Tempest: Transmit Radio Waves via a PC Video Card with No Extra Hardware
erikyyy.de
erikyyy.de
This software could be used to exfiltrate data from an "air-gaped" PC to a receiver. I suspect someone involved with this had a national security background.
....or, like me, they were simply not asleep during the 1990s when everyone and their dog remotely involved in information security became aware of Tempest, particularly via the publication of articles like "A Few Things on Van Eck's Method of Eavesdroping(sic)" in Phrack issue 46 (published 20 Sept 1994).[1]
This is interesting from a "dimensional expansion"/"dimensional collapse" perspective.
In other words, we have a computer monitor.
The screen, more specifically images on the screen -- are 2D entities.
Radio waves, on the other hand, could be considered 1D, or even 0D (time domain oscillations only), depending on one's perspective...
So, if what the article says works, we have this mapping of a specific patterned 2D screen image -- which maps to a note (a human hearable frequency) mapped to a much higher frequency 1D or 0D entity (the AM radio wave).
Anytime an apparent one-way mapping can be spotted -- I like to imagine if it could be reversed, and if so, what might be required to do that...
Reversed, this looks like a 0D/1D radio wave generating a 2D screen.
Well, we already have something like that... that's basically streaming YouTube videos over WiFi (2D screens gettting generated from 1D/0D information)... but that's still with an encoding method, compression, computer intervention, etc.
Perhaps there is something more fundamental there...
Old-time analog TV's used a radio (well, rf/electromagnetic spectrum, whether you call it "radio" or VHF or UHF or not...) signal only to create their 2D pictures without encoding or decoding, without computer intervention.
But, I don't know.
I think the whole idea of converting something in several dimensions to something in lesser dimensions, and then converting it back again -- has a whole lot of merits and applications -- thus far we've "discovered" TV and Computers and moving pictures of all sorts -- what potential applications will we find for this set of ideas in the future?
> If there are so many dimensions, why does it all fit on a SerDes? [0]
I can confidently tell both of you that dimension reduction from m to n is easy as long as you are happy to quantize (m-n) of the dimensions and have sufficient bandwidth in the remaining dimensions.
[0]: https://twitter.com/elonmusk/status/1701164151429579072
I don't think that's correct. Streaming data over WiFi it's like loading a painted portrait in a boat, rowing over the river and then unloading it in a different place.
What you're thinking is like reconstituting the portrait from the wave patterns made by the boat in the river. Which is possible and it's called Van Eck phreaking: https://en.wikipedia.org/wiki/Van_Eck_phreaking
You would of course need to know the exact pixel timings - which probably vary quite a bit between different manufacturers.
It's at least that old, I suppose it could be older.
And why doesn't it work for FM? Is it a software limitation or a hardware one?
Probably because the frequency range would need to be in MHz rather than KHz.
FM is normally transmitted at much higher frequencies (~ 100 Mhz rather than ~400 kHz). Your monitor pixel data will have components up at 100Mhz, but they'll be much smaller.
The math to generate an AM signal is fairly trivial (just multiply signal by carrier and re-quantize to the pixel clock). For FM, the math is much harder, although still doable.
There must be some hidden, universal...