Privacy Leakage in Wireless Charging

Wireless charging is becoming an essential power supply pattern for electronic devices. Currently, mainstream smartphones are almost compatible with wireless charging. However, when the charging efficiency is continuously improved, its security challenge still remains open yet overlooked. In this paper, we reveal that severe security flaws exist in the wireless charging procedure of off-the-shelf commodity smartphones. Specifically, we find that an attacker can utilize the electromagnetic induction effect between the wireless charger and the smartphone to detect the activities and operations performed on the smartphone. We term such attack as EM-Surfing side-channel attack and build a theoretical model to show its feasibility. To explore the hazard of \textit{EM-Surfing}, we propose a three-module attack method, with which we conduct real-world experiments over three mainstream models of smartphones. The results show that the attacker can achieve over 99%, 96%, 94%, and 97% accuracy when inferring the passcode, keystroke, App information, and speech content. We also design an App named SecCharging to prevent smartphones from EM-Surfing attacks. The defense experiment results demonstrate that SecCharging can mitigate the threats posed by EM-Surfing effectively.