Kahn: The Codebreakers

July 14, 2011

The Codebreakers
The Story of Secret Writing
David Kahn (Scribner, 1967)
1181 p.

These notes originally written 23 October 2005.

David Kahn’s The Codebreakers is an outstanding survey of the history of cryptography from the origins of the subject up to the Second World War. Kahn is thorough, and though the details occasionally threaten to overwhelm the narrative, for the most part the writing is clear and engaging.

Despite the fact that it attempts to cover the entire history of the subject, the center of mass of the chronology lies somewhere around 1925 — that is, a large portion of the book is devoted to WWI and WWII. This is quite appropriate, as these were the periods when cryptography blossomed in complexity and interest. But even so, Kahn casts his net into some rarely explored corners: he does not neglect to discuss medieval cryptography (lovers of medieval polyphony will not be surprised to learn that the medieval passion for intricate puzzles also animated the art of secret writing), he devotes some pages to cryptography in non-Western societies, and he gives an in-depth discussion of the U.S. intelligence services’ activities on the day of the Pearl Harbor attacks.

For me, the two best chapters of the book came after he had completed the main narrative arc. One chapter, called “The Pathology of Cryptology”, studies the pseudo-science wing of cryptology: all those efforts to discover ‘secret meanings’ in apparently non-secretive texts. The story of attempts to extract from the text of Shakespeare’s plays the confession that they were in fact written by Francis Bacon is hilarious and pitiful at once. And not only Shakespeare: the Bible (evidently Michael Drosnin’s The Bible Code is only the latest in a string of ill-considered efforts to turn Sacred Scripture into a crystal ball), Dante, Homer, and even Jonathan Swift have all, at one time or another, been made marionette by would-be decoders who — let us be generous — did not quite understand what they were doing.

Second, Kahn writes a chapter on the deciphering of ancient scripts, such as Egyptian hieroglyphics and the famous Greek script Linear B. This is a fascinating subject, well told (though I think that Simon Singh’s The Code Book, which treats the same topic, is even better).

Anyone, however, who wishes to read this book should understand that it is incomplete as to the modern history of the subject. This is no fault of the book, for it was written in 1967. The most significant topics missed are, first, the cracking of the Enigma cipher during WWII, which was not declassified until after Kahn wrote, and, second, the very significant developments in cryptology in the age of the computer and internet, especially the new paradigm of public-key cryptography. (In fact this new edition of the book does include a short new chapter on both of these topics, but the treatment is cursory. Simon Singh, in his aforementioned book, does a much more thorough and clearer job on these topics.)

In summary, then, I think this must be the book on cryptographic history, so long as you’re content to finish up in the mid-20th century.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: