JSON Web Encryption (JWE)Microsoftmbj@microsoft.comhttp://self-issued.info/Cisco Systems, Inc.jhildebr@cisco.com
Security
JOSE Working GroupRFCRequest for CommentsI-DInternet-DraftJavaScript Object NotationJSONJSON Object Signing and EncryptionJOSEJSON Web SignatureJWSJSON Web EncryptionJWEJSON Web KeyJWKJSON Web AlgorithmsJWA
JSON Web Encryption (JWE) represents encrypted content
using JavaScript Object Notation (JSON) based data structures.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate
JSON Web Algorithms (JWA) specification
and IANA registries defined by that specification.
Related digital signature and MAC capabilities are described
in the separate JSON Web Signature (JWS) specification.
JSON Web Encryption (JWE) represents encrypted content
using JavaScript Object Notation (JSON)
based data structures.
The JWE cryptographic mechanisms encrypt and provide integrity protection for
an arbitrary sequence of octets.
Two closely related serializations for JWE objects are defined.
The JWE Compact Serialization is a compact, URL-safe representation
intended for space constrained environments such as HTTP
Authorization headers and URI query parameters.
The JWE JSON Serialization represents JWE objects as JSON objects and
enables the same content to be encrypted to multiple parties.
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 IANA registries defined by that specification.
Related digital signature and MAC capabilities are described
in the separate JSON Web Signature (JWS)
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 .
If these words are used without being spelled in uppercase then
they are to be interpreted with their normal natural language meanings.
BASE64URL(OCTETS) denotes the base64url encoding of OCTETS,
per .
UTF8(STRING) denotes the octets of the
UTF-8 representation of STRING.
ASCII(STRING) denotes the octets of the
ASCII representation of STRING.
The concatenation of two values A and B
is denoted as A || B.
These terms defined by the
JSON Web Signature (JWS)
specification are incorporated into this specification:
"JSON Web Signature (JWS)",
"Base64url Encoding",
"Collision-Resistant Name", and
"StringOrURI".
These terms are defined for use by this specification:
A data structure representing an encrypted and integrity protected message.
An AEAD algorithm is one that encrypts the Plaintext,
allows Additional Authenticated Data to be specified,
and provides an integrated content integrity check
over the Ciphertext and Additional Authenticated Data.
AEAD algorithms accept two inputs, the Plaintext and the
Additional Authenticated Data value, and produce two outputs,
the Ciphertext and the Authentication Tag value.
AES Galois/Counter Mode (GCM) is one such algorithm.
The sequence of octets to be encrypted -- a.k.a., the message.
The plaintext can contain an arbitrary sequence of octets.
An encrypted representation of the Plaintext.
An input to an AEAD operation that
is integrity protected but not encrypted.
An output of an AEAD operation that
ensures the integrity of
the Ciphertext
and the Additional Authenticated Data.
Note that some algorithms may not use an Authentication Tag,
in which case this value is the empty octet sequence.
A symmetric key for the AEAD algorithm
used to encrypt the Plaintext for the
recipient to produce the Ciphertext and the Authentication Tag.
JSON object containing the parameters
describing the cryptographic operations and parameters employed.
The JWE Header members are the union of the members of
the JWE Protected Header,
the JWE Shared Unprotected Header, and
the JWE Per-Recipient Unprotected Header.
The members of the JWE Header are Header Parameters.
Encrypted Content Encryption Key (CEK) value.
Note that for some algorithms, the JWE Encrypted Key
value is specified as being the empty octet sequence.
Initialization Vector value used
when encrypting the plaintext.
Note that some algorithms may not use an Initialization Vector,
in which case this value is the empty octet sequence.
Additional value to be integrity protected by
the authenticated encryption operation.
This can only be present when using the JWE JSON Serialization.
(Note that this can also be achieved when using either serialization
by including the AAD value as an integrity protected Header Parameter value,
but at the cost of the value being double base64url encoded.)
Ciphertext value resulting from
authenticated encryption of the plaintext with additional authenticated data.
Authentication Tag value resulting from
authenticated encryption of the plaintext with additional authenticated data.
A name/value pair that is member of the JWE Header.
JSON object that contains the JWE Header Parameters that
are integrity protected by the authenticated encryption operation.
These parameters apply to all recipients of the JWE.
For the JWE Compact Serialization, this comprises the entire JWE Header.
For the JWE JSON Serialization, this is one component of the JWE Header.
JSON object that contains the JWE Header Parameters that
apply to all recipients of the JWE
that are not integrity protected.
This can only be present when using the JWE JSON Serialization.
JSON object that contains JWE Header Parameters that
apply to a single recipient of the JWE.
These Header Parameter values are not integrity protected.
This can only be present when using the JWE JSON Serialization.
A representation of the JWE as a compact, URL-safe string.
A representation of the JWE as a JSON object.
The JWE JSON Serialization
enables the same content to be encrypted to multiple parties.
This representation is neither optimized for compactness nor URL-safe.
A method of determining the Content Encryption Key (CEK) value to use.
Each algorithm used for determining the CEK value uses a specific Key Management Mode.
Key Management Modes employed by this specification are
Key Encryption,
Key Wrapping,
Direct Key Agreement,
Key Agreement with Key Wrapping, and
Direct Encryption.
A Key Management Mode in which the Content Encryption Key (CEK) value
is encrypted to the intended recipient using an asymmetric encryption algorithm.
A Key Management Mode in which the Content Encryption Key (CEK) value
is encrypted to the intended recipient using a symmetric key wrapping algorithm.
A Key Management Mode in which a key agreement algorithm is used to agree upon
the Content Encryption Key (CEK) value.
A Key Management Mode in which a key agreement algorithm is used to agree upon
a symmetric key used to encrypt the Content Encryption Key (CEK) value
to the intended recipient using a symmetric key wrapping algorithm.
A Key Management Mode in which the Content Encryption Key (CEK) value
used is the secret symmetric key value shared between the parties.
JWE represents encrypted content using JSON data
structures and base64url encoding.
A JWE represents these logical values:
JSON object containing the parameters
describing the cryptographic operations and parameters employed.
The JWE Header members are the union of the members of
the JWE Protected Header,
the JWE Shared Unprotected Header, and
the JWE Per-Recipient Unprotected Header, as described below.
Encrypted Content Encryption Key (CEK) value.
Initialization Vector value used
when encrypting the plaintext.
Additional value to be integrity protected by
the authenticated encryption operation.
Ciphertext value resulting from
authenticated encryption of the plaintext with additional authenticated data.
Authentication Tag value resulting from
authenticated encryption of the plaintext with additional authenticated data.
The JWE Header represents the combination of these logical values:
JSON object that contains the JWE Header Parameters that
are integrity protected by the authenticated encryption operation.
These parameters apply to all recipients of the JWE.
JSON object that contains the JWE Header Parameters that
apply to all recipients of the JWE
that are not integrity protected.
JSON object that contains JWE Header Parameters that
apply to a single recipient of the JWE.
These Header Parameter values are not integrity protected.
This document defines two serializations for JWE objects:
a compact, URL-safe serialization called the JWE Compact Serialization
and a JSON serialization called the JWE JSON Serialization.
In both serializations, the
JWE Protected Header,
JWE Encrypted Key,
JWE Initialization Vector,
JWE Ciphertext, and
JWE Authentication Tag
are base64url encoded for transmission,
since JSON lacks a way to directly represent octet sequences.
When present, the JWE AAD is also base64url encoded for transmission.
In the JWE Compact Serialization, no JWE Shared Unprotected Header or
JWE Per-Recipient Unprotected Header are used.
In this case, the JWE Header and the JWE Protected Header are the same.
In the JWE Compact Serialization, a JWE object is represented as the
combination of these five string values,
BASE64URL(UTF8(JWE Protected Header)),BASE64URL(JWE Encrypted Key),BASE64URL(JWE Initialization Vector),BASE64URL(JWE Ciphertext), andBASE64URL(JWE Authentication Tag),
concatenated in that order,
with the five strings being separated by four period ('.') characters.
In the JWE JSON Serialization, one or more of the JWE Protected Header,
JWE Shared Unprotected Header, and
JWE Per-Recipient Unprotected Header MUST be present.
