What is the main purpose of a digital certificate issued by a Certificate Authority (CA)?

### Why this is right A digital certificate is an electronic document that helps prove ownership of a public key. The certificate authority issues it and binds the key to an identity, allowing others to assess whether the key belongs to the claimed website, server, or user. ### The concept Public-key encryption depends on using the correct public key. A certificate helps address the question, “Does this key really belong to the party it claims to represent?” Certificates support authentication and trust through a chain associated with the certificate authority. They do not themselves encrypt every message or make a private key public. ### The other options - **B. To encrypt every message without using any keys**: A certificate is an identity-and-key document, not a keyless encryption mechanism. - **C. To prove that encrypted data is available during an attack**: Certificates support identity and trust, not availability under attack. - **D. To replace the private key with a publicly shared copy**: A private key remains secret; a certificate associates an identity with a public key. ### Terms - **CA**: Certificate Authority, a trusted body that issues digital certificates. - **Digital certificate**: An electronic document binding an identity to a public key. - **Authentication**: Checking that a party is who it claims to be. ### Remember A certificate helps you trust the identity associated with a public key.