The password is the first step for computer security. If security of password is unimportant even constructing of fire-wall, it is useless. But end-user is not able to manage a high-difficulty password. So complement for password management is needed. In this paper, algorithm which produces one time password by using random number in client is used. Not oかy this is easy for end-user to manage password, but also this can eliminate insecurity for server hacking.