In this case, the members of the JWE Header are the combination of
the members of the JWE Protected Header,
JWE Shared Unprotected Header, and
JWE Per-Recipient Unprotected Header
values that are present.
In the JWE JSON Serialization, a JWE object is represented as the
combination of these eight values,
BASE64URL(UTF8(JWE Protected Header)),JWE Shared Unprotected Header,JWE Per-Recipient Unprotected Header,BASE64URL(JWE Encrypted Key),BASE64URL(JWE Initialization Vector),BASE64URL(JWE Ciphertext),BASE64URL(JWE Authentication Tag), andBASE64URL(JWE AAD),
with the six base64url encoding result strings
and the two unprotected JSON object values
being represented as members within a JSON object.
The inclusion of some of these values is OPTIONAL.
The JWE JSON Serialization can also
encrypt the plaintext to multiple recipients.
See for more information
about the JWE JSON Serialization.
JWE utilizes authenticated encryption to ensure the confidentiality
and integrity of the Plaintext
and the integrity of the JWE Protected Header and the JWE AAD.
This example encrypts the plaintext
"The true sign of intelligence is not knowledge but imagination."
to the recipient using RSAES OAEP for key encryption
and AES GCM for content encryption.
The following example JWE Protected Header declares that:
the Content Encryption Key is encrypted to the recipient
using the RSAES OAEP algorithm to produce
the JWE Encrypted Key and
the Plaintext is encrypted using the AES GCM
algorithm with a 256 bit key to produce the Ciphertext.
Encoding this JWE Protected Header as
BASE64URL(UTF8(JWE Protected Header)) gives this value:
The remaining steps to finish creating this JWE are:
Generate a random Content Encryption Key (CEK).
Encrypt the CEK with the recipient's public key using the RSAES OAEP
algorithm to produce the JWE Encrypted Key.
Base64url encode the JWE Encrypted Key.
Generate a random JWE Initialization Vector.
Base64url encode the JWE Initialization Vector.
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))).
Encrypt the Plaintext with AES GCM
using the CEK as the encryption key,
the JWE Initialization Vector,
and the Additional Authenticated Data value,
requesting a 128 bit Authentication Tag output.
Base64url encode the Ciphertext.
Base64url encode the Authentication Tag.
Assemble the final representation:
The Compact Serialization of this result is the string
BASE64URL(UTF8(JWE Protected Header))
|| '.' || BASE64URL(JWE Encrypted Key)
|| '.' || BASE64URL(JWE Initialization Vector)
|| '.' || BASE64URL(JWE Ciphertext)
|| '.' || BASE64URL(JWE Authentication Tag).
The final result in this example
(with line breaks for display purposes only) is:
See for the complete details of computing this JWE.
See other parts of for additional examples.
The members of the JSON object(s) representing the JWE Header
describe the encryption applied to the Plaintext and optionally
additional properties of the JWE.
The Header Parameter names within the JWE Header MUST be unique;
recipients MUST either reject JWEs 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 are registered
in the IANA
JSON Web Signature and Encryption Header Parameters registry
defined in
,
with meanings as defined 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.
This parameter has the same meaning, syntax, and processing rules as the
alg Header Parameter defined in
Section 4.1.1 of , except that
the Header Parameter identifies the cryptographic algorithm used to
encrypt or determine the value of the Content Encryption Key (CEK).
The encrypted content is not usable if the alg
value does not represent a supported algorithm, or if the recipient does
not have a key that can be used with that algorithm.
A list of defined alg values
for this use can be found
in the IANA JSON Web Signature and Encryption Algorithms registry
defined in
;
the initial contents of this registry are the values defined in
Section 4.1 of the
JSON Web Algorithms (JWA) specification.
The enc (encryption algorithm)
Header Parameter identifies the content encryption algorithm
used to encrypt the Plaintext to produce the Ciphertext.
This algorithm MUST be an AEAD algorithm with a specified key length.
The recipient MUST reject the JWE if the enc
value does not represent a supported algorithm.
enc values should either be
registered in the IANA
JSON Web Signature and Encryption Algorithms registry
defined in
or be
a value that contains a Collision-Resistant Name.
The enc value is a case-sensitive string
containing a StringOrURI value.
This Header Parameter MUST be present
and MUST be understood and processed by implementations.
A list of defined enc values
for this use can be found
in the IANA JSON Web Signature and Encryption Algorithms registry
defined in
;
the initial contents of this registry are the values defined in
Section 5.1 of the
JSON Web Algorithms (JWA) specification.
The zip (compression algorithm)
applied to the Plaintext before encryption, if any.
The zip value defined by this specification is:
DEF
- Compression with the DEFLATE algorithm
Other values MAY be used.
Compression algorithm values can be registered in the IANA
JSON Web Encryption Compression Algorithm registry
defined in
.
The zip value is a case-sensitive string.
If no zip parameter is present,
no compression is applied to the Plaintext before encryption.
This Header Parameter MUST be integrity protected, and therefore
MUST occur only within the JWE Protected Header, when used.
Use of this Header Parameter is OPTIONAL.
This Header Parameter MUST be understood and processed by implementations.
This parameter has the same meaning, syntax, and processing rules as the
jku Header Parameter defined in
Section 4.1.2 of , except that
the JWK Set resource contains
the public key to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the JWE.
This parameter has the same meaning, syntax, and processing rules as the
jwk Header Parameter defined in
Section 4.1.3 of , except that
the key is
the public key to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the JWE.
This parameter has the same meaning, syntax, and processing rules as the
kid Header Parameter defined in
Section 4.1.4 of , except that
the key hint references
the public key to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the JWE.
This parameter allows originators to explicitly signal a change of
key to JWE recipients.
This parameter has the same meaning, syntax, and processing rules as the
x5u Header Parameter defined in
Section 4.1.5 of , except that
the X.509 public key certificate or certificate chain
contains the public key
to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the JWE.
This parameter has the same meaning, syntax, and processing rules as the
x5c Header Parameter defined in
Section 4.1.6 of , except that
the X.509 public key certificate or certificate chain
contains the public key
to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the JWE.
See Appendix B of for an example
x5c value.
This parameter has the same meaning, syntax, and processing rules as the
x5t Header Parameter defined in
Section 4.1.7 of , except that
certificate referenced by the thumbprint contains
the public key to which the JWE was encrypted;
this can be used to determine the private key needed to decrypt the JWE.
This parameter has the same meaning, syntax, and processing rules as the
typ Header Parameter defined in
Section 4.1.8 of , except that
the type is of this complete JWE object.
This parameter has the same meaning, syntax, and processing rules as the
cty Header Parameter defined in
Section 4.1.9 of , except that
the type is of the secured content (the plaintext).
This parameter has the same meaning, syntax, and processing rules as the
crit Header Parameter defined in
Section 4.1.10 of , except that
JWE Header Parameters are being referred to, rather than
JWS Header Parameters.
Additional Header Parameter names can be defined by those
using JWEs. 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
defined in
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 JWEs.
A producer and consumer of a JWE 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.
The message encryption process is as follows.
The order of the steps is not significant in cases where
there are no dependencies between the inputs and outputs of the steps.
Determine the Key Management Mode employed by the algorithm
used to determine the Content Encryption Key (CEK) value.
(This is the algorithm recorded in the
alg (algorithm)
Header Parameter of the resulting JWE.)
When Key Wrapping, Key Encryption,
or Key Agreement with Key Wrapping are employed,
generate a random Content Encryption Key (CEK) value.
See RFC 4086 for
considerations on generating random values.
The CEK MUST have a length equal to that
required for the content encryption algorithm.
When Direct Key Agreement or Key Agreement with Key Wrapping
are employed, use the key agreement algorithm
to compute the value of the agreed upon key.
When Direct Key Agreement is employed,
let the Content Encryption Key (CEK) be the agreed upon key.
When Key Agreement with Key Wrapping is employed,
the agreed upon key will be used to wrap the CEK.
When Key Wrapping, Key Encryption,
or Key Agreement with Key Wrapping are employed,
encrypt the CEK to the recipient and let the result be the
JWE Encrypted Key.
