Codes and ciphers. Julius Caesar, the Enigma and the Internet (Q2761405)

It has been the author's aim to introduce the non-specialist ``to a number of codes and ciphers, starting with the ancient and elementary and progressing, via some of the wartime cipher machines, to systems currently in commercial use''. He has tried -- successfully as I think -- a middle way between avoiding mathematics entirely and to assume familiarity with the full ``panoply'' of mathematical ideas, techniques and symbols: In the main body of the text, the mathematics including mathematical notation, is kept to a minimum; further details and explanations are provided in the mathematical appendix (28 pages); to understand this part, mathematics up to about the standard of the English A-level is generally sufficient, and in a few cases the reader is referred to a more advanced work. NEWLINENEWLINENEWLINEMany examples and problems (with solution in the appendix) help the reader to test his understanding. Caesars ciphers, other simple and polyalphabetic systems, jigsaw ciphers, playfair and book ciphers are explained in the first 7 chapters. The solutions to these ciphers are described in detail: for monoalphabetic substitutions (on 27 pages), for the book cipher (on 14 pages), and for the Vigenère cipher, in which Kasiski's test is used. NEWLINENEWLINENEWLINECryptographic remarks and recommendations on which system to use under which circumstances are included. The one time pad (with rather a plausibility argument than a proof of the security) gives rise to treat the problem of producing random or pseudorandom numbers and letters. The explanation and analysis of the Enigma, the Hagelin and the SZ42-cipher machines with their analysis takes 51 pages; a 12-point Mini-Enigma is used to indicate possible attacks in detail. Public key systems such as the Diffie-Hellman key exchange system and RSA (10 pages), DES (5 pages), PGP and Elliptic Curve Cryptography are the modern systems described in the last two chapters. NEWLINENEWLINENEWLINEThis very well-written book will appeal to anyone interested in the history of cryptography, but it gives information on the presently used systems as well. It was a pleasure to read.