Question

A security analyst is reviewing why a user's browser displayed a warning that a website's certificate was 'no longer valid' even though the certificate's notAfter date is six months in the future. Server logs confirm the certificate had not expired. Which mechanism most likely triggered this warning?

Accepted Answer

The certificate was revoked by the issuing CA and the browser confirmed its status via OCSP or a CRL

Answer

The browser rejected the certificate because it used symmetric encryption instead of asymmetric

Answer

The certificate's private key was transmitted across the network during the TLS handshake

Answer

The website used a self-signed certificate that had not been added to the trusted root store