If you get a (free) SSL certificate and key from StartSSL it might not be obvious how to install use them properly in nginx. nginx doesn’t automatically chain certificates like f.e. Apache does so you’ll have to do that yourself.
First, use the StartSSL website to create an SSL key and certificate and transfer them to your server. Then execute the following steps (if you use a class 2 certificate replace class1 by class2 in the instructions below):
Decrypt the private key using the password you entered when you created your key:
openssl rsa -in ssl.key -out /etc/nginx/conf/ssl.key
Protect your key from prying eyes:
chmod 600 /etc/nginx/conf/ssl.key
Fetch StartSSL’s root CA and class 1 intermediate server CA certificates:
Create a unified certificate from your certificate and the CA certificates:
cat ssl.crt sub.class1.server.ca.pem ca.pem > /etc/nginx/conf/ssl-unified.crt
Configure your nginx server to use the new key and certificate (in the global settings or a
Tell nginx to reload its configuration:
killall -HUP nginx
And you’re done!