This book is really good for beginners in cryptography. However, the most useful thing in the book is the source code, which can be used for programming your own crypto protocols. I would give this 5/5 rating.

This book offers a practical and relatively easy to read description of implementing cryptography algorithms, especially RSA, in software. Most books in the field are highly mathematical. This book covers all of the necessary mathematics, but also explains how to efficiently implement the mathematics in C. It covers many of the real-life issues in building security software. As a researcher in the field, I found the book very helpful.

Don't even try to do crypto routines in C/C++ without this book.

It will save you a lot of heartache.

Read it!

If truth in titling were a crime, someone would be in leg-irons over this one. This book should be entitled, "A Detailed Account of the Construction of a Large-Precision Number Library of the Sort that can be Used for RSA and Similar Cryptographic Systems, with a few Examples." The book fulfills this latter title exceptionally well.

The great majority of this book is a detailed, step-by-step account of the how the author constructed a C-language big-number library. It treats wrapping the C-libraries with C++ classes as a separate chapter -- nice touch. This treatise is thorough, well-written, and engaging. Nicely done. It is written from a mathematicians perspective, and its mathematical underpinnings may repel some programmers, but they need not fear. In the end the C-code is well-explained.

The only "cryptography" of note is a chapter on implementing RSA with the library. Indeed, the great majority of implementing RSA and similar ciphers is creating the big-number libraries. The RSA chapter is, fortunately, much more than a simple example. It is an excellent treatise of the pitfalls in implementing RSA. That is, RSA is more than a "simple example." If you are implemeting RSA with any big-number library, this chapter alone is worth the cost of admission.

There is a chapter on AES (Rijndael) cipher, but it is out of place here and an obvious paste-on, probably a last minute, hot-button item required by the publisher. It really has nothing you can't get from the original NIST documents on AES.

I'm willing to believe that the title and AES paste-on are the fault of the publisher, because otherwise Welschenbach did an excellent job -- lots of hard and careful work, well documeted. With a title-change, I'd give it a 5-star.

The question in the end is: Why would you want this book? Apart from general interest, the audiences that come to my mind are those who are constructing such libraries on their own, and those who need to use the software included with the book (on a non-commercial basis -- the software license prohibits commercial use).

This book will only be appealing to avid crypto fans. The book takes the abstract concept of contemporary algorithms and provides mechanisms for the user to contstruct concrete examples in C & C++ computer code. A rare advanced crypto book that also provides the reader with the mechanisms to explore the various aspects of contemporary advanced crypto ideas in programs. Welschenbach provides the boilerplate code for integrating these highly esoteric functions in C. Invaluable if you have both crypto knowledge and programming acumen.