Eavesdropping Risk Evaluation on Terahertz Wireless Channels in Atmospheric Turbulence

Wireless networks operating at terahertz (THz) frequencies have been proposed as a promising candidate to support the ever-increasing capacity demand, which cannot be satisfied with existing radio-frequency (RF) technology. Besides this, wireless channels in the THz range could be less vulnerable to interceptions because of their high beam directionality and small signal coverage. However, a risk for eavesdropping can still exist due to the multipath effects caused by unintended scattering when the channels operate in outdoor scenarios, such as in rain, snow, atmospheric turbulence, etc. In this work, eavesdropping risks for THz channel passing atmospheric turbulences are evaluated from a physical layer perspective. Secrecy capacity and outage probability of a point-to-point THz wireless channel are derived by considering the multipath scattering effect. Deterministic and probabilistic eavesdropping attacks are assessed. Their dependence on turbulence strength, eavesdropper's position and channel conditions is investigated.