What the server knows about you
Let's start with the basics. Solo2's server knows exactly three things about you: your username, your unique identifier, and a hash of your password. A hash is an irreversible mathematical transformation — the server can verify your password is correct without knowing what it is. Your real password only exists in your head and on your device.
And that's it. The server doesn't know who you talk to. It doesn't know how many tunnels you have. It doesn't know your contacts' names. That information only exists inside your vault, encrypted on your device. The server couldn't open it even if it wanted to.
The mailboxes
Imagine a wall of numbered mailboxes, like in an old post office. When your app wants to connect with someone, it leaves a note in a mailbox saying 'I want to talk to user X'. Nothing more. It doesn't say who you are. It doesn't say what you want to talk about. Just a note in a mailbox.
Periodically, all apps connected to Solo2 check the mailboxes to see if someone has left a note for them. It's like stopping by the post office and asking: 'Is there anything for me?'. If your contact finds your note, they ask the server for the IP address you left. The server provides it, and that information is erased from memory immediately. It's never written to any disk. It lives in the server's temporary memory for the milliseconds needed to respond.
From that point on, the server disappears
Once both devices know each other's address, they talk directly to each other. The server no longer participates. It doesn't relay messages. It doesn't store them. It doesn't know whether the connection was established or not. It doesn't know how long it lasts. It doesn't know how many messages are exchanged or how large they are.
So much so, that if the server shut down at that moment, the two users would continue talking exactly the same. The conversation doesn't depend on the server. It only depended on it for the two devices to find each other. Once connected, the server is irrelevant.
The conversation is secure before it even starts
When two people create a tunnel in Solo2, their devices exchange public cryptographic keys. From that moment, each message is encrypted with the recipient's key — and only the recipient can decrypt it. This happens before any conversation begins. The keys are ready from the moment the tunnel is created.
That's why, when the two devices connect directly, the communication is already protected. They don't need to negotiate anything. They don't need to ask the server for permission. The keys are theirs, on their devices, and nobody else has them.
What this means in practice
It means there's no record of your conversations on any server. No metadata to analyze. No history to hand over to a court order. No database to hack. Solo2's server can't hand over what it doesn't have. And it doesn't have anything because it never did.
Next time someone tells you an app 'encrypts your messages end-to-end', ask what happens with everything else. Who knows who you talk to. Who knows at what time. Who knows how often. If the answer is 'our server, but we don't use it for anything bad' — that's a promise. In Solo2, the answer is different: nobody knows. Because there's nobody to ask.