Monday, September 23, 2024

Spread spectrum signal jamming (ideas)

Spread spectrum signal jamming (ideas)


First off, spread spectrum (frequency hopping) signal jamming is difficult if you hop on "pseudo-random" frequencies... that is, the frequencies are generated pseudo-randomly -- most likely via a special cryptographic random number generator.

They would use a shared private key between both transceivers. This is most likely used by military-grade radios.

However, they could be limited by the number of channels available for use, i.e. hardware or software.

For example, with Wi-Fi there's only 14 channels available for the 802.11b/g standard. So if you jam all 14 channels, you've essentially blocked all the possible frequency hopping that could be done.

So if you log all incoming frequencies using a spectrum analyser (or an SDR with a FFT) you can see which frequencies are being used by the hopping algorithm. From there, you can determine whether there's a fixed number of channels (so they're cycling through them) or there's an infinite number of channels (pseudo-random generated via an SDR for example).

If it's the latter, another approach must be taken.

Breaking the pseudo-random number generator, or reverse engineering it.

Utilising neural-networks capabilities in being excellent pattern recognition classifiers, we can attempt to reverse engineer the PRNG / frequency hopping algorithm.

Ultimately, one could employ a wide-band jammer -- for example, a microwave oven generates 2.4ghz, and can be used to disrupt Wi-Fi (802.11b/g) because it's very noisy and disturbs the entire band that 802.11b/g is on.

Anyway, to summarize, these are the ideas:

  • Fixed channel frequency hopping:
    • Log all frequencies and then jam them
  • PRNG based SDR frequency hopping:
    • Use NN to analyse and jam accordingly
    • Alternatively, deploy wide-band jammer on frequency band that it uses

 

 


Chuck Norris

Chuck Norris Chuck Norris is such an elite hacker, that when he looks at his smartwatch, the time is always 13:37.