Covert Communications through Imperfect Cancellation

TL;DR

This paper introduces a covert communication method within IEEE 802.11 OFDM signals, balancing concealment with minimal impact on standard compliance and error rates, using imperfect cancellation techniques.

Contribution

It presents a novel approach for embedding hidden messages in Wi-Fi signals that adhere to spectral masks and analyzes its impact on signal parameters and error rates.

Findings

Hidden signals can be reliably retrieved under certain conditions.

The method maintains spectral compliance with IEEE 802.11 standards.

Impact on OFDM parameter estimation and error rates is quantifiable.

Abstract

We propose a method for covert communications using an IEEE 802.11 OFDM/QAM packet as a carrier. We show how to hide the covert message so that the transmitted signal does not violate the spectral mask specified by the standard, and we determine its impact on the OFDM packet error rate. We show conditions under which the hidden signal is not usable and those under which it can be retrieved with a usable bit error rate (BER). The hidden signal is extracted by cancellation of the OFDM signal in the covert receiver. We explore the effects of the hidden signal on OFDM parameter estimation and the covert signal BER. We conclude with an experiment using Over-The-Air recordings of 802.11 packets, inject the hidden