https://security.stackexchange.com/questions/220068/using-local-port-forwarding-from-raspberrypi-to-vps-in-order-to-be-able-to-acces ssh - Using local port forwarding from RaspberryPI to VPS in order to be able to access the PI from anywhere on the Internet, security considerations? - Information Security Stack Exchange
https://gist.github.com/attacus/cb5c8a53380ca755b10a5b37a636a0b9 Create your own encrypted chat server with Riot and Matrix