I don't see any mention of encryption in this standard. Are all messages public? I'd like to see this using public and private keys so that it is guaranteed onl

I don't see any mention of encryption in this standard. Are all messages public? I'd like to see this using public and private keys so that it is guaranteed only intended recipients (e.g. people on my friends list) can read my messages. This is especially important given the federated nature of this.