Title: Fundamental Limits of Covert Communications
Speaker: Prof. Dennis Goeckel
Recent revelations on government surveillance programs have highlighted that it is often the identity of the sender and receiver of a message (the so-called "meta-data"), rather than the content of the message, which needs to be protected. Covert communication is the transmission of information from a node Alice to intended recipient Bob where not only the contents but also the message's existence is hidden from an observer (warden Willie). In this talk, we consider the fundamental limits of covert communications in wireless and wireline channels; in particular, we consider the number of information bits that can be reliably transmitted from Alice to Bob without detection of the transmission by Willie. When both the Alice-Bob and the Alice-Willie channels are additive white Gaussian noise (AWGN) channels, we demonstrate that Alice can transmit sqrt(n) (and no more than sqrt(n)) bits covertly and reliably in n channel uses. Alice's power is limited by Willie's ability to detect her transmission from the background noise. Thus, we also consider how performance changes in more practical scenarios where Willie must estimate his background noise characteristics from the environment that may contain jamming and/or signal fading and how this may be exploited to improve the Alice-Bob throughput. The theoretical work is validated with a proof-of-concept optical communications experiment. Finally, we turn to wireline channels and consider the fundamental limits on conveying information covertly and reliably through the alteration of packet timings.
Dennis Goeckel received his BS from Purdue University in 1992, and his MS and PhD from the University of Michigan in 1993 and 1996, respectively. Since 1996, he has been with the Electrical and Computer Engineering Department at the University of Massachusetts at Amherst, where he is currently a Professor. Prof. Goeckel has been a Lilly Teaching Fellow (2000-2001) and received the University of Massachusetts Distinguished Teaching Award in 2007. He has served on the Editorial Board of a number of international journals in communications and networking: IEEE Transactions on Networking, IEEE Transactions on Mobile Computing, IEEE Transaction on Wireless Communications, and the IEEE Transactions on Communications. He received the NSF CAREER Award in 1999 and is an IEEE Fellow.