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Dilly Knox
Cocebreaker - this page is a stub

Alfred Dillwyn (Dilly) Knox (23 July 1884 - 27 February 1943) was a British classics scholar, papyrologist and codebreaker. During WWI he worked at the Navy's Room 40 codebreaking unit, where he helped decrypt the Zimmermann Telegram, which brought the US into World War I [1]. During World War II (WWII) he ran his own codebreaking operation — Intelligence Service Knox (ISK) — at Bletchley Park, where he was successful in breaking the Enigma cipher of the Abwehr.

Following the start of WWI in 1914, Knox was recruited to the Royal Navy's codebreaking effort in Room 40 of the Admiralty Old Building in London. He was involved in breaking the Zimmermann Telegram which brought the US into the war. He then joined the Government Code and Cypher School (GC&CS) — a cover name for the joint signals intelligence sections of the British Army (MI1b) and the British Navy (NID25, formerly: Room 40).

In 1925, Knox bought a commercial Enigma C in Vienna. The machine was evaluted in 1927 on behalf of GC&CS by Hugh Foss, who developed a cryptographic attack based on pieces of guessed plaintext (cribs). In 1937, Knox picked up Foss' work and improved his attack by developing a more effective algebraic method, which eventually became known as rodding. He subsequently used it to successfully break the Enigma K cipher used by the Franco Nationalists in the Spanish Civil War [1].

Soon after breaking the Spanish Enigma K, Knox began to attack the signals between Germany and Spain which were encrypted with steckered Enigma machines. in 1938, GC&CS began discussing these Enigma machines (known as Enigma I) with the French Deuxième Bureau.

The French disclosed their links with Polish cryptographers and shared details about the Wehrmacht Enigma — obtained from a spy codenamed Asché — and intercepts made by the Poles. This led to the first Polish-French-British meeting in Paris (France) in January 1939. In a second meeting on 25-26 July 1939 at Pyry (near Warsaw, Poland), the Poles disclosed their achievements in breaking the steckered Wehrmacht Enigma to the French and the British.

The work on steckered Enigma was later taken over by Alan Turing, who developed the Bombe — an improvment of the Polish Bomba — for its solution. In the meantime, Knox and his team of 'girls' worked on non-steckered Enigma ciphers, which included the machines used by the Italian Navy and the German Abwehr. In October 1941, Knox first solved the Abwehr Enigma, after which Intelligence Service Knox (ISK) was established to decrypt further Abwehr traffic.

In the meantime, Knox had been diagnosed with lymphoma. When he became too ill to travel to Blechley Park in early 1942, he continued his cryptographic work from his home in Hughenden (Buckinghamshire, UK), whilst Peter Twinn took over as head of ISK. By the end of the war, ISK had decrypted and disseminated 140,800 messages. Dilly Knox didn't live to see the success of his work. He died on 27 February 1943 at the age of 58. One of his girls — Mavis Batey — wrote a biography about him — Dilly: the man who broke Enigmas — which was published in 2009 [2].

Related subjects
Zählwerk Enigma (Enigma G and Abwehr Enigma)
Enigma K, the commercial Enigma
Keith Batey (4 July 1919 - 28 August 2010)
  1. Wikipedia, Dilly Knox
    Retrieved September 2022.

  2. Mavis Batey, Dilly, The Man Who Broke Enigmas
    2009. Hard cover, ISBN 978-1-906447-01-4.

  3. Wikipedia, GCHQ — Government Code and Cypher School
    Retrieved September 2022.
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