【作者】 付岩；

【导师】 王华奎；

【作者基本信息】 太原理工大学 ， 信号与信息处理， 2003， 硕士

【摘要】 数字视频广播(DVB)系统不但能够提供数字化广播节目，而且能够提供大量的增值服务，给传统的广播行业带来了新的大发展机会。条件接收系统(CAS)是DVB系统实现增值的核心，能够提供有效的系统管理和用户控制，它集多种先进技术于一身，诸如：系统调度管理、网络技术、数字压缩编码、加解扰算法、加解密算法、复用器技术、调制解调技术、机顶盒技术、智能卡技术等，同时也涉及到用户管理、节目管理、收费管理等数据库应用技术。 CAS在国外起步较早，现在已有多家知名CAS提供商，在全世界范围内运营，提供比较完善的服务。随着数字化时代的到来，目前我国也出现了多家CAS提供商，个别CAS在国内某些有线电视台也已经开始运营，但国内CAS还需要经过很长一段时间的检验才能够逐渐发展完备和成熟。 本文在首先对CAS的各个方面做简明和深入综述的基础上，主要完成了以下三部分工作： 第一部分讨论了密钥分配管理问题。针对二层和三层密钥模型存在的弊端，本文描述了适用于百万用户大系统的四层密钥模型以及对系统内用户分组的方案。该方案不但降低了密钥分配复杂度，而且实现的系统的动态管理。性能分析表明，证明该模型可以有效用于提供频道预订(PPC)和按次付费(PPV)业务的DVB系统。 第二部分介绍了CA子系统在机顶盒(STB)中的实现。根据目前国内的应用水平，本文采用嵌入式安全模块结构，结合一些实际应用，提出了CA子系统的软、硬件设计方案，完成了CA数据解码、智能卡通信接口以及通信流程设计。该方案既实现了安全性，又保证了低成本实现，对实际应用有一定的指导价值。 第三部分讨论了CAS的互操作性实现。这部分首先介绍了欧洲DVB组织提出的实现CAS互操作性的通用接口(CI)硬件实现方案，基于同样的思想，本文描述了将互操作软件下载到STB中来实现CA-STB互操作性的解决方案。该方案不仅可以提供完整的互操作性，而且可以较容易应用于未太原理工大学硕士学位论文来的STB，并且仅仅需要对目前的CAS做一些细微的改变。更多还原

【Abstract】 Digital video broadcasting system, which can provide not only many digital programs, but also variety of services, brings valuable opportunities to the traditional broadcast industry. Conditional access system is the key to realize the increment of the DVB system and provides effective system management and subscriber control. It covers many advanced techniques such as system-scheduling management, network, digital coding & decoding, scrambling & descrambling, encrypting & decrypting, multiplexing, modulating & demodulating, set-top box, smart card and some practical database techniques, for example program management, subscriber management and charging management.CAS appeared firstly in western countries, and at present, there are many mature CAS providers who provide complete solutions with various services throughout the world. Facing the impending of the digitalized era, some CAS providers have appeared in China and put some of their products into practical implementation, all of which are immature and should be checked by time.This paper is based on the concise and deep-going survey of CAS, and finished the following three parts:In the first part, the key distribution management of CAS is discussed. Aiming at the drawbacks of variant levels of key hierarchy, this paper describes two four-level schemes of key hierarchy in CAS. Therefore, we analyze the performance of the complete scheme, which shows that this scheme is efficient and suitable for DVB system that provides both PPC and PPV services.Besides, the described complete scheme is also flexible for dynamicmanagement.In the second part, CA subsystem is implemented in the set-top box. We adopt the embedded security module, and introduce a complete solution for the implementation of CA subsystem, and finally finish decoding relevant CA data, interfacing to smart card and communicating between the host and the smart card. The proposed solution, which ensures both security and lowcost, can be used to instruct the practical application.In the third part, the interoperability between different CASs is discussed. DVB common hardware interface is introduced firstly, then an interoperable software solution is described based on the thought of seperating the proprietary parts of CASs. It provides full CA-STB interoperability. Furthermore, it can be introduced relatively easily into future STBs and will require only minimal changes in current CASs.更多还原