Which function is performed by certificate authorities but is a limitation of registration authorities?

Both CAs and RAs (the latter often on behalf of the former) can accept enrollment requests from users or devices.

Certificate re-enrollment, like initial enrollment, typically involves submitting a request that can be processed by an RA before being issued by a CA.

Verifying user identity is a primary function of a Registration Authority, as they act as the trusted front-end to ensure that certificate requests are legitimate before forwarding them to the CA.

Certificate Authorities (CAs) are the entities that digitally sign and issue certificates, and critically, they are also responsible for publishing Certificate Revocation Lists (CRLs) or managing Online Certificate Status Protocol (OCSP) responses to indicate revoked certificates. Registration Authorities (RAs) act as intermediaries, verifying identities and accepting enrollment requests on behalf of the CA, but they do not have the authority to publish CRLs or issue certificates themselves.