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Mary’s Cipher of Death Jimmy Pautz

MAT 390 – Cryptography Dr. Meyer April 12, 2010

Pautz 2

Most people do not know what cryptography is or why I would be taking a class focusing on it. In fact, most people do not realize how common cryptography is in their daily lives or how many lives have been saved and lost because of cryptography’s ability or inability to keep information secret. The beautiful Mary Queen of Scots too was affected quite seriously by a particular cipher that bears her name. 1 Though, for Mary, cryptography led to her death. The cipher that Mary Queen of Scots and the Babington conspirators used should have been stronger because of how advanced cryptography was at the time and the sensitive nature of the information being discussed. To understand why Mary needed a cipher to communicate, one needs to understand her situation. Mary was born shortly after Henry VIII defeated her father James V and the Scottish army. Her father died days after she was born at the age of thirty, leaving only Mary as heir to the Scottish throne (and, as some would argue, the English throne).2 Because it would have been considered unchivalrous, Henry VIII did not invade Scotland now under rule of an infant queen. Instead, he started trying to arrange the marriage between his son Edward and the Scottish Queen Mary. After consideration by the Scottish court, they denied Henry for the French dauphin Francis. Scotland would continue James V’s venture by uniting Scotland and .3 Both Mary and Francis were children, but the marriage was arranged, which also provided protection for Scotland from any more English invasions.4 By the age of six, the English started attacking the Scotch again, and for her protection Mary was sent to grow up in the French courts. She grew to love her suitor Francis and they married at the age of sixteen. The next year they were crowned King

Pautz 3 and Queen of . Only months after they were crowned, Francis—who always had health problems—died of an ear infection that he had had since he was a child.5 The next year she returned to a changed Scotland. The Catholic Mary tolerated the majority’s turn toward Protestantism and generally ruled with favor. When she married her cousin Henry Stewart, the Earl of Darnley, things started going downhill. He was a brutal, power-hungry man who lost her the favor of the Scottish nobles. He was essentially a horrible person. Mary realized who she had really married when she witnessed him murder her secretary. It was clear that Darnley needed to go. On February 9, 1567, Darnley’s house was blown up and he was strangled when he attempted to escape.6 7

Mary was married again, this time to James Hepburn, the Fourth Earl of Bothwell.

This was not a good decision and by the summer of 1567, the Scottish nobles imprisoned Mary and exiled her new husband. They crowned Mary’s infant son from her second

marriage, James VI, as king. The

Figure 17

next year Mary escaped from her prison,

Pautz 4 gathered an army, and attempted to regain her throne. Although she had greater numbers, her army was easily defeated. Mary fled south, hoping to seek refuge with her cousin, Elizabeth I, but she was immediately arrested for the murder of Darnley.8 Murder was the official charge, but historians believe it was because of the threat she posed to Elizabeth’s throne.9 The Catholics in England claimed that Mary had the true right to the throne, citing that Henry VIII’s divorce was unlawful, and therefore the marriage to Anne Boleyn was not valid and Elizabeth was a bastard. (Bastards were not allowed to rule in England.) Mary was a direct descendant of Margaret Tudor, Henry VIII’s elder sister and therefore had a claim to the English throne (see figure 1).10 Though Mary was imprisoned, her conditions were not bad. She was held in different castles and manors throughout England. Mary was respected by most because “[s]he hath withal an alluring grace, a pretty Scotch accent, and a searching wit, clouded with mildness.”11 After many years, her health worsened because of her conditions and the acquisition of a Puritan jailer, who was “immune to her charms.”12 After attempts to her son James VI, Mary was at an all-time low: her son hated her, she was imprisoned with no amenities, and her health was failing her. At this low point, she received a packet of letters of iration from the French delivered by Gilbert Gifford, a professional spy for Sir Francis Walsingham and the English government. Gifford somehow received a recommendation from Mary’s ambassador to and put himself in position to smuggle messages to and from the imprisoned Mary.13 Gifford had devised a method of steganography by smuggling the messages through empty beer barrels.

