A game playing system includes a use permission tag provided for use in a game disk for a user of a game, a disk drive, and a reproduction device for reproducing the game. The disk drive reads out a disk ID from the game disk. When the game is to be played, the reproduction device conveys the disk ID and a player ID to the use permission tag. The use permission tag stores the terms of use of the game and determines whether a combination of the disk ID and the player ID conveyed from the reproduction device fulfills the terms of use or not.

the best bit:
By employing the game playing system 1000 according to the present embodiment, the use permission tag 220 together with the game disk 210 is supplied to the user, and the use permission tag 220 actively determines the use permit/rejection of electronic content. Thereby, the use of game AP stored in the game disk 210 can be restricted as appropriate according to the attribute of a reproduction device. Consider, for example, a case where used is a game package 200 distributed in the second-hand market. Then the ID of reproduction device for the game disk 210 differs from the legitimate use device ID stored in the use permission tag 220, so that the game disk can be reproduced in a mode which is predetermined for those bought and sold in the second-hand market. Also, for example, a content key may be supplied to the reproduction device 130 and the encrypted game AP may be decrypted using the content key only if the reproduction device ID matches a legitimate use device ID. Hence, use of game APs bought and sold in the second-hand market can be eliminated.