The communications between the guests and the Guest Portal are encrypted, and the Guest Portal accepts only HTTPS (HTTP over SSL/TLS) connections.
The Guest Portal uses the default self-signed Guest Portal certificate generated by the Sensor. The Guest Portal uses this certificate to generate standard browser messages to the guest users. You can use a custom SSL certificate and eliminate the browser warning, if required.
Generating a self-signed certificate via Sensor CLI
The Sensor CLI provides guest-portal install command which prompts the user for different fields required for Guest Portal Certificate and for creating the public/private key pair.