Secure positioning and navigation with GNSS

As our societies have come to increasingly rely on global navigation satellite systems (GNSS) for many critical tasks and the control of crucial infrastructures, so have increased the incentives to attack them for financial, or political motives. Two kinds of threats are particularly relevant to the GNSS context: jamming, carried out at the physical layer and aiming at denying the service to receivers in a given area, and spoofing, that aims to induce the receiver into computing a false position, velocity or time, by forging or illegitimately modifying the GNSS signal either at the data/message level or at the code/signal level. In this chapter we review the several countermeasures that have been devised, especially against the spoofing threat, both at the data and signal level, and discuss their effectiveness in relationship to the context and the possible side information available to the attacker and receiver. Eventually, we propose novel models for the analysis and design of partial spreading code encryption and for the integration of side information coming from other sensors into the integrity verification for the computed GNSS trajectory.