December 24, 2009, 11:01 AM —
Amazon sells content for the Kindle in an ".azw" format, some of which is has DRM (digital rights management) technology, which prevents a file from being transferred to an unauthorized device.
But one blogger, who goes by the handle "I love cabbages," with a heart to designate "love," developed a program called "Unswindle" that can convert books stored in the Kindle for PC application into a different file format that can then be imported to another device.
"Primarily, I view DRM as an unnecessary restriction on legitimate freedoms, such as fair use of copyrighted material," the hacker said in an e-mail exchange. "Laws such as the DMCA [Digital Millennium Copyright Act] turn those restrictions into injustice by making their circumvention illegal."
Amazon's proprietary ".azw" format is derived from a format called Mobipocket, which came from a French company of the same name that Amazon purchased, "I love cabbages" said in the e-mail exchange. The Mobipocket format is still relatively popular.
A hacker named "igorsk" discovered that books in the Mobipocket format with DRM could still be read on the Kindle. Igorsk developed a tool that generated a "PID," or a unique device-specific encryption key, used for Kindle e-books that enabled Mobipocket books with DRM to be read, "I love cabbages" said. That enabled people to buy Mobipocket books from other vendors and read them on their Kindles.
Then, another hacker named "darkreverser" wrote MobideDRM, which could remove the DRM from Mobipocket files. Used in combination with Igorsk's tool, the two programs have allowed people to remove DRM from Kindle books.
But Amazon changed the encryption scheme when it released the Kindle for PC program, a free application that allows people to read Kindle titles on their PCs. Instead of using a single device encryption key for Kindle books, each book is now encrypted with a different key.
"Everything else is the same though -- MobideDRM works, you just need to figure out a different key for each book instead of a single key for every book," I love cabbages wrote.
What Unswindle does is grab that unique key for every book using Windows debugging APIs (application programming interfaces), I love cabbages said. "It then hands all of the actual hard work of actual decryption to darkreverser's MobideDRM".