Microsoft

mbj@microsoft.com http://self-issued.info/

Cisco Systems, Inc.

jhildebr@cisco.com

Security JOSE Working Group RFC Request for Comments I-D Internet-Draft JavaScript Object Notation JSON JSON Object Signing and Encryption JOSE JSON Web Signature JWS JSON Web Encryption JWE JSON Web Key JWK JSON Web Algorithms JWA JSON Web Encryption (JWE) represents encrypted content using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries defined by that specification. Related digital signature and Message Authentication Code (MAC) capabilities are described in the separate JSON Web Signature (JWS) specification.

JSON Web Encryption (JWE) represents encrypted content using JSON-based data structures . The JWE cryptographic mechanisms encrypt and provide integrity protection for an arbitrary sequence of octets. Two closely related serializations for JWEs 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 JWEs 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" . The interpretation should only be applied when the terms appear in all capital letters. BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per Section 2 of . UTF8(STRING) denotes the octets of the UTF-8 representation of STRING, where STRING is a sequence of zero or more Unicode characters. ASCII(STRING) denotes the octets of the ASCII representation of STRING, where STRING is a sequence of zero or more ASCII characters. The concatenation of two values A and B is denoted as A || B.

The terms "JSON Web Signature (JWS)", "Base64url Encoding", "Collision-Resistant Name", "Header Parameter", "JOSE Header", and "StringOrURI" are defined by the JWS specification . The terms "Ciphertext", "Digital Signature", "Initialization Vector (IV)", "Message Authentication Code (MAC)", and "Plaintext" are defined by the "Internet Security Glossary, Version 2". These terms are defined 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. 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 to produce the ciphertext and the Authentication Tag. Encrypted Content Encryption Key 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 the JWE Compact Serialization or the JWE JSON 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. JSON object that contains the 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 JOSE Header. For the JWE JSON Serialization, this is one component of the JOSE Header. JSON object that contains the 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 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 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 CEK value is encrypted to the intended recipient using an asymmetric encryption algorithm. A Key Management Mode in which the 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 CEK value. A Key Management Mode in which a key agreement algorithm is used to agree upon a symmetric key used to encrypt the CEK value to the intended recipient using a symmetric key wrapping algorithm. A Key Management Mode in which the CEK value used is the secret symmetric key value shared between the parties.

JWE represents encrypted content using JSON data structures and base64url encoding. These JSON data structures MAY contain whitespace and/or line breaks before or after any JSON values or structural characters, in accordance with Section 2 of RFC 7159. A JWE represents these logical values (each of which is defined in ): JOSE Header JWE Encrypted Key JWE Initialization Vector JWE AAD JWE Ciphertext JWE Authentication Tag For a JWE, the JOSE Header members are the union of the members of these values (each of which is defined in ): JWE Protected Header JWE Shared Unprotected Header JWE Per-Recipient Unprotected Header 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 document defines two serializations for JWEs: 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, since JSON lacks a way to directly represent arbitrary octet sequences. When present, the JWE AAD is also base64url encoded.

In the JWE Compact Serialization, no JWE Shared Unprotected Header or JWE Per-Recipient Unprotected Header are used. In this case, the JOSE Header and the JWE Protected Header are the same. In the JWE Compact Serialization, a JWE is represented as the concatenation: BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag) See for more information about the JWE Compact Serialization.

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 JOSE Header are the union 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 is represented as a JSON object containing some or all of these eight members: protected, with the value BASE64URL(UTF8(JWE Protected Header)) unprotected, with the value JWE Shared Unprotected Header header, with the value JWE Per-Recipient Unprotected Header encrypted_key, with the value BASE64URL(JWE Encrypted Key) iv, with the value BASE64URL(JWE Initialization Vector) ciphertext, with the value BASE64URL(JWE Ciphertext) tag, with the value BASE64URL(JWE Authentication Tag) aad, with the value BASE64URL(JWE AAD) The six base64url-encoded result strings and the two unprotected JSON object values are 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.

This example encrypts the plaintext "The true sign of intelligence is not knowledge but imagination." to the recipient. 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. Authenticated encryption is performed on the plaintext using the AES GCM algorithm with a 256-bit key to produce the ciphertext and the Authentication Tag.

