Caesars Cipher Cryptography





Caesars Cipher Cryptography

Julius Caesar is supposed to have used the Caesar cypher, which is a classic example of ancient encryption. The Caesar cypher is based on transposition and requires changing each plaintext letter by a particular number of letters, usually three, as shown in Figure 5.1. By performing the same amount of shifts in the other way, the ciphertext may be decoded. Because of the continuous substitution of one letter for another, this sort of encryption is known as a substitution cypher.

The Caesar Cipher technique is one of the oldest and most basic ways of encryption. It's just a substitution cypher in which each letter of a given text is substituted with a letter from a set number of places down the alphabet. With a shift of 1, for example, A would be replaced by B, B would become C, and so on. The approach is said to have been named after Julius Caesar, who used it to communicate with his officials.

To encrypt a given text, we require an integer value known as a shift that shows how far down each letter of the text has been shifted.
By initially converting the characters into integers, the encryption may be expressed using modular arithmetic.

According to the scheme, A = 0, B = 1,…, Z = 25. Encryption of a letter by a shift n can be described mathematically as.

E n(x)=(x+n)mod /26 (Encryption Phase with shift n)
D n(x)=(x-n)mod/26 (Decryption Phase with shift n)

Examples :
Text : ABCDEFGHIJKLMNOPQRSTUVWXYZ Shift: 23 Cipher: XYZABCDEFGHIJKLMNOPQRSTUVW Text : ATTACKATONCE Shift: 4 Cipher: EXXEGOEXSRGI


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