PINBALL: Universal and Robust Signature Extraction for Smart Home Devices

Event-level signatures for smart home Internet-of-Things devices are the fundamental of many security enhancement systems for home networks equipped with smart home systems. However, existing event signature extraction methods for smart home devices are in a dilemma where the precision, generality and robustness of the signatures cannot be satisfied at the same time. In this paper, we present PINBALL, a universal tool that can automatically extract robust signatures for events happening on smart home devices. PINBALL uses length distributions of bidirectional packets generated by smart home devices as signatures for their trigger-events. It is lightweight and independent of the protocols. Besides, the signatures extracted by PINBALL are more robust and achieve better detection accuracy than previous state-of-the-art methods. Nevertheless, we argue that such signatures are double-edged swords that can not only help with the network management but also threaten the user privacy. We analyze these signatures from a comprehensive perspective and try to propose some possible measures to make such packet length side channels able to be used for legitimate purposes like security enhancement with the user privacy preserved.