| JOSE Working Group | M.B. Jones |
| Internet-Draft | Microsoft |
| Intended status: Standards Track | E. Rescorla |
| Expires: January 16, 2014 | RTFM |
| J. Hildebrand | |
| Cisco | |
| July 15, 2013 |
JSON Web Encryption (JWE)
draft-ietf-jose-json-web-encryption-13
JSON Web Encryption (JWE) is a means of representing 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. Related digital signature and MAC capabilities are described in the separate JSON Web Signature (JWS) specification.
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JSON Web Encryption (JWE) is a means of representing encrypted content using JavaScript Object Notation (JSON) [RFC4627] based data structures. The JWE cryptographic mechanisms encrypt and provide integrity protection for arbitrary sequences of octets.
Two closely related representations 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) [JWA] specification. Related digital signature and MAC capabilities are described in the separate JSON Web Signature (JWS) [JWS] specification.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in Key words for use in RFCs to Indicate Requirement Levels [RFC2119].
JWE represents encrypted content using JSON data structures and base64url encoding. Five values are represented in a JWE: the JWE Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, and the JWE Authentication Tag. In the Compact Serialization, the five values are base64url-encoded for transmission, and represented as the concatenation of the encoded strings in that order, with the five strings being separated by four period ('.') characters. A JSON Serialization for this information is also defined in Section 7.2.
JWE utilizes authenticated encryption to ensure the confidentiality and integrity of the Plaintext and the integrity of the JWE Protected Header.
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 Header declares that:
{"alg":"RSA-OAEP","enc":"A256GCM"}
Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
The remaining steps to finish creating this JWE are:
The final result in this example (with line breaks for display purposes only) is:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ. OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8 1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi 6UklfCpIMfIjf7iGdXKHzg. 48V1_ALb6US04U3b. 5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji SdiwkIr3ajwQzaBtQD_A. XFBoMYUZodetZdvTiFvSkQ
See Appendix A.1 for the complete details of computing this JWE. See Appendix A 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 [ECMAScript].
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 Section 4.1.12, all header parameters not defined by this specification MUST be ignored when not understood.
There are three classes of Header Parameter Names: Reserved Header Parameter Names, Public Header Parameter Names, and Private Header Parameter Names.
The following Header Parameter Names are reserved with meanings as defined below. All the names are short because a core goal of this specification is for the resulting representations using the JWE Compact Serialization to be compact.
Additional reserved Header Parameter Names can be defined via the IANA JSON Web Signature and Encryption Header Parameters registry [JWS]. 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 a cryptographic algorithm used to encrypt or determine the value of the Content Encryption Key (CEK). The recipient MUST reject the JWE 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. alg values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry [JWA] or be a value that contains a Collision Resistant Namespace. The alg value is a case sensitive string containing a StringOrURI value. Use of this header parameter is REQUIRED. This header parameter MUST be understood by implementations.
A list of defined alg values can be found in the IANA JSON Web Signature and Encryption Algorithms registry [JWA]; the initial contents of this registry are the values defined in Section 4.1 of the JSON Web Algorithms (JWA) [JWA] specification.
The enc (encryption method) 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 [JWA] or be a value that contains a Collision Resistant Namespace. The enc value is a case sensitive string containing a StringOrURI value. Use of this header parameter is REQUIRED. This header parameter MUST be understood by implementations.
A list of defined enc values can be found in the IANA JSON Web Signature and Encryption Algorithms registry [JWA]; the initial contents of this registry are the values defined in Section 4.2 of the JSON Web Algorithms (JWA) [JWA] specification.
The zip (compression algorithm) applied to the Plaintext before encryption, if any. If present, the value of the zip header parameter MUST be the case sensitive string "DEF". Compression is performed with the DEFLATE [RFC1951] algorithm. 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 with the JWE Protected Header, when used. Use of this header parameter is OPTIONAL. This header parameter MUST be understood by implementations.
The jku (JWK Set URL) header parameter is a URI [RFC3986] that refers to a resource for a set of JSON-encoded public keys, one of which is the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. The keys MUST be encoded as a JSON Web Key Set (JWK Set) [JWK]. The protocol used to acquire the resource MUST provide integrity protection; an HTTP GET request to retrieve the JWK Set MUST use TLS [RFC2818] [RFC5246]; the identity of the server MUST be validated, as per Section 3.1 of HTTP Over TLS [RFC2818]. Use of this header parameter is OPTIONAL.
The jwk (JSON Web Key) header parameter 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 key is represented as a JSON Web Key [JWK]. Use of this header parameter is OPTIONAL.
