Comment on Long-Theorized GPS Weakness Exploited on Large Scale by drenehtsral

It seems like you could at least geeatly increase the coat and complexity of GPS spoofing if you generated some (even small) private keys to be rotated often and had each sattelite broadcast small signed messages along with the public keys needed to verify the next couple days of signed messages. At that point if you wanted to pass yourself off as a fake GPS sattelite you'd need to do so continually, within range of your spoofing target, for at minimum the duration of the key rotation interval.

That wouldn't prevent jamming, but it would increase the cost and complexity of spoofing by a significant factor and since the spoofing transmitters would need to be running for several days in range of the target it would make them easier to detect and eliminate, as well as making it less practical to target moving vehicles from a fixed spoofing rig because once they wandered in from outside they'd see that the signatures of the spoofed messages no longer jibed with the previously announced public key as per the key rotation schedule.

This would require using one of the extra data fields over a significant time scale so targets might be spoofed for seconds or minutes but not hours or days (it would require that receivers be on and listening to get primed with the announced public keys).

In essence the signatures would say "I'm still the same satellite I was yesterday and the day before" rathet than saying "I am so-and-so", though I suppose you could also sign the satellites' public keys with a trusted cert, etc. but that would require more data and thus a longer interval to acquire the upcoming timespan's public keys...