Let's say I'm interested in building an app that uses encryption: an end-to-end email client and/ or server, a tarsnap competitor, or I just want to build a privacy conscious app (end-to-end encryption of user data, basically). How should I get started, would there be a reading list on cryptography besides the security reading list?

(And yes, I know the best way is to get a PhD building the thing, but I'm interested in learning nonetheless )