A security administrator is evaluating three different services: radius, diameter, and Kerberos. Which of the following is a feature that is UNIQUE to Kerberos?

RADIUS and Diameter also provide authentication services, making this feature not unique to Kerberos.

Kerberos uses a ticket-based system, specifically a Ticket Granting Ticket (TGT) and service tickets, to prove a user's identity to various services without re-entering credentials for each, a method distinct from the challenge-response or attribute-value pair exchanges of RADIUS and Diameter.

While Kerberos provides single sign-on, RADIUS and Diameter can also be integral components in implementing SSO solutions, meaning it is not unique to Kerberos.

Kerberos does not primarily use XML for its core operations or cross-platform interoperability; Diameter, however, can use XML for certain attribute definitions, making this statement inaccurate for Kerberos and not a unique feature anyway.