协作无线通信中的跨层密钥协商设计

According to a recent study by Cisco Systems, small portable devices, e.g. smartphones, will lead the IP traffic growth and will account for up to 70% of the mobile IP traffic by 2017. However, it is impractical to have multiple antennas and highly complex hardware equipped on small mobile terminals due to the size and power constraints. User cooperation and self-organized network is a promising solution for future wireless networking. Cooperative wireless communications has been extensively studied in the communication research community. Because of the complex network structure and the assumptions necessary for the relay nodes, cooperation inevitably introduces severe information security issues. Among information security topics, key generation is one of the most fundamental and also extremely important issues. It is very challenging to design efficient key generation schemes for cooperative wireless networks. Existing work on cooperative key generation relies heavily on channel estimation, which makes it impractical for real world applications. Violation of the classic two-phase frame structure for cooperation further raises compatibility issue with existing wireless cooperation protocols..Maurer suggested that channel uncertainty can be exploited for secret key generation via public discussion. A general framework for key agreement protocol design which contains advantage distillation, information reconciliation and privacy amplification, was proposed. He showed that a positive key rate can be achieved by key agreement even when the eavesdropper has more favorable average channel conditions. Therefore, in this project we consider key agreement for key generation in cooperative wireless systems..Considering the characteristics of relay channels, key agreement will be studied for cooperative wireless systems. We will derive the theoretic key rate bounds and use them to explore efficient key agreement protocol design based on joint optimization of advantage distillation, information reconciliation and privacy amplification. The proposed efficient protocols and algorithms can be used in real world applications of cooperative wireless systems to provide improved security.

研究表明，移动便携设备的发展将主导整个移动互联网业务量的增长，设备间通信(D2D)也已被认为是下一代蜂窝移动通信标准5G必定包含的系统特性。但在智能手机和无线传感器这样的小型移动设备上部署多天线设计来提高数据速率面临诸多现实问题，用户协作与自组织网络是未来无线技术的一个主流方向，协作通信于是成为近年一个研究热点。由于协作无线网络结构复杂性和中继结点多样性，其安全性逐渐成为研究焦点。其中，密钥管理是最基础且极重要的一环，是规模部署时必须面临的技术挑战。近两年学术界开始关注这一课题，但在已发表成果中，协议算法未能根据经典协作时隙结构设计，对信道估计的过度依赖也降低了其实用性。.本课题基于Maurer利用物理信道不确定性协商建立无条件安全密钥的思想，针对协作通信特点设计密钥协商协议。项目首先推导密钥率理论界，再利用物理信道的变化对优势提取、信息调和与保密增强进行联合优化，实现协作通信下无条件安全的密钥协商。研究中将采用基于信道鉴别和用户自激发的两种用户间共有信息生成模式，针对不同通信场景提出相应的解决方案。课题旨在研究高效实用的密钥协商机制，为协作无线网络规模部署提供安全性保障。

协作无线通信技术，是未来无线网络向超密集化、异构化和自组织化演进过程中，很具发展潜力的一项关键物理层技术。该青年基金项目针对无线协作引入的同时面临的信息安全威胁，提出采用物理层安全的方法，对上层密码系统加/解密密钥进行管理，实现协作密钥协商。该技术充分利用了无线信道的随机特性，有效实现密钥在合法通信方之间安全可靠的分配与管理，而物理层安全的信息理论安全特性，确保了该过程中密钥不被非授权方截获。项目首先在前期对单向中继密钥协商的研究基础上，对双向中继放大转发协作通信系统保密传输和密钥协商技术进行了研究，提出了三阶段双向中继协议下的安全最优化模拟网络编码方案，其保密传输性能优且对中继位置不敏感，对中继位置优化的需求也相应降低，更适合低复杂度边缘网络场景的应用。对多天线协作保密通信系统，研究了其利用主动物理层安全策略的同时，为低功耗小型无线设备进行无线输能的系统，着重对系统在CSI误差和相位噪声影响下鲁棒性进行了研究，提出了系统的低复杂度鲁棒性设计，显著提升了安全传输-无线输能联合系统的有效性。项目还将基于信道鉴别的密钥协商扩展至非常规无线信道环境——空地自由空间光通信系统，证明了空地自由空间无线光通信系统大气湍流信道的闪烁互易特性，据此为该系统设计了基于信道鉴别的密钥协商协议，并证明了该策略下密钥率由信道统计特性类型决定，受信道湍流强度影响较小。此外，对密集化、异构化和自组织化场景下的协作物理层保密传输、无线资源管理等问题进行了延伸探索。为项目负责人下阶段基于物理层安全的5G边缘网络安全技术研究奠定了良好的基础。

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