JOSE Working Group M. Jones Internet-Draft Microsoft Intended status: Standards Track E. Rescorla Expires: March 19, 2014 RTFM J. Hildebrand Cisco September 15, 2013 JSON Web Encryption (JWE) draft-ietf-jose-json-web-encryption-16 Abstract JSON Web Encryption (JWE) represents encrypted content using JavaScript Object Notation (JSON) based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries defined by that specification. Related digital signature and MAC capabilities are described in the separate JSON Web Signature (JWS) specification. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on March 19, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Jones, et al. Expires March 19, 2014 [Page 1] Internet-Draft JWE September 2013 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. JSON Web Encryption (JWE) Overview . . . . . . . . . . . . . . 9 3.1. Example JWE . . . . . . . . . . . . . . . . . . . . . . . 9 4. JWE Header . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Registered Header Parameter Names . . . . . . . . . . . . 11 4.1.1. "alg" (Algorithm) Header Parameter . . . . . . . . . . 11 4.1.2. "enc" (Encryption Method) Header Parameter . . . . . . 12 4.1.3. "zip" (Compression Algorithm) Header Parameter . . . . 12 4.1.4. "jku" (JWK Set URL) Header Parameter . . . . . . . . . 12 4.1.5. "jwk" (JSON Web Key) Header Parameter . . . . . . . . 13 4.1.6. "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 13 4.1.7. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter . . . . . . . . . . . . . . . . . . . . . . 13 4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter . . . 14 4.1.9. "kid" (Key ID) Header Parameter . . . . . . . . . . . 14 4.1.10. "typ" (Type) Header Parameter . . . . . . . . . . . . 14 4.1.11. "cty" (Content Type) Header Parameter . . . . . . . . 15 4.1.12. "crit" (Critical) Header Parameter . . . . . . . . . . 15 4.2. Public Header Parameter Names . . . . . . . . . . . . . . 16 4.3. Private Header Parameter Names . . . . . . . . . . . . . . 16 5. Producing and Consuming JWEs . . . . . . . . . . . . . . . . . 16 5.1. Message Encryption . . . . . . . . . . . . . . . . . . . . 16 5.2. Message Decryption . . . . . . . . . . . . . . . . . . . . 18 5.3. String Comparison Rules . . . . . . . . . . . . . . . . . 21 6. Key Identification . . . . . . . . . . . . . . . . . . . . . . 21 7. Serializations . . . . . . . . . . . . . . . . . . . . . . . . 21 7.1. JWE Compact Serialization . . . . . . . . . . . . . . . . 21 7.2. JWE JSON Serialization . . . . . . . . . . . . . . . . . . 22 8. Distinguishing Between JWS and JWE Objects . . . . . . . . . . 25 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 9.1. JWE Header Parameter Names Registration . . . . . . . . . 25 9.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 26 10. Security Considerations . . . . . . . . . . . . . . . . . . . 27 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27 11.1. Normative References . . . . . . . . . . . . . . . . . . . 27 11.2. Informative References . . . . . . . . . . . . . . . . . . 29 Appendix A. JWE Examples . . . . . . . . . . . . . . . . . . . . 30 Jones, et al. Expires March 19, 2014 [Page 2] Internet-Draft JWE September 2013 A.1. Example JWE using RSAES OAEP and AES GCM . . . . . . . . . 30 A.1.1. JWE Header . . . . . . . . . . . . . . . . . . . . . . 30 A.1.2. Encoded JWE Header . . . . . . . . . . . . . . . . . . 30 A.1.3. Content Encryption Key (CEK) . . . . . . . . . . . . . 30 A.1.4. Key Encryption . . . . . . . . . . . . . . . . . . . . 31 A.1.5. Encoded JWE Encrypted Key . . . . . . . . . . . . . . 31 A.1.6. Initialization Vector . . . . . . . . . . . . . . . . 32 A.1.7. Additional Authenticated Data . . . . . . . . . . . . 32 A.1.8. Content Encryption . . . . . . . . . . . . . . . . . . 32 A.1.9. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 33 A.1.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 33 A.1.11. Complete Representation . . . . . . . . . . . . . . . 33 A.1.12. Validation . . . . . . . . . . . . . . . . . . . . . . 33 A.2. Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 34 A.2.1. JWE Header . . . . . . . . . . . . . . . . . . . . . . 34 A.2.2. Encoded JWE Header . . . . . . . . . . . . . . . . . . 34 A.2.3. Content Encryption Key (CEK) . . . . . . . . . . . . . 34 A.2.4. Key Encryption . . . . . . . . . . . . . . . . . . . . 34 A.2.5. Encoded JWE Encrypted Key . . . . . . . . . . . . . . 35 A.2.6. Initialization Vector . . . . . . . . . . . . . . . . 36 A.2.7. Additional Authenticated Data . . . . . . . . . . . . 36 A.2.8. Content Encryption . . . . . . . . . . . . . . . . . . 36 A.2.9. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 36 A.2.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 37 A.2.11. Complete Representation . . . . . . . . . . . . . . . 37 A.2.12. Validation . . . . . . . . . . . . . . . . . . . . . . 37 A.3. Example JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 37 A.3.1. JWE Header . . . . . . . . . . . . . . . . . . . . . . 38 A.3.2. Encoded JWE Header . . . . . . . . . . . . . . . . . . 38 A.3.3. Content Encryption Key (CEK) . . . . . . . . . . . . . 38 A.3.4. Key Encryption . . . . . . . . . . . . . . . . . . . . 38 A.3.5. Encoded JWE Encrypted Key . . . . . . . . . . . . . . 39 A.3.6. Initialization Vector . . . . . . . . . . . . . . . . 39 A.3.7. Additional Authenticated Data . . . . . . . . . . . . 39 A.3.8. Content Encryption . . . . . . . . . . . . . . . . . . 39 A.3.9. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 40 A.3.10. Encoded JWE Authentication Tag . . . . . . . . . . . . 40 A.3.11. Complete Representation . . . . . . . . . . . . . . . 40 A.3.12. Validation . . . . . . . . . . . . . . . . . . . . . . 40 A.4. Example JWE Using JWE JSON Serialization . . . . . . . . . 40 A.4.1. JWE Per-Recipient Unprotected Headers . . . . . . . . 41 A.4.2. JWE Protected Header . . . . . . . . . . . . . . . . . 41 A.4.3. JWE Unprotected Header . . . . . . . . . . . . . . . . 41 A.4.4. Complete JWE Header Values . . . . . . . . . . . . . . 42 A.4.5. Additional Authenticated Data . . . . . . . . . . . . 42 A.4.6. Content Encryption . . . . . . . . . . . . . . . . . . 42 Jones, et al. Expires March 19, 2014 [Page 3] Internet-Draft JWE September 2013 A.4.7. Encoded JWE Ciphertext . . . . . . . . . . . . . . . . 42 A.4.8. Encoded JWE Authentication Tag . . . . . . . . . . . . 43 A.4.9. Complete JWE JSON Serialization Representation . . . . 43 Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation . . . . 43 B.1. Extract MAC_KEY and ENC_KEY from Key . . . . . . . . . . . 44 B.2. Encrypt Plaintext to Create Ciphertext . . . . . . . . . . 44 B.3. 64 Bit Big Endian Representation of AAD Length . . . . . . 44 B.4. Initialization Vector Value . . . . . . . . . . . . . . . 45 B.5. Create Input to HMAC Computation . . . . . . . . . . . . . 45 B.6. Compute HMAC Value . . . . . . . . . . . . . . . . . . . . 45 B.7. Truncate HMAC Value to Create Authentication Tag . . . . . 45 Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 46 Appendix D. Document History . . . . . . . . . . . . . . . . . . 46 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 54 Jones, et al. Expires March 19, 2014 [Page 4] Internet-Draft JWE September 2013 1. Introduction JSON Web Encryption (JWE) represents encrypted content using JavaScript Object Notation (JSON) [RFC4627] based data structures. The JWE cryptographic mechanisms encrypt and provide integrity protection for an arbitrary sequence of octets. Two closely related serializations for JWE objects are defined. The JWE Compact Serialization is a compact, URL-safe representation intended for space constrained environments such as HTTP Authorization headers and URI query parameters. The JWE JSON Serialization represents JWE objects as JSON objects and enables the same content to be encrypted to multiple parties. Both share the same cryptographic underpinnings. