Security
Vigenère Cipher
Encrypt and decrypt text using the Vigenère cipher with a keyword.
The key is repeated to match the text length. Only letters are used.
The Vigenère cipher uses a keyword to shift letters by different amounts, making it much stronger than Caesar cipher.
Example: Text "HELLO" with key "KEY" → H+K, E+E, L+Y, L+K, O+E
Documentation
How to Use
1
Switch Mode
Choose Encrypt or Decrypt.
2
Enter Text
Type or paste the message you want to encrypt or decrypt.
3
Provide Keyword
Enter a secret keyword (letters only).
4
Generate Key
Click Generate Key for a random 16-character keyword.
5
Process
Click to encrypt/decrypt or 'Show Work' to see step-by-step.
Pro Tips
Longer keywords are more secure
Use Show Work to see letter transformations
Examples
Input
Message: HELLO, Key: KEY
Output
RIJVS