Analysis And Implementation Of DVB Common Scrambling Algorithm

With the rapid development of information and digital technology, the television technique also goes through the transformation from analog television to digital television. The conditional Access System, the key technique assuring content copy protection as well as the paid services, has always been paid great attention because it is directly connected with the operation of whole digital television industry chain. Among the conditional Access System, Scrambling Algorithm, basis of system safety, is used to encrypt audio and video data and services information. The Common Scrambling Algorithm is one of the most frequently used Scrambling Algorithm in digital television field all over the world.DVB (Digital Video Broadcast) Common Scrambling Algorithm is specified by the European Telecommunications Standards Institute, for MPEG-2 transportation stream data encryption. During the digital television migration in China, DVB Common Scrambling Algorithm has been totally used for paid services encryption. People have always known little about the details of algorithm and its safety due to the sensitivity of the algorithm design documents.. Therefore, in-depth understanding the design of algorithm is significantly important for evaluating algorithm strength and risk assessment system of digital television.This thesis is mainly about:1. After collecting materials about DVB Common Scrambling Algorithm home and abroad, the paper made deeply study on DVB common Scrambling Algorithm specifications on the basis of understanding of the DVB standards and work experiences, so grasped the process and design details of the algorithm.2. On the basis mastering the algorithm theory, software implementation has been done to DVB common Scrambling Algorithm by using standard C language. The process of implementation was totally in compliance with the software engineering requirements, made requirement analysis, architecture design, details design, and then coding according to the detailed design. Moreover, module tests and integration tests have been made to the algorithm and results was passed.3. According to the performance test result, the paper made in-depth analysis to efficiency of algorithm implementation of each module and conclusion has been given.4. The paper also did analysis, from practical and safety, to DVB common Scrambling Algorithm through "error diffusion", "key length" and "random and periodicity of stream cipher key".Finally, the paper also made forecast for the following topics.