JOSE Working Group M. Jones Internet-Draft Microsoft Intended status: Standards Track J. Hildebrand Expires: July 17, 2015 Cisco January 13, 2015 JSON Web Encryption (JWE) draft-ietf-jose-json-web-encryption-40 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 July 17, 2015. Copyright Notice Copyright (c) 2015 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Jones & Hildebrand Expires July 17, 2015 [Page 1]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. JSON Web Encryption (JWE) Overview . . . . . . . . . . . . . . 8 3.1. JWE Compact Serialization Overview . . . . . . . . . . . . 9 3.2. JWE JSON Serialization Overview . . . . . . . . . . . . . 9 3.3. Example JWE . . . . . . . . . . . . . . . . . . . . . . . 10 4. JOSE Header . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Registered Header Parameter Names . . . . . . . . . . . . 12 4.1.1. "alg" (Algorithm) Header Parameter . . . . . . . . . . 12 4.1.2. "enc" (Encryption Algorithm) Header Parameter . . . . 12 4.1.3. "zip" (Compression Algorithm) Header Parameter . . . . 13 4.1.4. "jku" (JWK Set URL) Header Parameter . . . . . . . . . 13 4.1.5. "jwk" (JSON Web Key) Header Parameter . . . . . . . . 13 4.1.6. "kid" (Key ID) Header Parameter . . . . . . . . . . . 13 4.1.7. "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 13 4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter . . . 14 4.1.9. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter . . . . . . . . . . . . . . . . . . . . . . 14 4.1.10. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header Parameter . . . . . . . . . . . . . . . . . . . 14 4.1.11. "typ" (Type) Header Parameter . . . . . . . . . . . . 14 4.1.12. "cty" (Content Type) Header Parameter . . . . . . . . 14 4.1.13. "crit" (Critical) Header Parameter . . . . . . . . . . 14 4.2. Public Header Parameter Names . . . . . . . . . . . . . . 15 4.3. Private Header Parameter Names . . . . . . . . . . . . . . 15 5. Producing and Consuming JWEs . . . . . . . . . . . . . . . . . 15 5.1. Message Encryption . . . . . . . . . . . . . . . . . . . . 15 5.2. Message Decryption . . . . . . . . . . . . . . . . . . . . 17 5.3. String Comparison Rules . . . . . . . . . . . . . . . . . 20 6. Key Identification . . . . . . . . . . . . . . . . . . . . . . 20 7. Serializations . . . . . . . . . . . . . . . . . . . . . . . . 20 7.1. JWE Compact Serialization . . . . . . . . . . . . . . . . 20 7.2. JWE JSON Serialization . . . . . . . . . . . . . . . . . . 21 7.2.1. General JWE JSON Serialization Syntax . . . . . . . . 21 7.2.2. Flattened JWE JSON Serialization Syntax . . . . . . . 24 8. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . . 24 9. Distinguishing between JWS and JWE Objects . . . . . . . . . . 25 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 10.1. JSON Web Signature and Encryption Header Parameters Registration . . . . . . . . . . . . . . . . . . . . . . . 25 Jones & Hildebrand Expires July 17, 2015 [Page 2]
Internet-Draft JSON Web Encryption (JWE) January 2015 10.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 25 11. Security Considerations . . . . . . . . . . . . . . . . . . . 27 11.1. Key Entropy and Random Values . . . . . . . . . . . . . . 27 11.2. Key Protection . . . . . . . . . . . . . . . . . . . . . . 28 11.3. Using Matching Algorithm Strengths . . . . . . . . . . . . 28 11.4. Adaptive Chosen-Ciphertext Attacks . . . . . . . . . . . . 28 11.5. Timing Attacks . . . . . . . . . . . . . . . . . . . . . . 29 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29 12.1. Normative References . . . . . . . . . . . . . . . . . . . 29 12.2. Informative References . . . . . . . . . . . . . . . . . . 30 Appendix A. JWE Examples . . . . . . . . . . . . . . . . . . . . 31 A.1. Example JWE using RSAES OAEP and AES GCM . . . . . . . . . 31 A.1.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . 31 A.1.2. Content Encryption Key (CEK) . . . . . . . . . . . . . 31 A.1.3. Key Encryption . . . . . . . . . . . . . . . . . . . . 32 A.1.4. Initialization Vector . . . . . . . . . . . . . . . . 33 A.1.5. Additional Authenticated Data . . . . . . . . . . . . 33 A.1.6. Content Encryption . . . . . . . . . . . . . . . . . . 34 A.1.7. Complete Representation . . . . . . . . . . . . . . . 34 A.1.8. Validation . . . . . . . . . . . . . . . . . . . . . . 35 A.2. Example JWE using RSAES-PKCS1-V1_5 and AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 35 A.2.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . 35 A.2.2. Content Encryption Key (CEK) . . . . . . . . . . . . . 36 A.2.3. Key Encryption . . . . . . . . . . . . . . . . . . . . 36 A.2.4. Initialization Vector . . . . . . . . . . . . . . . . 38 A.2.5. Additional Authenticated Data . . . . . . . . . . . . 38 A.2.6. Content Encryption . . . . . . . . . . . . . . . . . . 38 A.2.7. Complete Representation . . . . . . . . . . . . . . . 39 A.2.8. Validation . . . . . . . . . . . . . . . . . . . . . . 39 A.3. Example JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . . . 40 A.3.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . 40 A.3.2. Content Encryption Key (CEK) . . . . . . . . . . . . . 40 A.3.3. Key Encryption . . . . . . . . . . . . . . . . . . . . 40 A.3.4. Initialization Vector . . . . . . . . . . . . . . . . 41 A.3.5. Additional Authenticated Data . . . . . . . . . . . . 41 A.3.6. Content Encryption . . . . . . . . . . . . . . . . . . 41 A.3.7. Complete Representation . . . . . . . . . . . . . . . 42 A.3.8. Validation . . . . . . . . . . . . . . . . . . . . . . 42 A.4. Example JWE using General JWE JSON Serialization . . . . . 43 A.4.1. JWE Per-Recipient Unprotected Headers . . . . . . . . 43 A.4.2. JWE Protected Header . . . . . . . . . . . . . . . . . 43 A.4.3. JWE Unprotected Header . . . . . . . . . . . . . . . . 44 A.4.4. Complete JOSE Header Values . . . . . . . . . . . . . 44 A.4.5. Additional Authenticated Data . . . . . . . . . . . . 44 A.4.6. Content Encryption . . . . . . . . . . . . . . . . . . 44 A.4.7. Complete JWE JSON Serialization Representation . . . . 45 Jones & Hildebrand Expires July 17, 2015 [Page 3]
Internet-Draft JSON Web Encryption (JWE) January 2015 A.5. Example JWE using Flattened JWE JSON Serialization . . . . 46 Appendix B. Example AES_128_CBC_HMAC_SHA_256 Computation . . . . 46 B.1. Extract MAC_KEY and ENC_KEY from Key . . . . . . . . . . . 46 B.2. Encrypt Plaintext to Create Ciphertext . . . . . . . . . . 47 B.3. 64 Bit Big Endian Representation of AAD Length . . . . . . 47 B.4. Initialization Vector Value . . . . . . . . . . . . . . . 48 B.5. Create Input to HMAC Computation . . . . . . . . . . . . . 48 B.6. Compute HMAC Value . . . . . . . . . . . . . . . . . . . . 48 B.7. Truncate HMAC Value to Create Authentication Tag . . . . . 48 Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 48 Appendix D. Document History . . . . . . . . . . . . . . . . . . 49 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 61 Jones & Hildebrand Expires July 17, 2015 [Page 4]
Internet-Draft JSON Web Encryption (JWE) January 2015 1. Introduction JSON Web Encryption (JWE) represents encrypted content using JavaScript Object Notation (JSON) [RFC7159] based data structures. The JWE cryptographic mechanisms encrypt and provide integrity protection for an arbitrary sequence of octets. Two closely related serializations for JWEs are defined. The JWE Compact Serialization is a compact, URL-safe representation intended for space constrained environments such as HTTP Authorization headers and URI query parameters. The JWE JSON Serialization represents JWEs as JSON objects and enables the same content to be encrypted to multiple parties. Both share the same cryptographic underpinnings. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) [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", "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. BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per Section 2 of [JWS]. UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation of STRING, where STRING is a sequence of zero or more Unicode [UNICODE] characters. ASCII(STRING) denotes the octets of the ASCII [RFC20] representation of STRING, where STRING is a sequence of zero or more ASCII characters. The concatenation of two values A and B is denoted as A || B. Jones & Hildebrand Expires July 17, 2015 [Page 5]
Internet-Draft JSON Web Encryption (JWE) January 2015 2. Terminology These terms defined by the JSON Web Signature (JWS) [JWS] specification are incorporated into this specification: "JSON Web Signature (JWS)", "Base64url Encoding", "Collision-Resistant Name", "Header Parameter", "JOSE Header", and "StringOrURI". These terms defined by the Internet Security Glossary, Version 2 [RFC4949] are incorporated into this specification: "Ciphertext", "Digital Signature", "Message Authentication Code (MAC)", and "Plaintext". These terms are defined by this specification: JSON Web Encryption (JWE) A data structure representing an encrypted and integrity protected message. 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 two outputs, the Ciphertext and the Authentication Tag value. AES Galois/Counter Mode (GCM) is one such algorithm. 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 to produce the Ciphertext and the Authentication Tag. JWE Encrypted Key Encrypted Content Encryption Key (CEK) value. Note that for some algorithms, the JWE Encrypted Key value is specified as being the empty octet sequence. Jones & Hildebrand Expires July 17, 2015 [Page 6]
