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RichFelker's profile
Rich Felker
Rich Felker
Rich Felker
@RichFelker

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Rich Felker

@RichFelker

Yeah, I do @musllibc, FOSS & infosec stuff. But now is not the time for a mostly-/only-tech Twitter feed.

musl-libc.org
Joined March 2014

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    1. whitequark‏ @whitequark Apr 23

      you have to actively prevent digital circuits from emitting radio waves. that's what the FCC part 15 subpart B is talking about. "unintentional radiators".

      1 reply 3 retweets 14 likes
      Show this thread
    2. whitequark‏ @whitequark Apr 23

      now spoofing GPS, yes, that is pretty serious. FCC will come and kick your ass too, but meanwhile you're going to seriously affect a lot of infrastructure nearby. this is a growing threat, mostly represented by truck drivers trying to work around fleet surveillance

      1 reply 2 retweets 27 likes
      Show this thread
    3. Rich Felker‏ @RichFelker Apr 23
      Replying to @whitequark

      Not sure, but I think it's possible to make a highly spoof-resistant (not jam-resistant of course) GPS receiver using multiple antennas.

      1 reply 0 retweets 0 likes
    4. whitequark‏ @whitequark Apr 23
      Replying to @RichFelker

      you can make a spoof-resistant GPS receiver, and you can even make a jam-resistant GPS receiver (within reason), but the issue is that a) most vendors don't bother doing basic sanity checks b) it's impossible to tell just by looking at the device c) shitty chipsets are everywhere

      2 replies 0 retweets 3 likes
    5. Rich Felker‏ @RichFelker Apr 23
      Replying to @whitequark

      Jam-resistant sounds really really hard due to the low signal strength. With a single point of jamming transmission there may be correlation-based approaches with multiple antennas, but with N independent noise sources...

      2 replies 0 retweets 0 likes
    6. Robert Ou‏ @rqou_ Apr 23
      Replying to @RichFelker @whitequark

      IIUI jam-resistant is possible as long as the malicious interference *) is not sufficiently correlated with any of the existing GPS Gold codes (so signal processing can still separate the real signal out) and *) does not cause the receiver to saturate

      2 replies 0 retweets 0 likes
    7. Rich Felker‏ @RichFelker Apr 23
      Replying to @rqou_ @whitequark

      Obviously a quality jammer would use the PRN codes, something like a random linear combination of the different sequences in different phases.

      1 reply 0 retweets 0 likes
    8. whitequark‏ @whitequark Apr 23
      Replying to @RichFelker @rqou_

      that's why I said "within reason". most jammers are cheap shit that's little more than a PLL and a PA

      1 reply 0 retweets 0 likes
    9. Rich Felker‏ @RichFelker Apr 23
      Replying to @whitequark @rqou_

      These cheap USB VGA things could easily make a good jammer based on the above though.

      1 reply 0 retweets 1 like
    10. whitequark‏ @whitequark Apr 23
      Replying to @RichFelker @rqou_

      easily accessible? yes. able to confuse most (completely unhardened) GPS receivers on market? yes. good? no

      2 replies 0 retweets 0 likes
      Rich Felker‏ @RichFelker Apr 23
      Replying to @whitequark @rqou_

      I was talking about making something that would jam a hardened receiver. Cheap SDR should be able to do that. Off-the-shelf jammer, maybe not.

      3:30 PM - 23 Apr 2018
      1 reply 0 retweets 0 likes
        1. whitequark‏ @whitequark Apr 23
          Replying to @RichFelker @rqou_

          if you're targeting a hardened receiver chances are you can afford a less crappy $50 SDR anyway, so this isn't really changing much

          0 replies 0 retweets 1 like
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