JP2986476B2 - Recording system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording system for encrypting and recording information and enabling the information to be reproduced only by a specific reproducing device.

2. Description of the Related Art It has been conventionally known to encrypt and transmit / receive information (video / audio / data).
There are information that you want to keep confidential and information that you only show to the person who paid. If it is desired to keep the secret, the information may be recorded in an encrypted state, but in this case, it is not desirable that any information can be decrypted by any encryption / decryption device. In the case of a fee, it is not desirable that the decrypted information is copied.

The present invention is a technique relating to a recording system that solves these problems.

Problems to be Solved by the Invention In the conventional recording system, there is a problem that any decryption device can decrypt the data even if the data is recorded in an encrypted state.

Further, when decrypting and recording the encrypted information, for example, the secret number of the device is encoded and recorded at the same time, but there is a problem that copying of the decrypted information cannot be prevented.

Therefore, the present invention solves such a conventional problem, and provides a recording system capable of decrypting recorded information only with a specific encryption / decryption device and preventing the decrypted information from being copied. With the goal.

To solve means this purpose in order to solve the problems, the present invention encrypts a unique key K _i to each of the decryption device key K _t or K _x for decrypting encrypted information It is characterized in that it is recorded together with the encrypted information. Therefore, remains even when the recorded information reproduced as it is encrypted, can only be decrypted by the decryption device with a key K _i used for recording.

According to the action to the present invention, generally because changes a key K _t or K _x is the lapse of time is different from the time the key K _t or K _x decryption apparatus has recorded the information signal during reproduction And encrypted information such as scrambled video and audio cannot be restored when reproduced, but according to the recording system of the present invention, when the recorded information signal is reproduced, Was obtained, so I decrypted this Further to obtain a K _x by decrypting with the key K _i, it is possible to decrypt the scrambled information signal reproduced (descrambled).

FIG. 1 shows an embodiment of the present invention. In the figure, parts 1 to 5 are recording / reproducing units (for example, VTR), and parts 11 to 21 and 29 show a part of a pay decoder including a decryption function and an encryption function.

In FIG. 1, input buffer circuits 1 and 3, a video recording head 4, and an audio recording head 5 are circuits and the like common to a corresponding portion of a normal VTR. Further, the data extraction circuit 14, the encryption / decryption circuit 15, and the key _Kt memory 16 are circuits that are functionally the same as the corresponding parts of the pay decoder for pay broadcasting (for example, Video Cipher II, BMAC, etc.) that is already in practical use. It is.

First, an outline of the entire encryption system which is the basis of the recording system of the present invention will be described with reference to FIGS.
Here, it is assumed that scrambling a video signal and an audio signal by the function f (K _t) uniquely determined by the key K _t that varies over time. When transmitting a key K _t from the delivery side to the reception side, since there is a risk of eavesdropping is intact, is encrypted with a different key K _i. The key K _i is also assigned ones separately one by one terminal, allocates one key together several cars may also use a common key to all terminals. Such a multilayer structure of the key is described in, for example, "Research on Data Protection and Encryption", supervised by Shin Ichimatsu, page 63, FIG. During the key K _t and K _i, may be used key K _x is updated by a period longer than another key K _t. This is also shown in the same document. FIG. 3 shows an example.

Here, in order to simplify the description, the case of FIG. 2 will be described. As a broadcasting format, consider a system adopted by a broadcasting satellite BS2 that can transmit a control signal such as a key as a digital signal. In this method, since audio is transmitted as a digital signal, encryption (scramble) can be performed by adding a PN signal to the audio data. Therefore, the initial value of the PN signal i.e. key K _t becomes, which can decrypt (descrambled) knowing. This key encrypts K _t the key K _i (scrambled) to feed, may be decrypted by the key K _i in the receiving side. The video signal is encrypted (scrambled) by line rotation, and the cutting point in each line may be given by the PN signal, and a known technique can be used for this.

Now, in Figure 1, P ₁ is the input terminal of the reception signal at the reception side, for example the FM detection composite video output signal of the BS tuner can be input as is. 11 is an input buffer circuit, 12
Is a separation circuit that separates a 5.73 MHz audio carrier component and a video signal component, and 13 is a 2.048 Mbps demodulating a 5.73 MHz QPSK signal.
Is a demodulation circuit that obtains a digital signal of 14 is a sampling circuit that extracts control signal data other than audio data from the output of the QPSK demodulation circuit 13, 15 is a decryption circuit that decrypts an encrypted key _{Kt and} other signals from the control signal data, and 16 is a decryption circuit. a memory a for storing a key K _t in the output of the circuit 15.
Needless to say, a memory for storing a control signal other than the addition to the key K _t of the memory A16 is separately.

