About Nullcode

Nullcode is a free, browser-based message encryption tool built for people who care about privacy. Write a message, choose a cipher, set a secret key — and your text becomes unreadable to anyone who doesn't have the key. The recipient decodes it here, with the same cipher and the same key.

How it works

All encryption happens in your browser using JavaScript. Nothing is ever uploaded, stored, or transmitted to a server. We do not have accounts, do not log usage, and do not track who encodes what. When you close the tab, your message is gone.

The ciphers we use

Vigenère cipher — A polyalphabetic substitution cipher invented in the 16th century. It uses a repeating keyword to shift each letter of the message by a different amount, making it dramatically harder to crack than a simple Caesar shift. Free forever.

Polybius square — An ancient Greek cipher that maps each letter to a pair of coordinates on a 5×5 grid built from your keyword. Output looks like streams of numbers — completely opaque without the key.

Custom substitution — Builds a fully scrambled alphabet from your keyword. Every letter maps to a different one, and the mapping changes with every key you choose.

Who it's for

Journalists protecting sources, friends sharing private notes, security students learning how classical cryptography works, anyone who wants their words to stay between sender and recipient. Nullcode is not a replacement for end-to-end encrypted messengers like Signal for high-threat use cases — it is a lightweight, no-friction tool for adding a real layer of privacy to ordinary channels.

Pricing

The Vigenère cipher is free forever. Polybius and Substitution ciphers unlock with a one-time payment of €2.99. No subscription, no renewals.

Contact

Questions or feedback? See the contact page.