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) [JWA] specification and IANA registries defined by that specification. Related digital signature and MAC capabilities are described in the separate JSON Web Signature (JWS) [JWS] specification. Names defined by this specification are short because a core goal is for the resulting representations to be compact. 1.1. Notational Conventions 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]. If these words are used without being spelled in uppercase then they are to be interpreted with their normal natural language meanings. 2. Terminology JSON Web Encryption (JWE) A data structure representing an encrypted message. The structure represents five values: the JWE Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, and the JWE Authentication Tag. Authenticated Encryption with Associated Data (AEAD) 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 Jones, et al. Expires March 19, 2014 [Page 5] Internet-Draft JWE September 2013 two outputs, the Ciphertext and the Authentication Tag value. AES Galois/Counter Mode (GCM) is one such algorithm. Plaintext The sequence of octets to be encrypted -- a.k.a., the message. The plaintext can contain an arbitrary sequence of octets. Ciphertext An encrypted representation of the Plaintext. Additional Authenticated Data (AAD) An input to an AEAD operation that is integrity protected but not encrypted. Authentication Tag 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. Content Encryption Key (CEK) A symmetric key for the AEAD algorithm used to encrypt the Plaintext for the recipient to produce the Ciphertext and the Authentication Tag. JSON Text Object A UTF-8 [RFC3629] encoded text string representing a JSON object; the syntax of JSON objects is defined in Section 2.2 of [RFC4627]. JWE Header A JSON Text Object (or JSON Text Objects, when using the JWE JSON Serialization) that describes the encryption operations applied to create the JWE Encrypted Key, the JWE Ciphertext, and the JWE Authentication Tag. The members of the JWE Header object(s) are Header Parameters. JWE Encrypted Key The result of encrypting the Content Encryption Key (CEK) with the intended recipient's key using the specified algorithm. Note that for some algorithms, the JWE Encrypted Key value is specified as being the empty octet sequence. JWE Initialization Vector A sequence of octets containing the Initialization Vector 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. JWE Ciphertext A sequence of octets containing the Ciphertext for a JWE. JWE Authentication Tag A sequence of octets containing the Authentication Tag for a JWE. Jones, et al. Expires March 19, 2014 [Page 6] Internet-Draft JWE September 2013 JWE Protected Header A JSON Text Object that contains the portion of the JWE Header that is integrity protected. For the JWE Compact Serialization, this comprises the entire JWE Header. For the JWE JSON Serialization, this is one component of the JWE Header. Header Parameter A name/value pair that is member of the JWE Header. Header Parameter Name The name of a member of the JWE Header. Header Parameter Value The value of a member of the JWE Header. Base64url Encoding Base64 encoding using the URL- and filename-safe character set defined in Section 5 of RFC 4648 [RFC4648], with all trailing '=' characters omitted (as permitted by Section 3.2). (See Appendix C of [JWS] for notes on implementing base64url encoding without padding.) Encoded JWE Header Base64url encoding of the JWE Protected Header. Encoded JWE Encrypted Key Base64url encoding of the JWE Encrypted Key. Encoded JWE Initialization Vector Base64url encoding of the JWE Initialization Vector. Encoded JWE Ciphertext Base64url encoding of the JWE Ciphertext. Encoded JWE Authentication Tag Base64url encoding of the JWE Authentication Tag. JWE Compact Serialization A representation of the JWE as 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. This representation is compact and URL-safe. JWE JSON Serialization A representation of the JWE as a JSON structure containing JWE Header, Encoded JWE Encrypted Key, Encoded JWE Initialization Vector, Encoded JWE Ciphertext, and Encoded JWE Authentication Tag values. Unlike the JWE Compact Serialization, the JWE JSON Serialization enables the same content to be encrypted to multiple parties. This representation is neither compact nor URL-safe. Jones, et al. Expires March 19, 2014 [Page 7] Internet-Draft JWE September 2013 Collision Resistant Name A name in a namespace that enables names to be allocated in a manner such that they are highly unlikely to collide with other names. Examples of collision resistant namespaces include: Domain Names, Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670 Recommendation series, and Universally Unique IDentifiers (UUIDs) [RFC4122]. When using an administratively delegated namespace, the definer of a name needs to take reasonable precautions to ensure they are in control of the portion of the namespace they use to define the name. StringOrURI A JSON string value, with the additional requirement that while arbitrary string values MAY be used, any value containing a ":" character MUST be a URI [RFC3986]. StringOrURI values are compared as case-sensitive strings with no transformations or canonicalizations applied. Key Management Mode A method of determining the Content Encryption Key (CEK) value to use. Each algorithm used for determining the CEK value uses a specific Key Management Mode. Key Management Modes employed by this specification are Key Encryption, Key Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping, and Direct Encryption. Key Encryption A Key Management Mode in which the Content Encryption Key (CEK) value is encrypted to the intended recipient using an asymmetric encryption algorithm. Key Wrapping A Key Management Mode in which the Content Encryption Key (CEK) value is encrypted to the intended recipient using a symmetric key wrapping algorithm. Direct Key Agreement A Key Management Mode in which a key agreement algorithm is used to agree upon the Content Encryption Key (CEK) value. Key Agreement with Key Wrapping A Key Management Mode in which a key agreement algorithm is used to agree upon a symmetric key used to encrypt the Content Encryption Key (CEK) value to the intended recipient using a symmetric key wrapping algorithm. Direct Encryption A Key Management Mode in which the Content Encryption Key (CEK) value used is the secret symmetric key value shared between the parties. Jones, et al. Expires March 19, 2014 [Page 8] Internet-Draft JWE September 2013 3. JSON Web Encryption (JWE) Overview 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. 3.1. Example JWE 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: o the Content Encryption Key is encrypted to the recipient using the RSAES OAEP algorithm to produce the JWE Encrypted Key and o the Plaintext is encrypted using the AES GCM algorithm with a 256 bit key to produce the Ciphertext. {"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: o Generate a random Content Encryption Key (CEK). o Encrypt the CEK with the recipient's public key using the RSAES OAEP algorithm to produce the JWE Encrypted Key. o Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key. Jones, et al. Expires March 19, 2014 [Page 9] Internet-Draft JWE September 2013 o Generate a random JWE Initialization Vector. o Base64url encode the JWE Initialization Vector to produce the Encoded JWE Initialization Vector. o Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value. o Encrypt the Plaintext with AES GCM using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value, requesting a 128 bit Authentication Tag output. o Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. o Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. o 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 See Appendix A.1 for the complete details of computing this JWE. See Appendix A for additional examples. Jones, et al. Expires March 19, 2014 [Page 10] Internet-Draft JWE September 2013 4. JWE Header 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: Registered Header Parameter Names, Public Header Parameter Names, and Private Header Parameter Names. 