On the other hand, reference numeral 17 denotes a modulation circuit for amplitude-modulating a continuous carrier of 4.5 MHz with audio data of 2.048 Mbps. The modulation circuit 17 mixes the modulated audio output of the modulation circuit 17 with the video signal component output of the separation circuit 12.
It was mixed with 18 outputs from the output terminal P _2. Therefore, the output signal of the output terminal P ₂ becomes as similar to an NTSC television signal of the terrestrial television broadcasting, so that contains audio data signals of the AM-modulated 4.5 MHz.

This signal is recorded on the tape by the video recording head 4 via the input buffer circuit 1 of the VTR. In this case, it goes without saying that the video recording head 4 can record up to a high frequency of 4.5 MHz or more. If the recording band of the VTR is narrow, the audio data signal may be recorded in baseband.However, to scramble the baseband audio data signal and record it, an audio scrambling circuit is required on the pay decoder side. become. Since this is not the subject of the present invention, it is assumed here that the VTR can record up to 4.5 MHz.

On the other hand, the terminal-specific key K _i from the memory 29 (here the key K _t stored in the memory 16 is an encryption circuit 19, a key K _i to each end
Are different) and the output buffer circuit 20
Output from the output terminal P ₃ via. The encryption circuit 19 and the output buffer circuit 20 each have a buffer memory inside.

Now, the fourth recording start control circuit of the VTR at time t ₀ shown in FIG. 2
When the recording start is instructed, the control signal of φ ₀ is changed to 1, 3, 4, 5
And the output signals from the output terminals P ₂ and P _{3 of} the pay decoder are recorded on the same tape. Then, by operating the changeover switch 22 at time t ₁ a fee decoder side, R / W
The control circuit 21 a control signal from _{φ 1 (φ 11), φ} 2 (φ 12) are output, the encryption circuit 19 reads out the key K _t from the memory 16
Input to and encrypted with key K _i encrypted circuit 19 To the output buffer circuit 20 and write it to the buffer memory. This action ends between t ₁ ~t _2, followed by t ₂ ~t ₃
Between the output buffer circuit 20 and its low speed of 1200 bps Reading, from the output terminal P _3. The format of the signal is the same as that of the output extracted by the data extraction circuit 14, and one packet is 272 bits. Here, from the output buffer circuit 20 If the data is read out by phase encoding at 1200 bps, 272 bits of data can be output in about 0.23 seconds. This is recorded on the audio track by the audio recording head via the input buffer circuit 3 of the VTR. The recording band of the VTR audio track is 5 KHz or more, and extends to a frequency higher than the highest frequency component of an output signal obtained by phase-encoding data read at 1200 bps, so that there is no recording problem. In this way, the audio track of the VTR tape When recording, a case of first recorded only during only as φ ₂ t ₂ ~t ₃ 1 times, t at regular intervals as φ _{12 n2} ~t _n3
There is a method of recording repeatedly between the two, but either may be used. Signal phi ₁ or phi ₁₁ of the recording control is the R / W control circuit 2
It is formed by 1 and switched by the setting of the changeover switch 22.

By configuring as described above, it was recorded by the video recording head 4 video signal recording control signal phi ₀ of FIG. 4 is encrypted between the high level (including the audio code signal) to the VTR,
And key K _t be encrypted Can be recorded on the audio track of the VTR by the audio recording head 5. In this case, an existing VTR can be used as the VTR of the recording / reproducing unit. Note that outputs the output of the input buffer circuit 11 without using the modulation circuit 17 if wider recording bandwidth of the video signal directly to the output terminal P ₂ of the VTR, it is also possible to record directly transmitted to the video recording head 4 is there.

Next, reproduction of the video / audio signal and the key thus recorded will be described with reference to FIG. As described in FIG. 4, only the t ₂ ~t ₃ of beginning of the reproduction signal May be recorded, or may be recorded repeatedly from t _{n2 to} t _n3 , but both operate in the same way. First, when the reproduction start is controlled by the reproduction start control circuit 10 of the recording / reproduction unit, the audio reproduction head 7 encrypts the data from the audio track. Play the phases encoded signals, via the output buffer circuit 9 to the input terminal P ₅ paid decoder. The output signal is phase decoded by the input buffer circuit 27.
272 bit digital signal of 1200bps Return to The output of the input buffer circuit 27 The get key K _t is decrypted by device-specific key K _i stored in the memory 29 (decoding). The key K _t K _t memory B30
Write to.

