I changed my VPN today from a PPTP connection to OpenVPN. My VPN settings using Ubuntu 12.04 show: Authentication: CA Certificate (Ipredator.se.ca.crt). The Advanced / TLS Authentication tab shows: Use additional TLS authentication: Key File (Ipredator.se.ta.key). Can someone please explain, in simple terms, what the CA Certifcate and additional TLS authentication Key File mean and how they enhance my privacy and / or security. Thanks!