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))). Perform authenticated encryption on the plaintext with the AES GCM algorithm 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 for additional examples, including examples using the JWE JSON Serialization in Sections and .

For a JWE, the members of the JSON object(s) representing the JOSE Header describe the encryption applied to the plaintext and optionally additional properties of the JWE. The Header Parameter names within the JOSE Header MUST be unique, just as described in Section 4 of . The rules about handling Header Parameters that are not understood by the implementation are also the same. The classes of Header Parameter names are likewise the same.

The following Header Parameter names for use in JWEs are registered in the IANA "JSON Web Signature and Encryption Header Parameters" registry established by , 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 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 established by ; the initial contents of this registry are the values defined in Section 4.1 of .

The enc (encryption algorithm) Header Parameter identifies the content encryption algorithm used to perform authenticated encryption on the plaintext to produce the ciphertext and the Authentication Tag. This algorithm MUST be an AEAD algorithm with a specified key length. The encrypted content is not usable 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 established by or be a value that contains a Collision-Resistant Name. The enc value is a case-sensitive ASCII string containing a StringOrURI value. This Header Parameter MUST be present and MUST be understood and processed by implementations. A list of defined enc values for this use can be found in the IANA "JSON Web Signature and Encryption Algorithms" registry established by ; the initial contents of this registry are the values defined in Section 5.1 of .

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 Algorithms" registry established by . The zip value is a case-sensitive string. If no zip parameter is present, no compression is applied to the plaintext before encryption. When used, this Header Parameter MUST be integrity protected; therefore, it MUST occur only within the JWE Protected Header. 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 the 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. Note that certificate thumbprints are also sometimes known as certificate fingerprints.

This parameter has the same meaning, syntax, and processing rules as the x5t#S256 Header Parameter defined in Section 4.1.8 of , except that the 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. Note that certificate thumbprints are also sometimes known as certificate fingerprints.

This parameter has the same meaning, syntax, and processing rules as the typ Header Parameter defined in Section 4.1.9 of , except that the type is that of this complete JWE.

This parameter has the same meaning, syntax, and processing rules as the cty Header Parameter defined in Section 4.1.10 of , except that the type is that of the secured content (the plaintext).

This parameter has the same meaning, syntax, and processing rules as the crit Header Parameter defined in Section 4.1.11 of , except that Header Parameters for a JWE are being referred to, rather than Header Parameters for a JWS.

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 established by or be a Public Name: a value that contains a Collision-Resistant Name. In each case, the definer of the name or value needs to take reasonable precautions to make sure they are in control of the part of the namespace they use to define the Header Parameter name. New Header Parameters should be introduced sparingly, as they can result in non-interoperable 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 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 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 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 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 and let M be the octet sequence representing the compressed plaintext; otherwise, let M be the octet sequence representing the plaintext. Create the JSON object(s) containing the desired set of Header Parameters, which together comprise the JOSE Header: one or more of the JWE Protected Header, 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). 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 fail, the encrypted content cannot be validated. When there are multiple recipients, it is an application decision which of the 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 considered invalid. 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 considered invalid. Parse the JWE representation to extract the serialized values for the components of the JWE. When using the JWE Compact Serialization, these components are 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, these components also include 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, with each value being separated from the next by a single period ('.') character, resulting in exactly four delimiting period characters being used. The JWE JSON Serialization is described in . Base64url decode 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, following the restriction that no line breaks, whitespace, or other additional characters have been used. Verify that the octet sequence resulting from decoding the encoded JWE Protected Header is a UTF-8-encoded representation of a completely valid JSON object conforming to RFC 7159; let the JWE Protected Header be this JSON object. If using the JWE Compact Serialization, let the JOSE Header be the JWE Protected Header. Otherwise, when using the JWE JSON Serialization, let the JOSE 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. During this step, verify that the resulting JOSE Header does 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 JOSE Header. Verify that the implementation understands and can process all fields that it is required to support, whether required by this specification, by the 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 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 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 to decrypt 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. Also, see for security considerations on mitigating timing attacks. When Direct Key Agreement or Direct Encryption are employed, verify that the JWE Encrypted Key value is an empty octet sequence. When Direct Encryption is employed, let the CEK be the shared symmetric key. Record whether the CEK could be successfully determined for this recipient or not. If the JWE JSON Serialization is being used, repeat this process (steps 4-12) for each recipient contained in the representation. 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 there was no recipient for which all of the decryption steps succeeded, then the JWE MUST be considered invalid. Otherwise, output the plaintext. In the JWE JSON Serialization case, also return a result to the application indicating for which of the recipients the decryption succeeded and failed. Finally, note that it is an application decision which algorithms may be used in a given context. Even if a JWE can be successfully decrypted, unless the algorithms used in the JWE are acceptable to the application, it SHOULD consider the JWE to be invalid.

