SYSTEM FOR ENABLING DESCRAMBLING ON A SELECTIVE-SUBSCRIPTION BASIS IN A SUBSCRIBER COMMUNICATION NETWORK

摘要

SYSTEM FOR ENABLING DESCRAMBLING ON A SELECTIVE-SUBSCRIPTIONBASIS IN A SUBSCRIBER COMMUNICATION NETWORKABSTRACT OF THE DISCLOSUREA system in a subscriber television network forenabling descrambling of a received scrambled signal on aprepaid basis and/or an impulse-purchase basis. A receivedmask signal uniquely related to the scrambled signal iscompared with a received authorization signal indicatingwhether the subscriber is authorized to receive thescrambled signal on a prepaid basis and a prepaid signal forenabling descrambling is provided when the compared signalsmatch. A not-prepaid signal is provided when they do notmatch. A received cost signal indicating the charge fordescrambling the scrambled signal and a received creditsignal indicating the subscriber's accumulated credit areprocessed with reference to a stored record of thesubscriber's prior accumulated charges to determine whetherthe subscriber has sufficient available credit to pay fordescrambling of the scrambled signal. If a program is notprepaid and if sufficient credit is available, thesubscriber is given the option of causing the signal to bedescrambled on an impulse-purchase basis. To prevent asubscriber from obtaining descrambling through such deceitas changing the mask, authorization, cost and/or creditsignals, these signals are processed with key signals whichare used in scrambling and descrambling the televisionsignal such that descrambling is prevented if any of themask et al signals is changed.