# Italian trace in cryptography

Many of the readers know Caesar’s cipher, a rare cryptography textbook goes without mentioning it, but it’s still a cipher of the Roman Empire, like the cipher of another Caesar — ​​Augustus. The very fact of the existence of these ciphers leads to questions: “And what happened afterwards? Is this really over? ” In fact, it all just started and developed so well that traces of the work of Italian cryptographers can be found in the forms and rules for using modern means of cryptographic information protection.

### Renaissance

In an ordinary household, encryption is not a very necessary thing, but it is very useful for command and control of troops and trade. If you recall the history, it turns out that with the first and second in the territory of modern Italy until the middle of the 20th century everything was fine, sometimes even too much. Since the saturation of the history of Italy with events and persons is great, only two centuries will fall into this article - XV and XVI, the Renaissance. At the indicated time there is a struggle between Italy and Spain during which the following wars take place: the first Italian, the second Italian, the Cambrian League war, the third Italian, the Cognac League war, the third war of Francis I and Charles V, the fourth war of Francis I and Charles V - it was bored once. There is an acute and ongoing struggle even at the clan level: poisons, stilettos, scandals, intrigues, investigations are used.

### Defendants in the story

Beautiful Italian mathematicians, engineers, inventors - Scipio del Ferro , Leonardo da Vinci , Gerolamo Cardano , Leon Battista Alberti , Giovani Battista Bellaso , Niccolo Tartaglia , Lodovico Ferrari and many others live and feel good in this boiling Italian boiler. Without the Internet, they are bored, because from time to time they arrange mathematical battles among themselves, in which truly Italian passions boil. For example, Scipio del Ferro was the first to find a solution to the equation



${x}^{3}+ax=b$

Where



$a,b$

- positive numbers, but he spoke about this only to his son-in-law Annibal della Nava and the student Fiore. Fiore in the battle decided to poke another mathematician Tartaglia, but he decided them. Cardano, in turn, decided to find out the secret at Tartaglia, to which he responded with an encrypted verse .

### Crypto

A more significant contribution to cryptography was made by their colleagues. So, Leonardo da Vinci used mirror writing of his messages and sometimes elements of paintings. Now we know this elementary operation as a shift of elements.

Leon Batista Alberti writes his "Treatise on Ciphers" in which the first suggests the use of nonlinear replacement blocks, thus killing the possibility of frequency cryptanalysis. Non-linear replacement blocks, they are S-blocks still live in block ciphers (read on each computer), for example, in AES, GOST 28147-89 and others. Based on them, the notorious Enigma was built.

Gerolamo Cardano offers his Cardano lattice as a cipher, a very convenient cipher - it is easy to explain to students :), it is mentioned in several textbooks at once.

Giovanni Battista Bellaso writes that it would be nice to use a long key, to change the key every time. To the enemy did not guess! He also suggested using an autokey - deploying a key from some initial value. It is precisely “thanks to” him that the modern rules for the use of cryptographic information protection indicate the need for a periodic key change, and again, thanks to him, this change is carried out once a year or less.

### P.S.

Now you know someone to remember kindly when your key is “rotten” (its validity period unexpectedly expired). And the developers of the CIPF need not be remembered, they are bonded people, which is written in the regulatory framework, they do.

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