Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
  • G11B20/10—Digital recording or reproducing
  • G11B20/12—Formatting, e.g. arrangement of data block or words on the record carriers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
  • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
  • H04N5/913—Television signal processing therefor for scrambling ; for copy protection
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/76—Television signal recording
  • H04N5/91—Television signal processing therefor
  • H04N5/913—Television signal processing therefor for scrambling ; for copy protection
  • H04N2005/91307—Television signal processing therefor for scrambling ; for copy protection by adding a copy protection signal to the video signal
  • H04N2005/91335—Television signal processing therefor for scrambling ; for copy protection by adding a copy protection signal to the video signal the copy protection signal being a watermark

Definitions

• the present invention relates to a method and apparatus for marking and preparing streams of data such as video or audio data, for the purpose of tracing the source of unauthorised copying and distribution.
• a state of the art procedure for marking digital media with an identification code is thus to select a predetermined portion, in time and/or space, of the recorded material and to insert a code signal on the selected portion.
• a code signal For video recording e.g. the luminance of a certain pixel at a certain point in time is raised whereas the luminance for another pixel next to the first pixel is lowered, leaving the average luminance unaltered.
• endless ways of introducing different sequences of altered information that are inconceivable by the end-user, i.e. the viewer or listener of the material, can be thought of. Since this code is inserted into the data of the material, direct copying of the material, e.g.
• US 5,394,274 discloses a system for preventing unauthorised copying of audio or video recordings by (1) processing the recorded material so as to identify the protected material in a manner that does not audibly distort the program material, and (2) processing the recorded material by a second method that produces audible artifacts.
• Equipment capable of removing the audible artifacts while retaining the inaudible identification signal would be installed in audio digital tape recorders or video recorders so as to allow the equipment to be used for playback purposes while at the same time discouraging the unauthorised copying of audio, video or motion picture protected material.
• the proposed solution suffers inter alia from the drawback the need for special equipment to be installed for playback purposes. Furthermore, it does not deal with, nor solve, the problem of preventing detection of identification markings or the like encoded into digitally recorded data.
• an object of the present invention is to provide a method and an apparatus for improving traceability of the source of illegally copied and distributed media, such as video and audio recordings. More specifically, an object of the invention is to overcome the known deficiencies of the prior art techniques regarding identity code marking of digital recorded data streams, by providing the material with an identity code which is not easily found by simple comparison between two copies of the same material having different identity codes.
• the above mentioned objects of the present invention are fulfilled by a method and an apparatus for implementing an identification code together with the data of a data stream, and to actively introduce a disturbance signal into the data stream, obscuring the presence of the identification code.
• the disturbance signal is true random noise at a level below the cognitive threshold of a viewer or listener of the material that is represented by the data stream.
• the magnitude of the noise is on average the same as the changes in the data introduced by the insertion of the identity code. Since the noise has true random behaviour, subtraction of one copy from another will not lead to any decrease in noise level. Hence, such a comparison will not lead to the uncovering of the identity codes.
• the inventive apparatus and method is preferably used for recording audio or video material on digital recording media, including optical means such as DVD and CD as well as magnetic tape recording media, but is also useable for analog recordings.
• the invention is particularly suitable for marking video data streams transmitted to a video-on- demand user.
• the invention relates to a data stream preparing apparatus for implementing an identification code together with the data of such a data stream, comprising: an input for a data stream; means for actively introducing a disturbance signal into said data stream; means for inserting a predetermined identification code into said data stream; and an output for the data stream including the inserted code and disturbance signal.
• a data stream transformer connectable to said data stream input, preferably has a control signal input connected to a signing key transformer, and to a random disturbance signal source.
• the invention relates to a method for marking a data stream, comprising the steps of: inputting a data stream into a data stream transformer of a marking apparatus; inputting a predetermined identification code control signal into a control signal input of the data stream transformer; inputting a random disturbance signal into said control signal input; inserting a predetermined identity code by transforming said data stream dependent on the signals input in said control signal input; outputting the transformed data stream from the marking apparatus.
• the invention relates to a data stream transformer for implementing an identification code together with the data of an input data stream, comprising: a data stream input; a control signal input connectable both to a signing key transformer, and to a random disturbance signal source; transforming means, for transforming an input data stream dependent on an input control signal; and a data stream output.
