Patent ID: 8539244

Claim:
An authentication server used in a content delivery system to deliver contents via a network to a plurality of an information processing terminals which are used by a single service user and which individually play back the contents, the content delivery system including a delivery server and the authentication server, the authentication server comprising: a memory and a processor; a control unit configured to: manage unique information of each of the information processing terminals as the device authentication IDs and information relating to the single service user as a user authentication ID, and which collectively manages, ID management information representative of a relationship between the device authentication IDs and the user authentication ID; respond to a content delivery request issued by the use of each device authentication ID from each of the processing information processing terminals; acquire the user authentication ID collectively managed with each of the device authentication IDs with reference to the ID management information; perform an authentication relating to the content delivery request by the use of the user authentication ID and device identification IDs to determine whether or not the contents are delivered to each of the information processing terminals and to determine whether or not the contents are taken over from one of the information processing terminals to another one with reference to the additional information; and generates the additional information needed for taking over the contents between the plurality of the information processing terminals, the additional information being transmitted to the delivery server along with an authentication result and being used to continuously deliver the contents to the single service user even when the information processing terminals of the single service user are changed from one to another.