This is a service that let's you get SSL certificates for HTTPS. These certificates are trusted by major browsers. See Let's Encrypt This is a barebones howto to get SSL certificates:
git clone https://github.com/letsencrypt/letsencrypt cd letsencrypt
This contains the client software for let's encrypt.
./letsencrypt-auto certonly --manual
This will start by updating and getting any needed dependencies and then jump to a wizard like configuration to get this done. Follow the prompts and pay special attention on the prompt used to validate your domain. (You need to create a couple of folders and a file with the right content). Afterwards your certificates will be in:
Then go to your CPanel configuration, then upload:
privkey.pemto Private Keys
Then you go to Manage SSL Hosts -> Browse Certificates, pick the right certificate. Then paste
chain.pem (from /etc/letsencrypt/live/mydomain.tld) to the CA Bundle box.