Read Ebook {PDF EPUB} The Time Machine by Lorenz B. Graham Pardon Our Interruption. As you were browsing something about your browser made us think you were a bot. There are a few reasons this might happen: You're a power user moving through this website with super-human speed. You've disabled cookies in your web browser. A third-party browser plugin, such as Ghostery or NoScript, is preventing JavaScript from running. Additional information is available in this support article. To regain access, please make sure that cookies and JavaScript are enabled before reloading the page. After completing the CAPTCHA below, you will immediately regain access to the site again. Pardon Our Interruption. As you were browsing something about your browser made us think you were a bot. There are a few reasons this might happen: You're a power user moving through this website with super-human speed. You've disabled cookies in your web browser. 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How Alan Turing Cracked The Enigma Code. Until the release of the Oscar-nominated film The Imitation Game in 2014, the name ‘Alan Turing’ was not very widely known. But Turing’s work during the Second World War was crucial. Who was Turing and what did he do that was so important? Mathematician. Alan Turing was a brilliant mathematician. Born in London in 1912, he studied at both Cambridge and Princeton universities. He was already working part-time for the British Government’s Code and Cypher School before the Second World War broke out. In 1939, Turing took up a full-time role at Bletchley Park in Buckinghamshire – where top secret work was carried out to decipher the military codes used by Germany and its allies. Enigma and the Bombe. The main focus of Turing’s work at Bletchley was in cracking the ‘Enigma’ code. The Enigma was a type of enciphering machine used by the German armed forces to send messages securely. Although Polish mathematicians had worked out how to read Enigma messages and had shared this information with the British, the Germans increased its security at the outbreak of war by changing the cipher system daily. This made the task of understanding the code even more difficult. Turing played a key role in this, inventing – along with fellow code-breaker Gordon Welchman – a machine known as the Bombe. This device helped to significantly reduce the work of the code-breakers. From mid-1940, German Air Force signals were being read at Bletchley and the intelligence gained from them was helping the war effort. Hut 8, Bletchley Park. Turing also worked to decrypt the more complex German naval communications that had defeated many others at Bletchley. German U-boats were inflicting heavy losses on Allied shipping and the need to understand their signals was crucial. With the help of captured Enigma material, and Turing’s work in developing a technique he called 'Banburismus', the naval Enigma messages were able to be read from 1941. He headed the ‘Hut 8’ team at Bletchley, which carried out cryptanalysis of all German naval signals. This meant that – apart from during a period in 1942 when the code became unreadable – Allied convoys could be directed away from the U-boat 'wolf-packs'. Turing’s role was pivotal in helping the Allies during the Battle of the Atlantic. Turingery and Delilah. In July 1942, Turing developed a complex code-breaking technique he named ‘Turingery’. This method fed into work by others at Bletchley in understanding the ‘Lorenz’ cipher machine. Lorenz enciphered German strategic messages of high importance: the ability of Bletchley to read these contributed greatly to the Allied war effort. Turing travelled to the United States in December 1942, to advise US military intelligence in the use of Bombe machines and to share his knowledge of Enigma. Whilst there, he also saw the latest American progress on a top secret speech enciphering system. Turing returned to Bletchley in March 1943, where he continued his work in cryptanalysis. Later in the war, he developed a speech scrambling device which he named ‘Delilah’. In 1945, Turing was awarded an OBE for his wartime work. The Universal Turing Machine. In 1936, Turing had invented a hypothetical computing device that came to be known as the ‘universal Turing machine’. After the Second World War ended, he continued his research in this area, building on his earlier work and incorporating all he'd learnt during the war. Whilst working for the National Physical Laboratory (NPL), Turing published a design for the ACE (Automatic Computing Engine), which was arguably the forerunner to the modern computer. The ACE project was not taken forward, however, and he later left the NPL. Legacy. In 1952, Alan Turing was arrested for homosexuality – which was then illegal in Britain. He was found guilty of ‘gross indecency’ (this conviction was overturned in 2013) but avoided a prison sentence by accepting chemical castration. In 1954, he was found dead from cyanide poisoning. An inquest ruled that it was suicide. The legacy of Alan Turing’s life and work did not fully come to light until long after his death. His impact on computer science has been widely acknowledged: the annual ‘Turing Award’ has been the highest accolade in that industry since 1966. But the work of Bletchley Park – and Turing’s role there in cracking the Enigma code – was kept secret until the 1970s, and the full story was not known until the 1990s. It has been estimated that the efforts of Turing and his fellow code-breakers shortened the war by several years. What is certain is that they saved countless lives and helped to determine the course and outcome of the conflict. The Lorenz Cipher. The Lorenz company designed a cipher machine based on the additive method for enciphering teleprinter messages invented in 1918 by Gilbert Vernam in America. Teleprinters are not based on the 26-letter alphabet and Morse code on which the Enigma depended. Teleprinters use the 32-symbol Baudot code. Note that the Baudot code output consists of five channels each of which is a stream of bits which can be represented as no-hole or hole, 0 or 1, dot or cross. The Baudot Code. The Vernam system enciphered the message text by adding to it, character by character, a set of obscuring characters thus producing the enciphered characters which were transmitted to the intended recipient. The simplicity of Vernam's system lay in the fact that the obscuring characters were added in a rather special way (known as modulo-2 addition). Then exactly the same obscuring characters, added also by modulo- 2 addtion to the received enciphered characters, would cancel out the obscuring characters and leave the original message characters which could then be printed. The working of modulo-2 addition is exactly the same as the XOR operation in logic. If A is the plain-text character, and C the obscuring character, then in the