'Create a message authentication code (MAC) for the given packet using
the outgoing MAC values.
@type seqid: L{int}
@param seqid: The sequence ID of the outgoing packet.
@type data: L{bytes}
@param data: The data to create a MAC for.
@rtype: L{str}
@return: The serialized MAC.'

def makeMAC(self, seqid, data):

    if (not self.outMAC[0]):
        return ''
    data = (struct.pack('>L', seqid) + data)
    return hmac.HMAC(self.outMAC.key, data, self.outMAC[0]).digest()
