Text-Encryption-and-Decryption

This code is a simple implementation of Caesar Cipher, a basic encryption technique where each letter in the message is shifted by a certain number of positions (defined by the key) in the alphabet. The process is reversible by shifting in the opposite direction to decrypt the message.

Code Overview

1. Encryption (encrypt(message, key)):

   • The function takes two inputs: "message" (the plain text to encrypt) and "key"(the number of positions to shift the letters).
   • It loops through each character of the message. If the character is a letter:
     • It checks if it's lowercase or uppercase.
     • For lowercase letters, it shifts within the lowercase range ('a' to 'z`), and for uppercase, it shifts within the uppercase range ('A' to 'Z').
     • Non-alphabetic characters are left unchanged.
   • The encrypted message is returned.

   Key point: Shifting is done using the ASCII values (ord()) of characters and then converting them back using chr(). The shift is controlled by the key, and % 26 ensures that the shift wraps around the alphabet.

2. Decryption (decrypt(encrypted_message, key)):

   • The decryption process mirrors encryption but shifts letters backward (by subtracting the key).
   • Like encryption, it handles both lowercase and uppercase letters, and non-alphabetic characters are returned unchanged.
   • After looping through each character and reversing the shift, the original message is restored.

3. Main Function (main()):

   • This is the entry point of the program where:
     • The user is prompted to enter a message and a key (0-25).
     • The message is passed to the encrypt() function to get the encrypted message.
     • The encrypted message is then passed to the decrypt() function to retrieve the original message.
   • The encrypted and decrypted messages are displayed.

Example:

• If you input "Hello World" with a key of 3, the encryption will shift each letter by 3 positions:
  • "H" becomes "K", "e" becomes "h", etc.
  • The encrypted message might be "Khoor Zruog".
• Decrypting it with the same key shifts the letters back, restoring the original message: "Hello World".