KR100281044B1 - Method and Device of copy protect for Digital VCR - Google Patents

Abstract

The present invention relates to a VCR, and more particularly, to a digital VCR capable of preventing the illegal copying of a program tape to the maximum. The digital VCR of the present invention is a ROM for storing unique recognition data, an encoder for encoding a bit stream in which a broadcast signal received from an antenna or a corresponding device is modulated in transmission packet units, on a vertical axis and a horizontal axis, and an encoding. An encryption unit for encrypting the outputted bitstream signal by means of the recognition data stored in the ROM, a demodulator for demodulating the digital signal reproduced on the tape in a proper manner, and a synchronization signal and an ID signal from the digital signal demodulated in the demodulator. A detection unit for detecting a signal, an ID processing unit for disposing the digital signal demodulated by the ID signal in sync block units, and a decryption unit for decrypting and outputting the encryption of the digital signal arranged in sync block units by recognition data. Is characteristic.

Description

Copy protection device and method of digital VCR {Method and Device of copy protect for Digital VCR}

The present invention relates to a digital recording and reproducing apparatus, and more particularly, to a method and a device for copy protection of a digital recording and reproducing apparatus.

Recently, with the development of digital information processing technology, analog broadcasting such as terrestrial broadcasting and cable broadcasting has become digital broadcasting starting from digital satellite broadcasting. In line with such digital broadcasting, development of a digital VCR capable of recording in a digital manner instead of a conventional VHS analog home VCR is being promoted.

When playing a copy tape on a VHS analog VCR, the image quality is lower than when playing back the original tape. Nevertheless, videotape copying is not allowed in terms of copyright protection, so many videotape program makers have introduced copy protection technology to make copying impossible. The copy-protected tape is made so that the copy quality is significantly worse than the original, making it almost impossible for pirated users to watch the program.

Although the quality of digital VCRs is better than that of analog VCRs, the quality of the copy has almost the same characteristics as the original. Thus, if several original tapes are illegally copied and distributed on the market, the program maker may suffer enormous damage. In order to solve this problem, the digital VCR uses a method of recording a scrambled bitstream on a digital video tape as it is recorded, and descrambled with a smart card at the time of playback. have.

Figure 1 shows the configuration and operation principle of a conventional digital receiver for recording such a scrambled bitstream. First, the digital broadcast signal 11 'is received from the antenna 11. This digital broadcast signal is selected by the user in the tuner 12 only a broadcast signal corresponding to one channel. The selected broadcast signal is extracted by the link unit 13 through demodulation and forward error correction (hereinafter referred to as FEC: Forward Error Correction). Demodulation methods include Quadrature Phase Shift Keying (QPSK), Vertical SideBand (VSB), and Quadrature Amplitude Modulation (QAM). The demodulation method uses appropriate demodulation methods depending on the channel received at the receiver. For example, QPSK is used for satellite broadcasting, VSB is used for terrestrial broadcasting in the United States, and QAM is used for cable broadcasting. The FEC performs a function of correcting an error of a broadcast signal generated by noise mixed in a transmission channel.

The baseband signal 13 'extracted from this link unit is output in units of transmission packets of each broadcasting system. For example, in the case of MPEG broadcasting, a baseband signal is output in units of MPEG transmission packets. The baseband signal is first descrambled by the descrambler 15 by selecting only the program selected by the user in the program selector 14. This descrambler is a type of decoder that allows a registered user to watch a broadcast signal that is scrambled and sent in order to supply a program only to a receiver to whom a broadcaster has permission to receive.

At this time, the determination of the existence of the receiving authority is performed by the smart card 16. The baseband signal extracted from the link unit includes a program of a channel selected by the user. The baseband signal corresponding to the program is judged by the smart card to determine whether to receive the right, and if received, the descrambler is descrambled by the descrambler to the video decoder 17 and the audio decoder 18. Is approved. The descrambled program is output as a video signal and an audio signal for the user to watch through the screen and the speaker through the video decoder and the audio decoder.

In this conventional digital receiver, a method of recording a digital signal on the tape 30 using a digital recording device such as a digital VCR 20 is as follows. When the user presses the record button, the digital VCR records the baseband signal before descramble on tape. This baseband signal is a scrambled bitstream. The digital VCR records the scrambled signal and outputs it as it is during reproduction. For example, even when signals in the transmission packet unit are not input at a constant rate and are irregularly input, when recording, the time stamp at the time of inputting each packet is recorded at the same time as the packet, thereby inputting at the time of reproduction. It means to play at an irregular rate. The reproduced scrambled bitstream is input to the program selector, and outputted as a video and sound through a descrambler, a video decoder, and an audio decoder to reproduce the digital VCR.

