In order to validate a certificate presented to you, what would you need?

To validate a certificate presented to you, you would need a Certificate Authority (CA) certificate. The CA is a trusted entity that issues digital certificates, which are used to verify the ownership of public keys. When a certificate is presented, the validation process involves checking its signature against the trusted CA certificate.

The CA certificate contains the public key of the CA, allowing you to confirm that the signature on the presented certificate matches the public key of the CA. If the signatures match, it indicates that the presented certificate was indeed issued by a trusted CA, thus validating its authenticity.

Other options do not serve the purpose of validating a certificate in the same way. A root certificate, while related, usually refers to the highest level of CA certificates in a hierarchy and is often included within a CA certificate's validation process. A firewall certificate is specific to firewall devices and does not play a role in the general validation of digital certificates. A user certificate is an individual certificate that may also need validation, but it relies on a CA certificate for trustworthiness and verification.