object Notation (JSON) Data Interchange Format"
states, "The names
within an object SHOULD be unique", whereas this specification states that
The Header Parameter names within the JOSE Header MUST be unique;
JWS parsers MUST either reject JWSs with duplicate Header Parameter
names
or use a JSON parser that returns only the lexically last duplicate
member name,
as specified in Section 15.12 ("The JSON Object") of
ECMAScript 5.1 .
Thus, this specification requires that the "SHOULD" in Section 4 of
be treated as a "MUST" by producers
and that it be either treated as a "MUST" or treated in the manner specified in
ECMAScript 5.1 by consumers.
Ambiguous and potentially exploitable situations could arise
if the JSON parser used does not enforce the uniqueness of member names
or returns an unpredictable value for duplicate member names.
Some JSON parsers might not reject input that contains extra
significant characters after a valid input. For instance,
the input {"tag":"value"}ABCD
contains a valid JSON-text object followed by
the extra characters ABCD.
Implementations MUST consider JWSs containing such input to be invalid.
Header Parameter names and algorithm names are Unicode strings. For
security reasons, the representations of these names must be
compared verbatim after performing any escape processing (as
per Section 8.3 of RFC 7159).
This means, for instance, that these JSON strings must
compare as being equal ("sig", "\u0073ig"), whereas these
must all compare as being not equal to the first set or to
each other ("SIG", "Sig", "si\u0047").
JSON strings can contain characters outside the Unicode
Basic Multilingual Plane. For instance, the G clef
character (U+1D11E) may be represented in a JSON string as
"\uD834\uDD1E". Ideally, JWS implementations SHOULD ensure
that characters outside the Basic Multilingual Plane are
preserved and compared correctly; alternatively, if this is
not possible due to these characters exercising limitations
present in the underlying JSON implementation, then input
containing them MUST be rejected.
ASCII format for Network InterchangeUniversity California Los Angeles (UCLA)Information Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER)International Telecommunications UnionThe Unicode StandardThe Unicode ConsortiumJSON Web Key (JWK)Microsoftmbj@microsoft.comhttp://self-issued.info/JSON Web Algorithms (JWA)Microsoftmbj@microsoft.comhttp://self-issued.info/ECMAScript Language Specification, 5.1 EditionEcma InternationalMedia TypesIANAXML Signature Syntax and Processing Version 2.0XML Signature Best PracticesJSON Web Token (JWT)Microsoftmbj@microsoft.comhttp://self-issued.info/Ping Identityve7jtb@ve7jtb.comhttp://www.thread-safe.com/Nomura Research Instituten-sakimura@nri.co.jphttp://nat.sakimura.org/Secure Hash Standard (SHS)National Institute of Standards and
TechnologyMagic SignaturesJSON Simple SignindependentNomura Research InstituteCanvas ApplicationsFacebook
JSON Web Encryption (JWE)Microsoftmbj@microsoft.comhttp://self-issued.info/Cisco Systems, Inc.jhildebr@cisco.com
This section provides several examples of JWSs.
While the first three
examples all represent JSON Web Tokens (JWTs) , the payload can be any
octet sequence, as shown in .
The following example JWS Protected Header declares that the
data structure is a JWT
and the JWS Signing Input is secured using
the HMAC SHA-256 algorithm.
To remove potential ambiguities in the representation of the JSON object above,
the actual octet sequence representing UTF8(JWS Protected Header) used in this example
is also included below.
(Note that ambiguities can arise due to
differing platform representations of line breaks (CRLF versus LF),
differing spacing at the beginning and ends of lines,
whether the last line has a terminating line break or not,
and other causes.
In the representation used in this example,
the first line has no leading or trailing spaces,
a CRLF line break (13, 10) occurs between the first and second lines,
the second line has one leading space (32) and no trailing spaces,
and the last line does not have a terminating line break.)
The octets representing UTF8(JWS Protected Header) in this example
(using JSON array notation) are:
[123, 34, 116, 121, 112, 34, 58, 34, 74, 87, 84, 34, 44, 13, 10, 32, 34, 97, 108, 103, 34, 58, 34, 72, 83, 50, 53, 54, 34, 125]
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The JWS Payload used in this example
is the octets of the UTF-8 representation of the JSON object below.