A recording system of a conventional digital VCR will be described with reference to FIG. Conventional digital VCR recording systems include interfaces 21, memories 22 and 24, longitudinal and transverse encoders 23 and 25, Sync / ID 26 and recording modulator 27, and recording. The amplifier 28 is comprised. The interface 21 stores the received bitstream in the first recording memory 22 in units of sync blocks and converts it into a recording format of a digital VCR. The vertical axis encoder 23 encodes the bit stream of the sync block unit stored in the first recording memory 22 in the vertical axis direction and stores the bit stream in the second recording memory 24. The horizontal axis encoder 25 encodes the bitstream encoded in the vertical axis direction in the horizontal axis direction. The Sync / ID 26 adds a sync signal and an ID signal to the encoded bitstream so that the sync block corresponding to the encoded bitstream can be identified in the VCR during later playback. Finally, the recording modulator 27 modulates the bitstream that has undergone Sync / ID so that recording and reproducing is possible in the digital VCR, and the recording amplifier 28 amplifies the modulated bitstream to record on the tape.

A conventional digital VCR reproducing system has a reproducing amplifier 29, a demodulator 38, a sync detector 37, an ID processor 36, a horizontal axis and a vertical axis decoder as shown in FIG. (decoder) 33, 35, memories 32, 34, and an interface 31. As shown in FIG. The reproduction amplifier 29 amplifies the signal reproduced from the tape 30. This reproduced signal is a modulated and coded signal. The demodulator 38 demodulates this reproduced signal into a signal that the system can recognize. The sync signal detector 37 detects a sync signal Sync from the demodulated signal and divides the signal into sync blocks. In addition, the ID processing unit 36 detects the ID from the signals divided by the sync block unit so as to have the same position as when these signals were recorded. The horizontal axis decoder 35 decodes the signals passing through the ID processing unit in the horizontal axis direction and stores the decoded signals in the first reproducing memory 34. The vertical axis decoder 33 decodes the signal stored in the first reproducing memory 34 in the longitudinal axis direction, and stores the signal in the second reproducing memory 32. Output in the form of a stream.

A description of the conventional recording operation of the digital VCR will be described with reference to FIG. The bitstream input in the packet unit is stored in the first recording memory in the form as shown in Fig. 3A in the sync block 41 unit. The bitstream stored in the first recording memory is coded 42 in the longitudinal axis direction by the longitudinal axis encoder and stored in the second recording memory in the form as shown in Fig. 3B. The bitstream stored in the first recording memory is coded 43 in the horizontal axis direction by the horizontal axis encoder as shown in Fig. 3C, and the synchronization signal 44 and the ID signal 45 by Sync / ID as shown in Fig. 3D. ) Is added. The bitstream to which the synchronization signal and the ID signal are added is recorded on the tape through a recording modulator and a recording amplifier.

At the time of reproduction, the digital signal recorded on the tape is amplified by the reproduction amplifier section and demodulated by the demodulation section. As shown in Fig. 3D, the same bitstream as at the time of recording is output. At this time, in order to obtain a bitstream as shown in FIG. 3D, the synchronization signal detector must accurately detect the synchronization signal. If the synchronization signal is incorrectly detected, a completely different type of bitstream is output. In this case, the correct correct bitstream can be obtained by performing error correction on the vertical decoder.

When the synchronization signal is detected, the ID signal can also be extracted, so that each sync block is stored in the address of the corresponding first playback memory. In addition, even if the ID processing unit cannot find the synchronization signal due to an error, if it is decorated in the longitudinal direction, the original correct bitstream can be obtained.

If the correct bitstream is extracted and the sync signal and ID signal are retrieved correctly, each sync block is placed in the same position of the first playback memory as recorded by the horizontal axis decoder. The sync blocks arranged in the first playback memory are decoded in sync block units by the vertical axis decoder and stored in the second playback memory. The sync block stored in the second reproducing memory is converted into a bitstream of a packet unit through an interface and output. The signal passed through this interface is the same as the format of the bitstream input to the interface at the time of writing.

However, the conventional digital VCR has the following problems. First, even if a broadcast signal is recorded in a scrambled bitstream on the tape, the recorded broadcast signal can be played back as many times as possible in other VCRs. This is because the scrambled bitstream recorded on the tape used in each VCR is the same even if a predetermined broadcast program is recorded on different VCRs.

That is, since the bitstream input through the interface at the time of recording and the bitstream output through the interface at the time of recording are identical, the copy is identical to the original because the content recorded on the tape is constant regardless of the recording apparatus. Therefore, if an individual illegally copies and distributes the recorded scrambled bitstream, the original author may suffer enormous damage.

The present invention has been made to solve such a problem, and its purpose is to prevent distribution of copies and to protect the rights of copyright holders.

1 is a view showing the configuration and operation principle of a conventional digital receiver for recording a scrambled bitstream.

2 is a block diagram showing the configuration of a conventional digital VCR.