• the invention relates to a system for identification marking of a data stream, the system comprising a control signal, and a data preparing apparatus for implementing an identification code together with the data of a data stream dependent on such a control signal, the apparatus comprising: a data stream input; a control signal input; transforming means, for transforming an input data stream dependent on an input control signal; a data stream output, said control signal comprising a predetermined identification code, and a random disturbance signal.
• figure 1 is a block diagram of the procedure for signing a data stream, according to an embodiment of the inventive method
• figure 2 is a schematic illustration of one embodiment of the inventive apparatus.
• figure 3 is a schematic illustration of another embodiment of the inventive apparatus.
• the present invention refers to identity marking of data streams representing recorded audio or video signals, such as music or movies.
• Numerous ways of introducing an identity code into an audio or video recording have been proposed, such that the identity code is inconceivable for the viewer or listener of the material, such as the aforementioned patent US 5,613,004.
• the identity code as such does not require a lot of bandwidth. Less than 100 bytes of code are enough to guarantee a uniquely coded copy for each person on the planet.
• the realisation of the identity code can be performed in many ways. For video, e.g., two adjacent pixels can be given an increased and decreased luminance amplitude respectively, still maintaining the correct average luminance. Performed correctly, such an identity code will not be conceivable by the viewer of the video material.
• the identity code can be realised by various amplitude changes or even by frequency or phase changes.
• the code is repeated on several, or preferably all frames of audio or video, making it possible to find the source identity using only a portion of the recording on an illegal copy. It is also possible to encode the identity code in the data stream, e.g. video, in a part of said stream that is not even devised to be presented to the viewer/listener.
• the invention is not directly focused on the means or techniques for introducing the identity codes into the data streams, but is intended to be useable together with any of such state of the art means and methods for marking media recordings.
• the purpose of the invention is to make it much more difficult to find the identity code of a copy of a recording by a simple comparison with another copy with a recording of the same material but with another identity code.
• the reason why the identity codes can be found by this comparison is that apart from the identity code the material, or data streams representing the material, is more or less the same.
• the problem is more severe for digital recordings, since in that case the data streams are in fact identical.
• the way of overcoming the problem that the identity codes can be easily found by comparison of different copies is to prepare each copy of a certain recording to be unique, even without the identity code. Furthermore, the difference between two copies shall not be conceivable by a viewer or listener of the material from two different copies.
• the proposed way of achieving this is to actively introduce a disturbance signal into the data stream of the recording. This disturbance signal must be unique to the extent that two copies of the same recording must not have the same disturbance signal.
• the disturbance signal is achieved by a true random noise generator, also called a Hardware Random Number Generator.
• a true random noise generator also called a Hardware Random Number Generator.
• the disturbance signal may, as previously mentioned for the identification code, also be introduced in parts of the data stream that do not represent information that is to be presented to the viewer/listener.
• true random noise the disturbance signal, however small, will be completely unique for each copy.
• a difference between the disturbance signal and the identity code, which also preferably is unique for every copy or group of copies, is that the pattern of the disturbance signal is unknown although it is actively introduced.
• the disturbance signal characterised by true random noise can not be reduced by recording by simple comparison between two copies. Subtraction or addition of the signals from two different copies will give the same result, namely a doubled noise level. Subsequent averaging can of course be performed but the resulting level of noise will be the same as for any of the two compared copies.
• the identification code may be constructed by using a variety of different methods as previously mentioned. It would be an advantage if these methods be regularly changed as this would make the work more difficult for an attacker. These methods, including the identification codes themselves and all secret parameters used, should be kept secret by the copyright holder. As the bandwidth needed for noise injection is very limited, as compared to the bandwidth utilised by the material itself, the quality problem associated with the noise injection will be slight or diminutive. In one embodiment of the present invention a secret key stream cipher, or a Pseudo Random Number Generator, is used instead of a true random noise generator to generate the disturbance signal. Since the number of identical copies to be individually signed and distributed are often counted in thousands, it is not necessary to use a true random number generator.
• the inventive apparatus and method is applicable to the insertion of an identity code, in the form of a signature key, and a disturbance signal in data streams representing e.g. recorded music or speech, a picture or moving pictures, a computer or video game, or a computer program.
• the procedure of the inventive method is first to take an unsigned data stream, such as a digital video recording, and second to add noise to the data stream.
• the data stream comprising noise is then marked by use of some appropriate method, as previously described.
• a signing key is provided and used for performing a transformation in order to give this specific copy, or group of copies, a marking inside the data stream.
• the result is a data stream comprising both the key and noise.
• the source of the copy is easily revealed, essentially by reversing the method of Fig. 1.
