The Decrypt Project Cracks Historic Codes With Algorithms
Academics are using modern tech to read the secret messages of history’s serial killers and imprisoned royalty.
In this May 3, 2018, file photo, a San Francisco Police Department wanted bulletin and copies of coded letters sent to the San Francisco Chronicle by a man who called himself Zodiac are displayed in San Francisco.
Photographer: Eric Risberg/AP Photo
More than 400 years ago, Mary, Queen of Scots was imprisoned in an English castle on charges that she’d conspired against Queen Elizabeth I, her cousin. As she tried to save her head, Mary wrote dozens of secret letters to friends and allies. In several of them, she discussed with France’s ambassador how rivals had abducted her son; in others she complained about conditions of her captivity and said she supported a controversial marriage that would’ve aided a political alliance between France and England.
Mary used a “spiral locking” technique to fold the letters, so the recipients would be able to tell if anyone had opened them before they were received. She and her associates also corresponded in a complex code, which protected the content for 436 years. Then in February, a group of codebreakers detailed in a paper how they’d designed a computer system to break it. In the paper, they showed how Mary had used a type of encryption known as a complex homophonic cipher, substituting various symbols for individual letters of the alphabet.