The x5u (X.509 URL) header parameter is a URI [RFC3986] that refers to a resource for the X.509 public key certificate or certificate chain [RFC5280] containing the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. The identified resource MUST provide a representation of the certificate or certificate chain that conforms to RFC 5280 [RFC5280] in PEM encoded form [RFC1421]. The certificate containing the public key to which the JWE was encrypted 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 [RFC2818] [RFC5246]; the identity of the server MUST be validated, as per Section 3.1 of HTTP Over TLS [RFC2818]. Use of this header parameter is OPTIONAL.
The x5t (X.509 Certificate Thumbprint) header parameter is a base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER encoding of the X.509 certificate [RFC5280] containing the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. Use of this header parameter is OPTIONAL.
If, in the future, certificate thumbprints need to be computed using hash functions other than SHA-1, it is suggested that additional related header parameters be defined for that purpose. For example, it is suggested that a new x5t#S256 (X.509 Certificate Thumbprint using SHA-256) header parameter could be defined by registering it in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS].
The x5c (X.509 Certificate Chain) header parameter contains the X.509 public key certificate or certificate chain [RFC5280] containing the key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. The certificate or certificate chain is represented as a JSON array of certificate value strings. Each string in the array is a base64 encoded ([RFC4648] Section 4 -- not base64url encoded) DER [ITU.X690.1994] PKIX certificate value. The certificate containing the public key to which the JWE was encrypted 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. Use of this header parameter is OPTIONAL.
See Appendix B of [JWS] for an example x5c value.
The kid (key ID) header parameter is a hint indicating which 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 recipients. Should the recipient be unable to locate a key corresponding to the kid value, they SHOULD treat that condition as an error. The interpretation of the kid value is unspecified. Its value MUST be a string. Use of this header parameter is OPTIONAL.
When used with a JWK, the kid value can be used to match a JWK kid parameter value.
The typ (type) header parameter MAY be used to declare the type of this complete JWE object in an application-specific manner in contexts where this is useful to the application. This parameter has no effect upon the JWE processing. The type value JOSE MAY be used to indicate that this object is a JWS or JWE using the JWS Compact Serialization or the JWE Compact Serialization. The type value JOSE+JSON MAY be used to indicate that this object is a JWS or JWE using the JWS JSON Serialization or the JWE JSON Serialization. Other type values MAY be used, and if not understood, SHOULD be ignored. The typ value is a case sensitive string. Use of this header parameter is OPTIONAL.
MIME Media Type [RFC2046] values MAY be used as typ values.
typ values SHOULD either be registered in the IANA JSON Web Signature and Encryption Type Values registry [JWS] or be a value that contains a Collision Resistant Namespace.
The cty (content type) header parameter MAY be used to declare the type of the encrypted content (the Plaintext) in an application-specific manner in contexts where this is useful to the application. This parameter has no effect upon the JWE processing. Content type values that are not understood SHOULD be ignored. The cty value is a case sensitive string. Use of this header parameter is OPTIONAL.
The values used for the cty header parameter come from the same value space as the typ header parameter, with the same rules applying.
The crit (critical) header parameter indicates that extensions to [[ this specification ]] are being used that MUST be understood and processed. Its value is an array listing the header parameter names defined by those extensions that are used in the JWE Header. If any of the listed extension header parameters are not understood and supported by the receiver, it MUST reject the JWE. Senders MUST NOT include header parameter names defined by [[ this specification ]] or by [JWA] for use with JWE, duplicate names, or names that do not occur as header parameter names within the JWE Header in the crit list. Senders MUST not use the empty list [] as the crit value. Recipients MAY reject the JWE if the critical list contains any header parameter names defined by [[ this specification ]] or by [JWA] for use with JWE, or any other constraints on its use are violated. This header parameter MUST be integrity protected, and therefore MUST occur only with the JWE Protected Header, when used. Use of this header parameter is OPTIONAL. This header parameter MUST be understood by implementations.
An example use, along with a hypothetical exp (expiration-time) field is:
{"alg":"RSA-OAEP",
"enc":"A256GCM",
"crit":["exp"],
"exp":1363284000
}
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 [JWS] or be a Public Name: a value that contains a Collision Resistant Namespace. 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 Reserved Names Section 4.1 or Public Names Section 4.2. Unlike Public Names, Private 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.
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 JWE MUST be rejected.
Processing a JWE inevitably requires comparing known strings to values in JSON objects. For example, in checking what the encryption method is, the Unicode string encoding enc will be checked against the member names in the JWE Header to see if there is a matching Header Parameter Name.