When Direct Key Agreement or Direct Encryption are employed,
let the JWE Encrypted Key be the empty octet sequence.
When Direct Encryption is employed,
let the Content Encryption Key (CEK) be the shared symmetric key.
Compute the encoded key value BASE64URL(JWE Encrypted Key).
If the JWE JSON Serialization is being used, repeat this process
(steps 1-7)
for each recipient.
Generate a random JWE Initialization Vector of the correct size
for the content encryption algorithm (if required for the algorithm);
otherwise, let the JWE Initialization Vector be the empty octet sequence.
Compute the encoded initialization vector value
BASE64URL(JWE Initialization Vector).
If a zip parameter was included,
compress the Plaintext using the specified compression algorithm.
Serialize the (compressed) Plaintext into an octet sequence M.
Create the JSON object(s) containing the desired set of Header Parameters,
which together comprise the JWE Header:
the JWE Protected Header, and if the JWE JSON Serialization is being used,
the JWE Shared Unprotected Header and
the JWE Per-Recipient Unprotected Header.
Compute the Encoded Protected Header value
BASE64URL(UTF8(JWE Protected Header)).
If the JWE Protected Header is not present
(which can only happen when using the JWE JSON Serialization
and no protected member is present),
let this value be the empty string.
Let the Additional Authenticated Data encryption parameter be
ASCII(Encoded Protected Header).
However if a JWE AAD value is present
(which can only be the case when using the JWE JSON Serialization),
instead let the Additional Authenticated Data encryption parameter be
ASCII(Encoded Protected Header || '.' || BASE64URL(JWE AAD)).
Encrypt M using the CEK, the JWE Initialization Vector, and
the Additional Authenticated Data value
using the specified content encryption algorithm
to create the JWE Ciphertext value and the JWE Authentication Tag
(which is the Authentication Tag output from the encryption operation).
Compute the encoded ciphertext value BASE64URL(JWE Ciphertext).
Compute the encoded authentication tag value
BASE64URL(JWE Authentication Tag).
The five encoded values are used in both the
JWE Compact Serialization and the JWE JSON Serialization representations.
If a JWE AAD value is present,
compute the encoded AAD value BASE64URL(JWE AAD).
Create the desired serialized output.
The Compact Serialization of this result is the string
BASE64URL(UTF8(JWE Protected Header))
|| '.' || BASE64URL(JWE Encrypted Key)
|| '.' || BASE64URL(JWE Initialization Vector)
|| '.' || BASE64URL(JWE Ciphertext)
|| '.' || BASE64URL(JWE Authentication Tag).
The JWE JSON Serialization is described in .
The message decryption process is the reverse of the
encryption process.
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 these steps fails, the encrypted content cannot be validated.
It is an application decision which recipients' encrypted content
must successfully validate for the JWE to be accepted.
In some cases, encrypted content for all recipients must successfully validate
or the JWE will be rejected.
In other cases, only the encrypted content for a single recipient
needs to be successfully validated.
However, in all cases, the encrypted content for at least one recipient
MUST successfully validate or the JWE MUST be rejected.
Parse the JWE representation to extract the serialized values
for the components of the JWE --
when using the JWE Compact Serialization,
the base64url encoded representations of
the JWE Protected Header,
the JWE Encrypted Key,
the JWE Initialization Vector,
the JWE Ciphertext, and
the JWE Authentication Tag,
and when using the JWE JSON Serialization,
also the base64url encoded representation of
the JWE AAD and the unencoded
JWE Shared Unprotected Header and
JWE Per-Recipient Unprotected Header values.
When using the JWE Compact Serialization,
the JWE Protected Header,
the JWE Encrypted Key,
the JWE Initialization Vector,
the JWE Ciphertext, and
the JWE Authentication Tag
are represented as base64url encoded values in that order,
separated by four period ('.') characters.
The JWE JSON Serialization
is described in .
The encoded representations of
the JWE Protected Header,
the JWE Encrypted Key,
the JWE Initialization Vector,
the JWE Ciphertext,
the JWE Authentication Tag, and
the JWE AAD
MUST be successfully base64url decoded following the
restriction that no padding characters have been used.
The octet sequence resulting from decoding the encoded JWE Protected Header
MUST be a UTF-8 encoded representation of
a completely valid JSON object
conforming to ,
which is the JWE Protected Header.
If using the JWE Compact Serialization, let the JWE Header be the
JWE Protected Header;
otherwise, when using the JWE JSON Serialization,
let the JWE Header be the union of
the members of the JWE Protected Header,
the JWE Shared Unprotected Header and
the corresponding JWE Per-Recipient Unprotected Header,
all of which must be completely valid JSON objects.
The resulting JWE Header MUST NOT contain duplicate
Header Parameter names.
When using the JWE JSON Serialization, this restriction includes
that the same Header Parameter name also MUST NOT occur in
distinct JSON object values that together comprise the JWE Header.
Verify that the implementation understands and can process
all fields that it is required to support,
whether required by this specification,
by the algorithms being used,
or by the crit Header Parameter value,
and that the values of those parameters are also understood and supported.
Determine the Key Management Mode employed by the algorithm
specified by the
alg (algorithm) Header Parameter.
Verify that the JWE uses a key known to the recipient.
When Direct Key Agreement or Key Agreement with Key Wrapping
are employed, use the key agreement algorithm
to compute the value of the agreed upon key.
When Direct Key Agreement is employed,
let the Content Encryption Key (CEK) be the agreed upon key.
When Key Agreement with Key Wrapping is employed,
the agreed upon key will be used to decrypt the JWE Encrypted Key.
When Key Wrapping, Key Encryption,
or Key Agreement with Key Wrapping are employed,
decrypt the JWE Encrypted Key to produce the Content Encryption Key (CEK).
The CEK MUST have a length equal to that
required for the content encryption algorithm.
Note that when there are multiple recipients,
each recipient will only be able decrypt any JWE Encrypted Key values
that were encrypted to a key in that recipient's possession.
It is therefore normal to only be able to decrypt one of the
per-recipient JWE Encrypted Key values to obtain the CEK value.
To mitigate the attacks described in RFC 3218,
the recipient MUST NOT distinguish between format, padding, and
length errors of encrypted keys. It is strongly recommended,
in the event of receiving an improperly formatted key,
that the receiver substitute a randomly generated
CEK and proceed to the next step, to mitigate timing attacks.
When Direct Key Agreement or Direct Encryption are employed,
verify that the JWE Encrypted Key value is empty octet sequence.
When Direct Encryption is employed,
let the Content Encryption Key (CEK) be the shared symmetric key.
If the JWE JSON Serialization is being used, repeat this process
(steps 4-12)
for each recipient contained in the representation
until the CEK value has been determined.
Compute the Encoded Protected Header value
BASE64URL(UTF8(JWE Protected Header)).
If the JWE Protected Header is not present
(which can only happen when using the JWE JSON Serialization
and no protected member is present),
let this value be the empty string.
Let the Additional Authenticated Data encryption parameter be
ASCII(Encoded Protected Header).
However if a JWE AAD value is present
(which can only be the case when using the JWE JSON Serialization),
instead let the Additional Authenticated Data encryption parameter be
ASCII(Encoded Protected Header || '.' || BASE64URL(JWE AAD)).
Decrypt the JWE Ciphertext using the CEK, the JWE Initialization Vector,
the Additional Authenticated Data value,
and the JWE Authentication Tag
(which is the Authentication Tag input to the calculation)
using the specified content encryption algorithm,
returning the decrypted plaintext and validating the JWE Authentication Tag
in the manner specified for the algorithm,
rejecting the input without emitting any decrypted output
if the JWE Authentication Tag is incorrect.
If a zip parameter was included,
uncompress the decrypted plaintext using the specified compression algorithm.
If all the previous steps succeeded, output the resulting Plaintext.
The string comparison rules for this specification are the same as
those defined in
Section 5.3 of .
The key identification methods for this specification are the same as
those defined in
Section 6 of , except that
the key being identified is
the public key to which the JWE was encrypted.
JWE objects use one of two serializations, the
JWE Compact Serialization
or the
JWE 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 JWE JSON Serialization is used,
that only JWE JSON Serialization support for a single recipient is used,
or that support for multiple recipients is used.
