What is the primary purpose of a digital certificate in public key infrastructure?

• A. Binds a public key to a subject and is issued by a trusted authority.
• B. Stores the private key.
• C. Encrypts emails.
• D. Is a password file.

Answer: (A)

Digital certificates in PKI exist to bind a public key to the identity of a subject and to establish trust through a trusted issuer. The certificate includes the subject’s identity, the public key, the issuer’s identity, a validity period, and a digital signature from the issuer. Anyone can verify that signature using the issuer’s public key, confirming that the public key really belongs to the stated subject. This enables authentication and secure communication since others can trust that they’re using the correct key for that identity. The private key stays with the owner and is not stored in the certificate. The certificate’s purpose isn’t to encrypt emails itself; it provides the public key that others use to encrypt or verify signatures. It also isn’t a password file.