单点登录源代码，其中BOB开两个程序，被认为BOB,和ALIC两个用户，BOB与ALICE想要通信，AS,TGS为服务器，帮助他们交换密码，保护通信安全-Single Sign-source code, one of the two specific procedures BOB was considered BOB, and ALIC two users, BOB and ALICE want communication, AS, TGS for the server to help them