JWE implementations only need to implement the features needed
for the applications they are designed to support.
The JWE Compact Serialization represents encrypted
content as a compact URL-safe string.
This string is
BASE64URL(UTF8(JWE Protected Header))
|| '.' || BASE64URL(JWE Encrypted Key)
|| '.' || BASE64URL(JWE Initialization Vector)
|| '.' || BASE64URL(JWE Ciphertext)
|| '.' || BASE64URL(JWE Authentication Tag).
Only one recipient is supported by the JWE Compact Serialization
and it provides no syntax to represent
JWE Shared Unprotected Header,
JWE Per-Recipient Unprotected Header,
or JWE AAD values.
The JWE JSON Serialization represents encrypted
content as a JSON object.
Content using
the JWE JSON Serialization can be encrypted to more than one recipient.
This representation is neither optimized for compactness nor URL-safe.
The following members are defined for use in
top-level JSON objects used for the JWE JSON Serialization:
The protected member MUST be present and contain the value
BASE64URL(UTF8(JWE Protected Header)) when the JWE Protected Header
value is non-empty; otherwise, it MUST be absent.
These Header Parameter values are integrity protected.
The unprotected member MUST be present and contain the value
JWE Shared Unprotected Header when the JWE Shared 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 iv member MUST be present and contain the value
BASE64URL(JWE Initialization Vector) when the JWE Initialization Vector
value is non-empty; otherwise, it MUST be absent.
The aad member MUST be present and contain the value
BASE64URL(JWE AAD)) when the JWE AAD
value is non-empty; otherwise, it MUST be absent.
A JWE AAD value
can be included to supply a base64url encoded value
to be integrity protected but not encrypted.
The ciphertext member MUST be present and contain the value
BASE64URL(JWE Ciphertext).
The tag member MUST be present and contain the value
BASE64URL(JWE Authentication Tag) when the JWE Authentication Tag
value is non-empty; otherwise, it MUST be absent.
The recipients member value MUST be
an array of JSON objects.
Each object contains information specific to a single recipient.
This member MUST be present,
even if the array elements contain only the empty JSON object
{}
(which can happen when all Header Parameter values are shared
between all recipients and when no encrypted key is used,
such as when doing Direct Encryption).
The following members are defined for use in
the JSON objects that are elements of
the recipients array:
The header member MUST be present and contain the value
JWE Per-Recipient Unprotected Header when the JWE Per-Recipient 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 encrypted_key member MUST be present and contain the value
BASE64URL(JWE Encrypted Key) when the JWE Encrypted Key
value is non-empty; otherwise, it MUST be absent.
At least one of the
header,
protected,
and unprotected
members MUST be present so that alg
and enc
Header Parameter values are conveyed for each recipient computation.
Additional members can be present in both the JSON objects defined above;
if not understood by implementations encountering them, they MUST be ignored.
Some Header Parameters, including the alg
parameter, can be shared among all recipient computations.
Header Parameters in the JWE Protected Header and
JWE Shared Unprotected Header values are shared among all recipients.
The Header Parameter values used when creating or validating
per-recipient Ciphertext and Authentication Tag values are
the union of the three sets of Header Parameter values that may be present:
(1) the JWE Protected Header represented in the
protected member,
(2) the JWE Shared Unprotected Header represented in the
unprotected member, and
(3) the JWE Per-Recipient Unprotected Header represented in the
header
member of the recipient's array element.
The union of these sets of Header Parameters comprises the JWE Header.
The Header Parameter names in the three locations MUST be disjoint.
Each JWE Encrypted Key value is computed using the
parameters of the corresponding JWE Header value
in the same manner as for the JWE Compact Serialization.
This has the desirable property that each
JWE Encrypted Key value
in the recipients array
is identical to the value
that would have been computed for the same parameter
in the JWE Compact Serialization.
Likewise, the JWE Ciphertext and JWE Authentication Tag values
match those produced for the JWE Compact Serialization,
provided that the JWE Protected Header value
(which represents the integrity-protected Header Parameter values)
matches that used in
the JWE Compact Serialization.
All recipients use the same
JWE Protected Header,
JWE Initialization Vector,
JWE Ciphertext,
and JWE Authentication Tag values,
when present, resulting in
potentially significant space savings if the message is large.
Therefore, all Header Parameters that specify the treatment of
the Plaintext value MUST be the same for all recipients.
This primarily means that the enc (encryption algorithm) Header Parameter
value in the JWE Header for each recipient
and any parameters of that algorithm MUST be the same.
See for an example
of computing a JWE using the JWE JSON Serialization.
The TLS requirements for this specification are the same as
those defined in
Section 8 of .
There are several ways of distinguishing whether an object is a
JWS or JWE object.
All these methods will yield the same result for all legal input values;
they may yield different results for malformed inputs.
If the object is using the JWS Compact Serialization or
the JWE Compact Serialization, the number of base64url encoded segments
separated by period ('.') characters differs for JWSs and JWEs.
JWSs have three segments separated by two period ('.') characters.
JWEs have five segments separated by four period ('.') characters.
If the object is using the JWS JSON Serialization or
the JWE JSON Serialization, the members used will be different.
JWSs have a signatures member and JWEs do not.
JWEs have a recipients member and JWSs do not.
A JWS Header can be distinguished from a JWE header by
examining the alg
(algorithm) Header Parameter value.
If the value represents a digital signature or MAC algorithm,
or is the value none, it is for a JWS;
if it represents a Key Encryption, Key Wrapping, Direct Key Agreement,
Key Agreement with Key Wrapping, or Direct Encryption algorithm, it is for a JWE.
(Extracting the alg value to examine is
straightforward when using the JWS Compact Serialization or
the JWE Compact Serialization and may be more difficult when
using the JWS JSON Serialization or the JWE JSON Serialization.)
A JWS Header can also be distinguished from a JWE header by
determining whether an
enc (encryption algorithm) member exists.
If the enc member exists, it is a JWE;
otherwise, it is a JWS.
This specification registers the Header Parameter names defined in
in the IANA
JSON Web Signature and Encryption Header Parameters registry
defined in
.
Header Parameter Name: alg
Header Parameter Description: Algorithm
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: enc
Header Parameter Description: Encryption Algorithm
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: zip
Header Parameter Description: Compression Algorithm
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: jku
Header Parameter Description: JWK Set URL
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: jwk
Header Parameter Description: JSON Web Key
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification document(s): of [[ this document ]]
Header Parameter Name: kid
Header Parameter Description: Key ID
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: x5u
Header Parameter Description: X.509 URL
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: x5c
Header Parameter Description: X.509 Certificate Chain
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: x5t
Header Parameter Description: X.509 Certificate SHA-1 Thumbprint
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: typ
Header Parameter Description: Type
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: cty
Header Parameter Description: Content Type
Header Parameter Usage Location(s): JWE
Change Controller: IESG
Specification Document(s): of [[ this document ]]
Header Parameter Name: crit
Header Parameter Description: Critical
Header Parameter Usage Location(s): JWE
Change Controller: IESG
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 and symmetric keys, preventing various attacks, and helping the
user avoid mistakes such as inadvertently encrypting a message for
the wrong recipient. The entire list of security considerations is
beyond the scope of this document.
All the security considerations in the JWS specification
also apply to this specification.
Likewise, all the security considerations in
XML Encryption 1.1
also apply, other than those that are XML specific.
When decrypting, particular care must be taken not to allow
the JWE recipient to be used as an oracle for decrypting messages.
RFC 3218 should be consulted for specific
countermeasures to attacks on RSAES-PKCS1-V1_5.
An attacker might modify the contents of the alg
parameter from RSA-OAEP to
RSA1_5 in order to generate a
formatting error that can be detected and used to recover the CEK
even if RSAES OAEP was used to encrypt the CEK.
It is therefore particularly important to report all
formatting errors to the CEK, Additional Authenticated Data,
or ciphertext as a single error when the encrypted content is rejected.
Additionally, this type of attack can be prevented by the use of "key tainting".
This method restricts the use of a key to a limited set of algorithms
-- usually one.
This means, for instance, that if the key is marked as being for
RSA-OAEP only, any attempt to decrypt a message
using the RSA1_5 algorithm with that key would
fail immediately due to invalid use of the key.
