We investigate a novel approach to resilient distributed optimization with quadratic costs in a Networked Control System prone to exogenous attacks that make agents misbehave. In contrast with commonly adopted filtering strategies, we draw inspiration from a game-theoretic formulation of the consensus problem and argue that adding competition to the mix can improve resilience in the presence of malicious agents. Our intuition is corroborated by analytical and numerical results showing that (i) our strategy reveals a nontrivial performance trade-off between full collaboration and full competition, and (ii) such competition-based approach can outperform state-of-the-art algorithms based on Mean Subsequence Reduced. Finally, we study impact of communication topology and connectivity on performance, pointing out insights to robust network design.
I. INTRODUCTIONW ITH great power comes great responsibility, and Networked Control Systems have great power indeed. From smart grids managing energy consumption [1], [2] to sensor networks able to monitor vast areas [3], to fleets of autonomous vehicles for intelligent transportation [4], [5], everyday life depends more and more on control of interacting devices.While this brings numerous benefits, a major drawback is that malicious agents can locally intrude from any point in the system, and cause serious damage at global scale. Recently, Department of Energy secretary stated that enemies of the United States can shut down the U.S. power grid, and it is known that hacking groups around the world have high technological sophistication [6]. Cyberattacks hit Italian health care infrastructures during the COVID-19, disrupting services for weeks [7]. Another concern is accidental failures spreading from single source nodes. Cascading failure damages have notable examples, from electricity blackouts over large areas, to denial of service of web applications. Furthermore, as new frontiers through massively connected devices in Networked Control Systems and the Internet-of-Things are breached, thanks to powerful communication protocols such as 5G and 6G, this problem will only gain in importance.