On the other hand, and supplies this time issues a reproduction instruction signal from the VTR reproduction instruction circuit 31 K _t memory A16, a selector 26, K _t memory B30, the descrambling section 32. This allows the _Kt memory
A16 becomes its output high impedance, becomes a holding state, the other K _t memory B30 is an active state. Also,
At this time, the selector 26 adds the output of the audio detection circuit 25 to the data processing circuit 14 instead of the output of the QPSK demodulation circuit 13. Therefore, the output of the audio detection circuit 25 of the same format as the output of the QPSK demodulation circuit 13 is added to the data processing circuit 14. The data processing circuit 14 processes the output of the QPSK demodulation circuit 13 and the output of the audio detection circuit 25 in the same manner. Then, the encryption / decryption circuit 15 decrypts the encryption of a part of the control signal in the data. The 15 operations will be described later. Key being output from encryption / decryption circuit 15
Information other than the K _t tell to descramble processing unit 32.

Performs decryption of a portion of the output of the descrambling processing unit 32 the data sampling circuit 14 using the key K _t in (portion not decoded by the decryption circuit 15), to obtain the necessary information about decoding (descrambling) , And descrambles the reproduced signal based on the information. Decoding the audio data signal (descramble) generates a PN sequence by applying a predetermined PN initial value or key K _t at the beginning of the frame period of the audio data, the audio data outputted from the data processing unit 14 and the PN value This is done by adding to the signal.

For video signals, the cut position of the line rotation during encryption specified in PN value, specified in the example the initial value of the key K _t Sokuchi PN the 22nd line of cut position, hereinafter, 23, 24 …… 1 at the position indicated by the PN sequence up to line 262
Cut and rotate the video signal of the line. At this time, the same line in every field or every frame is cut at the same position. If the waveform of a certain line video signal before the line rotation is as shown in FIG. 8A, the waveform encrypted by cutting and rotating at the position indicated by the predetermined PN value is shown in FIG. B
It will be something like Therefore, the initial of PN by its key K _t
If the value can be determined, it is easy to decrypt the encrypted video signal of FIG.

Here, the key K _t used for decoding (descrambling) of 1
If it is assumed that the key _Kt is changed on a weekly basis, the key _Kt is changed one week later even if the key is changed from a VTR using the pay decoder used for reception and recording as described above. the key K _t of K _t memory A16 is different from that at the time of recording. Therefore, in such a case, K _t
You need to get Also, as mentioned above, since the encrypted using the key K _i key K _t at the time of recording, to be used fee decoder other than toll decoder used at the time of recording does not have the key K _i The key _Kt can no longer be obtained, and it is not possible to descramble the reproduced signal.

Incidentally, when the key K _t is found that not changed, without using the output of the K _t memory B30 during playback in the configuration of FIG. 5, K _t de using the output of the memory A16 scrambler 32 by modifying the reproduced signal so as to descramble in, until the key K _t is next changed without using the K _t decrypted from the reproduction signal, i.e., an even reproduced signal without using a K _i It becomes possible to descramble. That is, a fee decoder which has no inherently key K _i, as long as it can be taken out K _t from the transmission signal, it is possible to reproduce the signal recorded encrypted with key K _i. That is, substantial pirate viewing is possible. To prevent such things, it is relatively changed in a short period of time the key K _t, and, by the key K _t read from the K _t memory A16 when VTR playback instruction is in paid decoder of FIG. 5 By making this switching part non-modifiable so that it is not easy to descramble,
It is possible to prevent only recording and reproduction by the same pay decoder except for personal recording and reproduction, and it is possible to prevent illegal duplication tape creation. FIG. 9 shows an example of such a configuration. The VTR playback instruction circuit 31 is a switch 3S and a memory 3 for holding its input.
Constituted by a 1M, the memory 31M and a key K _t memory A16, key
By either resin molding K _t memory B30 and sealed in one package to integrate the selector 30, the retrofit switching so as to use a key K _t extracted from the received Shinsuke during VTR playback physically blocking Can be prevented.

