algorithm

The "alg" (algorithm) Header Parameter identifies the cryptographic algorithm used to secure the JWS. The JWS Signature value is not valid if the "alg" value does not represent a supported algorithm or if there is not a key for use with that algorithm associated with the party that digitally signed or MACed the content. "alg" 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 "alg" 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.