条件接收系统授权信息的分析

Analysis of Authorization Information of Conditional Access System

数字电视条件接收系统（Conditional Access System，CAS）是广电部门运行服务平台的核心，它保障了节目提供商、网络运营商和用户3方的利益。针对基于密钥的条件接收（Conditional Access，CA）系统，简述条件接收系统基本工作原理、分析条件接收系统中授权控制信息（Entitle Control Message，ECM）和授权管理信息（Entitle Manage Message，EMM）数据包的结构；通过讨论EMM数据量的问题，分析条件接收系统授权方式。

Digital TV Conditional Access System （CAS） is the core of the service platform in the broadcasting and TV business. It benefits the program vendors, the network vendors and the customers. In connection with the password-based key CAS conditional aeeess, this article introduces the basle mechanism of the system, and presents the data packet structure of Entitle Control System （ECM） and Entitle Manage Message （EMM）. Also, the authorization way of CAS is analyzed by discussing EMM data quality.