Cryptography, algorithms, Enigma machines | Appunti di Informatica

Cryptography

Cryptography is a method of protecting information and communications through the use of codes,

so that only those for whom the information is intended can read and process it. In computer

science, cryptography refers to secure information and communication techniques derived from

mathematical concepts and a set of rule-based calculations called algorithms, to transform messages

in ways that are hard to decipher.

Cryptography techniques

Cryptography is closely related to the disciplines of cryptology and cryptanalysis. It includes techniques

such as microdots, merging words with images, and other ways to hide information in storage or transit.

Procedures andprotocols that meet some or all of the above criteria are known as cryptosystems..

Modern cryptography concerns itself with the following four objectives:

1. Confidentiality: the information cannot be understood by anyone for whom it was

unintended

2. Integrity: the information cannot be altered in storage or transit between sender and

intended receiver without the alteration being detected

3. Non-repudiation: the creator/sender of the information cannot deny at a later stage his or

her intentions in the creation or transmission of the information

4. Authentication: the sender and receiver can confirm each other's identity and the

origin/destination of the information

Cryptographic algorithms

Cryptosystems use a set of procedures known as cryptographic algorithms, or ciphers, to encrypt

and decrypt messages to secure communications among computer systems, devices such as

smartphones, and applications. A cipher suite uses one algorithm for encryption, another algorithm

for message authentication, and another for key exchange.

History of cryptography

The word "cryptography" is derived from the Greekkryptos, meaning hidden. The origin of

cryptography is usually dated from about 2000 B.C., with the Egyptian practice of hieroglyphics.

These consisted of complex pictograms, the full meaning of which was only known to an elite few.

The first known use of a moderncipherwas by Julius Caesar (100 B.C. to 44 B.C.), who did not

trust his messengers when communicating with his governors and officers. For this reason, he

created a system in which each character in his messages was replaced by a character three

positions ahead of it in the Roman alphabet.

In recent times, cryptography has turned into a battleground of some of the world's best

mathematicians and computer scientists. The ability to securely store and transfer sensitive

information has proved a critical factor in success in war and business.

Enigma

Cryptanalysis of the Enigma system enabled the western Allies in World War II to read

substantial amounts of Morse-coded radio communications of the Axis powers that had been

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Cryptography Cryptography is a method of protecting information and communications through the use of codes, so that only those for whom the information is intended can read and process it. In computer science, cryptography refers to secure information and communication techniques derived from mathematical concepts and a set of rule-based calculations called algorithms, to transform messages in ways that are hard to decipher.

Cryptography techniques

Cryptography is closely related to the disciplines of cryptology and cryptanalysis. It includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit. Procedures and protocols that meet some or all of the above criteria are known as cryptosystems.. Modern cryptography concerns itself with the following four objectives:

Confidentiality : the information cannot be understood by anyone for whom it was unintended
Integrity: the information cannot be altered in storage or transit between sender and intended receiver without the alteration being detected
Non-repudiation : the creator/sender of the information cannot deny at a later stage his or her intentions in the creation or transmission of the information
Authentication : the sender and receiver can confirm each other's identity and the origin/destination of the information

Cryptographic algorithms

Cryptosystems use a set of procedures known as cryptographic algorithms, or ciphers, to encrypt and decrypt messages to secure communications among computer systems, devices such as smartphones, and applications. A cipher suite uses one algorithm for encryption, another algorithm for message authentication, and another for key exchange.

History of cryptography

The word "cryptography" is derived from the Greek kryptos , meaning hidden. The origin of cryptography is usually dated from about 2000 B.C., with the Egyptian practice of hieroglyphics. These consisted of complex pictograms, the full meaning of which was only known to an elite few. The first known use of a modern cipher was by Julius Caesar (100 B.C. to 44 B.C.), who did not trust his messengers when communicating with his governors and officers. For this reason, he created a system in which each character in his messages was replaced by a character three positions ahead of it in the Roman alphabet. In recent times, cryptography has turned into a battleground of some of the world's best mathematicians and computer scientists. The ability to securely store and transfer sensitive information has proved a critical factor in success in war and business. Enigma Cryptanalysis of the Enigma system enabled the western Allies in World War II to read substantial amounts of Morse-coded radio communications of the Axis powers that had been

enciphered using Enigma machines. This was considered by western Supreme Allied Commander Dwight D. Eisenhower to have been "decisive" to Allied victory.[1] Until the release of the Oscar-nominated film The Imitation Game in 2014, the name ‘Alan Turing’ was not very widely known. But Turing’s work during the Second World War was crucial. Alan Turing was a brilliant mathematician. He was already working part-time for the British Government’s Code and Cypher School before the Second World War broke out. In 1939, Turing took up a full-time role at Bletchley Park in Buckinghamshire – where top secret work was carried out to decipher the military codes used by Germany and its allies. The main focus of Turing’s work at Bletchley was in cracking the ‘Enigma’ code. The Germans increased its security at the outbreak of war by changing the cipher system daily. This made the task of understanding the code even more difficult. Turing created a machine known as the Bombe. This device helped to significantly reduce the work of the code-breakers. From mid-1940, German Air Force signals were being read at Bletchley and the intelligence gained from them was helping the war effort. In 1936, Turing had invented a hypothetical computing device that came to be known as the ‘universal Turing machine’. After the Second World War ended, he continued his research in this area, building on his earlier work and incorporating all he'd learnt during the war. While working for the National Physical Laboratory (NPL), Turing published a design for the ACE (Automatic Computing Engine), which was considered the forerunner to the modern computer..

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