Managing the security-energy tradeoff in distributed cyber-physical systems

In this paper, we propose a technique that attempts to control energy consumption in distributed cyber-physical systems (CPS) in order to improve the level of security of the system. This is in contrast to most existing methods, where the system is set to use a certain level of authentication at design time, such as basic authentication, certificate-based authentication, or no authentication at all. To this end, we propose a notion of authenticatable task graph, which encodes standard task dependencies and allows for authentication tasks to be intermittently inserted into the computation task graph. The optimization objective here is to maximize the number of authentication tasks as well as peer-authentication, while remaining in the system energy bounds. We propose three offline optimization techniques and one online algorithm, where the system can dynamically manage the tradeoff between energy consumption and the level of security in the presence of uncertainties imposed by the physical environment. Our optimization algorithms are validated by a rich set of simulations as well as a real-world case study on a group of unmanned aerial vehicles (UAVs) that are assigned area search tasks and are required to perform peer-authentication within their battery limits.