Kerberos is a secure network authentication protocol designed for client-server model systems which provides strong authentication for client/server applications by using secret-key cryptography. It uses tickets and works on the basis of 'tickets' to allow nodes to prove their identity to one another in a secure manner. TACACS+ and RADIUS are both protocols used for similar purposes but they do not use tickets, and OAuth is an open standard for access delegation, commonly used as a way for Internet users to grant websites or applications access to their information on other websites but without giving them the passwords.