Whereas most ciphertexts look similar, being a stream of arbitrary symbols or Arabic figures, a class of Venetian ciphers produce a distinct appearance: a series of letters with superscript digits or exponents. Such a system was introduced to handle the increasing vocabulary (Meister (1902) p.21). In the same period, Venetian ambassadors also used ordinary symbol ciphers. Ciphers for ambassadors in Constantinople had a large vocabulary by arbitrary symbols without superscirpts (Pasini (1872), p.44, p.63; p.45, p.64). (Cryptologically, superencryption discovered by Bonavoglia (2019) is more interesting, but is off-topic herein.)
The cipher, known as the Zifra Granda or Ziffra Granda, reproduced in Fig. 1 of Bonavoglia (2019) from the book of ciphers 1578-1587 (ASVE, CX Cifra, chiavi e scontri di cifra con studi successivi , busta 4, reg. 16; ASVe gives "buste 8, registri 1") has a nomenclature of some 500 entries, whereby syllables and words are represented by a letter (h, f, p, L, r, a) followed by one or two digits. (In actual use, the digits are often written as superscripts.) There is regularity in the arrangement. In particular, Bonavoglia (2019) points out that syllables -a, -e, -i, -o, -u are consistently given digits ending in -1, -2, -3, -4, -5, respectively (Fig. 2).
The substitution table assigns each letter three homophones: a polywog (a circle with a rightward stroke), turned T (a vertical bar with a rightward stroke), and u with superscript digits. Similar polywog or arrow-like symbols are also used in Spanish ciphers (see Leyva's Cipher and Cp.44 in another article).
Ms. 994 of National Library, Madrid, contains an undeciphered letter from Venetian secretary Marco Otthobon [Marco Ottobon] to ambassador, Juan Mocenigo [Giovanni Mocenigo], dated 27 April 1589. Valle de la Cerda appears to have solved it, but his solution is lost. See another article. (This is placed in this section simply because its date is close to that of the above cipher. There is no evidence to indicate that the cipher has a regular assignment of symbols.)
Similar ciphers with superscript digits used by some Venetian ambassadors are more irregular.
Giovanni Michiel (Dizionario Biografico, vol.74 (2010)) was ambassador in England in 1554-1557.
His cipher was solved by Paul Friedmann (1869), and corrected by Pasini (1872). It has more irregular arrangement as compared with the Zifra Granda above. Pasini (1872) and Bonavoglia (2020) present passages in this cipher, which allows partial reconstruction of the cipher (Pasini (1869) appears to reproduce the whole reconstructed cipher, but the plate after p.9 is not properly scanned in Google's copy.).
It does not show an apparent regularity as seen in the Zifra Granda above.
Digits 3, 8, and 9 are not used (Pasini (1872) p.45).
A passage of a letter of 19 September 1553 by Giacomo Soranzo (Dizionario Biografico, vol.93 (2018)), ambassador in England (1550-1554) before Michiel, is presented in Bonavoglia (2020). As far as this specimen is concerned, it is the same as Michiel's cipher above except for d65 for "Sua Maesta", which is t25 in Michiel's cipher. Pasini (1869) lists several differences between Michiel's and Soranzo's ciphers (p.14).
The cipher used by Marc'Antonio Da Mula and Federico Badoer (Dizionario Biografico, vol.5 (1963)), ambassadors in Spain, was the same as Michiel's (Pasini (1872) p.44).
The cipher used by Antonio Tiepolo (Dizionario Biografico, vol.95 (2019)), ambassador in Spain (1564-1567) is different from Michiel's. Pasini (1872) presents a passage of his letter of 8 April 1566 (p.44).
Spanish cipher Cp.31 for an ambassador in Rome (1579-1585) also uses superscript digits in the nomenclature. But unlike Venitian ciphers above, syllables are represented with diacritics (vowel indicators) (see another article).
Michiel Surian, ambassador in England (1557-1558) succeding Giovanni Michiel, used a cipher with superscript letters (Bonavoglia (2020), Pasini (1872) p.43). Again, the arrangement is irregular. The following is a reconstruction from the specimens presented in Bonavoglia (2020).
A cipher used in a letter (1519) from the Senate to Marco Minio, ambassador in Rome (appointed in 1516, arrived in 1517 (Dizionario Biografico, vol.74 (2010))) is said to "resemble radically" Michiel's cipher (CSP).