Comparisons between JSON strings and other Unicode strings MUST be performed by comparing Unicode code points without normalization as specified in the String Comparison Rules in Section 5.3 of [JWS].
It is necessary for the recipient of a JWE to be able to determine the key that was employed for the encryption operation. The key employed can be identified using the Header Parameter methods described in Section 4.1 or can be identified using methods that are outside the scope of this specification. Specifically, the Header Parameters jku, jwk, x5u, x5t, x5c, and kid can be used to identify the key used. The sender 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. Recipients MUST reject the input when the key used cannot be determined.
JWE objects use one of two serializations, the JWE Compact Serialization or the JWE JSON Serialization. The JWE Compact Serialization is mandatory to implement. Implementation of the JWE JSON Serialization is OPTIONAL.
The JWE Compact Serialization represents encrypted content as a compact URL-safe string. This string is the concatenation of the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag in that order, with the five strings being separated by four period ('.') characters. Only one recipient is supported by the JWE Compact Serialization.
The JWE JSON Serialization represents encrypted content as a JSON object. Unlike the JWE Compact Serialization, content using the JWE JSON Serialization can be encrypted to more than one recipient.
The representation is closely related to that used in the JWE Compact Serialization, with the following differences for the JWE JSON Serialization:
The syntax of a JWE using the JWE JSON Serialization is as follows:
{"protected":<integrity-protected shared header contents>",
"unprotected":<non-integrity-protected shared header contents>",
"recipients":[
{"header":"<per-recipient unprotected header 1 contents>",
"encrypted_key":"<encrypted key 1 contents>"},
...
{"header":"<per-recipient unprotected header N contents>",
"encrypted_key":"<encrypted key N contents>"}],
"aad":"<additional authenticated data contents>",
"iv":"<initialization vector contents>",
"ciphertext":"<ciphertext contents>",
"tag":"<authentication tag contents>"
}
Of these members, only the ciphertext member MUST be present. The iv, tag, and encrypted_key members MUST be present when corresponding JWE Initialization Vector, JWE Authentication Tag, and JWE Encrypted Key values are non-empty. The recipients member MUST be present when any header or encrypted_key members are needed for recipients. 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.
The contents of the Encoded JWE Encrypted Key, Encoded JWE Initialization Vector, Encoded JWE Ciphertext, and Encoded JWE Authentication Tag values are exactly as defined in the rest of this specification. They are interpreted and validated in the same manner, with each corresponding Encoded JWE Encrypted Key, Encoded JWE Initialization Vector, Encoded JWE Ciphertext, Encoded JWE Authentication Tag, and set of header parameter values being created and validated together. The JWE Header values used are the union of the header parameters in the protected, unprotected, and corresponding header members, as described earlier.
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 Encoded 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 Encoded JWE 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, 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 method) header parameter value in the JWE Header for each recipient and any parameters of that algorithm MUST be the same.
See Appendix A.4 for an example of computing a JWE using the JWE JSON Serialization.
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.
This specification registers the Header Parameter Names defined in Section 4.1 in the IANA JSON Web Signature and Encryption Header Parameters registry [JWS].
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 [W3C.CR-xmlenc-core1-20120313] 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 [RFC3218] 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 JWE is rejected.
