Computer access control

A computer (2) uses a trace image booting password to control access to the computer. The computer (2) includes a sensing plane; a sensor unit (5) sensing a moving sensed unit (7) contacting the sensing plane; an image generator (11) generating a trace image along the movement of the sensed unit (7) as sensed by the sensor unit (5); and an image store (17) storing a predetermined image password based upon a predetermined image. The computer (2) further comprises a controller displaying (15) the predetermined image on a display screen (6) at booting time of the computer (2) to allow a user to move the sensed unit (7) in contact with the sensing plane over the displayed predetermined image, comparing a trace image generated by the image generator (11) along the moving trace of the sensed unit (7) by the user with the stored image password, and booting the computer (2) if the generated trace image corresponds to the stored image password.