Monday, December 11, 2006

Forensic Watermarks in Mobile Devices

Continued from page 1

By Kate Greene

Cinea believes the solution lies in doing some of the computer processing before the video is downloaded. Then, when the video is sent to a mobile phone, Schumann says, the file contains a few extra kilobits of data that essentially point to the pixels that need to be changed in order to embed a watermark.

"It's conceptually easy," Schumann says, "but hard to do in practice." The researchers are trying to tweak the algorithm so that the watermarking data added to the file isn't excessive. "Bandwidth is precious," he says.

Some researchers don't see forensic watermarking technology being easily accepted by consumers. "In extremely dynamic, mobile media consumer environments, fingerprinting makes a lot of sense only if you want to alienate your customers," says Radu Sion, professor of computer science at Stony Brook University, in New York. The problem, he says, is that if you give a song or video to one of your friends, the forensic watermark that identifies you travels with it. What happens after it leaves your possession is out of your hands. Suppose your friend gives it to her friend, who puts it on a file-sharing site on the Internet, Sion says. The forensic watermark still traces it back to you. "Customers would now be reluctant to buy into such a technology," he adds.

There are also problems in keeping forensic watermarks from being removed, says Min Wu, professor of electrical and computer engineering at the University of Maryland. Wu researches methods for allowing watermarks to stand up to these attacks. If multiple people purchase the same video, for instance, and compare those files, they could detect the unique pixel alterations in each person's file. These could be averaged out to reveal a watermark-free video.

Securing forensic watermarks is still an active area of research, says Cinea's Schumann. Perfecting the technology is still a few years out: he expects to see the first field tests for forensic watermarking on mobiles in 2007 and 2008. But he's confident that within the next decade, technology can change the way content providers protect their digital goods and the way people share and use them.