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This is an Accepted Manuscript of an article published by Taylor & Francis in Cryptologia on 12 Feb 2018.
Abstract:
In his book ‘Noui et singolari modi di cifrare’, Giovan Battista Bellaso presents to his readers three challenge ciphertexts. Two of them are based on a polyalphabetic cipher with a mixed primary reciprocal alphabet and a long key, whereas the third one uses four independent homophonic substitution alphabets which change after each word. A successful approach to solving these ciphers, to which Bellaso gave the name ‘terzo modo’ and ‘quarto modo’, performs a simulated annealing attack directly on the primary alphabet respectively the four homophonic alphabets at once. This paper focusses on the various applied fitness functions. The solutions for the ciphertexts are given and finally discussed, with a view toward the possibility of a hidden message within the plaintexts.
The British Library holds, in the legacy of John Wallis, six ciphered letters from the French Court to Count Lauzun in Ireland. Five of them, undecipherable by Wallis, were from Minister of War Louvois; their contents are still considered unknown today. However, not only is the plaintext copy of one of these letters held by the Service historique de la défense in Vincennes, but also is the nomenclator used for all five to be found in the Bibliothèque nationale de Paris. Another letter from Naval Minister Seignelay to Lauzun, which Wallis was able to decipher to a large extent, can be found in the Archives nationales de France. In this article, all six letters are published in plaintext, four of them possibly for the first time.