Due to the constraints on power supply and limited encryption capability, data security based on physical layer security (PLS) techniques in backscatter communications has attracted a lot of attention. In this work, we propose to enhance PLS in a full-duplex symbiotic radio (FDSR) system with a proactive eavesdropper, which may overhear the information and interfere legitimate communications simultaneously by emitting attack signals. To deal with the eavesdroppers, we propose a security strategy based on pseudo-decoding and artificial noise (AN) injection to ensure the performance of legitimate communications through forward noise suppression. A novel AN signal generation scheme is proposed using a pseudo-decoding method, where AN signal is superimposed on data signal to safeguard the legitimate channel. The phase control in the forward noise suppression scheme and the power allocation between AN and data signals are optimized to maximize security throughput. The formulated problem can be solved via problem decomposition and alternate optimization algorithms. Simulation results demonstrate the superiority of the proposed scheme in terms of security throughput and attack mitigation performance.

翻译：由于供电限制和加密能力有限，基于物理层安全（PLS）技术的后向散射通信数据安全备受关注。本文针对存在主动窃听者的全双工共生无线电（FDSR）系统，提出增强PLS的方案。主动窃听者可通过发射攻击信号同时窃听信息并干扰合法通信。为应对窃听者，我们提出基于伪解码和人工噪声（AN）注入的安全策略，通过前向噪声抑制确保合法通信性能。利用伪解码方法提出新型人工噪声生成方案，将人工噪声叠加在数据信号上以保护合法信道。优化前向噪声抑制方案中的相位控制及人工噪声与数据信号间的功率分配以最大化安全吞吐量。通过问题分解与交替优化算法求解所提问题。仿真结果表明，所提方案在安全吞吐量及攻击抑制性能方面具有优越性。