PowerKey: Generating Secret Keys from Power Line Electromagnetic Interferences

With the increasing adoption of Internet-of-Things devices, autonomously securing device-to-device communications with minimal human efforts has become mandated. While recent studies have leveraged ambient signals (i.e., amplitude of voltage harmonics) in a building’s power networks to secure plugged IoT devices, a key limitation is that the exploited signals are consistent only among nearby outlets, thus resulting in a low key matching rate when devices are far from each other. In this paper, we propose PowerKey to generate secret keys for multiple plugged IoT devices in an electrical domain (e.g., a lab or an office suite). Concretely, PowerKey taps into ambient power line electromagnetic interferences (EMI): there exist multiple spatially unique EMI spikes whose frequencies vary randomly but also remain consistent at participating power outlets to which IoT devices are connected. We propose K-mean clustering to locate common EMI spikes offline at participating outlets and then dynamically extract secret keys at runtime. For evaluation, we conduct experiments in two different locations — one research lab and one suite with multiple rooms. We show that with PowerKey, multiple devices can successfully obtain symmetric secret keys in a robust and reasonably fast manner (i.e., 100% successful at a bit generation rate of up to 52.7 bits/sec).