Who issues certificates?

• A. Public Key Registry
• B. Certification Scientist Board
• C. Public Auditor
• D. Certificate Authority (CA)

Answer: (D)

Digital certificates are issued by a certificate authority, a trusted entity in a public key infrastructure. The CA verifies the identity of the party requesting a certificate and then issues a digital certificate that binds that identity to a specific public key. The certificate is digitally signed with the CA’s private key, allowing anyone who trusts the CA to verify the certificate with the CA’s public key. This chain of trust lets others be confident that the public key really belongs to the claimed entity, which is essential for secure communications like TLS/SSL. Other options don’t fit because they’re not standard issuing authorities in PKI: a public key registry is typically just a directory, not an issuer; a public auditor isn’t involved in certificate issuance; and a Certification Scientist Board isn’t a recognized authority for issuing certificates.