In connection with the password-based key CAS conditional access, this article introduces the basic mechanism of the system, and presents the data packet structure of Entitle Control System (ECM) and Entitle Manage Message (EMM).

• 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;