On secure communications without eavesdropper channel state

The ubiquity of wireless connectivity between an ever-increasing number of devices has confirmed dire past predictions of widespread eavesdropping (among other security concerns) in wireless networks, further promoting the need for secure communications. Of particular interest are physical layer techniques which exploit error-correction coding intrinsic to digital transceivers and which offer two clear advantages: (i) no need for key distribution; and (ii) secrecy that is not conditioned on a computationally limited adversary. Present techniques, however, assume some knowledge of the channel connecting the transmitter to the eavesdropper; if the eavesdropper is truly passive, this critical parameter is unavailable. We therefore examine secure communication schemes that do not assume knowledge of the eavesdropper's channel, yet remain keyless in their operation. Two schemes are offered, with behavior intermediate between cryptographic and information-theoretic solutions.