Covert Wireless Communications in the Presence of an Active Adversary

Covert wireless communication or low probability of detection (LPD) communication that employs the noise or jamming signals as the cover to hide user's signals can prevent an adversary Willie from discovering user's transmission attempts. Previous work on this problem typically presupposed that Willie is static and has one antenna, often neglecting an active adversary who can dynamically adjust his/her location to make better statistic tests. In this paper, we analyzed the effect of an active adversary in the covert wireless communication over AWGN channels and found that, having gathered samples at different places, the active adversary can easily detect Alice's transmission behavior via a trend test. Furthermore, a more powerful adversary with multiple antennas is harder to be deceived, and his detection time can be greatly shortened.