Conditional access system and method thereof

A conditional access system comprising:

• a resource subscriber management system for transmitting to each receiver via a satellite channel a first time period for transmitting an entitlement management message (EMM) and a second time period for transmitting a receive control message (RCM), said EMM being non-periodically transmitted at a predetermined time to check whether or not a decoder in a receiving party is legal, said RCM being non-periodically transmitted at a predetermined time to check information on the amount used, and, at the same time, for providing a key value for scrambling;
• a transmitting unit for generating a random-number from said key value and scrambling program sources of a broadcasting station before transmitting them to each receiver;
• a receiver for receiving and decoding said RCM and/or EMM, checking whether or not a smart card is permitted, and transmitting information on the amount used by a user to said resource subscriber management system, said information being registered in the smart card, and, at the same time, for decrypting said key value and generating a random-number using the decrypted key value to reconstruct original data from scrambled data;
• and
• a power supply unit for turning on at the beginning of the first and second time periods and supplying power to said receiver during the first and second time periods.

A conditional access method for a system having a resource subscriber management system and a receiver that includes a smart card, the method comprising the steps of:

• predetermining a first time period to transmit an entitlement management message (EMM) and a second time period to transmit a receive control message (RCM) and transmitting the predetermined time periods to the receiver;
• scrambling program sources of a broadcasting station with a random-number generated from a key value and transmitting the scrambled sources to the receiver;
• turning on a power supply unit at the beginning of the first and second time periods, the power supplying power to the receiver during the first and second time periods;
• receiving said RCM and EMM from the management system during the first and second time periods, respectively;
• checking whether the smart card is permitted and transmitting information on the amount used by a user registered in the smart card to the management system by decoding the received RCM and EMM;
• and
• decrypting said key value and generating a random-number using the decrypted key value to reconstruct original data from the scrambled sources.