Optimal codes for information-theoretically covert communication

Covert communication;Physical-layer security;Coding for secrecy

Kadampot, Ishaque Ashar ; Bloch, Matthieu Electrical and Computer Engineering Barry, John Ralph, Stephen Fekri, Faramarz Xie, Yao ; Bloch, Matthieu

University:Georgia Institute of Technology

Department:Electrical and Computer Engineering

关键词: Covert communication;    Physical-layer security;    Coding for secrecy;   

Others  :  https://smartech.gatech.edu/bitstream/1853/62730/1/KADAMPOT-DISSERTATION-2020.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

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. Further, we extend the MLC-PPM scheme using bi-orthogonal PPM symbols to achieve information-theoretic limits of covert communication over additive white Gaussian channels. Finally, we illustrate the application of this scheme for the secret-key generation problem with a covertness constraint.