【作者】 郑猛；

【导师】 郑世宝；

【作者基本信息】 上海交通大学 ， 信号与信息处理， 2007， 博士

【摘要】 众所周知,从模拟电视到数字电视的过渡是我国广播电视行业必然的发展趋势。模拟电视用户可以购买新的数字电视接收机或机顶盒接收数字电视,其中机顶盒是多数老百姓的主要选择。条件接收系统作为数字电视技术中的核心设备,通过对所播出的节目进行加扰,管理和控制用户收视的权限,保障了节目供应商和运营商的利益,也为发展新的增值服务提供了一个安全可控的综合管理业务平台。然而,目前国内开通数字电视试用方案的“机顶盒”和“条件接收系统”机卡绑定产品体系结构,形成了运营商选择条件接收系统产品、终端制造商接运营商订单为其定制生产、运营商垄断销售机顶盒的畸形产业格局。针对机卡绑定的种种弊端,信息产业部及时提出“机卡分离”的产业技术政策,并作为“电子发展基金”项目招标,支持机卡分离产品的研究开发,意在为机顶盒制造商解决规模生产的外部瓶颈和给机顶盒用户带来实惠,梳通广电运营商、家电企业和CA厂商之间的产业链关系。本文结合作者参与信产部电子发展基金项目“智能卡机卡分离系统”的研发工作,全面研究了智能卡机卡分离条件接收系统解决方案中的关键技术问题,全文的内容安排和研究成果为:首先,分析数字电视条件接收系统的基本原理和核心技术。从现有条件接收系统的工作原理、一般实现架构、接收端条件接收系统内核功能及工作机制、条件接收系统的同步技术几个方面剖析条件接收系统,实现了一套条件接收前端系统的软件仿真试验平台。基于以上对CA的剖析以及与CA厂商的实际讨论结果,明确定义智能卡机卡分离的前提条件和衡量标准,为智能卡机卡分离方案奠定技术上的可行性基础。其次,基于实现的条件接收软件仿真平台,对条件接收技术的用户授权管理和利用MPEG2编码特性的加扰技术进行研究。通过对已有的密钥分配机制进行学习分析,基于D.Naor满二叉树的“完备子集法”和“子集差分法”两种子集覆盖算法,提出一种改进的条件接收系统四级密钥分配机制,新机制有效地减少密钥更新需要占用的数据带宽。进一步对DVB、ATSC、IPCA加扰算法的实现进行分析,着重研究利用MPEG2视频压缩编码特性的透明加扰算法,提出一种支持码率下变换的透明加扰系统结构,并给出参考算法对透明加扰效果进行主客观比较。接着,详细阐明智能卡机卡分离总体设计方案和系统架构,并对所有关键技术的应用背景、研究内容进行详细论述,智能卡机卡分离的关键技术具体包括机卡分离通信协议、虚拟消息滤波机制、机卡认证机制和安全通道机制。针对机卡分离插件的安全机制,提出了基于“离散对数机制”和“基于椭圆曲线”的两套完整的安全协议实现机卡认证、安全通道和机卡配对的功能,并对它们进行了安全分析。最后,描述了智能卡机卡分离接收机和智能卡的实现;为更加充分发挥机卡分离对我国数字电视产业发展的推动作用和运营商的实际市场需求,结合目前广电部门推行的中央地方两级CA模式,提出“多服务供应商+单一网络运营商+一张机卡分离智能卡”的新型业务模式并给出实现方案。综上所述,智能卡机卡分离方案是一种新的“一卡”通用条件接收系统解决方案,与现有的私有智能卡条件接收子系统相比,它在开放型、安全性和易升级维护性上具有明显的优势。同时,它的成本也大大低于PC卡条件接收子系统使用的PC卡费用。对机顶盒制造商,智能卡机卡分离解决了因为一款机顶盒通常只绑定一个CA系统造成的生产瓶颈,制造商大量生产基本功能的机顶盒产品,而不需要获得CA公司的授权。对运营商而言,一个明显的好处就是它可以较方便地更换加密付费电视采用的CA系统,或者便利地升级已使用的CA系统,这些完全在他的掌握之中。广大消费者可以受益于机顶盒大规模生产,可以在可接收的价格范围内买自己喜欢品牌的机顶盒。同时,用户可以更换自己的付费电视供应商,代价至多就是购买一张新的智能卡。对CA公司来说,智能卡机卡分离实现的“一卡”通用CA系统以更低的成本获得与CI模块相同的易替换性。同时,新方案的开放性和可交互操作性可使CA公司的产品在市场上更具有竞争力。更多还原

