Matteo Argenti was in the second half of the sixteenth century, together with his uncle Giovanni Battista Argenti, the principal designer of ciphers of the Papal States. His are very original ciphers, often based on non-univoque systems, such as polyphonic ones, where the same cipher sign can have different meanings that will have to be solved based on the context.
To a certain extent similar are the variable-length mono-alphabetic digits: a monoalphabetic cipher is often based on two-decimal digits, from 00 to 99; even writing them all down the cryptanalyst will not have much trouble recognizing the individual signs. But if you mix two-digit signs and single-digit signs, it becomes much more complicated.
Many ciphers of this type can be found in the treatise on Argenti's ciphers found in Meister's book. Another much more recent example of such ciphers is the cipher known as the straddle checkerboard , used around the middle of the 20th century. More details on the The straddling checkerboard cipher .
An example of such a cipher, from the collection of Matteo Argenti, is the following, n. 19 of 1585 (Meister, page 343): cifra con monsignor eletto vescovo di Savona, nuntio in Savoya.
Note that there are homophones for some frequent letters; furthermore the single digit 4 which stands for a is distinct from the two-digits cipher 04 which stands for catholic cantons (indeed this cipher also included a small nomenclator that used other two-digits ciphers and some three-digits ones, and that is not reported here).
For example, if you want to encrypt the dispatch Iniziare rientro truppe si scriverà: 52438352249143912243829391399330328281.
The decipherer must rely on the context to resolve any ambiguity. The cipher above could also be deciphered in ioeiuettouaglielrre ... which should be discarded without making sense. ( 83 in the dictionary stands for Vettouaglie )
Argenti also devised ciphers that minimize these ambiguities; in the following cifra n. 8 per Monsignor Arcivescovo di Rossano, Nuntio a Napoli:
Argenti uses only the odd numbers 1, 3, 5, 7, 9 as single digits, while the two-digit numbers for the other letters always end with an even number, except for those that start with zero. In this way, ambiguity is almost impossible, but not entirely, among the letters of the alphabet. However, they remain so also considering the dictionary: for example 51 stands for Naples but using the alphabet would also be for ce, 73 stands for Prince of but using the alphabet would also be for bd. It is assumed that such ambiguities can be easily solved based on the context.
The previous example start shelling now in this case is encrypted as: 31934303392213623233824188239.
Below you can try this cipher; enter text in the window, then click "Encrypt". Do not insert texts that are too long. It should be noted that the examples above will generally be somewhat differently encrypted, due to the many homophones present. In case of homophones indeed, the encrypting function use a random number generator.
Please select one of the two ciphers: Cifra n.8 Cifra n. 19
Warning! Argenti's cipher used the 20-letter alphabet of the XVI century, which differs from today 21 letters Italian one, because there was as in Latin a single letter V in capital letters and u lowercase, so you will have to write u instead of v , otherwise the letter is ignored. Also j k w x y z will be ignored.