Caesar Cipher

Module 01 / Lesson 01

Visual Explanation

Theoretical Concept

The Caesar Cipher is a type of Substitution Cipher. It works by shifting each character of the message by a fixed number of positions (called the 'Key') in the alphabet.

Mathematical Rule:

                    Encryption: E(x) = (x + k) mod 26 

                    Decryption: D(x) = (x - k) mod 26

For example, with a shift of 3, 'A' becomes 'D'. Despite its historical significance, it is very easy to break using brute force or frequency analysis.

Python Implementation

def caesar_cipher(text, shift, mode='encrypt'):
    result = ""
    if mode == 'decrypt':
        shift = -shift
    
    for char in text:
        if char.isalpha():
            start = ord('A') if char.isupper() else ord('a')
            new_char = chr((ord(char) - start + shift) % 26 + start)
            result += new_char
        else:
            result += char
    return result

# Usage
msg = "CipherBoy"
encrypted = caesar_cipher(msg, 3, 'encrypt')
print(f"Encrypted: {encrypted}")

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