Content delivery apparatus, user terminal device, relief management method and computer program

A method for delivering a content item in a content delivery system, the content delivery system including a computer that encrypts and delivers a content in response to a request received via a network from a user terminal device, and to manage a valid period for the user terminal device to use the content, the method comprising:

• detecting, by the computer, a period of time when communication on the network fails;
• specifying, by the computer, a user terminal device to be issued a relief right, by determining that the valid period for the user terminal device to use the content overlaps with the period of time when the communication fails;
• issuing, by the computer, the relief right to the user terminal device, the relief right indicating a relief period that allows the user terminal to decrypt the content at a time after the expiration of the valid period;
• sending, by the computer, a notification to the user terminal device to notify a corresponding user of the issued relief right;
• receiving, by computer from the user terminal, a view request to decrypt the content based on the relief right, the view request being received after the expiration of the valid period, and within the relief period;
• delivering, by the computer, view permission information for the user terminal device to decrypt the content in response to the view request;
• and
• storing, in a storage device, at least one of the view permission information or the content.