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CRT Eavesdropping: Optical Tempest

Posted by michael on from the tinfoil-house dept.

PortalCell writes "LED status monitors may potentially leak data in a few applications, but worse: Markus Kuhn has now revealed (pdf) that it's possible to read your monitor indirectly just by observing how the blue flicker lights up the room! Forget taping up LEDs or living in a metal box - now you might have to do without sunlight to be secure!" Hopefully people will also stop submitting the LED story now.

5 of 219 comments (clear)

  1. Interesting concept but... by ZaneMcAuley · · Score: 1, Interesting

    how practical/feasable/reliable is it? Wont data be missing if a shadow or a person walks in front of it and make it hard to put together?

    --
    ----- Whats wrong with this picture? http://www.revoh.org:1234/whatswrong
  2. On the other hand... by danro · · Score: 2, Interesting

    Considering the quality of the output, maby a funky wallpaper and transparent terminals might be enough for all the tin foil hat type persons out there...

    A _field_ test of this would probabli yield a even worse picture, methinks...

    --

    "First lesson," Jon said. "Stick them with the pointy end."
  3. Van Eck phreaking by ushac · · Score: 2, Interesting

    Wow, that's really neat. I wonder how good the results of this is compared to say van Eck phreaking (eavsdropping on the EMI emitted by the CRT-gun)?

    Regards / ushac

  4. Re:Knowing your enemy by PhotoGuy · · Score: 3, Interesting
    they will now be able to eliminate potential suspects just by looking at light that was leaked from their residences
    But isn't this exactly the same as the case where they used thermal imaging to determine a pot growing operation? I think that case was thrown out, as an invasion of privacy.

    I don't see how decoding blue light leaking from a residence would differ from decoding infrared radiation leaking from a residence.

    I'm all for catching bad guys every way possible, (and even for reducing the rights of the masses to do this) but given the current state of affairs, I don't think this would work without the same warrants required for other monitoring.

    Neat technology, though. One night, after seeing the neighbors TV glow flickering on their wall, I had thought about how it should be possible to monitor people's TV viewing habits, but spotting the patterns of illumination, comparing it to known broadcasts. Should be trivial to find the best match. Just one more thing for the paranoid conspiracy theorists to worry about. :-)

    -me
    --
    Love many, trust a few, do harm to none.
  5. Re:Knowing your enemy by DutchSter · · Score: 2, Interesting

    Yeah on the surface, it seems to be. There are a lot of misconceptions about that ruling. A significant part of the ruling was that SCOTUS declared that the government saying that they couldn't look at intimate details of your home (ie - are you growing pot in your underwear or in a body suit?), they didn't need a warrant. The court reaffirmed that "Such an approach would be wrong in principle because, in the sanctity of the home, all details are intimate details." (United States v. Karo, 468 U.S. 705).

    Interesting to note however, is that it is still a gray area as to whether stuff that is in "plain view" from the outside can be considered private. If I am correct, in order for this technology to work, they essentially need to be within line of sight of your monitor. To do this would require an open blind. That's the same as me (as police officer) walking by and seeing three teenagers drinking beer in the front window. Not only could you not accuse me of breaking in to look at you, I would have the right to inquire about whether underage drinking was occuring (since it was observed in plain view from a public place). Given that, I don't know that the thermal imaging case is 100% applicable because a large part of the technology is dependent on plain view.

    Now, having said that: You might have an affirmative defense in saying that such an evesdropping technology is not in the public domain. While anybody can walk by and see your underage beer party, its doubtful that Bill Public would have the resources to just walk by, pull out his imager and see what's going on.

    Am I unsure of what to say? Yeah pretty much, like anything else, this specific use of technology will be taken to the courts by one side or another. In the meantime, pull the blinds Mr. Tin Foil man :)