Abstract: Security is a very important aspect in network.Authentication is fundamental in maintaining security in the nework.Authentication is a process that satisfies another about one's claim of identity,which quality affects the security and performance of the system.Many activities cannot proceed without authentication because its compromise can lead to the compromise of the whole system.Therefore,a desirable authentication serices should be both highly reliable and secure.A threshold-based authentication service is presented in this paper,and reliability and security of the service are analyzed.Adjusting the thresholds can explore the tradeoff between reliability and security.