Patent ID: 7925020
Filing Date: 2011-04-12
Classification: G06F,H04N

Abstract:
1. A method of descrambling a broadcast signal in a broadcast receiver, the method comprising: generating a first Data Encryption System (DES) key from a first Copy Protection (CP) key and a first value in a DES key generator, the first value being generated from a Entitlement Control Message (ECM) Packet ID (PID) and a Local Transport Stream ID (LTSID) of a first broadcast signal received through a first broadcast channel; descrambling the first broadcast signal in a descrambler using the first DES key prior to a broadcast channel change; generating a second DES key from the first CP key and a second value in the DES key generator, the second value being generated from a ECM PID and a LTSID of a second broadcast signal received through a second broadcast channel; and descrambling the second broadcast signal in the descrambler using the second DES key during a CP key refresh and after the broadcast channel change.