Giovanni Soro [Zuan Soro] was a great cryptanalyst in Venice in the first half of the sixteenth century. (Zuan is the spelling used by himself; Giovanni is the form in modern Italian.) He left a book on cryptanalysis to the Council of Ten (governing body of Venice), but it has been lost since then. Bonavoglia (2022) speculates an anonymous treatise mentioned below may be Soro's lost treatise, but also points out it is in Tuscan Italian (which formed the basis of modern Italian), but at the time, it was "unusual but not impossible" for Venetians to have used it. (Bonavoglia (2022) sections 3, 6.5, 9)
When Soro died in 1544, there were four successors: Alvise Borghi, Giambattista de Ludovici, an engineer just known as Giovanni, and Zuan Francesco Marin. The ablest was Marin, who later became the official trainer of cifristi in 1576. When he died in 1578, no trainer was appointed for more than a decade, and Marin's papers, consigned to the state, provided the basis for training. (Iordanou (2019) p.141-143, Bonavoglia (2022) p.24-27)
The Venetian archives has "ASVe CX Cifre, chiavi e scontri di cifra ...", which consists of several bustas. Busta 3 has Venetian cipher keys, among which are also found some deciphered keys. Busta 6 [b.6] includes Marin's collection detailed in Bonavoglia (2022), including writings of Marin as well as Ludovici, his elder, as well as a copy of the famous treatise of Alberti. B6.1 includes, among others, demonstrations of codebreaking of a syllable cipher called babuino, the term derived from "ba-be-bi-bo-bu." (Bonavoglia (2022) section 6, esp. p.24, 25)
Busta 6.2 (b6.2) is an anonymous booklet of 64 pages in 8 folders (with one folder comprising 8 pages in 2 sheets), which is in Marin's hand up to carta 13. Bonavoglia points out that the hand does not prove authorship, and noting the style is different from that of Marin's writing and also that the author all but claims that he was the first to write about cryptanalysis, speculates that this may be the lost treatise of Soro. (Bonavoglia (2022) sections 6.5, 9)
Agostino Amadi's treatise on cipher describes techniques of Soro, Ludovici, and Marin "in a systematic and comprehensible form." (Bonavoglia (2022) p.29).
Amadi used it as a textbook for teaching cryptography and cryptanalysis (Bonavoglia (2020) n.17, Bonavoglia (2021) p.6, n.67). It was handed over to the Council of Ten when he died in March 1588. The Council adopted it as a training manual for personnels in their cryptologic department (Iordanou (2019) p.130, 143).
It is in busta 7 (Meister (1902) p.24) and is cited as:
ASV (Archivio di Stato, Venice), IS, b.1269 (Iordanou (2019) p.130, 143) or
Agostino Amadi. 1588. Trattato delle cifre [Trattato delle Zifre]. Digitized manuscript in ASVe, Inquisitori di Stato, Codice Amadi, Venezia. (Bonavoglia (2020), Bonavoglia (2021))
It consists of about 700 jpeg files, accessible in the Scholar Room of the Venetian Archives (Bonavoglia (2022) n.38).
According to Meister (1902), who considered this was the most important treatise in the Venetian state archives, the treatise consists of the following ten volumes:
1. (68 leaves) various types of cipher (a breakdown is found at DPJA Scheer's webpage)
2. (68 leaves) foreign unknown ciphers (a breakdown is found at DPJA Scheer's webpage)
3. (64 leaves, with 3 blank) "Polistenographia" (steganography)
4. (37 leaves) "Apocriptografia"
5. (4 leaves) invisible writing
6. (6 leaves) "ultimo volume de le zifre cioe la somma d'Agostino Armadi." (summary)
7. (29 leaves) examples, keys and rules of Amadi
8. (11 leaves?) 76 ciphered instances
9. (8 leaves) explanation of the examples above
10. (3 leaves) again, various cipher examples
As far as cryptanalysis in the 16th-century Venice is concerned, the volume II is the best source is volume II in Agostino Amadi's treatise on cipher (Bonavoglia (2021)).
Aloys Meister (1902), Die Anfange der Modernen Diplomatischen Geheimschrift p.24-25
Paolo Bonavoglia (2022), "Venetian Cryptanalysis Treatises of the Renaissance" (HistoCrypt 2022)
Paolo Bonavoglia (2021), "The ciphers of the Republic of Venice an overview", Cryptologia, DOI: 10.1080/01611194.2021.1901797
Paolo Bonavoglia (2020), "A Partenio’s Stegano-Crypto Cipher" (pdf)
Ioanna Iordanou (2019), Venice's Secret Service: Organizing Intelligence in the Renaissance, Oxford University Press