5 ms·

Our own encrypted communication is indistinguishable from noise, save for the initial handshake, which represents a detectable pattern, but mostly because we ha

Our own encrypted communication is indistinguishable from noise, save for the initial handshake, which represents a detectable pattern, but mostly because we happen to already have the full specification of the protocol handy. Additionally, entanglement can't be used for FTL communication, classical channel or not. So this, combined with the fact you don't need any quantum level mechanics for hidden communication that looks like noise... I'm unsure what the author is proposing and where that idea came to them.

thereddaikon 5y ago
That's definitely untrue. You can fire up an SDR and easily pickup encrypted radios from businesses and public safety. You can even classify the protocol they are using, P25, DMR etc based on the characteristics of the signals. They are definitely not indistinguishable from noise. Low Probability of Intercept radios can be harder to pick up because they use various techniques like frequency hopping but even then they don't blend in to the background.
- yourenotsmart 5y ago
  Knowing the popular protocols is an advantage you wouldn't have with "alien communication". Encryption in general doesn't try to hide itself, it just tries to hide the payload, so things like packet/frame structure, headers, handshake and so on can be relatively easy to pick up, because they're not hidden in the first place. Consider how unsophisticated the Enigma machine looks to modern eyes. Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Unlikely. Those are just few decades of difference on the same species with the same tech history.
  - zardo 5y ago
    > Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Definitely yeah
    - yourenotsmart 5y ago
      Well if all we need is just some bald confidence, I'll respond with a "Definitely nope".
      - unparagoned 5y ago
        Well I can confidently say you are wrong
        yourenotsmart 5y ago
        I can confidently say 2+2 is 5
  - thereddaikon 5y ago
    You said encryption is indistinguishable from noise without any further qualifications. That's simply incorrect. To address your other points, "Consider how unsophisticated the Enigma machine looks to modern eyes. Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Unlikely." Depending on how far you go back yes they would. Most communications today happens in the same frequency ranges they did decades ago. UHF is UHF. You bring up Enigma. I'm confident if Alan Turing were scanning the airwaves and heard a modern encrypted radio transmission he would immediately determine it was man made and some type of communication. He wouldn't have any hope of decrypting the signal or analyzing the packet structure. The mathematical theory behind modern encryption didn't exist yet let alone the compute power needed to crack it. "Knowing the popular protocols is an advantage you wouldn't have with "alien communication"." Normally projects like SETI will look for patterns and structure in the signals they detect. Nature can create some very complex transmissions and it can also create some very regular ones that are simple. But you rarely see both complexity and structure in a signal that isn't man made.
- dognotdog 5y ago
  Ultra-Wideband Spread-Spectrum can be undetectable, as the signal can be well below the noise floor in any given frequency band, and only knowing the right key will allow you to perform a convolution to lift the actual signal above the noise. Without the right key, all you'd see is noise, and you wouldn't even know there was a signal. see https://www.itu.int/itunews/manager/display.asp?lang=en&year=2004&issue=09&ipage=ultrawide&ext=html https://www.itu.int/itunews/manager/display.asp?lang=en&year...
  - sudosysgen 5y ago
    Detecting these kinds of signal is an area of active military research. The key is that if the signal comes from one direction, you can use multiple antennas and filter by time-delay/phase to find it even if it is below the noise floor. To this extent, there are methods to reliably detect signals 12dB under the noise floor, and as I said this is an area of active research and militaries are probably even further ahead.
    - dognotdog 5y ago
      That is quite interesting, and makes sense! The spread-spectrum signal is a psuedo-random, but same sequence for all receivers, while the noise varies and should cancel out. Though, if I am not mistaken, the laws of super-sampling hold in this case, and SNR is only improved by O(sqrt(N)) for N samples, so this approach will have practical limits as one has to place a very large number of receivers in range of the emitter (or do auto-correlations over a very long time window), with enough separation to make sure the noise isn't correlated anymore, if looking for a signal deep below the noise floor.
      - sudosysgen 5y ago
        I'm rusty on this but I do believe such a limit exists. However thankfully for this research it's about detecting radars, so thanks to the inverse square law there's a limit to how deep beneath the noise floor you need to look.
  - gus_massa 5y ago

