There is no theory explained here. We assume you know what you are doing. For a good introduction to the concepts, try William Stallings, Cryptography and Network Security: Principles and Practice [STAL]. For a more detailed work, see Some Examples of the PKCS Standards by RSA Laboratories [PKCS-EX], an old but still useful guide. If all else fails, try reading the primary references we used.
You are assumed to have a reasonable knowledge of the basics of cryptography and public key encryption, and that you can program in the language of your choice to an advanced standard.