[sebzim4500]

Authenticating signals for GNSS sound like an impossible cryptographic task. What stops a malicious actor from recording the signals coming off the satellites and replaying them louder with a delay?

If you pick the delay properly you can make the plane believe it is at an arbitrary point in space and time (although of course that time would always have to be at least a few `us` in the past).

[PinguTS]

https://gssc.esa.int/navipedia/index.php/Galileo_Open_Servic...

[marsovo]

Can you point us to which part of that can deal with the scenario in question?

> What stops a malicious actor from recording the signals coming off the satellites and replaying them louder with a delay?