Classical Cipher App
Instantly encrypt and decrypt messages with 15 classical ciphers — Caesar, Vigenère, Playfair, Hill, Enigma and more. Pick a cipher, type in either panel, and watch the transformation update live.
Current shift: 3
How it works
Pick a cipher from the dropdown, then type in either the plaintext or ciphertext panel — the other panel updates instantly using the algorithm and key/rotation you set. Everything runs locally in your browser, so nothing you type ever leaves your device.
Frequently asked questions
- What is a classical cipher?
- A classical cipher is a pre-computer method of encrypting text, such as shifting letters (Caesar), substituting them with a keyword (Vigenère), or rearranging them (Rail Fence). They're taught for their historical and educational value.
- Are these ciphers safe for real secrets today?
- No. Every cipher here except the One-Time Pad can be broken with modern computers, often instantly. Use them for puzzles, learning cryptography, or historical curiosity — not for protecting sensitive information.
- Is my text sent to a server?
- No. All encryption and decryption runs in your browser with JavaScript — nothing you type is ever sent over the network.
- Which cipher should I use to decode a message I received?
- Pick the cipher named or implied by the puzzle, then paste the message into the ciphertext panel. If you don't know which cipher was used, Caesar and Vigenère are the most common starting points.
- Can I customize the key or rotation offset?
- Yes. Selecting a cipher reveals its parameters — a rotation offset for Caesar, a keyword for Vigenère or Playfair, a matrix for Hill, and so on — and the output updates live as you change them.