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TBAS: Enhancing Wi-Fi Authentication by Actively Eliciting Channel State Information

In this paper, we propose Time Bounded Anti- Spoofing (TBAS), a novel spoof detection method for W-Fi networks. TBAS is based on the simple idea of comparing the channel states embedded in packets received within a short interval and discarding the packets if the channel state change is above a reasonable level for the interval. We leverage the packet transmission policies in Wi-Fi to actively elicit packets for the channel state check without modifying the Wi-Fi protocol, such as sending a dummy data packet which will automatically elicit an acknowledgement packet. Comparing to the existing methods that wait passively for the packets from the packet sender for the channel state information, TBAS has the full control of time to collect the channel state, such that it can use stricter rules to classify the packets and achieve higher security. We solve key problems in TBAS, including a Channel State Check (CSC) procedure which determines if two packets are from the same sender, as well as a simple protocol wrapped around CSC to reduce the overhead. We implement TBAS on the Sora software defined ratio and our trace-driven emulations show that TBAS can achieve desirable False Positive and False Negative ratios with very low overhead.