JP2542584B2 - Subscription broadcasting system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a subscriber broadcasting system such as CATV that multiplexes with a broadcast signal to transmit time data. The encoder side updates the initial value of the encrypted data on the decoder side according to the change of the time data by using it as the data for decrypting the initial value of the encrypted data for scrambling given to the pay broadcast, thus making it difficult for snooping. The present invention relates to a subscription broadcasting system that is designed to improve

(Prior Art) Generally, in order to make a program reservation in a subscriber broadcasting system such as CATV, a clock circuit is provided on the receiver side, and the time data by this clock circuit is compared with the reserved program start time data set by the subscriber. This is done by using a comparator.

That is, the receiver sets the reserved time, the reserved program channel, and the like, and compares them with the clock circuit output data of the receiver to control the reception of the reserved program.

On the other hand, in pay broadcasting, scrambling is applied to the broadcast signal in order to prevent non-contracted subscribers who have not made a reservation from viewing the program. The contracted subscriber can obtain the key information for descrambling at the time of reception by sending an identification code unique to the subscriber at the time of notifying the broadcasting station of the reservation time and the like.

FIG. 8 shows a conventional example of a subscription broadcasting system having a program reservation function. In the figure, only the subscriber receiving terminal side is shown.
Broadcast signals, such as video signals and audio signals, are input to the terminal 116 via an antenna or a cable. In the case of pay broadcasting, this broadcast signal is subjected to various scrambling processes, and the signal may be an analog signal or a digital signal, but the control signal for descrambling is superposed on the broadcast signal in some form.

Tuning for channel selection for the received broadcast signal is performed by setting the frequency division ratio of the PLL circuit 103. In this case, the frequency division ratio can be obtained by referring to the ROM 105 for the data corresponding to the channel data decoded by the decoder 104. The received broadcast signal at this time is subjected to a predetermined demodulation operation in the demodulation circuit 101 and further amplified by the amplification circuit 102.
Is amplified by and output from the output terminal 117.

On the other hand, for program reservation, the user selects a channel to be reserved by using the switch 115. The switch 115 is used for other than channel selection at the time of program reservation channel.
It has functions such as direct selection of program channels, set input of reserved time, and display switching between reserved time and current time.

In the case of directly selecting a program, the switch 115 inputs the data of the reserved program channel to the switch data input circuit 113. At this time, switch data input circuit 1
The output of 13 is applied to the switch data processing circuit 112, and the channel data is applied to the decoder 104 via the changeover switch 106. The channel data added to the decoder 104 is converted by the ROM 105 into PLL frequency division ratio data, and the frequency division ratio data corresponding to a predetermined channel is determined.
A predetermined channel is received.

In other words, the decoder 104 and ROM 105 convert it to programmable PLL data, transfer it to PLL 103, and
The LL103 tunes the broadcast of the frequency corresponding to the input data.

Further, the switch 115 has a time setting function, the time set data by the switch 115 is separated by the switch data processing circuit 112, and the time is set by transferring the time set data to the clock circuit 108. It

 Next, the program reservation operation performed by the receiver will be described.

Data such as program channel data, viewing start data, and end data at the time of reservation generated from the switch 115 is input to the switch data processing circuit 112 via the switch data input circuit 113. The switch data processing circuit 112 outputs reserved data such as reserved channel data, reserved time data and power supply control data, and also outputs channel data during normal reception outside the reservation. Reserved channel data is reserved channel data processing circuit 110.
And the reservation time data is distributed to the clock circuit 108.
Further, the power supply control data is distributed to the power supply 116.

The display 114 is controlled by the display control circuit 111, and the broadcast channel program being received, the current time, the reserved channel,
Display the reservation time. In this case, the display item is switch 11
This is done by switching the display data by 5.

 The reserved program is received as follows.

The reserved channel data and the reserved time data reserved by the receiver are stored in the RAM 109 after being processed by the reserved channel data processing circuit 110. The reserved channel data and the reserved time data stored in the RAM 109 are added to the changeover switch 106 and the comparator 107, respectively. In the comparator 107,
The current time data of the clock circuit 108 built in the receiver side is compared with the reserved time data. In this case, when a coincident output is obtained by the comparator 107, the power supply 116 is controlled, and the changeover switch 106 is changed over to supply the reserved channel data stored in the RAM 109 to the decoder 104. The reserved channel data decoded by the decoder 104 is converted by the ROM 105 into frequency division ratio data corresponding to the corresponding reserved channel data,
The PLL 103 performs tuning corresponding to the reserved channel.

