Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Particular communication authentication technique
Reexamination Certificate
1998-08-26
2001-11-06
Peeso, Thomas R. (Department: 2132)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Particular communication authentication technique
C713S164000, C713S002000, C713S180000, C380S201000, C380S203000
Reexamination Certificate
active
06314518
ABSTRACT:
The invention relates to an arrangement for receiving via a transfer signal encoded content information and supplemental information, which content information comprises a watermark at least partly representing the supplemental information, the arrangement comprising a receiver device for receiving the transfer signal, a detector for detecting watermark information in dependence on the watermark, and a decoder coupled to an output of the receiver device for decoding the content information, which receiver device comprises control means for controlling the reproduction of the content information in dependence on the supplemental information.
Such a transfer system is known from WO 97/13248, document D1 in the list of related documents. In the transfer system information is transferred from the transmitter via a transfer signal to a receiver device, e.g. from a video producer via an optical disc to a disc drive for playback. The document describes that video and audio content is increasingly transmitted and recorded in a digitally encoded form, for example, an MPEG bitstream. There is a growing need to transfer supplemental information logically related to the content information, which supplemental information is intended for controlling the reproduction of the content information. The supplemental information may comprise information on the rights of the owner or originator of the content information. For example a marker is to be accommodated in such an encoded signal so as to classify the encoded signal as authentic program material. Marking digital signals is particularly useful in copy protection applications, wherein the supplemental information indicates the copyright status. Therefore the supplemental information should be protected against manipulation. The mark, also referred to as watermark, can effectively take the form of a multi-bit watermark pattern representing some supplemental information, e.g. indicating that the encoded signal constitutes copy protected content. In a digital video system, e.g. based on the digital videodisc (DVD), copy control can be based on detection of electronic watermarking. Watermarks are minor, imperceptible modifications to the video, which can be detected electronically. Such watermarks can be resistant to typical signal processing, including format conversions (e.g. PAL to NTSC), and can be detected to retrieve copyright information about the video. Watermarks are used for playback control. The basic idea of playback control is that any drive refuses to pass video content if that content contains a watermark that classifies the video as being no-copy while that video is found on a recordable medium. Hence playback control requires detection of the watermark within the drive, and a detector should be on the same chip as the drive control electronics or on the same circuit board in the drive. Noise-like, pixel-domain watermarks are not suitable for detection by a detector in the receiver device, because the complexity of the detector has to remain below a few thousand gates, as drives and DVD RAM recorders are designed as simple storage devices without any ‘intelligence’ to interpret data. Watermark detection would imply that such devices have process the content data, e.g. to demultiplex and interpret MPEG video streams, at least including run-length Huffman decoding of DCT coefficients. Hence a requirement of simplicity of playback control can not effectively be met by pixel-domain watermarks. So the known system has the problem, that the drive must be provided with a complex watermark detector.
It is an object of the invention to provide a more flexible system for controlling the playback of content information in dependence of supplemental information. For this purpose, the system according to the invention is characterized in that the arrangement comprises a decoder device comprising the decoder and the detector, which decoder device is arranged separately from the receiver device, and in that the receiver device and the decoder device comprise linking means for communicating the watermark information between the detector and the control means. This has the effect, that the complex content information decoder, which is present in a reproduction device, is used to perform the detection of the watermark, and communicates the result back to the receiving device. The receiving device controls the output signal in dependence of the communicated results. This has the advantage, that a high quality watermark, embedded within the encoded content signal, can be detected with very low additional complexity of the receiving and decoding arrangement.
According to a first aspect of the invention a receiver device for use in the arrangement is characterized in that the linking means are arranged for communicating with the decoder device for receiving the watermark information. According to a second aspect of the invention a decoder device for use in the arrangement is characterized in that the linking means are arranged for communicating with the receiver device for transmitting the watermark information. This has the advantage, that both devices can be produced separately and the total system cost is low, while a high quality watermark is used resulting in a high resistance against manipulation of the supplemental information.
An embodiment of the receiver device or the decoder device is characterized in that the linking means comprise means for securing the communication against tampering. In particular, the means for securing the communication comprise means for encryption or decryption, and/or for authentication, and/or for exchanging random numbers, and/or for providing or verifying a digital signature. This has the advantage that malicious parties are facing additional difficulties when trying to manipulate the supplemental information.
REFERENCES:
patent: 5724327 (1998-03-01), Timmermans et al.
patent: 5905800 (1999-05-01), Moskowitz et al.
patent: 5960081 (1999-09-01), Vynne et al.
patent: 6157330 (2000-12-01), Bruekers et al.
patent: WO 9713248 (1997-04-01), None
patent: WO 9800040 (1998-01-01), None
patent: WO 9800087 (1998-01-01), None
patent: WO 9800085 (1998-01-01), None
Belk Michael E.
Peeso Thomas R.
U.S. Philips Corporation
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