Wireless communication technique operating at terahertz (THz) frequencies is regarded as the most potential candidate for future wireless networks due to its wider frequency bandwidth and higher directionality when compared with that employing radio frequency (RF) and millimeter waves (mmWaves). It has been proved that the high directionality owned by THz wireless links could help to reduce the possibility of eavesdropping attacks at physical layer. However, for outdoor applications in adverse weathers (such as water fog, dust fog, rain and snow), scattering and absorption effects suffered by a THz link due to weather particles and gaseous molecules could degrade its secrecy performance seriously. In this work, we present theoretical investigations on physical layer security of a point-to-point THz link in rain and snow with a potential eavesdropper locating outside of the legitimate link path. Signal degradation due to rain/snow, gaseous attenuation and beam divergence are included in a theoretical model to estimate the link performance. Secrecy capacity of the link with carriers at 140, 220 and 340 GHz is calculated and compared. We find that the rain/snow intensity, carrier frequency and receiver sensitivity could affect the secrecy performance and their influence on insecure region and maximum safe data transmission rate is discussed and summarized.

由于与使用射频（RF）和毫米波（mmWaves）的技术相比，以太赫兹（THz）频率工作的无线通信技术具有更宽的带宽和更高的方向性，因此被认为是未来无线网络最有潜力的候选技术。事实证明，太赫兹无线链路所具有的高方向性可以帮助减少在物理层进行窃听攻击的可能性。但是，对于恶劣天气（例如水雾，粉尘雾，雨雪）的户外应用，太赫兹链路由于天气颗粒和气态分子而产生的散射和吸收效应可能会严重降低其保密性能。在这项工作中，我们对雨雪中点对点太赫兹链路的物理层安全性进行了理论研究，潜在的窃听者位于合法链路路径之外。理论模型中包括了因雨/雪，气态衰减和束发散而引起的信号衰减，以估计链路性能。计算并比较了140、220和340 GHz载波的链路的保密容量。我们发现雨/雪强度，载波频率和接收器灵敏度会影响保密性能，并讨论和总结了它们对不安全区域和最大安全数据传输速率的影响。计算并比较了140、220和340 GHz载波的链路的保密容量。我们发现雨/雪强度，载波频率和接收器灵敏度会影响保密性能，并讨论和总结了它们对不安全区域和最大安全数据传输速率的影响。计算并比较了140、220和340 GHz载波的链路的保密容量。我们发现雨/雪强度，载波频率和接收器灵敏度会影响保密性能，并讨论和总结了它们对不安全区域和最大安全数据传输速率的影响。