Abstract: A cipher key is generated by first information shared in secrete between a data transmitting unit 10 and a data receiving unit 20, second information derived from duplication control information of transmit data and third information which is time change information shared between the data transmitting unit and the data receiving unit to cipher data by a CPU 12 by using the above-mentioned cipher key to transmit, from the data transmitting unit 10 to the data receiving unit 20, transmit data in which the duplication control information and the time change information are added to the ciphered data.

Abstract: A plurality of audio object (AOB) files and a plurality of picture object (POB) files are stored. Default Playlist Information and sets of Playlist Information each show an order in which AOBs stored in the plurality of AOB files are to be reproduced. The DPLGI includes DPLI_POB_SRPs that specify at least one POB to be displayed during the playback period of AOBs indicated by the playback order given in the Default Playlist Information. The TKGI includes TKI_POB_SRPs that specify at least one POB to be displayed only during the playback period of a particular AOB out of the AOBs indicated by the playback order given in the Default Playlist Information.