Privacy and encryption
What end-to-end encryption means here
Section titled “What end-to-end encryption means here”Your messages, attachments and calls are encrypted on your device and decrypted on the devices of the people you talk to. The keys never leave your devices, and the node in between only stores and forwards encrypted data: its operator cannot read along, and neither can anyone who breaks into it.
Channels are encrypted unless a room admin decides otherwise; direct messages, groups and voice always are.
What the node can see
Section titled “What the node can see”To deliver messages, a node needs some information about them. Its operator can see:
- who is a member of which room and conversation, and who writes when;
- whom a message mentions, so that the node can notify them;
- the size of files and messages;
- your profile, your status and the address you connect from.
When you send a link with a preview, your home node loads the linked page to build the preview, so it sees that link. The node never sees the text of encrypted messages, the names or contents of encrypted files, or your keys.
Channels without encryption
Section titled “Channels without encryption”A room admin can turn encryption off for a text, announcement or forum channel, for example for a large public channel. Such a channel shows a permanent banner that says the operator of the node can read along, and the change is recorded in the room’s audit log. Files channels without encryption say so in the same way.
Your history on new devices
Section titled “Your history on new devices”Your devices back up the keys of your conversations to your home node, encrypted so that only your recovery key or a passkey can open them. That is how a new device can read your older messages after you unlock it. For a single conversation you can also choose Keep the full history on this device in its menu.
Members who join a channel later read as much of its history as the channel allows; room admins set this per channel.
“Security key changed”
Section titled ““Security key changed””Every person has a security key that vouches for their devices. When someone’s key changes, you see a notice next to their name. Usually they reset their account, for example after losing their recovery key. If you verified them before, compare the safety number again; see Friends and direct messages.
Unknown devices (“ghost members”)
Section titled “Unknown devices (“ghost members”)”tavrn checks every device in a conversation against its owner’s security key. If a device shows up that its owner has not confirmed, the app warns you and sends nothing until you have looked at it. Often it is just someone’s new device, but it could be an attempt to listen in: when in doubt, ask the person.
One honest limit
Section titled “One honest limit”The web app is code that your node sends to your browser. A malicious operator could send a modified app. Using the web app of a node you trust, or the desktop app, narrows this. tavrn’s encryption code has not been audited by an independent firm yet.