Image data, such as image data coded in MPEG4 format, is verified by a client receiving an information data stream that is generated by multiplexing a plurality of coded object data and associated intellectual property management data, from a contents distribution server, wherein the intellectual property management data includes source information representing a copyright holder of the object data. Verification request data is transmitted, based on the source information included in the received intellectual property management data, to the copyright holder, via a different communication channel from that used for receiving the information data stream. The client receives, from the copyright holder, verification result data relating to the object data and then, a decoding process of the object data is controlled based on the verification result data.