Microsoft has won a patent for a digital-watermarking technology that could be used to protect the rights of content owners even when digital music is distributed without DRM protection. The technology, called "stealthy audio watermarking," inserts and detects watermarks in audio signals that can identify the content producer, "providing a signature that is embedded in the audio signal and cannot be removed," according to a filing with the U.S. Patent and Trade Organization (USPTO).
The application for U.S. patent 7,266,697 was filed May 3, 2004, by Darko Kirovski and Henrique Malvar, both of whom work at Microsoft Research. Malvar is a Microsoft distinguished engineer and managing director of Microsoft Research in Redmond, Washington, and Kirovski is a researcher there.