A Robust Algorithm against Delay Cyber-Attacks in PTP applicable for the fGn Environment

The Precision Time Protocol (PTP) applies for precise micro-seconds time synchronization for computer networks. Time synchronization (offset) and frequency synchronization (clock skew) can be achieved based on the hardware time stamps that the Master and Slave clocks are exchanging between them. PTP is applicable in many industrial and military systems or applications where micro-second accuracy is essential. Therefore, it makes PTP vulnerable to malicious Cyber-attacks that may take the computer networks out of sync. This work presents a robust algorithm against fixed delay Cyber-attacks in a network characterized by a fractional Gaussian noise (fGn) environment. The fixed delay Cyber-attack changes the fixed delay in the Forward or Reverse paths. The proposed algorithm detects and deletes suspicious time stamps and, for the first time, also estimates and completes those deleted time stamps. Namely, it estimates those time stamps without the fixed delay added by the delay Cyber-attack on the Forward or Reverse paths. The proposed algorithm is applied to the three recently presented clock skew estimators (the one-way delay (OWD) clock skew estimators for the Forward and Reverse paths and the two-way delay (TWD) clock skew estimator), proposed by the same authors. Simulation results confirm that our proposed algorithm against the delay Cyber-attack indeed preserves the clock skew performances of those three clock skew estimators.