Vigenère Cipher Calculator
Encode or decode text using a Vigenère cipher, which shifts each letter by an amount determined by a repeating keyword.
About the Vigenère Cipher Calculator
The Vigenère cipher strengthens the simple Caesar cipher by using a different shift for each letter, determined by a repeating keyword instead of one fixed shift for the whole message. This made it far harder to crack with basic frequency analysis, earning it the nickname "le chiffre indéchiffrable" for centuries.
How it works: Each letter of the keyword (cycled repeatedly to match the message length) sets the shift amount for the corresponding letter of the message, using the same A=0, B=1... Z=25 shift logic as a Caesar cipher.
Non-letter characters pass through unchanged and don't consume a keyword letter. Like the Caesar cipher, this is a classic historical/educational cipher and is not considered secure for protecting real sensitive data by modern standards.