【Abstract】 As is known to all, the conversion from analog TV to Digital TV is the inexorable trend. Analog TV users can either by new digital televisions or by set top boxes to watch digital programs, while the STB is a preferred choose of the masses. Being a kernel equipment of DTV technology, Conditional Access can manage and control the customers’entitlements, guarantee the interests of service providers and network operator, and set up a safe platform of providing new services by encrypting the programs. However, the current experimental operating of DTV is a bundling mode of the STB and the smart card, which leads to an abnormal industrial structure that the cable network operator choose a conditional access system, the STB manufacturer have STBs custom-made for one operator, and the operator monopolize the sell of STBs.To solve the disadvantages of the bundled mode, the ministry of information industry brings up the“Conditional Access functional separation”as an industrial policy, and calls for bid as a project supported by“Electronic Development Fund”in order to encourage the research and development. The application of CA functional separation are expected to remove the bottleneck of STB mass-production for manufacturer, to benefit the customers, and to comb up the industrial chain among CATV operators, DTV manufactures and CA system providers.Based on the work of the actual research and development, the dissertation presents all the key technologies of the“Smart-card-based CA functional separation”. It is arranged as: Firstly, the principles and kernel technology of conditional access are analyzed. The conditional access technology is studied from related CA working mechanism, common structure, CA kernel structure and working mechanism on the receiver side, and the synchronization. A software simulation of head-end CA system is implemented. The all-round study of CA technologies builds a feasibility foundation of smart-card-based CA functional separation. Secondly, based on the implemented SW CA system platform, there are some research on key distribution and MPEG2 scrambling technology. Based on D.Naor’s complete subtree algorithm and subset difference algorithm for full binary tree, a new four-level key management scheme is presented which can dynamically entitle the customers and greatly save the bandwidth usage.Moreover, with the analysis of DVB, ATSC and IPCA scrambling algorithm, a mechanism is illustrated which combines with the MPEG2 encoding characteristics and supports down-bit-rate transparent scrambling, and the reference algorithms are used to show the subjective and objective effects.Subsequently, the overall design and system architecture of smart-card-based CA functional separation is proposed. All the key technologies are described in application background, concrete content, and implementation method. The key technologies include the communication protocol, the virtual CA message filtering, the identification method, and the safety channel function. To implement the safety module, a DLP-based security protocol and an ECC-based security protocol are presented to carry out the smart-card authentication, safety channel and STB-smartcard pairing, which are followed by security analysis.Consequently, after the introduction of the CA-functional-separation receiver and smart card implementation, a new business model-“multi-service providers + single network operator + one CA functional separation card”is proposed. The implementation scheme for the new mode is presented based on the CA functional separation platform, and it can bring smart-card-based CA functional separation into full play and with the combination of the current two-level CA mode. We proposed a“one card”CASS solution which is more open, secure, and easy to update compared with the existing proprietary smart-card-based CASS. Meanwhile, the cost is much less than a CI PCMCIA module.The market benefits from the proposed system at least from the following four aspects. For the STB manufacturers, the manufacturing bottleneck caused by porting different kinds of proprietary CASS is broken. Manufacturers are able to mass-produce standard decoders with no need for permission from any CA system vendors.For the service providers, they can easily switch from one CA system to another and update their systems. All of these will be entirely under their control. For customers, they can buy STBs of whatever brands they like in a more affordable manner, or change their service provider at the cost of no more than a new smart card.For the CA vendors, the“one card”CASS solution saves the cost comparing to a CI PC card. The openness and high interoperability of the new solution makes a CA vendor’s product more competitive in the market.更多还原