Patent ID: 6848051
Filing Date: 2005-01-25
Classification: H04N

Abstract:
1. A method for determining that all of a scrambled message has been successfully received, the scrambled message being scrambled in accordance with a scrambling key and being capable of being descrambled in accordance with a descrambling key, descrambling key generating information for generating the descrambling key being comprised within a control message (ECM) associated with the scrambled message, the method comprising: providing a scrambled message scrambled in accordance with a scrambling key; generating an unmodified ECM comprising descrambling key generating information for generating a descrambling key for descrambling the scrambled message; generating a first derived value based on the scrambled message using a first value derivation function: applying a first modification function to the unmodified ECM, the first modification function being based, at least in pan, on the first derived value, thereby producing a modified ECM; transmitting the scrambled message and the modified ECM to a receiver; and performing, at the receiver, the following steps: