They aren't. A spoofer doesn't need to know what the signal means/be able to decrypt it. Just retransmit signal received from a different place at higher power. Only way to distinguish it from a real one is timing, but that requires an atomic clock, which is $15,000 and too expensive for most applications.
But, military grade GPS receivers use virtual beam forming to achieve a very high attenuation of spoofing signal so they are extremely hard to spoof, they always get the real signal as stronger.
Yeah, I'm not terribly worried about military drones. But as a civilian pilot I worry a lot about whether the non-military-grade GPS in my airplane is telling me the truth.
anovikov|8 years ago
But, military grade GPS receivers use virtual beam forming to achieve a very high attenuation of spoofing signal so they are extremely hard to spoof, they always get the real signal as stronger.
heartbreak|8 years ago
lisper|8 years ago
daniel-cussen|8 years ago