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jhowell · 05-13-2025, 08:12 AM

I took at look at the new BookFab Kindle Converter program to see what I could find out about how it works. There is a caveat in what follows that since I did not actually run the program I may have missed something. Even so, based on my findings I have decided not to install or use this product.

BookFab uses a clever hack to avoid the need to crack the latest KFX DRM. It obtains the customer's credentials and Kindle for PC registration info and then communicates with Amazon's servers pretending to be the latest version of Kindle for PC. However unlike the real app, when it requests a book for download it indicates that it only supports older KFX DRM that has been cracked since 2021. Surprisingly that actually works. Amazon supplies the files that make up the book and then BookFab uses included code from DeDRM and my KFX Input plugin to do the rest of the work.

While that method does work it has some significant problems.

First, it communicates with Amazon's servers in a way that the actual Kindle app would never do. Once Amazon catches on to the glaring difference between the supposed app version and its supported DRM level it will be easy for them to detect when it is being used. And it won't be long since they will look into it once this workaround becomes better known.

Second, they will know exactly which customers are using it. It only works because it supplies Amazon's servers with the user's Amazon account credentials. Amazon will know who is in violation of the their terms of service and they could decide to terminate accounts in order to send a clear message to others who might do the same. In contrast DeDRM does not communicate with Amazon and so its use is invisible to them.

Third, because it only works if Amazon actually responds with obsolete DRM, this hack will be very easy for Amazon to block. Once they do Bookfab customers will be left without a working product for however long it takes them to either find a new clever hack or actually defeat the latest KFX DRM. That could be quite a while.

05-13-2025, 08:12 AM	#2881
jhowell Grand Sorcerer Posts: 7,037 Karma: 91577715 Join Date: Nov 2011 Location: Charlottesville, VA Device: Kindles	I took at look at the new BookFab Kindle Converter program to see what I could find out about how it works. There is a caveat in what follows that since I did not actually run the program I may have missed something. Even so, based on my findings I have decided not to install or use this product. BookFab uses a clever hack to avoid the need to crack the latest KFX DRM. It obtains the customer's credentials and Kindle for PC registration info and then communicates with Amazon's servers pretending to be the latest version of Kindle for PC. However unlike the real app, when it requests a book for download it indicates that it only supports older KFX DRM that has been cracked since 2021. Surprisingly that actually works. Amazon supplies the files that make up the book and then BookFab uses included code from DeDRM and my KFX Input plugin to do the rest of the work. While that method does work it has some significant problems. First, it communicates with Amazon's servers in a way that the actual Kindle app would never do. Once Amazon catches on to the glaring difference between the supposed app version and its supported DRM level it will be easy for them to detect when it is being used. And it won't be long since they will look into it once this workaround becomes better known. Second, they will know exactly which customers are using it. It only works because it supplies Amazon's servers with the user's Amazon account credentials. Amazon will know who is in violation of the their terms of service and they could decide to terminate accounts in order to send a clear message to others who might do the same. In contrast DeDRM does not communicate with Amazon and so its use is invisible to them. Third, because it only works if Amazon actually responds with obsolete DRM, this hack will be very easy for Amazon to block. Once they do Bookfab customers will be left without a working product for however long it takes them to either find a new clever hack or actually defeat the latest KFX DRM. That could be quite a while.