“Let’s Encrypt is a new certificate authority (CA) offering free and automated SSL/TLS certificates. Certificates issued by Let’s Encrypt are trusted by most browsers in production today, including Internet Explorer on Windows Vista. Simply download and run the Let’s Encrypt client to generate a certificate (there are a few more steps than that, of course, though not many).
Before issuing a certificate, Let’s Encrypt validates ownership of your domain. First, The Let’s Encrypt client running on your host creates a temporary file (a token) with the required information in it. The Let’s Encrypt validation server makes an HTTP request to retrieve the file and validates the token, which serves to verify that the DNS record for your domain resolves to the server running the Let’s Encrypt client.
The Let’s Encrypt client does not yet officially support NGINX and NGINX Plus (support is in beta), but you can still get started right away using Let’s Encrypt with NGINX and NGINX Plus. (This blog applies to both NGINX and NGINX Plus, but for ease of reading we’ll refer only to NGINX Plus from now on.) All you need is the webroot plug-in from Let’s Encrypt, and a few small changes to your NGINX Plus configuration…”