Scrambling and key distribution scheme for digital television

The scrambling scheme is a part of the conditional access system (CAS) that is used to prevent unauthorized access to Pay-TV systems. In this paper, we propose a new scrambling scheme and key distribution scheme. The scrambling scheme is used in conjunction with ordinary encryption techniques, for protecting the digital video streams from unauthorized viewing. A hash function and a pseudo-random number generator are used to prepare the video stream before being encrypted. The proposed scheme helps reduce computational time and complexity while providing the same level of security as encrypting the entire video stream. In addition, the proposed secure key distribution scheme can be used with any scrambling scheme e.g. with our scrambling scheme. By using the Chinese Remainder Theorem (CRT) for distributing parameters in the scrambling process, the security of the scheme can be increased. Moreover, our scheme can prevent two common problems, namely smart card cloning and McCormac Hack.