This Cute Chat Site Could Save Your Life And Help Overthrow Your Government (Wired)

That deals with code signing only. I kept looking for public keys to transfer over a secure channel, but it seemed anyone could just join the chat. It was not until I read this comment thread that I found out how to get fingerprints using the UI.

It does however tell you how many are reading. If there are supposed to be three clients connected, but four subscribe, you know the chat room to be compromised. And in the case of small and tightly-knit groups that may be enough.

But then you have to securely verify that everyone is subscribed before you send anything sensitive, because otherwise that third subscriber could just as well be the military or the police.