Theory and implementation of dynamic watermarking for cybersecurity of advanced transportation systems

We consider a prototypical intelligent transportation system with a control law that is specifically designed to avoid collisions. We experimentally demonstrate that, nevertheless, an attack on a position sensor can result in collisions between vehicles. This is a consequence of the feeding of malicious sensor measurements to the controller and the collision avoidance module built into the system. This is an instance of the broader concern of cybersecurity vulnerabilities opened up by the increasing integration of critical physical infrastructures with the cyber system. We consider a solution based on “dynamic watermarking” of signals to detect and stop such attacks on cyber-physical systems. We show how dynamic watermarking can handle nonlinearities arising in vehicular models. We then experimentally demonstrate that employing this nonlinear extension indeed restores the property of collision freedom even in the presence of attacks.