4.1. Registered Header Parameter Names The following Header Parameter Names are registered in the IANA JSON Web Signature and Encryption Header Parameters registry defined in [JWS], 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. 4.1.1. "alg" (Algorithm) Header Parameter The "alg" (algorithm) header parameter identifies the cryptographic algorithm used to encrypt or determine the value of the Content Encryption Key (CEK). The encrypted content is not usable if the "alg" value does not represent a supported algorithm, or if the recipient does not have a key that can be used with that algorithm. "alg" values SHOULD either be registered in the IANA JSON Web Signature and Encryption Algorithms registry defined in [JWA] or be a value that contains a Collision Resistant Name. 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 and processed by implementations. Jones, et al. Expires March 19, 2014 [Page 11] Internet-Draft JWE September 2013 A list of defined "alg" values can be found in the IANA JSON Web Signature and Encryption Algorithms registry defined in [JWA]; the initial contents of this registry are the values defined in Section 4.1 of the JSON Web Algorithms (JWA) [JWA] specification. 4.1.2. "enc" (Encryption Method) Header Parameter 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 defined in [JWA] or be a value that contains a Collision Resistant Name. 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 and processed by implementations. A list of defined "enc" values can be found in the IANA JSON Web Signature and Encryption Algorithms registry defined in [JWA]; the initial contents of this registry are the values defined in Section 4.2 of the JSON Web Algorithms (JWA) [JWA] specification. 4.1.3. "zip" (Compression Algorithm) Header Parameter The "zip" (compression algorithm) applied to the Plaintext before encryption, if any. The "zip" value defined by this specification is: o "DEF" - Compression with the DEFLATE [RFC1951] algorithm Other values MAY be used. Compression algorithm values can be registered in the IANA JSON Web Encryption Compression Algorithm registry defined in [JWA]. The "zip" value is a case sensitive string. If no "zip" parameter is present, no compression is applied to the Plaintext before encryption. This header parameter MUST be integrity protected, and therefore MUST occur only within the JWE Protected Header, when used. Use of this header parameter is OPTIONAL. This header parameter MUST be understood and processed by implementations. 4.1.4. "jku" (JWK Set URL) Header Parameter 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 Jones, et al. Expires March 19, 2014 [Page 12] Internet-Draft JWE September 2013 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. 4.1.5. "jwk" (JSON Web Key) Header Parameter 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. 4.1.6. "x5u" (X.509 URL) Header Parameter 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. 4.1.7. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter The "x5t" (X.509 Certificate SHA-1 Thumbprint) header parameter is a base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER encoding of the X.509 certificate [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 defined in [JWS]. Jones, et al. Expires March 19, 2014 [Page 13] Internet-Draft JWE September 2013 4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter 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. 4.1.9. "kid" (Key ID) Header Parameter 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. 4.1.10. "typ" (Type) Header Parameter The "typ" (type) header parameter is 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" can be used by applications to indicate that this object is a JWS or JWE using the JWS Compact Serialization or the JWE Compact Serialization. The type value "JOSE+JSON" can be used by applications to indicate that this object is a JWS or JWE using the JWS JSON Serialization or the JWE JSON Serialization. Other type values can also be used by applications. The "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. When MIME Media Type values are used, it is RECOMMENDED that they be spelled using the exact character case used in the MIME Media Types Jones, et al. Expires March 19, 2014 [Page 14] Internet-Draft JWE September 2013 registry [IANA.MediaTypes], since this field is case sensitive, whereas MIME Media Type values are case insensitive. "typ" values SHOULD either be registered in the IANA JSON Web Signature and Encryption Type Values registry defined in [JWS] or be a value that contains a Collision Resistant Name. 4.1.11. "cty" (Content Type) Header Parameter The "cty" (content type) header parameter is 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. 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. 4.1.12. "crit" (Critical) Header Parameter 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 and processed by implementations. An example use, along with a hypothetical "exp" (expiration-time) field is: {"alg":"RSA-OAEP", "enc":"A256GCM", "crit":["exp"], "exp":1363284000 } Jones, et al. Expires March 19, 2014 [Page 15] Internet-Draft JWE September 2013 4.2. Public Header Parameter Names Additional Header Parameter Names can be defined by those using JWEs. However, in order to prevent collisions, any new Header Parameter Name SHOULD either be registered in the IANA JSON Web Signature and Encryption Header Parameters registry defined in [JWS] 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. 4.3. Private Header Parameter Names 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 Section 4.1 or Public Header Parameter Names Section 4.2. Unlike Public Header Parameter Names, Private Header Parameter Names are subject to collision and should be used with caution. 5. Producing and Consuming JWEs 5.1. Message Encryption 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. 1. Determine the Key Management Mode employed by the algorithm used to determine the Content Encryption Key (CEK) value. (This is the algorithm recorded in the "alg" (algorithm) header parameter of the resulting JWE.) 2. When Key Wrapping, Key Encryption, or Key Agreement with Key Wrapping are employed, generate a random Content Encryption Key (CEK) value. See RFC 4086 [RFC4086] for considerations on generating random values. The CEK MUST have a length equal to that required for the content encryption algorithm. 3. When Direct Key Agreement or Key Agreement with Key Wrapping are employed, use the key agreement algorithm to compute the value of the agreed upon key. When Direct Key Agreement is employed, let the Content Encryption Key (CEK) be the agreed upon key. When Key Agreement with Key Wrapping is employed, the agreed Jones, et al. Expires March 19, 2014 [Page 16] Internet-Draft JWE September 2013 upon key will be used to wrap the CEK. 4. 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. 5. Otherwise, when Direct Key Agreement or Direct Encryption are employed, let the JWE Encrypted Key be the empty octet sequence. 