You need the desktop Kindle application to download the book files to your computer. Use version 1.19 through 1.34 for the easiest workflow. Newer versions employ stronger DRM algorithms. 3. DeDRM Plugin
The KFX Input Plugin does not contain any cryptographic code to break Amazon’s DRM. Instead: kfx input plugin for calibre
KFX has advanced formatting features (fixed layouts, comic panels) that do not translate well to standard EPUB/MOBI formats. You need the desktop Kindle application to download
A proposed enhancement is integrating a to help developers map unknown tokens faster. kfx input plugin for calibre
Calibre will use the KFX Input plugin to decode the file structure and the DeDRM plugin to handle the encryption. The conversion engine will then build your new eBook file.