Applied Cryptography: Protocols, Algorithms, and Source Code in C

I'm currently reading this book based on a recommendation. I really enjoy Schneier's writing style; he covers complex material in the most easy-to-follow manner. He explains each of the protocols detailed in the book at as numbered-list sets of actions between actors, and writes just enough about each topic for the reader to develop a strong high-level understanding. The book covers a range of topics, including many common cryptographic protocols, algorithms, and real world implementations. The breadth and specificity of topics covered is quite wide and varied - everything from common concepts like man in the middle, various one-way hashing algorithms, and public key algorithms, to more esoteric concepts, like zero-knowledge proofs, Ohta-Okamoto identification, or even how Kereberos works - is covered in the text.

There are two kinds of cryptography in this world: cryptography that will stop your kid sister from reading your files, and cryptography that will stop major governments from reading your files. This book is about the latter.