Secret information indentification system

In a secret information identification system, an input password (PWIN) is compared with a registered password (PWREG) every time a permission signal (ST) is generated. Lock release permission is given when a comparison result (SCOMP) indicates coincidence. Alternatively, an input password is compared with a registered password and lock release permission is given every time a permission signal is generated when the comparison indicates coincidence. The cycle of generation of the permission signal is elongated as the number of events of non-coincidence in comparison results increases. As a result, the password is not easily broken, and further the password input function is not locked even after input of a wrong password.