To improve the secrecy of a password by enciphering the password with a keyword preserved in another initial file.

One or plural passwords are enciphered while using any arbitrary keyword and preserved as a data file, this keyword is preserved in the initial file different from this data file, and when inputting the password to a computer, the computer reads the data file and the initial file and decodes the enciphered password while using the keyword. Besides, the data file preserves an item name corresponding to each password together with the password and when inputting the password to the computer, the list of item names is displayed on the screen of the computer. When any item name is selected out of the indication of this list, the password corresponding to that item name is inputted to the computer. Further, the initial file is preserved on a portable storage medium different from that of the data file.