Change the block of pixels in the Jpeg at the upper right hand corner,
unrotated, and you'll change the encoding. Do it a couple of times and
I'll bet it's unpredictable enough to screw this method all too hell.
However, even if it doesn't let's see they used an example to identify
cameras, used in kidnapings.
I'm a kidnapper and want to provide proof that I've got the victim, I'm
not a photographer so I go to the local drug store, buy a blister
packed Polaroid, or Kodak 2mp resolution P&S with cash.
These cameras cost between $20 and $40 bucks, a factory in the orient
makes millions of them, every drugstore in America, Canada, and Mexico
probably stocks them, probably lots of other places as well. In fact
several different brands including generic store brands may even be the
same damn camera under the plastic cover. How does this narrow anything
down?
Now if the Kidnapper used his or her brand new Nikon D3 it might be
useful, but that seems pretty unlikely.
I think this is more likely to be intended to be used to prosecute
commercial child pornography, but almost everybody except the FBI knows
that the FBI is the largest supplier of high quality child porn, as a
byproduct of their sting operations.
Doug Franklin wrote:
Digital images contain their maker's mark
http://www.newscientist.com/article/mg20026826.200-digital-images-contain-their-makers-mark.html
By examining the minutia of adjacent pixel values in a photo, they
claim to be able to identify the model-specific demosaicing
algorithms. I'm guessing this can only be done from the in-camera
JPEG, since you wouldn't need to for the raw images. Not sure how
useful it actually is, since it identifies the model, not the
individual camera. But it's technically interesting, anyway, to a
geek like me. :-)
--
You get further with a kind word and a gun, than with a kind word alone.
--Al Capone.
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