Method and system for secure processing a stream of encrypted digital audio/video data

摘要

Method and system to prevent control words sharing. The system comprises a receiver capable of processing a digital data stream. The receiver, having a video descrambler device, is coupled to a primary and secondary secure device. The digital data stream comprises video content data scrambled by a first algorithm using a control word, audio content data encrypted with a secret second algorithm using a system key, and encrypted control messages comprising the control word. The primary secure device decrypts the control message and obtains the control word. The video descrambler device uses this control word to descramble the video content data. The secondary secure device comprises a decryption device which decrypts the encrypted audio content data and a watermarking module configured to add a watermark to the decrypted audio content data and return watermarked decrypted audio content data to the receiver.