| 摘要 |
PROBLEM TO BE SOLVED: To prevent the illegal usage of a card-shaped medium by making decoding difficult. SOLUTION: Random data and data enciphered based on these random data are recorded on the respective 1st tracks for recording of the card-shaped medium, and the added result of random data and the added result of enciphered data are recorded on the 1st tracks for recording. When reading data, the data recorded on the 1st and 2nd tracks for recording of the card-shaped medium are read, and the read random data and enciphered data on the 1st tracks for recording are respectively added by an arithmetic part 5d. Then, a control part 5a collates the added result of random data and the added result of enciphered data with the read data on the 2nd track for recording and judges whether the random data and enciphered data on the respective 1st tracks for recording are correct or not and when these data are correct, they are decoded to the original data by a data decoder part 5e based on the random data on the 1st tracks for recording. |
