At the heart of this is the iTunesDB file, the index that the iPod operating system uses to keep track of what playable media is on the device. Unless an application can write new data to this file, it won’t be able to “sync” music or other content to an iPod. The iTunesDB file has never been encrypted and is relatively well understood. In iPods released after September 2007, however, Apple introduced a checksum hash to make it difficult for applications other than iTunes to write new data to the iTunesDB file, thereby hindering an iPod owner’s ability to use alternative software (like gtkpod, Winamp, or Songbird) to manage the files on her iPod.
The original checksum hash was reverse engineered in less than 36 hours. Apple, however, has recently updated the hashing mechanism in the latest versions of the iPhone and iPod Touch. Those interested in using software other than iTunes to sync files to these new iPods will need to reverse engineer the hash again. Discussions about that process were posted to the public bluwiki site. Although it doesn’t appear that the authors had yet figured out the new iTunesDB hashing mechanism, Apple’s lawyers nevertheless sent a nastygram to the wiki administrator, who took down the pages in question.