Internet-Draft JSON Web Encryption (JWE) January 2015 JWE Initialization Vector Initialization vector value used when encrypting the plaintext. Note that some algorithms may not use an Initialization Vector, in which case this value is the empty octet sequence. JWE AAD Additional value to be integrity protected by the authenticated encryption operation. This can only be present when using the JWE JSON Serialization. (Note that this can also be achieved when using either serialization by including the AAD value as an integrity protected Header Parameter value, but at the cost of the value being double base64url encoded.) JWE Ciphertext Ciphertext value resulting from authenticated encryption of the plaintext with additional authenticated data. JWE Authentication Tag Authentication Tag value resulting from authenticated encryption of the plaintext with additional authenticated data. JWE Protected Header JSON object that contains the Header Parameters that are integrity protected by the authenticated encryption operation. These parameters apply to all recipients of the JWE. For the JWE Compact Serialization, this comprises the entire JOSE Header. For the JWE JSON Serialization, this is one component of the JOSE Header. JWE Shared Unprotected Header JSON object that contains the Header Parameters that apply to all recipients of the JWE that are not integrity protected. This can only be present when using the JWE JSON Serialization. JWE Per-Recipient Unprotected Header JSON object that contains Header Parameters that apply to a single recipient of the JWE. These Header Parameter values are not integrity protected. This can only be present when using the JWE JSON Serialization. JWE Compact Serialization A representation of the JWE as a compact, URL-safe string. JWE JSON Serialization A representation of the JWE as a JSON object. The JWE JSON Serialization enables the same content to be encrypted to multiple parties. This representation is neither optimized for compactness nor URL-safe. Jones & Hildebrand Expires July 17, 2015 [Page 7]
Internet-Draft JSON Web Encryption (JWE) January 2015 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. 3. JSON Web Encryption (JWE) Overview JWE represents encrypted content using JSON data structures and base64url encoding. These JSON data structures MAY contain white space and/or line breaks before or after any JSON values or structural characters, in accordance with Section 2 of RFC 7159 [RFC7159]. A JWE represents these logical values (each of which is defined in Section 2): o JOSE Header o JWE Encrypted Key o JWE Initialization Vector o JWE AAD Jones & Hildebrand Expires July 17, 2015 [Page 8]
Internet-Draft JSON Web Encryption (JWE) January 2015 o JWE Ciphertext o JWE Authentication Tag For a JWE, the JOSE Header members are the union of the members of these values (each of which is defined in Section 2): o JWE Protected Header o JWE Shared Unprotected Header o JWE Per-Recipient Unprotected Header JWE utilizes authenticated encryption to ensure the confidentiality and integrity of the Plaintext and the integrity of the JWE Protected Header and the JWE AAD. This document defines two serializations for JWEs: a compact, URL- safe serialization called the JWE Compact Serialization and a JSON serialization called the JWE JSON Serialization. In both serializations, the JWE Protected Header, JWE Encrypted Key, JWE Initialization Vector, JWE Ciphertext, and JWE Authentication Tag are base64url encoded, since JSON lacks a way to directly represent arbitrary octet sequences. When present, the JWE AAD is also base64url encoded. 3.1. JWE Compact Serialization Overview In the JWE Compact Serialization, no JWE Shared Unprotected Header or JWE Per-Recipient Unprotected Header are used. In this case, the JOSE Header and the JWE Protected Header are the same. In the JWE Compact Serialization, a JWE is represented as the concatenation: BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag) See Section 7.1 for more information about the JWE Compact Serialization. 3.2. JWE JSON Serialization Overview In the JWE JSON Serialization, one or more of the JWE Protected Header, JWE Shared Unprotected Header, and JWE Per-Recipient Unprotected Header MUST be present. In this case, the members of the JOSE Header are the union of the members of the JWE Protected Header, JWE Shared Unprotected Header, and JWE Per-Recipient Unprotected Jones & Hildebrand Expires July 17, 2015 [Page 9]
Internet-Draft JSON Web Encryption (JWE) January 2015 Header values that are present. In the JWE JSON Serialization, a JWE is represented as a JSON object containing some or all of these eight members: "protected", with the value BASE64URL(UTF8(JWE Protected Header)) "unprotected", with the value JWE Shared Unprotected Header "header", with the value JWE Per-Recipient Unprotected Header "encrypted_key", with the value BASE64URL(JWE Encrypted Key) "iv", with the value BASE64URL(JWE Initialization Vector) "ciphertext", with the value BASE64URL(JWE Ciphertext) "tag", with the value BASE64URL(JWE Authentication Tag) "aad", with the value BASE64URL(JWE AAD) The six base64url encoded result strings and the two unprotected JSON object values are represented as members within a JSON object. The inclusion of some of these values is OPTIONAL. The JWE JSON Serialization can also encrypt the plaintext to multiple recipients. See Section 7.2 for more information about the JWE JSON Serialization. 3.3. Example JWE This example encrypts the plaintext "The true sign of intelligence is not knowledge but imagination." to the recipient. The following example JWE Protected Header declares that: o The Content Encryption Key is encrypted to the recipient using the RSAES OAEP [RFC3447] algorithm to produce the JWE Encrypted Key. o Authenticated encryption is performed on the Plaintext using the AES GCM [AES, NIST.800-38D] algorithm with a 256 bit key to produce the Ciphertext and the Authentication Tag. {"alg":"RSA-OAEP","enc":"A256GCM"} Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this 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. Jones & Hildebrand Expires July 17, 2015 [Page 10]
Internet-Draft JSON Web Encryption (JWE) January 2015 o Base64url encode the JWE Encrypted Key. o Generate a random JWE Initialization Vector. o Base64url encode the JWE Initialization Vector. o Let the Additional Authenticated Data encryption parameter be ASCII(BASE64URL(UTF8(JWE Protected Header))). o Perform authenticated encryption on the Plaintext with the AES GCM algorithm using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value, requesting a 128 bit Authentication Tag output. o Base64url encode the Ciphertext. o Base64url encode the Authentication Tag. o Assemble the final representation: The Compact Serialization of this result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag). The final result in this example (with line breaks for display purposes only) is: 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, including examples using the JWE JSON Serialization in Sections A.4 and A.5. 4. JOSE Header For a JWE, the members of the JSON object(s) representing the JOSE Header describe the encryption applied to the Plaintext and optionally additional properties of the JWE. The Header Parameter names within the JOSE Header MUST be unique, just as described in Section 4 of [JWS]. The rules about handling Header Parameters that are not understood by the implementation are also the same. The classes of Header Parameter names are likewise the same. Jones & Hildebrand Expires July 17, 2015 [Page 11]
Internet-Draft JSON Web Encryption (JWE) January 2015 4.1. Registered Header Parameter Names The following Header Parameter names for use in JWEs 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 This parameter has the same meaning, syntax, and processing rules as the "alg" Header Parameter defined in Section 4.1.1 of [JWS], except that the Header Parameter identifies the cryptographic algorithm used to encrypt or determine the value of the Content Encryption Key (CEK). The encrypted content is not usable if the "alg" value does not represent a supported algorithm, or if the recipient does not have a key that can be used with that algorithm. A list of defined "alg" values for this use can be found in the IANA JSON Web Signature and Encryption Algorithms registry defined in [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 Algorithm) Header Parameter The "enc" (encryption algorithm) Header Parameter identifies the content encryption algorithm used to perform authenticated encryption on the Plaintext to produce the Ciphertext and the Authentication Tag. This algorithm MUST be an AEAD algorithm with a specified key length. The encrypted content is not usable if the "enc" value does not represent a supported algorithm. "enc" values should either be registered in the IANA JSON Web Signature and Encryption Algorithms registry defined in [JWA] or be a value that contains a Collision- Resistant Name. The "enc" value is a case-sensitive ASCII string containing a StringOrURI value. This Header Parameter MUST be present and MUST be understood and processed by implementations. A list of defined "enc" values for this use can be found in the IANA JSON Web Signature and Encryption Algorithms registry defined in [JWA]; the initial contents of this registry are the values defined in Section 5.1 of the JSON Web Algorithms (JWA) [JWA] specification. Jones & Hildebrand Expires July 17, 2015 [Page 12]
