A content providing server connected to a home network or the like is configured in such a way as to store a content key, which is encrypted by a network key shared by network-connected devices and appropriately updated, in a storage together with encrypted content, and as to hold a network key table in which all network keys including all pre-update network keys, which are being applied to encrypted content keys, are registered and stored. This server performs a key changing operation of changing a content key, which is encrypted by a pre-update network key, to an encrypted key, to which an updated network key is applied, only when needed, for example, at an occurrence of utilization of the content. Consequently, this configuration prevents key changing operations from being wastefully performed. Thus, the processing load on the server is alleviated.