Patent ID: 7783043

Claim:
A device for use in a system with multiple receiving units, and multiple intermediate units each configured to communicate with the device and at least some of the multiple receiving units, the device comprising: a communication module configured to send information toward and receive information from the receiving units and the intermediate units; a memory; and a processor coupled to the memory and the communication module and configured to: cause the communication module to send information toward each of the receiving units for the receiving units to obtain a key chain corresponding to that receiving unit, each key chain containing a plurality of keys, each key in each key chain being related to other keys in the respective key chains by at least one inverse of a one-way function; select a key from a key chain associated with a particular receiving unit and stored in the memory; and cause the communication module to send the selected key, and an indication of which receiving unit the selected key is associated with, toward the intermediate unit associated with the particular receiving unit.