Section: 13.2.4.4 Protection using JSON Web Encryption (JWE) 13.2.4.4.0 General
Content: The SEPP shall use JSON Web Encryption (JWE) as specified in RFC 7516 [59] for the protection of reformatted HTTP messages between the SEPPs. All encryption methods supported by JWE are AEAD methods, i.e. methods that encrypt and integrity protect in one single operation and can additionally integrity protect additional data. The dataToIntegrityProtectAndCipher and dataToIntegrityProtect blocks shall be input to JWE as plaintext and JWE Additional Authenticated Data (AAD) respectively. The JWE AEAD algorithm generates JWE encrypted text (ciphertext) and a JWE Authentication Tag (Message Authentication Code). The ciphertext is the output from symmetrically encrypting the plaintext, while the authentication tag is a value that verifies the integrity of both the generated ciphertext and the Additional Authenticated Data. The Flattened JWE JSON Serialization syntax shall be used to represent JWE as a JSON object. The session key shared between the two SEPPs, as specified in clause 13.2.4.4.1, shall be used as the Content Encryption Key (CEK) value to the algorithm indicated in the Encryption algorithm ("enc") parameter in the JOSE header. The algorithm ("alg") parameter in the JOSE header denoting the key exchange method shall be set to "dir", i.e. "Direct use of a shared symmetric key as the CEK". The 3GPP profile for supported cipher suites in the "enc" parameter is described in clause 13.2.4.9. The generated JWE object shall be transmitted on the N32-f interface in the payload body of a SEPP to SEPP HTTP/2 message.