Secret Key Establishment via RSS Trajectory Matching Between Wearable Devices

Recently, people have witnessed a remarkable growth in the number of smart wearable devices. Accompanied with the development of a contactless data transmission technique, the lack of effective secret key establishment between lightweight wearable devices which support contactless data transmission technique becomes a security bottleneck. In this paper, we propose a novel wireless key establishment method by moving or shaking the wearable wireless devices. Instead of received signal strength (RSS) itself, we denote the RSS trajectories of two moving wireless devices as the materials of secret key. Moreover, inspired by channel reciprocity in a channel feature-based key establishment technique, we propose the concept of reciprocity of RSS trajectory that guarantees that even when the RSSs of two devices are the same, the identical RSS trajectories of two devices can successfully generate the secret key. In addition, to effectively utilize the RSS trajectories, we design a novel quantization scheme by considering the entropy and efficiency of key generation. Furthermore, we analyze the security of this key establishment procedure in an eavesdropped and monitored environment. We also perform an evaluation of 64-, 128-, 192-, and 256-b key generation in indoor/outdoor environment, and the results indicate that the times are 0.22/0.33, 0.61/0.74, 0.95/1.02, and 1.28/1.46 s, respectively. In addition, the ranges of efficiency and entropy are 0.654-0.795 and 0.968-0.993.