Anti-spoofing

GNSS spoofing is an attack where the adversary broadcasts a counterfeit GNSS signal that looks valid to the receiver but encodes false ranging information. The receiver, having no inherent way to authenticate the broadcast, accepts the spoof and computes a position that drifts toward whatever the attacker wants — into a no-fly zone, off course, or to a wrong time. Spoofing attacks have grown common since 2020 as the equipment to generate them dropped to consumer prices.

Defensive techniques fall into three layers. Antenna-side: directional discrimination (a spoofer typically comes from one direction, while real satellites span the sky — a CRPA can distinguish them), polarisation purity (a hand-built spoofer may have imperfect RHCP), and arrival-time consistency checks. Signal-side: signal authentication (Galileo OS-NMA provides cryptographic verification of navigation message bits), code-correlation peak shape analysis, and dual-frequency consistency checks. Application-side: receiver autonomous integrity monitoring (RAIM), Kalman filter outlier rejection, and external sensor cross-checks (INS, magnetometer, vehicle dynamics).

AI-based signal authentication is increasingly built into high-end CRPA arrays — the DSP analyses signal characteristics (correlation peak shape, amplitude consistency, modulation purity) and flags signals that don't match the satellite signature broadcast. GNSource's 16- and 32-element arrays include AI anti-spoofing on top of their adaptive null-steering anti-jamming capability.

For most civilian users, simply having a multi-constellation receiver makes spoofing harder — the attacker must spoof every constellation simultaneously, which is much more expensive than a single-system jammer.