Rather than being a dry recitation of encryption and cryptanalysis schemes, Bauer provides a great deal of information about what actually goes wrong when one tries to construct a cipher that must be used under pressure by non-cryptologists, with plenty of historical examples to illustrate his points. And he discusses at some length the ways in which cryptanalysts can hope to unravel ciphers and codes too strong to be broken by standard methods. Much of what he has to say I had never seen in print before; some of it was brand new to me. Perhaps it helps that Bauer is German, and doesn't have to write with the uneasy feeling that NSA or MI-6 is looking over his shoulder at every line he writes. For example, his explanation of how Robert Murphy compromised an American cipher in WW II so badly that the Germans could read it easily is one that I think some American officials would probably still prefer not to have in print.
Despite comments by other reviewers and by Cryptologia, I think it requires a certain mathematical sophistication to absorb much of the material in this book. The math is not hard, but Bauer implicitly assumes a mathematical mindset and a familiarity with the terminology of pure mathematics that most college undergraduates don't have. So I wouldn't choose it as the primary text for a first course in cryptology, but I would certainly use it as a supplementary text. I know of no other book that contains so much material on the practical realities of cryptology.
In today's unsafe and increasingly wired world cryptology plays a vital role in protecting communication channels, databases, and software from unwanted intruders. This revised and extended third edition of the classic reference work on cryptology now contains many new technical and biographical details. The first part treats secret codes and their uses - cryptography. The second part deals with the process of covertly decrypting a secret code - cryptanalysis, where particular advice on assessing methods is given. The book presupposes only elementary mathematical knowledge. Spiced with a wealth of exciting, amusing, and sometimes personal stories from the history of cryptology, it will also interest general readers.