TEMPEST: A Signal Problem


TEMPEST is the covername used by the NSA and other agencies to talk about emissions from computing machinery that can divulge what the equipment is processing. We’ve covered a few projects in the past that specifically intercept EM radiation. TEMPEST for Eliza can transmit via AM using a CRT monitor, and just last Fall a group showed how to monitor USB keyboards remotely. Through the Freedom of Information Act, an interesting article from 1972 has been released. TEMPEST: A Signal Problem (PDF) covers the early history of how this phenomenon was discovered. Uncovered by Bell Labs in WWII, it affected a piece of encryption gear they were supplying to the military. The plaintext could be read over that air and also by monitoring spikes on the powerlines. Their new, heavily shielded and line filtered version of the device was rejected by the military who simply told commanders to monitor a 100 feet around their post to prevent eavesdropping. It’s an interesting read and also covers acoustic monitoring. This is just the US history of TEMPEST though, but from the anecdotes it sounds like their enemies were not just keeping pace but were also better informed.

[via Schneier]

12 thoughts on “TEMPEST: A Signal Problem

  1. “Their new, heavily shielded and line filtered version of the device was rejected by the military who simply told commanders to monitor a 100 feet around their post to prevent eavesdropping” :D thats a simple and effective solution ;)

  2. Tempest is actually a technical standard by which electronics are secured against radiological intelligence gathering methods aka RINT. In specific the methodology employed here is van eck listening. It annoys me that people call it tempest anything when tempest is the security standard itself and utterly unrelated to the science or the application of it in these situations. There is a great doc from USENIX a couple years back about how to pick up emissions off of digital cables running to LCDs and why it’s actually easier to do on an lcd than on a crt. Fun app though. Always loved eliza… the only problem is … for some reason programmers and specifically hackers all name their apps eliza. It’s wierd.

  3. Having guards secure a 100ft perimeter around the device would not be effective with the use of directional antennas, unless I’m missing something here.

  4. One creepy thing I heard the NSA can reconstruct an image from a unshielded monitor though they need to be very close.
    On side note the RFI emissions were how they used to get altairs to play music back in the 70s.

  5. I’m searching(said someone)tempest fenommena thru pc power supply where the wattage is huge ( about 200 watts).Soon coming to hackaday!Tune 69O khz am band!

  6. I have posted some links to research publications relating to tempest in this topic (should be the 1st post). Can anyone tell me how come my post did not appear?

  7. Just a gripe:

    Why do you always link to your own posts when referring to old projects? It’s just an extra click to see the actual project and it’s really annoying.

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