...an encyclopedic work of a very high standard. ... More than merely a book that describes cryptographic codes, scattered throughout this book are pictures and biographies of key personnel responsible for progressing the world's knowledge and use of codes, as well as exercises and problems ... This is, without question, an excellent book. ... the depth of the knowledge, the provided mathematical background, and simply the correctness and consistency of symbols throughout, all give indications of the quality and amount of work that has gone into this book. ... the book is probably the best book currently for the range of users. -IACR book reviews, May 2010 It is an excellent book with unique features including more than 370 exercises... -The Cryptogram, Vol. LXXI, No. 5, September-October 2005 This is an interesting, entertaining and well-composed book. ... It was a good idea to collect all exercises in the Appendix G as it makes reading easier for a general reader, while enabling university and college faculty to use the book in teaching courses in cryptography and cryptoanalysis. To conclude it is worth mentioning that all sections of the book are decorated with beautiful quotations. -Mathematical Reviews It is full of engaging detail on the many personalities that have been drawn to this branch of applied mathematics. ... a self-contained guide to the subject covering material from basic arithmetic to the foundations of group theory and probability. ... Among books at the level, this one stands out for some of its vivid examples. Particularly enlightening is the discussion of quantum computing: rather than merely touching on the subject, Mollin provides a particularly illustrative and detailed example. -MAA Reviews, Dec. 2005 Richard Mollin has written many books ... on cryptography for readers at many levels. I found this to be his most approachable work, and perhaps one of his most educational. -SIGACT News