What is the function of the Key Distribution Center (KDC) in Kerberos?

The Key Distribution Center (KDC) plays a crucial role in the Kerberos authentication protocol by granting tickets that allow users to access servers securely. In the Kerberos framework, when a client wants to access a service, it first authenticates with the KDC to obtain a Ticket Granting Ticket (TGT). This TGT is then used to request service tickets for specific resources. The KDC validates the user's credentials and issues tickets that include encrypted session keys for secure communication. By handling the ticketing process, the KDC ensures that both authentication and secure key exchange are efficiently managed, enhancing security across the network.

The other options do not accurately encapsulate the primary functions of the KDC. Managing user passwords is typically handled by directory services rather than the KDC itself. The KDC does not merely distribute encryption keys for external communications; its role extends to facilitating secure authentication through ticket issuance. Additionally, while backup servers may be a necessary component of an overall data protection strategy, this function does not align with the primary responsibilities of the KDC in the Kerberos authentication model. Therefore, claiming that the KDC acts as a backup server for user data is misleading in the context of its core duties in network security and authentication.