Use RF noise from VGA DAC to drive VHF TV | Hacker News Reader

Use RF noise from VGA DAC to drive VHF TV

bellard.org

117 pointsluu20 comments

I remember reading articles in the 90's about the TEMPEST technology (or some other name) where spy agencies could remotely eavesdrop on the output of your computer monitor, without a line of sight, from a truck parked on the street.

Example: http://www.sans.org/reading-room/whitepapers/privacy/introdu...

The general term for this (although a different concept to TFA) is http://en.wikipedia.org/wiki/Van_Eck_phreaking (as popularized in Cryptonomicon)

And if something typed doesn't show up onscreen (like a password), you can just eavesdrop on the keyboard. http://lasecwww.epfl.ch/keyboard/

I have a really cool story that I like to tell whenever something like this comes up. When I was a kid we had a very old 386 PC with a gigantic black & white CRT monitor, it was also very heavy (at least for a little kid). The computer was in a room adjacent to the living room where we had the TV and one day we started noticing lines of snowy noise appearing on the image on the TV. It seemed to be random and it was annoying as heck. One day I'm sitting on the computer doing something in good old MS DOS and the door is open, so I can work on the PC and watch cartoons at the same time, so double win for me!! It is then that I notice something really curious, the lines of noise on the TV are identical in shape and pattern to the ones on my monitor!!! Whoa!! I try writing long lines alternating with short ones and they also appear on the TV, and even though you couldn't discern specific letters you could definitely tell the spacing between the words. Mind blown!!! I think the culprit was in the unshielded cable running from the antenna in our roof to the TV, which happened to pass by the room with the computer in it. Anyway, I solved the noise "mystery" that day, but was subsequently banned from using the computer whenever the family was gathered watching TV. Talk about being ungrateful :)

On a similar note, the Raspberry Pi can be turned into a FM transmitter without additional hardware [0]. I remembered seeing another hack for a higher frequency that required a filter to be attached to the GPIO but I can't find the link.

[0] http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb...

There is an even better story about reading the screens of people using VGA cards at a distance by post processing the emissions coming from them [1]. Of course it is always fun to have your computer do things in interesting an unexpected ways.

[1] http://www.eskimo.com/~joelm/tempest.html used to be a page that had links to code that was used for reconstructing a vga image on your screen from picking up passive radiation, it has sadly gone away.

I think http://www.jammed.com/~jwa/tempest.html might be the same FAQ/info page (right author, anyway), although last updated in '99, and no obvious links to any code (except one link about sniffing CPU emissions, which is also bitrotted)

Playing music using monitor emissions: http://www.erikyyy.de/tempest/

See also the Braun Tube Jazz Ensemble http://youtu.be/Ouue59iY0Hs

This is interesting. I wish I understood what was going on. YouTube's automatic translated captions were little help.

He has guitar leads on his hands, and preset loops playing on each tv - for example, drum samples, tones - recorded on VHS. The audio is recorded as the video signal. Then, by putting his hands near the front of a television, the video signal is picked up by the guitar lead and played through the amplifier. He can play it by selecting which sample to play when.

Another video of him playing: http://www.youtube.com/watch?v=v5T2Q_wgoKg

And a video of his other project, Open Reel Ensemble: http://www.youtube.com/watch?v=AFM8UarAuVw

Nice catch. University of Cambridge paper I believe, which had a live demonstration. Its been a long time though.

No code here, but other technical details and some photos of what's possible in this paper http://www.cl.cam.ac.uk/~mgk25/ih98-tempest.pdf - possibly the one you were thinking of in your parallel comment.

May have been EckBox: http://eckbox.sourceforge.net/

We built the hardware back in college and played around with it a bit... back when people had CRTs.

This guy never ceases to amaze.

Allez Fabrice!

Fabrice Bellard, what a tease. Lots of awesome engineering work, no source code =(.

Well, not entirely fair. QEmu is open source.

Music played on a radio made from the RF emissions of the IBM 1401:

http://youtu.be/EPk8MVEmiTI

Guys, this is some of the coolest stuff I've ever seen. _These_ are the articles that keep me coming back to Hacker News.

Take a look at the .pgm images that generate those RF signals. I imagine that's the best we could hope to see leaking from some interstellar civilization's communications.

Reply on news.ycombinator.com