6. When Direct Encryption is employed, let the Content Encryption Key (CEK) be the shared symmetric key. 7. Base64url encode the JWE Encrypted Key to create the Encoded JWE Encrypted Key. 8. If the JWE JSON Serialization is being used, repeat this process for each recipient. 9. 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. 10. Base64url encode the JWE Initialization Vector to create the Encoded JWE Initialization Vector. 11. Compress the Plaintext if a "zip" parameter was included. 12. Serialize the (compressed) Plaintext into an octet sequence M. 13. Create a JWE Header containing the encryption parameters used. Note that white space is explicitly allowed in the representation and no canonicalization need be performed before encoding. 14. Base64url encode the octets of the UTF-8 representation of the JWE Protected Header to create the Encoded JWE 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 the Encoded JWE Header be the empty string. 15. Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value. However if a top-level "aad" member is present when using the JWE JSON Serialization, instead let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the concatenation of the Encoded JWE Header value, a period ('.') character, and the "aad" field Jones, et al. Expires March 19, 2014 [Page 17] Internet-Draft JWE September 2013 value. 16. 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). 17. Base64url encode the JWE Ciphertext to create the Encoded JWE Ciphertext. 18. Base64url encode the JWE Authentication Tag to create the Encoded JWE Authentication Tag. 19. The five encoded parts are result values used in both the JWE Compact Serialization and the JWE JSON Serialization representations. 20. Create the desired serialized output. The JWE 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 JWE JSON Serialization is described in Section 7.2. 5.2. Message Decryption The message decryption process is the reverse of the encryption process. The order of the steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. If any of these steps fails, the encrypted content cannot be validated. It is an application decision which recipients' encrypted content must successfully validate for the JWE to be accepted. In some cases, encrypted content for all recipients must successfully validate or the JWE will be rejected. In other cases, only the encrypted content for a single recipient needs to be successfully validated. However, in all cases, the encrypted content for at least one recipient MUST successfully validate or the JWE MUST be rejected. 1. Parse the serialized input to determine the values of the JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag. When using the JWE Compact Serialization, the Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Jones, et al. Expires March 19, 2014 [Page 18] Internet-Draft JWE September 2013 Ciphertext, and the Encoded JWE Authentication Tag are represented as text strings in that order, separated by four period ('.') characters. The JWE JSON Serialization is described in Section 7.2. 2. The Encoded JWE Header, the Encoded JWE Encrypted Key, the Encoded JWE Initialization Vector, the Encoded JWE Ciphertext, and the Encoded JWE Authentication Tag MUST be successfully base64url decoded following the restriction that no padding characters have been used. 3. The resulting JWE Protected Header MUST be a completely valid JSON object conforming to RFC 4627 [RFC4627]. 4. If using the JWE Compact Serialization, let the JWE Header be the JWE Protected Header; otherwise, when using the JWE JSON Serialization, let the JWE Header be the union of the members of the JWE Protected Header, the members of the "unprotected" value, and the members of the corresponding "header" value, all of which must be completely valid JSON objects. 5. The resulting JWE Header MUST NOT contain duplicate Header Parameter Names. When using the JWE JSON Serialization, this restriction includes that the same Header Parameter Name also MUST NOT occur in distinct JSON Text Object values that together comprise the JWE Header. 6. The resulting JWE Header MUST be validated to only include parameters and values whose syntax and semantics are both understood and supported or that are specified as being ignored when not understood. 7. Determine the Key Management Mode employed by the algorithm specified by the "alg" (algorithm) header parameter. 8. Verify that the JWE uses a key known to the recipient. 9. When Direct Key Agreement or Key Agreement with Key Wrapping are employed, use the key agreement algorithm to compute the value of the agreed upon key. When Direct Key Agreement is employed, let the Content Encryption Key (CEK) be the agreed upon key. When Key Agreement with Key Wrapping is employed, the agreed upon key will be used to decrypt the JWE Encrypted Key. 10. When Key Wrapping, Key Encryption, or Key Agreement with Key Wrapping are employed, decrypt the JWE Encrypted Key to produce the Content Encryption Key (CEK). The CEK MUST have a length equal to that required for the content encryption algorithm. Jones, et al. Expires March 19, 2014 [Page 19] Internet-Draft JWE September 2013 Note that when there are multiple recipients, each recipient will only be able decrypt any JWE Encrypted Key values that were encrypted to a key in that recipient's possession. It is therefore normal to only be able to decrypt one of the per- recipient JWE Encrypted Key values to obtain the CEK value. To mitigate the attacks described in RFC 3218 [RFC3218], the recipient MUST NOT distinguish between format, padding, and length errors of encrypted keys. It is strongly recommended, in the event of receiving an improperly formatted key, that the receiver substitute a randomly generated CEK and proceed to the next step, to mitigate timing attacks. 11. Otherwise, when Direct Key Agreement or Direct Encryption are employed, verify that the JWE Encrypted Key value is empty octet sequence. 12. When Direct Encryption is employed, let the Content Encryption Key (CEK) be the shared symmetric key. 13. If the JWE JSON Serialization is being used, repeat this process for each recipient contained in the representation until the CEK value has been determined. 14. Let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the Encoded JWE Header value. However if a top-level "aad" member is present when using the JWE JSON Serialization, instead let the Additional Authenticated Data encryption parameter be the octets of the ASCII representation of the concatenation of the Encoded JWE Header value, a period ('.') character, and the "aad" field value. 15. 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 verifying 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. 16. Uncompress the decrypted plaintext if a "zip" parameter was included. 17. Output the resulting Plaintext. Jones, et al. Expires March 19, 2014 [Page 20] Internet-Draft JWE September 2013 5.3. String Comparison Rules 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]. 6. Key Identification 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. These header parameters MUST be integrity protected if the information that they convey is to be utilized in a trust decision. 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. Validation of the encrypted content fails when the key used cannot be determined. The means of exchanging any shared symmetric keys used is outside the scope of this specification. 7. Serializations 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. 