Time-based GNSS attack detection

To safeguard Civilian Global Navigation Satellite Systems (GNSS) external information available to the platform encompassing the GNSS receiver can be used to detect attacks. Cross-checking the GNSS-provided time against alternative multiple trusted time sources can lead to attack detection aiming at controlling the GNSS receiver time. Leveraging external, network-connected secure time providers and onboard clock references, we achieve detection even under fine-grained time attacks. We provide an extensive evaluation of our multi-layered defense against adversaries mounting attacks against the GNSS receiver along with controlling the network link. We implement adversaries spanning from simplistic spoofers to advanced ones synchronized with the GNSS constellation. We demonstrate attack detection is possible in all tested cases (sharp discontinuity, smooth take-over, and coordinated network manipulation) without changes to the structure of the GNSS receiver. Leveraging the diversity of the reference time sources, detection of take-over time push as low as 150us is possible. Smooth take-overs forcing variations as low as 30ns are also detected based on on-board precision oscillators. The method (and thus the evaluation) is largely agnostic to the satellite constellation and the attacker type, making time-based data validation of GNSS information compatible with existing receivers and readily deployable.