Codebreaking through Comparison of Two Independently Enciphered Texts

I uploaded a new article "Codebreaking through Comparison of Two Independently Enciphered Texts", which presents my solution of a cipher used in a letter from Abel Servien to Melchior de Sabran (1632). It was quite simple a job, because some words in the clear gave a clue. More interesting would be the very comparison of the two independently enciphered ciphertexts.
I also added references to unsolved ciphers in Sabran's letters in "French Ciphers during the Reign of Louis XIII" and "Unsolved Historical Ciphers."

 

 

Colbert de Croissy Switched to Numerical Cipher in Italy, but Reverted to Figures with Diacritics in London

I made several additions, mainly related to Colbert, to "Ciphers Early in the Reign of Louis XIV" and "French Ciphers during the Reign of Louis XIII" from the Baluze collection in BnF. In this update, the most interesting is the changes of ciphers used by Colbert de Croissy. He used cipher consisting of figures with diacritics, typical in French ciphers at the time, in 1659 (DE=28) and 1660 (DE=42~) when he was Intendant of Alsace. But he switched to a purely numerical cipher (1660-1661) during his mission to Rome (DE=91). He used another numerical cipher in Cleves in 1666 (DE=151), but reverted to figures with diacritics (1668-1674) in his London embassy (DE=68). Somehow, specimens of purely numerical ciphers in France are often related to Italy.

A Cipher between Cardinal Mazarin and Anne d'Autriche

I added a section "Mazarin-Anne d'Autriche Cipher (1651)" in "Cardinal Mazarin and Ciphers". Although the nomenclature of the cipher is printed in Ravenel (1836), the substitution alphabet is not included therein. I reconstructed the substitution cipher by comparing the manuscript letters and the version printed in Ravenel (1836). (Though Ravenel suggests the manuscript key is extant, I could not find it online.)

Cardinal Mazarin Used Partially Two-Part Code

When I posted "Cardinal Mazarin and Ciphers", I thought Mazarin's letters in cipher would not be available online (this is why the article is not titled "Cardinal Mazarin's Ciphers") and thought his cipher might be little more than a short nomenclature, judging from a specimen printed in Ravenel (1836).
Contrary to my expectations, I found a specimen that shows Mazarin('s secretary) used two-part code in June 1651 during his exile in Germany (though the arrangement is not completely random). It is the same cipher as the one used between Le Tellier and Colbert in December 1650. At present, I think the Le Tellier-Colbert cipher was given to Mazarin, who went to exile in Germany, rather than Le Tellier and Colbert were using the cipher given by Mazarin. More specimens are necessary to make a call.
I now added a section "Mazarin's Cipher" to describe these findings.

Note (16 October 2021): The original title of this post was "Cardinal Mazarin Used Two-Part Code." Although I included a reservation "the arrangement is not completely random" in the body, I thought I should add "Partially" in the headline, too (see today's post).