Free Seizing the Enigma by David Kahn

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became ciphertext A. This reciprocity had the advantageof eliminating the need for any switch to shift from enciphering mode to deciphering and vice versa, thus precluding the error of enciphering a message in the deciphering mode. But it had the crypt-analytic disadvantage of yielding the knowledge of a second plaintext letter whenever a first was found. The double passage brought another advantage and disadvantage: it complicated the cryptosystem, but it meant that no letter could ever represent itself, a fact that might speed solutions by showing which possibilities could be rejected.
    In 1924, the firm got the German post office to exchange Enigmaenciphered greetings with that year’s congress of the International Postal Union. Later a book on cipher machines by an Austrian criminologist, Dr. Siegfried Türkel, gave the Enigma extensive coverage, including a detailed description of the various models, many photographs, and praise from the Austrian cryptanalyst and author Colonel Andreas Figl. But, no more than any other cipher-machine inventor of the time who had dreamed of getting rich by selling protection for businessmen’s messages, no more than Alexander von Kryha or Edward H. Hebern or Arvid Damm, did Arthur Scherbius make money. By the end of 1924, his firm still had not paid dividends.
    The situation, however, was changing. Behind the sandstone walls of the four-story headquarters of the Naval Command at Tirpitzufer 72–76, facing Berlin’s tree-lined Landwehr Canal, the cryptologic branch that had turned Scherbius down in 1918 was reconsidering the security of German naval communications. The reason was the shocking discovery that the British had been reading coded German naval messages for much of World War I.
    The first clue came from the fiery builder of Britain’s Dreadnought navy, the retired first sea lord, Admiral of the Fleet Sir John Fisher. In his
Memories
, published in 1919, he wrote:
The development of the wireless has been such that you can get the direction of one who speaks and go for him; so the Germandaren’t open his mouth. But if he does, of course, the message is in cypher; and it’s the elucidation of that cypher which is one of the crowning glories of the Admiralty work in the late war. In my time they never failed once in that elucidation.
    Subsequent indications were even more specific. In 1923, the official history of the Royal Navy in the war revealed various instances when intercepts had given the British an advantage. At the same time a dramatic and authentic story drew the attention of all to Britain’s cryptanalysis.
    In his best-selling
The World Crisis
, the first two volumes of which were also published in 1923, Winston Churchill, who had been the civilian head of the Royal Navy at the start of the war, revealed, in his flamboyant style and with some poetic license as to facts, the basis of Britain’s codebreaking successes:
At the beginning of September, 1914, the German light cruiser
Magdeburg
was wrecked in the Baltic. The body of a drowned German under-officer was picked up by the Russians a few hours later, and clasped in his bosom by arms rigid in death, were the cipher and signal books of the German Navy and the minutely squared maps of the North Sea and Heligoland Bight. On September 6 the Russian Naval Attaché came to see me. He had received a message from Petrograd telling him what had happened, and that the Russian Admiralty with the aid of the cipher and signal books had been able to decode portions at least of the German naval messages. The Russians felt that as the leading naval Power, the British Admiralty ought to have these books and charts. If we would send a vessel to Alexandrov, the Russian officers in charge of the books would bring them to England. We lost no time in sending a ship, and late on an October afternoon Prince Louis [of Battenberg, first sea lord, whose name was later changed to Mountbatten] and I received from the hands of