Internet-Draft JSON Web Encryption (JWE) January 2015 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. When used, this Header Parameter MUST be integrity protected; therefore, it MUST occur only within the JWE Protected Header. Use of this Header Parameter is OPTIONAL. This Header Parameter MUST be understood and processed by implementations. 4.1.4. "jku" (JWK Set URL) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "jku" Header Parameter defined in Section 4.1.2 of [JWS], except that the JWK Set resource contains the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. 4.1.5. "jwk" (JSON Web Key) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "jwk" Header Parameter defined in Section 4.1.3 of [JWS], except that the key is the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. 4.1.6. "kid" (Key ID) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "kid" Header Parameter defined in Section 4.1.4 of [JWS], except that the key hint references the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. This parameter allows originators to explicitly signal a change of key to JWE recipients. 4.1.7. "x5u" (X.509 URL) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "x5u" Header Parameter defined in Section 4.1.5 of [JWS], except that the X.509 public key certificate or certificate chain [RFC5280] contains the public key to which the JWE was encrypted; this can be Jones & Hildebrand Expires July 17, 2015 [Page 13]
Internet-Draft JSON Web Encryption (JWE) January 2015 used to determine the private key needed to decrypt the JWE. 4.1.8. "x5c" (X.509 Certificate Chain) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "x5c" Header Parameter defined in Section 4.1.6 of [JWS], except that the X.509 public key certificate or certificate chain [RFC5280] contains the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. See Appendix B of [JWS] for an example "x5c" value. 4.1.9. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "x5t" Header Parameter defined in Section 4.1.7 of [JWS], except that the certificate referenced by the thumbprint contains the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. Note that certificate thumbprints are also sometimes known as certificate fingerprints. 4.1.10. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "x5t#S256" Header Parameter defined in Section 4.1.8 of [JWS], except that the certificate referenced by the thumbprint contains the public key to which the JWE was encrypted; this can be used to determine the private key needed to decrypt the JWE. Note that certificate thumbprints are also sometimes known as certificate fingerprints. 4.1.11. "typ" (Type) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "typ" Header Parameter defined in Section 4.1.9 of [JWS], except that the type is that of this complete JWE. 4.1.12. "cty" (Content Type) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "cty" Header Parameter defined in Section 4.1.10 of [JWS], except that the type is that of the secured content (the plaintext). 4.1.13. "crit" (Critical) Header Parameter This parameter has the same meaning, syntax, and processing rules as the "crit" Header Parameter defined in Section 4.1.11 of [JWS], Jones & Hildebrand Expires July 17, 2015 [Page 14]
Internet-Draft JSON Web Encryption (JWE) January 2015 except that Header Parameters for a JWE are being referred to, rather than Header Parameters for a JWS. 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 Jones & Hildebrand Expires July 17, 2015 [Page 15]
Internet-Draft JSON Web Encryption (JWE) January 2015 of the agreed upon key. When Direct Key Agreement is employed, let the Content Encryption Key (CEK) be the agreed upon key. When Key Agreement with Key Wrapping is employed, the agreed upon key will be used to wrap the CEK. 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. 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. Compute the encoded key value BASE64URL(JWE Encrypted Key). 8. If the JWE JSON Serialization is being used, repeat this process (steps 1-7) 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. Compute the encoded initialization vector value BASE64URL(JWE Initialization Vector). 11. If a "zip" parameter was included, compress the Plaintext using the specified compression algorithm and let M be the octet sequence representing the compressed Plaintext; otherwise, let M be the octet sequence representing the Plaintext. 12. Create the JSON object(s) containing the desired set of Header Parameters, which together comprise the JOSE Header: if the JWE Compact Serialization is being used, the JWE Protected Header, or if the JWE JSON Serialization is being used, one or more of the JWE Protected Header, the JWE Shared Unprotected Header, and the JWE Per-Recipient Unprotected Header. 13. Compute the Encoded Protected Header value BASE64URL(UTF8(JWE Protected Header)). If the JWE Protected Header is not present (which can only happen when using the JWE JSON Serialization and no "protected" member is present), let this value be the empty string. 14. Let the Additional Authenticated Data encryption parameter be ASCII(Encoded Protected Header). However if a JWE AAD value is Jones & Hildebrand Expires July 17, 2015 [Page 16]
Internet-Draft JSON Web Encryption (JWE) January 2015 present (which can only be the case when using the JWE JSON Serialization), instead let the Additional Authenticated Data encryption parameter be ASCII(Encoded Protected Header || '.' || BASE64URL(JWE AAD)). 15. 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). 16. Compute the encoded ciphertext value BASE64URL(JWE Ciphertext). 17. Compute the encoded authentication tag value BASE64URL(JWE Authentication Tag). 18. If a JWE AAD value is present, compute the encoded AAD value BASE64URL(JWE AAD). 19. Create the desired serialized output. The Compact Serialization of this result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag). The JWE JSON Serialization is described in 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. When there are multiple recipients, it is an application decision which of the recipients' encrypted content must successfully validate for the JWE to be accepted. In some cases, encrypted content for all recipients must successfully validate or the JWE will be considered invalid. In other cases, only the encrypted content for a single recipient needs to be successfully validated. However, in all cases, the encrypted content for at least one recipient MUST successfully validate or the JWE MUST be considered invalid. 1. Parse the JWE representation to extract the serialized values for the components of the JWE. When using the JWE Compact Serialization, these components are the base64url encoded representations of the JWE Protected Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, and the Jones & Hildebrand Expires July 17, 2015 [Page 17]
Internet-Draft JSON Web Encryption (JWE) January 2015 JWE Authentication Tag, and when using the JWE JSON Serialization, these components also include the base64url encoded representation of the JWE AAD and the unencoded JWE Shared Unprotected Header and JWE Per-Recipient Unprotected Header values. When using the JWE Compact Serialization, the JWE Protected Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, and the JWE Authentication Tag are represented as base64url encoded values in that order, with each value being separated from the next by a single period ('.') character, resulting in exactly four delimiting period characters being used. The JWE JSON Serialization is described in Section 7.2. 2. Base64url decode the encoded representations of the JWE Protected Header, the JWE Encrypted Key, the JWE Initialization Vector, the JWE Ciphertext, the JWE Authentication Tag, and the JWE AAD, following the restriction that no line breaks, white space, or other additional characters have been used. 3. Verify that the octet sequence resulting from decoding the encoded JWE Protected Header is a UTF-8 encoded representation of a completely valid JSON object conforming to RFC 7159 [RFC7159]; let the JWE Protected Header be this JSON object. 4. If using the JWE Compact Serialization, let the JOSE Header be the JWE Protected Header. Otherwise, when using the JWE JSON Serialization, let the JOSE Header be the union of the members of the JWE Protected Header, the JWE Shared Unprotected Header and the corresponding JWE Per-Recipient Unprotected Header, all of which must be completely valid JSON objects. During this step, verify that the resulting JOSE Header does not contain duplicate Header Parameter names. When using the JWE JSON Serialization, this restriction includes that the same Header Parameter name also MUST NOT occur in distinct JSON object values that together comprise the JOSE Header. 5. Verify that the implementation understands and can process all fields that it is required to support, whether required by this specification, by the algorithms being used, or by the "crit" Header Parameter value, and that the values of those parameters are also understood and supported. 6. Determine the Key Management Mode employed by the algorithm specified by the "alg" (algorithm) Header Parameter. 7. Verify that the JWE uses a key known to the recipient. Jones & Hildebrand Expires July 17, 2015 [Page 18]
