This post offers solutions for – VPN client does not work or is not connecting ... WAN Miniport (IP), WAN Miniport(IPv6) and WAN Miniport (PPTP) are used for VPN connections, i.e., connection ...
Then, the key is used to create the encryption needed for streaming data using the RC4 encryption scheme between the VPN clients. The asymmetric key used to negotiate PPTP sessions isn't secure.