The Design And Realization Of Conditional Access Set-Top-Box Based On Multicrypt Technique

The essential intention of Conditional Access System (CAS) is to achieve pay-TV of the digital broadcast system by means of subscriber management and authorization control. So CAS is the key technology to realize the pay-TV and interact-TV. CAS can bring profits to the service operators and thus the service operators will provide more kinds of contents with better qualities. Digital Video Broadcasting organization brings forward the solution based on simulcrypt and multicrypt technique for making CAS as an open system and solving compatibility and fair competition between different CAS. In conclusion, multicrypt technique with the character of open and compatibility is the direction of future CAS. After researching the multicrypt technique of conditional access deeply, author design a conditional access satellite Set-Top-Box (STB) according to market requirement based on DVB-S, DVB-CI and MPEG-2 standards. The paper firstly introduces the correlative standards and key technique, and then, thesis describes the standard structure of STB and constitution of multicrypt CA STB in terms of the design model of host and module separately. Next, author introduces the chosen satellite set-top-box R&D scheme, which has powerful function, high price performance ratio and was adopted in the domestic markets recently. Subsequently, the paper analyses the scheme's software and hardware system structure on the whole, and gives emphasis to introduce the software architecture based on independent layers and the application software development on the basis of task. The paper also explains the inter-action relationship among tasks through the essential function of satellite STB, and shows the system's integrated development environment and the way of software debug. In the following content, author designs Common Interface module's software and hardware after making a study of CA Multicrypt technique and DVB-CI standard, and mainly introduces the realization method of CI Command Interface protocol stack, which has important reference meaning on developing the communication protocol in other Embedded Operation System; then the paper presents how to get the PSI information using STB's Section Filter module and how to descramble the scrambled TV programs through the communication between host and CA Module with Command Interface protocol stack. In the end of this paper, it gives out the test result and analyses the disadvantages and has a view of the development's trend of research domain.