Chapter one of Simon Singh’s The Code Book begins with two stories. The first one is about Mary Queen of Scots and the second one is about Demaratus, an exiled Greek who nevertheless worked to communicate secretly with his homeland. While both of their stories were told to establish a theme of secret writing, the two stories have very little else in common.
Demaratus’s story is one of a brave and cunning man who, upon learning of a Persian plot against his homeland, found a way to conceal the existence of his message so it could reach its destination safely. His heroics allowed the Greeks to prepare a fleet to meet the advance of Xerxes’s fleet and defend themselves from an attack that would otherwise have caught them completely off guard. Demaratus’s successful use of steganography, the act of concealing the existence of a message, allowed him to save Greece from a major military defeat.
The story of Mary Queen of Scots did not end as pleasantly for Mary as Demaratus’s did for the Greeks. Mary had concealed her message using cryptography rendering it unreadable to those who did not have the cipher, rather than by hiding its existence in the first place. The fate of her life hung, not on whether or not her message would be discovered, for it already had been, but rather on whether it could be deciphered. Her encrypted message was, unfortunately for her, in the hands of a man named Thomas Phelippes, one of the finest cryptanalysts of his day. He eventually succeeded in decrypting the message and laid bare a plot by Mary to assassinate Queen Elizabeth and take the English throne. She was relieved of her head shortly thereafter.
There are several differences between these two stories. Obviously, one story sees the message successfully and discreetly transported to its intended audience, while the other one has the message discovered and decrypted. In addition, the British one is likely more factual, as it is based on historical data and physical records, rather than the legends and folklore that likely drive much of Heroditus’s account of Demaratus. Finally, the type of secret writing involved varies between the two. In the Ancient Greek story, Demaratus used steganography to conceal the existence of his message whereas Queen Mary of Scots relied on cryptography to keep the contents of her message a secret even once the message had been discovered.