Mine
public text v1 · immutableroot@OpenWrt:~# uci set dropbear.cfg1.PasswordAuth=off
root@OpenWrt:~# uci commit
root@OpenWrt:~# /etc/init.d/dropbear restart
Connection to router closed by remote host.
Connection to router closed.
plouj@gray ~ $ ssh root@router
ssh: connect to host router port 22: Connection refused