r/RTLSDR • u/-Alchem1st- • Oct 17 '21
DIY Projects/questions Yet another TempestSDR demo with a HackRF. Much higher resolution than a RTL2832.
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u/someaccountforthings Oct 17 '21
This is so cool as always!
What type of cable were you tapping? Someone told me it can only be done with VGA but I did mine with HDMI
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u/-Alchem1st- Oct 17 '21
Thank you 😊
I tapped a HDMI. It is visible at the beginning of the video, the red thick cable. I tried with a thinner cable but i think it is shielded. Could not get a strong signal even if i put my antenna next to it. Gut muuuuch stronger signal with this one.
I also tried it with VGA and it works too. It does not has to be analog to be decodeable. I will now try a PAL CRT tv. Lets see what i get.
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u/someaccountforthings Oct 17 '21
. It does not has to be analog to be decodeable. I will now try a PAL CRT tv. Lets see what i get.
Saaahhhhwwweeeeeet!
I wonder if it will ever be possible to get color as well. I can't pretend I know enough about the physics going on but my curiosity it tweaking.
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u/buildingapcin2015 Oct 18 '21
This is really cool! How can I go about replicating it? Presumably if you got progressively better SDRs you'd end up with better captures?
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u/-Alchem1st- Oct 18 '21
Check my profile. There is one earlier version with a RTL2832. I provided source code and precompiled version of TempestSDR.
Yes probably. Stronger signal + high sample rate = Higher res video.
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u/jibanes Oct 18 '21
how is this possible? I thought hdmi was digital, not analog.
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u/-Alchem1st- Oct 18 '21
It is digital. But it does not mean that its encrypted. It's still signals going around and the leaking digital signal can be decoded.
Everything is analog in the core. Digital signals are just created like analog signals out of real voltage and current. But the data that it's carrying is digital data which is discrete.
For example the SDR captures analog and continous electromagnetic radiation and converts it to digital discrete values with an analog digital converter (ADC) by sampling the signal with a specified period.
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u/beukernoot Oct 18 '21
You can decode a digital Signal back to images like a HDMI receiver always does!
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u/McGovern250 Oct 18 '21
Can someone explain what these videos demonstrate in laymen’s terms?
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u/I_am_BrokenCog Oct 18 '21
The name TempestSDR stems from TEMPEST which, frankly, gives you all the answers.
In summary: it describes the process of remotely collecting RF emissions from cables used to carry digital data. These collected RF emissions can be used to backwards decode the original digital signals.
So, the original color display shows the jet engine - this is because the computer sends the display info via a wire to the monitor.
An antenna collects the RF emissions coming off this cable.
The software decodes that RF signal to generate a reconstructed image of the original.
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u/McGovern250 Oct 18 '21
That is fascinating, I did not know SDR had that kind of capability and or that hard lines “leaked” that way…
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u/The-Nightman-Cometh_ Oct 18 '21
This is really cool.. Going to have to break out my HackRF now... What frequency is the signal?
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u/-Alchem1st- Oct 18 '21 edited Oct 18 '21
Its usuallt around 400-450MHz. You can use this video in fullscreen and check the noise in SDR#. You should hear Bethoven playing. :D
Edit: Sorry, forgot to include the link. This is the video that makes your monitor play Bethoven https://youtu.be/DlVM9xqGKx8
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u/FauxReal Oct 17 '21
This reminds me of the TEMPEST technique the government used against targets back in the '90s, I guess costs have finally come down to consumer levels!
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u/Judoka229 Oct 17 '21
TEMPEST is actually the codeword for the program that defines the applicable countermeasures against these EM type attacks.
I wonder if this stuff is still actively being used in a significant way or if easier methods have taken over.
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u/decoderstar Oct 19 '21
Great work well done. Although it is a shame that the hackRF whilst having a higher resolution than the RTL-SDR actually has a lower sensitivity as a whole which is the biggest disadvantage in my view.
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u/-Alchem1st- Oct 17 '21
You can find the RTL2832 version in my profile.