What are CA Certificates used for

Question

I have a Linux debian server running Webmin. I have just installed SSL keys for my server, but I do not know if everything is correct.

In webmin I went to

webmin > Webmin Configuration > SSL Encryption > Upload certificate

There are 2 fields, one for a private key file, and one for a certificate. So I filed in the 2 texts in the fields, one for the private key, and one for the certificate. Then I hot save and everything worked fine.

Now I see that my SSL provider also has root CA, PEM and DER encoded. I also see intermediate server CA.

I was wondering if I should use these, and where exactly.

Answer 1

You would use the CA certificate if you want to automatically trust any certificates it has signed. This usually applies to clients like your web browser.

Servers use the CA certificate for two purposes.

• They will include the CA certificate if they are providing the full certificate chain. For this purpose the CA certificate may be included in the servers certificate file.
• They will use the CA certificate when deciding whether or not to trust a client's certificate. Client's usually don't have certificates, so this is rarely required. PKI implementations will use this method.