What is the purpose of a digital certificate?

A digital certificate serves primarily to verify that a public key truly belongs to the individual or entity that claims to own it. It acts as an electronic "passport" for identifying and authenticating the holder of a public key. This verification is crucial in establishing trust during communications over the internet, particularly in secure environments, as it confirms that the public key is associated with the correct identity and not an imposter.

Digital certificates are issued by trusted entities known as Certificate Authorities (CAs). These authorities validate the identities of the entities seeking a certificate and bind the public key to that identity. When someone receives a digital certificate, they can ensure that the public key within it can be trusted to encrypt messages or verify signatures related to that identity.

In contrast, other options address different aspects of security but are not the primary purpose of a digital certificate. For example, confirming a computer is virus-free involves antivirus measures rather than digital certificates, while indicating ownership of a private key is not relevant since private keys should remain confidential and not be shared. Additionally, ensuring that a digital document is complete typically relates to data integrity checks rather than the function of a digital certificate.