Internet-Draft JSON Web Encryption (JWE) January 2015 8. 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. 9. When Key Wrapping, Key Encryption, or Key Agreement with Key Wrapping are employed, decrypt the JWE Encrypted Key to produce the Content Encryption Key (CEK). The CEK MUST have a length equal to that required for the content encryption algorithm. Note that when there are multiple recipients, each recipient will only be able decrypt any JWE Encrypted Key values that were encrypted to a key in that recipient's possession. It is therefore normal to only be able to decrypt one of the per- recipient JWE Encrypted Key values to obtain the CEK value. Also, see Section 11.5 for security considerations on mitigating timing attacks. 10. When Direct Key Agreement or Direct Encryption are employed, verify that the JWE Encrypted Key value is empty octet sequence. 11. When Direct Encryption is employed, let the Content Encryption Key (CEK) be the shared symmetric key. 12. Record whether the CEK could be successfully determined for this recipient or not. 13. If the JWE JSON Serialization is being used, repeat this process (steps 4-12) for each recipient contained in the representation. 14. Compute the Encoded Protected Header value BASE64URL(UTF8(JWE Protected Header)). If the JWE Protected Header is not present (which can only happen when using the JWE JSON Serialization and no "protected" member is present), let this value be the empty string. 15. Let the Additional Authenticated Data encryption parameter be ASCII(Encoded Protected Header). However if a JWE AAD value is present (which can only be the case when using the JWE JSON Serialization), instead let the Additional Authenticated Data encryption parameter be ASCII(Encoded Protected Header || '.' || BASE64URL(JWE AAD)). 16. 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, Jones & Hildebrand Expires July 17, 2015 [Page 19]
Internet-Draft JSON Web Encryption (JWE) January 2015 returning the decrypted plaintext and validating the JWE Authentication Tag in the manner specified for the algorithm, rejecting the input without emitting any decrypted output if the JWE Authentication Tag is incorrect. 17. If a "zip" parameter was included, uncompress the decrypted plaintext using the specified compression algorithm. 18. If there was no recipient for which all of the decryption steps succeeded, then the JWE MUST be considered invalid. Otherwise, output the Plaintext. In the JWE JSON Serialization case, also return a result to the application indicating for which of the recipients the decryption succeeded and failed. Finally, note that it is an application decision which algorithms may be used in a given context. Even if a JWE can be successfully decrypted, unless the algorithms used in the JWE are acceptable to the application, it SHOULD consider the JWE to be invalid. 5.3. String Comparison Rules The string comparison rules for this specification are the same as those defined in Section 5.3 of [JWS]. 6. Key Identification The key identification methods for this specification are the same as those defined in Section 6 of [JWS], except that the key being identified is the public key to which the JWE was encrypted. 7. Serializations JWEs use one of two serializations: the JWE Compact Serialization or the JWE JSON Serialization. Applications using this specification need to specify what serialization and serialization features are used for that application. For instance, applications might specify that only the JWE JSON Serialization is used, that only JWE JSON Serialization support for a single recipient is used, or that support for multiple recipients is used. JWE implementations only need to implement the features needed for the applications they are designed to support. 7.1. JWE Compact Serialization The JWE Compact Serialization represents encrypted content as a compact, URL-safe string. This string is: Jones & Hildebrand Expires July 17, 2015 [Page 20]
Internet-Draft JSON Web Encryption (JWE) January 2015 BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag) Only one recipient is supported by the JWE Compact Serialization and it provides no syntax to represent JWE Shared Unprotected Header, JWE Per-Recipient Unprotected Header, or JWE AAD values. 7.2. JWE JSON Serialization The JWE JSON Serialization represents encrypted content as a JSON object. This representation is neither optimized for compactness nor URL-safe. Two closely related syntaxes are defined for the JWE JSON Serialization: a fully general syntax, with which content can be encrypted to more than one recipient, and a flattened syntax, which is optimized for the single recipient case. 7.2.1. General JWE JSON Serialization Syntax The following members are defined for use in top-level JSON objects used for the fully general JWE JSON Serialization syntax: protected The "protected" member MUST be present and contain the value BASE64URL(UTF8(JWE Protected Header)) when the JWE Protected Header value is non-empty; otherwise, it MUST be absent. These Header Parameter values are integrity protected. unprotected The "unprotected" member MUST be present and contain the value JWE Shared Unprotected Header when the JWE Shared Unprotected Header value is non-empty; otherwise, it MUST be absent. This value is represented as an unencoded JSON object, rather than as a string. These Header Parameter values are not integrity protected. iv The "iv" member MUST be present and contain the value BASE64URL(JWE Initialization Vector) when the JWE Initialization Vector value is non-empty; otherwise, it MUST be absent. aad The "aad" member MUST be present and contain the value BASE64URL(JWE AAD)) when the JWE AAD value is non-empty; otherwise, it MUST be absent. A JWE AAD value can be included to Jones & Hildebrand Expires July 17, 2015 [Page 21]
Internet-Draft JSON Web Encryption (JWE) January 2015 supply a base64url encoded value to be integrity protected but not encrypted. ciphertext The "ciphertext" member MUST be present and contain the value BASE64URL(JWE Ciphertext). tag The "tag" member MUST be present and contain the value BASE64URL(JWE Authentication Tag) when the JWE Authentication Tag value is non-empty; otherwise, it MUST be absent. recipients The "recipients" member value MUST be an array of JSON objects. Each object contains information specific to a single recipient. This member MUST be present with exactly one array element per recipient, even if some or all of the array element values are the empty JSON object "{}" (which can happen when all Header Parameter values are shared between all recipients and when no encrypted key is used, such as when doing Direct Encryption). The following members are defined for use in the JSON objects that are elements of the "recipients" array: header The "header" member MUST be present and contain the value JWE Per- Recipient Unprotected Header when the JWE Per-Recipient Unprotected Header value is non-empty; otherwise, it MUST be absent. This value is represented as an unencoded JSON object, rather than as a string. These Header Parameter values are not integrity protected. encrypted_key The "encrypted_key" member MUST be present and contain the value BASE64URL(JWE Encrypted Key) when the JWE Encrypted Key value is non-empty; otherwise, it MUST be absent. At least one of the "header", "protected", and "unprotected" members MUST be present so that "alg" and "enc" Header Parameter values are conveyed for each recipient computation. Additional members can be present in both the JSON objects defined above; if not understood by implementations encountering them, they MUST be ignored. Some Header Parameters, including the "alg" parameter, can be shared among all recipient computations. Header Parameters in the JWE Protected Header and JWE Shared Unprotected Header values are shared Jones & Hildebrand Expires July 17, 2015 [Page 22]
Internet-Draft JSON Web Encryption (JWE) January 2015 among all recipients. The Header Parameter values used when creating or validating per- recipient Ciphertext and Authentication Tag values are the union of the three sets of Header Parameter values that may be present: (1) the JWE Protected Header represented in the "protected" member, (2) the JWE Shared Unprotected Header represented in the "unprotected" member, and (3) the JWE Per-Recipient Unprotected Header represented in the "header" member of the recipient's array element. The union of these sets of Header Parameters comprises the JOSE Header. The Header Parameter names in the three locations MUST be disjoint. Each JWE Encrypted Key value is computed using the parameters of the corresponding JOSE Header value in the same manner as for the JWE Compact Serialization. This has the desirable property that each JWE Encrypted Key value in the "recipients" array is identical to the value that would have been computed for the same parameter in the JWE Compact Serialization. Likewise, the JWE Ciphertext and JWE Authentication Tag values match those produced for the JWE Compact Serialization, provided that the JWE Protected Header value (which represents the integrity protected Header Parameter values) matches that used in the JWE Compact Serialization. All recipients use the same JWE Protected Header, JWE Initialization Vector, JWE Ciphertext, and JWE Authentication Tag values, when present, resulting in potentially significant space savings if the message is large. Therefore, all Header Parameters that specify the treatment of the Plaintext value MUST be the same for all recipients. This primarily means that the "enc" (encryption algorithm) Header Parameter value in the JOSE Header for each recipient and any parameters of that algorithm MUST be the same. In summary, the syntax of a JWE using the general JWE JSON Serialization is as follows: { "protected":"<integrity-protected shared header contents>", "unprotected":<non-integrity-protected shared header contents>, "recipients":[ {"header":<per-recipient unprotected header 1 contents>, "encrypted_key":"<encrypted key 1 contents>"}, ... {"header":<per-recipient unprotected header N contents>, "encrypted_key":"<encrypted key N contents>"}], "aad":"<additional authenticated data contents>", "iv":"<initialization vector contents>", "ciphertext":"<ciphertext contents>", "tag":"<authentication tag contents>" Jones & Hildebrand Expires July 17, 2015 [Page 23]
