The present invention particularly relates, but is not limited to, a technology that facilitates the identification of a consumed content item and a user who consumed that item, and there is provided a proxy server that is capable of communicating with a client and a content server storing content for which permission data is required for reproduction. The proxy server comprises, in particular, a content information retrieving unit that retrieves, from the content server, content information that identifies the content server and the content, and a generating unit that generates modified content information that identifies the proxy server and the content identified by the content information.