What is a digital certificate and who issues it?

• A. It binds a public key to a domain and is issued by a Certificate Authority.
• B. It certifies a user’s identity in a social network and is issued by the platform.
• C. It encrypts emails end-to-end and does not require an issuer.
• D. It stores passwords securely in the browser.

Answer: (A)

Digital certificates are part of how the internet proves who a site or entity is. A certificate binds a public key to an identity (such as a domain) and is issued by a trusted Certificate Authority. The CA verifies the entity, signs the certificate with its private key, and publishes it so others can check the signature against the CA’s public key. When you visit a site, your browser uses this certificate to confirm the domain matches and to establish an encrypted TLS connection, trusting the certificate because it chains back to a trusted CA. This is why the description that says it binds a public key to a domain and is issued by a Certificate Authority is the best answer. The other descriptions describe different concepts (social identity on a platform, end-to-end encryption without an issuer, or browser-stored passwords) and don’t capture what a digital certificate actually is.