Tales From The Black Chambers

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By choice, cryptographers are an unsung and anonymous lot. In war and peace they labor in their black chambers, behind barred doors, dispatching sheets of secret symbols and reading encoded messages from the innermost councils of foreign governments. Few tales have leaked from those rooms.

Yet cryptographers have at critical moments affected the tide of history, for better or for worse, far more than some of the legendary heroes known to every schoolboy. On occasion American officials have blundered badly with codes and ciphers. On other occasions American cipher experts have shown brilliant flashes of imagination that lone will live in the sparse annals of cryptography.

Such unsung heroes were on Admiral Chester Nimitz’s intelligence staff in the Pacific at a highly critical moment in the spring of 1942. Radio monitors were intercepting a heavy volume of traffic from all elements of the Japanese fleet. Some of the messages were deciphered, and it became increasingly evident that Admiral Isoroku Yamamoto (who one year later was to die because a deciphered message had pinpointed the route of his airplane flight) was planning the biggest naval operation of the war. Nimitz had scant forces to oppose such an operation.

The key question at Pearl Harbor was Yamamoto’s target, knowledge of which was crucial to the planning of any effective counterstrategy. The deciphered messages referred to the target only as “ AF .” Was AF Midway ?Nimitz thought so but couldn’t be sure. Was AF Pearl Harbor itself? Admiral King, Nimitz’s superior back in Washington, thought so. How could AF be identified?

At this point Nimitz’s intelligence staff evolved a simple but ingenious plan to bait the Japanese into revealing the target themselves—and the heart of the plan was a unique exercise in cryptography. An encoded message was sent to the American commander at Midway, ordering him to send back a fake message in the clear . This message was to state only that the water-distillation system for the atoll had broken down. The plan showed a delicate sense of judgment; if Midway was indeed AF , the water supply on the island was of military significance; yet the information about the distillation system was fairly routine, might well be sent in the clear, and thus would not arouse the suspicions of Japanese intelligence monitors. Midway dutifully transmitted the message.

A few days later intelligence officers at Pearl Harbor deciphered a Japanese transmission noting that AF was low on water.

Nimitz himself later noted that effective intelligence was a key factor in his victory over a vastly superior force. Knowledge of the target enabled him to move three carriers to the scene in time to surprise Yamamoto. The intelligence ruse was a striking innovation in cryptography. Nimitz’s staff used a message from Midway in the clear to lure Yamamoto into revealing the identity of his target in code . History has seldom noted such triumphs of codes, or ciphers, or the men who manipulate them. We shall never know the countless times that, thanks to cryptographers, vital messages have been transmitted in complete secrecy. A successful cryptographer is far more reticent about revealing his legerdemain than a Houdini ; he may want to use the same system again, and the course of a nation may depend upon it. In the history of American cryptography only one man has talked, perhaps in vengeance when the doors of his beloved black chamber were abruptly closed by government order. Yet despite their bars and bolts, the doors of those chambers beckon invitingly. Most of us, from the time we developed a secret language for our childhood club or wrote enciphered messages to our first love, have found fascination in codes and ciphers. Americans watched enthralled as Marlene Dietrich, in Dishonored , played a series of piano chords, thus transmitting the disposition of enemy troops in a musical cipher—despite the fact that only one real musical cipher has ever been developed, by English writer Philip Thicknesse, and it was unsatisfactory because information couldn’t be fashioned into anything that sounded like a tune. Detective literature abounds in the use of secret ciphers (remember the chilling moments as Sherlock Holmes unravelled the secret of the Dancing Men?), and on television a criminal or a government agent frequently uses an “unbreakable code” to achieve his despicable or laudable goal.

Despite our fascination, we Americans have until recently been reluctant to use codes and ciphers in official dealings and frequently have bumbled in our attempts. Perhaps there is something about secret writing that runs cross-grain to the necessary openness of a democracy.