Two Time Spoofing Algorithms on GNSS Receiver Instrumentation of Modifying Satellite Clock Correction Parameters in Navigation Message

The global navigation satellite system (GNSS) receiver instrumentation can be used for precise timing of infrastructure, such as smart grid, and time spoofing on smart grid is one of the important purposes for spoofers. In order to meet more diverse demands for time spoofing and provide possible time spoofing schemes for the defense of time spoofing, the qualitative influence of modifying main parameters of navigation message and the sensitivity of satellite clock correction parameters are analyzed, and two GNSS time spoofing algorithms of modifying satellite clock correction parameters in navigation message are proposed: step-type time spoofing algorithm and slowly varying-type time spoofing algorithm. The principles of the two algorithms are deduced, and the performance and effectiveness of the two algorithms are verified and evaluated through simulation experiments and practical experiments using the open source GNSS observation data provided by Curin GNSS-SPAN Group. The experimental results and insights are as follows: for step-type time spoofing, the average error of time spoofing is −0.53 m and the distance deviation in rectangular space coordinates of the receiver instrumentation is-1.24× 10⁻³m, which can achieve the purpose of spoofing instantaneously, and it has the advantage of spoofing in a very short time, but the step type change of clock offset of receiver instrumentation is easier to be identified and detected by the victim receiver instrumentation; for slowly varying-type time spoofing, the average error of time spoofing is −2.49 m, and the distance deviation in rectangular space coordinates of the receiver instrumentation is 1.52 m; the average error of time spoofing is slightly larger, but the way of slowly increasing clock offset of receiver instrumentation will greatly improve the concealment of spoofing and greatly increase the detection difficulty for slowly varying-type spoofing, but it also takes longer to achieve the ultimate goal of spoofing. Therefore, the spoofer is very likely to implement the two different time spoofing proposed, and their performance and characteristics are different.