Tools to remove ebook DRM
There are many ebook DRM remover tools that work with MOBI, KFX, AZW, EPUB and PDF files. The most popular are:
- Calibre and DeDRM plugin – removes DRM from Adobe Digital Editions and Kindle DRM
- Epubor– provides a range of tools to remove DRM from Adobe Adept (Google Play ebooks), Amazon Kindle, Kobo, Nook, Sony & more
- EPubsoft ToolBox – removes DRM from all common ebook formats
- Tuneskit – removes Apple DRM (iTunes DRM removal)
You might ask why these ebook DRM removal applications are so successful. It’s simple: the above DRM security has been implemented as an afterthought (and usually rather badly), enabling applications to either plugin to (to access the content as it is decrypted or intercept the decryption keys) or pickup unprotected content that the system has directly cached to disk. This is nothing new – Elcomsoft pointed out the issues with Adobe PDF DRM and other ebook protection methods back in 2000. 20 years on and removing the DRM from ebooks is still trivial. See PDF Security issues and weak DRM implementations for further information.
Adobe’s standard security handler uses RC4 stream cipher, encrypting file content with a unique encryption key. The encryption key is encrypted and stored in the file’s encryption dictionary. Either the user password or owner password can recover the encryption key and decrypt the file content. Removing PDF Passwords covers this subject in more detail.
In 2009 Adobe Digital Editions was broken by i♥cabbages allowing users to remove the DRM protection from Adobe ebooks. They commented “There is very little obfuscation in how Adobe Digital Editions hides and encrypts the per-user RSA key, allowing fairly simple duplication of exactly the same process Digital Editions uses to retrieve it”. 5 years later, in 2014, Adobe released Adobe Content Server 5 which, in their own words, is “A more secure Digital Rights Management scheme to protect EPUB and PDFs from unauthorized viewing. The new hardened DRM solution uses multiple encryption layers with Adobe Licensing server having the control to change the mechanism of encrypted key generation.” Yet still ebook DRM removal products claim to remove it, proving that it does not matter how many layers of encryption you have if it is implemented poorly.
Publishers who implemented the latest edition were also in for a shock. Customers reported losing e-books from their libraries after having upgraded to the latest version.
Sadly, access being denied to PDF documents and ebooks after an Adobe update is not new. Companies that have implemented the Acrobat PDF DRM plugin have also had furious customers unable to access DRM protected PDF files since every time Acrobat is updated the plugin no longer works.