EPub print & picture protection

Hi all,

I've recently exported an InDesign file as an epub3 - fixed lay-out book. But when I open this file in iBooks or another reader, I can simply export every single image as a png file... Probably there will also be other security and access options I've not seen yet.

I'd like to protect this file so it can only be read on the system, without any other possibility. How do I create such an epub file?

Thanks,

Bart