Patent ID: 7986781
Filing Date: 2011-07-26
Classification: H04N

Abstract:
1. A method for controlling access to data encrypted by control words, said control words being received by a security module in control messages and returned to a processing unit for accessing encrypted data, said control messages containing at least a first control word and a second control word, said first and second control words each allowing access to data encrypted by said control words during a respective cryptoperiod, the method comprising the steps of: sending said encrypted data to at least one processing unit; and sending the control messages to said processing unit, each of the control messages being sent to the processing unit after the sending of the data encrypted by said first control word and before the sending of the data encrypted by said second control word; wherein the time shifting between the sending to the processing unit of data encrypted by said first control word and the sending of the control message containing said first control word and said second control word is greater than 75% of the cryptoperiod, said time shifting being determined in such a way as to prevent the processing unit decrypting the encrypted data by using only one control message of two consecutive control messages.