SECURITY SYSTEM FOR TELEVISION SIGNAL ENCRYPTION

专利名称：SECURITY SYSTEM FOR TELEVISION SIGNAL

ENCRYPTION

发明人：MASON, Arthur, Gordon申请号：EP84902601.0申请日：19840702公开号：EP0151147A1公开日：19850814

摘要： A conditional access system for the reception and transmission by radio wavesof scrambled television signals improves the reliability of the reception signal by

transmitting a key used to descramble the television signal in an information block whichis itself encrypted by the key signal. Upon receipt, the receiver, after having decryptedblock information, compares the key signal recovered from the block key signal suppliedto the receiver to decrypt the block. Descrambling will be allowed only if the comparisonshows that the two key signals are the same. The system can also provide informationabout the credit status of each user, status that is transmitted by radio waves. In order toensure rapid operation, the credit status of the signal is sent repeatedly and anothersignal is attached, which is used at the receiver to prevent repeated accumulation.Another arrangement enables the transmitter to transmit a signal indicating the totalamount of credit purchased by a user as well as the incorporation of a counter at theuser's receiver to accumulate all programs watched payments by user. A simple

comparison between two signals is sufficient to determine whether the user can watch aprogram.

申请人：INDEPENDENT BROADCASTING AUTHORITY

地址：70 Brompton Road London SW3 1EY GB

国籍：GB

代理机构：Crawford, Andrew Birkby, et al

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