Key Technologies Of The Digital Tv Conditional Access System

With the rapid development of DTV (digital television), analog TV will be replaced gradually. Users' requirement for multimedia services will increase quickly. As a novel data transmission technology,digital video broadcasting System is being used widely because of its high speed and flexibility. However, without guaranteeing of condition access, new business will not become reality because no one is willing to make an investment without repayment.Digital television conditional access system (CAS) guarantees that only those entitled customers can watch program. The main idea is as follow: CAS scrambles service streams at head-end with pseudorandom sequence that control words produce. At the same time, Control words are transmitted to terminal for entitled terminal to descramble and entitled users to watch program.CAS is the core guarantee system, which is concerned with the security of the whole television network. There are relatively mature CAS technologies overseas, yet all of them are in secret. It's the most important and challenging work that we open up our own secure and efficient CAS. Some manufactures have developed a few practicable CAS in nearly years. Most of these CAS is unilateral transmission with some special and simple functions ,because DTV standard and criterion is not confirmed in our country, especially machine-card- separated management is in passionate discussion.The timetable of DTV popularization is as follow: first, the cable's DTV will be developed in 2003.Second, the users of the cable's DTV will exceed 30 million doors. Third, analog television will be discarded in 2015. The demand of CAS that is adapt to DTV development become more and more urgent for this timetable was confirmed.This dissertation introduces some digital TV CAS key technologies,such as criteria on MPEG-2 and DVB, encryption and de-encryption etc. Analyzing the weakness of popularized CAS technologies in the market, it put forward a solution. I have finished the design and debugging of CAS' head–end module and Subscriber Management System after analyzing theories, survey and simulation. Though the system is available for special users too, it has its features. I wish that it can be contributed to our country's digital television CAS' development.