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# Cryptography

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## Enrica Maragliano

on 23 June 2014

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#### Transcript of Cryptography

Cryptography
What is it ?
Case Study
The word
CRYPTOGRAPHY
derives from the union of two greek words:
kryptós which means "covertly", and gráphein which means "to write"
So the criptography is about "the covertly script", with this kind of script we can write an obscure message for people who can not read it.
Cryptography is a very old science used to hide messages between kings and nobles in the past.

the scytale lacédémoniens is an old example of a system to enchiper messages using a cylindrical stick

The Second World War is the most important period of the criptology, when
Alan Turing,the father of the theoretical IT with the research group of
Bletchley Park formalized maths necessary for a systematic studying of the code book.
Enigma is one of the most important code-machine in the Second World War.
Claude Shannon, the inventor of the modern theory of the information, who in 1949
published an article called
Communication theory of secrecy
systems.
In Britain in 1943 was born the first electronic compute:"the Colossus", used to code the secret communication of enemies.
TEST
yesterday
yesterday
The code book
In 1976 in America was born the public-key cryptography.
In 1977 was born the public code book RSA.

what is a code book?
the code book is system which can transform a normal text in a unintelligible text
If you want to use a code book you have to do two different phases:
1)the encryption of the text;
2)the decryption of the cryptogram.

An example of code book is the CODE BOOK OF CAESAR:
Alice and Bob. Usually Alice wants to send a message to Bob. In 1978 Ron Rivest used those names in the article "Communications of the Association for Computing Machinery" which presented the cryptosystem RSA.
A video about the public key
CAESAR
Full transcript