Internet-Draft JSON Web Encryption (JWE) January 2015 } See Appendix A.4 for an example JWE using the general JWE JSON Serialization syntax. 7.2.2. Flattened JWE JSON Serialization Syntax The flattened JWE JSON Serialization syntax is based upon the general syntax, but flattens it, optimizing it for the single recipient case. It flattens it by removing the "recipients" member and instead placing those members defined for use in the "recipients" array (the "header" and "encrypted_key" members) in the top-level JSON object (at the same level as the "ciphertext" member). The "recipients" member MUST NOT be present when using this syntax. Other than this syntax difference, JWE JSON Serialization objects using the flattened syntax are processed identically to those using the general syntax. In summary, the syntax of a JWE using the flattened JWE JSON Serialization is as follows: { "protected":"<integrity-protected header contents>", "unprotected":<non-integrity-protected header contents>, "header":<more non-integrity-protected header contents>, "encrypted_key":"<encrypted key contents>", "aad":"<additional authenticated data contents>", "iv":"<initialization vector contents>", "ciphertext":"<ciphertext contents>", "tag":"<authentication tag contents>" } Note that when using the flattened syntax, just as when using the general syntax, any unprotected Header Parameter values can reside in either the "unprotected" member or the "header" member, or in both. See Appendix A.5 for an example JWE using the flattened JWE JSON Serialization syntax. 8. TLS Requirements The TLS requirements for this specification are the same as those defined in Section 8 of [JWS]. Jones & Hildebrand Expires July 17, 2015 [Page 24]
Internet-Draft JSON Web Encryption (JWE) January 2015 9. Distinguishing between JWS and JWE Objects There are several ways of distinguishing whether an object is a JWS or JWE. All these methods will yield the same result for all legal input values; they may yield different results for malformed inputs. 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 "payload" member and JWEs do not. JWEs have a "ciphertext" member and JWSs do not. o The JOSE Header for a JWS can be distinguished from the JOSE Header for a JWE by examining the "alg" (algorithm) Header Parameter value. If the value represents a digital signature or MAC algorithm, or is the value "none", it is for a JWS; if it represents a Key Encryption, Key Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping, or Direct Encryption algorithm, it is for a JWE. (Extracting the "alg" value to examine is straightforward when using the JWS Compact Serialization or the JWE Compact Serialization and may be more difficult when using the JWS JSON Serialization or the JWE JSON Serialization.) o The JOSE Header for a JWS can also be distinguished from the JOSE Header for a JWE by determining whether an "enc" (encryption algorithm) member exists. If the "enc" member exists, it is a JWE; otherwise, it is a JWS. 10. IANA Considerations 10.1. JSON Web Signature and Encryption Header Parameters 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]. 10.1.1. Registry Contents o Header Parameter Name: "alg" o Header Parameter Description: Algorithm Jones & Hildebrand Expires July 17, 2015 [Page 25]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 Description: Encryption Algorithm 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 Description: Compression Algorithm 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 Description: JWK Set URL 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 Description: JSON Web Key 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: "kid" o Header Parameter Description: Key ID 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: "x5u" o Header Parameter Description: X.509 URL 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 Description: X.509 Certificate Chain o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.8 of [[ this document ]] Jones & Hildebrand Expires July 17, 2015 [Page 26]
Internet-Draft JSON Web Encryption (JWE) January 2015 o Header Parameter Name: "x5t" o Header Parameter Description: X.509 Certificate SHA-1 Thumbprint o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.9 of [[ this document ]] o Header Parameter Name: "x5t#S256" o Header Parameter Description: X.509 Certificate SHA-256 Thumbprint 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: "typ" o Header Parameter Description: Type 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: "cty" o Header Parameter Description: Content Type o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.12 of [[ this document ]] o Header Parameter Name: "crit" o Header Parameter Description: Critical o Header Parameter Usage Location(s): JWE o Change Controller: IESG o Specification Document(s): Section 4.1.13 of [[ this document ]] 11. Security Considerations All of the security issues that are pertinent to any cryptographic application must be addressed by JWS/JWE/JWK agents. Among these issues are protecting the user's asymmetric private and symmetric secret keys and employing countermeasures to various attacks. All the security considerations in the JWS specification also apply to this specification. Likewise, all the security considerations in XML Encryption 1.1 [W3C.REC-xmlenc-core1-20130411] also apply, other than those that are XML specific. 11.1. Key Entropy and Random Values See Section 10.1 of [JWS] for security considerations on key entropy and random values. In addition to the uses of random values listed there, note that random values are also used for content encryption Jones & Hildebrand Expires July 17, 2015 [Page 27]
Internet-Draft JSON Web Encryption (JWE) January 2015 keys (CEKs) and initialization vectors (IVs) when performing encryption. 11.2. Key Protection See Section 10.2 of [JWS] for security considerations on key protection. In addition to the keys listed there that must be protected, implementations performing encryption must protect the key encryption key and the content encryption key. Compromise of the key encryption key may result in the disclosure of all contents protected with that key. Similarly, compromise of the content encryption key may result in disclosure of the associated encrypted content. 11.3. Using Matching Algorithm Strengths Algorithms of matching strengths should be used together whenever possible. For instance, when AES Key Wrap is used with a given key size, using the same key size is recommended when AES GCM is also used. If the key encryption and content encryption algorithms are different, the effective security is determined by the weaker of the two algorithms. Also, see RFC 3766 [RFC3766] for information on determining strengths for public keys used for exchanging symmetric keys. 11.4. Adaptive Chosen-Ciphertext Attacks 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. Additionally, this type of attack can be prevented by restricting the use of a key to a limited set of algorithms -- usually one. This means, for instance, that if the key is marked as being for "RSA-OAEP" only, any attempt to decrypt a message using the "RSA1_5" algorithm with that key should fail immediately due to invalid use of the key. Jones & Hildebrand Expires July 17, 2015 [Page 28]
Internet-Draft JSON Web Encryption (JWE) January 2015 11.5. Timing Attacks 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 recipient substitute a randomly generated CEK and proceed to the next step, to mitigate timing attacks. 12. References 12.1. Normative References [JWA] Jones, M., "JSON Web Algorithms (JWA)", draft-ietf-jose-json-web-algorithms (work in progress), January 2015. [JWK] Jones, M., "JSON Web Key (JWK)", draft-ietf-jose-json-web-key (work in progress), January 2015. [JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", draft-ietf-jose-json-web-signature (work in progress), January 2015. [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification version 1.3", RFC 1951, May 1996. [RFC20] Cerf, V., "ASCII format for Network Interchange", RFC 20, October 1969. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC 4949, August 2007. [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. [RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, March 2014. Jones & Hildebrand Expires July 17, 2015 [Page 29]
