| 摘要 |
When a technique for specifying an unauthorized terminal based on a combination of watermarks embedded in content distributed without authorization is applied to content distributed on recording media, recording capacity limits of the recording media lead to a limit on the number of combinations of watermarks that can be embedded in the content, and only a limited number of terminals can be specified. In the present invention, all terminals are sorted into the same number of groups as there are combinations of watermarks, and a group that includes an unauthorized terminal can be specified based on the combination of watermarks embedded in the content. When the group including the unauthorized terminal is specified, this group is divided into groups, and a plurality of groups that do not include the unauthorized terminal are integrated. This enables the unauthorized terminal to be specified while keeping within the capacity of the recording medium.
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