At the time of this writing, LetsEncrypt is in public beta and already in high demand. This service is a new certificate authority that allows you to generate your own signed certificates in an effort to improve security. At present there is a feature request for providing this functionality in cPanel.
You can also use this handy (commercial) plugin: https://letsencrypt-for-cpanel.com/
Update: Sources for an open-source plugin have been released here:
I’m not going to go through the process of copying and pasting verbatim instructions, but you can find the entire write-up on the cPanel forums here: