The Man Who Broke Purple by Ronald Clark

Author:Ronald Clark
Language: eng
Format: epub
Publisher: Bloomsbury Publishing
Published: 1977-01-15T00:00:00+00:00

II How PURPLE came to Britain

The Friedman team’s success with Purple in August 1940 had come at an interesting moment in military cryptography quite apart from the arrival in Washington of Hagelin and his equipment.

In Britain, which had been at war with Germany since the previous September, and with Italy since May, some formidable feats of cryptanalysis had already been accomplished. Between the two world wars the government’s cryptographic organization, set up in Broadway, Westminster in 1923 under Alastair Denniston and combining the functions of Yardley’s Black Chamber, Friedman’s Signals Intelligence Service, and the US naval counterpart, had achieved a mixed record of failure and success. In 1927, when the government’s inept move against the Russian trading organization had revealed that at least some Russian codes had been broken, these were scrapped by the Russians and replaced by use of the one-time pad, a system which although it had operational disadvantages was virtually unbreakable. Eight years later the Abyssinian War gave Denniston the opportunity for which he had been waiting and a number of Italian codes were broken following efficient interception of Italian naval traffic off East Africa. But there was a price to be paid: the Germans, radio-watching British naval vessels in the Red Sea just as the British were watching the Italians, accumulated enough intercepts to break some of the Admiralty’s codes. The Germans exploited their success and by the outbreak of World War II their efficient Beobachtung-Dienst in Berlin had fifty cryptanalysts reading British naval codes alone, an operation that continued successfully until 1942-3.

Two years after Abyssinia, the Spanish Civil War, in which the Italians used their own adaptation of Enigma to service their interventionist forces, gave the British a chance to study their machine encipherments. This time Denniston’s team had little success. However, by August 1939, when they had been evacuated to Bletchley, a small town some forty miles north of London, the British had obtained at least one, and possibly two, replicas of the German Enigma machine, altered and improved for use by the German Services.

It is typical of the contradictions surrounding the cryptographic establishment that there are two different versions of how it, or they, were secured. According to General Bertrand of the French cryptographic services — who has described the events in his book Enigma- the French were in the 1930s able to supply their Polish allies with certain Enigma material bought from a civilian cipher clerk in the German Army. The Poles, who had already made some progress in breaking the Enigma systems, were then able to complete their work, and to reconstruct the new Enigma mechanism — a feat somewhat comparable to that of Friedman’s team on Purple but one of course made infinitely easier by the use of the German Army material. On 9 January 1939, French, Polish and British cryptologists met in Paris and discussed the problems that still remained, since having a replica of the machine was only a part of the solution. The Poles now took over

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