Cryptography Reference
In-Depth Information
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The Enigma machine, looking rather like a typewriter, was
battery-powered and highly portable. In addition to a key-
board, the device had a lamp board consisting of 26 stenciled
letters, each with a small lightbulb behind it. Each bulb in the
lamp board was electrically connected to a letter on the key-
board, but the wiring passed via a number of rotating wheels,
with the result that the connections were always changing as
the wheels moved. Thus, typing the same letter at the key-
board, such as AAAA..., would produce a stream of changing
letters at the lamp board, such as WMEV…. It was this ever-
changing pattern of connections that made Enigma extremely
hard to break.
In the winter of 1932-33, Polish mathematician Marian
Rejewski deduced the pattern of wiring inside the three rotat-
ing wheels of the Enigma machine. (Rejewski was helped by
photographs, received from the French secret service, show-
ing pages of an Enigma operating manual.) Before an Enigma
operator began enciphering a message, he set Enigma's three
wheels (four in models used by the German navy) to various
starting positions that were also known to the intended recipi-
ent. In a major breakthrough, Rejewski invented a method
for finding out, from each intercepted German transmission,
the positions in which the wheels had started at the begin-
ning of the message. In consequence, Poland was able to read
encrypted German messages from 1933 to 1939.
In the summer of 1939 Poland turned over everything—
including information about Rejewski's Bomba, a machine he
devised in 1938 for breaking Enigma messages—to Britain and
France. New methods developed during 1940 at Bletchley Park,
a British government establishment located north of London,
enabled code breakers there to continue to decipher German
air force and army communications, and in June 1941 British
mathematician Alan M. Turing and his group succeeded in
