The Caesar Cipher is a straightforward and historical encryption technique that falls under the category of symmetric ciphers. Named after Julius Caesar, who is believed to have used it for military communications, the cipher involves shifting each letter in the plaintext by a fixed number of positions down the alphabet.

Algorithm description

Key

The Caesar cipher uses a fixed shift value to encrypt and decrypt messages. The key represents the number of positions each letter of the plaintext is shifted in the alphabet.

Work Principles

1. Encryption:
   • For each letter in the plaintext, shift it forward in the alphabet by the fixed key;
   • Wrap around to the beginning of the alphabet if the shift goes beyond 'Z' (for uppercase) or 'z' (for lowercase);
   • Non-alphabetic characters remain unchanged.
2. Decryption:
   • To decrypt, shift each letter in the ciphertext backward in the alphabet by the fixed key;
   • Wrap around to the end of the alphabet if the shift goes before 'A' (for uppercase) or 'a' (for lowercase);
   • Non-alphabetic characters remain unchanged.

Example

Let's encode word Hello using Caesar Cipher with key = 2.

Note

The Caesar cipher is a straightforward and easily breakable encryption method. It is a historical example rather than a secure choice for modern cryptography. Its simplicity makes it a useful educational tool for understanding basic encryption principles.

You can try to use Caesar Cipher using this simple web interface: