Secure two-way fiber-optic time transfer against sub-ns asymmetric delay attack

TL;DR

This paper proposes a dynamic scheme to defend against sub-nanosecond asymmetric delay attacks in two-way fiber-optic time transfer, enhancing secure precise synchronization with theoretical and experimental validation.

Contribution

A novel dynamic detection method based on a two-state clock model is introduced to identify and mitigate asymmetric delay attacks in fiber-optic time transfer systems.

Findings

Achieved time stability of 24.5ps at 1s averaging time

Demonstrated detection of sub-ns delay attacks experimentally

Validated the scheme's effectiveness through theoretical simulation

Abstract

Two-way fiber-optic time transfer is a promising precise time synchronization technique with sub-nanosecond accuracy. However, asymmetric delay attack is a serious threat which cannot be prevent by any encryption method. In this paper, a dynamic model based scheme is proposed to defense the sub-nanosecond asymmetric delay attack. A threshold is set according to the estimated time difference by a two-state clock model where the fixed frequency difference is excluded from the time difference to detect the asymmetric delay attack which is smaller than the time difference induced by the fixed frequency difference. Theoretical simulation and experimental demonstration are implemented to prove the feasibility of the scheme. A two-way fiber-optic time transfer system with time stability with 24.5ps, 3.98ps, and 2.95ps at 1s, 10s, and 100s averaging time is shown under sub-ns asymmetric time delay attack experimentally. The proposed method provides a promising secure sub-ns precise time synchronization technique against asymmetric delay attack.