7.1. JWE Compact Serialization 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 Jones, et al. Expires March 19, 2014 [Page 21] Internet-Draft JWE September 2013 separated by four period ('.') characters. Only one recipient is supported by the JWE Compact Serialization. 7.2. JWE JSON 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: o Values in the JWE JSON Serialization are represented as members of a JSON object, rather than as base64url encoded strings separated by period ('.') characters. (However binary values and values that are integrity protected are still base64url encoded.) o The Encoded JWE Header value, if non-empty, is stored in the "protected" member. o The Encoded JWE Initialization Vector value, if non-empty, is stored in the "iv" member. o The Encoded JWE Ciphertext value is stored in the "ciphertext" member. o The Encoded JWE Authentication Tag value, if non-empty, is stored in the "tag" member. o The JWE can be encrypted to multiple recipients, rather than just one. A JSON array in the "recipients" member is used to hold values that are specific to a particular recipient, with one array element per recipient represented. These array elements are JSON objects. o Each Encoded JWE Encrypted Key value, if non-empty, is stored in the "encrypted_key" member of a JSON object that is an element of the "recipients" array. o Some header parameter values, such as the "alg" value and parameters used for selecting keys, can also differ for different recipient computations. Per-recipient header parameter values, if present, are stored in the "header" members of the same JSON objects that are elements of the "recipients" array. o Some header parameters, including the "alg" parameter, can be shared among all recipient computations. These header parameters Jones, et al. Expires March 19, 2014 [Page 22] Internet-Draft JWE September 2013 are stored in either of two top-level member(s) of the JSON object: the "protected" member and the "unprotected" member. The values of these members, if present, are JSON Text Objects containing Header Parameters. o Not all header parameters are integrity protected. The shared header parameters in the "protected" member are integrity protected, and are base64url encoded. The per-recipient header parameters in the "header" array element members and the shared header parameters in the "unprotected" member are not integrity protected. These JSON Text Objects containing header parameters that are not integrity protected are not base64url encoded. o 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 per-recipient values in the "header" member of the recipient's array element, (2) the shared integrity-protected values in the "protected" member, and (3) the shared non- integrity-protected values in the "unprotected" member. The union of these sets of header parameters comprises the JWE Header. The header parameter names in the three locations MUST be disjoint. o An "aad" (Additional Authenticated Data) member can be included to supply a base64url encoded value to be integrity protected but not encrypted. (Note that this can also be achieved when using either serialization by including the AAD value as a protected header parameter value, but at the cost of the value being double base64url encoded.) o The "recipients" array MUST always be present, even if the array elements contain only the empty JSON object "{}" (which can happen when all header parameter values are shared between all recipients and when no encrypted key is used, such as when doing Direct Encryption). Jones, et al. Expires March 19, 2014 [Page 23] Internet-Draft JWE September 2013 The syntax of a JWE using the JWE JSON Serialization is as follows: {"protected":", "unprotected":", "recipients":[ {"header":"", "encrypted_key":""}, ... {"header":"", "encrypted_key":""}], "aad":"", "iv":"", "ciphertext":"", "tag":"" } 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 Jones, et al. Expires March 19, 2014 [Page 24] Internet-Draft JWE September 2013 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. 8. Distinguishing Between JWS and JWE Objects 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. o 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. o If the object is using the JWS JSON Serialization or the JWE JSON Serialization, the members used will be different. JWSs have a "signatures" member and JWEs do not. JWEs have a "recipients" member and JWSs do not. o A JWS Header can be distinguished from a JWE header by examining the "alg" (algorithm) header parameter value. If the value represents a digital signature or MAC algorithm, or is the value "none", it is for a JWS; if it represents a Key Encryption, Key Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping, or Direct Encryption algorithm, it is for a JWE. o A JWS Header can also be distinguished from a JWE header by determining whether an "enc" (encryption method) member exists. If the "enc" member exists, it is a JWE; otherwise, it is a JWS. 9. IANA Considerations 9.1. JWE Header Parameter Names Registration This specification registers the Header Parameter Names defined in Section 4.1 in the IANA JSON Web Signature and Encryption Header Parameters registry defined in [JWS]. Jones, et al. Expires March 19, 2014 [Page 25] Internet-Draft JWE September 2013 9.1.1. Registry Contents o Header Parameter Name: "alg" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.1 of [[ this document ]] o Header Parameter Name: "enc" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.2 of [[ this document ]] o Header Parameter Name: "zip" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.3 of [[ this document ]] o Header Parameter Name: "jku" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.4 of [[ this document ]] o Header Parameter Name: "jwk" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification document(s): Section 4.1.5 of [[ this document ]] o Header Parameter Name: "x5u" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.6 of [[ this document ]] o Header Parameter Name: "x5t" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.7 of [[ this document ]] o Header Parameter Name: "x5c" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.8 of [[ this document ]] o Header Parameter Name: "kid" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.9 of [[ this document ]] Jones, et al. Expires March 19, 2014 [Page 26] Internet-Draft JWE September 2013 o Header Parameter Name: "typ" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.10 of [[ this document ]] o Header Parameter Name: "cty" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.11 of [[ this document ]] o Header Parameter Name: "crit" o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.12 of [[ this document ]] 10. Security Considerations 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 encrypted content is rejected. 11. References 11.1. Normative References [ECMAScript] Ecma International, "ECMAScript Language Specification, Jones, et al. Expires March 19, 2014 [Page 27] Internet-Draft JWE September 2013 5.1 Edition", ECMA 262, June 2011. [IANA.MediaTypes] Internet Assigned Numbers Authority (IANA), "MIME Media Types", 2005. [ITU.X690.1994] International Telecommunications Union, "Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)", ITU-T Recommendation X.690, 1994. [JWA] Jones, M., "JSON Web Algorithms (JWA)", draft-ietf-jose-json-web-algorithms (work in progress), September 2013. [JWK] Jones, M., "JSON Web Key (JWK)", draft-ietf-jose-json-web-key (work in progress), September 2013. [JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", draft-ietf-jose-json-web-signature (work in progress), September 2013. [RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures", RFC 1421, February 1993. [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification version 1.3", RFC 1951, May 1996. [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. Jones, et al. Expires March 19, 2014 [Page 28] Internet-Draft JWE September 2013 [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. [RFC4627] Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, July 2006. [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, October 2006. