Copy protection method for digital data stored on a medium

Description of the invention

The present invention relates to a method for securing against copying digital data stored on a recording medium and a device for reproducing digital data stored on a recording medium.

A characteristic feature of digital data is that it can be copied without any appreciable loss of quality because the copying consists in sending a signal representing a sequence of 1s and 0s from the source to the recorder. The occurrence of errors that may occur during copying can be prevented by using error correction methods. Hence, if an information carrier comprises digital data, it is relatively very easy to record the contents of the information carrier on a recordable medium.

Various types and kinds of information carriers are used to memorize information, in all possible digital forms. Video and audio data can be stored in digital form, for example, on tapes, recordable or unrecordable optical discs (CD, CD-R, CD-RW, DVD, DVD-R, magneto-optical discs, etc., abbreviated as means compact disc, recordable CD, rewritable CD, universal video disc, recordable DVD).

In order to better protect the interests of the authors of the information stored or the producers of pre-recorded information carriers, it is desirable to limit the possibilities of free copying of digital data. There are currently many different mechanisms to protect your digital data from illegal copying.

The digital data can be encrypted in a known manner when it is stored on the information carrier. Encryption allows the use of digital data to be restricted to the holder of the decryption public (multi-access) or private (confidential) key. For example, encryption is used to protect data on DVD, optical discs used to store video data in digital form. Hence, the DVD player requires an appropriate key to decrypt the data read from the DVD.

One way to protect digital data from copying is to provide it with a watermark, that is, auxiliary data attached to the digital data. The watermark must be non-modifiable and indelible. The data playback is performed with a public key that identifies the watermark. The public key is a code known to the users, or to be more precise, it is contained in most media players. To copy watermarked digital data, a private key is required to put the watermark in the right place on the copy, and when this is not met, the copy becomes illegal and is watermarkless. The private key is in the possession of the author or producer of the watermarked information. Digital data copied without a watermark cannot be played without the watermark in the player as it cannot identify the watermark where it should be. Therefore, the watermark prevents copying without the private key. When a copy is required then the recording device must have this private key embedded in it.

The introduction of a watermark does not prevent the duplication of digital data via analog, ie duplication where first the conversion of the digital data into an analog signal is required and then the analog signal is treated as a copying source.

A known solution to prevent the duplication of a digital medium using the analog path, especially in the field of video and television, consists in distorting the analog signal in such a way that it can be used to display an image on the screen of a television set as an analog input to that receiver, but the same signal cannot be used to make copies on a VCR. More specifically, an electronic circuit is used that influences the picture timing parameters. The timing parameters are differently "seen" by a television set and a VCR. This solution does not prevent digital copying of digital data.

Another solution for limiting digital copying of digital data is to provide it with an information element to manage the generation of copies. Generally speaking, this information item carries an information item "Never copy" for data that do not have copying rights and an information item "copy" or "X copy number" if the data is a first generation or copy generation X number of the original. In this way, the recorder can determine using these information items whether the digital data to be copied has copying rights and prevent copying if it is prohibited for the 2nd or (X + 1) th generation respectively. The backup management information is updated with each copy made. Element manipulation

The duplication management information makes it vulnerable to tampering. The copy generation management information element is available in a clear text, i.e. in decrypted form, in one copying step. Manipulation also requires the appropriate equipment of the recording device. The copy generation management information element alone cannot prevent analogue duplication.

The object of the present invention is to find a solution for preventing digital copying in which no information element related to generating a copy is available in decrypted form.

Another object of the present invention is to find a solution in which no modification of the copy protection data is performed when a copy is possible.

A method for preventing the copying of digital data on a record carrier in which it is identified whether or not a watermark has been embedded in the digital data, according to the invention, is characterized in that it then identifies whether the digital data has been encrypted and provides a permission signal or a prohibition to copy signal and / or reproduction of digital data, depending on the identification or non-encryption of digital data, and watermarking of digital data.

Moreover, the method according to the invention is characterized in that it further identifies the type of the recording medium, and provides a signal to authorize or prohibit the copying and / or reproduction of digital data depending on the identification of the recordable or unrecordable type of the recording medium.

Moreover, the method according to the invention is characterized in that it further identifies whether the digital data is provided with a cryptographic signature, and then provides a signal to authorize or prohibit copying and / or reproducing the digital data depending on the identification or non-identification of the cryptographic signature accompanying the digital data.

The method according to the invention is characterized in that, furthermore, the type of the recording medium is identified, then it is identified whether the digital data is provided with a cryptographic signature, and then the digital copying authorization signal is provided, once the encryption of the digital data has been identified, the digital data watermark has been identified. , a non-recordable type of recording medium has been identified, and a cryptographic signature accompanying the digital data has been identified.

