Abstract:
This thesis presents ล television scrambling system. The system consists of two parts: the scrambling and the conditional access. The scrambling utilizes random video inversion and total sync removal methods. For conditional access, a control word IS used to generate a sequence of pseudo random numbers, which are used as scrambling parameters. Descrambling requires the control word, which is sent in an encrypted form to the receivers. There are a number of keys used in the encrypting process. By managing these keys, it is possible to provide the conditional access, e.g. controlling individual view, dividing members into groups and giving a pay-per-view service.