Vigenere Cipher
Securely encrypt and decrypt messages using a keyword. Polyalphabetic substitution made easy.
Polyalphabetic
Uses multiple substitution alphabets based on your key for stronger security than Caesar cipher.
Client-Side
Your secret keys and messages never leave your browser. 100% private.
Real-Time
See the encryption/decryption results instantly as you type your message or key.
Try These Examples
Classic Encryption
Encrypt a simple message with key KEY. See how the Vigenere cipher transforms each letter.
Secret Meeting
Encrypt a meeting time and location with a passphrase for secure communication.
Decrypt Challenge
Try decrypting this message with key KEY. The secret word is HELLO.
Long Message
Test the cipher with a longer paragraph using a strong key.
About Vigenere Cipher
The Vigenere cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword. It employs a form of polyalphabetic substitution.
First described by Giovan Battista Bellaso in 1553, the cipher is easy to understand and implement, but it resisted all attempts to break it for three centuries, which earned it the description le chiffre indechiffrable (the indecipherable cipher).
How it Works
To encrypt, a table of alphabets can be used, termed a tabula recta, Vigenere square or Vigenere table. It has the alphabet written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous row, corresponding to the 26 possible Caesar ciphers.
At different points in the encryption process, the cipher uses a different alphabet from one of the rows. The alphabet used at each point depends on a repeating keyword.