Authenticating Smart Home Devices via Home Limited Channels

Nowadays, most Internet of Things devices in smart homes rely on radio frequency channels for communication, making them exposed to various attacks such as spoofing and eavesdropping attacks. Existing methods using encryption keys may be inapplicable on these resource-constrained devices that cannot afford the computationally expensive encryption operations. Thus, in this article, we design a key-free communication method for such devices in a smart home. In particular, we introduce the Home-limited Channel (HLC) that can be accessed only within a house yet inaccessible for outside-house attackers. Utilizing HLCs, we propose HlcAuth, a challenge-response mechanism to authenticate the communications between smart devices without keys. The advantages of HlcAuth are low cost, lightweight as well as key-free, and requiring no human intervention. According to the security analysis, HlcAuth can defeat replay attacks, message-forgery attacks, and man-in-the-middle (MiTM) attacks, among others. We further evaluate HlcAuth in four different physical scenarios, and results show that HlcAuth achieves 100% true positive rate (TPR) within 4.2m for in-house devices while 0% false positive rate (FPR) for outside attackers, i.e., guaranteeing a high-level usability and security for in-house communications. Finally, we implement HlcAuth in both single-room and multi-room scenarios.