Which statement correctly describes the role of the CA's digital signature in a certificate?

• A. It confirms identity only
• B. It confirms the public key only
• C. It signs the entire certificate to verify issuer and integrity
• D. It is used to encrypt data

Answer: (C)

The digital signature on a certificate is created by the certificate authority to bind the certificate’s contents together and prove who issued it. When you receive a certificate, you verify its signature with the CA’s public key; if it checks out, you gain two assurances: the certificate was issued by that trusted CA, and the certificate’s data hasn’t been altered since issuance. Crucially, the signature covers the entire certificate, including the subject’s identity, the subject’s public key, validity period, and any extensions, so it guarantees both issuer authenticity and data integrity in one fell swoop. It’s not used to encrypt data, and it doesn’t merely confirm identity or merely confirm the public key by itself—the signature certifies the entire certificate and binds the key to the verified subject.