On covert throughput performance of two-way relay covert wireless communications

Abstract

Covert wireless communication ensures information security by hiding the existence of the information transmission itself. Available works mainly focused on the covert throughput study of one-hop wireless communications, while the performance limit of covert throughput in important two-way two-hop scenarios remains largely unknown. As the most significant contribution, this paper, for the first time, investigates such performance limit in a system where two sources wish to covertly exchange information through a relay against the detection of a warden, i.e., a malicious node that attempts to detect the existence of communication between the two sources. As the second contribution, this paper considers various scenarios regarding the warden’s prior knowledge about the relay, the sources/relay’s prior knowledge about the warden, as well as different relaying patterns, and then proposes a covertness strategy to resist the warden’s detection for each scenario. As the last contribution, we derive the scaling law result for the covert throughput of the system for each scenario, i.e., the maximum number of bits that the two sources can exchange subject to a constraint on the detection probability of the warden. The results in this paper indicate that the covert throughput of the concerned system follows the well-known square root scaling law, which is independent of the relaying patterns, detection schemes, covertness strategies, and prior knowledges of the sources/relay and warden.