Recently I was listening to an episode of Strong Sense of Place (actually their spin-off series, The Library of Lost Time) when I heard about a stack of 16th century coded letters found in the National Library of France. A French computer scientist (based in Israel), a German opera professor, and a Japanese physicist worked together to decipher them and discovered that they were written by Mary, Queen of Scots!

According to Smithsonian Magazine, 50 of the 57 letters were unknown. Mary, Queen of Scots expert John Guy said, ““This is the most important new find on Mary, Queen of Scots, for 100 years.”

The letters consist of 191 different symbols. The trio transcribed the 50,000 characters so they could be read by a computer, which used a hill-climbing algorithm that was able to decipher 30% of the text. The rest of the text had to be deciphered by hand. “The encryption turned out to be a homophonic cipher, in which each letter of the alphabet can be encoded in several different ways. Mary also used a number of dedicated symbols representing commonly cited words and people. An elongated “H,” for example, denoted the Earl of Shrewsbury, an English nobleman who served as the queen’s custodian during her time in captivity.”

If you like, you can read the findings of George Lasry, Norbert Biermann, and Satoshi Tomokiyo in Cryptologia Volume 47 (February 9, 2023).

I don’t remember all that much about Mary, Queen of Scots, so it was interesting to read in the Smithsonian article that during her 19 years of imprisonment she sent thousands of letters, employing “ciphers and codes of varying complexity” to “hide her messages from the prying eyes of Elizabeth’s spies.” (See a page of ciphers used by her on the UK National Archives website.) Pretty exciting that new discoveries about her are still being made almost 500 years later!