Which system binds a public key to an entity's identity and manages digital certificates?

• A. Hashing
• B. Encryption
• C. Certificates
• D. PKI

Answer: (D)

Trust in public-key cryptography is established by binding a public key to an entity’s identity and managing the digital certificates that prove that binding. A digital certificate is the credential that links a specific public key to a real-world identity, but you need a framework to issue, verify, renew, and revoke those certificates and to establish trust across systems. That framework is the Public Key Infrastructure. PKI includes the authority that signs certificates (the Certification Authority), processes that verify identities (Registration Authority), a repository of issued certificates, and mechanisms to revoke or validate certificates (like certificate revocation lists or OCSP). With PKI, others can trust that a given public key actually belongs to the claimed entity, enabling secure communications and digital signatures. Hashing, encryption, and certificates alone don’t provide the full lifecycle and trust framework that PKI supplies.