PROBLEM TO BE SOLVED: To prevent advertising effectiveness from being lost even after a time passes since content is publicized when an advertisement is made to be viewed along with the content including images and sound.;SOLUTION: A reproduction device 2 for reproducing content data and a management server 5 are connected so that they may be mutually communicable. The reproduction device 2 reads content data 7 from an optical disk recording medium 10 or a content storage part 30, requests the management server 5 of a decode key 62 for canceling restriction about reproduction of the content data 7, and when the advertisement data 66 are transmitted together with the decode key 62 from the management server 5 in response to the request, reproduces the content data 7 by using the decode key 62 after the transmitted advertisement data 66 are reproduced.;COPYRIGHT: (C)2010,JPO&INPIT
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