KEY SIGNAL ENCRYPTION AND DISTRIBUTION SYSTEM FOR CONTROLLING SCRAMBLING AND SELECTIVE, REMOTE DESCRAMBLING OF TELEVISION SIGNALS

摘要

KEY SIGNAL ENCRYPTION AND DISTRIBUTION SYSTEM FORCONTROLLING SCRAMBLING AND SELECTIVE,REMOTE DESCRAMBLING OF TELEVISION SIGNALSABSTRACT OF THE DISCLOSUREA system and method for scrambling and selectivelydescrambling television signals that are transmitted tosubscribers' descramblers in a subscription televisionsystem. A working key signal is generated by processing an"initialization vector" signal in accordance with the DESalgorithm upon the algorithm being keyed by either a commoncategory key signal or some other key signal. A uniqueencryption keystream is generated by processing theinitialization vector signal in accordance with the DESalgorithm upon the algorithm being keyed by the working keysignal. A television signal is scrambled in accordancewith the unique encryption keystream to provide a scrambledtelevision signal. A plurality of unique encryptedcategory key signals individually addressed to differentselected subscribers' descramblers are generated byprocessing the initial common category key signal inaccordance with the DES algorithm upon the algorithm beingkeyed by a plurality of different "unit key" signals uniqueto different selected descramblers. The scrambledtelevision signal, the initialization vector signal, andthe plurality of encrypted category key signals arebroadcast to the descramblers. A corresponding tier of DESalgorithms are employed at the descrambler to reproduce theencryption keystream; and the TV signal is descrambledin accordance therewith. Each descrambler has its uniqueunit key signal stored in a secure memory for use inreproducing the common catagory key signal when thedescrambler is addressed by its unique encrypted cateaorykey signal.