Читать книгу Engineering Hitler's Downfall - Gwilym Roberts - Страница 33

Originally invented by a German engineer around 1920, early Enigma encoding machines were used commercially but were later adopted by the German military who also upgraded them. The Poles were also working on them; by December 1932 they had broken the German cyphers. They also built replica machines and, five weeks before the outbreak of the Second World War, they gave replica equipment to the British GC&CS and their French equivalent together with details of their decryption techniques.

Courtesy of Greg Goebel

The Enigma machines worked on electro-mechanical principles and had five rotors, each with a variety of settings which were generally changed on a daily basis, meaning time was always of the essence – it was calculated that there could have been 159x1018 possible daily keys.

Separate coding systems were used by each of the German services, adding to the difficulties of their decryption. As the numbers working at Bletchley Park increased, wooden huts were built in the grounds, with each hut’s occupants dealing with separate aspects of the decrypting operation. Hut 6 under Gordon Welchman was responsible for dealing with Army and Air Force codes, while Navy codes were the responsibility of Hut 8, which was initially controlled by Alan Turing and subsequently by Hugh Alexander.

In the early days the successful cracking of a code relied to a certain extent on insights and inspired guesses by the cryptologists as to the likely behaviour of the German operatives of the machines. Some frequently used insights were named after the person who first proposed them e.g. the Herivel tip, or Herivelismus, after John Herivel and Parkerismus after Reg Parker.

Outstanding work by the GC&CS cryptanalysts enabled some messages to be broken as early as 1940. Further clues as to the workings of the Enigma machines and of the naval codes used were obtained by the capture of German weather boats off Iceland in 1940–41; however, as code settings were changed each month they could be broken only for a limited period. Then, in May 1941, U-boat U-110 attacked a convoy though depth charges fired by the escorting vessels forced her to surface, whereupon her crew abandoned ship. Instead of ramming and sinking her, the captain of HMS Bulldog ordered one of his officers, Sub-Lieutenant David Balme RN, to be rowed over, board the submarine, and retrieve anything of interest. Among the prize items of equipment he took back to Bulldog were an Enigma machine and current code books, which were then rushed to Bletchley Park in great secrecy. (Balme was awarded the DSC.) Next, in October 1942, U-559 was sunk in the eastern Mediterranean. Before she went under, three crew members of the attacking ship, HMS Petard, were able to board her and recover the code books. Sadly, the submarine sank suddenly, taking two of the boarding party with her.