3A to 3D are models of a bitstream converted during a recording operation and a reproduction operation of a conventional digital VCR.

4 is a block diagram showing the configuration of the digital VCR of the present invention.

5A to 5F are models for modeling a bitstream converted during a recording operation and a reproduction operation of the digital VCR of the present invention.

6A and 6B are diagrams illustrating conversion rules of different digital signals.

7A to 7D are diagrams for modeling a bitstream converted when a tape recorded by a digital VCR of the present invention is played back by another VCR.

Explanation of symbols for main parts of the drawings

100: VCR 111, 141: interface

112: first recording memory 113: vertical axis encoder

114: second recording memory 115: horizontal axis encoder

116: encryption unit 117: Sync / ID

118: modulation section 120: recording amplifier

130: playback amplifier 142: second playback memory

143: vertical decoder 144: first playback memory

145: horizontal decoder 146: decryption unit

147: ID processing unit 148: Sync signal detector

149: demodulator 161: bit stream in sync block units

161 ': Symbol whose bit value is reduced 162: Vertical axis encoding

163: horizontal encoding 164: synchronization signal

165: ID signal 166: Symbol whose bit value is converted

167: miscorrected symbol 170: conversion rule recognition data

171: Decryption rule recognition data 172: Horizontal axis decoding

173: longitudinal decoding 200: tape

According to the present invention, after encoding a video signal, the video signal is encoded and recorded on the tape based on the recognition data, and after the video signal is played on the tape, the video signal is set based on the recognition data. It is characterized by decrypting and decrypting. That is, the present invention sets the encryption by the recognition data before the video signal is recorded on the tape, and decrypts the encryption before decoding after playing the video signal on the tape. The video signal can be reproduced.

As shown in FIG. 4, the present invention includes a ROM (Read Only Memocy) 150, an encoder 113, 115, an encryption forming unit 116, an encryption decrypting unit 146, a demodulating unit 149, The detector 148 and the ID processor 147 are configured. That is, in the present invention, the encryption unit 116, the decryption unit 146, and the ROM 150 are additionally installed in the conventional digital VCR shown in FIG. At this time, the ROM, the encryption unit and the decryption unit may be configured in one IC chip to prevent duplication.

ROM stores the recognition data. The recognition data corresponds to a conversion rule for encryption of a video signal when recording as an encryption key unique to each VCR, and corresponds to a decryption rule for decryption of a video signal to be reproduced during reproduction. Therefore, video signals recorded on other VCRs cannot be reproduced correctly because of conversion rules and decoding rules.

The encoder encodes a bitstream modulated by a transmission packet on a vertical axis and a horizontal axis. This bitstream is a modulated broadcast signal received from an antenna or a corresponding device. The encoder is constituted by a vertical axis encoder 113 and a horizontal axis encoder 115, and the configuration and operation thereof are the same as the conventional one, and thus description thereof is omitted.

The encryption unit 116 encrypts and outputs the bitstream encoded by the encoder according to the recognition data stored in the ROM. Since this recognition data is unique to the VCR, the encrypted bitstreams are different for each VCR. Since the Sync / ID, the recording modulator, the memories 112, 114, 142, and 144, the sync signal detector, and the ID processor are the same in structure and operation as the conventional one, the description thereof is omitted.

The demodulator 149 demodulates the digital signal reproduced on the tape 200 in an appropriate manner. This method is the same as the conventional one. The detector 148 detects a synchronization signal and an ID signal included in the digital signal demodulated by the demodulator. The digital signal demodulated by the ID signal is arranged in sync blocks.

The decryption unit decrypts and outputs the ciphers included in the digital signals arranged in sync block units by the recognition data stored in the ROM. If the digital signal is decoded with recognition data different from when recorded, it is not correctly decoded and reproduction is impossible.

The operation of the digital VCR of the present invention will be described with reference to the accompanying drawings, FIGS. 4, 5 and 6.

(Example)

The digital VCR of the present invention converts the output data that has passed through the horizontal axis encoder 115 at the time of recording, according to the unique recognition data by the cryptographic forming unit 116. For example, assume that there are n symbols (not shown) in the sync block 161. At this time, each symbol is unit information (data) consisting of a predetermined number of bits. The encryption unit 116 of the present invention converts the symbols of each sync block by changing the bit value corresponding to the recognition data. In the accompanying drawings, FIGS. 5A to 5F, a portion represented by '1' represents a symbol of a sync block whose bit value is changed. In FIG. 5E, the portion represented by 'e' represents a symbol having an error in the bit value.

If the recognition data specifies that the third bit value of the sync block is to be changed, the symbols of all the sync blocks input to the encryption unit are changed and output. Then, the output data passing through the horizontal axis encoder 115 has a completely different data value in the encryption unit 116.

