CIF: Small: Alignment for Secrecy: One-Time-Pads in the Air without Keys

在当今的通信网络中，大多数数据流经无线链路，而无线链路特别容易受到窃听攻击。虽然目前可用的密码算法提供了针对计算有限的窃听者的有用保护，但攻击者不断增长的计算能力需要提供更强大形式的安全保证的技术。信息论物理层安全提供了无条件的安全保证，即使对计算上无限的对手也是有效的。该研究的目标是提出信息论物理层安全，以解决用户行为不当、用户利益冲突、缺乏完整的网络状态信息等实际问题，并设计出实用的代码。在将信息论物理层安全应用于多用户无线信道中，对齐成为实现网络最大可能安全自由度的有力工具。出于安全目的的最佳对准可以被解释为空中的一次一密通信的形式，而不需要显式地交换密钥；安全是从物理信道中的随机性和用户的合作意愿引导的。这项研究的目标是开发技术，使这种安全的对准方案对用户的不当行为和缺乏信道状态信息更加健壮；通过连接到极坐标编码来开发显式编码来更实用；以及更广泛地适用于具有多天线节点的现代无线网络。具体地说，本研究调查了以下情况：1)不遵循商定的最佳协议的偏离用户；2)对抗具有冲突利益的助手和自私用户；3)由于使用多个天线而产生的矢量信道以及相关的信道状态信息问题；以及4)使用极性码以及相关的极对准和信号对齐的显式码设计。

In today's communication networks, most data flow through wireless links which are particularly vulnerable to eavesdropping attacks. While currently available cryptographic algorithms provide useful protection against computationally limited eavesdroppers, the ever-increasing computational power of adversaries necessitates techniques that provide stronger forms of security guarantees. Information-theoretic physical layer security provides unconditional security guarantees that are valid even against computationally unlimited adversaries. The goal of this research is to advance information-theoretic physical layer security to address practical issues arising from user misbehavior, conflicting user interests, lack of complete network state information; and to devise practically implementable codes.In the application of information-theoretic physical layer security to multi-user wireless channels, alignment emerges as a powerful tool to achieve the maximum possible secure degrees of freedom for the network. Optimal alignment for the purposes of security may be interpreted as a form of one-time-pad communication in the air with no need for explicit exchange of keys; security is bootstrapped from the randomness in the physical channel and from the willingness of the users to cooperate. The goal of this research is to develop techniques to make such secure alignment schemes more robust to user misbehavior and to the lack of channel state information; more practical by making connections to polar coding to develop explicit codes; and more widely applicable to modern wireless networks with multi-antenna nodes. Specifically, this research investigates the cases of 1) deviating users who do not follow agreed-upon optimum protocols; 2) combating helpers and selfish users who have conflicting interests; 3) vector channels arising from use of multiple antennas and the associated channel state information issues; and 4) explicit code design using polar codes and relating polar alignment and signal alignment.