At the end of reception of the reserved channel, the comparator 107 compares the current time data with the reserved time data to shut off the power supply when a coincident output is obtained.

However, in such a system, the key information for descrambling the scrambled broadcast signal is transmitted, so that there remains a problem that illegal viewing may be carried out.

For example, the scrambling method includes scrambling by a time axis replacement process of replacing scanning lines or pixels. Generally, the replacement content uses the output of a random number generator. As a random number generator, for example, a PN pattern generating circuit is known which feeds back any output of a shift register to an input side via a predetermined logic circuit. In this case, correct descrambling is performed by generating the same random number as that generated on the broadcast station side. In order to match the random numbers on the broadcasting station side and the receiver side, the initial values of the random numbers on the broadcasting station side and the receiver side may be matched. Therefore, the broadcasting station side conceals the subscriber-specific identification code sent at the time of reservation and the initial value, and multiplex-transmits them. Since the receiver has the identification code, only the reserved subscriber can obtain the initial value.

As described above, in the conventional system, since the key information for descrambling is transmitted, the decryption by mischief is relatively easy.

(Problems to be Solved by the Invention) In the conventional scrambling technique, although the initial value for random number matching is transmitted in a concealed manner, there is a problem that the confidentiality is low and is relatively easily found. .

The present invention solves the above problem and makes it difficult to decipher the initial value.
A subscription broadcasting system capable of performing highly confidential scramble broadcasting.

[Structure of the Invention] (Means for Solving Problems) The present invention is a means for generating transmission time data, and means for generating random number data for scrambling whose initial value is changed with time based on the transmission time data. , Means for scrambling the broadcast signal by the random number data from this means and transmitting the scrambled broadcast signal to the decoder side together with the transmission time data, the decoder side reproducing an initial value from the transmission time data, and based on this initial value It is characterized in that it is provided with a means for generating random number data for descrambling that matches the encoder side, and that key information for decrypting the random number data is not transmitted.

(Operation) In the pay broadcasting system, only the contracting subscriber who scrambles the broadcast signal in order to prevent the non-contracting subscriber from viewing and reserves the viewing together with the reservation time data,
It is possible to obtain a random number initial value for descrambling. In the present invention, random number data whose initial value changes every moment is generated according to the clock data by the clock circuit on the encoder side, and scrambles the broadcast signal by this random number data. Then, the clock data is transmitted to the decoder side together with the broadcast signal. The decoder side can decipher the initial value based on the transmission time data by notifying the broadcasting station side of the reserved time and the like, and correct descrambling can be performed. That is, in the present invention, the initial value is managed by both the broadcasting station side and the receiver side, and since the key information for decrypting the initial value is not sent, the protection of the broadcast signal against snooping is ensured.

(Examples) The present invention will be described below with reference to illustrated examples.

FIG. 1 is a schematic block circuit diagram showing the present invention. In FIG. 1, a signal for pay broadcasting is supplied to an encoder-side input terminal 1, and the signal from the terminal 1 is sent through an input data processing block 2 to one side of a scrambler 3 by an exclusive OR circuit. Guided to the input end. A time data generation block 4 is provided on the encoder side, and transmission time data is output from this block 4.
The transmission time data is input to a random number generator 5 such as a PN pattern generator, and the generator 5 outputs random number data whose initial value changes according to the change with time of the transmission time data. The random number data is guided to the other input terminal of the scrambler 3, and scrambles the broadcast signal. The scrambled data derived from the scrambler 3 is supplied to a data superimposing circuit 6 to which the transmission time data is input, and the transmission time data is multiplexed in a predetermined period of the scrambled data. The output from the data superimposing circuit 6 is sent to the circuit 8 as an RF transmission signal via the output data processing block 7.