(Note that the payload can be any base64url-encoded octet
sequence and need not be a base64url-encoded JSON
object.)
The following octet sequence, which is the UTF-8 representation
used in this example for the JSON object above, is the JWS Payload:
[123, 34, 105, 115, 115, 34, 58, 34, 106, 111, 101, 34, 44, 13, 10, 32, 34, 101, 120, 112, 34, 58, 49, 51, 48, 48, 56, 49, 57, 51, 56, 48, 44, 13, 10, 32, 34, 104, 116, 116, 112, 58, 47, 47, 101, 120, 97, 109, 112, 108, 101, 46, 99, 111, 109, 47, 105, 115, 95, 114, 111, 111, 116, 34, 58, 116, 114, 117, 101, 125]
Encoding this JWS Payload as BASE64URL(UTF8(JWS Payload))
gives this value
(with line breaks for display purposes only):
Combining these as
BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload)
gives this string
(with line breaks for display purposes only):
The resulting JWS Signing Input value,
which is the ASCII representation of above string,
is the following octet sequence (using JSON array notation):
[101, 121, 74, 48, 101, 88, 65, 105, 79, 105, 74, 75, 86, 49, 81, 105, 76, 65, 48, 75, 73, 67, 74, 104, 98, 71, 99, 105, 79, 105, 74, 73, 85, 122, 73, 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76, 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118, 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48, 99, 110, 86, 108, 102, 81]
HMACs are generated using keys.
This example uses the symmetric key
represented in JSON Web Key format below
(with line breaks within values for display purposes only):
Running the HMAC SHA-256 algorithm on
the JWS Signing Input
with this key yields this JWS Signature octet sequence:
[116, 24, 223, 180, 151, 153, 224, 37, 79, 250, 96, 125, 216, 173, 187, 186, 22, 212, 37, 77, 105, 214, 191, 240, 91, 88, 5, 88, 83, 132, 141, 121]
Encoding this JWS Signature as
BASE64URL(JWS Signature) gives this value:
Concatenating these values in the order
Header.Payload.Signature with period ('.') characters between the
parts yields this complete JWS representation
using the JWS Compact Serialization
(with line breaks for display purposes only):
Since the alg Header Parameter
is HS256, we validate the HMAC SHA-256
value contained in the JWS Signature.
To validate the HMAC value, we repeat the previous process
of using the correct key and
the JWS Signing Input
(which is the initial substring of the JWS Compact Serialization
representation up until but not including the second period character)
as input to the HMAC SHA-256 function
and then taking the output and determining if it matches
the JWS Signature
(which is base64url decoded from the value encoded in the JWS representation).
If it matches exactly, the HMAC has been validated.
The JWS Protected Header in this example is different
from the previous example in two ways. First, because a
different algorithm is being used, the alg value is
different. Second, for illustration purposes only, the
optional typ (type) Header Parameter is not used.
(This difference is
not related to the algorithm employed.) The
JWS Protected Header used is:
The octets representing UTF8(JWS Protected Header) in this example (using JSON array notation) are:
[123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125]
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The JWS Payload used in this example, which
follows, is the same as in the previous example. Since
the BASE64URL(JWS Payload) value will therefore be the same, its
computation is not repeated here.
