@1996-2019 Paolo Bonavoglia
Cryptography from Atbash to RSA

Classical cryptography(*)
Contemporary cryptography
Math for cryptography

Cryptography is a word of Greek origin for secret writing; it is therefore the art of writing secret messages that can be read and understood only by the recipient; a technique that dates back to the most remote antiquity, if the Bible already speaks of a secret cipher for writing the name of Babel ( Atbash ).

For centuries cryptography was almost exclusively the preserve of military and diplomats, and secret messages traveled materially entrusted to trusted couriers.

Between the nineteenth and twentieth centuries this picture has radically changed: the invention of the telegraph, telephone and radio have made it possible to transmit almost instantaneously messages from one point to another of the globe; on the other hand radio communications even more than telephone ones are exposed to interception by the enemy, and hence the need to encrypt all the confidential messages transmitted by radio.

Macchina Enigma In the second half of the 20th century the invention of the computer and the internet have changed the scenario even more radically; most old cryptographic systems, manual or machines, have suddenly become obsolete partly due to the ease with which they can be forced with the help of the computer, partly due to the inconvenience and slowness of use.

The need to communicate information in a confidential manner and therefore to encrypt messages has extended well beyond the diplomatic-military sphere. Today, those who withdraw money from an ATM, those who make purchases on the Internet with a credit card, and those who make a phone call with their mobile phone often use cryptographic techniques without realizing it.

Cifra Feistel → DES Inevitabile in questo contesto la nascita di cifrari completamente nuovi come il DES della IBM e il rivoluzionario RSA capostipite dei cifrari a chiave pubblica, e all'inizio del XXI secolo il nuovo AES che ha sostituito il DES, ormai obsoleto.

Updates and news
International Conference on Historical Cryptology 2020, Budapest (Hungary), June 15-17

International Conference on Historical Cryptology 2019, Mons (Belgium), June 23-26

Risolto l'enigma della Cifra delle caselle

Ritrovata a Venezia la cifra di G.B. Bellaso del 1552

International Conference on Historical Cryptology 2018, Uppsala

European Conference on Historical Cipher 2017, Smolenice

Decrittato dopo un secolo e mezzo l'ultimo poema di Pietro Giannone

I cifrati di Antonio Marzi


The titles in Italian point to pages available only in Italian. Work in progress! It will take time!