Security of Cyber-Physical Systems

This talk addresses in the main the problem of secure control of networked cyber-physical systems, and, title notwithstanding, a digression into mm-wave networks that have quickly become of great topical interest since the FCC release of 10.85 GHz of spectrum in July 2016. We consider physical plants controlled by multiple actuators and sensors communicating over a network, where some sensors and actuators could be “malicious.” A malicious sensor may not report the measurement that it ob- serves truthfully, while a malicious actuator may not apply actuation signals in accordance with the designed control policy. In the first segment of the talk, we introduce the notions of securable and unsecurable subspaces of a linear dynamical system, which have important operational meanings in the context of secure control. These subspaces may be regarded as analogs of the controllable and unobservable subspaces reexamined in an era where there is intense interest in cybersecurity of control systems.

In the second segment of the talk, we address the problem of detecting malicious sensors in a system. We propose a general technique, called “Dynamic Watermarking,” by which honest actuators in the system can detect the actions of malicious sensors, and disable closed-loop control based on their information.

We then digress to Medium Access Control (MAC) design for mm-wave wireless networks. The high directionality of mm-wave nodes introduces the problem of deafness, which renders conventional MAC protocols such as CSMA/CA ineffective in orchestrating the medium access. We outline some preliminary results on TrackMAC, a MAC protocol designed for mm-wave wireless networks, and show how it achieves efficient medium access (this talk is based on several joint works with Prof. P. R. Kumar, Woo-Hyun Ko, and Simon Yau of Texas A&M University, and Dr. Amal Ekbal, Dr. Ahsan Aziz, and Dr. Nikhil Kundargi of National Instruments).