Exploiting Wireless Systems for Covert Communications

The desire to hide communications has existed since antiquity. This includes hiding the existence of the transmission and the location of the sender. Wireless networks offer an opportunity for hiding a transmission by placing a signal in the radio frequency (RF) occupied by a target network which also has the added benefit of lowering its probability of detection.;This research hides a signal within the RF environment of a packet based wireless (infrastructure) network. Specifically, in this research the interfering (covert) signal is placed in the guard band of the target network's orthogonal frequency division multiplexed (OFDM) signal. We show that the existence of adaptive protocols allow the target network to adjust to the existence of the covert signal. In other words, the wireless network views the covert network as a minor change in the RF environment; this work shows that the covert signal can be indistinguishable from other wireless impairments such as fading.;The impact of the covert signal on the target system performance is discovered through analysis and simulation; the analysis and simulation begin at the physical layer where the interaction between the target and covert systems occurs. After that, analysis is performed on the impact of the covert link on the target system at the data-link layer. Finally, we analyze the performance of the target system at the transmission control protocol (TCP) layer which characterizes the end-to-end performance. The results of this research demonstrate the potential of this new method for hiding the transmission of information. The results of this research could encourage the creation of new protocols to protect these networks from exploitation of this manner.