| 摘要 |
The present invention provides a method for decrypting encrypted content transmitted from an operator to a plurality of users where said operator further provides security information allowing for the decryption of said content. The method has the advantage of satisfying the goal of providing the capability for detecting a fraudulent user who retransmits control words extracted from the security information to other users. The method provides for the achievement of the goal without incurring extra overhead in addition to the transmitted content and security information. The method makes use of control words which are based on multiple solutions provided by collisions in mathematical functions and involves the observation of choices of control words retransmitted by the fraudulent user.
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