Simon Singh

The Cracking Code Book


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href="#litres_trial_promo">Figure 8 shows the postscript that was added at the end of Mary’s letter to Babington. It can be deciphered using Mary’s nomenclator, as shown in Figure 7, to reveal the following plaintext:

      I would be glad to know the names and qualities of the six gentlemen which are to accomplish the designment; for it may be that I shall be able, upon knowledge of the parties, to give you some further advice necessary to be followed therein, as also from time to time particularly how you proceed: and as soon as you may, for the same purpose, who be already, and how far everyone is privy hereunto.

      

      Figure 8 The forged postscript added by Thomas Phelippes to Mary’s message. It can be deciphered by referring to Mary's nomenclator (Figure 7).

      Soon after receiving the message and its postscript, Babington needed to go abroad to organize the invasion, and had to register at Walsingham’s department in order to acquire a passport. This would have been an ideal time to capture the traitor, but the bureaucrat who was manning the office, John Scudamore, was not expecting the most wanted traitor in England to turn up at his door. Scudamore, with no support to hand, took the unsuspecting Babington to a nearby tavern, stalling for time while his assistant organized a group of soldiers. A short while later a note arrived at the tavern, informing Scudamore that it was time for the arrest. Babington, however, caught sight of it. He casually said that he would pay for the beer and meal and rose to his feet, leaving his sword and coat at the table, implying that he would return in an instant. Instead, he slipped out of the back door and escaped, first to St John’s Wood and then on to Harrow. He attempted to disguise himself, cutting his hair short and staining his skin with walnut juice to mask his aristocratic background. He managed to elude capture for ten days, but by August 15, Babington and his six colleagues were captured and brought to London. Church bells across the city rang out in triumph. Their executions were horrid in the extreme. In the words of the Elizabethan historian William Camden, “they were all cut down, their privities were cut off, bowelled alive and seeing, and quartered!”

      Meanwhile, on August 11, Mary Queen of Scots and her entourage had been allowed the exceptional privilege of riding in the grounds of Chartley Hall. As Mary crossed the moors she spied some horsemen approaching, and immediately thought that these must be Babington’s men coming to rescue her. It soon became clear that these men had come to arrest her, not release her. Mary had been implicated in the Babington Plot and was charged under the Act of Association, an Act of Parliament passed in 1584 specifically designed to convict anybody involved in a conspiracy against Elizabeth.

      The trial was held in Fotheringhay Castle, a bleak, miserable place in the middle of the featureless fens of East Anglia. It began on Wednesday, October 15, in front of two chief justices, four other judges, the Lord Chancellor, the Lord Treasurer, Walsingham, and various earls, knights and barons. At the back of the courtroom there was space for spectators, such as local villagers and the servants of the commissioners, all eager to see the humiliated Scottish queen beg forgiveness and plead for her life. However, Mary remained dignified and composed throughout the trial. Mary’s main defence was to deny any connection with Babington. “Can I be responsible for the criminal projects of a few desperate men,” she proclaimed, “which they planned without my knowledge or participation?” Her statement had little impact in the face of the deciphered letters.

      The trial went into a second day, and Mary continued to deny any knowledge of the Babington Plot. When the trial finished, she left the judges to decide her fate, pardoning them in advance for the inevitable decision. Ten days later, the Star Chamber met in Westminster and concluded that Mary had been guilty of “compassing and imagining since June 1st matters tending to the death and destruction of the Queen of England.” They recommended the death penalty, and Elizabeth signed the death warrant.

      On February 8, 1587, in the Great Hall of Fotheringhay Castle, an audience of three hundred gathered to watch the beheading. Walsingham was determined to minimize Mary’s influence as a martyr, and he ordered that the block, Mary’s clothing and everything else relating to the execution be burned afterwards in order to avoid the creation of any holy relics. He also planned a lavish funeral procession for his son-in-law, Sir Philip Sidney, to take place the following week. Sidney, a popular and heroic figure, had died fighting Catholics in the Netherlands, and Walsingham believed that a magnificent parade in his honour would dampen sympathy for Mary. However, Mary was equally determined that her final appearance should be a defiant gesture, an opportunity to reaffirm her Catholic faith and inspire her followers.

      While the Dean of Peterborough led the prayers, Mary spoke aloud her own prayers for the salvation of the English Catholic Church, for her son and for Elizabeth. With her family motto, “In my end is my beginning”, in her mind, she composed herself and approached the block. The executioners requested her forgiveness, and she replied, “I forgive you with all my heart, for now I hope you shall make an end of all my troubles.” Richard Wingfield, in his Narration of the Last Days of the Queen of Scots, describes her final moments:

      Then she laide herself upon the blocke most quietile, & stretching out her armes & legges cryed out In manus tuas domine three or foure times, & at the laste while one of the executioners held her slightlie with one of his handes, the other gave two strokes with an axe before he cutt of her head, & yet lefte a little gristle behinde at which time she made verie small noyse &, stirred not any parte of herself from the place where she laye…. Her lipps stirred up & downe almost a quarter of an hower after her head was cutt of. Then one of her executioners plucking of her garters espied her little dogge which was crept under her clothes which could not be gotten forth but with force & afterwardes could not depart from her dead corpse, but came and laye betweene her head & shoulders a thing dilligently noted.

      Figure 9 The execution of Mary Queen of Scots.

       2 The Anonymous Codebreaker

       The Vigenère cipher, why cryptographers seldom get credit for their breakthroughs and a tale of buried treasure

      For centuries, the simple monoalphabetic substitution cipher had been sufficient to ensure secrecy. The subsequent development of frequency analysis, first in the Arab world and then in Europe, destroyed its security. The execution of Mary Queen of Scots was a dramatic illustration of the weaknesses of monoalphabetic substitution, and in the battle between cryptographers and cryptanalysts it was clear that the cryptanalysts had gained the upper hand. Anybody sending an encrypted message had to accept that an expert enemy codebreaker might intercept and decipher their most precious secrets.

      The burden was clearly on the cryptographers to concoct a new, stronger cipher, something that could outwit the cryptanalysts. Although such a cipher would not emerge until the end of the sixteenth century, its origins can be traced back to the fifteenth-century Florentine polymath Leon Battista Alberti. Born in 1404, Alberti was one of the leading figures of the Renaissance – a painter, composer, poet and philosopher, as well as the author of the first scientific analysis of perspective, a treatise on the housefly and a funeral oration for his dog. He is probably best known as an architect, having designed Rome’s first Trevi Fountain and having written De re aedificatoria, the first printed book on architecture, which acted as a catalyst for the transition from Gothic to Renaissance design.

      Sometime in the 1460s, Alberti was wandering through the gardens of the Vatican when he bumped into his friend Leonardo Dato, the pontifical secretary, who began chatting to him about some of the finer points of cryptography. This casual conversation prompted Alberti to write an essay on the subject, outlining what he believed