The repeater of the present invention communicates data signals over power lines. The repeater of one embodiment includes at least one modem that receives a data packet and attempts to decrypt the data packet with a first and/or second encryption key. If the packet is successfully decrypted using the first encryption key, the packet is encrypted using the second encryption and transmitted over the power line. If the packet is successfully decrypted using the second encryption key, the packet is encrypted using the first encryption and transmitted over the power line.