摘要:The Gurevich's Abstract State Machine formalism is used to specify the well known Kerberos Authentication System based on the Needham-Schroeder authentication protocol. A complete model of the system is reached through stepwise refinements of ASMs, and is used as a basis both to discover the minimum assumptions to guarantee the correctness of the system and to analyse its security weaknesses. Each refined model comes together with a correctness refinement theorem.