Patent ID: 7426494

Claim:
A playback device for acquiring and playing back a digital work provided from a provider to a rental agent and rented from the rental agent to a user, the rental agent being operable to provide to the user the digital work and a rental agent identifier identifying the rental agent, said playback device comprising: a time acquisition unit for acquiring time information including a current time from a time source device; an expiry acquisition unit for acquiring user-expiry information from the rental agent and agent-expiry information from the provider, the user-expiry information including a user expiry time of a period during which the user is permitted by the rental agent to play back the digital work, and the agent-expiry information including a rental expiry time of a period during which the rental agent is permitted by the provider to rent the digital work; a first comparison unit for comparing the current time included in the time information acquired by said time acquisition unit with the user expiry time included in the user-expiry information acquired by said expiry acquisition unit; a second comparison unit for comparing the current time included in the time information acquired by said time acquisition unit with the rental expiry time included in the agent-expiry information acquired by said expiry acquisition unit in response to the current time being not later than the user expiry time; a prohibition unit for prohibiting playback of the digital work in response to the current time included in the time information being later than at least one of the rental expiry time included in the agent-expiry information and the user expiry time included in the user-expiry information; and a rental agent identifier transmission unit for transmitting the rental agent identifier to the provider in response to the current time being later than the rental expiry time.