The Code Book by Simon Singh Page A

line, a system spanning the 60 km between Baltimore and Washington. Morse used an electromagnet to enhance the signal, so that upon arriving at the receiver’s end it was strong enough to make a series of short 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 cognizant 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.

    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.
    Table 6 International Morse Code symbols.

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 realize 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