Next, the specific contents of the encryption key K _t as described above (scrambled), the operation of the decrypting circuit 15, supplementary explanation with reference to FIGS. 6 and 7. Here, the update cycle of the key K _t and once a week, shall be carried out at night. Since the power of pay decoder terminal can not update the K _t memory A16 of K _t in the pay decoder is disconnected, by encrypting the key K _t the key K _i at midnight every day just in case each terminal It shall be sent to the paid decoder. Suppose the QP of the audio data signal
Shall send various data by using the SK-modulated signal, it is assumed to use the 500K bit in the per 2.048M bits for delivery key K _t. Further, one terminal Atari key K _t is 32 bits and the address and 24 bits, it is necessary 56 bits per terminal (see Figure 7). One packet to be transmitted is 288 bits including the header as shown in FIG. A packet of various control information identification signal 1 is attached, B is a packet for a control signal including K _t are assigned the認別signal 2. 27
If two bits are configured by encoding using the error correction method based on the BEST method used for teletext, the data will be 190 bits out of 272 bits. Therefore, if the terminal has 56 bits, 168-bit data for three terminals can be transmitted in one packet. 500K bits ÷ 288 bits ≒ 173
6 is the number of terminals that can be accessed every second, and if the address is composed of 24 bits, the number that can be specified is about 16.78 million terminals, so all terminals are accessed in 16,780,000 ÷ 1736 ≒ 0.966 million seconds, that is, about 2.7 hours, and the key K _t Can be delivered. Therefore, for example, it delivers the Monday morning 2:00 5 1:00 Kaikagi K _t, the method such as each case individually corresponding is selected in accordance with the request from the terminal side after.

When receiving the data by QPSK modulation signal format Fig. 6 B (packet), that the identification signal in the decryption signal 15 has been sent a key K _t to identify that it is a (2) identify, which decrypts the key K _i with self decrypts the encrypted key K _t that matches the terminal address again with the key K _i. That is, since the key _Kt is doubly encrypted, the key _Kt is doubly decrypted. Only key K _t are encrypted address is also a method of a method which does not encrypt the key K _t keep encrypted with other K _i '. (K _i ′ is a key other than K _i that differs for each terminal).

On the other hand, when a signal in the signal format of FIG. 6A is received,
Control information decrypts using key K _t the encryption circuit 15 to obtain information necessary for decoding (descrambling).

The above is a case where the key structure is double as shown in FIG.
If three layers are used as shown in FIG. 3, the safety is further improved. In this case, the operation is the same, except that the key _Kx is stored in the memories 16 and 30. In this case, key K _t is changed per minute or per second unit, key K _x per week, are changed on a monthly or yearly basis. Since the key _Kt is included in the output of the QPSK demodulation circuit 13 in FIG. 1, it is recorded together with the audio data signal and reproduced together with the audio data signal. In this case, control information of FIG. 6 A is encrypted with the key K _x, key K _t That predetermined PN early in the control signal in FIG. 6 B obtained by decoding the key K _x Contains a value. The descramble processing section 32 in FIG. 5 decodes (descrambles) the video signal and the audio data signal based on the PN initial value.

As described above, according to the present invention, an encrypted video signal and a key updated with the passage of time are encrypted by a unique key and recorded on the same recording medium by a VTR or the like. Therefore, it can be reproduced and decrypted only by the decryption device having the unique key used for the recording.
Therefore, even if a recording medium such as a VTR tape recorded illegally is copied, it cannot be reproduced and decrypted (descrambled) unless a decryption device such as a pay decoder used for the recording is used. Unauthorized copying can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a recording portion of a recording system according to an embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing a basic principle of encryption and decryption, and FIG. FIG. 5 is a block diagram showing a reproducing portion of the recording system, and FIGS.
FIG. 8 is a waveform diagram showing an encrypted signal, and FIG. 9 is a block diagram showing a main part of a recording system according to another embodiment of the present invention. 4 ... Video recording head, 5 ... Audio recording head, 13 ...
QPSK demodulator, 14 ...... data sampling circuit, 15 ...... decrypting circuit, 16 ...... K _t memory A, 19 ...... encryption circuit, 25 ......
Voice detection circuit, 26 ... Selector, 28 ... Decoding circuit, 29
… _Ki memory, 30… _Kt memory B, 32… Descramble processing unit.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hisashika Sato 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-60-183842 (JP, A) -44873 (JP, A) JP-A-59-165585 (JP, A)

Claims (4)

(57) [Claims] 1. A key Kx encrypted by a key Ki given to each receiving terminal is recorded at least in the first part of the recording, and thereafter, the update period is shorter than that of the Kx encrypted by the Kx. A recording system for recording a key Kt and a signal including at least a video signal encrypted by the Kt. 2. A key Kt encrypted by the Kx and having a shorter update period than the Kx is recorded at least once before a signal including at least a video signal encrypted by the Kt. The recording system according to claim 1, wherein 3. The recording system according to claim 1, wherein the key Kt encrypted with the Kx and having a shorter update cycle than the Kx is recorded together with the audio data. 4. A key Kt encrypted by the Kx and having a shorter update cycle than the Kx is recorded every time the Kt is updated. Recording system.