Controllable Asymmetric Attack Against Practical Round-Trip Fiber Time Synchronization Systems

The round-trip fiber time synchronization system is preferred for high-precision time synchronization due to its easier implementation compared to bidirectional systems. However, its link-symmetry assumption renders it susceptible to asymmetric delay attacks, posing a serious threat to the system that current encryption methods cannot effectively prevent. This letter proposes a controllable asymmetric channel attack scheme for the round-trip fiber time synchronization system. The objective is to assess the impact of asymmetry on time synchronization accuracy by measuring the time difference between the local and remote ends of the system. Experimental results demonstrate that by employing asymmetric channels, the synchronization accuracy of the system can be reduced to 1.01 ns, 2.09 ns, and 5.06 ns, respectively, from the initial accuracy of 52.40 ps. This work highlights the critical security issue in round-trip systems, emphasizing the urgent need for effective countermeasures against asymmetric delay attacks.