Physical-layer encryption for enhanced cyber-physical security

Abstract

Communication in wide-area measurement/control systems (WAM/CS) presents simultaneous challenges of achieving low latency, high security, and sufficient data throughputs to meet the overall quality of service requirements. High-value and timecritical information such as that indicating transient instability or attacks on the cyber-physical infrastructure must be delivered to their destination within 5-20 ms of identification [1], eliminating many of the existing commercial communications solutions that employ a traditional net-centric ISO stack-based architecture. This paper focuses on a physical-layer wireless communications technology capable of supporting real-time protection, detection, and reaction processes within the WAM/CS via physical-layer encryption. This PHY-layer encryption adapts a maximum entropy digital chaotic spread spectrum waveform originally developed for secure military communications [2] by employing the underlying spreading sequence as a private key cryptosystem, thus avoiding latencies derived from MAC-layer framing or cryptographic block algorithms. The proposed approach delivers latencies on the order of 500µs per node, allowing significant flexibility in wireless network topology. We present the proposed PHY-layer encryption system in the context of communicating an a monitored "event," evaluate its behavior against the traditional IA objectives, and also consider its integration with related communications techniques to demonstrate its utility as a building block for enhancing cyber-physical security.