Combining these as
BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload)
gives this string
(with line breaks for display purposes only):
The resulting JWS Signing Input value,
which is the ASCII representation of above string,
is the following octet sequence:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 122, 73, 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76, 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118, 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48, 99, 110, 86, 108, 102, 81]
This example uses the RSA key
represented in JSON Web Key format below
(with line breaks within values for display purposes only):
The RSA private key is then passed to the RSA
signing function, which also takes the hash type, SHA-256,
and the JWS Signing Input
as inputs. The result of the digital signature is an octet sequence,
which represents a big-endian integer. In this example, it
is:
[112, 46, 33, 137, 67, 232, 143, 209, 30, 181, 216, 45, 191, 120, 69, 243, 65, 6, 174, 27, 129, 255, 247, 115, 17, 22, 173, 209, 113, 125, 131, 101, 109, 66, 10, 253, 60, 150, 238, 221, 115, 162, 102, 62, 81, 102, 104, 123, 0, 11, 135, 34, 110, 1, 135, 237, 16, 115, 249, 69, 229, 130, 173, 252, 239, 22, 216, 90, 121, 142, 232, 198, 109, 219, 61, 184, 151, 91, 23, 208, 148, 2, 190, 237, 213, 217, 217, 112, 7, 16, 141, 178, 129, 96, 213, 248, 4, 12, 167, 68, 87, 98, 184, 31, 190, 127, 249, 217, 46, 10, 231, 111, 36, 242, 91, 51, 187, 230, 244, 74, 230, 30, 177, 4, 10, 203, 32, 4, 77, 62, 249, 18, 142, 212, 1, 48, 121, 91, 212, 189, 59, 65, 238, 202, 208, 102, 171, 101, 25, 129, 253, 228, 141, 247, 127, 55, 45, 195, 139, 159, 175, 221, 59, 239, 177, 139, 93, 163, 204, 60, 46, 176, 47, 158, 58, 65, 214, 18, 202, 173, 21, 145, 18, 115, 160, 95, 35, 185, 232, 56, 250, 175, 132, 157, 105, 132, 41, 239, 90, 30, 136, 121, 130, 54, 195, 212, 14, 96, 69, 34, 165, 68, 200, 242, 122, 122, 45, 184, 6, 99, 209, 108, 247, 202, 234, 86, 222, 64, 92, 178, 33, 90, 69, 178, 194, 85, 102, 181, 90, 193, 167, 72, 160, 112, 223, 200, 163, 42, 70, 149, 67, 208, 25, 238, 251, 71]
Encoding the signature as
BASE64URL(JWS Signature) produces this value
(with line breaks for display purposes only):
Concatenating these values in the order
Header.Payload.Signature with period ('.') characters between the
parts yields this complete JWS representation
using the JWS Compact Serialization
(with line breaks for display purposes only):
Since the alg Header Parameter
is RS256, we
validate the RSASSA-PKCS1-v1_5 SHA-256 digital signature contained in the JWS Signature.
Validating the JWS Signature is a bit different
from the previous example.
We pass the public key (n, e),
the JWS Signature
(which is base64url decoded from the value encoded in the JWS representation), and
the JWS Signing Input
(which is the initial substring of the JWS Compact Serialization
representation up until but not including the second period character)
to an RSASSA-PKCS1-v1_5 signature verifier that has
been configured to use the SHA-256 hash function.
The JWS Protected Header for this example differs from
the previous example because a different algorithm is
being used. The JWS Protected Header used is:
The octets representing UTF8(JWS Protected Header) in this example (using JSON array notation) are:
[123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125]
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The JWS Payload used in this example, which
follows, is the same as in the previous examples. Since
the BASE64URL(JWS Payload) value will therefore be the same, its
computation is not repeated here.
Combining these as
BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload)
gives this string
(with line breaks for display purposes only):
The resulting JWS Signing Input value,
which is the ASCII representation of above string,
is the following octet sequence:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 73, 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76, 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118, 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48, 99, 110, 86, 108, 102, 81]
This example uses the Elliptic Curve key
represented in JSON Web Key format below:
The Elliptic Curve Digital Signature Algorithm (ECDSA) private part d is then passed to an ECDSA
signing function, which also takes the curve type, P-256,
the hash type, SHA-256, and
the JWS Signing Input
as inputs. The result of the
digital signature is the Elliptic Curve (EC) point (R, S), where R and S are
unsigned integers. In this example, the R and S values,
given as octet sequences representing big-endian integers are:
Result NameValueR
[14, 209, 33, 83, 121, 99, 108, 72, 60, 47, 127, 21, 88, 7, 212, 2, 163, 178, 40, 3, 58, 249, 124, 126, 23, 129, 154, 195, 22, 158, 166, 101]
S
[197, 10, 7, 211, 140, 60, 112, 229, 216, 241, 45, 175, 8, 74, 84, 128, 166, 101, 144, 197, 242, 147, 80, 154, 143, 63, 127, 138, 131, 163, 84, 213]
The JWS Signature is the value R || S.
