We require a very basic command line utility which can take an mp3 file and embed a watermark (ie a short identification string/serial number) into the file without any adverse effect on the audio itself, and conversely extract the watermark from an MP3. The resulting MP3 will need to be playable in any standard MP3 player.
There are a number of papers on the web detailing how this can be achieved reasonably easily. Obviously this is *not* as simple as tacking it onto the end of the file, or into an ID3 tag, so it is important you have experience of this, or have research how this can be achieved.
The script needs to run in a Linux environment, but can be written in any reasonable language thats supported.