It is suggested that you only run Foundation API Server over SSL and use nginx as a proxy for performance reasons. This gist demonstrates how to configure nginx and create a certificate for use in development. In production, it is suggested you use a certificate from your preferred certificate authority.
Create a directory called 'ssl' under the nginx configuration directory to hold the certificates:
sudo mkdir /etc/nginx/ssl
Now that we have a location to place our files, we can create the SSL key and certificate files in one motion by typing:
sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/nginx/ssl/nginx.key -out /etc/nginx/ssl/nginx.crt