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.

JWEs 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. This representation is neither optimized for compactness nor URL safe. Two closely related syntaxes are defined for the JWE JSON Serialization: a fully general syntax, with which content can be encrypted to more than one recipient, and a flattened syntax, which is optimized for the single-recipient case.

The following members are defined for use in top-level JSON objects used for the fully general JWE JSON Serialization syntax: 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 with exactly one array element per recipient, even if some or all of the array element values are 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 JOSE 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 JOSE 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 JOSE Header for each recipient and any parameters of that algorithm MUST be the same.

In summary, the syntax of a JWE using the general JWE JSON Serialization is as follows: ", "unprotected":, "recipients":[ {"header":, "encrypted_key":""}, ... {"header":, "encrypted_key":""}], "aad":"", "iv":"", "ciphertext":"", "tag":"" } ]]>

See for an example JWE using the general JWE JSON Serialization syntax.

The flattened JWE JSON Serialization syntax is based upon the general syntax, but flattens it, optimizing it for the single-recipient case. It flattens it by removing the recipients member and instead placing those members defined for use in the recipients array (the header and encrypted_key members) in the top-level JSON object (at the same level as the ciphertext member). The recipients member MUST NOT be present when using this syntax. Other than this syntax difference, JWE JSON Serialization objects using the flattened syntax are processed identically to those using the general syntax.

In summary, the syntax of a JWE using the flattened JWE JSON Serialization is as follows: ", "unprotected":, "header":, "encrypted_key":"", "aad":"", "iv":"", "ciphertext":"", "tag":"" } ]]>

Note that when using the flattened syntax, just as when using the general syntax, any unprotected Header Parameter values can reside in either the unprotected member or the header member, or in both. See for an example JWE using the flattened JWE JSON Serialization syntax.

The Transport Layer Security (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. 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 payload member and JWEs do not. JWEs have a ciphertext member and JWSs do not. The JOSE Header for a JWS can be distinguished from the JOSE Header for a JWE 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.) The JOSE Header for a JWS can also be distinguished from the JOSE Header for a JWE by determining whether an enc (encryption algorithm) member exists. If the enc member exists, it is a JWE; otherwise, it is a JWS.

This section registers the Header Parameter names defined in in the IANA "JSON Web Signature and Encryption Header Parameters" registry established by .

Header Parameter Name: alg Header Parameter Description: Algorithm Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: enc Header Parameter Description: Encryption Algorithm Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: zip Header Parameter Description: Compression Algorithm Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: jku Header Parameter Description: JWK Set URL Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: jwk Header Parameter Description: JSON Web Key Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: kid Header Parameter Description: Key ID Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: x5u Header Parameter Description: X.509 URL Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: x5c Header Parameter Description: X.509 Certificate Chain Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 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 RFC 7516 Header Parameter Name: x5t#S256 Header Parameter Description: X.509 Certificate SHA-256 Thumbprint Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: typ Header Parameter Description: Type Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: cty Header Parameter Description: Content Type Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516 Header Parameter Name: crit Header Parameter Description: Critical Header Parameter Usage Location(s): JWE Change Controller: IESG Specification Document(s): of RFC 7516

All of the security issues that are pertinent to any cryptographic application must be addressed by JWS/JWE/JWK agents. Among these issues are protecting the user's asymmetric private and symmetric secret keys and employing countermeasures to various attacks. All the security considerations in 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.

See Section 10.1 of for security considerations on key entropy and random values. In addition to the uses of random values listed there, note that random values are also used for Content Encryption Keys (CEKs) and Initialization Vectors (IVs) when performing encryption.

