IEEE Technology and Society Magazine - September 2015 - 8

Immediately on the declaration of
war he was taken on as a temporary Civil Servant in the Foreign
Office, in the Department of Communications.... At first even his
whereabouts were kept secret,
but later it was divulged that he
was working at Bletchley Park,
Bletchley. No hint was ever given
of the nature of his secret work,
nor has it ever been revealed.

It was only decades later that the
scope and importance of Turing's
work at Bletchley Park - breaking
German codes and ciphers - first
became known. The success of
the initial English embargo on any
mention of their remarkable wartime cryptanalytic successes may be
judged by the total absence of any
mention of them in David Kahn's
encyclopedic 1967 book The Codebreakers which in contrast devoted
an entire chapter to the US exploitation of Japanese codes and ciphers.
All this changed after the publication in 1973 of General Gustav Bertrand's book Enigma. It
emerged that in 1932 the Polish
military had hired three mathemati.
cians, Marian Rejewski, Jerzy Róz
ycki, and Henryk Zygalski, to work
on the decryption of the Enigma,
a mechanical device for enciphering messages that the German military had begun using just a few
years before. For the better part
of a decade (from 1933 to 1939),
thanks in part to information provided by a German spy working in
the Cipher Bureau of the German
Ministry of Defense and passed on
by Bertrand, the Poles were able
to read a substantial majority of
the German Enigma messages, ultimately only defeated towards the
end of the decade by a succession
of German communications security upgrades. In July of 1939, in a
famous conference near Warsaw
(no doubt sensing the impending

outbreak of war), the Poles revealed
all this to their French and English
counterparts, describing their methods and providing replicas of the
device itself.
Now that Bertrand had let that
the secret was out, the English
lifted their embargo on any discussion of "Ultra," the codename
for intelligence der iving from
this source. Frederick Winterbotham's The Ultra Secret (1974)
revealed the scope and success
of the Allied wartime efforts; followed several years later by F.
H. Hinsley's multivolume British
Intelligence in the Second World
War (1979-1990). But these early
books focused almost entirely on
the use of the intelligence generated rather than the technical
methods used to acquire it, nor
did they say much about the new
role played by the "boffins" (the
technical and scientific experts).
This was a significant omission,
because signals intelligence in the
1939-1945 war was a very different affair than it had been earlier. In the years leading up to the
war, the major military powers had
turned to sophisticated machine
encryption of their messages, and
these were largely impervious to
the linguistic methods of attack
used successfully in earlier periods. Instead, mathematics and
machines came to the forefront,
and with them, the need for "men
of the Professor type."
So some of Turing's wartime
colleagues began to discuss his
vital role. One of these was I. J.
("Jack") Good, who served as Turing's primary statistical assistant
for a year. But it was only in the
1980s that the technical veil itself
was first lifted. In 1981 Rejewski wrote a paper describing the
use the Poles had made of the
mathematics of permutations to
break Enigma messages. This was

IEEE Technology and Society Magazine

followed in 1982 by Gordon Welchman's most informative book, The
Hut Six Story. Indeed, Welchman
was regarded by the British authorities as being too informative, and
lost his security clearance. Welchman had reported to Bletchley at
the outbreak of war, made key
contributions to the cryptanalysis of the Enigma, and ultimately
became the head of Hut 6 (Army
and Luftwaffe cryptanalysis). Turing, as Welchman revealed, had
played a key part in developing
the attack on the Enigma, helping,
among other things, to develop
the "Bombe," a mechanical device
used to determine the daily settings of the machine.
So by 1982 a modest amount
was known. Turing and Bletchley, it turned out, were the perfect
combination. Turing liked to attack
from scratch hard problems that
had stymied others. It was precisely this mindset that emboldened
him to attack the Entscheidungsproblem. The time was therefore
ripe for a full account of his life:
Andrew Hodges's 1983 biography,
Alan Turing: The Enigma. Hodges's book described in extensive
and sympathetic detail the whole
of Turing's life, from his boyhood
in the 1920s to his tragic suicide in
1954. It became an instant classic.
One detail, from many that could
be cited, illustrates the meticulous care that Hodges took. In the
autumn of 1928 Turing had been
a student at Sherborne, an English
public school. His mathematics
master at the time, D. B. Eperson,
later wrote:
All that I can claim is that my
deliberate policy of leaving him
largely to his own devices and
standing by to assist when necessary, allowed his natural mathematical genius to progress uninhibited. [Hodges, p. 43]
∕

september 2015

Table of Contents for the Digital Edition of IEEE Technology and Society Magazine - September 2015