JSON Web Signature (JWS)Microsoftmbj@microsoft.comhttp://self-issued.info/Ping Identityve7jtb@ve7jtb.comNomura Research Instituten-sakimura@nri.co.jpJSON Web Key (JWK)Microsoftmbj@microsoft.comhttp://self-issued.info/JSON Web Algorithms (JWA)Microsoftmbj@microsoft.comhttp://self-issued.info/Coded Character Set -- 7-bit American Standard Code for Information InterchangeAmerican National Standards InstituteECMAScript Language Specification, 5.1 EditionEcma InternationalJSON Simple EncryptionindependentNomura Research Institute
This section provides examples of JWE computations.
This example encrypts the plaintext
"The true sign of intelligence is not knowledge but imagination."
to the recipient using RSAES OAEP for key encryption
and AES GCM for content encryption.
The representation of this plaintext is:
[84, 104, 101, 32, 116, 114, 117, 101, 32, 115, 105, 103, 110, 32, 111, 102,
32, 105, 110, 116, 101, 108, 108, 105, 103, 101, 110, 99, 101, 32, 105, 115,
32, 110, 111, 116, 32, 107, 110, 111, 119, 108, 101, 100, 103, 101, 32, 98,
117, 116, 32, 105, 109, 97, 103, 105, 110, 97, 116, 105, 111, 110, 46]
The following example JWE Protected Header declares that:
the Content Encryption Key is encrypted to the recipient
using the RSAES OAEP algorithm to produce
the JWE Encrypted Key and
the Plaintext is encrypted using the AES GCM
algorithm with a 256 bit key to produce the Ciphertext.
Encoding this JWE Protected Header as
BASE64URL(UTF8(JWE Protected Header)) gives this value:
Generate a 256 bit random Content Encryption Key (CEK).
In this example, the value is:
[177, 161, 244, 128, 84, 143, 225, 115, 63, 180, 3, 255, 107, 154, 212, 246,
138, 7, 110, 91, 112, 46, 34, 105, 47, 130, 203, 46, 122, 234, 64, 252]
Encrypt the CEK with the recipient's public key using the RSAES OAEP
algorithm to produce the JWE Encrypted Key.
This example uses the RSA key
represented in JSON Web Key format below
(with line breaks for display purposes only):
The resulting JWE Encrypted Key value is:
[56, 163, 154, 192, 58, 53, 222, 4, 105, 218, 136, 218, 29, 94, 203, 22,
150, 92, 129, 94, 211, 232, 53, 89, 41, 60, 138, 56, 196, 216, 82, 98,
168, 76, 37, 73, 70, 7, 36, 8, 191, 100, 136, 196, 244, 220, 145, 158,
138, 155, 4, 117, 141, 230, 199, 247, 173, 45, 182, 214, 74, 177, 107, 211,
153, 11, 205, 196, 171, 226, 162, 128, 171, 182, 13, 237, 239, 99, 193, 4,
91, 219, 121, 223, 107, 167, 61, 119, 228, 173, 156, 137, 134, 200, 80, 219,
74, 253, 56, 185, 91, 177, 34, 158, 89, 154, 205, 96, 55, 18, 138, 43,
96, 218, 215, 128, 124, 75, 138, 243, 85, 25, 109, 117, 140, 26, 155, 249,
67, 167, 149, 231, 100, 6, 41, 65, 214, 251, 232, 87, 72, 40, 182, 149,
154, 168, 31, 193, 126, 215, 89, 28, 111, 219, 125, 182, 139, 235, 195, 197,
23, 234, 55, 58, 63, 180, 68, 202, 206, 149, 75, 205, 248, 176, 67, 39,
178, 60, 98, 193, 32, 238, 122, 96, 158, 222, 57, 183, 111, 210, 55, 188,
215, 206, 180, 166, 150, 166, 106, 250, 55, 229, 72, 40, 69, 214, 216, 104,
23, 40, 135, 212, 28, 127, 41, 80, 175, 174, 168, 115, 171, 197, 89, 116,
92, 103, 246, 83, 216, 182, 176, 84, 37, 147, 35, 45, 219, 172, 99, 226,
233, 73, 37, 124, 42, 72, 49, 242, 35, 127, 184, 134, 117, 114, 135, 206]
Encoding this JWE Encrypted Key as
BASE64URL(JWE Encrypted Key) gives this value
(with line breaks for display purposes only):
Generate a random 96 bit JWE Initialization Vector.
In this example, the value is:
[227, 197, 117, 252, 2, 219, 233, 68, 180, 225, 77, 219]
Encoding this JWE Initialization Vector as
BASE64URL(JWE Initialization Vector) gives this value:
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))).
This value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69, 116,
84, 48, 70, 70, 85, 67, 73, 115, 73, 109, 86, 117, 89, 121, 73, 54,
73, 107, 69, 121, 78, 84, 90, 72, 81, 48, 48, 105, 102, 81]
Encrypt the Plaintext with AES GCM
using the CEK as the encryption key,
the JWE Initialization Vector,
and the Additional Authenticated Data value above,
requesting a 128 bit Authentication Tag output.
The resulting Ciphertext is:
[229, 236, 166, 241, 53, 191, 115, 196, 174, 43, 73, 109, 39, 122, 233, 96,
140, 206, 120, 52, 51, 237, 48, 11, 190, 219, 186, 80, 111, 104, 50, 142,
47, 167, 59, 61, 181, 127, 196, 21, 40, 82, 242, 32, 123, 143, 168, 226,
73, 216, 176, 144, 138, 247, 106, 60, 16, 205, 160, 109, 64, 63, 192]
The resulting Authentication Tag value is:
[92, 80, 104, 49, 133, 25, 161, 215, 173, 101, 219, 211, 136, 91, 210, 145]
Encoding this JWE Ciphertext as
BASE64URL(JWE Ciphertext) gives this value
(with line breaks for display purposes only):
Encoding this JWE Authentication Tag as
BASE64URL(JWE Authentication Tag) gives this value:
Assemble the final representation:
The Compact Serialization of this result is the string
BASE64URL(UTF8(JWE Protected Header))
|| '.' || BASE64URL(JWE Encrypted Key)
|| '.' || BASE64URL(JWE Initialization Vector)
|| '.' || BASE64URL(JWE Ciphertext)
|| '.' || BASE64URL(JWE Authentication Tag).
The final result in this example
(with line breaks for display purposes only) is:
This example illustrates the process of creating a JWE with
RSAES OAEP for key encryption
and AES GCM for content encryption.
These results can be used to validate JWE decryption implementations for these algorithms.
Note that since the RSAES OAEP computation includes random values,
the encryption results above will not be completely reproducible.
However, since the AES GCM computation is deterministic, the JWE Encrypted Ciphertext
values will be the same for all encryptions performed using these inputs.
This example encrypts the plaintext
"Live long and prosper."
to the recipient using RSAES-PKCS1-V1_5 for key encryption
and AES_128_CBC_HMAC_SHA_256 for content encryption.
The representation of this plaintext is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114,
111, 115, 112, 101, 114, 46]
The following example JWE Protected Header declares that:
the Content Encryption Key is encrypted to the recipient
using the RSAES-PKCS1-V1_5 algorithm to produce
the JWE Encrypted Key and
the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
algorithm to produce the Ciphertext.
Encoding this JWE Protected Header as
BASE64URL(UTF8(JWE Protected Header)) gives this value:
Generate a 256 bit random Content Encryption Key (CEK).
In this example, the key value is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106, 206,
107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156, 44, 207]
Encrypt the CEK with the recipient's public key using the RSAES-PKCS1-V1_5
algorithm to produce the JWE Encrypted Key.
