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Why don't they just install a background behind the subject that produces a checkerboard pattern? This is exactly why programs like Photoshop use a checkered ba

Why don't they just install a background behind the subject that produces a checkerboard pattern? This is exactly why programs like Photoshop use a checkered background to make it trivial to detect transparency in your images. Wouldn't that render the exploit this guy found obsolete?

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city41 15y ago
If it does make his exploit obsolete, then it also has a side effect of the TSA admitting that the backscatter machines have been ineffective for 2 (3?) years now. That is something they will never admit.
tsaoutourpants 15y ago
Not sure, it might actually make it harder to tell where the body ends and the checkerboard begins, because the resolution is so poor. Either way, this was but one exploit I found. :)
djb_hackernews 15y ago
Install a background? Photoshop? You do realize that the backscatter machines aren't taking a picture right? There isn't a "background" to change. It's basically an X-ray machine, throw some radiation, see what bounces back. I'll let you figure out why building a backing that is made up of different materials that reflect radiation in a checkerboard pattern won't work.
- georgieporgie 15y ago
  I'll let you figure out why building a backing that is made up of different materials that reflect radiation in a checkerboard pattern won't work. Uh. Why won't it work? From what I recall of the images, they're sort of gray-scale. The brightness of a body drops off as it falls away from the camera (i.e. the outline of your body is a darker gray than, say, your forward-facing bellybutton region), since, presumably, as we wrap around to the sides of your body, more energy is bounced out to the sides than to the 'camera'. So, I assume it's depicting the amount of radiation reflected back to the 'camera', right? So, if you make a checkerboard background of materials that bounce differing amounts of energy back (either due to composition of the tile or its angle), why wouldn't it work?
- snprbob86 15y ago
  The phrases "You do realize that" and "I'll let you figure out why" are condescending. The tone of your post is rude. Moreover, you're clearly the one who doesn't understand: The prior poster was proposing a checker pattern of reflective material on the background.

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city41 15y ago

If it does make his exploit obsolete, then it also has a side effect of the TSA admitting that the backscatter machines have been ineffective for 2 (3?) years now. That is something they will never admit.

tsaoutourpants 15y ago

Not sure, it might actually make it harder to tell where the body ends and the checkerboard begins, because the resolution is so poor. Either way, this was but one exploit I found. :)

djb_hackernews 15y ago

Install a background? Photoshop? You do realize that the backscatter machines aren't taking a picture right? There isn't a "background" to change. It's basically an X-ray machine, throw some radiation, see what bounces back. I'll let you figure out why building a backing that is made up of different materials that reflect radiation in a checkerboard pattern won't work.

georgieporgie 15y ago
I'll let you figure out why building a backing that is made up of different materials that reflect radiation in a checkerboard pattern won't work. Uh. Why won't it work? From what I recall of the images, they're sort of gray-scale. The brightness of a body drops off as it falls away from the camera (i.e. the outline of your body is a darker gray than, say, your forward-facing bellybutton region), since, presumably, as we wrap around to the sides of your body, more energy is bounced out to the sides than to the 'camera'. So, I assume it's depicting the amount of radiation reflected back to the 'camera', right? So, if you make a checkerboard background of materials that bounce differing amounts of energy back (either due to composition of the tile or its angle), why wouldn't it work?
snprbob86 15y ago
The phrases "You do realize that" and "I'll let you figure out why" are condescending. The tone of your post is rude. Moreover, you're clearly the one who doesn't understand: The prior poster was proposing a checker pattern of reflective material on the background.