Can Digital Photos Be Trusted?

Given those rather large blind spots, some scientists are taking a completely different tack. Rather than try to discern after the fact whether a picture has been altered, they want to invisibly mark photos in the moment of their creation so that any subsequent tampering will be obvious.

Jessica Fridrich of SUNY Binghamton works on making digital watermarks. Watermarked data are patterns of zeros and ones that are created when an image is shot and embedded in its pixels, invisible unless you look for them with special software. Watermarks are the modern equivalent of dripping sealing wax on a letter-if an image is altered, the watermark will be "broken" digitally, and your software will tell you.

Watermarking is currently available in one consumer product, Canon´s DVK-E2 data-verification kit. This $700 system uses proprietary software and a small USB plug-in application to authenticate images shot with Canon´s pro-level cameras. It would seem ideal for news organizations: Photo editors (or anyone needing to authenticate) plug in the device, click on an image, and the software alerts them when a photo has been altered. Most digital news photos will be tweaked, of course, to adjust hue, saturation, contrast and brightness-editing procedures that were traditionally conducted in the darkroom-and then saved as a new file, but if the editor suspects funny business, he can compare the unaltered original with the altered copy and find out exactly how much it deviates.

The Canon kit won´t prevent self-made controversies, such as National Geographic´s digitally relocating an Egyptian pyramid to fit better on its February 1982 cover, or Newsweek´s grafting Martha Stewart´s head onto a model´s body on its March 7, 2005, cover, but it would have caught, and thus averted, another journalism scandal: In 2003 photographer Brian Walski was fired from the Los Angeles Times for melding two photographs to create what he felt was a more powerful composition of a British soldier directing Iraqis to take cover. Still, many media outlets remain dismissive of verification technology, putting their faith in the integrity of trusted contributors and their own ability to sniff out fraud. "If we tried to verify every picture, we´d never get anything done," says Stokes Young, managing editor at Corbis, which licenses stock photos. As damaging mistakes pile up, though, wire services and newspapers may change their attitude.

Meanwhile, work is progressing at Fridrich´s lab to endow photos with an additional level of security. Fridrich, whose accomplishments include winning the 1982 Czechoslovakian Rubik´s Cube speed-solving championship, is developing a camera that not only watermarks a photograph but adds key identifying information about the photographer as well. Her team has modified a commercially available Canon camera, converting the infrared focusing sensor built into its viewfinder to a biometric sensor that captures an image of the photographer´s iris at the instant a photo is shot. This image is converted to digital data that is stored invisibly in the image file, along with the time and date and other watermark data.

The application for a police photographer is obvious: If challenged in court, the image, camera and shoot are verifiable, the entire system secure. Unfortunately, the world of justice is the Dark Ages to academia´s Renaissance. The FBI has a special Digital Evidence Section and is funding authentication research, but federal rules of evidence don´t require verification of digital images other than by the photographer or someone else at the scene, let alone a secure photography system, and there´s been little effort to change them. "Most criminal courts are technically illiterate," says Grant Fredericks, a forensic-video analyst with forensic-systems maker Avid Technology. "They don´t have the tools and experience to deal with advanced technology."