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

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      Figure 8 The nomenclator of Mary Queen of Scots, consisting of a cipher alphabet and codewords.

      Gifford was still a youth, even younger than Babington, and yet he conducted his deliveries with confidence and guile. His aliases, such as Mr Colerdin, Pietro and Cornelys, enabled him to travel the country without suspicion, and his contacts within the Catholic community provided him with a series of safe houses between London and Chartley Hall. However, each time Gifford travelled to or from Chartley Hall, he would make a detour. Although Gifford was apparently acting as an agent for Mary, he was actually a double agent. Back in 1585, before his return to England, Gifford had written to Sir Francis Walsingham, Principal Secretary to Queen Elizabeth, offering his services. Gifford realised that his Catholic background would act as a perfect mask for infiltrating plots against Queen Elizabeth. In the letter to Walsingham, he wrote, ‘I have heard of the work you do and I want to serve you. I have no scruples and no fear of danger. Whatever you order me to do I will accomplish.’

      Walsingham was Elizabeth’s most ruthless minister. He was a machiavellian figure, a spymaster who was responsible for the security of the monarch. He had inherited a small network of spies, which he rapidly expanded into the Continent, where many of the plots against Elizabeth were being hatched. After his death it was discovered that he had been receiving regular reports from twelve locations in France, nine in Germany, four in Italy, four in Spain and three in the Low Countries, as well as having informants in Constantinople, Algiers and Tripoli.

      Walsingham recruited Gifford as a spy, and in fact it was Walsingham who ordered Gifford to approach the French Embassy and offer himself as a courier. Each time Gifford collected a message to or from Mary, he would first take it to Walsingham. The vigilant spymaster would then pass it to his counterfeiters, who would break the seal on each letter, make a copy, and then reseal the original letter with an identical stamp before handing it back to Gifford. The apparently untouched letter could then be delivered to Mary or her correspondents, who remained oblivious to what was going on.

      When Gifford handed Walsingham a letter from Babington to Mary, the first objective was to decipher it. Walsingham had originally encountered codes and ciphers while reading a book written by the Italian mathematician and cryptographer Girolamo Cardano (who, incidentally, proposed a form of writing for the blind based on touch, a precursor of Braille). Cardano’s book aroused Walsingham’s interest, but it was a decipherment by the Flemish cryptanalyst Philip van Marnix that really convinced him of the power of having a codebreaker at his disposal. In 1577, Philip of Spain was using ciphers to correspond with his half-brother and fellow Catholic, Don John of Austria, who was in control of much of the Netherlands. Philip’s letter described a plan to invade England, but it was intercepted by William of Orange, who passed it to Marnix, his cipher secretary. Marnix deciphered the plan, and William passed the information to Daniel Rogers, an English agent working on the Continent, who in turn warned Walsingham of the invasion. The English reinforced their defences, which was enough to deter the invasion attempt.

      Now fully aware of the value of cryptanalysis, Walsingham established a cipher school in London and employed Thomas Phelippes as his cipher secretary, a man ‘of low stature, slender every way, dark yellow haired on the head, and clear yellow bearded, eaten in the face with smallpox, of short sight, thirty years of age by appearance’. Phelippes was a linguist who could speak French, Italian, Spanish, Latin and German, and, more importantly, he was one of Europe’s finest cryptanalysts.

      Upon receiving any message to or from Mary, Phelippes devoured it. He was a master of frequency analysis, and it would be merely a matter of time before he found a solution. He established the frequency of each character, and tentatively proposed values for those that appeared most often. When a particular approach hinted at absurdity, he would backtrack and try alternative substitutions. Gradually he would identify the nulls, the cryptographic red herrings, and put them to one side. Eventually all that remained were the handful of codewords, whose meaning could be guessed from the context.

      When Phelippes deciphered Babington’s message to Mary, which clearly proposed the assassination of Elizabeth, he immediately forwarded the damning text to his master. At this point Walsingham could have pounced on Babington, but he wanted more than the execution of a handful of rebels. He bided his time in the hope that Mary would reply and authorise the plot, thereby incriminating herself. Walsingham had long wished for the death of Mary Queen of Scots, but he was aware of Elizabeth’s reluctance to execute her cousin. However, if he could prove that Mary was endorsing an attempt on the life of Elizabeth, then surely his queen would permit the execution of her Catholic rival. Walsingham’s hopes were soon fulfilled.

      On 17 July, Mary replied to Babington, effectively signing her own death warrant. She explicitly wrote about the ‘design’, showing particular concern that she should be released simultaneously with, or before, Elizabeth’s assassination, otherwise news might reach her jailer, who might then murder her. Before reaching Babington, the letter made the usual detour to Phelippes. Having cryptanalysed the earlier message, he deciphered this one with ease, read its contents, СКАЧАТЬ