Between a digital multi-function peripheral for processing data, and one or a plurality of memory devices for giving an instruction for the digital multi-function peripheral to process data, when the memory device(s) contacts a display surface of a display section of the digital multi-function peripheral, the digital multi-function peripheral accepts a first instruction concerning authentication and a second instruction concerning processing of the data based on a contact position, in this case, acquires first identification data stored in the memory device(s) concerning the first instruction and second identification data stored in the memory device(s) concerning the second instruction, and when the first identification data and the second identification data do not coincide with each other, invalidates the accepted second instruction.