Caphammer: Exploiting Capacitor Vulnerability of Energy Harvesting Systems

An energy harvesting system (EHS) has emerged as an alternative to traditional battery-operated Internet of Things (IoT) devices. An EHS harnesses ambient energy and stores it in a small capacitor, enabling batteryless operation when sufficient energy is available. However, capacitors are susceptible to malicious charging/discharging and over-voltages, which can lead to a loss of capacitance. With the capacitor vulnerability in mind, this article introduces a capacitor hammering attack, simply Caphammer, that can undermine the security of every EHS. The idea is that Caphammer can degrade the capacitance by using frequent power outages. Once Caphammer degrades the capacitor of the victim EHS, it can suffer from denial of service, data corruption, data encryption failure, and abnormal termination. To defeat Caphammer, this article presents FanCap, a capacitor bank scheduling scheme that can dynamically transform energy storage organization, taking into account the capacitor vulnerability. The experimental results demonstrate that FanCap can successfully thwart Caphammer with a negligible run-time overhead.