The Code Book: The Secret History of Codes and Code-breaking. Simon Singh

and long marks, dots and dashes, on a piece of paper. He also developed the now familiar Morse code for translating each letter of the alphabet into a series of dots and dashes, as given in Table 6. To complete his system he designed a sounder, so that the receiver would hear each letter as a series of audible dots and dashes.

      Back in Europe, Morse’s approach gradually overtook the Wheatstone-Cooke system in popularity, and in 1851 a European form of Morse Code, which included accented letters, was adopted throughout the Continent. As each year passed, Morse code and the telegraph had an increasing influence on the world, enabling the police to capture more criminals, helping newspapers to bring the very latest news, providing valuable information for businesses, and allowing distant companies to make instantaneous deals.

      However, guarding these often sensitive communications was a major concern. The Morse code itself is not a form of cryptography, because there is no concealment of the message. The dots and dashes are merely a convenient way to represent letters for the telegraphic medium; Morse code is effectively nothing more than an alternative alphabet. The problem of security arose primarily because anyone wanting to send a message would have to deliver it to a Morse code operator, who would then have to read it in order to transmit it. The telegraph operators had access to every message, and hence there was a risk that one company might bribe an operator in order to gain access to a rival’s communications. This problem was outlined in an article on telegraphy published in 1853 in England’s Quarterly Review:

      Means should also be taken to obviate one great objection, at present felt with respect to sending private communications by telegraph – the violation of all secrecy – for in any case half-a-dozen people must be cognisant of every word addressed by one person to another. The clerks of the English Telegraph Company are sworn to secrecy, but we often write things that it would be intolerable to see strangers read before our eyes. This is a grievous fault in the telegraph, and it must be remedied by some means or other.

      Table 6 International Morse Code symbols.

      The solution was to encipher a message before handing it to the telegraph operator. The operator would then turn the ciphertext into Morse code before transmitting it. As well as preventing the operators from seeing sensitive material, encryption also stymied the efforts of any spy who might be tapping the telegraph wire. The polyalphabetic Vigenère cipher was clearly the best way to ensure secrecy for important business communications. It was considered unbreakable, and became known as le chiffre indéchiffrable. Cryptographers had, for the time being at least, a clear lead over the cryptanalysts.

      Mr Babbage Versus the Vigenère Cipher

      The most intriguing figure in nineteenth-century cryptanalysis is Charles Babbage, the eccentric British genius best known for developing the blueprint for the modern computer. He was born in 1791, the son of Benjamin Babbage, a wealthy London banker. When Charles married without his father’s permission, he no longer had access to the Babbage fortune, but he still had enough money to be financially secure, and he pursued the life of a roving scholar, applying his mind to whatever problem tickled his fancy. His inventions include the speedometer and the cowcatcher, a device that could be fixed to the front of steam locomotives to clear cattle from railway tracks. In terms of scientific breakthroughs, he was the first to realise that the width of a tree ring depended on that year’s weather, and he deduced that it was possible to determine past climates by studying ancient trees. He was also intrigued by statistics, and as a diversion he drew up a set of mortality tables, a basic tool for today’s insurance industry.

      Babbage did not restrict himself to tackling scientific and engineering problems. The cost of sending a letter used to depend on the distance the letter had to travel, but Babbage pointed out that the cost of the labour required to calculate the price for each letter was more than the cost of the postage. Instead, he proposed the system we still use today – a single price for all letters, regardless of where in the country the addressee lives. He was also interested in politics and social issues, and towards the end of his life he began a campaign to get rid of the organ-grinders and street musicians who roamed London. He complained that the music ‘not infrequently gives rise to a dance by little ragged urchins, and sometimes half-intoxicated men, who occasionally accompany the noise with their own discordant voices. Another class who are great supporters of street music consists of ladies of elastic virtue and cosmopolitan tendencies, to whom it affords a decent excuse for displaying their fascinations at their open windows.’ Unfortunately for Babbage, the musicians fought back by gathering in large groups around his house and playing as loud as possible.

      The turning point in Babbage’s scientific career came in 1821, when he and the astronomer John Herschel were examining a set of mathematical tables, the sort used as the basis for astronomical, engineering and navigational calculations. The two men were disgusted by the number of errors in the tables, which in turn would generate flaws in important calculations. One set of tables, the Nautical Ephemeris for Finding Latitude and Longitude at Sea, contained over a thousand errors. Indeed, many shipwrecks and engineering disasters were blamed on faulty tables.

      These mathematical tables were calculated by hand, and the mistakes were simply the result of human error. This caused Babbage to exclaim, ‘I wish to God these calculations had been executed by steam!’ This marked the beginning of an extraordinary endeavour to build a machine capable of faultlessly calculating the tables to a high degree of accuracy. In 1823 Babbage designed ‘Difference Engine No. 1’, a magnificent calculator consisting of 25,000 precision parts, to be built with government funding. Although Babbage was a brilliant innovator, he was not a great implementer. After ten years of toil, he abandoned ‘Difference Engine No. 1’, cooked up an entirely new design, and set to work building ‘Difference Engine No. 2’.

      When Babbage abandoned his first machine, the government lost confidence in him and decided to cut its losses by withdrawing from the project – it had already spent £17,470, enough to build a pair of battleships. It was probably this withdrawal of support that later prompted Babbage to make the following complaint: ‘Propose to an Englishman any principle, or any instrument, however admirable, and you will observe that the whole effort of the English mind is directed to find a difficulty, a defect, or an impossibility in it. If you speak to him of a machine for peeling a potato, he will pronounce it impossible: if you peel a potato with it before his eyes, he will declare it useless, because it will not slice a pineapple.’

      Figure 12 Charles Babbage.

       Science and Society Picture Library, London.

      Lack of government funding meant that Babbage never completed Difference Engine No. 2. The scientific tragedy was that Babbage’s machine would have been a stepping stone to the Analytical Engine. Rather than merely calculating a specific set of tables, the Analytical Engine would have been able to solve a variety of mathematical problems depending on the instructions that it was given. In fact, the Analytical Engine provided the template for modern computers. The design included a ‘store’ (memory) and a ‘mill’ (processor), which would allow it to make decisions and repeat instructions, which are equivalent to the ‘IF … THEN … ’ and ‘LOOP’ commands in modern programming.

      A century later, during the course of the Second World War, the first electronic incarnations of Babbage’s machine would have a profound effect on cryptanalysis, but, in his own lifetime, Babbage made an equally important contribution to codebreaking: he succeeded in breaking the Vigenère cipher, and in so doing he made the greatest breakthrough in cryptanalysis since the Arab scholars of the ninth century broke the monoalphabetic cipher by inventing frequency analysis. Babbage’s work required no mechanical calculations or complex computations. Instead, he employed nothing more than sheer cunning.

      Babbage had become interested in ciphers at a very young age. In later life, he recalled how his childhood hobby occasionally got him into trouble: ‘The bigger boys made ciphers, but if I got hold of a few words, I usually found out the key. The consequence of this ingenuity was occasionally painful: the owners of the detected ciphers sometimes thrashed me, though the