I read of a partially enciphered letter addressed to Napoleon's general during the Peninsular Campaign (Cipherbrain). It is a dispatch of Clarke, Minister of War in Paris, to General Caffarelli in Spain dated 19 October 1812. Karsten Hansky acquired it at an auction site and described it in "A dispatch from the French Minister of War Clarke to General Caffarelli, the commander of the Northern Army in Spain, from the year 1812" (17.06.2021) (pdf).
The passages in code are short, but the plaintext is attached. The code in use is what wac called "Great Paris Cipher" by the British (see also my article "Great Ciphers of Napoleon's Grande Armée"). It is code table #24 in the archives of the SHD (Service Historique de la Défense) in Vincenne (SHD box 1M-2352).
What is interesting to me is the marginal note including the coded message (apparently) transcoded into another code (#29). From the range of numbers, the code #29 appears to have about the same size as #24, but the number of codegroups is different (that is, there is no one-to-one correspondence between the code groups.)
I now included a reference to this transcoding in "Great Ciphers of Napoleon's Grande Armée".
ReplyDeleteAlso I included an additional link to a reconstructed key of the small cipher between Marmont and Jardet. I found it in a search of the Spanish archives, after which I noticed I prepared the image back in 2018, but has not uploaded it.