Cryptography Reference
In-Depth Information
than spoken. Originally, these telephone codes had a small collection of two-
letter codewords, which eventually grew to three-letter code words. These were
subsequently adopted for wireless where early one-part codes grew into two-part
codes in later implementations.
By 1917, the Germans were using trench codes, which evolved into enci-
phered code, as we shall see later. Ultimately, when the Americans joined the
fray, they too adopted trench codes. Moreover, they had a brilliant cryptolo-
gist at their disposal, named Parker Hitt, who had worked as a Signal Corps
instructor. In 1915, Hitt published an influential booklet on cryptology called
Manual for the Solution of Military Ciphers . This was a practical manifestation
of how cryptology should be used in the field. Also, in 1913, Hitt rediscovered
the wheel cipher in strip form, and this led to the Navy strip cipher M-138-A
(see page 66 for comparison with Jefferson's original invention). In 1916, Major
Joseph O. Mauborgne put Hitt's strip cipher back into the intended Jeffersonian
cylindrical form, strengthened the alphabet construction, and produced what
came to be known as the M-94 device, which remained in service until the early
part of World War II.
Britain did not have a formal cryptology bureau. However, with interception
of German cryptograms, they quickly saw the need for one. A group was put
together by Sir Alfred Ewing, the admiralty's director of naval education. They
initially operated out of Ewing's oQce at the admiralty, but as the group grew
and their activities increased, they were moved into Room 40 of the Admiralty
Old Building. They became legendary as the Room 40 Group for their remark-
able cryptanalytic feats. In [131, Chapter 9], Kahn devotes an entire chapter to
them.
One of the major intelligence coups of the Room 40 Group occurred in 1917.
They had intercepted a telegram sent by the Germans over Swedish and Amer-
ican cables routed through Britain. When deciphered, it indicated that the
telegram was from the new German Foreign Minister, Arthur Zimmermann, to
the German embassy in Mexico City. It proposed to the Mexican government
that they invade the United States to reclaim territories lost in the 1848 war.
Germany was offering military assistance. This was an insane move since Mex-
ico could not possibly have the capacity to attack the United States under any
circumstances. The Room 40 Group saw the provocative nature of the tele-
gram, but ultimately the Zimmermann Telegram , as it went down in infamy,
was handed to the American ambassador to Britain on February 23, 1917. Of
course, the Americans were outraged, especially when Zimmermann admitted
the validity of the telegram. It contributed to the United States' declaration of
war against Germany that April.
The breaking of the Vigenere cryptosystem in the nineteenth century, cou-
pled with the advent of radio, and the looming First World War, in the early
twentieth century, brought into sharp focus the need for the development of new,
strong, and effective cryptosystems. Nothing much happened in this arena until
the dying days of World War I. It is worth noting that in the last year of World
War I, 1918, the Americans employed eight American Indians from the Choctaw
tribe to convey vital messages across insecure communication channels in their
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