It doesn’t work like a centralized server for connecting contacts. You use a unique link per device to initiate the original connection with others at a distance or you can use QR codes in-person.

The link just tells briar where to route the messages and looks like:

briar://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (50 char alphanumeric key)

So there’s no way to impersonate someone directly. If you made two contacts and they use the same username, I suppose you could mistake them, but their contact connection keys will not be the same.

Hopefully that makes sense, if you look in the app or their site, it’s probably explained clearer.

Probably Briar. Encrypted, P2P, and doesn’t require anything but a username and password to sign up. Pretty sure that username doesn’t need to be unique, it’s just what people will see you as in messages.

Downside is it’s only Android, so many people are left out.

Unfortunately, this is a barbell of silence. Privacy won’t hold up to our expectations unless it is cone shaped.