The sync block may be converted in various ways, but in this embodiment, a method of sequentially converting symbols by allocating n + α bits is used. 5A is a bitstream input to a vertical encoder in sync block units. 5B shows a bitstream encoded 162 by way of the longitudinal coder. 5C shows bitstreams 162 and 163 encoded by the vertical axis and the horizontal axis through the vertical axis encoder and the horizontal axis encoder. FIG. 5D shows a bitstream in which the symbols of each sync block are encrypted and the sync signal 164 and the ID signal 165 are added through the vertical encoder, the horizontal encoder, the encryption generator, and the Sync / ID. The part represented by '1' in the symbol is an encrypted bit. The bitstream of FIG. 5D is recorded as a digital signal on the tape through the recording modulator 118 and the recording amplifier 120. FIG.

When the encrypted digital signal is reproduced on the tape, the digital signal is applied as a bitstream to the decryption unit 146 via the reproduction amplifier 130 and the demodulator 149. The bitstream applied to this decryption unit restores each symbol for which bit conversion has occurred due to the recognition data stored in the ROM. The bitstream composed of the reduced symbols 161 'is decoded into a bitstream containing the original video signal through a horizontal decoder and a vertical decoder. This bitstream is converted into a video signal in a packet unit via the interface 141. At this time, there may be a miscorrected symbol 167 in the bitstream of the digital signal reproduced on the tape, but this miscorrected symbol is corrected by the horizontal axis decoder and the vertical axis decoder.

If a tape recorded on another VCR is reproduced, it is as shown in Figs. 7A to 7D. Assume that the digital signal conversion rule 170 recorded on the tape is as shown in Fig. 6A, and the recognition data 171 of the VCR to reproduce the tape is as shown in Fig. 6B. At this time, the original bitstream recorded on the tape is as shown in Fig. 7A, and the bitstream of the video signal input to the decoder of the VCR to be played back contains errors due to this noise. The bitstream output from this decoder does not correctly reduce the symbol whose bit value is changed and appears as shown in Fig. 7C. Even if the video signals are decoded (172, 173) through the horizontal axis decoder and the vertical axis decoder, they are converted into an unknown video signal as shown in Fig. 7D. Therefore, if the recognition data is different, the video signal is not demodulated correctly.

Digital tape recorded through the VCR of the present invention cannot be distributed in copies. Because the VCR of the present invention has a ROM in which unique recognition data is stored, and the bit stream of the video signal is encrypted by the recognition data at the time of recording, the video signal is not reproduced correctly in a VCR in which the recognition data does not match. Because. Therefore, the digital tape produced through the VCR of the present invention provides the maximum protection of the rights of the copyright holder, and thus, the VCR of the present invention has the advantage of preventing illegal copying of the program tape and ensuring the maximum profit of the copyright holder.

Claims (7)

For digital VCRs; A memory for storing unique recognition data; An encoder for error correcting and encoding the input digital broadcast signal; An encryption unit for encrypting the bit stream output from the encoding unit based on the recognition data stored in the memory; A synchronization / ID unit for adding a synchronization signal and an ID signal to the output of the encryption unit; A recording unit for recording a digital signal obtained by modulating the output of the synchronization / ID unit on a recording medium; A demodulation section for demodulating a digital signal reproduced from the recording section; A detector for detecting a synchronization signal and an ID signal from the demodulated digital signal; An ID processor arranged to arrange the demodulated digital signal in sync block units based on the ID signal; And a decryption unit for decrypting and outputting the output of the ID processing unit based on the recognition data stored in the memory. The digital VCR of claim 1, wherein the memory is a PROM capable of storing recognition data only once. The digital VCR according to claim 1, wherein at least the identification data, the encryption unit, and the decryption unit are integrated in one IC chip. The apparatus of claim 1, wherein the encoder comprises: a vertical axis encoder for encoding the bitstream in a vertical axis direction; And a horizontal axis encoder for encoding the bitstream encoded in the vertical axis direction in the horizontal axis direction. A video signal recording method of a digital VCR; Encoding a video signal received from the outside; Encrypting the encoded video signal based on recognition data stored in a memory of a digital VCR; A video signal recording method for copy protection of a digital VCR comprising the step of adding a synchronization signal and an ID signal to the encrypted video signal. A video signal recording method of a digital VCR; Encoding a video signal received from the outside; Adding a synchronization signal and an ID signal to the encoded video signal; And encrypting the video signal to which the synchronization signal and the ID signal are added based on recognition data stored in a memory of the digital VCR. A video signal reproduction method of a digital VCR; Demodulating a digital signal reproduced from the tape; Detecting a synchronization signal and an ID signal from the demodulated digital signal; Disposing the digital signal in sync block units by an ID signal; Decrypting the encryption of the digital signals arranged in the sync block units based on the recognition data stored in the memory of the digital VCR; And decoding the decrypted digital signal.

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