So I caved and bought some books from Kyobo that were definitely not on thé usual channels and they have them in such a way that you can only read them from the app. So I downloaded them to my phone using the mobile app (the app doesn’t support Linux and is basically a Rootkit anyway) and copied the files from Android/data. They’re OEBPS by structure but come in regular folders, is it feasible to just zip them and import to Calibre?
Edit: I found a Calibre plugin for the DRM itself, so it’s more “How to make this folder a file”
Edit: so you can just zip them up and import as epub BUT the DRM plugin only goes as far as the metadata, the content itself shows up garbled. Don’t know how to get around that one…
I looked at the code using jadx, it can decompiler apks easily. I found out that the licence is obtained from the server, you will have to do the rest of the work yourself.
Look for Public Class LicenceManager and drmkey, you should be able to find the dycrption algorithm.
The url for the license is ddrm.kyobobook.co.kr/drmone/mobile/gateway/license.do
https://github.com/skylot/jadx
This is my guess I believe each book has a different key and to get access you need the license. Since I didn’t purchase the book I can’t get access to the decryption key. I hope I am wrong because this is annoying drm.
I looked up the url in a search engine and found this it might help, I believe this is a guy to locate the decrypted files on a pc: https://bibliothecamysticadedantalian.tistory.com/m/45
Also an old study on how to break DRM on Kyobo: https://seclab.skku.edu/wp-content/uploads/2018/04/NTMS_conference.pdf
If you ever manage to break it I will appreciate if you tell me how you did it. I believe extracting the decrypted book from a pc is the easiest method.