See Section 10.2 of for security considerations on key protection. In addition to the keys listed there that must be protected, implementations performing encryption must protect the key encryption key and the Content Encryption Key. Compromise of the key encryption key may result in the disclosure of all contents protected with that key. Similarly, compromise of the Content Encryption Key may result in disclosure of the associated encrypted content.

Algorithms of matching strengths should be used together whenever possible. For instance, when AES Key Wrap is used with a given key size, using the same key size is recommended when AES GCM is also used. If the key encryption and content encryption algorithms are different, the effective security is determined by the weaker of the two algorithms. Also, see RFC 3766 for information on determining strengths for public keys used for exchanging symmetric keys.

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 Header 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 restricting 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&nbhy;OAEP only, any attempt to decrypt a message using the RSA1_5 algorithm with that key should fail immediately due to invalid use of the key.

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 recipient substitute a randomly generated CEK and proceed to the next step, to mitigate timing attacks.

University California Los Angeles (UCLA) The Unicode Consortium

Microsoft

mbj@microsoft.com http://self-issued.info/

Ping Identity

ve7jtb@ve7jtb.com

Nomura Research Institute

n-sakimura@nri.co.jp

Microsoft

mbj@microsoft.com http://self-issued.info/

Microsoft

mbj@microsoft.com http://self-issued.info/

National Institute of Standards and Technology (NIST) National Institute of Standards and Technology (NIST) independent Nomura 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 (using JSON array notation) 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. Authenticated encryption is performed on the plaintext using the AES GCM algorithm with a 256-bit key to produce the ciphertext and the Authentication Tag.

Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this value:

Generate a 256-bit random CEK. In this example, the value (using JSON array notation) 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&nbhy;OAEP algorithm to produce the JWE Encrypted Key. This example uses the RSA key represented in JSON Web Key format below (with line breaks within values 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]

Perform authenticated encryption on the plaintext with the AES GCM algorithm 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&nbhy;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 (using JSON array notation) 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. Authenticated encryption is performed on the plaintext using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the ciphertext and the Authentication Tag.

Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this value:

Generate a 256-bit random 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&nbhy;PKCS1&nbhy;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 within values 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]

Perform authenticated encryption on the plaintext with the AES_128_CBC_HMAC_SHA_256 algorithm 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&nbhy;PKCS1&nbhy;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&nbhy;PKCS1&nbhy;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 (using JSON array notation) 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. Authenticated encryption is performed on the plaintext using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the ciphertext and the Authentication Tag.

Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this value:

Generate a 256-bit random 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]

Perform authenticated encryption on the plaintext with the AES_128_CBC_HMAC_SHA_256 algorithm 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 general JWE JSON Serialization syntax. 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 CEK, JWE 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 CEK. The second uses AES Key Wrap to encrypt the CEK. Key ID values are supplied for both keys. The two JWE Per-Recipient Unprotected Header values used to represent these algorithms and key IDs are:

and

Authenticated encryption is performed on the plaintext 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 Shared Unprotected Header value as:

Combining the JWE Per-Recipient Unprotected Header, JWE Protected Header, and JWE Shared Unprotected Header values supplied, the JOSE 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]

Perform authenticated encryption on the plaintext with the AES_128_CBC_HMAC_SHA_256 algorithm 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 JWE JSON Serialization for these values is as follows (with line breaks within values for display purposes only):

This section contains an example using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure. The values in this example are the same as those for the second recipient of the previous example in . The complete JWE JSON Serialization for these values is as follows (with line breaks within values 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 Public-Key Cryptography Standards (PKCS) #7 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 (using JSON array notation) 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 CBC mode using PKCS #7 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 document. This document 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, Alissa Cooper, Breno de Medeiros, Stephen Farrell, Dick Hardt, Jeff Hodges, Russ Housley, Edmund Jay, Scott Kelly, Stephen Kent, Barry Leiba, James Manger, Matt Miller, Kathleen Moriarty, Tony Nadalin, Hideki Nara, Axel Nennker, Ray Polk, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner. Jim Schaad and Karen O'Donoghue chaired the JOSE working group and Sean Turner, Stephen Farrell, and Kathleen Moriarty served as Security Area Directors during the creation of this specification.