Novel Watermarking Process Protects Video Producers And Purchasers

"A number of digital watermarking techniques have been proposed in recent years, but none has fully addressed the problems of proving rightful ownership or protecting a customer's right to use the material," said Klara Nahrstedt, a U. of I. professor of computer science.

"The purpose of a watermark is to protect the owner's copyright," Nahrstedt said. "Without a careful design and proper requirements on the watermark, however, an attacker can easily manipulate the watermarked material and confuse rightful ownership."

To create a tamper-proof watermark, Nahrstedt and graduate student Lintian Qiao developed a watermark construction algorithm that combines a standard encryption function with part of the original video image. Because the resulting watermark is dependent upon both the original material and the encryption function, rightful ownership is easily determined.

"To prove ownership, both the original material and the watermark construction algorithm are required for the verification process," Nahrstedt said. "Therefore, manipulated watermarks are easy to identify and discredit."

The researchers' watermarking process also can be used to protect the rights of legitimate customers, an important feature not found in other watermarking techniques.

"Currently, sellers of video information have complete control over the watermarking procedure, and customers have no way to prove their rights to use the watermarked data," Nahrstedt said. "To provide proper protection to customers, the watermarking framework needs protocols that involve both owners and customers."

One such protocol, designed by Nahrstedt and Qiao, encodes a customer's unique identification into the owner's watermark at the point of purchase. This creates a unique watermark for each purchase, and ensures that only legal customers can prove their rights to use the material.

"The ideal watermark should be invisible, create minimal distortion and be extremely difficult to remove," Nahrstedt said. "The integration of our watermarking scheme with the customer's right protocols creates a robust framework that resolves rightful ownership and protects customer's rights."

Nahrstedt and Qiao described their watermarking process at the IEEE International Conference on Multimedia Computing and Systems, held June 28 through July 1, in Austin, Texas.