Wireless systems are of paramount importance for providing ubiquitous data transmission for smart cities. However, due to the broadcasting and openness of wireless channels, such systems face potential security challenges. UAV-assisted covert communication is a supporting technology for improving covert performances and has become a hot issue in the research of wireless communication security. This paper investigates the performance of joint covert and security communication in a tow-hop UAV-assisted wireless system, where a source transmits the covert message to a destination with the help of an untrusted UAV. We first design a transmission scheme such that use UAVs to assist in covert communications while ensuring the security of covert messages. Then, we develop a theoretical model to derive the expressions for the detection error probability of the warden and the covert and security rate, and the maximum covert and security rate is optimized by power control under a given covertness and security requirements. Finally, numerical results are provided to illustrate our theoretical analysis and the performance of covert and security communication in such systems.

翻译：无线系统为智慧城市提供无处不在的数据传输至关重要。然而，由于无线信道的广播性和开放性，此类系统面临潜在的安全挑战。无人机辅助的隐蔽通信是提升隐蔽性能的关键支撑技术，已成为无线通信安全研究中的热点问题。本文研究了两跳不可信无人机辅助无线系统中的联合隐蔽与安全通信性能，其中信源借助不可信无人机向目的节点传输隐蔽消息。我们首先设计了一种传输方案，利用无人机辅助隐蔽通信的同时确保隐蔽消息的安全性。随后，建立了理论模型以推导监护者检测错误概率、隐蔽与安全速率的表达式，并在给定隐蔽性与安全性要求下通过功率控制优化最大隐蔽与安全速率。最后，通过数值结果验证了理论分析及该类系统中隐蔽与安全通信的性能。