This example uses the RSA key
represented in JSON Web Key format below
(with line breaks for display purposes only):
The resulting JWE Encrypted Key value is:
[80, 104, 72, 58, 11, 130, 236, 139, 132, 189, 255, 205, 61, 86, 151, 176,
99, 40, 44, 233, 176, 189, 205, 70, 202, 169, 72, 40, 226, 181, 156, 223,
120, 156, 115, 232, 150, 209, 145, 133, 104, 112, 237, 156, 116, 250, 65, 102,
212, 210, 103, 240, 177, 61, 93, 40, 71, 231, 223, 226, 240, 157, 15, 31,
150, 89, 200, 215, 198, 203, 108, 70, 117, 66, 212, 238, 193, 205, 23, 161,
169, 218, 243, 203, 128, 214, 127, 253, 215, 139, 43, 17, 135, 103, 179, 220,
28, 2, 212, 206, 131, 158, 128, 66, 62, 240, 78, 186, 141, 125, 132, 227,
60, 137, 43, 31, 152, 199, 54, 72, 34, 212, 115, 11, 152, 101, 70, 42,
219, 233, 142, 66, 151, 250, 126, 146, 141, 216, 190, 73, 50, 177, 146, 5,
52, 247, 28, 197, 21, 59, 170, 247, 181, 89, 131, 241, 169, 182, 246, 99,
15, 36, 102, 166, 182, 172, 197, 136, 230, 120, 60, 58, 219, 243, 149, 94,
222, 150, 154, 194, 110, 227, 225, 112, 39, 89, 233, 112, 207, 211, 241, 124,
174, 69, 221, 179, 107, 196, 225, 127, 167, 112, 226, 12, 242, 16, 24, 28,
120, 182, 244, 213, 244, 153, 194, 162, 69, 160, 244, 248, 63, 165, 141, 4,
207, 249, 193, 79, 131, 0, 169, 233, 127, 167, 101, 151, 125, 56, 112, 111,
248, 29, 232, 90, 29, 147, 110, 169, 146, 114, 165, 204, 71, 136, 41, 252]
Encoding this JWE Encrypted Key as
BASE64URL(JWE Encrypted Key) gives this value
(with line breaks for display purposes only):
Generate a random 128 bit JWE Initialization Vector.
In this example, the value is:
[3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104, 101]
Encoding this JWE Initialization Vector as
BASE64URL(JWE Initialization Vector) gives this value:
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))).
This value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69, 120,
88, 122, 85, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50,
73, 110, 48]
Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256
using the CEK as the encryption key,
the JWE Initialization Vector,
and the Additional Authenticated Data value above.
The steps for doing this using the values from
are detailed in .
The resulting Ciphertext is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6, 75,
129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143, 112, 56, 102]
The resulting Authentication Tag value is:
[246, 17, 244, 190, 4, 95, 98, 3, 231, 0, 115, 157, 242, 203, 100, 191]
Encoding this JWE Ciphertext as
BASE64URL(JWE Ciphertext) gives this value:
Encoding this JWE Authentication Tag as
BASE64URL(JWE Authentication Tag) gives this value:
Assemble the final representation:
The Compact Serialization of this result is the string
BASE64URL(UTF8(JWE Protected Header))
|| '.' || BASE64URL(JWE Encrypted Key)
|| '.' || BASE64URL(JWE Initialization Vector)
|| '.' || BASE64URL(JWE Ciphertext)
|| '.' || BASE64URL(JWE Authentication Tag).
The final result in this example
(with line breaks for display purposes only) is:
This example illustrates the process of creating a JWE with
RSAES-PKCS1-V1_5 for key encryption
and AES_CBC_HMAC_SHA2 for content encryption.
These results can be used to validate JWE decryption implementations for these algorithms.
Note that since the RSAES-PKCS1-V1_5 computation includes random values,
the encryption results above will not be completely reproducible.
However, since the AES CBC computation is deterministic, the JWE Encrypted Ciphertext
values will be the same for all encryptions performed using these inputs.
This example encrypts the plaintext
"Live long and prosper."
to the recipient using AES Key Wrap for key encryption
and AES_128_CBC_HMAC_SHA_256 for content encryption.
The representation of this plaintext is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114,
111, 115, 112, 101, 114, 46]
The following example JWE Protected Header declares that:
the Content Encryption Key is encrypted to the recipient
using the AES Key Wrap algorithm with a 128 bit key to produce
the JWE Encrypted Key and
the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256
algorithm to produce the Ciphertext.
Encoding this JWE Protected Header as
BASE64URL(UTF8(JWE Protected Header)) gives this value:
Generate a 256 bit random Content Encryption Key (CEK).
In this example, the value is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106, 206,
107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156, 44, 207]
Encrypt the CEK with the shared symmetric key using the AES Key Wrap
algorithm to produce the JWE Encrypted Key.
This example uses the symmetric key
represented in JSON Web Key format below:
The resulting JWE Encrypted Key value is:
[232, 160, 123, 211, 183, 76, 245, 132, 200, 128, 123, 75, 190, 216, 22, 67,
201, 138, 193, 186, 9, 91, 122, 31, 246, 90, 28, 139, 57, 3, 76, 124,
193, 11, 98, 37, 173, 61, 104, 57]
Encoding this JWE Encrypted Key as
BASE64URL(JWE Encrypted Key) gives this value:
Generate a random 128 bit JWE Initialization Vector.
In this example, the value is:
[3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104, 101]
Encoding this JWE Initialization Vector as
BASE64URL(JWE Initialization Vector) gives this value:
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))).
This value is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50,
73, 110, 48]
Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256
using the CEK as the encryption key,
the JWE Initialization Vector,
and the Additional Authenticated Data value above.
The steps for doing this using the values from this example
are detailed in .
The resulting Ciphertext is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6, 75,
129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143, 112, 56, 102]
The resulting Authentication Tag value is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38, 194, 85]
Encoding this JWE Ciphertext as
BASE64URL(JWE Ciphertext) gives this value:
Encoding this JWE Authentication Tag as
BASE64URL(JWE Authentication Tag) gives this value:
Assemble the final representation:
The Compact Serialization of this result is the string
BASE64URL(UTF8(JWE Protected Header))
|| '.' || BASE64URL(JWE Encrypted Key)
|| '.' || BASE64URL(JWE Initialization Vector)
|| '.' || BASE64URL(JWE Ciphertext)
|| '.' || BASE64URL(JWE Authentication Tag).
The final result in this example
(with line breaks for display purposes only) is:
This example illustrates the process of creating a JWE with
AES Key Wrap for key encryption
and AES GCM for content encryption.
These results can be used to validate JWE decryption implementations for these algorithms.
Also, since both the AES Key Wrap and AES GCM computations are deterministic,
the resulting JWE value will be the same for all encryptions performed using these inputs.
Since the computation is reproducible, these results can also be used to validate
JWE encryption implementations for these algorithms.
This section contains an example using the JWE JSON Serialization.
This example demonstrates the capability for
encrypting the same plaintext to multiple recipients.
Two recipients are present in this example.
The algorithm and key used for the first recipient
are the same as that used in .
The algorithm and key used for the second recipient
are the same as that used in .
The resulting JWE Encrypted Key values are therefore the same;
those computations are not repeated here.
The Plaintext, the Content Encryption Key (CEK), Initialization Vector,
and JWE Protected Header are shared by all recipients
(which must be the case, since the Ciphertext and
Authentication Tag are also shared).
The first recipient uses the RSAES-PKCS1-V1_5 algorithm
to encrypt the Content Encryption Key (CEK).
The second uses AES Key Wrap to encrypt the CEK.
Key ID values are supplied for both keys.
The two per-recipient header values used to represent
these algorithms and Key IDs are:
and
The Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256 algorithm
to produce the common JWE Ciphertext and JWE Authentication Tag values.
The JWE Protected Header value representing this is:
Encoding this JWE Protected Header as
BASE64URL(UTF8(JWE Protected Header)) gives this value:
This JWE uses the jku Header Parameter
to reference a JWK Set.
This is represented in the following JWE Unprotected Header value as:
Combining the per-recipient, protected, and unprotected header values
supplied, the JWE Header values used for the first and second recipient
respectively are:
and
Let the Additional Authenticated Data encryption parameter be
ASCII(BASE64URL(UTF8(JWE Protected Header))).
This value is:
[101, 121, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73, 52,
81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48]
Encrypt the Plaintext with AES_128_CBC_HMAC_SHA_256
using the CEK as the encryption key,
the JWE Initialization Vector,
and the Additional Authenticated Data value above.
The steps for doing this using the values from
are detailed in .
