MUMBAI: Microsoft Corp 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 US Patent and Trade Organization (USPTO), says a report in PC World.

Microsoft currently has DRM (digital rights management) technology called Windows Media DRM that encrypts audio files and protects them from misuse or unauthorized redistribution. The company has traditionally been an outspoken proponent of using DRM to protect owners of digital content, though it said earlier this year it would consider selling DRM-free songs online after rival Apple Inc. struck a deal with EMI Group PLC to do so. Forensic digital watermarking technology can be used to prove who owns the content of the digital file by encoding a file with a unique digital signature. That means illegally traded songs could be tracked back to the original purchaser, allowing authorities to identify illegal sharers and serving as a deterrent. The technology could also be used to track files for royalty distribution. Apple has been inserting simple watermarks into digital audio files that include personal information about the purchaser on some files sold over iTunes so those files can be traced back to their purchaser in the case of unauthorized distribution, says the report.