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Cryptanalyst
Hugh Rose Foss (13 May 1902 - 23 December 1971) was a British cryptanalist
at the Government Code & Cypher School (GC&CS, later GCHQ).
He was also a Japanese linguist and an avid Scottish Dancer.
In 1927, he was one of the first people to analyse the
German commerical Enigma cipher machine (Enigma D)
and developed a method that
was used 10 years later, in 1937, to attack it.
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Foss joined GC&CS in December 1924.
He first learned about the Enigma in 1926, when there were two models on
the market: the heavy non-reciprocal Schreibende Enigma
(printing Enigma) and the portable reciprocal Glühlampenchiffriermaschine (Glow lamp
cipher machine) Enigma D.
In late 1926 or early 1927, GC&CS deputy director Commander Edward Travis
visited his friend Lt. Hume who was a Naval Attaché in Berlin [4]. As the Germans
wanted to promote their Enigma machines, Travis was able to obtain a sample,
which he brought home to the UK for evaluation.
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At some point in 1927, this machine — an Enigma D with serial
number A320 — landed on Foss' desk with the request
to analyse its cipher security. It resulted in Foss' now famous report
The Reciprocal Enigma [I],
in which he describes the machine and lists the conditions for attacking it.
At the time there was no real traffic to test the method, but that changed
in 1936, when the Spanish civil war broke out and Spanish dictator Franco
started using commercial Enigma K.
It attracted the attention of fellow codebreaker Dillwyn (Dilly) Knox.
Based on Foss' analysis, Knox developed two new codebreaking techniques knows
as Rodding and Buttoning up. Knox realised that there was a
difference between Enigma K and
Enigma D — the stepping notch was attached
to the letter ring rather than the rotor body — but this was only a minor
obstacle. In April 1937, GC&CS
codebreaker William Bodsworth was the first to use these methods to break
the Spanish Naval Enigma K. Around the same time,
Dilly Knox managed to
break the Italian Navy's Enigma K.
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1902 May 13 Born in Kobe (Japan) 1924 Graduated from Christ's College (Cambridge, UK) 1924 Dec Joined the Government Code and Cipher School (GC&CS) 1926 Learned about two Enigma models (Schreibende Enigma and Enigma C) 1927 Received Enigma D from Edward Travis for analysis 1928 Wrote paper The Reciprocal Enigma 1934 Sep Broke Japanese navala attaché cipher (with Oliver Stratchey) 1940 Worked in Hut 8 at BP 1940 Nov Broke a day's worth of Enigma code using Banburismus 1942-1944 Head of Hut 7 at BP 1944 Worked at OP-20-G in Washington (US) on Japanese CORAL cipher 1949 Wrote paper Reminiscences on Enigma [4] 1953 Retired from GCHQ 1971 Dec 23 Died in St. Johns Town of Dairy (Scotland, UK)
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Document kindly provided by Frode Weierud.
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© Crypto Museum. Created: Monday 10 October 2022. Last changed: Thursday, 25 July 2024 - 06:22 CET.
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![Hugh Foss. Photograph via GCHQ [2].](img/HughFoss.jpg)
