Will padd the param to be of the correct length for the encryption alg.

        :type b: bytes
        :rtype: bytes

def _pad(self, b):
        """
        Will padd the param to be of the correct length for the encryption alg.

        :type b: bytes
        :rtype: bytes
        """
        return b + (self.bs - len(b) % self.bs) * chr(self.bs - len(b) % self.bs).encode("UTF-8")