An image processing system has a host computer to which a scanner and a printer are connected. A color space conversion module, for converting a color space of a device input-output image into a predetermined color space, likewise a resolution conversion module, for converting the resolution of the image into a predetermined resolution, and a counterfeit determination module, which determines a degree of a match between the image signal converted into predetermined color space and resolution and a particular image, are included in the OS of the host computer. The OS further includes an anti-counterfeiting module for preventing or suppressing counterfeiting based on the results of the matching determination. By providing the various modules in the OS instead of the device, the system is able to provide counterfeiting prevention and anti-counterfeiting capabilities designed to accommodate a plurality of different types of input-out devices efficiently.