Initializes the automatic key generation function which derives a key from the data fed to it via SetAutoKeyData (string), when all data is input then AutoKeyFinish () must be called to compete key generation. If the AutoKeyStart method is not called, then the SetAutoKeyData method is used to pass the path to a file, which is then used to encrypt the signature, when AutoKeyStart is called then SetAutoKeyData is used to pass in string literals as data.