'Verify the validity of an ElGamal signature.
:Parameter M: The expected message.
:Type M: byte string or long
:Parameter signature: The ElGamal signature to verify.
:Type signature: A tuple with 2 longs as return by `sign`
:Return: True if the signature is correct, False otherwise.'

def verify(self, M, signature):

    return pubkey.verify(self, M, signature)