Pautz 5 One of the irers of Mary was the well known Anthony Babington. Babington was a former page of Mary’s who began organizing a plot to “assassinate Elizabeth, incite a general Catholic uprising in England, and crown Mary.”14 Although Babington and his coconspirators were happy with their plot, they would not proceed without Mary’s blessing.15 At about the same time, Mary had heard about the plot through her French ers and sent a letter to Babington (through Gifford) asking for his reply. In turn, Babington sent a letter outlining the plot, enciphering the letter with a nomenclator.16 According to Simon Singh, “[a] nomenclator is a system of encryption that relies on a cipher alphabet, which is used to encrypt the majority of the message, and a limited list of codewords.”17 Mary’s featured monoalphabetic substitution of 23 symbols for letters (j, v, and w were excluded) and 36 symbols representing words or phrases. It also featured four nulls and one dowbleth. The dowbleth indicated that the next symbol would be a double letter (see figure 2).18

Figure 219

Even though the messages between Mary

and Babington

were

encrypted, Gifford

still

brought the

Pautz 6 letters to Walsingham. Walsingham, years before, recognized the value of cryptography and being able to break it. He hired Thomas Phelippes as his cipher secretary and started a cipher school in London.20 When Walsingham received the letters from Gifford, he would send them to Phelippes, who would get to work immediately on them. Once he decrypted them, he would send both the decrypted and the originals to Walsingham, who would send the originals onward to their intended goal.21 Walsingham waited until he gathered enough information to arrest the conspirators. Finally Babington sent a letter to Mary detailing the plot further and she “not having explicitly commanded, in her reply, that that part [the assassination of Elizabeth] should be abandoned, she was clearly chargeable under the Bond of Association.”22 Although he had proof enough to arrest Mary, Walsingham still wanted the names of the other six coconspirators, so he had Phelippes forge a postscript to Mary’s letter to Babington asking for “the names and qualities of the six gentlemen which are to accomplish the designment.”23 Soon after Babington receive the forged note, he needed to go abroad. He needed to to get a port, which happened to be in Walsingham’s department. The man who was running the office was ill-prepared for a wanted man to show up, so he stalled Babington by taking him to a tavern until soldiers could come and arrest him. Babington saw the notice of arrest and slipped out the back door while pretending to pay for the drinks.24 He and the other six men managed to avoid capture for ten days, but they were eventually arrested and were executed. Elizabethan historian William Camden said, “They were all cut down; their privities were cut off, bowelled alive and seeing, and quartered.”25

Pautz 7 Though the conspirators were executed almost immediately after their arrest, Mary was allowed a fair trial. She denied association with the men and claimed that she had nothing to do with them. However, the evidence greatly outweighed her testimony and the judges recommended the death penalty. Mary’s cousin Elizabeth I signed the death warrant. Three hundred people gathered to watch Mary’s beheading on February 8, 1587.26 One might ask how Mary was sentenced to death, if the messages were encrypted. Evidence shows that the cipher had major flaws. The cipher mostly consisted of simple substitution methods, which can be decrypted by use of frequency analysis. This was, in fact, the method that Phelippes used to break the cipher.27 Furthermore, because of the nature of the cipher, after he broke the cipher once, he had the key and could break it even more quickly any subsequent times. Phelippes used the context of the rest of the message to guess the code words/phrases in the rest of the nomenclator. Another reason the cipher failed was because of the confidence that Mary and Babington had in it. This confidence may have increased due to the steganography involved, but they should have still realized how easy their cipher could be broken had it fallen into the wrong hands. This confidence is probably the reason they were susceptible to the forgery. Had Mary and Babington realized how advanced cryptography was at time, they would have used a stronger cipher and probably would have saved their lives. To understand why Mary’s cipher was too simple for the times, one needs to understand how cryptography advanced up to the times of Mary Queen of Scots and her cipher. Cryptography first was used by Islamic Arab nations in the ninth and tenth centuries.