thereddaikon 5y ago

That's definitely untrue. You can fire up an SDR and easily pickup encrypted radios from businesses and public safety. You can even classify the protocol they are using, P25, DMR etc based on the characteristics of the signals. They are definitely not indistinguishable from noise. Low Probability of Intercept radios can be harder to pick up because they use various techniques like frequency hopping but even then they don't blend in to the background.

yourenotsmart 5y ago
Knowing the popular protocols is an advantage you wouldn't have with "alien communication". Encryption in general doesn't try to hide itself, it just tries to hide the payload, so things like packet/frame structure, headers, handshake and so on can be relatively easy to pick up, because they're not hidden in the first place. Consider how unsophisticated the Enigma machine looks to modern eyes. Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Unlikely. Those are just few decades of difference on the same species with the same tech history.
- zardo 5y ago
  > Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Definitely yeah
  - yourenotsmart 5y ago
    Well if all we need is just some bald confidence, I'll respond with a "Definitely nope".
    - unparagoned 5y ago
      Well I can confidently say you are wrong
      - yourenotsmart 5y ago
        I can confidently say 2+2 is 5
- thereddaikon 5y ago
  You said encryption is indistinguishable from noise without any further qualifications. That's simply incorrect. To address your other points, "Consider how unsophisticated the Enigma machine looks to modern eyes. Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Unlikely." Depending on how far you go back yes they would. Most communications today happens in the same frequency ranges they did decades ago. UHF is UHF. You bring up Enigma. I'm confident if Alan Turing were scanning the airwaves and heard a modern encrypted radio transmission he would immediately determine it was man made and some type of communication. He wouldn't have any hope of decrypting the signal or analyzing the packet structure. The mathematical theory behind modern encryption didn't exist yet let alone the compute power needed to crack it. "Knowing the popular protocols is an advantage you wouldn't have with "alien communication"." Normally projects like SETI will look for patterns and structure in the signals they detect. Nature can create some very complex transmissions and it can also create some very regular ones that are simple. But you rarely see both complexity and structure in a signal that isn't man made.
dognotdog 5y ago
Ultra-Wideband Spread-Spectrum can be undetectable, as the signal can be well below the noise floor in any given frequency band, and only knowing the right key will allow you to perform a convolution to lift the actual signal above the noise. Without the right key, all you'd see is noise, and you wouldn't even know there was a signal. see https://www.itu.int/itunews/manager/display.asp?lang=en&year=2004&issue=09&ipage=ultrawide&ext=html https://www.itu.int/itunews/manager/display.asp?lang=en&year...
- sudosysgen 5y ago
  Detecting these kinds of signal is an area of active military research. The key is that if the signal comes from one direction, you can use multiple antennas and filter by time-delay/phase to find it even if it is below the noise floor. To this extent, there are methods to reliably detect signals 12dB under the noise floor, and as I said this is an area of active research and militaries are probably even further ahead.
  - dognotdog 5y ago
    That is quite interesting, and makes sense! The spread-spectrum signal is a psuedo-random, but same sequence for all receivers, while the noise varies and should cancel out. Though, if I am not mistaken, the laws of super-sampling hold in this case, and SNR is only improved by O(sqrt(N)) for N samples, so this approach will have practical limits as one has to place a very large number of receivers in range of the emitter (or do auto-correlations over a very long time window), with enough separation to make sure the noise isn't correlated anymore, if looking for a signal deep below the noise floor.
    - sudosysgen 5y ago
      I'm rusty on this but I do believe such a limit exists. However thankfully for this research it's about detecting radars, so thanks to the inverse square law there's a limit to how deep beneath the noise floor you need to look.
- gus_massa 5y ago