Friday, July 02, 2004

How to Spot Vanishing Commissars

Here's as good an excuse to plug the old alma mater as any other: it's just been announced that a Computer Science professor at Dartmouth has come up with a means for spotting doctored digital images.

"Seeing is no longer believing. Actually, what you see is largely irrelevant," says Dartmouth Professor Hany Farid. He is referring to the digital images that appear everywhere: in newspapers, on Web sites, in advertising, and in business materials, for example.

Farid and Dartmouth graduate student Alin Popescu have developed a mathematical technique to tell the difference between a "real" image and one that's been fiddled with. Consider a photo of two competing CEOs talking over a document labeled "confidential - merger," or a photo of Saddam Hussein shaking hands with Osama bin Laden. The Dartmouth algorithm, presented recently at the 6th International Workshop on Information Hiding, in Toronto, Canada, can determine if someone has manipulated the photos, like blending two photos into one, or adding or taking away objects or people in an image.


Farid and his students have built a statistical model that captures the mathematical regularities inherent in natural images. Because these statistics fundamentally change when images are altered, the model can be used to detect digital tampering.

"This technology to manipulate and change digital media is developing at an incredible rate," says Farid. "But our ability to contend with its ramifications is still in the Dark Ages. I'm always asked if this technology would stand up in a court of law." He explains that the simple answer is, "eventually." Farid predicts there will be skepticism and a great deal of scientific and legal debate. But eventually, he believes that some form of his technology or someone else's will be incorporated into our legal system.

Farid, whose research is funded by an Alfred P. Sloan Fellowship, the National Science Foundation and the U.S. Department of Justice, also works with law enforcement officials, government representatives, and corporate leaders on this issue of authenticating digital images.

"There is little doubt that counter-measures will be developed to foil our detection schemes," says Farid. "Our hope, however, is that as more authentication tools are developed it will become increasingly more difficult to create convincing digital forgeries."
Fark denizens and Weekly World News "journalists" now have something to fear.