Built a small encrypted messenger that runs over any MQTT broker you host. The broker is just a dumb relay — it only sees ciphertext, never plaintext.
Setup is dead simple: spin up an MQTT broker (EMQX, Mosquitto, whatever), share a room name and encryption key with someone, done. ChaCha20-Poly1305 + Argon2id, fresh salt and nonce per message. Rust backend (Tauri), React frontend, single portable exe around 5MB.
There's also a clipboard encryption mode — type plaintext, it encrypts to clipboard, paste into any app. Useful if you don't want to run a dedicated chat client.
Originally designed for people in censored regions, but it works as a minimal self-hosted secure chat for anyone who wants it.
Limitations: no forward secrecy, no traffic obfuscation, Windows only for now. Tauri should make cross-compilation straightforward if anyone wants to build for Linux/macOS.
Unlicense, public domain. I'm not maintaining it — fork and do what you want.
Due to throwaway account limitations, I can't post this in many places. If you think this project is useful, feel free to share it wherever you think it fits.