Caesar Cipher in Cryptography
A Caesar Cipher is one of the most simple and easily cracked encryption methods.
It is a Substitution Cipher that involves replacing each letter of the secret message with a different letter of the alphabet which is a fixed number of positions further in the alphabet.
For example with a shift of 1, A would be replaced by B, B would become C, and so on. The method is apparently named after Julius Caesar, who apparently used it to communicate with his officials.
Thus to cipher a given text we need an integer value, known as shift which indicates the number of position each letter of the text has been moved down.
Text : ABCDEFGHIJKLMNOPQRSTUVWXYZ
Shift: 23
Cipher: XYZABCDEFGHIJKLMNOPQRSTUVW
Text : ATTACKATONCE
Shift: 4
Cipher: EXXEGOEXSRGI
Algorithm for Caesar Cipher:
Input:
- A String of lower case letters, called Text.
- An Integer between 0-25 denoting the required shift.
Procedure:
- Traverse the given text one character at a time .
- For each character, transform the given character as per the rule, depending on whether we’re encrypting or decrypting the text.
- Return the new string generated.
How to decrypt?
We can either write another function decrypt similar to encrypt, that’ll apply the given shift in the opposite direction to decrypt the original text. However we can use the cyclic property of the cipher under modulo , hence we can simply observe
Cipher(n) = De-cipher(26-n)
Hence, we can use the same function to decrypt, instead we’ll modify the shift value such that shift = 26-shift
Caesar Cipher implementation in python
Caesar Cipher implementation in C language
Caesar Cipher implementation in Javascript
