Capacity of an intensity interferometry channel

Abstract

In this work we show that intensity interferometry may be used to send a non-trivial amount of data steganographically over the air. Intensity interferometry was developed by Hanbury Brown and Twiss [1], [2], and originally used to measure the angular diameter of stars [3] at both optical and radio frequencies. Since then, this method has been used in many other fields to measure the size of regions of interest. Here we introduce an opposite paradigm and show that the technique may be used to transmit information wirelessly. This channel does not require additional frequency bands or additional bandwidth as it relies on a phenomenon that is already present but unexploited in current systems, and it has the potential to be highly secure against eavesdropping, and thus shows promise as a means of steganographic communication. We discuss the information theory of our new type of channel and address the trade-off between channel capacity and signaling rate. Finally, we propose communication through intensity interferometry as a method of secure steganographic communication in general and suggest its application in particular for secure communications in networks of wireless sensors.