The Farnese letter

summary

A long-unsolved 1542 letter from Cardinal Alessandro Farnese was deciphered using a combination of statistical analysis, a five-gram Italian language model, and simulated annealing. The process involved recovering a monoalphabetic key where letters were represented by one or two digits, and then refining the transcription through a fixed-key decoder that accounted for human error in the original manuscript. This technical achievement reveals diplomatic tensions regarding naval expenses and military movements against the Ottoman Empire during the Renaissance.

key points

1. The author used a beam search and simulated annealing to test random key assignments, scoring them against a language model trained on millions of letters from Renaissance authors like Machiavelli and Vasari.
2. To correct transcription errors, a fixed-key decoder was implemented with specific edit costs for substituting or inserting digits, which was then validated by comparing the results against high-resolution photographs of the original manuscript.
3. The decoded text exposes high-level papal diplomacy, including the Pope's reluctance to commit funds to a hundred-ship fleet due to timing and efficiency concerns, and reports on the fortification of castles in Parma.

who should read it

Historians of the Renaissance, cryptanalysts, and computer scientists interested in the application of machine learning and probabilistic models to historical linguistics.

discussion skeptical