Farid founds ‘digital forensics’

Hany Farid

With $100 Photoshop software and a little training, computer users can drastically alter digital photos, shedding a few pounds from a high school prom picture or removing a tumor from a medical image. While manipulated photos can be very difficult to detect, Hany Farid, associate chair of the computer science department at Dartmouth, is one of the first people to develop a method to find alterations in digital photographs.

Farid is a founder of the emerging field of digital forensics, which uses computer software to detect statistical differences in a photograph’s lighting, light reflections in eyes and other abnormalities that indicate that a photo has been altered. Detecting alterations is far more expensive and time consuming than altering a photograph, Farid said. Farid typically charges between $5,000 and $25,000 for his services and operators must be highly trained to use his software, he said.

“There is no magic bullet. It’s not simple,” he said.

After eight years of research and development, Farid delivered the first public digital forensics software to the Federal Bureau of Investigations last month. Law enforcement agencies provided some of the largest grants for Farid’s research as these agencies need a scientific method to determine if a photograph has been doctored for trials, he said.

Digital forensics has been especially important for child pornography cases since the Supreme Court ruled that digitally generated child pornography on the internet is protected as a form of free speech, Farid said. In his opinion, computer technology is not advanced enough to create a digital child that is indistinguishable from a real child by the naked eye, although in 10 to 15 years this could change. Many defense attorneys, however, claim that the children in digital pornography were computer generated to instill reasonable doubt in juries. Prosecutors have called on Farid several times to determine if images were digitally created.

The media is another potential market for digital forensics, he said. Reuters was recently faulted after one its photographers photo-shopped smoke on to a picture of bombed building in Beirut during the 2006 Lebanon-Isreali conflict and Newsweek was criticized for superimposing Martha Stewart’s head onto a model’s body for its cover.

Media policies toward digital manipulation vary widely, Farid said, adding that some news agencies, such as the Associated Press, strictly limit what can be altered in photographs while others are allowed to alter any images. Farid has had discussions with several news agencies about creating software that can quickly sift through their photographs to see if any alterations have been made, he said.

The number of doctored photos in circulation is on the rise, Farid said, although it is hard to determine the exact number of photographs in the media or on the internet that have been altered. Farid remains hopeful that the increase can be countered, highlighting the rise in awareness of digital manipulations and the technological improvement in digital forensics.

“Both sides are getting more sophisticated,” he said. “The Secret Service didn’t stop currency forgeries from being made, but they made it very costly and consuming. That is what we hope to do.”

Farid entered the field of digital forensics after stumbling upon a book called the Federal Rules of Evidence while waiting in the check-out line at the Massachusetts Institute of Technology library ten years ago.

“It said a digital photograph is admissible as evidence. They said basically we know this was not reliable,” Farid said. “I remember thinking this was stupid, and that was the start.”

Farid’s curiosity sparked the emergence of digital forensics.

“There was a huge need for this type of work,” Farid said. “We started working on this problem, and it just sort of resonated with people. All the pieces came together in the right way.”

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