Verify request authenticator.
        :return: True if verification failed else False
        :rtype: boolean

def VerifyCoARequest(self):
        """Verify request authenticator.
        :return: True if verification failed else False
        :rtype: boolean
        """
        assert(self.raw_packet)
        hash = md5_constructor(self.raw_packet[0:4] + 16 * six.b('\x00') +
                self.raw_packet[20:] + self.secret).digest()
        return hash == self.authenticator