Internet-Draft JSON Web Encryption (JWE) January 2015 [UNICODE] The Unicode Consortium, "The Unicode Standard", 1991-, <http://www.unicode.org/versions/latest/>. 12.2. Informative References [AES] National Institute of Standards and Technology (NIST), "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001. [I-D.mcgrew-aead-aes-cbc-hmac-sha2] McGrew, D., Foley, J., and K. Paterson, "Authenticated Encryption with AES-CBC and HMAC-SHA", draft-mcgrew-aead-aes-cbc-hmac-sha2-05 (work in progress), July 2014. [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. [NIST.800-38D] National Institute of Standards and Technology (NIST), "Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC", NIST PUB 800-38D, December 2001. [RFC3218] Rescorla, E., "Preventing the Million Message Attack on Cryptographic Message Syntax", RFC 3218, January 2002. [RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1", RFC 3447, February 2003. [RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For Public Keys Used For Exchanging Symmetric Keys", BCP 86, RFC 3766, April 2004. [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. [RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, September 2009. [W3C.REC-xmlenc-core1-20130411] Eastlake, D., Reagle, J., Hirsch, F., and T. Roessler, Jones & Hildebrand Expires July 17, 2015 [Page 30]
Internet-Draft JSON Web Encryption (JWE) January 2015 "XML Encryption Syntax and Processing Version 1.1", World Wide Web Consortium Recommendation REC-xmlenc-core1- 20130411, April 2013, <http://www.w3.org/TR/2013/REC-xmlenc-core1-20130411/>. 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 (using JSON array notation) is: [84, 104, 101, 32, 116, 114, 117, 101, 32, 115, 105, 103, 110, 32, 111, 102, 32, 105, 110, 116, 101, 108, 108, 105, 103, 101, 110, 99, 101, 32, 105, 115, 32, 110, 111, 116, 32, 107, 110, 111, 119, 108, 101, 100, 103, 101, 32, 98, 117, 116, 32, 105, 109, 97, 103, 105, 110, 97, 116, 105, 111, 110, 46] A.1.1. JOSE Header The following example JWE Protected Header declares that: o The Content Encryption Key is encrypted to the recipient using the RSAES OAEP algorithm to produce the JWE Encrypted Key. o Authenticated encryption is performed on the Plaintext using the AES GCM algorithm with a 256 bit key to produce the Ciphertext and the Authentication Tag. {"alg":"RSA-OAEP","enc":"A256GCM"} Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this value: eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ A.1.2. Content Encryption Key (CEK) Generate a 256 bit random Content Encryption Key (CEK). In this example, the value (using JSON array notation) is: [177, 161, 244, 128, 84, 143, 225, 115, 63, 180, 3, 255, 107, 154, Jones & Hildebrand Expires July 17, 2015 [Page 31]
Internet-Draft JSON Web Encryption (JWE) January 2015 212, 246, 138, 7, 110, 91, 112, 46, 34, 105, 47, 130, 203, 46, 122, 234, 64, 252] A.1.3. 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 within values 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", "p":"1r52Xk46c-LsfB5P442p7atdPUrxQSy4mti_tZI3Mgf2EuFVbUoDBvaRQ- SWxkbkmoEzL7JXroSBjSrK3YIQgYdMgyAEPTPjXv_hI2_1eTSPVZfzL0lf fNn03IXqWF5MDFuoUYE0hzb2vhrlN_rKrbfDIwUbTrjjgieRbwC6Cl0", "q":"wLb35x7hmQWZsWJmB_vle87ihgZ19S8lBEROLIsZG4ayZVe9Hi9gDVCOBm UDdaDYVTSNx_8Fyw1YYa9XGrGnDew00J28cRUoeBB_jKI1oma0Orv1T9aX IWxKwd4gvxFImOWr3QRL9KEBRzk2RatUBnmDZJTIAfwTs0g68UZHvtc", "dp":"ZK-YwE7diUh0qR1tR7w8WHtolDx3MZ_OTowiFvgfeQ3SiresXjm9gZ5KL hMXvo-uz-KUJWDxS5pFQ_M0evdo1dKiRTjVw_x4NyqyXPM5nULPkcpU827 rnpZzAJKpdhWAgqrXGKAECQH0Xt4taznjnd_zVpAmZZq60WPMBMfKcuE", "dq":"Dq0gfgJ1DdFGXiLvQEZnuKEN0UUmsJBxkjydc3j4ZYdBiMRAy86x0vHCj ywcMlYYg4yoC4YZa9hNVcsjqA3FeiL19rk8g6Qn29Tt0cj8qqyFpz9vNDB UfCAiJVeESOjJDZPYHdHY8v1b-o-Z2X5tvLx-TCekf7oxyeKDUqKWjis", "qi":"VIMpMYbPf47dT1w_zDUXfPimsSegnMOA1zTaX7aGk_8urY6R8-ZW1FxU7 AlWAyLWybqq6t16VFd7hQd0y6flUK4SlOydB61gwanOsXGOAOv82cHq0E3 eL4HrtZkUuKvnPrMnsUUFlfUdybVzxyjz9JF_XyaY14ardLSjf4L_FNY" } 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, Jones & Hildebrand Expires July 17, 2015 [Page 32]
Internet-Draft JSON Web Encryption (JWE) January 2015 13, 237, 239, 99, 193, 4, 91, 219, 121, 223, 107, 167, 61, 119, 228, 173, 156, 137, 134, 200, 80, 219, 74, 253, 56, 185, 91, 177, 34, 158, 89, 154, 205, 96, 55, 18, 138, 43, 96, 218, 215, 128, 124, 75, 138, 243, 85, 25, 109, 117, 140, 26, 155, 249, 67, 167, 149, 231, 100, 6, 41, 65, 214, 251, 232, 87, 72, 40, 182, 149, 154, 168, 31, 193, 126, 215, 89, 28, 111, 219, 125, 182, 139, 235, 195, 197, 23, 234, 55, 58, 63, 180, 68, 202, 206, 149, 75, 205, 248, 176, 67, 39, 178, 60, 98, 193, 32, 238, 122, 96, 158, 222, 57, 183, 111, 210, 55, 188, 215, 206, 180, 166, 150, 166, 106, 250, 55, 229, 72, 40, 69, 214, 216, 104, 23, 40, 135, 212, 28, 127, 41, 80, 175, 174, 168, 115, 171, 197, 89, 116, 92, 103, 246, 83, 216, 182, 176, 84, 37, 147, 35, 45, 219, 172, 99, 226, 233, 73, 37, 124, 42, 72, 49, 242, 35, 127, 184, 134, 117, 114, 135, 206] Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives this value (with line breaks for display purposes only): OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8 1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi 6UklfCpIMfIjf7iGdXKHzg A.1.4. 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] Encoding this JWE Initialization Vector as BASE64URL(JWE Initialization Vector) gives this value: 48V1_ALb6US04U3b A.1.5. Additional Authenticated Data Let the Additional Authenticated Data encryption parameter be ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is: [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69, 116, 84, 48, 70, 70, 85, 67, 73, 115, 73, 109, 86, 117, 89, 121, 73, 54, 73, 107, 69, 121, 78, 84, 90, 72, 81, 48, 48, 105, 102, 81] Jones & Hildebrand Expires July 17, 2015 [Page 33]
Internet-Draft JSON Web Encryption (JWE) January 2015 A.1.6. Content Encryption Perform authenticated encryption on the Plaintext with the AES GCM algorithm using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above, requesting a 128 bit Authentication Tag output. The resulting Ciphertext is: [229, 236, 166, 241, 53, 191, 115, 196, 174, 43, 73, 109, 39, 122, 233, 96, 140, 206, 120, 52, 51, 237, 48, 11, 190, 219, 186, 80, 111, 104, 50, 142, 47, 167, 59, 61, 181, 127, 196, 21, 40, 82, 242, 32, 123, 143, 168, 226, 73, 216, 176, 144, 138, 247, 106, 60, 16, 205, 160, 109, 64, 63, 192] The resulting Authentication Tag value is: [92, 80, 104, 49, 133, 25, 161, 215, 173, 101, 219, 211, 136, 91, 210, 145] Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this value (with line breaks for display purposes only): 5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji SdiwkIr3ajwQzaBtQD_A Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication Tag) gives this value: XFBoMYUZodetZdvTiFvSkQ A.1.7. Complete Representation Assemble the final representation: The Compact Serialization of this result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag). The final result in this example (with line breaks for display purposes only) is: Jones & Hildebrand Expires July 17, 2015 [Page 34]
Internet-Draft JSON Web Encryption (JWE) January 2015 eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkEyNTZHQ00ifQ. OKOawDo13gRp2ojaHV7LFpZcgV7T6DVZKTyKOMTYUmKoTCVJRgckCL9kiMT03JGe ipsEdY3mx_etLbbWSrFr05kLzcSr4qKAq7YN7e9jwQRb23nfa6c9d-StnImGyFDb Sv04uVuxIp5Zms1gNxKKK2Da14B8S4rzVRltdYwam_lDp5XnZAYpQdb76FdIKLaV mqgfwX7XWRxv2322i-vDxRfqNzo_tETKzpVLzfiwQyeyPGLBIO56YJ7eObdv0je8 1860ppamavo35UgoRdbYaBcoh9QcfylQr66oc6vFWXRcZ_ZT2LawVCWTIy3brGPi 6UklfCpIMfIjf7iGdXKHzg. 48V1_ALb6US04U3b. 5eym8TW_c8SuK0ltJ3rpYIzOeDQz7TALvtu6UG9oMo4vpzs9tX_EFShS8iB7j6ji SdiwkIr3ajwQzaBtQD_A. XFBoMYUZodetZdvTiFvSkQ A.1.8. 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 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 (using JSON array notation) is: [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114, 111, 115, 112, 101, 114, 46] A.2.1. JOSE Header The following example JWE Protected Header 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. o Authenticated encryption is performed on the Plaintext using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the Ciphertext and the Authentication Tag. {"alg":"RSA1_5","enc":"A128CBC-HS256"} Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Jones & Hildebrand Expires July 17, 2015 [Page 35]
Internet-Draft JSON Web Encryption (JWE) January 2015 Header)) gives this value: eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0 A.2.2. 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.2.3. 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 within values for display purposes only): Jones & Hildebrand Expires July 17, 2015 [Page 36]
Internet-Draft JSON Web Encryption (JWE) January 2015 {"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", "p":"9gY2w6I6S6L0juEKsbeDAwpd9WMfgqFoeA9vEyEUuk4kLwBKcoe1x4HG68 ik918hdDSE9vDQSccA3xXHOAFOPJ8R9EeIAbTi1VwBYnbTp87X-xcPWlEP krdoUKW60tgs1aNd_Nnc9LEVVPMS390zbFxt8TN_biaBgelNgbC95sM", "q":"uKlCKvKv_ZJMVcdIs5vVSU_6cPtYI1ljWytExV_skstvRSNi9r66jdd9-y BhVfuG4shsp2j7rGnIio901RBeHo6TPKWVVykPu1iYhQXw1jIABfw-MVsN -3bQ76WLdt2SDxsHs7q7zPyUyHXmps7ycZ5c72wGkUwNOjYelmkiNS0", "dp":"w0kZbV63cVRvVX6yk3C8cMxo2qCM4Y8nsq1lmMSYhG4EcL6FWbX5h9yuv ngs4iLEFk6eALoUS4vIWEwcL4txw9LsWH_zKI-hwoReoP77cOdSL4AVcra Hawlkpyd2TWjE5evgbhWtOxnZee3cXJBkAi64Ik6jZxbvk-RR3pEhnCs", "dq":"o_8V14SezckO6CNLKs_btPdFiO9_kC1DsuUTd2LAfIIVeMZ7jn1Gus_Ff 7B7IVx3p5KuBGOVF8L-qifLb6nQnLysgHDh132NDioZkhH7mI7hPG-PYE_ odApKdnqECHWw0J-F0JWnUd6D2B_1TvF9mXA2Qx-iGYn8OVV1Bsmp6qU", "qi":"eNho5yRBEBxhGBtQRww9QirZsB66TrfFReG_CcteI1aCneT0ELGhYlRlC tUkTRclIfuEPmNsNDPbLoLqqCVznFbvdB7x-Tl-m0l_eFTj2KiqwGqE9PZ B9nNTwMVvH3VRRSLWACvPnSiwP8N5Usy-WRXS-V7TbpxIhvepTfE0NNo" } 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, Jones & Hildebrand Expires July 17, 2015 [Page 37]