The resulting Ciphertext is:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6, 75,
129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143, 112, 56, 102]
The resulting Authentication Tag value is:
[51, 63, 149, 60, 252, 148, 225, 25, 92, 185, 139, 245, 35, 2, 47, 207]
Encoding this JWE Ciphertext as
BASE64URL(JWE Ciphertext) gives this value:
Encoding this JWE Authentication Tag as
BASE64URL(JWE Authentication Tag) gives this value:
The complete JSON Web Encryption JSON Serialization
for these values is as follows
(with line breaks for display purposes only):
This example shows the steps in the AES_128_CBC_HMAC_SHA_256
authenticated encryption computation using the values from
the example in .
As described where this algorithm is defined in
Sections 5.2 and 5.2.3 of JWA, the AES_CBC_HMAC_SHA2 family
of algorithms are implemented using
Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #5 padding
to perform the encryption and
an HMAC SHA-2 function to perform the integrity calculation
- in this case, HMAC SHA-256.
The 256 bit AES_128_CBC_HMAC_SHA_256 key K used in this example is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106, 206,
107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156, 44, 207]
Use the first 128 bits of this key as the HMAC SHA-256 key MAC_KEY, which is:
[4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106, 206]
Use the last 128 bits of this key as the AES CBC key ENC_KEY, which is:
[107, 124, 212, 45, 111, 107, 9, 219, 200, 177, 0, 240, 143, 156, 44, 207]
Note that the MAC key comes before the encryption key in the input key K;
this is in the opposite order of the algorithm names in
the identifiers "AES_128_CBC_HMAC_SHA_256" and
A128CBC-HS256.
Encrypt the Plaintext with
AES in Cipher Block Chaining (CBC) mode using PKCS #5 padding
using the ENC_KEY above.
The Plaintext in this example is:
[76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114,
111, 115, 112, 101, 114, 46]
The encryption result is as follows, which is the Ciphertext output:
[40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6, 75,
129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143, 112, 56, 102]
The Additional Authenticated Data (AAD) in this example is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50,
73, 110, 48]
This AAD is 51 bytes long, which is 408 bits long.
The octet string AL, which is the number of bits in AAD
expressed as a big endian 64 bit unsigned integer is:
[0, 0, 0, 0, 0, 0, 1, 152]
The Initialization Vector value used in this example is:
[3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111, 116, 104, 101]
Concatenate
the AAD,
the Initialization Vector,
the Ciphertext,
and the AL value.
The result of this concatenation is:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52,
83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66,
77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50,
73, 110, 48, 3, 22, 60, 12, 43, 67, 104, 105, 108, 108, 105, 99, 111,
116, 104, 101, 40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152,
230, 6, 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143,
112, 56, 102, 0, 0, 0, 0, 0, 0, 1, 152]
Compute the HMAC SHA-256 of the concatenated value above. This result M is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38, 194, 85,
9, 84, 229, 201, 219, 135, 44, 252, 145, 102, 179, 140, 105, 86, 229, 116]
Use the first half (128 bits) of the HMAC output M as
the Authentication Tag output T. This truncated value is:
[83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38, 194, 85]
Solutions for encrypting JSON content were also explored by
JSON Simple Encryption and
JavaScript Message Security
Format, both of which significantly influenced this draft.
This draft attempts to explicitly reuse as many of the relevant concepts from
XML Encryption 1.1
and RFC 5652 as possible,
while utilizing simple, compact JSON-based data structures.
Special thanks are due to John Bradley, Eric Rescorla, and Nat Sakimura for
the discussions that helped inform the content of this
specification, to Eric Rescorla and Joe Hildebrand for
allowing the reuse of text from in this document,
and to Eric Rescorla for co-authoring many drafts of this specification.
Thanks to Axel Nennker, Emmanuel Raviart, Brian Campbell, and Edmund Jay
for validating the examples in this specification.
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:
Richard Barnes,
John Bradley,
Brian Campbell,
Breno de Medeiros,
Dick Hardt,
Jeff Hodges,
Edmund Jay,
James Manger,
Matt Miller,
Tony Nadalin,
Hideki Nara,
Axel Nennker,
Emmanuel Raviart,
Eric Rescorla,
Nat Sakimura,
Jim Schaad,
Hannes Tschofenig,
and Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
Sean Turner and Stephen Farrell served as Security area directors
during the creation of this specification.
[[ to be removed by the RFC Editor before publication as an RFC ]]
-25
Corrected two external section number references that had changed.
Corrected a typo in an algorithm name in the prose of an example.
-24
Corrected complete JSON Serialization example.
Replaced uses of the term "associated data" wherever it was used
to refer to a data value with "additional authenticated data",
since both terms were being used as synonyms, causing confusion.
Updated the JSON reference to RFC 7159.
Thanked Eric Rescorla for helping to author of most of the drafts
of this specification and removed him from the current author list.
-23
Corrected a use of the word "payload" to "plaintext".
-22
Corrected RFC 2119 terminology usage.
Replaced references to draft-ietf-json-rfc4627bis with RFC 7158.
-21
Changed some references from being normative to informative,
addressing issue #90.
Applied review comments to the JSON Serialization section,
addressing issue #178.
-20
Made terminology definitions more consistent,
addressing issue #165.
Restructured the JSON Serialization section to call out
the parameters used in hanging lists,
addressing issue #178.
Replaced references to RFC 4627 with draft-ietf-json-rfc4627bis,
addressing issue #90.
-19
Reordered the key selection parameters.
-18
Updated the mandatory-to-implement (MTI) language to say that
applications using this specification need to specify what serialization
and serialization features are used for that application,
addressing issue #176.
Changes to address editorial and minor issues
#89, #135, #165, #174, #175, #177, #179, and #180.
Used Header Parameter Description registry field.
-17
Refined the typ and
cty definitions to always be
MIME Media Types, with the omission of "application/"
prefixes recommended for brevity,
addressing issue #50.
Updated the mandatory-to-implement (MTI) language to say
that general-purpose implementations must implement the
single recipient case for both serializations
whereas special-purpose implementations can implement
just one serialization if that meets the needs of
the use cases the implementation is designed for,
addressing issue #176.
Explicitly named all the logical components of a JWE
and defined the processing rules and serializations
in terms of those components,
addressing issues #60, #61, and #62.
Replaced verbose repetitive phases such as
"base64url encode the octets of the UTF-8 representation of X"
with mathematical notation such as "BASE64URL(UTF8(X))".
Header Parameters and processing rules occurring in both
JWS and JWE are now referenced in JWS by JWE, rather than duplicated,
addressing issue #57.
Terms used in multiple documents are now defined in
one place and incorporated by reference.
Some lightly used or obvious terms were also removed.
This addresses issue #58.
-16
Changes to address editorial and minor issues
#163, #168, #169, #170, #172, and #173.
-15
Clarified that it is an application decision which
recipients' encrypted content
must successfully validate for the JWE to be accepted,
addressing issue #35.
Changes to address editorial issues
#34, #164, and #169.
-14
Clarified that the protected,
unprotected, header,
iv, tag,
and encrypted_key
parameters are to be omitted in the JWE JSON Serialization
when their values would be empty.
Stated that the recipients
array must always be present.
-13
Added an aad (Additional Authenticated Data) member
for the JWE JSON Serialization, enabling Additional Authenticated Data
to be supplied that is not double base64url encoded,
addressing issue #29.
-12
Clarified that the typ and
cty header parameters are used
in an application-specific manner
and have no effect upon the JWE processing.
Replaced the MIME types
application/jwe+json and
application/jwe with
application/jose+json and
application/jose.
Stated that recipients MUST either reject JWEs with
duplicate Header Parameter Names
or use a JSON parser that returns only
the lexically last duplicate member name.
Moved the
epk,
apu, and
apv
Header Parameter definitions to be with
the algorithm descriptions that use them.
Added a Serializations section with parallel treatment of the
JWE Compact Serialization
and the
JWE JSON Serialization
and also moved the former Implementation Considerations content there.
Restored use of the term "AEAD".
Changed terminology from "block encryption" to "content encryption".
-11
Added Key Identification section.
Removed the Encrypted Key value from the AAD computation since it is
already effectively integrity protected by the encryption process.
