Minimizing Side-Channel Attack Vulnerability via Schedule Randomization

Control systems can be vulnerable to security threats where an attacker gathers information about the execution of the system. In particular, side-channel attacks exploit the predictability of real-time control systems and of their schedules. To counteract their action, a scheduler can randomize the temporal execution of tasks and limit the amount of information the attacker can gather. Schedule randomization is aimed at achieving the highest possible schedule diversity (measured using the upper-approximated entropy) during the real-time execution of the controller. This paper investigates fundamental limitations of schedule randomization for a generic taskset. The constructed schedule set has minimal size and achieves the highest possible upper-approximated entropy.