Internet-Draft JSON Web Encryption (JWE) January 2015 248, 63, 165, 141, 4, 207, 249, 193, 79, 131, 0, 169, 233, 127, 167, 101, 151, 125, 56, 112, 111, 248, 29, 232, 90, 29, 147, 110, 169, 146, 114, 165, 204, 71, 136, 41, 252] Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives this value (with line breaks for display purposes only): UGhIOguC7IuEvf_NPVaXsGMoLOmwvc1GyqlIKOK1nN94nHPoltGRhWhw7Zx0-kFm 1NJn8LE9XShH59_i8J0PH5ZZyNfGy2xGdULU7sHNF6Gp2vPLgNZ__deLKxGHZ7Pc HALUzoOegEI-8E66jX2E4zyJKx-YxzZIItRzC5hlRirb6Y5Cl_p-ko3YvkkysZIF NPccxRU7qve1WYPxqbb2Yw8kZqa2rMWI5ng8OtvzlV7elprCbuPhcCdZ6XDP0_F8 rkXds2vE4X-ncOIM8hAYHHi29NX0mcKiRaD0-D-ljQTP-cFPgwCp6X-nZZd9OHBv -B3oWh2TbqmScqXMR4gp_A A.2.4. 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] Encoding this JWE Initialization Vector as BASE64URL(JWE Initialization Vector) gives this value: AxY8DCtDaGlsbGljb3RoZQ A.2.5. Additional Authenticated Data Let the Additional Authenticated Data encryption parameter be ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is: [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 48, 69, 120, 88, 122, 85, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48] A.2.6. Content Encryption Perform authenticated encryption on the Plaintext with the AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above. The steps for doing this using the values from 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, Jones & Hildebrand Expires July 17, 2015 [Page 38]
Internet-Draft JSON Web Encryption (JWE) January 2015 112, 56, 102] The resulting Authentication Tag value is: [246, 17, 244, 190, 4, 95, 98, 3, 231, 0, 115, 157, 242, 203, 100, 191] Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this value: KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication Tag) gives this value: 9hH0vgRfYgPnAHOd8stkvw A.2.7. Complete Representation Assemble the final representation: The Compact Serialization of this result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag). The final result in this example (with line breaks for display purposes only) is: 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.2.8. 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 Jones & Hildebrand Expires July 17, 2015 [Page 39]
Internet-Draft JSON Web Encryption (JWE) January 2015 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_128_CBC_HMAC_SHA_256 for content encryption. The representation of this plaintext (using JSON array notation) is: [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114, 111, 115, 112, 101, 114, 46] A.3.1. JOSE Header The following example JWE Protected 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. o Authenticated encryption is performed on the Plaintext using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the Ciphertext and the Authentication Tag. {"alg":"A128KW","enc":"A128CBC-HS256"} Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this value: eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0 A.3.2. 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.3.3. 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: Jones & Hildebrand Expires July 17, 2015 [Page 40]
Internet-Draft JSON Web Encryption (JWE) January 2015 {"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] Encoding this JWE Encrypted Key as BASE64URL(JWE Encrypted Key) gives this value: 6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ A.3.4. 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] Encoding this JWE Initialization Vector as BASE64URL(JWE Initialization Vector) gives this value: AxY8DCtDaGlsbGljb3RoZQ A.3.5. Additional Authenticated Data Let the Additional Authenticated Data encryption parameter be ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is: [101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 66, 77, 84, 73, 52, 83, 49, 99, 105, 76, 67, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48] A.3.6. Content Encryption Perform authenticated encryption on the Plaintext with the AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above. The steps for doing this using the values from this example are detailed in Appendix B. The resulting Ciphertext is: [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6, Jones & Hildebrand Expires July 17, 2015 [Page 41]
Internet-Draft JSON Web Encryption (JWE) January 2015 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143, 112, 56, 102] The resulting Authentication Tag value is: [83, 73, 191, 98, 104, 205, 211, 128, 201, 189, 199, 133, 32, 38, 194, 85] Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this value: KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication Tag) gives this value: U0m_YmjN04DJvceFICbCVQ A.3.7. Complete Representation Assemble the final representation: The Compact Serialization of this result is the string BASE64URL(UTF8(JWE Protected Header)) || '.' || BASE64URL(JWE Encrypted Key) || '.' || BASE64URL(JWE Initialization Vector) || '.' || BASE64URL(JWE Ciphertext) || '.' || BASE64URL(JWE Authentication Tag). The final result in this example (with line breaks for display purposes only) is: eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0. 6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ. AxY8DCtDaGlsbGljb3RoZQ. KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY. U0m_YmjN04DJvceFICbCVQ A.3.8. 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. Jones & Hildebrand Expires July 17, 2015 [Page 42]
Internet-Draft JSON Web Encryption (JWE) January 2015 A.4. Example JWE using General JWE JSON Serialization This section contains an example using the general JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the same plaintext to multiple recipients. Two recipients are present in this example. The algorithm and key used for the first recipient are the same as that used in 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), JWE Initialization Vector, and JWE Protected Header are shared by all recipients (which must be the case, since the Ciphertext and Authentication Tag are also shared). 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 Authenticated encryption is performed on the Plaintext using the AES_128_CBC_HMAC_SHA_256 algorithm to produce the common JWE Ciphertext and JWE Authentication Tag values. The JWE Protected Header value representing this is: {"enc":"A128CBC-HS256"} Encoding this JWE Protected Header as BASE64URL(UTF8(JWE Protected Header)) gives this value: eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0 Jones & Hildebrand Expires July 17, 2015 [Page 43]
Internet-Draft JSON Web Encryption (JWE) January 2015 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"} A.4.4. Complete JOSE Header Values Combining the per-recipient, protected, and unprotected header values supplied, the JOSE 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 ASCII(BASE64URL(UTF8(JWE Protected Header))). This value is: [101, 121, 74, 108, 98, 109, 77, 105, 79, 105, 74, 66, 77, 84, 73, 52, 81, 48, 74, 68, 76, 85, 104, 84, 77, 106, 85, 50, 73, 110, 48] A.4.6. Content Encryption Perform authenticated encryption on the Plaintext with the AES_128_CBC_HMAC_SHA_256 algorithm using the CEK as the encryption key, the JWE Initialization Vector, and the Additional Authenticated Data value above. The steps for doing this using the values from 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: Jones & Hildebrand Expires July 17, 2015 [Page 44]
Internet-Draft JSON Web Encryption (JWE) January 2015 [51, 63, 149, 60, 252, 148, 225, 25, 92, 185, 139, 245, 35, 2, 47, 207] Encoding this JWE Ciphertext as BASE64URL(JWE Ciphertext) gives this value: KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY Encoding this JWE Authentication Tag as BASE64URL(JWE Authentication Tag) gives this value: Mz-VPPyU4RlcuYv1IwIvzw A.4.7. Complete JWE JSON Serialization Representation The complete JWE JSON Serialization for these values is as follows (with line breaks within values for display purposes only): { "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0", "unprotected": {"jku":"https://server.example.com/keys.jwks"}, "recipients":[ {"header": {"alg":"RSA1_5","kid":"2011-04-29"}, "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","kid":"7"}, "encrypted_key": "6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ"}], "iv": "AxY8DCtDaGlsbGljb3RoZQ", "ciphertext": "KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY", "tag": "Mz-VPPyU4RlcuYv1IwIvzw" } Jones & Hildebrand Expires July 17, 2015 [Page 45]
Internet-Draft JSON Web Encryption (JWE) January 2015 A.5. Example JWE using Flattened JWE JSON Serialization This section contains an example using the flattened JWE JSON Serialization syntax. This example demonstrates the capability for encrypting the plaintext to a single recipient in a flattened JSON structure. The values in this example are the same as those for the second recipient of the previous example in Appendix A.4. The complete JWE JSON Serialization for these values is as follows (with line breaks within values for display purposes only): { "protected": "eyJlbmMiOiJBMTI4Q0JDLUhTMjU2In0", "unprotected": {"jku":"https://server.example.com/keys.jwks"}, "header": {"alg":"A128KW","kid":"7"}, "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 5.2 and 5.2.3 of JWA, the AES_CBC_HMAC_SHA2 family of algorithms are implemented using Advanced Encryption Standard (AES) in Cipher Block Chaining (CBC) mode with PKCS #7 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 (using JSON array notation) is: [4, 211, 31, 197, 84, 157, 252, 254, 11, 100, 157, 250, 63, 170, 106, Jones & Hildebrand Expires July 17, 2015 [Page 46]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 #7 padding using the ENC_KEY above. The Plaintext in this example is: [76, 105, 118, 101, 32, 108, 111, 110, 103, 32, 97, 110, 100, 32, 112, 114, 111, 115, 112, 101, 114, 46] The encryption result is as follows, which is the Ciphertext output: [40, 57, 83, 181, 119, 33, 133, 148, 198, 185, 243, 24, 152, 230, 6, 75, 129, 223, 127, 19, 210, 82, 183, 230, 168, 33, 215, 104, 143, 112, 56, 102] 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, 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] Jones & Hildebrand Expires July 17, 2015 [Page 47]