The AAD value now only contains the representation of the JWE Encrypted Header.
For the JWE JSON Serialization, enable Header Parameter values
to be specified in any of three parameters:
the protected member that is
integrity protected and shared among all recipients,
the unprotected member that is
not integrity protected and shared among all recipients,
and the header member that is
not integrity protected and specific to a particular recipient.
(This does not affect the JWE Compact Serialization, in which all
Header Parameter values are in a single integrity protected JWE Header value.)
Shortened the names authentication_tag to
tag and
initialization_vector to
iv in the JWE JSON Serialization,
addressing issue #20.
Removed apv (agreement PartyVInfo)
since it is no longer used.
Removed suggested compact serialization for multiple recipients.
Changed the MIME type name application/jwe-js
to application/jwe+json,
addressing issue #22.
Tightened the description of the
crit (critical) header parameter.
-10
Changed the JWE processing rules for multiple recipients so that
a single AAD value contains the header parameters and encrypted key
values for all the recipients,
enabling AES GCM to be safely used for multiple recipients.
Added an appendix suggesting a possible compact serialization
for JWEs with multiple recipients.
-09
Added JWE JSON Serialization, as specified by
draft-jones-jose-jwe-json-serialization-04.
Registered application/jwe-js MIME type
and JWE-JS typ header parameter value.
Defined that the default action for header parameters that
are not understood is to ignore them unless specifically
designated as "MUST be understood" or included in the new
crit (critical) header parameter list.
This addressed issue #6.
Corrected x5c description.
This addressed issue #12.
Changed from using the term "byte" to "octet" when referring to 8 bit values.
Added Key Management Mode definitions to terminology section
and used the defined terms to provide clearer key management instructions.
This addressed issue #5.
Added text about preventing the recipient from behaving as an oracle
during decryption, especially when using RSAES-PKCS1-V1_5.
Changed from using the term "Integrity Value" to "Authentication Tag".
Changed member name from integrity_value to
authentication_tag in the JWE JSON Serialization.
Removed Initialization Vector from the AAD value since it is already
integrity protected by all of the authenticated encryption algorithms
specified in the JWA specification.
Replaced A128CBC+HS256
and A256CBC+HS512
with A128CBC-HS256
and A256CBC-HS512.
The new algorithms perform the same cryptographic computations as
,
but with the Initialization Vector and Authentication Tag values remaining
separate from the Ciphertext value in the output representation.
Also deleted the header parameters
epu (encryption PartyUInfo) and
epv (encryption PartyVInfo),
since they are no longer used.
-08
Replaced uses of the term "AEAD" with "Authenticated Encryption", since
the term AEAD in the RFC 5116 sense implied the use of a particular
data representation, rather than just referring to the class of
algorithms that perform authenticated encryption with associated data.
Applied editorial improvements suggested by
Jeff Hodges and Hannes Tschofenig.
Many of these simplified the terminology used.
Clarified statements of the form "This header parameter is OPTIONAL"
to "Use of this header parameter is OPTIONAL".
Added a Header Parameter Usage Location(s) field to the
IANA JSON Web Signature and Encryption Header Parameters registry.
Added seriesInfo information to Internet Draft references.
-07
Added a data length prefix to PartyUInfo and PartyVInfo values.
Updated values for example AES CBC calculations.
Made several local editorial changes to clean up loose ends
left over from to the decision to only support
block encryption methods providing integrity.
One of these changes was to explicitly state that the
enc (encryption method) algorithm
must be an Authenticated Encryption algorithm with a specified key length.
-06
Removed the int and
kdf parameters and defined the new composite
Authenticated Encryption algorithms A128CBC+HS256 and
A256CBC+HS512 to replace the former
uses of AES CBC, which required the use of separate integrity
and key derivation functions.
Included additional values in the Concat KDF calculation -- the
desired output size and the algorithm value,
and optionally PartyUInfo and PartyVInfo values.
Added the optional header parameters
apu (agreement PartyUInfo),
apv (agreement PartyVInfo),
epu (encryption PartyUInfo), and
epv (encryption PartyVInfo).
Updated the KDF examples accordingly.
Promoted Initialization Vector from being a header parameter to being
a top-level JWE element.
This saves approximately 16 bytes in the compact serialization,
which is a significant savings for some use cases.
Promoting the Initialization Vector out of the header also avoids repeating
this shared value in the JSON serialization.
Changed x5c (X.509 Certificate Chain)
representation from being a single string to being an array of strings,
each containing a single base64 encoded DER certificate value,
representing elements of the certificate chain.
Added an AES Key Wrap example.
Reordered the encryption steps so CMK creation is first, when required.
Correct statements in examples about which algorithms produce
reproducible results.
-05
Support both direct encryption using a
shared or agreed upon symmetric key, and the use of a
shared or agreed upon symmetric key to key wrap the CMK.
Added statement that
"StringOrURI values are compared as case-sensitive strings
with no transformations or canonicalizations applied".
Updated open issues.
Indented artwork elements to better distinguish them from the body text.
-04
Refer to the registries as the primary sources of defined
values and then secondarily reference the sections
defining the initial contents of the registries.
Normatively reference
XML Encryption 1.1
for its security considerations.
Reference draft-jones-jose-jwe-json-serialization
instead of draft-jones-json-web-encryption-json-serialization.
Described additional open issues.
Applied editorial suggestions.
-03
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.
Reordered encryption steps so that the Encoded JWE Header
is always created before it is needed as an input to the Authenticated Encryption
"additional authenticated data" parameter.
Added the cty (content type) header parameter
for declaring type information about the secured content,
as opposed to the typ (type) header parameter,
which declares type information about this object.
Moved description of how to determine whether a header is
for a JWS or a JWE from the JWT spec to the JWE spec.
Added complete encryption examples for both Authenticated Encryption and non-Authenticated Encryption algorithms.
Added complete key derivation examples.
Added "Collision Resistant Namespace" to the terminology section.
Reference ITU.X690.1994 for DER encoding.
Added Registry Contents sections to populate registry values.
Numerous editorial improvements.
-02
When using Authenticated Encryption algorithms (such as AES GCM),
use the "additional authenticated data" parameter
to provide integrity for the header, encrypted key, and
ciphertext and use the resulting "authentication tag"
value as the JWE Authentication Tag.
Defined KDF output key sizes.
Generalized text to allow key agreement to be employed
as an alternative to key wrapping or key encryption.
Changed compression algorithm from gzip to DEFLATE.
Clarified that it is an error when a kid
value is included and no matching key is found.
Clarified that JWEs with duplicate Header Parameter Names
MUST be rejected.
Clarified the relationship between
typ header parameter values
and MIME types.
Registered application/jwe MIME type and "JWE" typ header parameter value.
Simplified JWK terminology to get replace the "JWK Key Object" and
"JWK Container Object" terms with simply "JSON Web Key (JWK)"
and "JSON Web Key Set (JWK Set)" and to eliminate potential
confusion between single keys and sets of keys.
As part of this change, the Header Parameter Name for a
public key value was changed from
jpk (JSON Public Key) to
jwk (JSON Web Key).
Added suggestion on defining additional header parameters
such as x5t#S256 in the future
for certificate thumbprints using hash algorithms other
than SHA-1.
Specify RFC 2818 server identity validation, rather than
RFC 6125 (paralleling the same decision in the OAuth specs).
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.
Reformatted to give each header parameter its own section heading.
-01
Added an integrity check for non-Authenticated Encryption algorithms.
Added jpk and x5c header parameters for including
JWK public keys and X.509 certificate chains directly in
the header.
Clarified that this specification is defining the JWE
Compact Serialization. Referenced the new JWE-JS spec,
which defines the JWE JSON Serialization.
Added text "New header parameters should be introduced
sparingly since an implementation that does not understand
a parameter MUST reject the JWE".
Clarified that the order of the encryption and decryption
steps is not significant in cases where there are no
dependencies between the inputs and outputs of the steps.
Made other editorial improvements suggested by JOSE
working group participants.
-00
Created the initial IETF draft based upon
draft-jones-json-web-encryption-02 with no normative
changes.
Changed terminology to no longer call both digital
signatures and HMACs "signatures".