What is the primary function of a digital certificate in PKI?

• A. Digital certificates encrypt all data
• B. Digital certificates act like firewalls
• C. Digital certificates bind a public key to an identity
• D. Digital certificates store passwords

Answer: (C)

A digital certificate in PKI mainly binds a public key to an identity. It’s a digitally signed statement issued by a trusted Certificate Authority that says this public key belongs to this person or entity, along with the subject’s identifying information, the issuer, and the certificate’s validity period. The certificate also contains the CA’s signature, which you can verify with the CA’s root key to establish trust.

Why this is the right function: with the certificate, others can confidently associate a public key with a known identity. This enables secure key exchange and authentication: you can encrypt to the recipient’s public key or verify a sender’s signed message, knowing the key actually belongs to the claimed subject because the CA’s trusted signature vouches for the binding.

The other options don’t fit because the certificate itself does not encrypt all data, it does not act as a firewall, and it does not store passwords. While the public key in a certificate can be used for encryption, the certificate’s purpose is the verified link between the key and the identity, not bulk data encryption or credential storage.