The Principle And Realization Of Digital Television Broadcasting Conditional Access System

With the rapid development of information technology, digital television services now begin to be realized. Digital television broadcast platform gives the possibility of much more attractive services,such as HDTV,interactive television and interner access. But this will not become reality without the surport of another technology-conditional access system.Conditional Access System guarantee that only those entitled costomer can access services. CAS scrambles service streams with control word at head-end and broadcast the encrypted control word together with services streams. It is CAS's responsibility to make sure only entitled terminal can decrypt the control word and descramble service streams.This paper mainly focuses on the design and implement of conditional access systen.Chapter 1 gives a brief description of digital television broadcase and conditional access system.Chapter 2 describes all aspects of conditional access systen in DVB architecture including struct, principium, encrypt arithmetic, DVB simulcrypt and common interface. Then discusses the security and protection of CAS.Chapter 3 describes detailedly an advanced solution of conditional access system, including the details of scramble/descramble and encrypt/decrypt.Chapter 4 describes the implement of manage system which is closely related to CAS.