JPH0241091A - Signal recorder - Google Patents

Abstract

PURPOSE:To disable interception even if a reproducing signal is illegally copied by using a specific key at a charged decoder so as to encipher a decoding key and multiplexing it during the horizontal or vertical blanking period. CONSTITUTION:A key Kt in a Kt memory A11 is enciphered by using a specific key Ki at an enciphering device 12 to generate an enciphering key EKi (Kt) and it is stored in a buffer memory 3. The content of the memory 3 is read for a prescribed period and it is superimposed onto the nH-th TV signal. A mixing circuit 4 eliminates the nH-th scrambled video signal, the EKi (Kt) signal is superimposed and it is recorded on a tape by a recording head section 5. At reproduction, a readout head section 6 reads a recording signal, a decoding circuit 14 uses a key Ki specific to the charged decoder so as to decode the signal, the key Kt is extracted and written in a Kt memory B17. Thus, other charged decoder cannot descramble the signal, then illegal copy is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a signal recording device for recording scrambled video signals of pay television broadcasting, and in particular to a signal recording device for recording a scrambled video signal for pay television broadcasting. The present invention relates to a signal recording device capable of reading and recording data from a decoder.

BACKGROUND OF THE INVENTION With the spread of recording devices such as VTRs, it has become common to record television broadcast signals, and even paid broadcasts such as CATV can now be freely recorded.

In such 0ATV pay broadcasting, the signal is encrypted and broadcast, and only those who have a specific decoder can decode and view the signal.

When recording a pay television signal, either record the encrypted (scrambled) television signal as it is, or first decode (descramble) it and make it into a normal video signal before recording. It was one of two things.

Problem to be Solved by the Invention However, when such an encrypted pay broadcast signal is descrambled and recorded, it is no longer a normal video signal and the tape cannot be freely played back. Unless unauthorized copying can be prevented, paid broadcasting will lose its meaning.

On the other hand, if the scrambled data is recorded, if the decryption key is changed over time (for example, on the first day of the first week of January 2015), it will no longer be possible to decipher it. If the decryption key is not changed, any paid decoder that holds the decryption key will be able to play and descramble the tape for viewing. . Therefore, in this case as well, the tape on which the scrambled television signal is recorded can be illegally copied and viewed in secret, rendering paid broadcasting meaningless.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a signal recording device that eliminates these conventional problems and prevents illegal copying and unauthorized viewing.

Means for Solving the Problems In order to achieve the object, the present invention provides at least an apparatus for recording and reproducing video signals and audio signals of a television signal, in which a decoder for decoding a scrambled television signal and means for outputting a drive signal for reading out a decryption key Kt encrypted using a key Ki specific to the decoder;
means for multiplexing Kt into a recordable portion in or near the horizontal or vertical retrace period of a television signal, extracting an encrypted decryption key Kt from the playback signal, and sending the playback signal to a decoder together with a control signal. It is characterized by comprising a supplying means.

Effects With this configuration, each decoder records the encrypted decryption key Kt using a unique key Ki, so that it can be played back by a decoder other than the decoder that has the key Ki. and, moreover,
Such recording can be performed by multiplexing the recording signal into a recording signal on the recording apparatus side independently of the decoder.

Embodiment An embodiment of the present invention is shown in FIG. In the figure, parts 1 to 9 are recording and reproducing devices (for example, VTR), and parts 11 to 16 are
The part indicates a part of the paid decoder that includes a decryption function and an encryption function.

In FIG. 1, synchronous separation circuit 1. Recording head5. The reproducing head 6 and other parts not shown are common circuits with the corresponding parts of a normal VTR. In addition, parts not shown in the pay decoder, such as a data extraction circuit and an encryption/decryption circuit, are used for pay broadcasts that have already been put into practical use (for example, video
This circuit is functionally the same as the corresponding part of the paid decoder of C1pharll, BMAC, etc.).

