In Public Key Infrastructure (PKI), the Certificate Authority (CA) is responsible for issuing digital certificates. The CA validates entities and binds their public keys with their respective identities through a process of registration and issuance of certificates. This process can be automated or carried out under human supervision. The Registration Authority (RA) often assists the CA by handling the vetting of certificate requests and authenticating the entity making the request, but it does not issue certificates. The CA maintains the integrity of the binding by ensuring that the certificates are issued according to industry norms and best practices, and it also manages the revocation of certificates when necessary.

References: The explanation is based on the standard roles and responsibilities defined within a PKI as outlined in various sources, including the Internet Engineering Task Force’s RFC 36471, which details the functions of an RA and clarifies that only a CA has the authority to issue certificates2345.