Decrypted Renaissance Dead Letters

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From Inverse:

Simon and Marie de Brienne were the 17th century’s most active postmaster and postmistress, delivering personal and political letters alike across Europe. But the Briennes also had a secret.

In addition to delivering letters, they stored away for thousands of “dead letters” — the typically discarded letters belonging to recipients who couldn’t pay postage. Rediscovered in 1926, the Brienne’s trunk is the final resting place of over 5,000 letters. Nearly half have never been opened for fear of destruction.

Now, using X-ray microtomography instead of a letter opener, a team of scientists has opened one of these letters for the very first time and demonstrated their pioneering new system on four letterpackets from Renaissance Europe.

This system gives scientists a powerful new tool for accessing the daily-lives of Renaissance people and for better understanding what the personal, professional, and political pressures of the day might have been like.

It also offers scientists an opportunity to explore one of history’s ancient security measures, a “letterlock.” This is an early, physical predecessor to today’s modern cryptography.

“[W]e developed virtual unfolding to prove our letterlocking theories, and elucidate a historically vital — but long underappreciated — form of physical cryptography,” write the authors.”

. . . .

Long before the invention of email, or even bitter-tasting lickable envelopes, Renaissance correspondents had to think more creatively about the safety of their epistolatory works. One way that these letters were kept safe, write the authors, was through intricate, origami-like letterlocks.

“Before the proliferation of mass-produced envelopes in the 1830s, most letters were sent via letterlocking, the process of folding and securing writing [materials] to become their own envelopes,” the authors explain.

“Letterlocking was an everyday activity for centuries, across cultures, borders, and social classes, and plays an integral role in the history of secrecy systems.”

The authors write that in their study of 250,000 letterlocked messages (beyond the Brienne haul) from the “Renaissance world,” they discovered a spectrum of security systems, ranging from simply sealed to booby-trapped letters with tamper-evident locking mechanisms to deter “man-in-the-middle” attacks.

In other words, a mechanism that would secretly signal to the recipient if others had snuck a peek at their secret writing.

A striking discovery made during their research was the successful virtual unfolding of a never-before-opened letter from July 1697 from Frenchman Jacques Sennacques to his cousin Pierre Le Pers requesting a certified copy of a death notice for one Daniel Le Pers.

“Before computational analysis, we only knew the name of the intended recipient, written on the outside of the letter packet,” write the authors.

As these “dead letters” were often never delivered due to either insufficient postage or the death of the recipient, one can wonder if Pierre Le Pers joined Daniel before receiving this final postage.

While the contents of this letter weren’t necessarily world-changing secrets, the authors write that the success of their approach could be used in the future to unlock even more long-forgotten secrets from this era.

The letters, quite simply, are also difficult to read — despite being technically legible. The study authors note that the “idiosyncrasies of a hand” can make it difficult to determine the actual context of letters; paleographers have to use contextual clues and linguistic knowledge to fill in when text is messy or missing. Other times, wormholes have made it impossible to determine a word.

Link to the rest at Inverse

(PG apologizes for the “snuck” in the OP)