Patent ID: 7246228

Claim:
A communication system, comprising: a terminal device including reproduction means which carries out reproduction of a digital content; and a server machine which is connected to the terminal device via a communication link and includes program generation means for generating a device ID alteration program by which a device ID of the terminal device is altered, the communication system being characterized in that: the reproduction means includes ID setting means for setting a device ID corresponding to the terminal device; the digital content is reproduced only when a device ID included in the digital content corresponds to a device ID of a device by which it is intended to reproduce the digital content; when the device ID alteration program is supplied from the server machine, the device ID of the terminal device is altered in accordance with the device ID alteration program; and when the server machine receives a request to alter the device ID from the terminal device, the device ID alteration program is sent to the terminal device, and the reproduction means sends only (I) a user identification ID for identifying a user, (II) an authentication password corresponding to the user identification ID, and (III) a device ID which is desired to be recovered, to the server machine, the server machine further includes: a customer information management database which stores user identification IDs of formerly registered users and corresponding authentication passwords; and user identification means for judging whether or not the user identification ID and the authentication password, which have been received, correspond to any one of the user identification IDs and any one of the authentication passwords, which are stored in the customer information management database, and if the user identification means confirms that the user is formally registered, the program generation means generates a device alteration program by which the device ID set by the setting means of the reproduction means is replaced with the device ID which is desired to be recovered, and thereafter the device ID alteration program is supplied to the terminal device.