基于物理层技术和网络编码的空天信息安全传输机理研究

The space information network (SIN) is of critical importance in both national defense industry and national economy. With an unprecedented amount of sensitive data being transferred over SIN, security has become a primary concern in the applications of civilian and military satellite communications. Particularly, due to the shared wireless medium, highly dynamic network topology, unstable network connectivity, and stringent network resources, SIN is vulnerable to be eavesdropped and susceptible to attacks. As such, the unique characteristics of SIN has imposed a number of nontrivial challenges to the conventional security design. .In this project, based on the information-theoretic secrecy model developed by C. E. Shannon, we consider the physical-layer security design of satellite-ground link and inter-satellite link, respectively. Particularly, for satellite-ground transmissions, thanks to the reciprocity and uniqueness of the fast time-varying fading channel, with compressed sensing based channel estimation, we expand the bit error rate difference between the main channel and the wiretap channel by jointly utilizing the channel state information and the LDPC codes. Further, with cooperative relays, we increase the signal-to-noise ratio difference between the main channel and the wiretap channel by generating artificial noise at the eavesdroppers. Based on the above proposed strategies, the performance of secure transmissions in satellite-ground links is thereby improved. For inter-satellite transmissions, network coding is applied by jointly considering the network protocols, transmission efficiency and transmission security. Particularly, with network coding aware protocol, homomorphic hashing algorithm, and variable-step auxiliary information check, the confidentiality and integrity of delivering messages in inter-satellite links can be effectively guaranteed, which thus improves the performance of secure transmissions in inter-satellite links..In conclusion, this project aims to provide a novel analytical framework for physical-layer security in SIN. It is hoped that the achievements of our research will be of great benefits to the practical design of SIN.

空天信息网络在国民经济和国防工业等相关领域发挥着越来越重要的作用，信道开放性、拓扑高动态、非持续连通、资源受限等特点，对现有安全体制提出严峻挑战。 .本项目以香农的安全模型为基础，基于空天信息系统的分层结构，分别从星地通信和空间段网络传输两个层次保障空天信息安全传输，在星地通信中，利用通信空时唯一性、短时互易性和快速时变性，在压缩感知信道估计的基础上，采用信道状态信息与LDPC编码相结合，扩大主信道和窃听信道误码率差值，采用协作技术，通过不同信道模型中差异化转发和加扰，扩大主信道和窃听信道信噪比的差值，提高安全容量；在空间段采用与组网协议相结合的网络编码方法，构建效率与安全兼顾组网指标体系，研究编码感知组网协议，通过网络编码混合数据，并结合同态哈希与可变步长辅助信息校验，提高信息传输机密性和完整性。.项目研究成果为空天信息安全保障提供一种新的思路，为实现信息论安全提供技术手段和理论基础。

空天信息网络是以空间平台为载体，实时获取、传输和处理空天信息的网络系统，在国民经济和军事领域发挥着越来越重要的作用。.大时空尺度分布及无线信道的开放特性，使得网络无防御边界，截获、窃听威胁无时不在、无处不在；而空天网络高动态、非持续连通、资源受限等特点，对现有安全体制提出了严峻挑战。.本项目以香农的安全模型为基础，分别从一跳通信和网络传输两个层次保障空天信息安全，在一跳通信中，采用物理层安全技术，利用无线通信的空时唯一性、短时互易性和快速时变性，在信道估计的基础上，通过差错控制编码、协作转发和加扰等物理层方法的应用，提高信息机密性；.提出了基于压缩感知的信道估计算法，根据信号间互相关性构建联合稀疏模型，兼顾压缩效率和重建精度，实现效率和精度的有效折中、协同提高。.提出了一种基于预测的协作频谱感知算法，利用频谱状态在相邻时隙和相邻频段之间的相关性，采用LSTM网络对频谱进行预测，并通过数据融合完成多认知用户协作提高感知精度。.提出了基于多元RC-LDPC(Rate Compatible Low Density Parity Check Code)的星地信息安全传输方案。.提出协作转发与协作加扰相结合的空天信息安全传输方法。采用协作中继技术获得协作分集增益，有效对抗各种信道衰落，进而提高通信系统主信道的信道质量。采用零空间人工噪声与随机加权技术相结合，人工干扰恶意窃听节点对保密信息的窃听。.在网络层次，采用与组网协议相结合的网络编码方法，构建效率与安全兼顾的组网指标体系，设计编码感知的组网协议，通过网络编码混合数据，并针对编码系统中伪造、篡改等行为造成的拜占庭攻击，提出同态哈希与可变步长辅助信息校验的检测方法，提高信息在网络传输中的安全性。.通过仿真和演示验证系统对项目提出的算法进行验证，证明了算法的有效性和对空天应用环境的适应性。