4 ms·

All three systems are incredibly easy to jam. The signals from the satellites are very low power by the time the reach Earth, and in fact are below the noise fl

All three systems are incredibly easy to jam. The signals from the satellites are very low power by the time the reach Earth, and in fact are below the noise floor. Recievers use processing gain tricks in order to see them at all. I don't remember the RF energy decay rate but there is a X^2 term in there, which means the energy decays exponentially with distance. So a jammer 10 miles away doesn't have to try very hard to drown out a satellite 13000 miles away.

beecafe 5y ago
Not exponentially, that would be 2^X
wildzzz 5y ago
That's why RF loss equations use dB instead of ratios or percentage. GPS is anti-jam in nature due to it's spread spectrum method but a wideband jammer could make it difficult for a receiver to build the link. Jamming mitigation includes things like using highly directional antennas and smart receivers that can recognize jammers and null them out dynamically. Additionally there is a new encrypted M-code that allows military users access to a much harder to jam signal. A smart jammer works by not just putting noise into the GPS signal bands but by mimicking the GPS signal. You don't need much power and can use an antenna array to point at planes like radar systems do. Using an encrypted code would totally prevent someone from broadcasting a fake signal because the receivers would not lock onto it and would instead lock onto the weaker, correct signal. Although encrypted M-code has just come out so I doubt Ukraine has access to it. Maybe NATO countries will have access but that's not the reality for Ukraine now.
- sudosysgen 5y ago
  Encrypted GPS jammers/spoofers just use replay attacks. It's very effective.
  - throw0101a 5y ago
    I would think that the encryption would prevent replay. Galileo's (proposed?) system certain seems to: * https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-1/ https://berthub.eu/articles/posts/galileos-authentication-al... Based on: * https://datatracker.ietf.org/doc/html/rfc4082 https://datatracker.ietf.org/doc/html/rfc4082
    - sudosysgen 5y ago
      Naive replay attacks of course won't spoof because of encryption. However, by replaying, it will be harder for the receiver to find the actual good signal amongst masses of inauthentic ones. If you want to spoof via replay you need to do it subtly and progressively - think by only a few ms, and it only works for a specific target. But that's not what I'm talking about here.

beecafe 5y ago

Not exponentially, that would be 2^X

wildzzz 5y ago

That's why RF loss equations use dB instead of ratios or percentage. GPS is anti-jam in nature due to it's spread spectrum method but a wideband jammer could make it difficult for a receiver to build the link. Jamming mitigation includes things like using highly directional antennas and smart receivers that can recognize jammers and null them out dynamically. Additionally there is a new encrypted M-code that allows military users access to a much harder to jam signal. A smart jammer works by not just putting noise into the GPS signal bands but by mimicking the GPS signal. You don't need much power and can use an antenna array to point at planes like radar systems do. Using an encrypted code would totally prevent someone from broadcasting a fake signal because the receivers would not lock onto it and would instead lock onto the weaker, correct signal. Although encrypted M-code has just come out so I doubt Ukraine has access to it. Maybe NATO countries will have access but that's not the reality for Ukraine now.

sudosysgen 5y ago
Encrypted GPS jammers/spoofers just use replay attacks. It's very effective.
- throw0101a 5y ago
  I would think that the encryption would prevent replay. Galileo's (proposed?) system certain seems to: * https://berthub.eu/articles/posts/galileos-authentication-algorithm-part-1/ https://berthub.eu/articles/posts/galileos-authentication-al... Based on: * https://datatracker.ietf.org/doc/html/rfc4082 https://datatracker.ietf.org/doc/html/rfc4082
  - sudosysgen 5y ago
    Naive replay attacks of course won't spoof because of encryption. However, by replaying, it will be harder for the receiver to find the actual good signal amongst masses of inauthentic ones. If you want to spoof via replay you need to do it subtly and progressively - think by only a few ms, and it only works for a specific target. But that's not what I'm talking about here.