Importance

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Abstract

A method and system for recording and reproducing, such as on a record carrier, content information and supplemental information relating thereto. The content information may be audio and/or video, and the supplemental information may provide author identification and/or copy control status. An encoded signal is generated representing the content information and which includes a watermark pattern representing the supplemental information. The watermark pattern cannot be changed without impairing the quality of the content information during reproduction. The supplemental information also includes a control pattern, the watermark being generated by applying a one-way function to such control pattern. This has the advantage that any alteration of the watermark or the control pattern can be detected easily, because it is not computationally feasible to calculate a new control pattern for an altered watermark. Therefore, the supplemental information is well protected against unauthorized manipulation. An attempt to fully replace the watermark pattern will affect the quality of reproduction of the content information. In a copy control method allowing a first generation copy ('copy-once'), the original control pattern is processed several times by the one-way function for generating the watermark. Each player or recorder processes the control pattern once before outputting/recording it, thus forming a cryptographically protected down-counter.

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First Claim