When a user makes a remote log-in to a server apparatus from a terminal apparatus, a password managing apparatus, which manages the name of a user of the server apparatus, his/her direct log-in password and transformation rule, displays an authentication purpose symbol sequence on a display apparatus. The user transforms the displayed sequence by his/her transformation rule and supplies, via the terminal apparatus, his/her user name and the post-transformation symbol sequence to the server apparatus, which then sends them to the password managing apparatus. If the result of applying the user's transformation rule to any authentication purpose symbol sequence generated in the past coincides with the post-transformation symbol sequence, the password managing apparatus sends the direct log-in password to the server apparatus to pass the remote log-in to the server apparatus by the terminal apparatus as a success.