The difference between a signed certificate and a self-signed certificate mainly reside in the fact the signed certificate has been delivered by a trusted source that identified you as the legitimate domain owner.
So why would someone use a self-signed certificate?
The main reason people use a self-signed SSL certificate is because it's free. Self-signed certificates are great for testing purposes or to secure a portion of your website that is to be accessed only by you or your staff. It's also useful for intranet websites where there is probably no need to verify the domain owner.
When you access a website secured by a self-signed certificate, you will see a warning message similar to this:
How to Generate a Self-Signed Certificate
In order to generate a self-signed certificate on a cPanel server, log in to your WHM control panel as root and click on Generate an SSL Certificate and Signing Request from the main menu. Simply fill-in the details and use all the default settings.
Note that it is not necessary to have the certificate and signing request (CSR) sent to you by email as they will be stored on the server.
How to Install a Self-Signed Certificate
Before you can install any type of SSL certificate (trusted or self-signed), your domain (or sub-domain) needs to have its own dedicated IP address.
To assign a dedicated IP address to a whole domain, go to WHM > Change Site's IP Address. Don't forget to reserve the IP address once you're done. This will avoid it from being assigned to another domain.
Once you're ready to install the certificate, go to WHM > Install an SSL Certificate on a Domain. Click on Browse Certificates to select the newly generated certificate:
WHM will automatically insert the certificate and private key in the appropriate fields. Simply hit Install. If everything went well, you will get this message:
Now try accessing your website using HTTPS and see if the connexion is secured. If you want to force HTTPS access, see the last step from this post.
Removing an SSL Certificate
To uninstall an SSL certificate, go to WHM > SSL Storage Manager. You will need to delete the key, the certificate and the certificate signing request.
If you've forced HTTPS connexion through an .htaccess file, make sure the remove the instructions.