What the hub does
- Looks up a Stonechat ID and answers with that person’s public key and mailbox address
- Sets up a hosted mailbox when you ask for one
Your messages.
Your server.
Stonechat is an end-to-end encrypted private messaging app where you own the server. Every person has their own mailbox: contacts send messages to it, and your phone picks them up. You can destroy and recreate your mailbox at will.
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This is the whole thing
01 · Lookup
Alice adds Bob by his Stonechat ID. Her phone asks the hub where that ID lives.
02 · Answer
The hub replies with Bob's public key and his mailbox address. Alice checks it against the ID she asked for.
03 · Send
Alice's phone seals the message for Bob and delivers it directly to his mailbox. The hub never sees it.
04 · Retrieve
Bob's phone fetches the envelope, decrypts it, and acks. The mailbox deletes it.
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Your identity
No phone number, no email, no password. Your identity is a secret key that the app creates on your phone, and it never leaves it. From this key comes your Stonechat ID, something like SC-XXXX…. This ID is what you share so contacts can add you, as a QR code or as plain text.
Technical explanation?
Your identity is an Ed25519 key pair, generated on your phone and never uploaded. The Stonechat ID is a hash commitment to the public key (BLAKE2b-160 plus a checksum, written in base32).
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Your mailbox
A mailbox is a tiny private post box that belongs to one person: you. Instead of one giant server holding everyone’s messages, each person has their own small mailbox. People drop locked envelopes in it. The mailbox can’t read them or even tell who sent them, and once your phone has picked them up, they are deleted. You choose who runs it: we can host it for you, a friend can, or you can run it yourself.
Technical explanation?
The mailbox is a tiny Rust binary that works as a relay. We run it in a Docker container on a VPS; you can run the binary wherever you want. It’s fast to spin up and destroy, which makes it easy to tear down and recreate if you want a fresh mailbox.
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The hub
The hub is the only central server in Stonechat. It tells your app where someone’s mailbox is, so you can message them. It never carries or sees your messages.
What the hub never does
- Read, store or relay a message
- Hold your secret key or your contacts
- Know who is talking to whom
Technical explanation?
The hub is a small Python (FastAPI) service. It is a directory that maps a Stonechat ID to a public key and a mailbox address, and it can provision hosted mailboxes. When you add a contact, the app asks the hub for the contact’s public key and mailbox IP address to know where to send messages. You can run your own hub, but it will be a network separate from the main Stonechat network.
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The app
Owning your mailbox doesn’t mean giving up the things that make a messenger nice to use. Stonechat is a modern chat app with the features you’d expect from a, well, modern chat app.
MESSAGES
Replies, emoji reactions, stickers. Edit a message, or delete it for everyone.
MEDIA
Photos, video & voice notes. Files are encrypted before they leave your phone.
CALLS
Voice & video calls. Encrypted end-to-end.
GROUP CHATS
Small groups of up to 25 people. End-to-end encrypted.
MULTI-DEVICE
Link a second phone or the web app to the same identity, and keep an encrypted backup you control.
ENCRYPTION
Modern, post-quantum crypto. Signal-style double ratchet with a post-quantum key exchange on top. Every message gets a fresh key.
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Self-host
Everything on the server side is open source and free to run yourself.
JUST YOU
Your own mailbox
Run a mailbox on a small always-on Linux machine — a cheap cloud server or a box at home. You still talk to everyone on Stonechat.
YOUR FAMILY, FRIENDS, OR TEAM
Your own mailbox host
One machine can host mailboxes for the people you invite. Their messages are encrypted even from you. Just give them the IP address and an invite code.
YOUR NETWORK
Your own hub
Run the whole hub on your own server and get a private Stonechat network. You can still use the same mobile app; just point it at your hub.
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Who is behind this
I’m just a software engineer who got tired of the sketchy messaging apps that are okay with opening backdoors to your messages for other “entities”, or are considering allowing the scanning of ALL your messages for some shady reasons. So I built Stonechat. I hope it’s useful to someone.
If you want to help me or have some suggestions, email me at julio [at] stonechat.app, find me on X at @julioandresdev, or on LinkedIn.
Get Stonechat
Stonechat is invite-only for now, and the iPhone and Android apps are coming soon to the stores. Request an invite by email. Self-hosting doesn’t need an invite code.
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Open source
All of Stonechat — the app, the mailbox and the hub — is open source under the AGPL-3.0 license.