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Abstract

A system for embedding and detecting digital watermarks, e.g., for copyright protection of digital content distributed via the Internet or other channels. Different copies of content, such as audio data, are formed with a common watermark (CW), and different transaction watermarks (TW). Based on a user transaction request, portions of the different copies of the content are assembled to provide a copy with a unique sequence of TWs associated with the user. A copy of content which is subsequently located can be analyzed to determine if it has been used in a collusion attack, where a pirate attempts to modify the watermarks, e.g., in an averaging or cut-and-splice attack. The CWs are provided in time-aligned intervals of the different copies of the content so they are not modified by the attack. Content from different web sites can be analyzed by first determining if a particular CW is embedded in the content, and, if so, recovering the TW to identify the unauthorized distributor.

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First Claim