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Stray WiFi Signals Could Let Spies See Inside Closed Rooms (sciencemag.org)
sciencehabit quotes a report from Science Magazine: Your wireless router may be giving you away in a manner you never dreamed of. For the first time, physicists have used radio waves from a Wi-Fi transmitter to encode a 3D image of a real object in a hologram similar to the image of Princess Leia projected by R2D2 in the movie Star Wars. In principle, the technique could enable outsiders to "see" the inside of a room using only the Wi-Fi signals leaking out of it, although some researchers say such spying may be easier said than done. Their experiment relies on none of the billions of digital bits of information encoded in Wi-Fi signals, just the fact that the signals are clean, "coherent" waves. However, instead of recording the key interference pattern on a photographic plate, the researchers record it with a Wi-Fi receiver and reconstruct the object in a computer. They placed a Wi-Fi transmitter in a room, 0.9 meters behind the cross. Then they placed a standard Wi-Fi receiver 1.4 meters in front of the cross and moved it slowly back and forth to map out a "virtual screen" that substituted for the photographic plate. Also, instead of having a separate reference beam coming straight to the screen, they placed a second, stationary receiver a few meters away, where it had a direct view of the emitter. For each point on the virtual screen, the researchers compared the signals arriving simultaneously at both receivers, and made a hologram by mapping the delays caused by the aluminum cross. The virtual hologram isn't exactly like a traditional one, as researchers can't recover the image of the object by shining more radio waves on it. Instead, the scientists used the computer to run the radio waves backward in time from the screen to the distance where wave fronts hit the object. The cross then popped out.
Placing the receiver directly in "the shadow" of the target object is a nice neat experiment, but wouldn't work in a real-world room. RF bounces all over the place like a box full of mad cats. Until they work out a way of differentiating the reflections from the primary, at all possible angles simultaneously, this is just an interesting hobby project.
I'm behind 7 walls lol no way to get through.
2013: http://m.slashdot.org/story/188149
2009: http://m.slashdot.org/story/125417
How long until someone else "discovers" the same thing again?
Don't let them catch you with your pants down!
What this is really showing is that they have worked out how to make an array antenna and composite that data to "see" what is blocking RF signals which is normally metals. I think you would be hardpressed to identify if a person was standing in the room. Still interesting though.
Anons need not reply. Questions end with a question mark.
What is next? They can use "light waves" to detect a cross placed in a room? Its like magic and stuff!
I distinctly remember some researchers use something similar to see through walls years ago.
It was even posted on here.
Yeah here it was: See thruogh walls with Wi-fi.
Video too .
A more recent (2015) one with motion
This can be done in most regions without having to install multiple routers and repeaters right now for most people. If you look at your available wirelss signals, you on average will see 3 or more. Most modern neighborhoods have enough routers and wireless devices that the only thing preventing the above is.......Nothing at all apparently.
It will give you very fuzzy "pictures". Lots of work for uncertain and marginal benefit. Nice for a research paper or some bullshit way to get defense research money.
Even with expensive equipment most are unable to locate interfering radio signals.
With all this technology and wiretapping, why are the criminal organizations not turned off?
They basically took a CT scan (computed tomography) using radio waves instead of x-rays.
Tomography has been around for over 80 years. It's why there's no lens when you have a traditional x-ray taken. You just fire the RF rays in a uniform direction (in this case the single WiFi course acts as a point source with all rays radiating radially), and capture them using a flat photographic plate (or in this case, by moving the WiFi receiver around on a plane). What they're doing isn't even as sophisticated as a CT scan because without moving the RF source as well, they can't capture 3D information.
One of these days, they will invent glass windows to see inside a room. Oh, the horror.
Sounds a little more fancy in the implementation, but using wifi as a passive radar isn't a new idea.
https://www.extremetech.com/ex...
If this were true it could possibly get rid of MRI's.
Not for the first time, just for the first documented time..
You can build an imaging radar at pretty much any frequency you want, as long as "some" of the power goes through the walls. WiFi is fine. The real challenge is modeling (and removing) the propagation effects of the walls and obstacles.
WiFi signals make a dandy radar illuminator: they're moderately wide band, particularly if you use all the channels available.
With today's technology, it would be like looking through one of those wavy frosted glass windows. You can easily distinguish moving objects through the window, probably see arms and legs but probably not resolve features.
With sufficient computational horsepower and sufficiently sophisticated transmitter/receiver arrays (lots of elements to get lots of independent looks), you could probably do it.