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How to remove LCP DRM from epub files? (slrpnk.net)

submitted 1 year ago by archenemy@slrpnk.net to c/piracy@lemmy.dbzer0.com

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I have been searching for a concrete book for a long time and finally saw it's been offered as an epub loan on my local library, which uses LCP DRM (Thorium Reader or something like that).

The code to remove it was itself removed from the DeDRM calibre plugin because of DMCA, but then there's https://www.notabug.org/uhuxybim/DeDRM_tools-LCP, a fork that adds it back. The thing is: I can't get it to work. I've tried older versions of calibre as seen on obscure italian threads about this fork.

I've tried running it in debug mode to see where it's not working and it seems like it fails to detect that this concrete epub i'm providing has DRM and it just adds it to the calibre library as-is.

Before I dive into the code and try to extract the relevant bits to a simpler CLI utility, does anybody know how to make this work?

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[–] r3nder@beehaw.org 5 points 1 year ago* (last edited 1 year ago)

First, I should note that I haven't come across (Readium?) LCP before - so I don't have experience with this particular method for DRM - I do however like to play with these sorts of things and have definitely come across some similar methods, etc.

I found a similar tool on GitHub which may help you to better understand what the process is for figuring out something like LCP: lcp-decrypt. I'm not sure how fresh your knowledge is on encryption - but it would help to have some knowledge of the process you're trying to reverse engineer.

If you happen to find a sample with of non-copyrighted material that has some sort of encryption you'd like examined, I'd be happy to have a look for educational purposes.