SECURE DESCRAMBLING OF AN AUDIO / VIDEO DATA STREAM

摘要

The present invention discloses a method to prevent control word sharing by using advanced features of a security module rendering fastidious the capture of control words by hackers. The method ensures a secure descrambling of a scrambled audio/video stream by a receiver provided with a chip set connected to a security module. The security module receives seed data encrypted by a transport key.The scrambled audio/video stream is organized in packets having a packet header and a payload section. The seed data is filtered by the receiver and passed to the security module for decryption and processing in order to generate a key stream including the packet header previously extracted from the received packet. The key stream is generated in such a way that its bandwidth is equivalent or larger than the bandwidth of the input scrambled audio/video data transport stream. The processor chip set applies a mixing function to the key stream and to the packet payload identified by the packet header returned by the security module and obtains a descrambled payload packet. The packet header is then added to the descrambled payload packet before outputting from the chip set towards a MPEG decompression module.