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That link goes to the ACM Digital Library, where the paper is behind a paywall. Oddly, it is also available on the ACM SIGMOBILE site without a paywall: https://www.sigmobile.org/mobicom/2015/papers/p90-aliA.pdf

If I am understanding this thing correctly, WTF...they are figuring out keystrokes by looking at the variations on a WiFi signal caused by the movement of human fingers during typing, which change how the signal propagates!?

Note that the computer you are typing on does not even have to be using WiFi. Heck, you would not even need to be using a computer. This should work if you are using an old manual non-electric typewriter.




People are mostly water, and the 2.4Ghz frequency is absorbed by water (the molecule makes a convenient antenna). That is why it is used in microwaves and why microwaves don't heat dry things well.

So people are really good attenuators of the 2.4Ghz signal and mimo routers in particular are pretty good at localizing where attenuation is happening. That combination makes a WiFi base station a good hardware platform for tracking humans.

As soon as my LimeSDR system arrives I'm looking at trying to replicate some of these results.


Has anyone replicated them yet?


Is each antenna directional, or do routers only gain directionality with multiple antennas? I'm amazed that they can get such precise beamforming with only four or six antennas (maybe they didn't even have that many antennas in 2013.) Admittedly I'm more familiar with beamforming as a sonar concept than as radar.

edit: I just read the MIT paper, and it's using ISAR. My advisor would be ashamed of me for not realizing that... Still, as the number of antennas continue to increase for better directionality, the wifi radar could even become effective on stationary targets. Soon we'll all be dressed like F-35s to hide from our routers.


I like the idea of 'stealth ware', although recognize it would be something of a tin-foil hat type fashion.

I'd be happy if I can add a 'human motion / location detector' I've got ideas for a spotlight system that provides light for you when you walk up to a dark porch.


I watched the video but it's really weirding me out that the CEO paints his fingernails black


It's actually stealth paint to protect him from these kinds of attacks ;)


1994 called, it wants its The Crow T-shirt back.




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