Vigenère Cipher Calculator

This comprehensive tool allows you to both encrypt and decrypt messages using the classic Vigenère cipher algorithm. Choose your operation below:

Encryption

Convert plain text into secure ciphertext using a secret key

Decryption

Decode ciphertext back to original message with the correct key

Secure Algorithm

Uses the polyalphabetic Vigenère cipher for strong encryption

About the Vigenère Cipher

The Vigenère cipher is a method of encrypting alphabetic text by using a simple form of polyalphabetic substitution. It was invented by Blaise de Vigenère in the 16th century and was considered secure for centuries until the development of frequency analysis techniques.

How It Works

The cipher uses a keyword to shift letters in the plaintext:

Encryption: Each plaintext letter is shifted forward in the alphabet by the amount of the corresponding keyword letter (A=0, B=1, etc.)
Decryption: Each ciphertext letter is shifted backward by the keyword letter value
The keyword is repeated to match the length of the message

Security Considerations

For maximum security:

Use a key that is as long as the message
Avoid common words or phrases as keys
Never reuse the same key for multiple messages
Share keys through secure channels only