It’s quite difficult to write a book in cryptography today and not talk about RSA, DSA, keys and the internet. Some make the effort to write about a bit of history, information theory and the arcane cryptosystems, but so far I’ve only found small references just for the sake of having it.
If you don’t understand the basics, the advanced may sound right, but faint. If you don’t have a hands-on experience with the basic technics, you’ll never get quite right the more advanced stuff, that’s why I strongly recommend this book. It was written in the sixties with the intent to describe basic cryptanalysis that was already obsolete at that time, specially after the WWII when cryptanalysis was boosted to a new level.
The book always explain the concepts by examples. Every chapter have a encrypted text that needs decryption and then the author goes on through the theory and practice of solving it. As the theory is worked out together with the practice you won’t loose any important concept, what always happens in mathematical texts (minimal theory, one useless example and lots of exercises).
It’s organized in five parts, one for each basic cryptosystem: direct standard alphabet (caesar cipher, rot13), generic monoalphabetic substitution (linear transformations), polyalphabetic substitution, polygraphic systems (matrices) and transpositions. All of which are, somehow still used in advanced cryptography, so the knowledge of how it used to work in plain text will definitely give you important clues on how to understand even the Rijndael (a.k.a. AES) algorithm.
I’m also building a tool kit to help me checkpoint my work throughout the book.
For Amazon US and International, follow this link: Elementary Cryptanalysis: A Mathematical Approach