A user sends a request signal to a delivery management server 60 by utilizing a mobile station 10 in response to a broadcast service provided by a broadcast station 70. The request signal includes a music song ID of music song data segments which the user wants to be delivered and also an address of the destination to which the music song data segments be delivered. Upon the receipt of the request signal, the delivery management server 60 returns, in the case of unpopular songs, the music song data segments and a decrypting key for decrypting the data segments, and on the other hand, it returns, in the case of popular songs, only the decrypting key to the mobile station 10 or a STB 40. The mobile station 10 or the STB 40 decodes, in the case of unpopular songs, the music song data segments received from the delivery management server 60 by utilizing the decrypting key therefor and on the other hand, it receives, in the case of popular songs, the music song data segments in the broadcast waves provided from the broadcast station 70 and then decrypts data segments by utilizing the decrypting key received from the delivery management server 60.