said by pulsar777:the ATA and PC both are connected to the router, which connected to cable modem. Do I need connect it through the hub before router? Also, I read somewhere that encryption somehow use MAC address of ATA for the key.
Yes, the hub basically replicates all packets to all ports, so your PC can sniff the traffic that is supposed to go to the ATA. With a switch (which is built into today's routers), the traffic only goes to the port of the device that is meant to receive it.
The encryption can be done in different ways, the most common one is to save a unique encryption key in the ATA and all the provisioning files feed to the ATA afterwards will be encrypted with that key.