The method according to the invention is characterized in that it further provides a digital copying authorization signal when the encryption of the digital data has not been identified and the watermark of the digital data has not been identified.

The method according to the invention is characterized in that it further provides a digital data non-reproduction signal when no encryption of the digital data has been identified, and the watermark of the digital data has been identified.

The method according to the invention is characterized in that further identifying the type of the recording medium, and then providing a copy prohibition signal, when the encryption of the digital data has been identified, the watermark of the digital data has been identified, and the recordable type of the medium has been identified.

The method according to the invention is characterized in that it further identifies the type of the recording medium, then identifies whether the digital data is provided with a cryptographic signature, and then provides a digital copy prohibition signal, when digital data encryption has been identified, digital data watermark has been identified, a non-recordable type of medium has been identified and the cryptographic signature accompanying the digital data has not been identified.

The method according to the invention is characterized in that it further converts the digital data into analog signals and distorts the analog signals if a digital copy prohibition signal is provided.

The protection method according to the invention is characterized in that the digital copy prohibition signal comprises a signal for blocking the digital data output.

A device for reproducing digital data recorded on a recording medium comprising at least a digital output for providing signals representing the digital data at the time of reproducing the digital data, means for detecting a watermark of digital data and a recordable or non-recordable type of information carrier, according to the invention is characterized by: that it further comprises an analog output for providing analog signals representing the digital data at the time of reproducing the digital data, means for detecting the encryption of the digital data

PL 202 063 B1 and the cryptographic signature accompanying the digital data, a system for decrypting the digital data when encryption is detected, and a system for preventing the copying of digital data, receiving signals from the detection means and generating a copy permission signal or a copy prohibition signal depending on the signals received by means of detection, recording controls to block signals delivered to the digital output, when the write control means receive a copy prohibition signal, a security system, a system for preventing the received signals from being played back from the detection means and generating a reproduction prohibition signal when the encoding of the digital data has not been detected and the watermark of the digital data has been detected by the detection means, and the reproduction control means interrupting data playback or their output to the analog output, when the reproduction control means receives the reproduction prohibition signal from the security system.

Fig. 1 is a flowchart illustrating an embodiment of the invention, Figs. 2 to 5 are flowcharts illustrating aspects of the invention, Fig. 6 is a flowchart illustrating a digital / analog conversion in accordance with the invention. and Fig. 7 is a diagram illustrating an apparatus in accordance with the invention.

Fig. 1 shows a flowchart in which the digital data stored on the information carrier 1 is subject to first scrambling identification 2 so as to verify that the digital data is stored encrypted, then to a second watermark identification 3 to verify that the data is provided with encryption. the watermark. The first bifurcation 4 makes it possible to distinguish between cases where the encryption is identified 5 or not identified 6. The second separation 7 makes it possible to distinguish between cases where the watermark is identified 8, or is not identified 9. If cases 5 and 8 are truly verified, the first determination block 10 generates the first marker # 1.

The third identification 11 of the type of information carrier serves for example to check whether the information carrier is recordable or unrecordable. The type-related information item may be contained per se in the digital data, or as a result of measurements of the physical parameters of the information carrier 1, for example during installation in the information carrier 1 player. The third branch 12 distinguishes between cases where the type may be of a fixed type 13, for example a non-recordable information medium, such as an embossed optical disc or not 14. If case 13 is validly verified and the first flag # 1 was generated, then the second block the finding of 15 generates the second tag # 2.

The fourth cryptographic signature data identification 16 determines whether the digital data is cryptographically signed. The fourth branch 17 distinguishes between cases where there is 18 or 19 no cryptographic signature. If case 18 is valid verified, and the second flag # 2 was generated, then the third determination block 20 generates the third flag # 3.

In the event that the third flag # 3 is present, provision 21 is performed to enable digital copying 22 of the digital data.

In general, the flowchart of Fig. 1 shows how different criteria relating to digital data and also to digital data can lead to the granting of a digital copying license, and the idea is to only allow copying under certain conditions. For example, data should not be altered and therefore should be encrypted and watermarked. Moreover, the data should not be copied anymore. If the data is on a non-recordable disk, then a priori the data is on the original recording medium. Finally, the data should have a cryptographic signature. It indicates that the data can be copied. This is when the data receives authorization for digital copying. The data copying result will be identical to the original data, except that reference is made to the information medium which must be recordable. A new copy of the data from the recordable recording medium would be impossible since a second flag # 2 could not be generated after the third identification of 11. In particular, the third branch 12 would lead us to case 14.

Consider other examples of cases where, for example, the encryption or watermark of digital data cannot be identified. Typically, encryption and watermark occur simultaneously, and the absence of one is evidence of unauthorized manipulation of digital data. Therefore, it is simply necessary not only to prohibit the copying of digital data. You should also prevent their reproduction.