| [RFC3218] | Rescorla, E., "Preventing the Million Message Attack on Cryptographic Message Syntax", RFC 3218, January 2002. |
| [RFC4122] | Leach, P., Mealling, M. and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, July 2005. |
| [RFC5652] | Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, September 2009. |
| [I-D.rescorla-jsms] | Rescorla, E. and J. Hildebrand, "JavaScript Message Security Format", Internet-Draft draft-rescorla-jsms-00, March 2011. |
| [I-D.mcgrew-aead-aes-cbc-hmac-sha2] | McGrew, D. and K. Paterson, "Authenticated Encryption with AES-CBC and HMAC-SHA", Internet-Draft draft-mcgrew-aead-aes-cbc-hmac-sha2-01, October 2012. |
| [JSE] | Bradley, J. and N. Sakimura (editor), "JSON Simple Encryption", September 2010. |
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 Header declares that:
{"alg":"RSA-OAEP","enc":"A256GCM"}
Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ
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 [JWK] format below (with line breaks for display purposes only):
{"kty":"RSA",
"n":"oahUIoWw0K0usKNuOR6H4wkf4oBUXHTxRvgb48E-BVvxkeDNjbC4he8rUW
cJoZmds2h7M70imEVhRU5djINXtqllXI4DFqcI1DgjT9LewND8MW2Krf3S
psk_ZkoFnilakGygTwpZ3uesH-PFABNIUYpOiN15dsQRkgr0vEhxN92i2a
sbOenSZeyaxziK72UwxrrKoExv6kc5twXTq4h-QChLOln0_mtUZwfsRaMS
tPs6mS6XrgxnxbWhojf663tuEQueGC-FCMfra36C9knDFGzKsNa7LZK2dj
YgyD3JR_MB_4NUJW_TqOQtwHYbxevoJArm-L5StowjzGy-_bq6Gw",
"e":"AQAB",
"d":"kLdtIj6GbDks_ApCSTYQtelcNttlKiOyPzMrXHeI-yk1F7-kpDxY4-WY5N
WV5KntaEeXS1j82E375xxhWMHXyvjYecPT9fpwR_M9gV8n9Hrh2anTpTD9
3Dt62ypW3yDsJzBnTnrYu1iwWRgBKrEYY46qAZIrA2xAwnm2X7uGR1hghk
qDp0Vqj3kbSCz1XyfCs6_LehBwtxHIyh8Ripy40p24moOAbgxVw3rxT_vl
t3UVe4WO3JkJOzlpUf-KTVI2Ptgm-dARxTEtE-id-4OJr0h-K-VFs3VSnd
VTIznSxfyrj8ILL6MG_Uv8YAu7VILSB3lOW085-4qE3DzgrTjgyQ"
}
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]
Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key. This result (with line breaks for display purposes only) is:
OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8 1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi 6UklfCpIMfIjf7iGdXKHzg
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]
Base64url encoding this value yields this Encoded JWE Initialization Vector value:
48V1_ALb6US04U3b
Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value. This AAD 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]
Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result (with line breaks for display purposes only) is:
5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji SdiwkIr3ajwQzaBtQD_A
Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is:
XFBoMYUZodetZdvTiFvSkQ
Assemble the final representation: The Compact Serialization of this result is the concatenation of the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag in that order, with the five strings being separated by four period ('.') characters.
The final result in this example (with line breaks for display purposes only) is:
eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ. OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8 1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi 6UklfCpIMfIjf7iGdXKHzg. 48V1_ALb6US04U3b. 5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji SdiwkIr3ajwQzaBtQD_A. XFBoMYUZodetZdvTiFvSkQ
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 Header (with line breaks for display purposes only) declares that:
{"alg":"RSA1_5","enc":"A128CBC-HS256"}
Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value:
eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
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 [JWK] format below (with line breaks for display purposes only):
{"kty":"RSA",
"n":"sXchDaQebHnPiGvyDOAT4saGEUetSyo9MKLOoWFsueri23bOdgWp4Dy1Wl
UzewbgBHod5pcM9H95GQRV3JDXboIRROSBigeC5yjU1hGzHHyXss8UDpre
cbAYxknTcQkhslANGRUZmdTOQ5qTRsLAt6BTYuyvVRdhS8exSZEy_c4gs_
7svlJJQ4H9_NxsiIoLwAEk7-Q3UXERGYw_75IDrGA84-lA_-Ct4eTlXHBI
Y2EaV7t7LjJaynVJCpkv4LKjTTAumiGUIuQhrNhZLuF_RJLqHpM2kgWFLU
7-VTdL1VbC2tejvcI2BlMkEpk1BzBZI0KQB0GaDWFLN-aEAw3vRw",
"e":"AQAB",
"d":"VFCWOqXr8nvZNyaaJLXdnNPXZKRaWCjkU5Q2egQQpTBMwhprMzWzpR8Sxq
1OPThh_J6MUD8Z35wky9b8eEO0pwNS8xlh1lOFRRBoNqDIKVOku0aZb-ry
nq8cxjDTLZQ6Fz7jSjR1Klop-YKaUHc9GsEofQqYruPhzSA-QgajZGPbE_
0ZaVDJHfyd7UUBUKunFMScbflYAAOYJqVIVwaYR5zWEEceUjNnTNo_CVSj
-VvXLO5VZfCUAVLgW4dpf1SrtZjSt34YLsRarSb127reG_DUwg9Ch-Kyvj
T1SkHgUWRVGcyly7uvVGRSDwsXypdrNinPA4jlhoNdizK2zF2CWQ"
}
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]
Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key. This result (with line breaks for display purposes only) is:
UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm 1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8 rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv -B3oWh2TbqmScqXMR4gp_A
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]
Base64url encoding this value yields this Encoded JWE Initialization Vector value:
AxY8DCtDaGlsbGljb3RoZQ
Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value. This AAD 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 Appendix A.3 are detailed in Appendix B. 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]
Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result is:
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is:
9hH0vgRfYgPnAHOd8stkvw
Assemble the final representation: The Compact Serialization of this result is the concatenation of the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag in that order, with the five strings being separated by four period ('.') characters.
