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Files purchased through the iTunes Music Store are digitally protected so they can only be played on the computer where they were purchased from, or any legal iPod attached to the system.

FairPlay is Apple’s Digital Rights Management (DRM) technology used to protect music files bought from the iTunes Music Store. Files purchased through the iTunes Music Store are digitally protected so they can only be played on the computer where they were purchased from, or any legal iPod attached to the system.

However, there’s a GPL-licensed program called Hymn which is able to remove this DRM protection from files purchased via iTMS (iTunes Music Store) with no quality lose. This little jewel can be downloaded from:

http://hymn-project.org

and it’s available both in source code and pre-compiled for Mac OS X and Windows.

Hymn requires an iPod to be attached to the system in order to extract the keys used to encrypt the music files content. Thus, the easiest way to use Hymn is attaching my iPod to my PowerBook, downloading hymn’s binary image for Mac OS X from the web site, launch hymn and then drop into it the protected music files (Hymn sports a nice Cocoa interface),.

A protected music file has a “.m4p” extension meaning the content is protected. When dropping a file with a “.m4p” extension into Hymn, the file will be decrypted and a corresponding, unprotected “.m4a” file will be stored at the same location. This new “.m4a” file can be played on any system which supports the AAC encoding audio format. Any Mac OS X computer or iPod will do.