富安全模型下的时间式网络隐信道理论与方法研究

As existing network covert timing channels always utilize cumulative distribution function of inter-packet delay (IPD) sequence to modulate secret message while discarding high-order statistics of IPD sequence completely, which results in the poor resistance to the state-of-the-art covert timing channel detection methods, the research on network covert timing channels maintaining multi-order timing characteristics is significant and important. Based on rich security model of IPD sequence of network traffic, the project concentrates on cover-constraint network covert timing channels, and studies corresponding secure transmission law. With matrix embedding framework and IPD characteristics, the project studies network covert timing channels based on dither matrix modulation utilizing source power expanding and dither modulation. With the duality between Wyner-Ziv source coding and information embedding, the project studies network covert timing channels based on nested lattice quantization. Last, based a family of low-density lattice codes with linear decoding complexity, the project studies the lattice construction and the syndrome-based embedding framework. The project can enrich the theoretical intension of network covert timing channels, and can provide the technical support for high secure covert communication implemented in real networks.

当前时间式网络隐信道普遍依赖载体数据流的包间时延序列（简称时序）累计分布函数来调制秘密信息，难以保留时序的高阶统计特性从而无法抵御先进的隐信道检测手段，因此迫切需要对可保持时序多阶统计特征的时间式网络隐信道展开研究。本课题在建立数据流时序富安全模型的基础上，以载体流约束型时间式网络隐信道为研究对象，研究其安全传输准则。在矩阵嵌入框架上，针对包间时延的特点，采用信源功率扩展和抖动调制策略，研究基于抖动矩阵调制的时间式网络隐信道方法；基于Wyner-Ziv信源编码问题与信息嵌入的对偶性，研究基于嵌套栅格量化的时间式网络隐信道方法；利用具有线性译码复杂度的低密度栅格码，研究其栅格码构造及对应的伴随式嵌入框架。本课题的研究可丰富时间式网络隐信道的理论内涵，为实际互联网环境下高安全的网络隐蔽通信提供技术支撑。

针对现有时间式网络隐信道普遍依赖载体数据流的包间时延序列累计分布函数来调制秘密信息，难以保留高阶统计特性从而无法抵御先进的隐信道检测手段的缺陷，对网络隐信道的多阶统计安全模型进行了研究，并围绕安全性和可靠性进行网络隐信道方案的设计。建立了网络数据流的包间时延序列富安全模型，依据该富安全模型初步提出了时间式网络隐信道的安全传输准则。以载体流约束型时间式网络隐信道为研究对象，重点解决了载体流包间时延序列生成以及时间信道调制方案设计这两个核心问题，从载体流包间时延序列生成、抖动矩阵调制、栅格量化调制等方面对兼具安全性和鲁棒性的时间式网络隐信道方案进行设计。本课题的研究可丰富时间式网络隐信道的理论内涵，为实际互联网环境下高安全的网络隐蔽通信提供技术支撑。