First, an overview of the entire encryption system that is the basis of the system of the present invention will be explained with reference to FIGS. 2 and 3. Here, it is assumed that the video signal and the audio signal are scrambled using a function f(Kt) that is uniquely determined by a key Kt that changes over time. When transmitting the key Kt from the sending side to the receiving side, it is encrypted using another key Ki since there is a risk that it may be intercepted in its original form. A different key Ki is assigned to each terminal. Such a multi-layered structure of keys is described, for example, in Figure 1-27, page 63 of "Research on Data Protection and Encryption" edited by - Denshin. Another key Kx that is updated at a longer cycle than the key Kt may be used between the keys Kt and Ki. This is also shown in the same document. Figure 3 is an example.

Here, in order to simplify the explanation, the case shown in FIG. 2 will be explained. As a broadcasting format, consider the method adopted by the broadcasting satellite BS2, which is capable of transmitting control signals such as keys as digital signals. Since this method transmits audio as a digital signal, it can be encrypted (scrambled) by adding a PN signal to the audio data. Therefore, if the initial value of the PN signal is the key Kt, it can be decrypted (descrambled). This key Kt may be encrypted (scrambled) with the key Ki, sent, and decrypted with the key Ki on the receiving side. The video signal may be encrypted (scrambled) by line rotation, and the cutting point on each line may be given using the PN signal, and any known technique can be used for this purpose.

Now, in FIG. 1, a received signal (for example, an FM detection composite video output signal of a BS tuner) is input as is to the paid decoder. From the signal, a 5.73 MH2 audio carrier wave component and a video signal component are separated, and a 5.73 MH2 QPSK signal is demodulated to obtain a 2.048 Mbps digital signal. Control signal data other than audio data is extracted from the output of the QPSK demodulation circuit, decrypts the encrypted key Kt and other signals from the control signal data, and stores the decrypted key Kt in the Kt memory 11. . It goes without saying that there is a separate memory in addition to the memory 11 that stores control signals other than the key Kt.

In the following explanation, it is assumed that Kt changes every week, and the terminal side decrypts the signal shown in FIG. 4B once every week using a unique key Ki. For example, the key Kt is delivered every day from Monday to Friday, and the Kt memory 11 shown in Fig. 1 has a capacity of two Kts, and the key Kt in the terminal is changed every Sunday at midnight. , switches to that week's key Kt. Now, K
The key Kt for that week (hereinafter referred to as Kt) is stored in the t memory 11.
is stored in memory. On the other hand, on the right side of the dotted chain line in FIG. 1 is a VTR. A scrambled video signal is input to Pl. For simplicity, it is assumed that the audio is descrambled and recorded as left and right baseband audio signals.

It is assumed that the vertical and horizontal synchronizing signal portions of this video signal are not scrambled, and the other portions are scrambled by so-called line rotation.

The input to terminal P1 is separated by synchronous separation circuit 1 to obtain H pulse and V pulse. As shown in FIG. 6, when a recording instruction pulse is supplied from the recording instruction circuit 9 to the R/W control circuit 2 at time t1, the R/W control circuit A read clock φ3 starting from 1 and / is supplied from 2 to the read control circuit 13 of the decoder. On the other hand, a control pulse φ2 is supplied from tl to the readout control circuit 13, and the contents Kt of the Kt memory 11 are encrypted by the encoder 12 using a unique key Ki, resulting in an encrypted key signal EKi(
Kt) is made. 1, / to ]KKi( in the encoder 12)
Kt) is read out and stored in the buffer memory 3.

The contents of buffer memory 3 are sent to clock φ4 between 12 and 13.
The second part of the television signal is read as shown in Fig.
Superimposed on 2H. The mixing circuit 4 removes the 22nd H video signal scrambled by line rotation and superimposes the EK signal (Kt) of B in FIG. This is recorded on the tape by the recording head section 6. If the high-frequency characteristics of the tape are poor, there is no problem even if 288 bits are divided into 2H and recorded.

Signals related to other scramble contents are used during the vertical retrace period (
VBI), for example, the 20th H (or the 20th H and the 21st
Assume that 288 bits are superimposed on the H-th data (total of 288 bits) as shown in FIG. As a result, the signal of FIG. 4B is recorded on the tape of the VTR in such a manner that the signal shown in FIG.

