How to add DRM on epub programmatically?

Question 1

I added DRM with following things: if ePub is coming from server, make zip file password protected and inside HTML pages you can encrypt via AES-128. For images also you can encrypt but you need to add more code on your reader part.

if you are encrypting images, then all images must be decrypted before you load HTML page in web or browser.

Question 2

If you just want to protect your books from copying, then publish them through Amazon or Apple. As long as you don't select otherwise, those bookstores will wrap the books in DRM that allows them to be read only a limited number of devices belonging to the purchaser.

If you have some reason for wanting to worry about DRM yourself, then after carefully considering why on earth you'd want to, you'll need to find a vendor who can provide both the DRM technology and the reader (perhaps white-labeled for you) which knows how to read those DRM'd books. You see, DRM is useless unless there's a reader that can read the DRM'd books. And what's more, you need a back-end infrastructure to keep track of which devices belong to which person. There are vendors who provide such solutions. However, you'll end up paying them some of the money you were trying to save by avoiding Amazon or Apple.

The pricey Adobe solution mentioned by one commenter has the advantage that it is used by multiple bookstores/reading systems, including Kobo and Sony, so if you use it, then people buying your books can read them on any of these devices--albeit with an annoying step involving some software called ADE.

If for some strange reason you are thinking of building this entire infrastructure yourself, all I can say is, good luck.

More generally, even if you work through Amazon or Apple, it's well worth stepping back and thinking if you really want to do DRM or not. It's a natural human instinct to think, "By golly, I'm not going to let anyone steal MY book!!", but many of the people that might pirate a non-DRM'd book would not have paid money in the first place, so it's hard to say you're actually "losing" money. And someone who pirated the book might then Tweet or tell their friends about it and you'll end up selling more books than otherwise. Finally, someone who really wants the book without paying will crack the DRM anyway, as another commenter noted.