Vigenère Cipher
Encrypts and decrypts with the Vigenère cipher, which uses a repeating keyword to shift each letter by a different amount — the polyalphabetic cipher that resisted cryptanalysis for three centuries and earned the name "le chiffre indéchiffrable".
Runs 100% in your browser — keys and data never leave your device.
Read the full guide to this tool
Notes
- Vigenère defeats simple frequency analysis because the same plaintext letter maps to different ciphertext letters depending on its position under the key.
- It is broken by first finding the key length (Kasiski examination or the index of coincidence), then solving each column as a Caesar cipher.
- Runs 100% in your browser — keys and data never leave your device.
Explore the idea
Related tools
Enigma Machine Simulator
Operate a full Enigma I — rotors, plugboard, lamp board — and watch each letter travel the wiring.
Caesar Cipher & ROT
Shift-cipher encode/decode with an automatic brute-forcer.
Morse Code Translator
Text to Morse and back, with audio playback.
Substitution, Atbash & Affine
Monoalphabetic substitution ciphers with a custom key.
AES Encryption
Encrypt and decrypt text with AES-GCM or AES-CBC.
Cryptographic Key Generator
Random keys, IVs, salts and API tokens from a CSPRNG.