Several of your organization's users have requested permission to install certificates from a third party. Before users can install these certificates, company policy states that you must verify that the certificates are still valid. You need to check for revocation. What could you check to verify this information? (Choose all that apply.)

A. CRL
B. OCSP
C. DNSSEC
D. DRM

A,B
Explanation: You can use either a certificate revocation list (CRL) or Online Certificate Status Protocol (OCSP) to check for certificate revocation, depending on which type of PKI is deployed.
DNSSEC is a security feature used by Domain Name System (DNS). Digital rights management (DRM) controls the use of digital content and devices after sale.