The final result in this example (with line breaks for display purposes only) is:
eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0. UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm 1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8 rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv -B3oWh2TbqmScqXMR4gp_A. AxY8DCtDaGlsbGljb3RoZQ. KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY. 9hH0vgRfYgPnAHOd8stkvw
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 GCM 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 Header declares that:
{"alg":"A128KW","enc":"A128CBC-HS256"}
Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value:
eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
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 [JWK] format below:
{"kty":"oct",
"k":"GawgguFyGrWKav7AX4VKUg"
}
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]
Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key. This result is:
6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ
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]
Base64url encoding this value yields this Encoded JWE Initialization Vector value:
AxY8DCtDaGlsbGljb3RoZQ
Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value. This AAD 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 Appendix B. 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]
Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result is:
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is:
U0m_YmjN04DJvceFICbCVQ
Assemble the final representation: The Compact Serialization of this result is the concatenation of the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag in that order, with the five strings being separated by four period ('.') characters.
The final result in this example (with line breaks for display purposes only) is:
eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0. 6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ. AxY8DCtDaGlsbGljb3RoZQ. KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY. U0m_YmjN04DJvceFICbCVQ
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 Appendix A.2. The algorithm and key used for the second recipient are the same as that used in Appendix A.3. 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 RSAES OAEP 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:
{"alg":"RSA1_5","kid":"2011-04-29"}
and:
{"alg":"A128KW","kid":"7"}
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:
{"enc":"A128CBC-HS256"}
Base64url encoding the octets of the UTF-8 representation of the JWE Protected Header yields this Encoded JWE Protected Header value:
eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0
This JWE uses the jku header parameter to reference a JWK Set. This is represented in the following JWE Unprotected Header value as:
{"jku":"https://server.example.com/keys.jwks"}
Combining the per-recipient, protected, and unprotected header values supplied, the JWE Header values used for the first and second recipient respectively are:
{"alg":"RSA1_5",
"kid":"2011-04-29",
"enc":"A128CBC-HS256",
"jku":"https://server.example.com/keys.jwks"}
and:
{"alg":"A128KW",
"kid":"7",
"enc":"A128CBC-HS256",
"jku":"https://server.example.com/keys.jwks"}
Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Protected Header value. This AAD 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 Appendix A.3 are detailed in Appendix B. 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]
Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result is:
KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY
Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is:
Mz-VPPyU4RlcuYv1IwIvzw
The complete JSON Web Encryption JSON Serialization for these values is as follows (with line breaks for display purposes only):
{"protected":
"eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0",
"unprotected":
{"jku":"https://server.example.com/keys.jwks"},
"recipients":[
{"header":
{"alg":"RSA1_5"},
"encrypted_key":
"UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-
kFm1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKx
GHZ7PcHALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3
YvkkysZIFNPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPh
cCdZ6XDP0_F8rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPg
wCp6X-nZZd9OHBv-B3oWh2TbqmScqXMR4gp_A"},
{"header":
{"alg":"A128KW"},
"encrypted_key":
"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"}],
"iv":
"AxY8DCtDaGlsbGljb3RoZQ",
"ciphertext":
"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY",
"tag":
"Mz-VPPyU4RlcuYv1IwIvzw"
}
This example shows the steps in the AES_128_CBC_HMAC_SHA_256 authenticated encryption computation using the values from the example in Appendix A.3. As described where this algorithm is defined in Sections 4.8 and 4.8.3 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 [JSE] and JavaScript Message Security Format [I-D.rescorla-jsms], both of which significantly influenced this draft. This draft attempts to explicitly reuse as many of the relevant concepts from XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313] and RFC 5652 [RFC5652] as possible, while utilizing simple, compact JSON-based data structures.
Special thanks are due to John Bradley and Nat Sakimura for the discussions that helped inform the content of this specification and to Eric Rescorla and Joe Hildebrand for allowing the reuse of text from [I-D.rescorla-jsms] in this document.
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, Axel Nennker, Emmanuel Raviart, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and Sean Turner and Stephen Farrell served as Security area directors during the creation of this specification.
[[ to be removed by the RFC editor before publication as an RFC ]]
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