Physical Layer Security for Channels with State and Active Eavesdroppers (PLAY SCATE)

如今，作为对密码技术的补充，信息理论的安全方法被广泛讨论。这些方法通过考虑噪声信道的属性在物理层共同建立可靠的通信和数据机密性。最近，这一领域的研究引起了相当大的关注，因为它为实现无条件安全和将安全通信嵌入到无线网络中提供了一种很有前途的方法。在实际系统中，由于无线信道的性质和估计/反馈的不准确性，CSI会受到限制，在设计对自然故障具有弹性和对恶意攻击具有鲁棒性的无线系统时，正确的系统理论模型分别是复合信道和任意变化的信道。如果信道的状态在一个码字的持续时间内是恒定的，则CC模型适用。如果每个信道使用受到不同信道状态的影响，则AVC模型是合适的。本项目的目标是了解复合窃听信道和任意变化的具有主动窃听者的窃听信道的基本属性，这些监听者自愿影响信道状态。在系统设计中，重要的是要考虑对传输节点和攻击节点的约束，以正确地建模它们的可能性。在文献中，AVWCS的保密能力的表征依赖于AhlSwede的方法。它们不能直接在输入和攻击者约束下应用，特别是确定二分法在约束下是否成立，以及对于哪些约束，所产生的保密容量为零是有趣的。预计由于主动攻击，半确定性编码将受到对称性的影响。为了实现设计弹性无线系统的目标，需要对对策进行详细描述。此外，在信道是CC或AVC的情况下，应使用信道模型来研究物理层密钥协商，并将导出最优传输策略。此外，《化学武器公约》和《禁止化学武器公约》的保密能力取决于潜在的不确定性集合。通信系统的性能应该以一种连续的方式依赖于系统参数。这是因为，如果参数的微小变化会导致性能的急剧下降，那么手头的方法很可能不会被使用。事实上，人们感兴趣的是对这种变化具有健壮性的方法，因为不确定性集合的微小变化会导致保密能力的微小变化。这种持续的依赖关系在可能以恶意方式影响系统参数的活跃攻击者的背景下是可取的。该项目将开发基于一般信道模型的信息论方法来模拟对嵌入安全的通信系统的攻击。

Nowadays, information theoretic approaches to security are intensively discussed as a complement to cryptographic techniques. Such approaches jointly establish reliable communication and data confidentiality at the physical layer by taking the properties of the noisy channel into account. Recently, this area of research has drawn considerable attention since it provides a promising approach to achieve unconditional security and to embed secure communication into wireless networks. In practical systems, CSI will be limited due to the nature of the wireless channel and estimation/feedback inaccuracy.In designing wireless systems resilient against failures caused by nature and robust against malicious attacks, the correct system-theoretic model is the compound and the arbitrarily varying channel, respectively. The CC model applies if the state of the channel is constant for the duration of one codeword. The AVC model is suitable if each channel use is affected by a different channel state. This correctly models malicious attacks.The goal of this project is to understand the fundamental properties of compound wiretap channels and arbitrarily varying wiretap channels with active eavesdroppers who voluntarily influence the channel states. For the system design it is important to consider constraints on the transmit as well as attacker nodes to correctly model their possibilities.In the literature, the characterization of the secrecy capacity of AVWCs relies on methods by Ahlswede. They cannot be applied directly under input and attacker constraints.In particular, it is interesting to determine whether the dichotomy holds under constraints, and for which constraints the resulting secrecy capacity is zero. It is expected that semi-deterministic coding will suffer from symmetrizability due to active attacks. A detailed description of countermeasures is required to achieve the goal to design resilient wireless systems. Furthermore, physical layer key agreement, using the channel model, where the channel is either a CC or an AVC, shall be investigated and optimal transmit strategies will be derived. Additionally, the secrecy capacities of the CWC and the AVWC depend on the underlying uncertainty set. The performance of a communication system should depend in a continuous way on the system parameters. This is because if small changes in the parameters were to lead to dramatic losses in performance, the approach at hand would most likely not be used. Indeed, one is interested in approaches that are robust against such variations, in the sense that small variations in the uncertainty set result in small variations in the secrecy capacity. Such a continuous dependency is desirable in the context of active adversaries who can influence the system parameters in a malicious way.The project will develop information theoretic approaches based on general channel models to model attacks on communication systems with embedded security.