CRYPTOGRAPHY

cryptography is the science that studies how to encrypt a Message to make it intelligible only to those who know the key.

Used for centuries almost exclusively in military and diplomatic environments today cryptography involves us daily: just think of credit cards, GSM communication of mobile phones or smart cards used for viewing satellite programs; PGP software to encrypt emails, e-commerce via internet, privacy protection or public order, the security of computer networks and so on.

The development of cryptographic technique is based on two basic mechanisms: transposition and/or replacement, i.e. changing the order of the elements of the text or replacing them with others.

The fundamental stages were: the Greek scitale (V century BCE), the Rosetta Stele (196 BCE), the cipher of Giulio Cesare (102-44 BCE), the cipher disc of Leon Battista Alberti (1466), the table of Vigenère (1562 ca.), the electromechanical machine enigma, used by the Germans during the Second World War, the “bomb” of A. Turing (1941), Colossu

After contributing to the birth of the computer, cryptanalysis continued to employ and improve computer technology and each encryption process is now computerized and uses the private or symmetric key system and asymmetrical or public key system.

There are different types of algorithms (mathematic methods) that allow the use of a public key. The most widespread is the RSA (1977) which is based on the difficulty of identifying a number as a product of two first numbers. It is estimated that even working with all computers in the world at the same time, to discover a key of 1,024 digits (current military keys are 2.048 digits) would take an equivalent time to the age of the universe (15 billion years).

The first numbers, which are the basis of modern cryptographic systems, are now an integral part of our everyday life.