Patent ID: 8117463

Claim:
An information device, comprising: means for storing a content file including an encrypted content and an encrypted key block, and a license including grouped device identification information; means for receiving key information in response to a transmission of device identification information of the information device and the grouped device identification information over a network and upon a determination that fewer than a predetermined number of information devices are associated with the grouped device identification information, and for receiving the license; means for using the content by reading out the grouped device identification information from the license, reading out the key information based on the grouped device identification information, decrypting the encrypted key block based on the key information, and decrypting the encrypted content based on the key block; and means for transmitting a deletion request over the network when at least the predetermined number of information devices are associated with the grouped device identification information, the deletion request identifying the grouped device identification information and the device identification information of the information device, wherein, when the information device receives a deletion completion notice after a transmission of the deletion request, the means for using deletes the key information.