Digital Cameras Leave Unique 'Pixel' Fingerprints
http://it.ojp.gov/index.jsp

New research, conducted at Binghamton University, New York, can link
digital images to the camera with which they were taken. The research
analyzes the slight variations created by the image sensor in each
camera to uniquely identify pictures. Pegging a photo to an individual
camera essentially extends forensic document identification techniques
to the digital imaging area. The technology is being presented as
potentially useful in catching child pornographers. ''The defense in
these kind of cases would often be that the images were not taken by
this person's camera,'' Jessica Fridrich, the Binghamton University
engineering professor who oversaw the research, said in a statement.
''But if it can be shown that the original images were taken by the
person's cell phone or camera, it becomes a much stronger case.'' In
preliminary tests, Fridrich's lab analyzed 2,700 pictures taken by
nine digital cameras, with 100 percent accuracy. ''We already know law
enforcement wants to be able to use this,'' Fridrich said, in the
statement. ''What we have right now is a research tool; it's a raw
technology that we will continue to improve.''
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Comment: Copying and pasting photos can erase some of their
identification. Photos right out of the camera can be easily traced:
many cameras embed ID data in the photo which can be persistent if not
deleted. Modifying the photos with the effects palette within graphics
programs can erase more and distort pixelations. Photos can be reduced
to a dot or a pixel, stretched into a line, hidden within another
photo or an audio file, fragmented and reassembled, and so on. If you
want them to covertly photograph you, leave them unchanged.