3 ms·
Because an attacker can just replay legitimate broadcasts with slightly skewed time and origin and introduce huge errors into the fix.
by 15155 4mo ago
Because an attacker can just replay legitimate broadcasts with slightly skewed time and origin and introduce huge errors into the fix.
- stavros 4mo agoJust because we can't solve all current problems doesn't mean we shouldn't solve any current problems. If you want to prevent replaying as well, add a counter.
- stinkbeetle 4mo ago> Just because we can't solve all current problems doesn't mean we shouldn't solve any current problems. Obviously not, but solving problems is always a cost benefit and we went from all spoofing is impossible to some spoofing is possible. What is the benefit of doing this and what is the cost? > If you want to prevent replaying as well, add a counter. It's not clear that would be able to prevent spoofing if the attacker could overwhelm and degrade the real signal.
- throw0101a 4mo ago>> An even bigger WTF is why GPS data isn't signed with some official key so spoofing is impossible. > Because an attacker can just replay legitimate broadcasts with slightly skewed time and origin and introduce huge errors into the fix. Galileo uses a signing system (Timed Efficient Stream Loss-Tolerant Authentication, TESLA) to protect the authenticity of its messages, including preventing replays: * https://gssc.esa.int/navipedia/index.php/Galileo_Open_Service_Navigation_Message_Authentication https://gssc.esa.int/navipedia/index.php/Galileo_Open_Servic... * https://datatracker.ietf.org/doc/html/rfc4082 https://datatracker.ietf.org/doc/html/rfc4082 (TESLA) * https://people.eecs.berkeley.edu/~tygar/papers/TESLA_broadcast_authentication_protocol.pdf https://people.eecs.berkeley.edu/~tygar/papers/TESLA_broadca... * https://users.ece.cmu.edu/~adrian/projects/stream/node1.html https://users.ece.cmu.edu/~adrian/projects/stream/node1.html
- eqvinox 4mo agoI don't think this helps against someone receiving the signals (all satellites) and rebroadcasting them. The effect of that would be that any receiver of those rebroadcasted signals will believe they are located where the receiver of the rebroadcast is located (just the time is slightly off/late, but that doesn't help much without a reference to check against.)
- rkourdis 4mo agoIt's been a few years since I've worked with this stuff but I'm under the impression that you can do this sort of replay only for a short amount of time. If so, is there a point? If the receiver expects a key to have been revealed at a particular timestep, it won't accept a replayed message with that key after that, so you can't record and replay indefinitely. EDIT: Unless you indeed meant to instantly replay - would the receiver accept the highest strength signal, ie. yours?
- eqvinox 4mo agoI did indeed mean instant replay, and yeah the better your clock in the receiver the narrower the window of delay that the spoofer has to work with. If you can get the time from a 5G network or NTP down to 10ms, that'd mean you can detect being spoofed at >=3km distance if the spoofer has 0 delay (which is doable with a plain analog rebroadcast).
- 15155 4mo agoThe point is to prevent missiles and drones from impacting their intended targets. For most payloads and targets, this requires very little distortion.
- DoctorOetker 4mo agonobody would send a military vehicle (manned or drone) without initializing a proper clock, the replays would be stale.
- 4mo ago