Deducing user presence from inter-message intervals in home automation systems

Abstract

Privacy in Home Automation Systems is a topic of increasing importance, as the number of installed systems constantly grows. In this paper we investigate the ability of an outside observer to link sets of message timestamps together to predict user presence and absence. The question we try to answer is: If attacker Eve has captured 1 hour of traffic from victim Alice’s HAS and knows whether Alice was present at that time, can Eve deduce Alice’s state by capturing another hour of traffic? We apply different statistical tests and show that in certain situations, the attacker can infer the user’s presence state with absolute confidence.