DTV Conditional Access System And Implementation In STB

Broadcasting has been in the digital era. With the full digital technology, we will make video & audio more vivid and make the best of resource of frequence, meanwhile, we could appreciate rich and colorful services. During the era of analog TV, adervatisement is the main income of TV station. But now, era of digital TV, there are more means to make profit, such as subscribing specific services. In order to let viewer pay for the service they want to watch, a conditional access system is necessary.The history of CAS and characteristic of technology and the necessary of CAS in digital TV are given in this paper. The core technology encryption algorithm is descripted in detail. The security of CAS is studied based on the description of algorithm, various attacking the CAS would suffer from are put forward. At the same time, the paper detaily gives the principle of CAS and system structure and makes a contrast between Simulcrypt and Multicrypt. It points that Multicrypt will be the trend of CAS. A embedded OS pSOS is deeply studied, specialy on attemper mechanisim based on priority and time splice. A method is given how to put a practical CAS into practice in Cable STB, it includes the development of driver and interface between application and driver. Beside, integration and test of system are descripted. Last, a summery of the project is given and prospect of CAS is shown.The project implements all function of a commercial CAS in STB base on the plat of LSI SC2000 and pSOS. The system runs stably with friendly user interface after the strongly test, which is our expection.