This document discusses old encryption algorithms from the classical method of cryptography, including replacement algorithms, the Caesar cipher, Vigenere cipher, Atbash cipher, and Affine cipher. It also describes the Jefferson cylinder, one of the strongest encryption devices of the time which was nearly unbreakable without stealing the entire device.

1. Cryptography
L03- Old Encryption algorithms

2. outline
 Old Encryption algorithms OR Classical Method
● Replacement Algorithms
● Caesar Cipher
● Full vigenere cipher
● Atbash Cipher
● Affine Cipher
● THE JEFFERSON CYLINDER
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3. Classical Method Cryptography
 Replacement Algorithms
This algorithm is deployed in the Middle Ages and this algorithm based
on replacing each character of the alphabet with another character
in a particular order.
The number of attempts needed to break this algorithm is 26! ,and it is
equal to almost 10264.
To be breached depending on the frequency of the original language
characters ,Where are calculated by testing a large number of texts.
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4. Classical Method Cryptography
 Replacement Algorithms
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5. Classical Method Cryptography
 Caesar Cipher
Julius Caesar has to find a way that they named after him in 58 BC.
This method is based on a comparison between each letter of the
alphabet with a letter last, depending on the value of rotation.
We do not need a lot of effort to prove the weakness of this simple
algorithm where they depend on the rotation and therefore the value
of knowing the value of the rotation loosen the entire encrypted
message.
And calculates the number of possibilities for the value of rotation in
the English language, we find that it is a small value of 26 field easily
break through the algorithm and the discovery of the original
message.
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6. Classical Method Cryptography
 Caesar Cipher
 Example : Word “SECRET” the encryption of this "VHFUHW“
where the rotation key is 3
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7. Classical Method Cryptography
 Full vigenere cipher
The Leon Battista Albert develop this algorithm in 1467 AD.
The code is used to switch between the appropriate disk letters.
The working principle of this algorithm depends on the encryption
table.
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8. Classical Method Cryptography
 Table of Full vigenere cipher
Example : the text “helloGreenDay” and key is “ForumForumFor”
The text after encryotion
became “Mscfalvyzlop”
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9. Classical Method Cryptography
 Atbash Cipher
This Cipher of the simplest types of Cipher which was originally the
Hebrew language.
But it can be used in other languages.
Mode of operation as follows :
To make the first letter in the language is the last letter and the second
character is the last before etc...
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10. Classical Method Cryptography
 Atbash Cipher
AZ
B Y
Etc >>>
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11. Classical Method Cryptography
 Affine Cipher
Encryption is a way Affine Cipher confusion between the two types of
encryption ,the first type, a Caesar Cipher and the second is the
product Cipher.
Caesar be in encryption mathematical relation :
C = p + key MOD n
Product Cipher be in encryption relation :
C = p * key MOD n
Affine code brought together the two previous two relationships :
C = m*p + key MOD n
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12. Classical Method Cryptography
 THE JEFFERSON CYLINDER
is one of the strongest encryption used in devices where the Cipher
generated strong can be broken easily never except in the case of the
theft of the entire device.
Name Jefferson back to its inventor THOMAS JEFFERSON Name.
This disc consists of some 36 wheel beside a row and 26, meaning that
each row by 36 character.
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13. Classical Method Cryptography
 THE JEFFERSON CYLINDER
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14. Thanks for watching
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