1. A personal authentication method for use in a network system, said network system comprising an electronic computer connected with a plurality of devices, including a first network card for connecting to said network system and an input device, and operated by an operating system, and a server comprising a second network card for connecting to said network system and storage means for storing a database, including personal information concerning a user using the electronic computer; wherein when said user actuates said input device, an actuation time when said user actuates said input device is obtained on a kernel mode that is an operating mode in which all instructions of said operating system are executable; input information including said actuation time is transmitted to said server by said first network card; said server receives said input information by said second network card, analyzes said input information, and obtains actuation characteristics; said server performs personal authentication of said user by comparing said actuating characteristics with said personal information.