Next, the case of reproducing the recording signal φ5 will be explained.

The read head unit 6 reads the recording signal φ5 from the tape,
The signal is transmitted to the signal separation circuit 7. The signal separation circuit 7 detects the header in the signal shown in Fig. 6 (the header part of Fig. 4 and B),
The control signal forming circuit 8 forms the control signal φ6, and the control signal φ6
is supplied to the input/output control section 16 of the paid decoder. A clock is sent from the control section 16 to the Ki (Kt) decoder 14 and input buffer memory 15. That is, 288 bits (corresponding to the person in FIG. 4) from t2 to t5 in FIG. 6 are written to the memory of the input buffer memory 15, and then the decoder 14
Transfers the contents of the input buffer memory 16 to the paid decoder, decrypts it with a key Ki specific to the paid decoder, and extracts the key Kt.
Write to Kt memory B17.

When inputting the VTR output to a paid decoder, the paid decoder is provided with a changeover switch, and by changing the switch, it is possible to use the key Kt in the j5Kt memory A11 or the key Kt in the Kt memo 17 B 17. Switch. Therefore, when descrambling the playback output of a VTR, the middle key Kt of the Kt memory B1 end, that is, the encryption key Kt used to convert the signal recorded on the VTR tape into 8 crumples, is used. can be converted into This is only possible with the paid decoder used when recording.

- Until the sent key Kt is changed, it is possible to play back scrambled signals recorded with another paid decoder by changing the internal wiring of the paid decoder. However, this can be prevented by making it impossible to change the wiring by packaging and molding the Kt memory 11, the Kt memory B 17, and their switching parts on the paid decoder side.

The above explanation is based on the case where the multilayer structure of the key is two layers as shown in FIG. 2, but it may be three layers as shown in FIG. 3. In the case of three layers, the key Kx instead of the key Kt is encrypted and recorded with the key Ki,
Play the Kt memory A11 and Kt memory B1 in Figure 1.
7 stores the key KX.

Effects of the Invention As described above, according to the present invention, by shortening the key update cycle that changes over time, a scrambled signal recorded using one paid decoder cannot be descrambled by another paid decoder. This prevents illegal copying.

Also, if you physically protect it with the internal structure of a paid decoder,
Even before the key changes, scrambled signals recorded with other paid decoders cannot be descrambled. This is because the key Kt cannot be obtained even if the signal obtained by playback is decrypted using the key Ki.On the other hand, with paid decoders, the structure allows only the key obtained from the playback output to be used during playback. This is because the structure can be configured in such a way that it cannot be changed by outsiders.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a signal recording device according to an embodiment of the present invention, and FIGS. 2 and 3 show its encryption. FIGS. 4 and 5 are block diagrams showing the principle of decoding. FIG. 6 is a waveform diagram showing the operation. 1... Synchronization separation circuit, 2... R/W control circuit, 3... Buffer memory, 4...
・Mixing circuit, 6... Recording head section, e...
・Reading head section, 7... Signal separation circuit, 8...
... Control signal forming circuit, 9 ... Recording instruction circuit, 11 ... Kt memory person, 12 ... Encryptor, 13 ... Read control circuit, 14. ...Decode circuit, 16...Input buffer memory, 16...
...Input/output control circuit, 17...Kt memo IJ
3゜Name of agent Patent attorney Shigetaka Awano and 1 other person
Name chart! Is there a concave diagram? f:3 +22HH-11111

Claims (1)

[Claims] A device for recording and reproducing at least a video signal and an audio signal of a television signal, which reads a decoding key Kt encrypted using a key Ki unique to the decoder from a decoder that decodes a scrambled television signal. means for outputting a drive signal for the reproduction signal; means for multiplexing the encrypted decryption key Kt into a recordable portion in or near the horizontal or vertical retrace period of the television signal; A signal recording device comprising means for extracting an encrypted decryption key Kt and supplying the reproduction signal to the decoder together with a control signal.