Untappable wireless communication leveraging surplus resources at the low layers

Abstract

With the development of wireless networks, attacks such as personal information hijacking through packet sniffing are increasing. However, encryption techniques to protect data are not sufficient to prevent this. In this paper, we propose a secret communication system that can not be tapped using surplus resources of wireless network lower layer. To make the communication untappable and exchange hidden messages exclusively between the sender and receiver, our system utilizes the OFDM padding mechanism of the PHY layer and the CRC error mechanism of the MAC layer. General network receivers immediately discard OFDM padding bits at PHY layer and corrupted packets by CRC error at MAC layer, however, we change the role of each low layers. We implemented the proposed system through USRP, a SDR platform and commercial Wi-Fi device driver, and achieved throughput of up to 18 Mbps and over 99% hidden message recovery rates.