Patent ID: 8804965

Claim:
A method of decrypting control words for a plurality of terminals, said plurality of terminals comprising terminals that are mechanically and electronically independent of one another, said plurality of terminals comprising a terminal that has detected an absence of at least one control word to descramble at least one cryptoperiod of multimedia content, said method comprising, at a control-word server that is in data communication with said plurality of terminals, receiving, from said terminal that has detected an absence of at least one control word to descramble at least one cryptoperiod of multimedia content, a request containing at least one cryptogram corresponding to said absent control word and, in response to receiving said request containing at least one cryptogram corresponding to said absent control word, causing said control-word server to transmit said absent control word to said terminal, determining a probability that security of additional control words is compromised in said terminal, causing said control-word server to determine, for said terminal, a number of additional control words to be transmitted to said terminal as a function of said probability that security of said additional control words is compromised, and causing said control-word server to transmit, to said terminal, in addition to said absent control word, said determined number of additional control words to enable said terminal to descramble additional cryptoperiods of said multimedia content in addition to a cryptoperiod of said multimedia content that can be descrambled using said absent control word.