Encoding the signature as
BASE64URL(JWS Signature) produces this value
(with line breaks for display purposes only):
Concatenating these values in the order
Header.Payload.Signature with period ('.') characters between the
parts yields this complete JWS representation
using the JWS Compact Serialization
(with line breaks for display purposes only):
Since the alg Header Parameter
is ES256, we
validate the ECDSA P-256 SHA-256 digital signature contained in
the JWS Signature.
Validating the JWS Signature is a bit different
from the previous examples.
We need to split the 64 member octet sequence of the JWS Signature
(which is base64url decoded from the value encoded in the JWS representation)
into two 32 octet sequences, the first representing R and the second S. We
then pass the public key (x, y), the signature (R, S), and
the JWS Signing Input
(which is the initial substring of the JWS Compact Serialization
representation up until but not including the second period character)
to an ECDSA signature verifier that
has been configured to use the P-256 curve with the
SHA-256 hash function.
The JWS Protected Header for this example differs from
the previous example because different ECDSA curves
and hash functions are used. The JWS Protected Header used is:
The octets representing UTF8(JWS Protected Header) in this example (using JSON array notation) are:
[123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 53, 49, 50, 34, 125]
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The JWS Payload used in this example is the ASCII string "Payload".
The representation of this string is the following octet sequence:
[80, 97, 121, 108, 111, 97, 100]
Encoding this JWS Payload as
BASE64URL(JWS Payload) gives this value:
Combining these as
BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS Payload)
gives this string:
The resulting JWS Signing Input value,
which is the ASCII representation of above string,
is the following octet sequence:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 85, 120, 77, 105, 74, 57, 46, 85, 71, 70, 53, 98, 71, 57, 104, 90, 65]
This example uses the Elliptic Curve key
represented in JSON Web Key format below
(with line breaks within values for display purposes only):
The ECDSA private part d is then passed to an ECDSA
signing function, which also takes the curve type, P-521,
the hash type, SHA-512, and
the JWS Signing Input
as inputs. The result of the
digital signature is the EC point (R, S), where R and S are
unsigned integers. In this example, the R and S values,
given as octet sequences representing big-endian integers are:
Result NameValueR
[1, 220, 12, 129, 231, 171, 194, 209, 232, 135, 233, 117, 247, 105, 122, 210,
26, 125, 192, 1, 217, 21, 82, 91, 45, 240, 255, 83, 19, 34, 239, 71,
48, 157, 147, 152, 105, 18, 53, 108, 163, 214, 68, 231, 62, 153, 150, 106,
194, 164, 246, 72, 143, 138, 24, 50, 129, 223, 133, 206, 209, 172, 63, 237,
119, 109]
S
[0, 111, 6, 105, 44, 5, 41, 208, 128, 61, 152, 40, 92, 61,
152, 4, 150, 66, 60, 69, 247, 196, 170, 81, 193, 199, 78, 59, 194, 169,
16, 124, 9, 143, 42, 142, 131, 48, 206, 238, 34, 175, 83, 203, 220, 159,
3, 107, 155, 22, 27, 73, 111, 68, 68, 21, 238, 144, 229, 232, 148, 188,
222, 59, 242, 103]
The JWS Signature is the value R || S.
Encoding the signature as
BASE64URL(JWS Signature) produces this value
(with line breaks for display purposes only):
Concatenating these values in the order
Header.Payload.Signature with period ('.') characters between the
parts yields this complete JWS representation
using the JWS Compact Serialization
(with line breaks for display purposes only):
Since the alg Header Parameter
is ES512, we
validate the ECDSA P-521 SHA-512 digital signature contained in
the JWS Signature.
Validating this JWS Signature is very similar to the previous example.
We need to split the 132-member octet sequence of the JWS Signature
into two 66-octet sequences, the first representing R and the second S. We
then pass the public key (x, y), the signature (R, S), and
the JWS Signing Input
to an ECDSA signature verifier that
has been configured to use the P-521 curve with the
SHA-512 hash function.
