The Bletchley Park Codebreakers by Michael Smith Read Free Book Online Page B

1920, particularly in India 1921–1929. Much of this was new to them – I don’t remember that they told me anything significant that I didn’t know already.
    The Mask operation led by Tiltman continued until the middle of 1937. Its significance is confirmed not just by Curry but by Josh Cooper who remarked that while the work carried out by Kenworthy’s police unit was of no particular interest to the police it was ‘of great importance to the future GCHQ’.
    Exploitation of Soviet armed forces traffic during the interwar period appears to have been less systematic and therefore less successful than that of the diplomatic and Comintern networks. It is not clear how much military material was deciphered in India. But both Simla and Sarafand had limited success with Russian military ciphers. There was also some early work on the ciphers of the KGB. But during the 1920s and early 1930s, the main focus inside GC&CS with regard to Soviet armed forces was on the Russian Navy.
    William ‘Nobby’ Clarke, a former member of Room 40, was one of a number of GC&CS members unhappy at the way in which the codebreakers and the intercept operators were increasingly being asked to work on diplomatic material at the expense of service traffic. He managed to persuade the Admiralty that there should be a naval section within GC&CS and then made the rounds of Royal Navy establishments and ships, coaxing a number of officers into agreeing to intercept Russian, French and Japanese wireless communications in their spare time while at sea. The Royal Navy intercept station at Flowerdown also began taking Russian naval material and the Army station in Sarafand covered the Black Sea Fleet. But the use of one-time pads and a lack of depth ensured that few messages were deciphered.
    Clarke’s report on Naval Section work for 1927 admitted that there had been very little naval traffic intercepted, all of it between shore-based establishments. There had, however, been some success in solving a super-enciphered system in which encoded messages were reciphered before transmission, a practice designed to make them more difficult for an eavesdropper to read. The messages were first encoded using a codebook, which provided groups of randomly selected figures for common words or phrases. This produced a series of groups of figures, normally uniformly four-figure or five-figure groups. The operator then took a stream of predetermined but randomly selected figures, placed them underneath his encoded message, and added the two together figure by figure, using non-carrying arithmetic, to produce the reciphered message.
    In an attempt to find out whether it was worthwhile continuing towork on the Russian Navy ciphers, Clarke decided to see the problems faced by his volunteer intercept operators for himself: ‘In the hope of clearing up the problem of Russian naval ciphers, I joined HMS
Curacao
for the Baltic cruise of the 2nd Light Cruiser Squadron … Unfortunately the amount of intercepts available does not permit of much work being undertaken on this kind of traffic nor is it considered that it would be profitable.’ The situation improved slightly in 1929. Although no messages had been broken, enough intercepts were coming in to allow some limited traffic analysis.
    During late 1929 and 1930, the Naval Section launched a concerted effort to try to solve the Russian naval codes and ciphers. Josh Cooper was sent to Sarafand to carry out a fifteen-month investigation of Black Sea Fleet communications while Lieutenant-Commander G. A. ‘Titts’ Titterton, a former member of the Naval Section, returned from a Russian interpreter’s course to work on Russian Navy material in London.
    Cooper’s report shows that there were a number of different codes and ciphers in use, ranging from relatively simple systems to high-grade ciphers. But while the lower grade systems proved vulnerable he was not able to break any of the high-grade systems and Titterton seems