Patent ID: 7071835

Claim:
A home control system that uses electrical power lines for communications, comprising: a plurality of components that are connected for communications among themselves through the electrical power lines, wherein the communications among the plurality of components is established through a single communication protocol; a sending one of the components being configured to send messages over the electrical power lines in accordance with acts comprising: calculating a first message authentication code based on a predefined one-way function of data from a message and of a key value that is shared between sending and receiving components; including the message authentication code in the message; sending the message over the electrical power lines; a receiving one of the components being configured to receive messages in accordance with acts comprising: receiving a message over the electrical power lines; calculating a second message authentication code based on the predefined one-way function of the data from the message and of the current shared key value; concluding that the message is either not authentic or contains a data error if the first and second message authentication codes do not match.