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I'm looking for a good way to encrypt ePub files. DRM is a too expensive option and not really needed: so good encryption will do the job but I'm not sure what are the standards/the way to go.

I get 'clean' unprotected ePub files which I can encrypt serverside. Then they can be downloaded with an iOS client. If I put the decrypt logic in the app, it will be unsafe, right? The user may not have access to the clean ePub file.

When working with an encryption key, it also have to be downloaded by the client, so unsafe too, right?

What's a right way to do this? For example: how is Spotify doing this?

CodesInChaos
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Milan van Schaik
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    You can't implement secure DRM, especially if it's in software. Who could have guessed. All those DRM solutions use a bunch of obfuscation and hope that nobody figures it out, i.e. they rely on security-through-obscurity. – CodesInChaos Nov 21 '14 at 12:15
  • If you are going to do the protection yourselves you will spend a lot of money on good obfuscation so at the end you may find out that using built in DRM solution will be cheaper and you will not need to maintain it. – Ladislav Mrnka Nov 21 '14 at 14:31
  • EPUB is a zip file. Maybe you can add a password during the zip. Here's a Q discussing the zipping: http://stackoverflow.com/questions/22620183/creating-epub-with-a2x-versus-zip/22631549#22631549 – Paulb Nov 23 '14 at 13:50
  • you may try this. [https://stackoverflow.com/questions/40299463/how-to-integrate-epub-file-in-own-ebook-reader-application-using-expressplay-sdk/43445213](https://stackoverflow.com/questions/40299463/how-to-integrate-epub-file-in-own-ebook-reader-application-using-expressplay-sdk/43445213) – yangJie Sep 04 '17 at 12:30
  • @Milan van Schaik have you found any way for above problem? – Bhagyashri Jul 29 '20 at 05:42

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