I've gathered all the book titles in this thread and created Amazon affiliate links (if you don't mind. Otherwise you still have all the titles together :-) )

A Pattern Language, Alexander and Ishikawa and Silverstein http://amzn.to/2s9aSSc

Advanced Programming in the Unix Environment , Stevens http://amzn.to/2qPOMjN

Algorithmics: the Spirit of Computing, Harel http://amzn.to/2rW5FNS

Applied Crytography, Wiley http://amzn.to/2rsULxS

Clean Code, Martin http://amzn.to/2sIOWtQ

Clean Coder, Martin http://amzn.to/2rWgbEP

Code Complete, McConnel http://amzn.to/2qSUIwE

Code: The Hidden Language of Computer Hardware and Software, Petzold http://amzn.to/2rWfR9d

Coders at Work, Seibel http://amzn.to/2qPCasZ

Compilers: Principles, Techniques, & Tools, Aho http://amzn.to/2rCSUVA

Computer Systems: A Programmer's Perspective, O'Hallaron and Bryant http://amzn.to/2qPY5jH

Data Flow Analysis: Theory and Practice, Khedker http://amzn.to/2qTnSvr

Dependency Injection in .NET, Seemann http://amzn.to/2rCz0tV

Domain Driven Design, Evans http://amzn.to/2sIGM4N

Fundamentals of Wireless Communication, Tse and Viswanath http://amzn.to/2rCTmTM

Genetic Programming: An Intrduction, Banzhaf http://amzn.to/2s9sdut

Head First Design Patterns, O'Reilly http://amzn.to/2rCISUB

Implementing Domain-Driven Design, Vernon http://amzn.to/2qQ2G5u

Intrduction to Algorithms, CLRS http://amzn.to/2qXmSBU

Introduction to General Systems Thinking, Weinberg http://amzn.to/2qTuGJw

Joy of Clojure, Fogus and Houser http://amzn.to/2qPL4qr

Let over Lambda, Hoyte http://amzn.to/2rWljcp

Operating Systems: Design and Implementation, Tanenbaum http://amzn.to/2rKudsw

Parsing Techniques, Grune and Jacobs http://amzn.to/2rKNXfn

Peopleware: Productive Projects and Teams, DeMarco and Lister http://amzn.to/2qTu86F

Programming Pearls, Bentley http://amzn.to/2sIRPe9

Software Process Design: Out of the Tar Pit, McGraw-Hill http://amzn.to/2rVX0v0

Software Runaways, Glass http://amzn.to/2qT2mHn

Sorting and Searching, Knuth http://amzn.to/2qQ4NWQ

Structure and Interpretation of Computer Programs, Abelson and Sussman http://amzn.to/2qTflsk

The Art of Unit Testing, Manning http://amzn.to/2rsERDu

The Art of Unix Programming, ESR http://amzn.to/2sIAXUZ

The Design of Design: Essays from a Computer Scientist, Brooks http://amzn.to/2rsPjev

The Effective Engineer, Lau http://amzn.to/2s9fY0X

The Elements of Style, Strunk and White http://amzn.to/2svB3Qz

The Healthy Programmer, Kutner http://amzn.to/2qQ2MtQ

The Linux Programming Interface, Kerrisk http://amzn.to/2rsF8Xi

The Mythical Man-Month, Brooks http://amzn.to/2rt0dAR

The Practice of Programming, Kernighan and Pike http://amzn.to/2qTje0C

The Pragmatic Programmer, Hunt and Thomas http://amzn.to/2s9dlvS

The Psychology of Computer Programming, Weinberg http://amzn.to/2rsPypy

Transaction Processing: Concepts and Techniques, Gray and Reuter http://amzn.to/

Types and Programming Languages, Pierce http://amzn.to/2qT2d6G

Understanding MySQL Internals, Pachev http://amzn.to/2svXuFo

Working Effectively with Legacy Code, Feathers http://amzn.to/2sIr09R

Zen of graphics programming, Abrash http://amzn.to/2rKIW6Q

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.