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008. [W3C.CR-xmlenc-core1-20120313] Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch, "XML Encryption Syntax and Processing Version 1.1", World Wide Web Consortium CR CR-xmlenc-core1-20120313, March 2012, . 11.2. Informative References [I-D.mcgrew-aead-aes-cbc-hmac-sha2] McGrew, D. and K. Paterson, "Authenticated Encryption with AES-CBC and HMAC-SHA", draft-mcgrew-aead-aes-cbc-hmac-sha2-01 (work in progress), October 2012. [I-D.rescorla-jsms] Rescorla, E. and J. Hildebrand, "JavaScript Message Security Format", draft-rescorla-jsms-00 (work in progress), March 2011. [JSE] Bradley, J. and N. Sakimura (editor), "JSON Simple Encryption", September 2010. [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, Jones, et al. Expires March 19, 2014 [Page 29] Internet-Draft JWE September 2013 RFC 5652, September 2009. Appendix A. JWE Examples This section provides examples of JWE computations. A.1. Example JWE using RSAES OAEP and AES GCM 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] A.1.1. JWE Header The following example JWE Header declares that: o the Content Encryption Key is encrypted to the recipient using the RSAES OAEP algorithm to produce the JWE Encrypted Key and o the Plaintext is encrypted using the AES GCM algorithm with a 256 bit key to produce the Ciphertext. {"alg":"RSA-OAEP","enc":"A256GCM"} A.1.2. Encoded JWE Header Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value: eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ A.1.3. Content Encryption Key (CEK) 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] Jones, et al. Expires March 19, 2014 [Page 30] Internet-Draft JWE September 2013 A.1.4. Key Encryption 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] A.1.5. Encoded JWE Encrypted Key Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key. This result (with line breaks for display purposes Jones, et al. Expires March 19, 2014 [Page 31] Internet-Draft JWE September 2013 only) is: OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8 1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi 6UklfCpIMfIjf7iGdXKHzg A.1.6. Initialization Vector 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 A.1.7. Additional Authenticated Data 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] A.1.8. Content Encryption 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] Jones, et al. Expires March 19, 2014 [Page 32] Internet-Draft JWE September 2013 A.1.9. Encoded JWE Ciphertext 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 A.1.10. Encoded JWE Authentication Tag Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is: XFBoMYUZodetZdvTiFvSkQ A.1.11. Complete Representation 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 A.1.12. Validation 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 Jones, et al. Expires March 19, 2014 [Page 33] Internet-Draft JWE September 2013 for all encryptions performed using these inputs. A.2. Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256 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] A.2.1. JWE Header The following example JWE Header (with line breaks for display purposes only) declares that: o the Content Encryption Key is encrypted to the recipient using the RSAES-PKCS1-V1_5 algorithm to produce the JWE Encrypted Key and o the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the Ciphertext. {"alg":"RSA1_5","enc":"A128CBC-HS256"} A.2.2. Encoded JWE Header Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value: eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0 A.2.3. Content Encryption Key (CEK) 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] A.2.4. Key Encryption 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): Jones, et al. Expires March 19, 2014 [Page 34] Internet-Draft JWE September 2013 {"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] A.2.5. Encoded JWE Encrypted Key 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 Jones, et al. Expires March 19, 2014 [Page 35] Internet-Draft JWE September 2013 -B3oWh2TbqmScqXMR4gp_A A.2.6. Initialization Vector 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 A.2.7. Additional Authenticated Data 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] A.2.8. Content Encryption 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] A.2.9. Encoded JWE Ciphertext Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result is: Jones, et al. Expires March 19, 2014 [Page 36] Internet-Draft JWE September 2013 KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY A.2.10. Encoded JWE Authentication Tag Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is: 9hH0vgRfYgPnAHOd8stkvw A.2.11. Complete Representation 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 A.2.12. Validation 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. A.3. Example JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256 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: Jones, et al. Expires March 19, 2014 [Page 37] Internet-Draft JWE September 2013 [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114, 111, 115, 112, 101, 114, 46] A.3.1. JWE Header The following example JWE Header declares that: o the Content Encryption Key is encrypted to the recipient using the AES Key Wrap algorithm with a 128 bit key to produce the JWE Encrypted Key and o the Plaintext is encrypted using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the Ciphertext. {"alg":"A128KW","enc":"A128CBC-HS256"} A.3.2. Encoded JWE Header Base64url encoding the octets of the UTF-8 representation of the JWE Header yields this Encoded JWE Header value: eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0 A.3.3. Content Encryption Key (CEK) 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] A.3.4. Key Encryption 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] Jones, et al. Expires March 19, 2014 [Page 38] Internet-Draft JWE September 2013 A.3.5. Encoded JWE Encrypted Key Base64url encode the JWE Encrypted Key to produce the Encoded JWE Encrypted Key. This result is: 6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ A.3.6. Initialization Vector 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 A.3.7. Additional Authenticated Data 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] A.3.8. Content Encryption 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] Jones, et al. Expires March 19, 2014 [Page 39] Internet-Draft JWE September 2013 A.3.9. Encoded JWE Ciphertext Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result is: KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY A.3.10. Encoded JWE Authentication Tag Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is: U0m_YmjN04DJvceFICbCVQ A.3.11. Complete Representation 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 A.3.12. Validation 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. A.4. Example JWE Using JWE JSON Serialization This section contains an example using the JWE JSON Serialization. This example demonstrates the capability for encrypting the same plaintext to multiple recipients. Jones, et al. Expires March 19, 2014 [Page 40] Internet-Draft JWE September 2013 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). A.4.1. JWE Per-Recipient Unprotected Headers The first recipient uses the RSAES-PKCS1-V1_5 algorithm