[gjkood]

If you want to do the heavy lifting in understanding Cryptography, almost all the relevant documentation can be found at the following resource.

http://csrc.nist.gov/publications/PubsFIPS.html

A lot of the hard (math heavy) stuff used in modern cryptography has been published almost a couple of decades ago and good books are available on Amazon. I usually just buy them used as you get very good deals for books that have been published several years ago.

I would recommend Bruce Schneier's 'Applied Cryptography, Protocols, Algorithms and Source Code in C'. I was surprised to see the 20th Anniversary Edition is out now.

https://www.amazon.com/Applied-Cryptography-Protocols-Algori...

The math involved uses a lot of number theory (prime numbers, prime factorization, modulo computations, chinese remainder theorem, elliptic curves, etc)

Once you get a basic understanding of the math, you will find out why it is hard to find the keys (if properly generated) through brute force computer attacks.