PURPOSE: To surely keep the security by storing data peculiar to an information processor and making the processing executable when data added to an informa tion storage medium coincides with stored data.

CONSTITUTION: A buffer memory 52, an operating circuit 53, and a deciding circuit 54 constitute a device specifying mechanism 51, and the peculiar data of a picture information memory device 1 is stored in the memory 52 when the device 1 is installed, and device data obtained by adding one to peculiar data is written in the prescribed block of a disk 19 by a CPU 32 when an optical disk 19 is inserted to an optical disk device. Peculiar data and device data are compared with each other by the circuit 54 when data on the disk 19 is read out, and a desired processing is performed when they coincide with each other.