Wireless Covert Channel With Polarized Dirty Constellation in Backscatter Communication

Ambient backscatter communication has become a low-cost and green solution to next-generation Internet-of-Things (IoT). In this paper, we investigate a problem of wireless covert communication in backscatter communication system. The purpose of covert communication is to hide the process of communication and avoid being detected by eavesdropper. Covert messages are modulated into a random-like noise, and then superimposed on the carrier signal. Specially, we propose a wireless covert channel with polarization dirty constellation (WCC-PDC), which is polarized to solve the problem of low signal power in backscatter communication. Some methods are used to combine covert code block with carrier information block and increase the undetectability of covert communication. Additionally, successive-cancellation decoder and successive-cancellation list decoder are adopted to improve the reliability of WCC-PDC. Simulation results are finally provided to verify the improvement of undetectability and reliability with WCC-PDC.

Shannon-limit approached information reconciliation for quantum key distribution

Information reconciliation (IR) corrects the errors in sifted keys and ensures the correctness of quantum key distribution (QKD) systems. Polar codes-based IR schemes can achieve high reconciliation efficiency; however, the incidental high frame error rate decreases the secure key rate of QKD systems. In this article, we propose a Shannon-limit approached (SLA) IR scheme, which mainly contains two phases: the forward reconciliation phase and the acknowledgment reconciliation phase. In the forward reconciliation phase, the sifted key is divided into sub-blocks and performed with the improved block checked successive cancellation list decoder of polar codes. Afterward, only the failure corrected sub-blocks perform the additional acknowledgment reconciliation phase, which decreases the frame error rate of the SLA IR scheme. The experimental results show that the overall failure probability of SLA IR scheme is decreased to $$10^{-8}$$ 10 - 8 and the efficiency is improved to 1.091 with the IR block length of 128 Mb. Furthermore, the efficiency of the proposed SLA IR scheme is 1.055, approached to Shannon limit, when the quantum bit error rate is 0.02 and the input scale of 1 Gb, which is hundred times larger than the state-of-the-art implemented polar codes-based IR schemes.