• the steps of adding noise and signing the stream are reversed, i.e. the stream is first signed, after which noise is added.
• noise addition and signing transformation is achieved in one step.
• the apparatus 1 comprises a first input 2 for a data stream.
• a second input 3 is devised for input of noise.
• a noise adder 4 comprised in the inventive apparatus 1
• an input data stream from the first input 2 is added with noise from the second input 3.
• the apparatus 1 further has a third input 5 for a signing key.
• the signing key is preferably a code for the purchaser, or receiver, of the copy, but can also contain information on the distributor, the copying date, etc.
• a signing key transformer 6 in the apparatus 1 is devised to transform the input code by a secret procedure, in a manner well known in the art.
• a signing adder 7, comprised in the apparatus 1, is then useable for adding the transformed code into the noise impeded data stream, before outputting the signed data stream comprising noise through an output 8 of the apparatus 1.
• Figure 3 illustrates an alternative embodiment of the apparatus 1 according to the invention.
• the apparatus 1 comprises a first input 2 for a data stream.
• a second input 3 is devised for input of noise from a random disturbance signal source.
• the apparatus may comprise a noise generator, constituting the source of the random disturbance signal.
• the apparatus further has a third 5 input for a signing key.
• a signing key transformer 9 in the apparatus 1 is devised to transform the input code by a secret procedure, in a manner well known in the art.
• the output of signing key transformer 9 is a control signal useable by a data stream transformer 10, connected to the signing key transformer 9 by a control signal input 11.
• the data stream transformer 10 has a data stream input 12, connectable to input 2, and a data stream output 13, connectable to output 8.
• the data stream transformer 10 comprises data stream transforming means, devised to transform the data stream dependent on a control signal inserted through said control signal input 1 1. Furthermore, said second input 3 for noise is connected to said control signal input 11 of the data stream transformer 10. Hence, the data stream transformer will not be able to separate between predetermined control signals originating from the signing key transformer 9, and random noise originating from input 3. Consequently, in case the identification code is not known in advance, it will be nearly impossible to detect in a prepared data stream which alterations are caused by the identification code, and which are caused by noise.
• a feature of the invention is that the introduced noise and ID marking are of the same kind, since they are introduced by the same mechanism, namely by transformer 10, and are applied to the same portion of the data stream.
• the data stream is to be marked e.g. by an identification code creating pixel value variations in the picture frames of the video signal, executed by the transformer 10, this is also how and where the noise is added.
• the noise added is of the same magnitude as the identification code, if a magnitude can be related to the implemented marking. Or to put it in other words:
• the disturbance effect of the data stream created by the identification code marking and the disturbance signal, i.e. noise, implementation is the same.
• the difference is that the ID marking, being carefully chosen and controlled, has a pattern representing the identification code, and preferably a redundancy, whereas the disturbance signal is random.
• the disturbance signal obscuring the marking makes the identification code very difficult to locate.
• the apparatus may be realised in hardware as an electronic circuit, or as a part of an ASIC, Application Specific Integrated Circuit.
• the inventive apparatus may also be realised in software, as a computer program product for use with a data processing and storage system, for carrying out the inventive steps.
• the inventive apparatus according to Fig. 2 may of course be realised using both hardware and software elements, and may comprise a disturbance signal generator, such as a random number generator, instead of having an input for noise.
• the data stream is preferably recorded on a recording medium.
• a recording medium can be e.g. a Compact Disc, a DVD or a Mini Disc.
• Analog copies can be made on traditional magnetic tapes, for instance.
• Another suitable field of application for the present invention is video-on-demand (VOD) services.
• VOD video-on-demand
• the copyright holder, or someone authorised by the copyright holder transmits the data stream representing a movie, chosen by the user of the service, over the public telephone network or other transmission media, and the user is then able to watch the selected video in his or her home without having to go to a traditional video store.
• the data stream preparing apparatus is preferably used to sign the material by inserting a suitable identification code, and to insert a suitable amount of noise for the purpose of hiding the sign. Any recording performed by the VOD-user will then contain both the sign and the obscuring noise.
• the advantage of the proposed method and means is that an attacker will find plenty of discrepancies between different copies independent of how these copies are obtained. It would be difficult to correct all such discrepancies and the attacker may in no way feel confident that no source of the original material can not be traced.
• the level of protection could be increased by using the described method layered. Different distribution networks could be given different copies protected by the described method which in turn would be protected in the distribution process before reaching the end-customers. This will protect the original material if the attacker is able to obtain a master copy.

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Cited By (5)

Citations (3)

• 1999
  • 1999-09-24 SE SE9903461A patent/SE9903461L/ not_active Application Discontinuation
• 2000
  • 2000-09-20 WO PCT/SE2000/001835 patent/WO2001022406A1/en active Application Filing
  • 2000-09-20 AU AU78191/00A patent/AU7819100A/en not_active Abandoned

Patent Citations (3)

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