Emperor Charles V’s secret code cracked after 5 centuries

It took the team at the Lorea Research Laboratory six months to decipher the letter written by Charles in 1547.


A team of researchers has unearthed a five-century-old code that reveals a rumored French plot to kill Charles V, Holy Roman Emperor and King of Spain.

Charles was one of the most powerful men of the 16th century, presiding over a vast empire that covered much of Western Europe and the Americas during a reign of more than 40 years.

It took a team at the Loria research laboratory in eastern France six months to decipher a letter written by the emperor to his ambassador in France in 1547.

The tumultuous period saw a sequence of wars and tensions between Spain and France, then ruled by the Renaissance emperor Francis I, who had brought Leonardo da Vinci from Italy.

The letter from Charles V to Jean de Saint-Maurice was forgotten for centuries in the collection of the Stanislaus library in Nancy.

Cecil Pierrot, a cryptographer from Lorraine, first heard of its existence at a dinner in 2019, and after much searching was eyeing it in 2021.

He told reporters on Wednesday that as with Charles V’s signature, it was mysterious and completely incomprehensible.


In painstaking work assisted by computers, Pierrot found “distinct families” of about 120 symbols used by Charles V.

“Whole words are encrypted with a single symbol” and the emperor replaced vowels coming after consonants with numerals, she said, an inspiration probably coming from Arabic.

In another obstacle, he also used symbols that mean nothing to mislead any adversaries trying to understand the message.

The breakthrough came in June, when Pierrot managed to make out a phrase in the letter, and then the team cracked the code with the help of historian Camille Descenclos.

“It was painstaking and long work but really a breakthrough that happened in one day, where suddenly we got the right hypothesis,” she said.

Another letter from Jean de Saint-Maurice, where the receiver had doodled a form of transcription code in the margin, also helped.

– More discoveries to come –

Descenclos said that “it was rare as a historian to manage to read a letter that no one had managed to read for five centuries.”

He added that this “confirms to some extent the poor state of relations” between Francis I and Charles V in 1547, who had signed a peace treaty three years earlier.

But relations between the two were still strained, with various attempts to undermine each other, she said.

Desenclos went so far as to reveal a nugget of information rumored to be an assassination plot against Charles V, which was said to be underway in France.

She said that there was “not much information” about the plot but that it underscored the “fear” of the monarch.

Researchers now hope to identify other letters between the emperor and his ambassador “to take a snapshot of Charles V’s strategy in Europe”, she said.

“It is likely that we will make many more discoveries in the years to come,” the historian said.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

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