Which of the following is an authentication protocol that uses a ticket-based system for access control?

PKI (Public Key Infrastructure) is a framework for managing digital certificates and public-key encryption, not a ticket-based authentication protocol.

Ciphers are algorithms used for encryption and decryption of data, not an authentication protocol of any kind.

WPA2 is a wireless network security standard that provides encryption for Wi-Fi communications, not a ticket-based authentication system.

Kerberos is a network authentication protocol that uses a trusted third-party Key Distribution Center (KDC) to issue encrypted tickets. When a user authenticates, they receive a Ticket Granting Ticket (TGT), which is then used to request service tickets for specific resources. This ticket-based system avoids sending credentials repeatedly across the network.