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Comment by marcan_42 | Hacker News Reader

Just for my own amusement, I tried to come up with one he hasn't done. He's done HDD LEDs, screen brightness, switch LEDs, and keyboard LEDs (those are 4 independent papers). But he hasn't done camera LEDs!

So:

xxd -c 1 -p secret.txt | while read a; do for b in ${a:0:1} ${a:1:1}; do ffmpeg -y -f v4l2 -i /dev/video0 -t $((0x$b)) -f rawvideo /dev/null ; done; done

That leaks a file via the camera LED, PWMing it at 4 bits per pulse (16 different pulse widths), tested on my iMac. Can I get a paper now? :-)

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Heh, I think the keyboard LED trick was mentioned in Cryptonomicon iirc.

I created one that takes a mere 14 minutes to transmit 'hello' using a cd drive's movement: https://www.anfractuosity.com/projects/cditter/

"Anonymous Reviewer 2" stipulates that you include twenty citations to papers written by a single lab before your paper can be accepted for publication :^)

And at least one or two to his papers... Of course, he's anonymous!

> That leaks a file via the camera LED, PWMing it at 4 bits per pulse (16 different pulse widths), tested on my iMac. Can I get a paper now? :-)

Using (security) camera LEDs was already done:

* https://arxiv.org/abs/1709.05742

That's nifty!

Here's an alternative way to pass the bytes to ffmpeg, using hexdump (does not require vim) and `read -n1` (works in bash, but not in zsh):

hexdump -v -e '1/1 "%02x"' secret.txt | while read -n1 b; do ffmpeg -y -f v4l2 -i /dev/video0 -t $((0x$b)) -f rawvideo /dev/null; done

Yes maybe it's too many papers for too little material. But I do think even your the code you posted has some merit (even if not enough to stand alone).

The camera led is cool.

That might work in a noisy environment, but it draws attention visually, which might not be great. Also, (1) users tend to cover their cameras with tape or post-its, (2) why would a super secure endpoint have a camera if it wouldn't be on the network, (3) slight chance of being noticed on external/detached security webcam.

I went through the command trying to understand what you did and I realized I know nothing about using the CLI properly. So cool!

Keyboard LEDs using morse code has been done before in literature (Cryptonomicon). This is a nice modernization of the same approach.

This website is pretty cool sometimes.

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