Owing to the high probability of line-of-sight channels, unmanned aerial vehicle (UAV)Unmanned Aerial Vehicle (UAVs) communications face inherent vulnerabilities to eavesdropping. A promising solution to enhance the security of UAV communication is the integration of reconfigurable intelligent surface (RIS)Reconfigurable Intelligent Surface (RIS), given its capacity to manipulate propagation environment. This chapter is dedicated to the investigation of secureSecure transmission scheme for RIS-assisted UAV communication networks. Specifically, we introduce an optimization problem aimed at maximizing the average secrecy rateSecrecy rate. This problem intricately combines the optimization of transmit beamforming, passive beamforming, and UAV trajectory. To tackle this challenge, we break it down into three distinct sub-problems and propose an iterative algorithm for their alternating resolution. RISReconfigurable Intelligent Surface (RIS) plays a pivotal role in bolstering this security framework, enhancing received signals at intended users while concurrently degrading the quality of eavesdropping links. The efficacy of our proposed scheme is validated through a set of simulations, shedding light on its effectiveness and offering valuable insights. Finally, we highlight several challenges that require resolution for practical implementation in this evolving domain.