Uyuni uses SSL certificates to ensure that clients are registered to the correct server.
When you create an SSL certificate for your server, the certificate includes the host name of the server it is associated with. The certificate is then deployed on the server, and when clients attempt to connect, they check the certificate details. If the certificate contains the name of the server they are attempting to connect to, the connection will be successful. The client will also check if the certificate has been signed by a trusted certificate authority.
All certificates must be signed by a certificate authority (CA), in order for them to be considered valid, and for clients to be able to successfully match against them. When an organization signs its own certificate, the certificate is considered self-signed. A self-signed certificate is straight-forward to set up, and does not cost any money, but they are considered less secure.
For additional security, you can arrange a third party CA to sign your certificates. Third party CAs perform checks to ensure that the information contained in the certificate is correct. They will usually charge an annual fee for this service. Using a third party CA makes certificates harder to spoof, and will provide additional protection for your installation.
By default, Uyuni uses a self-signed certificate. If you have certificates signed by a third party CA, you can import them to your Uyuni installation.