table below, F is the cipher-text character. You can also see from this table that the addition of C to F brings you back to A again: A + C = F F + C = A x + . = x x + . = x x + x = . . + x = x . + x = x x + x = . . + x = x x + x = . . + . = . . + . = . Vernam proposed that the obscuring characters should be completely random and pre-punched on to paper tape to be consumed character by character in synchrony with the input message characters. Such a cipher system (a 'one-time pad system') using purely random obscuring characters is unbreakable. The difficulty was how to ensure, in a hot war situation, that the same random character tapes were available at each end of a communications link and that they were both set to the same start position. The Lorenz company decided that it would be operationally easier to construct a machine to generate the obscuring character sequence. Because it was a machine it could not generate a completely random sequence of characters. It generated what is known as a pseudo-random sequence. Unfortunately for the German Army it was more "pseudo" than random and that was how it was broken. The amazing thing about Lorenz is that the code breakers in Bletchley Park never saw an actual Lorenz machine until right at the end of the war but they had been breaking the Lorenz cipher for two and a half years. The first intercepts. Brigadier John Tiltman, one of the top codebreakers in Bletchley Park, took a particular interest in these enciphered teleprinter messages. They were given the code name "Fish". The messages which (as was later found out) were enciphered using the Lorenz machine, were known as "Tunny". Tiltman knew of the Vernam system and soon identified these messages as being enciphered in the Vernam manner. Because the Vernam system depended on addition of characters, Tiltman reasoned that if the operators made a mistake and used the same Lorenz machine starts for two messages (a depth ), then by adding the two cipher texts together character by character, the obscuring character sequence would disappear. He would then be left with a sequence of characters each of which represented the addition of the two characters in the original German message texts. For two completely different messages it is virtually impossible to assign the correct characters to each message. Just small sections at the start could be derived but not complete messages. The German mistake. They now both put their Lorenz machines back to the same start position. Absolutely forbidden, but they did it. The operator at the sending end then began to key in the message again, by hand. If he had been an automaton and used exactly the same key strokes as the first time then all the interceptors would have got would have been two identical copies of the cipher text. Input the same — machines generating the same obscuring characters — same cipher text. But being only human and being thoroughly disgusted at having to key it all again, the sending operator began to make differences in the second message compared to the first. The message began with that well known German phrase SPRUCHNUMMER — "message number" in English. The first time the operator keyed in S P R U C H N U M M E R. The second time he keyed in S P R U C H N R and then the rest of the message text. Now NR means the same as NUMMER, so what difference did that make? It meant that immediately following the N the two texts were different. But the machines were generating the same obscuring sequence, therefore the cipher texts were different from that point on. The interceptors at Knockholt realised the possible importance of these two messages because the twelve letter indicators were the same. They were sent post-haste to John Tiltman at Bletchley Park. Tiltman applied the same additive technique to this pair as he had to previous Depths. But this time he was able to get much further with working out the actual message texts because when he tried SPRUCHNUMMER at the start he immediately spotted that the second message was nearly identical to the first. Thus the combined errors of having the machines back to the same start position and the text being re-keyed with just slight differences enabled Tiltman to recover completely both texts. The second one was about 500 characters shorter than the first where the German operator had been saving his fingers. This fact also allowed Tiltman to assign the correct message to its original cipher text. Now Tiltman could add together, character by character, the corresponding cipher and message texts revealing for the first time a long stretch of the obscuring character sequence being generated by this German cipher machine. He did not know how the machine did it, but he knew that this was what it was generating! The dénouement. Bill Tutte started to write out the bit patterns from each of the five channels in the teleprinter form of the string of obscuring characters at various repetition periods. Remember this was BC, "Before Computers", so he had to write out vast sequences by hand. When he wrote out the bit patterns from channel one on a repetition of 41, various patterns began to emerge which were more than random. This showed that a repetition period of 41 had some significance in the way the cipher was generated. Then over the next two months Tutte and other members of the Research section worked out the complete logical structure of the cipher machine which we now know as Lorenz: Outline of the structure of the Lorenz cipher machine. This was a fantastic tour de force and at the beginning of 1942 the Post Office Research Labs at Dollis Hill were asked to produce an implementation of the logic worked out by Bill Tutte & Co. Frank Morrell produced a rack of uniselectors and relays which emulated the logic. It was called "Tunny". So now when the manual code breakers in the Testery had laboriously worked out the settings used for a particular message, these settings could be plugged up on Tunny and the cipher text read in. A Tunny Machine. If the codebreakers had got it right, out came German. But it was taking four to six weeks to work out the settings. This meant that although they had proved that technically they could break Tunny, by the time the messages were decoded the information in them was too stale to be operationally useful. The lecture Fish and I, by Bill Tutte, gives more information on the structure of the Lorenz pseudo-random sequence and the methods developed to break Lorenz-enciphered messages. In particular it explains the 'double-delta' method which was an important element of the mechanisation programme that now ensued. This page was originally created by the late Tony Sale the original curator of the Bletchley Park Museum and is currently being hosted by Rich Sale Limited. Reworking of this section of the website is sponsored by Book Create Service who provide Self Publishing Services.