*********************************
There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
*********************************
Title: Optimal Codes For Information-theoretically Covert Communication
Committee:
Dr. Matthieu Bloch, ECE, Chair , Advisor
Dr. John Barry, ECE
Dr. Stephen Ralph, ECE
Dr. Faramarz Fekri, ECE
Dr. Yao Xie, ISyE
Abstract:
We consider a problem of coding for covert communication, which involves ensuring reliable communication between two legitimate parties while simultaneously guaranteeing a low probability of detection by an eavesdropper. Specifically, we develop an optimal low-complexity coding scheme that achieves the information-theoretic limits of covert communication over binary-input discrete memoryless channels. We first demonstrate the non-triviality of designing codes for covert communication by showing the impossibility of achieving information-theoretic limits using linear codes without a shared secret key for a regime in which information theory proves the possibility of covert communication without a secret key. We then circumvent this impossibility by introducing non-linearity into the coding scheme through the use of pulse position modulation (PPM) and multilevel coding (MLC). This MLC-PPM scheme exhibits several appealing properties; in particular, for an appropriate decoder, the channel at a given level is independent of the total number of levels and the codeword length. We exploit these properties to show how one can use families of channel capacity- and channel resolvability-achieving codes to concretely instantiate a covert communication scheme.
