Seizing the Enigma by David Kahn Read Free Book Online Page A

agency got another lucky break. The third major codebook of the Imperial German Navy arrived in sodden condition in Ewing’s office. The captain of the torpedo boat S-119 had thrown it and other papers overboard in a lead -lined chest when he encountered a British squadron off a Dutch island; a month and a half later a British fishing boat hauled it up in its trawl. Soon the new codebook, the
Verkehrsbuch
, a five-numeral code
(Kaiser =
46786) used at sea by flag officers, was drying before Ewing’s fire.
    The new book too was used with a superencipherment, which was discovered the day the book arrived. Some days earlier the British had intercepted two almost identical German naval messages. One was encoded entirely in the
Magdeburg codebook
and so could be read by Room 40. A small part of the second was encoded in the newly found code. “It is never wise to mix your ciphers,” Ewing remarked. “Like mixing your drinks, it may lead to self-betrayal”This did. The
Signalbuch
gave the meaning of the coded portion of the
Verkehrsbuch
message; these German words could be looked up in the
Verkehrsbuch
to find the basic codenumbers, and comparison of those with the superenciphered codenumbers of the message revealed the formula for conversion.
    Thus, before the war was four months old, Britain had gained, mainly through means other than codebreaking, the ability to read the most secret intentions of its chief enemy’s navy.
    Nor did Britain’s cryptologic gifts from the sea end there. Later in the war the Germans changed their codes, but divers recovered the new ones and their superencipherments from U-boats sunk in the shallow waters around Britain. One of the most successful of these divers was Shipwright E. C. Miller, a pale, wiry young diving instructor. His most remarkable characteristic was a sangfroid in facing horrors that would have frightened off many other men. Once he investigated a German submarine sunk off the Yorkshire coast. She was lying on her side, and Miller found no point of entry. He rigged charges and blew off the top of the conning tower. As the water cleared, he saw the head of a dead German seaman rise above the ragged rim of the conning tower as if peering out. That didn’t stop Miller. In his bulky suit and spherical armored helmet, he clambered in. At once the imprisoned corpses crowded around him. He calmly tied them up with lanyards and pursued his exploration of the U-boat, stumbling through the narrow black passageway of the underwater tomb until, in a compartment aft of the officers’ quarters, he found a strongbox. This contained one of the new codes and some of its superencipherment keys.
    As the war progressed and the value of codebreaking became increasingly obvious, the staff of Room 40 swelled. Ewing recruited many members from Cambridge University, where he himself had been a professor of mechanical engineering, and from that university’s King’s College, of which he had been a fellow. Curiously, more of his recruits were classicists and linguists than mathematicians andscientists. One who proved most successful was a scholar of Greek named Alfred Dillwyn Knox, called Dillwyn.
    He was the second of four sons of the Anglican bishop of Manchester. At Eton he became close friends with the future economist John Maynard Keynes. At King’s he refused the homosexual advances of Lytton Strachey, the future author of
Eminent Victorians
, who had fallen in love with him.
    “Did I tell you,” Strachey wrote of Knox, “that he has a wonderful veil of ugliness that he is able to lower at any minute over his face? His method is, you see, to lure you on with his beauty, until at last, just as you step forward to seize a kiss, or whatever else you may want to seize, he lets down a veil, and you simply fall back disgusted. Isn’t it a horrid trick?” Witty, clever, always ready with a new limerick, Knox played first-rate bridge with unorthodox moves that more often than not succeeded. But