Internet-Draft JSON Web Encryption (JWE) January 2015 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] 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.REC-xmlenc-core1-20130411] and RFC 5652 [RFC5652] as possible, while utilizing simple, compact JSON-based data structures. Jones & Hildebrand Expires July 17, 2015 [Page 48]
Internet-Draft JSON Web Encryption (JWE) January 2015 Special thanks are due to John Bradley, Eric Rescorla, and Nat Sakimura for the discussions that helped inform the content of this specification, to Eric Rescorla and Joe Hildebrand for allowing the reuse of text from [I-D.rescorla-jsms] in this document, and to Eric Rescorla for co-authoring many drafts of this specification. Thanks to Axel Nennker, Emmanuel Raviart, Brian Campbell, and Edmund Jay for validating the examples in this specification. This specification is the work of the JOSE Working Group, which includes dozens of active and dedicated participants. In particular, the following individuals contributed ideas, feedback, and wording that influenced this specification: Richard Barnes, John Bradley, Brian Campbell, Alissa Cooper, Breno de Medeiros, Stephen Farrell, Dick Hardt, Jeff Hodges, Russ Housley, Edmund Jay, Scott Kelly, Stephen Kent, Barry Leiba, James Manger, Matt Miller, Kathleen Moriarty, Tony Nadalin, Hideki Nara, Axel Nennker, Ray Polk, Emmanuel Raviart, Eric Rescorla, Pete Resnick, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and Sean Turner. Jim Schaad and Karen O'Donoghue chaired the JOSE working group and Sean Turner, Stephen Farrell, and Kathleen Moriarty served as Security area directors during the creation of this specification. Appendix D. Document History [[ to be removed by the RFC Editor before publication as an RFC ]] -40 o Clarified the definitions of UTF8(STRING) and ASCII(STRING). -39 o No changes were made, other than to the version number and date. -38 o Replaced uses of the phrases "JWS object" and "JWE object" with "JWS" and "JWE". o Added member names to the JWE JSON Serialization Overview. o Applied other minor editorial improvements. -37 Jones & Hildebrand Expires July 17, 2015 [Page 49]
Internet-Draft JSON Web Encryption (JWE) January 2015 o Restricted algorithm names to using only ASCII characters. o When describing actions taken as a result of validation failures, changed statements about rejecting the JWE to statements about considering the JWE to be invalid. o Added the CRT parameter values to example RSA private key representations. -36 o Defined a flattened JWE JSON Serialization syntax, which is optimized for the single recipient case. o Clarified where white space and line breaks may occur in JSON objects by referencing Section 2 of RFC 7159. -35 o Addressed AppsDir reviews by Ray Polk. -34 o Addressed IESG review comments by Barry Leiba, Alissa Cooper, Pete Resnick, Stephen Farrell, and Richard Barnes. -33 o Noted that certificate thumbprints are also sometimes known as certificate fingerprints. o Changed to use the term "authenticated encryption" instead of "encryption", where appropriate. o Acknowledged additional contributors. -32 o Addressed Gen-ART review comments by Russ Housley. o Addressed secdir review comments by Scott Kelly, Tero Kivinen, and Stephen Kent. -31 o Updated the reference to draft-mcgrew-aead-aes-cbc-hmac-sha2. -30 Jones & Hildebrand Expires July 17, 2015 [Page 50]
Internet-Draft JSON Web Encryption (JWE) January 2015 o Added subsection headings within the Overview section for the two serializations. o Added references and cleaned up the reference syntax in a few places. o Applied minor wording changes to the Security Considerations section and made other local editorial improvements. -29 o Replaced the terms JWS Header, JWE Header, and JWT Header with a single JOSE Header term defined in the JWS specification. This also enabled a single Header Parameter definition to be used and reduced other areas of duplication between specifications. -28 o Specified the use of PKCS #7 padding with AES CBC, rather than PKCS #5. (PKCS #7 is a superset of PKCS #5, and is appropriate for the 16 octet blocks used by AES CBC.) o Revised the introduction to the Security Considerations section. Also moved a security consideration item here from the JWA draft. -27 o Described additional security considerations. o Added the "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) header parameter. -26 o Noted that octet sequences are depicted using JSON array notation. o Updated references, including to W3C specifications. -25 o Corrected two external section number references that had changed. o Corrected a typo in an algorithm name in the prose of an example. -24 o Corrected complete JSON Serialization example. Jones & Hildebrand Expires July 17, 2015 [Page 51]
Internet-Draft JSON Web Encryption (JWE) January 2015 o Replaced uses of the term "associated data" wherever it was used to refer to a data value with "additional authenticated data", since both terms were being used as synonyms, causing confusion. o Updated the JSON reference to RFC 7159. o Thanked Eric Rescorla for helping to author of most of the drafts of this specification and removed him from the current author list. -23 o Corrected a use of the word "payload" to "plaintext". -22 o Corrected RFC 2119 terminology usage. o Replaced references to draft-ietf-json-rfc4627bis with RFC 7158. -21 o Changed some references from being normative to informative, addressing issue #90. o Applied review comments to the JSON Serialization section, addressing issue #178. -20 o Made terminology definitions more consistent, addressing issue #165. o Restructured the JSON Serialization section to call out the parameters used in hanging lists, addressing issue #178. o Replaced references to RFC 4627 with draft-ietf-json-rfc4627bis, addressing issue #90. -19 o Reordered the key selection parameters. -18 o Updated the mandatory-to-implement (MTI) language to say that applications using this specification need to specify what serialization and serialization features are used for that Jones & Hildebrand Expires July 17, 2015 [Page 52]
Internet-Draft JSON Web Encryption (JWE) January 2015 application, addressing issue #176. o Changes to address editorial and minor issues #89, #135, #165, #174, #175, #177, #179, and #180. o Used Header Parameter Description registry field. -17 o Refined the "typ" and "cty" definitions to always be MIME Media Types, with the omission of "application/" prefixes recommended for brevity, addressing issue #50. o Updated the mandatory-to-implement (MTI) language to say that general-purpose implementations must implement the single recipient case for both serializations whereas special-purpose implementations can implement just one serialization if that meets the needs of the use cases the implementation is designed for, addressing issue #176. o Explicitly named all the logical components of a JWE and defined the processing rules and serializations in terms of those components, addressing issues #60, #61, and #62. o Replaced verbose repetitive phases such as "base64url encode the octets of the UTF-8 representation of X" with mathematical notation such as "BASE64URL(UTF8(X))". o Header Parameters and processing rules occurring in both JWS and JWE are now referenced in JWS by JWE, rather than duplicated, addressing issue #57. o Terms used in multiple documents are now defined in one place and incorporated by reference. Some lightly used or obvious terms were also removed. This addresses issue #58. -16 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 & Hildebrand Expires July 17, 2015 [Page 53]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 & Hildebrand Expires July 17, 2015 [Page 54]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 & Hildebrand Expires July 17, 2015 [Page 55]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 & Hildebrand Expires July 17, 2015 [Page 56]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 & Hildebrand Expires July 17, 2015 [Page 57]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 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 & Hildebrand Expires July 17, 2015 [Page 58]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 & Hildebrand Expires July 17, 2015 [Page 59]
Internet-Draft JSON Web Encryption (JWE) January 2015 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 & Hildebrand Expires July 17, 2015 [Page 60]
Internet-Draft JSON Web Encryption (JWE) January 2015 Authors' Addresses Michael B. Jones Microsoft Email: mbj@microsoft.com URI: http://self-issued.info/ Joe Hildebrand Cisco Systems, Inc. Email: jhildebr@cisco.com Jones & Hildebrand Expires July 17, 2015 [Page 61]