Pautz 8 Many years before the Europeans, the Arabs were already employing the use of cryptography and cryptanalysis.28 By the fourteenth century, the Arab cryptographer Qalqashandi had already developed ciphers that featured transposition and more than one substitute for a single plaintext letter.29 The Islamic Arabs were so advanced at cryptography because their nations flourished, along with their mathematics and linguistic education at that time. While the Arabs “enjoyed a vigorous period of intellectual achievement, […] Europe was firmly stuck in the Dark Ages.”30 These factors are why there was such disparity between the Arab and European advancement in cryptography. In the fifteenth century, cryptography was an industry in Europe as it was widely used in diplomatic affairs. This was due to the revival of the “arts, sciences, and scholarship” that occurred during the Renaissance Age.31 “Renaissance nurtured the capacity for cryptography, while an explosion in political machination offered ample motivation for secret communication.” Giovanni Soro, the Venetian cipher secretary in the early 1500s, was the “first great European cryptanalyst.”32 He put Italy on top of the cryptography food chain. Soro was sent messages to decrypt from all over Europe, even the Vatican—which had the second best cryptographers in Europe. Because he was so skilled, cryptographers had to work hard to invent new cryptosystems or adjust existing ones and make them more difficult to break. Monoalphabetic substitution ciphers were eventually broken by cryptanalysts’ use of frequency analysis. Cryptographers, in an effort to strengthen their ciphers, introduced codes and nomenclators. Nomenclators were solved again by frequency analysis and by logical use of context (for the codewords). Codes proved too difficult for those trying to send and

Pautz 9 receive them because of the need for a large codebook. Another advancement in cryptography was the introduction of nulls. Nulls are letters/symbols that do not substitute for anything in an attempt to confuse cryptanalysts. A different effort of advancement was the act of misspelling words on purpose so that frequency analyzers would have a more difficult time at finding patterns in frequency. Nulls and misspellings were eventually broken or dealt with. All of these advancements happened more than 50 years before the Babington conspirators and Mary started their correspondence and therefore should have been taken into by Mary or Babington.33 Both parties knew the value of the information that they sent to each other and the consequences if that information would happen to fall into the wrong hands. The message encrypted with the cipher of Mary, Queen of Scots did fall into the wrong hands and the worst that could have happened did happen. Had Mary or Babington taken into the cipher’s weakness—its ability to be broken by frequency analysis—they may have succeeded in their plot. Overconfidence in their cryptosystem and the steganographic aspect may have disillusioned Mary and Babington into thinking that their cipher was strong. Failure to study cryptography, its advances, and methods of cryptanalysis cost them their lives. Most people do not know what cryptography is and are ignorant to the fact that they could be dead right now without it. At least Mary and Babington knew what it was; it is a pity they did not know more.

Pautz 10 Notes

1

George Malcolm Thomson, The Crime of Mary Stuart (New York: E. P. Dutton & Co., Inc., 1967), 15. Simon Singh, The Code Book: The Evolution of Secrecy from Mary, Queen of Scots to Quantum Cryptography (New York: Doubleday, 1999), 32. 3 Ibid., 33. 4 Ibid., 33. 5 Ibid., 33. 6 Ibid., 34. 7 Thomson, The Crime, 10. 8 Ian B. Cowan, The Enigma of Mary Stuart (New York: St. Martin’s Press, 1971), 160-161. 9 Singh, The Code Book, 35. 10 Thomson, The Crime of Mary Stuart, 10. 11 qtd. in Singh, The Code Book, 35. 12 Ibid., 35. 13 Andrew Dakers, The Tragic Queen: A Study of Mary Queen of Scots (Cambridge, MA: The Riverside Press, 1931), 218. 14 David Kahn, The Codebreakers: The Story of Secret Writing (New York: Scribner, 1996), 122. 15 Singh, The Code Book, 37. 16 Ibid., 37. 17 Ibid., 31. 18 Ibid., 38. 19 Ibid., 38. 20 Dakers, The Tragic Queen, 221. 21 Kahn, Codebreakers, 122. 22 Dakers, The Tragic Queen, 223. 23 qtd. in Kahn, Codebreakers, 123. 24 Singh, The Code Book, 42. 25 qtd. in Ibid., 42 26 Ibid., 44. 27 Ibid., 40. 28 Kahn, Codebreakers, 97. 29 Ibid., 96. 30 Singh, The Code Book, 26. 31 Ibid, 27. 32 Ibid, 28. 33 Ibid., 31. 2