1. An information recording device for recording information on an optical disk comprising a first recording area and a second recording area, said device comprising: means for recording information using a first modulation method into a first recording area of such an optical disk; means for reading disk identification information recorded by a second modulation method in a second recording area of such an optical disk; means for encrypting information using a cipher key and any one such optical disk's unique identification information, into encrypted information unique to that one optical disk; and wherein said means for recording is capable of recording encrypted information unique to an optical disk in said first recording area of said optical disk.