to encrypt the Content Encryption Key (CEK). The second uses AES Key Wrap to encrypt the CEK. Key ID values are supplied for both keys. The two per-recipient header values used to represent these algorithms and Key IDs are: {"alg":"RSA1_5","kid":"2011-04-29"} and {"alg":"A128KW","kid":"7"} A.4.2. JWE Protected Header 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 A.4.3. JWE Unprotected Header 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"} Jones, et al. Expires March 19, 2014 [Page 41] Internet-Draft JWE September 2013 A.4.4. Complete JWE Header Values 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"} A.4.5. Additional Authenticated Data 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] A.4.6. Content Encryption 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] A.4.7. Encoded JWE Ciphertext Base64url encode the Ciphertext to create the Encoded JWE Ciphertext. This result is: Jones, et al. Expires March 19, 2014 [Page 42] Internet-Draft JWE September 2013 KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY A.4.8. Encoded JWE Authentication Tag Base64url encode the Authentication Tag to create the Encoded JWE Authentication Tag. This result is: Mz-VPPyU4RlcuYv1IwIvzw A.4.9. Complete JWE JSON Serialization Representation 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" } Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation 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 Jones, et al. Expires March 19, 2014 [Page 43] Internet-Draft JWE September 2013 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. B.1. Extract MAC_KEY and ENC_KEY from Key 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". B.2. Encrypt Plaintext to Create Ciphertext 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] B.3. 64 Bit Big Endian Representation of AAD Length 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, Jones, et al. Expires March 19, 2014 [Page 44] Internet-Draft JWE September 2013 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] B.4. Initialization Vector Value 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] B.5. Create Input to HMAC Computation 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] B.6. Compute HMAC Value 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] B.7. Truncate HMAC Value to Create Authentication Tag 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] Jones, et al. Expires March 19, 2014 [Page 45] Internet-Draft JWE September 2013 Appendix C. Acknowledgements 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. Appendix D. Document History [[ to be removed by the RFC Editor before publication as an RFC ]] -16 o Changes to address editorial and minor issues #163, #168, #169, #170, #172, and #173. -15 o Clarified that it is an application decision which recipients' encrypted content must successfully validate for the JWE to be accepted, addressing issue #35. Jones, et al. Expires March 19, 2014 [Page 46] Internet-Draft JWE September 2013 o Changes to address editorial issues #34, #164, and #169. -14 o Clarified that the "protected", "unprotected", "header", "iv", "tag", and "encrypted_key" parameters are to be omitted in the JWE JSON Serialization when their values would be empty. Stated that the "recipients" array must always be present. -13 o Added an "aad" (Additional Authenticated Data) member for the JWE JSON Serialization, enabling Additional Authenticated Data to be supplied that is not double base64url encoded, addressing issue #29. -12 o Clarified that the "typ" and "cty" header parameters are used in an application-specific manner and have no effect upon the JWE processing. o Replaced the MIME types "application/jwe+json" and "application/jwe" with "application/jose+json" and "application/jose". o Stated that recipients MUST either reject JWEs with duplicate Header Parameter Names or use a JSON parser that returns only the lexically last duplicate member name. o Moved the "epk", "apu", and "apv" Header Parameter definitions to be with the algorithm descriptions that use them. o Added a Serializations section with parallel treatment of the JWE Compact Serialization and the JWE JSON Serialization and also moved the former Implementation Considerations content there. o Restored use of the term "AEAD". o Changed terminology from "block encryption" to "content encryption". -11 o Added Key Identification section. o Removed the Encrypted Key value from the AAD computation since it is already effectively integrity protected by the encryption Jones, et al. Expires March 19, 2014 [Page 47] Internet-Draft JWE September 2013 process. The AAD value now only contains the representation of the JWE Encrypted Header. o For the JWE JSON Serialization, enable header parameter values to be specified in any of three parameters: the "protected" member that is integrity protected and shared among all recipients, the "unprotected" member that is not integrity protected and shared among all recipients, and the "header" member that is not integrity protected and specific to a particular recipient. (This does not affect the JWE Compact Serialization, in which all header parameter values are in a single integrity protected JWE Header value.) o Shortened the names "authentication_tag" to "tag" and "initialization_vector" to "iv" in the JWE JSON Serialization, addressing issue #20. o Removed "apv" (agreement PartyVInfo) since it is no longer used. o Removed suggested compact serialization for multiple recipients. o Changed the MIME type name "application/jwe-js" to "application/jwe+json", addressing issue #22. o Tightened the description of the "crit" (critical) header parameter. -10 o Changed the JWE processing rules for multiple recipients so that a single AAD value contains the header parameters and encrypted key values for all the recipients, enabling AES GCM to be safely used for multiple recipients. o Added an appendix suggesting a possible compact serialization for JWEs with multiple recipients. -09 o Added JWE JSON Serialization, as specified by draft-jones-jose-jwe-json-serialization-04. o Registered "application/jwe-js" MIME type and "JWE-JS" typ header parameter value. o Defined that the default action for header parameters that are not understood is to ignore them unless specifically designated as "MUST be understood" or included in the new "crit" (critical) Jones, et al. Expires March 19, 2014 [Page 48] Internet-Draft JWE September 2013 header parameter list. This addressed issue #6. o Corrected "x5c" description. This addressed issue #12. o Changed from using the term "byte" to "octet" when referring to 8 bit values. o Added Key Management Mode definitions to terminology section and used the defined terms to provide clearer key management instructions. This addressed issue #5. o Added text about preventing the recipient from behaving as an oracle during decryption, especially when using RSAES-PKCS1-V1_5. o Changed from using the term "Integrity Value" to "Authentication Tag". o Changed member name from "integrity_value" to "authentication_tag" in the JWE JSON Serialization. o Removed Initialization Vector from the AAD value since it is already integrity protected by all of the authenticated encryption algorithms specified in the JWA specification. o Replaced "A128CBC+HS256" and "A256CBC+HS512" with "A128CBC-HS256" and "A256CBC-HS512". The new algorithms perform the same cryptographic computations as [I-D.mcgrew-aead-aes-cbc-hmac-sha2], but with the Initialization Vector and Authentication Tag values remaining separate from the Ciphertext value in the output representation. Also deleted the header parameters "epu" (encryption PartyUInfo) and "epv" (encryption PartyVInfo), since they are no longer