A coded letter signed in 1547 by the most powerful ruler in Europe has been cracked by French scientists, revealing that he lived in fear of an assassination attempt by an Italian mercenary. Sent by the Holy Roman Emperor Charles V to his ambassador at the French royal court … the letter gives an insight into the preoccupations of Europe’s rulers at a time of dangerous instability caused by wars of religion and rival strategic interests.
The three-page letter – consisting of about 70 lines – is mainly written using about 120 encrypted symbols, but there are also three sections in plain contemporary French. “The first thing was to categorise the symbols, and to look for patterns. But it wasn’t simply a case of one symbol representing one letter – it was much more complex,” says [cryptographer Cecile] Pierrot. “Simply putting it into a computer and telling the computer to work it out would literally have taken longer than the history of the universe!”…
The rarity of the letter ‘e’ is a sign that the codemakers knew their stuff. Because ‘e’ is the most common letter (in old as in modern French), it is what codebreakers would be looking for first. And the fake symbols were simply put in to sow more confusion.
“Of course by today’s standards it is pretty basic,” says Pierrot, who spends her normal time thinking about quantum physics and massive prime numbers. “But given the tools they had, they certainly put us to work!”
February 1547 was a time of rare relative peace between the rival powers of France and the Holy Roman Empire. Emperor Charles V – ruler of vast areas including Spain, the Netherlands, Austria, Hungary and southern Italy – was no longer actually at war with King François I. But mistrust still prevailed.
Two recent events were in both rulers’ minds. The first was the death of Henry VIII just a few weeks before. And the second was the rebellion in Germany by a Protestant alliance called the Schmalkaldic League. In the letter, Charles V reveals his concern to maintain the peace with France so that he can focus his forces against the League. He tells the ambassador to keep himself abreast of thinking in the French court, in particular any reaction to the death of King Henry. What he wants to avoid above all is the French and English combining to lend more assistance to the Protestant rebels.
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