PL 202 063 B1

Fig. 2 shows two example cases where the encryption and watermark are not simultaneously identified. The exemplary example predicts that the first branch 4 gives the case 6, i.e. the first scrambling identification is negative and the second branch 7 gives the case 8, i.e. there is a watermark. Then the second supply block 23 generates a prohibition of reproducing digital data 24. In practice, this would lead to an interruption of data reproduction. Another example case is that the first branch 4 gives case 5, i.e. the first encryption identification is positive and the second branch 1 gives the case 9, i.e. the watermark identification is negative. In the latter case, the second supply block 23 generates a digital data reproduction prohibition 24.

The method described above makes it possible to freely copy unprotected digital data, for example data without encryption and watermark. Figure 3 shows a flowchart where the first and second branches 4 and 7 give a case of negative identification of case 6 with respect to encryption and 9 with regard to watermarking, respectively. The third delivery block generates digital copying permission 22.

In the latter case, it does not matter whether the data is in a recordable or unrecordable medium. The lack of encryption and watermarking indicates the lowest level of data security.

In certain example instances, it must be possible to reproduce and use the data without copying it. This is especially the case when a purchase is made of an information medium containing digital data, the copying of which is prevented by the author or the producer. The same is the case when a recordable information medium containing legally copied data is played back. Such a case is illustrated using a flowchart in Fig. 4, wherein the fourth delivery block 26 checks whether the first flag # 1 has been delivered and whether a type identification case 14 other than the specified type has occurred before generating a copy prohibition 27. In practice, the player would have to employ a device to prevent duplication of digital data, for example by turning off the digital output of the player.

Another such case is illustrated using the flowchart in Fig. 5. If the second flag # 2 is identified and case 19 signals a fourth negative identification, which means that there is no cryptographic copy permitting, then the fifth delivery block 28 generates a copy prohibition. 27.

Of course, the fact that the cryptographic signature allowing copying has not been identified does not exclude the possibility of a specific non-copying cryptographic signature.

It has already been mentioned in the above description that the information medium 1 is used in a corresponding player. The digital data on the recording medium 1 can in some cases be transferred to the digital output of a player. In the case of a DVD player (optical disk for video / audio data), a digital output may be provided to output a signal representing the data to a DVD-R player / writer for copying, or to a computer for image processing. In general, the player may also be equipped with an analog output so that an analog signal representing the digital data can be sent to an analog input such as a television set.

In the flowchart of Fig. 6, it is indicated by a dashed arrow that the information carrier yields digital data 29. The processing 30 enables the digital data 29 to be converted into analog signals 31. The presence of a digital copying permission 22, together with any first, second, or third tag (# 1, # 2, # 3), or the presence of a digital copying prohibition 27, is detected at detection block 32 which, when appropriate, starts the block distorting 33 the analog signal so as to obtain distorted analog signals 34. For example, the analog signals are distorted such that they can be used to obtain a television picture, but cannot be copied with an analog input recorder.

Preferably, the output of the digital data player 35 is blocked in the presence of a digital copying prohibition 27.

Encryption of digital data on an information carrier is usually performed by the manufacturer.

The digital data, as well as the cryptographic signature that may be associated with it, is decrypted in the data player, but when the data is to be sent to the digital player's output, it is encrypted.

PL 202 063 B1

The digital data reproduction apparatus 42 shown in FIG. 7 includes a digital output 43 that provides signals representing the digital data at the time of reproducing the digital data of an information carrier. For example, output 43 may be via an IEEE 1394 standard bus. Analog output 44 provides analog signals representing the same digital data. The decryption system 45 enables the decryption of the digital data, if the latter is encrypted, but also the identification of the watermark and the cryptographic signature data. The decryption system makes it possible, for example, to carry out the identification 2, 3, 11 and 16 of the method shown in Fig. 1.

The security system, with respect to the duplication of digital data 46, uses the signals sent by the decryption system 45 and evaluates them by implementations of the indications 10, 15, and 20 of the method shown in Fig. 1, and provides, after determining the presence of the markers # 1, # 2 and # 3, copy permission signal.

The recording control portion 47 manages the digital data stream going to the digital output. This portion, when it obtains the copy enable signal from security system 46, may in particular start the stream.

The anti-copy system for digital data 46 may also function as an anti-reproduction system. By means of the signals received from the decryption system 45, the latter system generates a non-playback signal when the digital data is not encrypted but contains a watermark, or when the digital data is encrypted but has no watermark.

The reproduction control block 48 enables the reproduction of the digital data to be interrupted when it receives a prohibition signal from the reproduction security system 46.