
French National Library
An international team of cipher-breakers has succeeded in deciphering more than 50 mysterious letters discovered in French archives. The team discovers that the letters were written by him Mary Queen of Scots, to trusted allies during her imprisonment in England by Queen Elizabeth I (her cousin) – previously unknown to most historians. In a new paper published in the journal Cryptologia, the team describes how they cracked Marie’s cipher, then decrypted and translated several letters. The publication coincides with the anniversary of Mary’s execution on 8 February 1587.
“This is a really exciting discovery.” said co-author George Lasry, a computer scientist and cryptographer in Israel. Mary, Queen of Scots, left a large collection of letters preserved in various archives. However, there was earlier evidence that other letters from Mary Stuart were missing from those collections, such as those referred to in other sources but nowhere to be found. Else. The messages we have decoded are most likely part of this lost secret correspondence.” Lasry is part of the multidisciplinary DECRYPT project Dedicated to mapping, digitizing, transcribing and decoding historical ciphers.
Mary sought to protect her private letters from being intercepted and read by hostile parties. For example, I was involved in the so-called “Letter lock,” a joint training At the time to protect private messages from prying eyes. as we are I mentioned earlierJana D’Ambrogio, custodian at MIT Libraries. Coined the term “letter locking” after discovery Such letters when he was a colleague at the Secret Vatican Archives in 2000.
These “closed” Vatican letters dated back to the 15th and 16th centuries, and had strange cracks and angles that had been cut into them. D’Ambrogio realized that the letters were originally folded in an ingenious manner, essentially ‘locking’ by inserting a strip of paper into a slit, then sealing it with wax. It was not possible to open the letter without tearing that slip of paper – evidence that the letter had been tampered with.

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Queen Elizabeth I, Catherine de’ Medici, Machiavelli, Galileo Galilei, John Donne, and Marie Antoinette are among the famous people who used the letter lock for their correspondence. There are hundreds of letter-locking techniques such as “butterfly locks,” a simple method of bending and tucking into a triangle, and an ingenious method known as the “dagger trap,” which involves a booby trap disguised as another type of simpler letter lock. Mary, Queen of Scots used an intricate screw lock for her last letter (to King Henry III of France) on the eve of her execution for treason in February 1587. A 1574 letter from Mary also used a different type of screw lock.
Marie was well trained in the art of cryptography by her mother, Marie de Guise, from a young age. The large collection of her letters in various archives contains puzzling references to other missing letters. John Posey, author of Under Molehill: The Story of an Elizabethan Spy (2002), suggested that these missing letters may have been written in a cipher of Mary’s vast network of colleagues and allies—a network that was fatally compromised around mid-1583. Sir Francis Walsingham (Elizabeth I’s spy), which eventually led to Mary’s trial and execution for treason. Like many before him, Bussy assumed these letters were lost.
Enter Lasry and his fellow code-breaking enthusiasts: physicist and patent expert Satoshi Tomokiyo and pianist and music professor Norbert Biermann. As part of DECRYPT, they were searching various archives for documents encoded with zeros, especially documents that had not yet been attributable. They found several collections in the archives of the French National Library online, and identified 57 documents written entirely in cipher. Other items in the collection date from the 1620s and 1630s and were mainly concerned with “Italian affairs”. No text in the letters was written in plain language, so it was not possible to determine who wrote it without first deciphering it.