FastID: An undeceived router for real-time identification of WiFi terminals

In recent past, the rapid developing of mobile internet inspires the widespread use of WiFi (IEEE 802.11) technology. In WiFi, the access control of a terminal to the router remains a significant challenge because the PIN (password) and MAC address are easy to guess and forge. In this paper, we present FastID - a practical system that identifies WiFi terminals in real-time by fingerprinting their clocks. Previous approaches of clock fingerprinting require tens of minutes or even hours for clock data collection, and thus cannot be applied into real-time WiFi terminal identification. Even worse, unstable wireless communications and unknown status of terminals´ OSes may further degrade the accuracy of fingerprint computation. In comparison, FastID performs fast clock fingerprinting based on the timestamps carried by terminals´ ICMP packets. Moreover, FastID employs simple but efficient techniques to remove outliers of collected clock data and differentiate terminals based on the similarity of their distributions, making it suitable for fast terminals identification. FastID is implemented on an off-the-shelf commercial WiFi router and extensively evaluated based on 10 commodity WiFi terminals. Experimental results show that FastID is able to identify terminals with high accuracy and low cost within several seconds.