encryption

The "enc" (encryption algorithm) Header Parameter identifies the content encryption algorithm used to perform authenticated encryption on the plaintext to produce the ciphertext and the Authentication Tag. This algorithm MUST be an AEAD algorithm with a specified key length. The encrypted content is not usable if the "enc" value does not represent a supported algorithm. "enc" values should either be registered in the IANA "JSON Web Signature and Encryption Algorithms" registry established by (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.