The RF transmission signal from the line 8 is processed by the reception data processing block 9 on the decoder side and input to the data separation circuit 10. The data separation circuit 10 separates transmission time data and scramble data. The transmission time data is supplied to the random number generator 12 having the same configuration as the encoder side, and the random number generator 12 outputs the random number that matches the scramble time. The random number data from the random number generator 12 and the scramble data are input to the descrambler 11 and descrambled. Data from the descrambler 11 is processed by the output device 13 and output terminal
It is led to the television receiver through 14.

2 and 3 are practical examples of the system of FIG.

 The broadcast signal will be described by taking an audio signal as an example.

As a service form of a voice signal, there is a digital voice service in which an input analog signal is digitally converted and an error correction function is provided for a code error due to a transmission system. In this type of digital voice service, data is normally transmitted in the form of interleave, and the influence of the last noise is suppressed, so that high quality data transmission is possible.

First, FIG. 2 shows an encoder circuit. Input terminal 201
An analog audio signal to be broadcast is applied to. This analog signal is converted into a digital signal by the A / D converter 202, and then converted into serial data by the P / S conversion circuit 203. Then, the data compression circuit 204 performs data compression to improve the transmission efficiency. This data-compressed data is sent to an error correction addition circuit via a scrambler 3 and a data superposition circuit 6 which are composed of an exclusive OR circuit.
At 206, an error correction code is added. The serial data to which the predetermined code such as the error correction code is added is interleaved by the interleave circuit 207, subjected to the predetermined modulation processing by the modulation circuit 208, and further frequency-changed to the predetermined RF frequency by the frequency conversion circuit 209. It is amplified by the amplifier 210 and output from the output terminal 211 to the transmission system.

The timing signal for the above data processing is generated by the timing circuit 212. The timing circuit 212 includes a P / S conversion circuit 203, a data compression circuit 204, a P / S conversion circuit 213 for transmitting time data, and a data compression circuit.
Generating 214 operation timing signals.

The clock circuit 215 generates current time data, and this current time data is P / S converted by the P / S converter 213, further compressed by the data compression circuit 214 and added to the data multiplexing circuit 6.

The data multiplexing circuit 6 superimposes the digitized voice data and the current time data over time.

Further, in this embodiment, the time data from the P / S converter 213 is supplied to the random number generator 5. The random number generator 5 has a first
As described in the figure, the initial value of the random number data to be output is changed every time the content of the clock data is updated.

Next, a decoder circuit for decoding the scrambled broadcast signal transmitted via the transmission path will be described.

In FIG. 3, blocks having the same functions as those in FIG. 1 are designated by the same reference numerals. The frequency of the transmission signal input to the terminal 301 is converted by the frequency conversion circuit 302. The data received by the tuning operation by the frequency conversion action is separated by the plurality of circuits 303.

The data separated here is deinterleaved by the deinterleave circuit 304, and then the error correction circuit 305.
Then, the code error is corrected to form a digital data string. This digital data string is separated by the data separation circuit 10 into digital voice data and current time data.

At this time, the separated compressed audio data is expanded by the audio data expansion circuit 307 through the descrambler 11, converted into an analog amount by the D / A conversion circuit 308, and further amplified by the amplification circuit 309. It is output to the audio output terminal 311 via the mute circuit 310.

The broadcasting channel is selected by setting the frequency division ratio for the PLL circuit 312. The packet synchronization for receiving the data is performed by using the synchronization pattern generated by the synchronization pattern generation circuit 313 and detecting the coincidence with the transmission synchronization pattern by the exclusive OR circuit 314. That is,
The sync pattern follows the pattern generated by the sync pattern generation circuit 313, and is used by the exclusive OR circuit 314 to determine the suitability of the sync timing. In this way, the data acquisition timing is controlled, but at this time, the counter circuit 317 is reset according to the output of the latch circuit 318 that latches the pattern match signal detected by the exclusive OR circuit 314. A timing pulse corresponding to the output is generated in the timing pulse generation ROM 316.