BnF Clair. 327 (Gallica), ff.279-280 is an unsigned letter of 11 April 1528 to Seigneur Garbino. The paragraphs in cipher are not deciphered. A seemingly contemporary addenda (see the next section) suggests the base letter of the cipher symbols with exponents indicates the initial of the word/syllable represented.
A memoire in Italian, dated Madrid, 11 April 1528 also uses a similar cipher with superscript figures (BnF fr.3022 (Gallica), f.44). Probably, it is a report of a Venetian agent in Madrid.
BnF Clair. 314 (Gallica), f.337 is an addition to a cipher, listing entries such as apresso (a327), Cartagenia (c327), Perilche (p400), scorn (s400), Zabre (z37)). The base letter indicates the initial of the word represented. Probably, the original cipher had entries a1, ..., a326, and the entries in the "A" section in this addition continue the sequence.
F.338 appears to be a list of code words such as Antonioto Adorno (Andrea de Passano), Antonio de Leyva (Agostino Spinola), Ambassiatore (Thesorero). These names suggest the list belongs to the 1520s (or 1530s).
(The same addenda and jargon are also found in BnF fr.3022 (Gallica), f.96-102. This was brought to my notice by Norbert Biermann's comment on Cipherbrain.)
Several undeciphered letters of Hieronimo Ranzo use similar ciphers with superscript figures (BnF fr.2988 (Gallica) f.2, f.9-10; BnF fr.3019 (Gallica) f.73-74; BnF fr.20506, f.136 (a copy of BnF fr.2988, f.9, which Norbert Biermann pointed out to me)). Hieronimo Ranzo served the Count of Gattinara (Wikipedia, Treccani), chancellor of Emperor Charles V, and is recorded as one of the witnesses of the Treaty of Saragossa (Wikipedia) (1529) (The text of the treaty reads as if Augustin de Urbano had been the chancellor, as quoted in Davenport (ed.) (2004), European Treaties bearing on the History of the United States and its Dependencies to 1648, p.197 (Google), but Augustin de Urbina was secretary of the chancellor according to Documentos para el quinto centenario de la primera vuelta al mundo: Tratado de Zaragoza (sevilla.2019-2022.org)).
The Ranzos was a noble family of Vercelli, and Gattinara's mother, Felicita Ranzo, was also from the family. Hieronimo Ranzo was a courtier of Charles V. (I was made aware of these by Thomas Bosbach's comments in Cipherbrain)
It is wondered whether Ranzo had any connection with Venice to use this kind of cipher.
By the way, Ranzo's cipher letter in BnF fr.2988, f.2, is preceded by another ciphertext on f.1. Since f.1 and f.2 are treated as one item in catalog information, I wondered whether one is an enclosure of the other. But it turned out that f.1 probably belongs to the latter half of the century, addressed to Mary Queen of Scots (see another article).
A cipher of Vergerio (?Wikipedia) printed in Rockinger (1891) also has supercripts.
A cipher from Prague printed in Rockinger (1891) also has supercripts.
Paolo Bonavoglia (2020), "Decifra dispacci veneziani"
Paolo Bonavoglia (2019), "Hieronimo di Franceschi and Pietro Partenio: Two Unknown Venetian Cryptologists" (pdf), Proceedings of HistoCrypt2019
Luigi Pasini (1872), Delle scritture in cifra usate dalla Repubblica di Venezia, reprint (2019) as Crittografia book series 2, edited by Paolo Bonavoglia; also included in as Appendix of Parte I in Cecchetti (1873), Il regio Archivio generale di Venezia (Google), p.289
Luisi Pasini (1869), I dispacci di Giovanni Michiel: ambasciatore veneto in inghilterra : 1554 - 1557 (Google)
Paul Friedmann (1869), Les Dépèches De Giovanni Michiel, Ambassadeur De Venise En Angleterre pendant les années de 1554 à 1557, déchifrées et publiées d'aprè les documents conservées aux archives nationales de Venise (Cited by Pasini (1872). I have not seen this.)
J.P. Devos (1950), Les chiffres de Philippe II (1555-1598) et du Despacho universal durant le XVIIe siècle
Aloys Meister (1902), Die Anfange Der Modernen Diplomatischen Geheimschrift
CSP Venice, vol.2 (1867) 'Appendix II: Italian Cipher', pp. lxix-lxxii (British History Online)
Dizionario Biografico degli Italiani (Treccani)
Ludwig von Rockinger (1891), Ueber Geheimschriftenschlüssel der bayerischen Kanzlei im sechzehnten Jahrhundert (1891) (Google)