The following example JWS Protected Header declares that the
encoded object is an Unsecured JWS:
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The JWS Payload used in this example, which
follows, is the same as in the previous examples. Since
the BASE64URL(JWS Payload) value will therefore be the same, its
computation is not repeated here.
The JWS Signature is the empty octet string
and BASE64URL(JWS Signature) is the empty string.
Concatenating these values in the order
Header.Payload.Signature with period ('.') characters between the
parts yields this complete JWS representation
using the JWS Compact Serialization
(with line breaks for display purposes only):
This section contains an example using the general JWS JSON Serialization syntax.
This example demonstrates the capability for
conveying multiple digital signatures and/or MACs for the
same payload.
The JWS Payload used in this example is the same as
that used in the examples in
and
(with line breaks for display purposes only):
Two digital signatures are used in this example:
the first using RSASSA-PKCS1-v1_5 SHA-256 and
the second using ECDSA P-256 SHA-256.
For the first, the JWS Protected Header and key
are the same as in ,
resulting in the same JWS Signature value;
therefore, its computation is not repeated here.
For the second, the JWS Protected Header and key
are the same as in ,
resulting in the same JWS Signature value;
therefore, its computation is not repeated here.
The JWS Protected Header value used for the first signature is:
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
The JWS Protected Header value used for the second signature is:
Encoding this JWS Protected Header as
BASE64URL(UTF8(JWS Protected Header)) gives this value:
Key ID values are supplied for both keys using per-signature
Header Parameters.
The two JWS Unprotected Header values used to represent these key IDs are:
and
Combining the JWS Protected Header and JWS Unprotected Header values
supplied, the JOSE Header values used for the first and second
signatures, respectively, are:
and
The complete JWS JSON Serialization
for these values is as follows
(with line breaks within values for display purposes only):
This section contains an example using the flattened JWS JSON Serialization syntax.
This example demonstrates the capability for
conveying a single digital signature or MAC
in a flattened JSON structure.
The values in this example are the same as those in the second signature
of the previous example in .
The complete JWS JSON Serialization
for these values is as follows
(with line breaks within values for display purposes only):
The JSON array below is an example of a certificate chain
that could be used as the value of an
x5c (X.509 certificate chain) Header Parameter,
per
(with line breaks within values for display purposes only):
This appendix describes how to implement base64url encoding
and decoding functions without padding based upon standard
base64 encoding and decoding functions that do use padding.
To be concrete, example C# code implementing these functions
is shown below. Similar code could be used in other
languages.
As per the example code above, the number of '=' padding
characters that needs to be added to the end of a base64url-encoded
string without padding to turn it into one with
padding is a deterministic function of the length of the
encoded string. Specifically,
if the length mod 4 is 0, no padding is added;
if the length mod 4 is 2, two '=' padding characters are added;
if the length mod 4 is 3, one '=' padding character is added;
if the length mod 4 is 1, the input is malformed.
An example correspondence between unencoded and encoded values
follows. The octet sequence below encodes into the string
below, which when decoded, reproduces the octet sequence.
This appendix describes a set of possible algorithms for selecting the key
to be used to validate the digital signature or MAC of a JWS
or for selecting the key to be used to decrypt a JWE.
This guidance describes a family of possible algorithms
rather than a single algorithm,
because in different contexts, not all the sources of keys will be used,
they can be tried in different orders,
and sometimes not all the collected keys will be tried;
hence, different algorithms will be used in different application contexts.
The steps below are described for illustration purposes only;
specific applications can and are likely to use different algorithms
or perform some of the steps in different orders.
Specific applications will frequently have a much simpler method
of determining the keys to use, as there may be one or two key selection
methods that are profiled for the application's use.
This appendix supplements the normative information on key location
in .
These algorithms include the following steps.
Note that the steps can be performed in any order
and do not need to be treated as distinct.
For example, keys can be tried as soon as they are found,
rather than collecting all the keys before trying any.
Collect the set of potentially applicable keys.
Sources of keys may include:
Keys supplied by the application protocol being used.
Keys referenced by the jku (JWK Set URL)
Header Parameter.
