A recording disc has a lead-in area and a data area. A scrambled version of a SID code word is read out from the lead-in area of the disc. The SID code word represents a producer of the disc. The readout scrambled version is de-scrambled to recover the SID code word. The recovered SID code word is collated with reference SID code words to decide whether or not the disc is legitimate. Main information is read out from the data area of the disc when it is decided that the disc is legitimate. Readout of the main information from the data area of the disc is inhibited when it is decided that the disc is not legitimate.