Recording information with a watermark related to a prerecorded medium mark on an information carrier

Abstract

A system for copy protection of recorded information is disclosed, including an information carrier, a recorder and a player. The information carrier, e.g. an optical disc, includes a medium mark representing a first bitpattern, which medium mark cannot be copied on standard recording devices. The recorded information includes a watermark representing a second bitpattern, which second bitpattern has a predefined relationship to the first bitpattern. The watermark cannot be manipulated without disturbing the quality of the reproduction of the information. The relationship, preferably a one-way function, between the watermark and the medium mark requires that an illegal copy also has the corresponding medium mark. As neither the watermark nor the medium mark can be manipulated, a strong protection against illegal copying is achieved. The recorder includes encoder means for embedding the watermark in the information and generator means for generating the second bitpattern according to said relationship. The player includes verification means for verifying said relationship.