To ensure that a digital certificate is valid, the receiver must check ________.

• A. the digital signature
• B. the valid period
• C. whether the certificate has been revoked
• D. All of the above

Answer: (D)

Verifying a digital certificate requires multiple checks to establish trust. The digital signature confirms the certificate came from the claimed issuer and hasn’t been tampered with. The valid period ensures the certificate is currently active, not expired or not yet valid. The revocation status checks whether the certificate has been withdrawn due to compromise or policy reasons. Because each of these conditions protects a different aspect of trust, you need to perform all of them to ensure the certificate is truly valid.