Book: The Codebreakers by David Kahn


A detailed history of cryptology

David Kahn
The Codebreakers: The Story of Secret Writing
Scribner, 1996 (originally published in 1967)
ISBN: 0-684-83130-0
$70 (routinely discounted and used copies seem to run around $30)
984 pages (main text)

Not that much needs to be said about The Codebreakers. It is a long and detailed history of code and cipher making and breaking from Ancient Egypt up to most of the interesting developments of the second world war. Though codebreakers (cryptanalysts) get pride of place in the book's title and often have the more exciting job, there are lots of interesting code-makers (cryptographers) in the book. This revised edition has an additional short chapter at the end that includes information that wasn't available to Mr Kahn when the original edition was published, notably about the Polish-British efforts to decipher the messages encrypted with German Enigma machines during the second world war.

The reason that not much needs to be said about the book is that if you're a serious geek about ciphers and codes, you'll want to read this long book regardless of its few flaws. If you're only an ordinary crypto geek or even just somewhat interested in the subject, Simon Singh's very excellent and much more portable book The Code Book will do just fine. If you've read that book and want to know more, this is the book.

The Codebreakers begins with a detailed account of the use of the decipherments (codenamed Magic) of the Japanese code called Purple which was used before and during the second world war. The Japanese declaration of war on the U. S. (which was really just a message that seemed to break off negotiations) wasn't delivered to President Roosevelt by the Japanese ambassadors (there were two) until after the attack on Pearl Harbor. But Roosevelt had already seen it when they brought it.

Following that chapter, there are 17 chapters of the history of cryptology. The really interesting stuff starts in the Renaissance and there's a lot about the first and second world wars. There's also some information about cold-war codes and ciphers. Then there's a chapter on the history and bureaucracy of the National Security Agency, which isn't especially interesting. Following that, there are 7 rather miscellaneous chapters that are of varying degrees of interest. They rather have the feel of articles that weren't originally written for the book. The one about the history of cryptology in fiction isn't especially interesting. The one about codes used by businesses (both legal and criminal) is. The one about deciphering messages from outer space can probably safely be skipped. The final chapter that brings the book more nearly up to date is reasonably good but too short. For example, the discussion in it of Alan Turing's "bombes" is hardly longer than the Wikipedia article on them.

For those who are keen enough on cryptology to read the book, there's a lot of detailed information in it and Mr Kahn's prose is generally serviceable. For example, the actual methods of cryptanalysis used on some relatively simple ciphers are given. There are also some fascinating historical tidbits. For example, Thomas Jefferson invented a cipher machine with a mechanism pretty much identical to one introduced by the U. S. Army in 1922. And the famous German Enigma rotor machine was in fact a variation on a commercial cipher machine. The first person to build a useful rotor machine was an American, Edward Heburn, who built one in 1918. There are also fascinating stories of cryptanalysis affecting history. At least some of Rommel's success in North Africa seems to have come because for a large part of the war he was reading the decoded dispatches of the American military attaché in Cairo. And it seems that the battle of Midway was in large part a victory of cryptanalysis.


If I had been Mr Kahn's editor, I'd have suggested italicizing a few foreign words and phrases, but that's a very small thing. And a better translation of the title of Georges Seurat's famous painting would be "Sunday Afternoon on the Isle of La Grande Jatte" (p. 724).

Posted: Mon - April 9, 2007 at 04:51 PM   Main   Category: 

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