Abstract: Recently developed methods for copy protection rely on a watermark detector to judge whether multimedia content can be copied or not. In such copy protection schemes, a watermark detector examines the multimedia content and outputs a signal (D) indicating whether a watermark is present or not. Known watermark detectors determine a decision variable (y) indicating to which extent the watermark is present, for example, the amount of correlation between the input signal and a reference copy of the watermark to be detected. The watermark is detected if the decision variable exceeds a predetermined threshold (y2). Such a detector is vulnerable to an attack which is described in this patent application.

Abstract: A method and arrangement for detecting a watermark in an information signal. The method may include the steps of computing the correlation (dk) of the watermark (Wi) and the information signal (e.g. an image Q) for a plurality of positions (k) of the watermark with respect to the information signal, and detecting whether at least one of the respective correlation values exceeds a given threshold. The step of detecting may include determining the standard deviation (&sgr;d) of the respective correlation values (dk), and setting the threshold to a given multiple (T) of the standard deviation. The multiple (T) is derived form a desired false alarm rate (watermark detected when there is none, or no watermark detected when there is one).

Abstract: Recent copy-protection schemes for digital video copy-protection rely on a pixel-watermark together with the presence of a ‘ticket’ to implement the ‘copy-once’ state of content. This ticket is designed to entitle the owner of a disk/tape to making one copy of digital content. We disclose a method to pass along this ticket with the video signal after content has been converted to the analog domain. This form of the ticket is called the analog ticket. The analog signal may be recorded on a legacy device that does not comply with the copy-protection scheme (e.g. ordinary VCRs). The analog ticket is designed such that it is automatically removed in these legacy devices. Next generation copies by compliant devices are made impossible. Three possible ways of embedding the ticket signal into the analog video signal are proposed.

Abstract: A watermark detector is disclosed to judge whether multimedia content can be copied or not. The watermark detector examines the multimedia content and outputs a signal indicating whether a watermark is present or not. A decision variable indicating to which extent the watermark is present is determined, for example, the amount of correlation between the input signal and a reference copy of the watermark to be detected. The watermark is detected if the decision variable exceeds a predetermined threshold (y2). The detector also generates a random output signal for a predetermined range of decision values between the threshold (y2) and a further threshold (y1).

Abstract: A system for copy protecting content information has an arrangement for receiving and controlling the playback of encoded video. The video content, e.g. MPEG compressed digital video, is watermarked and includes a control signal indicating the status (e.g. playback only, one generation of copy allowed, etc). In the receiver device a check is performed to allow playback in dependence of the watermark. The watermark is extracted in a separate decoder device, such as an external MPEG decoder. The receiver device starts the playback via the external decoder, and the separate decoder communicates retrieved watermark information via a link to the playback device. The playback device checks the watermark information against further supplemental information, such as a physical mark on the record carrier or the control signal. Said communication may be protected by cryptographic methods, such as a digital signature.

Abstract: Recently developed methods for copy protection rely on a watermark detector to judge whether multimedia content can be copied or not. In such copy protection schemes, a watermark detector examines the multimedia content and outputs a signal (D) indicating whether a watermark is present or not. Known watermark detectors determine a decision variable (y) indicating to which extent the watermark is present, for example, the amount of correlation between input signal and a reference copy of the watermark to be detected. The watermark is detected if the decision variable exceeds a predetermined threshold (ythr) In accordance with the invention, the threshold value (ythr) is adaptively controlled in dependence upon statistical characteristics of the information signal and a desired probability of false alarms (watermark detected whereas the signal is not watermarked).

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.

Abstract: An electronic watermarking scheme is proposed that can significantly increase the security of copy protection mechanisms. The watermarking methods works at high level in the hierarchy of the (MPEG) source signal. This ensures that the watermark is easily detectable, but difficult to erase without significant transcoding effort. Such transcoding is considered a difficult and expensive task that may furthermore lead to loss of quality or increase in bit rate.

Abstract: To detect a watermark signal embedded within an information signal, predictive filtering is applied to either the information signal, a plurality of applied watermark signals, or both types of signals. After the filtering, a correlation is determined between the information signal and the watermark signals. The amount of the correlation is indicative of whether a particular watermark is embedded within the information signal.