The Software Design And Implementation Of STB Conditional Access System

With the rapid development of information technology, set-top boxes have more functions, and are more integrated. In the future course of development, set-top boxes is likely to become the leader in home terminal to complete the connection of TV terminal, network and various other applications. It can be seen that the set-top box has a very large market potential. Currently, as a major providers of television service, radio and television operators can profit by providing users with a variety of fee-based program. In order to protect the interests of operators, only legitimate users can be able to watch the pay program. Based on the needs of radio and television operators, the paper designs a set-top box’s conditional access system, and elaborated the system software implementation and testing validation.This paper introduces the background and significance of the subject conditional access systems, current research, and the main content of this research topic. In the second chapter introduces the basic principles of set-top boxes, as well as set-top box software architecture, key technology study and research, it is to prepare for the design of conditional access systems. The third chapter describes the detailed design of the conditional access system, including the detailed design of the PSI / SI analysis module and the smart card communication module and the ECM / EMM information processing module, and in PSI / SI parsing module, through the data analysis of PAT tables, PMT table, CAT table, we can obtain the PID of ECM / EMM data, through the PID, the ECM / EMM processing module can filter the information of ECM and EMM data. Smart card communication module, the ECM / EMM data is used to communicate with a smart card, to decrypt the SK from the EMM data, and as a key to decrypt the control word CW from the ECM data, and the CW can use to descramble the transport stream, the we can restore the original audio and video data, the decryption process is complete. Any software design, are inevitably need to maintain and update, therefore, in the fourth chapter, describes the detailed design of the online upgrade system, including the detailed design of a new version of the software detection module, online data download module, upgrade information storage module, upgrade information can be detected by the detection of a new version of software modules, and send the information to the STB, the onlie data download module can complete the download, parse, stitching and check and notify of the upgrade data, and send the information to the STB; the upgrade data is written to flash by the upgrade information storage module, and complete the upgrade software online. The fifth chapter describes the system testing of the conditional access systems and online upgrade system, and problem analysis and resolution.This design of conditional access systems, not only achieving the encryption program to watch, but also supporting the software online upgrade.It provided a guarantee for the stability and maintainability of the system.