You use a shared key I guess. I had a look how keybase does it [1] but they don't say in that blog post. But in their post about encyrpted group chat and chat

You use a shared key I guess. I had a look how keybase does it [1] but they don't say in that blog post. But in their post about encyrpted group chat and chat bots they do say there is a shred key for the group caht. [1] - https://keybase.io/blog/encrypted-git-for-everyone https://keybase.io/blog/encrypted-git-for-everyone