The key provided by the jwk (JSON Web Key)
Header Parameter.
The key referenced by the x5u (X.509 URL)
Header Parameter.
The key provided by the
x5c (X.509 certificate chain)
Header Parameter.
Other applicable keys available to the application.
The order for collecting and trying keys from different key sources
is typically application dependent.
For example, frequently, all keys from a one set of locations,
such as local caches,
will be tried before collecting and trying keys from other locations.
Filter the set of collected keys.
For instance, some applications will use only keys referenced by
kid (key ID) or
x5t (X.509 certificate SHA-1 thumbprint)
parameters.
If the application uses the JWK
alg (algorithm),
use (public key use), or
key_ops (key operations) parameters,
keys with inappropriate values of those parameters
would be excluded.
Additionally, keys might be filtered to include or exclude keys
with certain other member values in an application-specific manner.
For some applications, no filtering will be applied.
Order the set of collected keys.
For instance, keys referenced by
kid (key ID) or
x5t (X.509 certificate SHA-1 thumbprint)
parameters might be tried before keys with neither of these values.
Likewise, keys with certain member values
might be ordered before keys with other member values.
For some applications, no ordering will be applied.
Make trust decisions about the keys.
Signatures made with
keys not meeting the application's trust criteria would not be accepted.
Such criteria might include, but is not limited to,
the source of the key,
whether the TLS certificate validates for keys retrieved from URLs,
whether a key in an X.509 certificate is backed by a valid certificate chain,
and other information known by the application.
Attempt signature or MAC validation for a JWS
or decryption of a JWE with
some or all of the collected and possibly filtered and/or ordered keys.
A limit on the number of keys to be tried might be applied.
This process will normally terminate following a successful validation
or decryption.
Note that it is reasonable for some applications to perform
signature or MAC validation prior to making a trust decision about a key,
since keys for which the validation fails need no trust decision.
Conforming implementations must reject input containing critical extensions
that are not understood or cannot be processed. The following JWS must
be rejected by all implementations, because it uses an extension
Header Parameter name http://example.invalid/UNDEFINED
that they do not understand.
Any other similar input, in which the use of the value
http://example.invalid/UNDEFINED is substituted for
any other Header Parameter name not understood by the implementation,
must also be rejected.
In some contexts, it is useful to integrity-protect content that
is not itself contained in a JWS.
One way to do this is to create a JWS in the normal fashion using
a representation of the content as the payload
but then delete the payload representation from the JWS
and send this modified object to the recipient rather than the JWS.
When using the JWS Compact Serialization, the deletion is accomplished
by replacing the second field (which contains BASE64URL(JWS Payload)) value
with the empty string;
when using the JWS JSON Serialization, the deletion is accomplished
by deleting the payload member.
This method assumes that the recipient can reconstruct
the exact payload used in the JWS.
To use the modified object, the recipient reconstructs the JWS
by re-inserting the payload representation into the modified object
and uses the resulting JWS in the usual manner.
Note that this method needs no support from JWS libraries, as applications
can use this method by modifying the inputs and outputs of standard JWS libraries.
Solutions for signing JSON content were previously explored by
Magic Signatures, JSON Simple Sign, and Canvas Applications, all of which
influenced this document.
Thanks to Axel Nennker for his early implementation
and feedback on the JWS and JWE specifications.
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,
Brian Campbell,
Alissa Cooper,
Breno de Medeiros,
Stephen Farrell,
Yaron Y. Goland,
Dick Hardt,
Joe Hildebrand,
Jeff Hodges,
Russ Housley,
Edmund Jay,
Tero Kivinen,
Ben Laurie,
Ted Lemon,
James Manger,
Matt Miller,
Kathleen Moriarty,
Tony Nadalin,
Hideki Nara,
Axel Nennker,
John Panzer,
Ray Polk,
Emmanuel Raviart,
Eric Rescorla,
Pete Resnick,
Jim Schaad,
Paul Tarjan,
Hannes Tschofenig,
and Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
Sean Turner, Stephen Farrell, and Kathleen Moriarty served as Security Area Directors
during the creation of this specification.