Tempest LCD: Playing songs from your LCD monitor with a radio

It's far worse than just being able to listen to music, with the right receiver and software you can decode the image from the monitor. Here's a quick overview. https://hackaday.com/2020/05/14/tempest-comes-to-gnu-radio/

I have verified that it works with my equipment (alarmingly well), though higher resolutions are harder to get a clear image out of. It even works with multiple monitors in close proximity, you just have to select the right parameters. Having an appropriate antenna helps avoid interference and improve the quality.

Relatedly, making the monitor itself emit the sound (might not be very loud or audible depending on the model) was discovered accidentally in this article: https://news.ycombinator.com/item?id=8856829

THIS is what I want to see more of. These fun hacks like this are why I got into programming to begin with. Computers these days has gotten so dreadfully dull.

Nice. I wonder if something like this has been ever used to exfiltrate data from some air gapped computer.

Some years ago I tried the FM transmitter via GPIO hack for the raspberry pi. The range was surprisingly high, around 100m. First google result. https://linuxhint.com/turn-raspberry-pi-fm-transmitter/

Nice to see someone else had one of my stray day dreams and implemented it. Albeit the version I thought of was a bit more malicious. In principle, if you know the frequency that a TV network broadcasts on, you could shape an that when broadcast happens to be coincident with a wifi packet. There was about a decade long window between when wifi was adopted to when analog TV was phased out where you could have tricked a TV station into transmitting some hack over a wide area.

Also worth noting the tempest trick should work in reverse. If you have a composite video to HDMI converter, whatever radio signal is on the video component should translate directly to pixels on screen. The hacky mans SDR.

Making nearby radios play music is a very old hack:

https://adwaterandstir.com/2017/05/30/play-daisy/

I wonder if you could play PCM audio with this technique. I'm sure it would be very low fidelity, but it would be cool if you could make out a human voice.

Reminds me of this watch I used to have way back in the day, maybe late 90's... It had a little eye and you would put it in some kind of programming mode and the eye would read the signals on the screen. If I recall correctly it looked a lot like this, just flashing lines on the screen.

Very cool! Although I'm curious about this part

> slowly change the frequency it's tuned to until you hear the sound. You might have to run the command a few times until finding the right frequency.

I don't really know much about this stuff, but shouldn't it be possible to calculate the frequency?

That’s really neat, I recall having a computer in the late 90s (maybe 2000?) with some cheap speakers next to the monitor. When scrolling text you’d get static in those speakers, presumably for the same reason (well, the earlier CRT example of this craziness)

I remember doing something like this with a CRT monitor way back in the early 2000s.

It might be possible to train a neural network on the RF emissions vs the image displayed and make it able to reconstruct the image based on the RF emissions. Might be blurry and noisy but worth a try!

Eh, wait. Tempest for Eliza works on LCD monitors too. I tried it with xvidtune to match the settings and the tune worked perfectly, and I did this over 10 years ago.

If we link an AM receiver with a machine learning model, we should be able to train the model to recognize patterns on the monitor.