A reduction-based proof for authentication and session key security in three-party Kerberos

Abstract

This paper presents a reduction-based proof framework for establishing authentication and session key security in a three-party cryptographic protocol. The proposed analysis considers interactions among three entities, such as a user, a service provider, and a trusted authority, and formally examines the security of their authentication and session establishment processes. Security is demonstrated through a sequence of reductions to well-established computational assumptions, showing that an adversary capable of successfully impersonating a legitimate participant or distinguishing the established session key could be transformed into an algorithm capable of solving an underlying hard problem. The proof framework incorporates resistance against common threats, including replay attacks, impersonation, session-key compromise, and active adversarial interference. The results provide a rigorous foundation for evaluating three-party authentication protocols and demonstrate that session keys remain computationally indistinguishable from random values under the assumed security conditions