Field testing of GNSS user protection techniques

GNSS is a key element for a wide range of applications in our daily lives. Mass-market applications such as sports tracking or user guidance, liability-critical applications such as banking and telecommunication time synchronization, and safety critical services such as aviation and automotive-related solutions, all rely on GNSS. The huge growth experimented during the last decade puts GNSS in the target of attackers. The Galileo program is complementing the Galileo Open Service with Navigation Message Authentication (OSNMA) and providing signal authentication through the Commercial Service signals. These new services will be able to provide added protection to the current GNSS applications. Nevertheless, these features will require the users to implement new algorithms to exploit them. In this context, the European Commission launched the Navigation Authentication through Commercial Service-Enhanced Terminal (NACSET) project aiming at researching and implementing different techniques to detect and mitigate thus improving the resilience at user-level. In the frame of the NACSET project, a user terminal has been developed based on a high-end multi-GNSS receiver that is able to track E1/L1 and E6-B/C signals for data and signal protection. The terminal is equipped with a set of resilience techniques. Among these techniques, this paper focuses on an anti-replay technique protecting against zero-delay Secure Code Estimate-Replay (SCER) attacks based on the analysis of the unpredictable symbols from OSNMA cryptographic data. This paper firstly describes the NACSET project and its aim. Secondly, the theory of Anti-replay protection is explained from the point of view of a receiver, and anti-replay techniques based on OSNMA are introduced. Then, we describe the SCER simulator developed to assess the performances of the technique. To conclude, an attack is defined and performed with the SCER simulator over a real receiver. The results with and without OSNMA replay protection are presented and explained, and some conclusions of the experiment are derived.