I uploaded a new article "French ciphers during the Reign of Henry III of France."
It includes more than a dozen ciphers of his reign that I reconstructed from materials in the French archives. The reconstruction was done some years ago, but it took time in organizing them into a preesntable format.
There remain many undeciphered letters, many of which can now be deciphered with the help of the reconstructed keys by those versed in the language and background.
There are also some ciphers still unidentified.
BnF 15572 f.91 was one of the first I worked on. I found the following text which I recorded some years ago. I decided not to include it in the article, but it may be of some interest in showing the difficulty posed by the handwriting. At the time, I was totally unfamiliar with the handwriting of this period (not that I'm familiar with it now).
ReplyDelete"BnF 15572
The last enciphered paragraph of f.91 is relatively short and gave a clue. The last word in the margin could be read as "aura par tout de la difficulte." But because nulls may be used at the end of the paragraph (as was indeed the case), one cannot match the letters with symbols yet. The two d's in the plaintext are spaced by three letters and I found a symbol which repeats with three-letter spacing. That symbol may be "d". Further, a symbol corresponding to "a" in "au... par" could be identified. The other repeating letters are enciphered with homophones and could not be identified at this time. This gave several symbols as a starting point and led to one discovery after another. When the first word of the paragraph (which was illegible in the handwriting) started to reveal a familiar name "Orleans", I was sure I was on the right track. In the end, some of the initial identifications were wrong. The identifications for "-fficulte" were all wrong by a shift of one place because the double letter "ff" was enciphered with a single symbol. I noted this only when the symbol for "t" in the ending "te" was identified (at first, I did not notice it was the same symbol with the initial "t" for "tout" because of the difference in handwriting). This means I took a symbol for "c" as representing "i" but at first I did not doubt the identification because "secours" turned into "sejours" still made sense! (This was part of one of the few plaintext letters written in alignment with the ciphertext, which seemed to be "laissent a" at first but turned out ot be "le secours"). I took a symbol for "l" as representing "n" until fairly late stage. The revelation came late partly because use of homophone made the symbol relatively infrequent.
There were other misleading clues in other paragraphs. The phrase identified in the plaintext "le roi de navarre" turned out to be encoded with one figure "76" (which I suspected from the fist anyway). What seemed to be "8e" but seemed to many turned out to be Sr (=sieur).
There were many other unsuccessful hypotheses I tried."