used. -08 o Replaced uses of the term "AEAD" with "Authenticated Encryption", since the term AEAD in the RFC 5116 sense implied the use of a particular data representation, rather than just referring to the class of algorithms that perform authenticated encryption with associated data. o Applied editorial improvements suggested by Jeff Hodges and Hannes Tschofenig. Many of these simplified the terminology used. o Clarified statements of the form "This header parameter is OPTIONAL" to "Use of this header parameter is OPTIONAL". Jones, et al. Expires March 19, 2014 [Page 49] Internet-Draft JWE September 2013 o Added a Header Parameter Usage Location(s) field to the IANA JSON Web Signature and Encryption Header Parameters registry. o Added seriesInfo information to Internet Draft references. -07 o Added a data length prefix to PartyUInfo and PartyVInfo values. o Updated values for example AES CBC calculations. o Made several local editorial changes to clean up loose ends left over from to the decision to only support block encryption methods providing integrity. One of these changes was to explicitly state that the "enc" (encryption method) algorithm must be an Authenticated Encryption algorithm with a specified key length. -06 o Removed the "int" and "kdf" parameters and defined the new composite Authenticated Encryption algorithms "A128CBC+HS256" and "A256CBC+HS512" to replace the former uses of AES CBC, which required the use of separate integrity and key derivation functions. o Included additional values in the Concat KDF calculation -- the desired output size and the algorithm value, and optionally PartyUInfo and PartyVInfo values. Added the optional header parameters "apu" (agreement PartyUInfo), "apv" (agreement PartyVInfo), "epu" (encryption PartyUInfo), and "epv" (encryption PartyVInfo). Updated the KDF examples accordingly. o Promoted Initialization Vector from being a header parameter to being a top-level JWE element. This saves approximately 16 bytes in the compact serialization, which is a significant savings for some use cases. Promoting the Initialization Vector out of the header also avoids repeating this shared value in the JSON serialization. o Changed "x5c" (X.509 Certificate Chain) representation from being a single string to being an array of strings, each containing a single base64 encoded DER certificate value, representing elements of the certificate chain. o Added an AES Key Wrap example. o Reordered the encryption steps so CMK creation is first, when required. Jones, et al. Expires March 19, 2014 [Page 50] Internet-Draft JWE September 2013 o Correct statements in examples about which algorithms produce reproducible results. -05 o Support both direct encryption using a shared or agreed upon symmetric key, and the use of a shared or agreed upon symmetric key to key wrap the CMK. o Added statement that "StringOrURI values are compared as case- sensitive strings with no transformations or canonicalizations applied". o Updated open issues. o Indented artwork elements to better distinguish them from the body text. -04 o Refer to the registries as the primary sources of defined values and then secondarily reference the sections defining the initial contents of the registries. o Normatively reference XML Encryption 1.1 [W3C.CR-xmlenc-core1-20120313] for its security considerations. o Reference draft-jones-jose-jwe-json-serialization instead of draft-jones-json-web-encryption-json-serialization. o Described additional open issues. o Applied editorial suggestions. -03 o Added the "kdf" (key derivation function) header parameter to provide crypto agility for key derivation. The default KDF remains the Concat KDF with the SHA-256 digest function. o Reordered encryption steps so that the Encoded JWE Header is always created before it is needed as an input to the Authenticated Encryption "additional authenticated data" parameter. o Added the "cty" (content type) header parameter for declaring type information about the secured content, as opposed to the "typ" (type) header parameter, which declares type information about Jones, et al. Expires March 19, 2014 [Page 51] Internet-Draft JWE September 2013 this object. o Moved description of how to determine whether a header is for a JWS or a JWE from the JWT spec to the JWE spec. o Added complete encryption examples for both Authenticated Encryption and non-Authenticated Encryption algorithms. o Added complete key derivation examples. o Added "Collision Resistant Namespace" to the terminology section. o Reference ITU.X690.1994 for DER encoding. o Added Registry Contents sections to populate registry values. o Numerous editorial improvements. -02 o When using Authenticated Encryption algorithms (such as AES GCM), use the "additional authenticated data" parameter to provide integrity for the header, encrypted key, and ciphertext and use the resulting "authentication tag" value as the JWE Authentication Tag. o Defined KDF output key sizes. o Generalized text to allow key agreement to be employed as an alternative to key wrapping or key encryption. o Changed compression algorithm from gzip to DEFLATE. o Clarified that it is an error when a "kid" value is included and no matching key is found. o Clarified that JWEs with duplicate Header Parameter Names MUST be rejected. o Clarified the relationship between "typ" header parameter values and MIME types. o Registered application/jwe MIME type and "JWE" typ header parameter value. o Simplified JWK terminology to get replace the "JWK Key Object" and "JWK Container Object" terms with simply "JSON Web Key (JWK)" and "JSON Web Key Set (JWK Set)" and to eliminate potential confusion Jones, et al. Expires March 19, 2014 [Page 52] Internet-Draft JWE September 2013 between single keys and sets of keys. As part of this change, the Header Parameter Name for a public key value was changed from "jpk" (JSON Public Key) to "jwk" (JSON Web Key). o Added suggestion on defining additional header parameters such as "x5t#S256" in the future for certificate thumbprints using hash algorithms other than SHA-1. o Specify RFC 2818 server identity validation, rather than RFC 6125 (paralleling the same decision in the OAuth specs). o Generalized language to refer to Message Authentication Codes (MACs) rather than Hash-based Message Authentication Codes (HMACs) unless in a context specific to HMAC algorithms. o Reformatted to give each header parameter its own section heading. -01 o Added an integrity check for non-Authenticated Encryption algorithms. o Added "jpk" and "x5c" header parameters for including JWK public keys and X.509 certificate chains directly in the header. o Clarified that this specification is defining the JWE Compact Serialization. Referenced the new JWE-JS spec, which defines the JWE JSON Serialization. o Added text "New header parameters should be introduced sparingly since an implementation that does not understand a parameter MUST reject the JWE". o Clarified that the order of the encryption and decryption steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. o Made other editorial improvements suggested by JOSE working group participants. -00 o Created the initial IETF draft based upon draft-jones-json-web-encryption-02 with no normative changes. o Changed terminology to no longer call both digital signatures and HMACs "signatures". Jones, et al. Expires March 19, 2014 [Page 53] Internet-Draft JWE September 2013 Authors' Addresses Michael B. Jones Microsoft Email: mbj@microsoft.com URI: http://self-issued.info/ Eric Rescorla RTFM, Inc. Email: ekr@rtfm.com Joe Hildebrand Cisco Systems, Inc. Email: jhildebr@cisco.com Jones, et al. 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