Microsoft has done the seemingly impossible and developed a digital watermarking system that is free of DRM (digital rights management) technology.
The `Stealthy Audio Watermarking' system, which has just been patented by the software giant we all love to hate, embeds a digital signature into the heart of the data file, but without - it is claimed - affecting the file in any way.
Personally, I doubt that the SAW system does not affect the playback of an audio track, but since this is aimed at relatively low bit-rate MP3 files, I also doubt punters will notice.
In its patent application, Microsoft reportedly says that SAW-encoding software will either look for gaps in the energy levels of a given track or create an uneven chess-board-like pattern, inserting data bits into areas of the file where they are unlikely to affect the sound.
The checking software then looks for a digital signature in the relevant files and can request authorisation for playback based on this information.
Now here's the bad news - 'cos the system depends on the actual structure of the music, stripping the watermark out will be almost impossible for most people.
According to newswire reports, whilst Microsoft has not announced plans to use the SAW scheme, the granting of a patent means it could so at any time and on a relatively short timescale.
It could even integrate the digital checking system for SAW into a Windows Vista update, but that, as they, say another entirely different can of digital worms...