The Research And Implementation Of Head End Of Digital Television Conditional Access System

With the development of the digital television, many new services have been provided to serve people, such as Video-On-Demand, pay-per-view, information-on-demand. Digital television provided a service platform for services and Network Company. The conditional access is the key system of the digital television. It ensures the benefit of consumer, program supply and network company. It guarantee the legal benefit of consumer and supply by encryption technology, good design,strict rule of law .This paper introduces the status , characteristic of conditional access (CA).It is necessary to use CA technology in digital television. It analyses the key technology multilayer encryption algorithm and the security of this system. It introduces the principle of conditional access. Two essential way of conditional access, SimulCrypt, MutiCrpt. This system is composed of head end and terminal end .This paper aim at the design and develop of head end.The main task includes design, develop and test of Entitlement Control Message Generator and Entitlement Management Message. The design and develop of interface of CA system and subscriber manage system. Multilayer encryption is used in CA system to protect data. It is a mature technology and its security is indisputable. This paper researches and analyses DES and RSA algorism in terms of the needs of the capability and security of the system. The application of simulcrypt stack is the key work of the system.The main work of head end system is run on the simulcrypt stack. The exact synchronization is the key point of the system. It affects the performance of CA system. This paper analyses synchronization from system prospect and soft realize, and it make a project to solve this problem. It includes Synchronization between ECM and control words, Synchronization between EMM and service key. It transmits even and odd control words. With even and odd control flag to make the control word perspicuity. It analyses the bandwidth ofconditional access and the realization form of EMM and ECM. This project meets the user's need. In the end, summarize the paper and make prospect of conditional access. This task achieves a commercial conditional access system. It provides full functions and friendly interface to users. It passed the test of the state administration of radio film and television. The system runs stably and achieves the goal.