To enable exact terminal authentication on the side of a host even when password update timing is deviated between the host and a terminal in an authentication system for successively updating a used password in both the host and the terminal each time of authentication, based on the use of the password.
Concerning this system, a storage part 43 of a managing device 4 (host) is provided with a first buffer 43A for storing a password to be used for the next authentication and a second buffer 43B for storing a password used for the authentication of this time. When the authentication based on the password in the first buffer 43A is not established, the managing device 4 performs the authentication of a public telephone set (terminal) by using the password in the second buffer 43B.
YAMAGUCHI HIROYUKI
KAWAMATA MORIO
