Vigenère Cipher Encoder/Decoder

About this calculator

This tool encrypts or decrypts text with the Vigenère cipher, a polyalphabetic substitution cipher that shifts each letter of the plaintext by an amount determined by the corresponding letter of a repeating keyword, using what's known historically as the tabula recta. Because the shift changes from letter to letter, it defeats simple frequency analysis that breaks single-shift ciphers like Caesar's.

Used for centuries as a "le chiffre indéchiffrable," it's now mainly a teaching tool for cryptography students, puzzle and CTF (capture-the-flag) enthusiasts, and hobbyists exploring classical ciphers. Enter your text and a keyword, choose encrypt or decrypt, and get the result instantly.