Autokey Cipher
Encrypt and decrypt the Vigenère autokey cipher — runs 100% in your browser. No data is uploaded; nothing leaves your device.
Reach for Autokey Cipher whenever you need to encrypt and decrypt the Vigenère autokey cipher. It is a favourite for CTF challenges, escape-room puzzles, geocaching clues and classroom cryptography lessons — decode mystery messages or teach how historical encryption worked, with zero setup.
How to embed Autokey Cipher on your website
Add this free tool to your own site, blog or intranet — it's 100% free to embed. Paste this snippet where you want the tool to appear; it loads a clean, self-contained version with no ads or navigation.
<iframe src="https://tooljolt.com/embed/autokey-cipher" title="Autokey Cipher" width="100%" height="640" style="border:1px solid #e5e7eb;border-radius:12px" loading="lazy"></iframe>
About Autokey Cipher
Autokey Cipher is a free online classic cipher tool that lets you encrypt and decrypt the Vigenère autokey cipher. It runs entirely in your browser — no sign-up, no uploads and nothing ever sent to a server — so it is fast, private and safe to use with sensitive data. Whether you are a developer, security professional, student or just curious, Autokey Cipher gives you an instant, reliable result with zero setup.
How to use Autokey Cipher
- 1Type or paste your message into Autokey Cipher.
- 2Enter the key or settings the cipher needs.
- 3Switch between encrypt and decrypt as needed.
- 4Copy the transformed text to share or solve your puzzle.
Why use Autokey Cipher?
- ✓100% free with no sign-up, accounts, watermarks or usage limits
- ✓Runs entirely in your browser — your input never leaves your device, ideal for confidential security data
- ✓Perfect for CTF challenges, escape rooms, puzzles and cryptography lessons
- ✓Encode and decode in both directions instantly
- ✓Works on any device with a modern web browser, online or offline
Frequently asked questions
Is the cipher in Autokey Cipher secure for real data?+
No. Classic ciphers like this are trivially broken by modern computers and exist for puzzles, CTF challenges, escape rooms and learning how cryptography evolved. For real protection, use AES or another modern algorithm.
Can Autokey Cipher both encode and decode?+
Yes. Autokey Cipher works in both directions, so you can encrypt a message and decrypt it again, or solve a coded message you were given.
Is Autokey Cipher free to use?+
Yes. Autokey Cipher is 100% free with no sign-up, no account, no usage limits and no watermarks. Use it as often as you like.
Does Autokey Cipher upload my data to a server?+
No. Autokey Cipher runs entirely in your browser using JavaScript — nothing you type or upload ever leaves your device. That makes it safe to use with sensitive or confidential security data.
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