Customer Reviews

Secret & Urgent: The Story of Codes & Ciphers

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I agree with Mark Riordan's concern about inaccuracies in Fletcher Pratt's book, but I recommend reading "Secret and Urgent" before reading Kahn's book, unless you are already familiar with cryptology. Pratt's book actually leads the reader step by step through the classic processes for breaking ciphers, from simple substitution up through Vigniere ciphers with disordered arrays with long keys. And he gives useful small examples of how to break codes. Kahn doesn't cover this elementary material. Someone who has read Pratt's book is in a much better position to understand what's hard and what's easy in trying to break such ciphers as Enigma, Fish and the M-209, and such codes as the various forms of "Purple".

This, in turn, helps the reader fit into context what the driving forces are behind such more recent ciphers as RSA and the NDES. In short: if you want to understand not only where cryptology is but also where it's been going, Pratt's little book (if the reader actually works through the examples) is a really good starting point.

This is a highly readable history of cryptology written around 1939. In fact, it was the book that inspired David Kahn to write his classic _The Codebreakers_. As Kahn later reported, he was disappointed to discover that much of what he had read in _Secret and Urgent_ as a child was false or exaggerated. I definitely recommend Kahn's book over Pratt's, though Pratt's may be slightly more approachable.