3 ms·

Dumb question, but how does this deal with security? Can't anyone broadcast valid but malicious data on 1575.42 MHz? (e.g. to crash planes/missiles etc) EDIT:

by gfd 5y ago

Dumb question, but how does this deal with security? Can't anyone broadcast valid but malicious data on 1575.42 MHz? (e.g. to crash planes/missiles etc) EDIT: found wiki from some quick googling https://en.wikipedia.org/wiki/Spoofing_attack#Global_navigation_satellite_system_spoofing https://en.wikipedia.org/wiki/Spoofing_attack#Global_navigat...

ezconnect 5y ago
It's illegal in most countries to jam or transmit on that frequency.
- ncmncm 5y ago
  But common in military activity.
- grkvlt 5y ago
  it's already illegal to cause a plane to crash, regardless of the mechanism used, and the legality of the mechanism generally has no bearing on its effectiveness...! but, gps (or other gndss) spoofing or jamming is effective, and i think that commercially available jammers simply broadcast reasonably broad spectrum noise around that frequency, which can overwhelm nearby recievers; although the article describes how noise rejection is performed, it has its limits. spoofing is more difficult, but still possible, including simple re-broadcast attacks using data received at another location, however i believe these things are non-trivial for military receivers due to countermeasures like beam steering?
myself248 5y ago
Yes, and there are moves in the next generation to add cryptographic signatures to the satellite streams. Someone could still jam it, but they couldn't spoof it. Tons of info starting here: https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-1/ https://berthub.eu/articles/posts/galileos-authentication-al... Continued here: https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-2/ https://berthub.eu/articles/posts/galileos-authentication-al... And finally here: https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-3/ https://berthub.eu/articles/posts/galileos-authentication-al...
ncmncm 5y ago
Military aviation systems often have their GPS antenna designed to receive signals only from above.
ridgeguy 5y ago
One security measure effective against a simple class of GPS spoofing is to check against the satellites' epheremi. For example, if your RX tells you that bird #7 is part of your location fix, but it knows from prior valid ephemeris data that that bird is currently below your horizon, the bogosity indicator will flash red. Ditto with certain pull-off spoofing methods.

by gfd 5y ago

ezconnect 5y ago

It's illegal in most countries to jam or transmit on that frequency.

ncmncm 5y ago
But common in military activity.
grkvlt 5y ago
it's already illegal to cause a plane to crash, regardless of the mechanism used, and the legality of the mechanism generally has no bearing on its effectiveness...! but, gps (or other gndss) spoofing or jamming is effective, and i think that commercially available jammers simply broadcast reasonably broad spectrum noise around that frequency, which can overwhelm nearby recievers; although the article describes how noise rejection is performed, it has its limits. spoofing is more difficult, but still possible, including simple re-broadcast attacks using data received at another location, however i believe these things are non-trivial for military receivers due to countermeasures like beam steering?

myself248 5y ago

Yes, and there are moves in the next generation to add cryptographic signatures to the satellite streams. Someone could still jam it, but they couldn't spoof it. Tons of info starting here: https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-1/ https://berthub.eu/articles/posts/galileos-authentication-al... Continued here: https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-2/ https://berthub.eu/articles/posts/galileos-authentication-al... And finally here: https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-3/ https://berthub.eu/articles/posts/galileos-authentication-al...

ncmncm 5y ago

Military aviation systems often have their GPS antenna designed to receive signals only from above.

ridgeguy 5y ago

One security measure effective against a simple class of GPS spoofing is to check against the satellites' epheremi. For example, if your RX tells you that bird #7 is part of your location fix, but it knows from prior valid ephemeris data that that bird is currently below your horizon, the bogosity indicator will flash red. Ditto with certain pull-off spoofing methods.