On the other hand, the current time data separated by the data separation circuit 10 is supplied to the random number generator 12 and the S / P conversion circuit 315.
The random number generator 12 is composed of the same circuit as the broadcasting station side,
The random number data to be output has a pattern in which the initial value is changed in accordance with the temporal change of the current time data in correspondence with the broadcasting station side, and thus matches the broadcasting station side. The current time data converted into parallel data by the S / P conversion circuit 315 is supplied to the RAM 320 for time data storage. Writing and reading of the RAM 320 are performed by the DMA circuit 319 which generates an address signal in response to the timing pulse from the timing generation ROM. In this case, so-called cycle still processing is used in order to improve the efficiency of writing and reading processing.

The time data written in the RAM 320 is used for control such as program reservation control. A control unit 333 for controlling program reservation, broadcast reception, etc. using this current time data
Is composed of a circuit substantially equivalent to that shown in FIG. The time data once written in the RAM 320 is the display control circuit 330 and the comparator 3.
Added to 25. The current time data applied to the display control circuit 330 drives the display device 331 and is displayed by the display means such as liquid crystal, and functions as a clock for the subscriber on the decoder side.

The subscriber operates the switch circuit 332 to
Control can be performed in two modes: a channel for which reservation is desired, a program reservation mode for setting a program start or end time, and a direct channel selection for directly selecting a program.

In the program reservation mode, reservation data such as the set reservation channel and program start time data is input to the switch data processing circuit 328 via the switch data input circuit 329. This reservation data is stored in the reserved program storage control circuit 327.
After being subjected to predetermined data processing by, the data is added to the RAM 326. Of the reservation data from the RAM 326, the reservation time data is supplied to the comparator 325 and compared with the current time data from the RAM 320. Of the reservation data, the reservation channel data is led to the A end side of the changeover switch 324.

Then, the comparator 325 compares the current time data read from the RAM 320 with the reserved time data read from the RAM 326. Here, when the reserved time data and the current time data match, the output of the comparator 325 switches the changeover switch 324 to the terminal A side. By this switching operation, the reserved channel data set corresponding to the reserved time data is added to the decoder 321 in the RAM 326. The decoder 321 generates an address necessary to read the frequency division ratio data corresponding to the reserved channel from the ROM 322. Then, the PLL data corresponding to the reserved channel is applied to the PLL circuit 312 from the ROM 322 according to this address.
In this case, the automatic channel selection circuit 323 performs channel selection control for the decoder 321 by the coincidence signal from the latch circuit 318. In this way, the frequency division ratio corresponding to the reserved channel is set in the PLL circuit 312, so that the reserved channel can be received. The mute circuit 310 operates so that noise does not occur at the output terminal 311 if the synchronization pattern is not synchronized even when the reserved channel is received.

When the subscriber directly selects a channel by operating the switch 332, the selector switch 324 is connected to the terminal B side by the output of the comparator 325, and the channel selection data is processed by the switch data processing. Decoder 3 via circuit 328
Data for reading the frequency division ratio data corresponding to the selected channel from the ROM 322 is applied to 21. This allows direct channel selection.

FIG. 4 is a time chart showing the timing relationship between both data when the clock data is superimposed on the audio data in the encoder circuit. In this way, on the broadcast side, P /
The digital audio data digitized by the S conversion circuit 203 (FIG. 2 (a)) is data-compressed by the data compression circuit 204, and the serial data length is shortened by this compression (FIG. 2 (b)). The clock data (FIG. 2 (c)) compressed during the time between the compressed data packets is data-multiplexed by the data multiplexing circuit 6 in accordance with the timing of the multiplexing timing pulse (FIG. 2 (e)). (FIG. 2 (d)).

In this way, the data string in which the current time timing information is multiplexed is sent from the encoder side after being interleaved in the format as shown in FIG. 5, for example. In the transmission format, one packet consists of 64 bits, and 32 packets form one frame. The time data is transmitted by dividing a data string indicating "month", "day", "hour", "minute" into several packets.

FIG. 6 is a circuit diagram showing a configuration example of a specific circuit of the random number generator 12.

Since the random number generator 12 used in this embodiment is a PN pattern generation circuit and the transmission clock data from the data separation circuit 10 is a digital data string, first, the S / P conversion circuit 4
It is converted to parallel data at 01. In this case, since only the time data is extracted, the data extraction pulse G3 from the timing circuit 316 is supplied to the S / P conversion circuit 401. The parallel data is supplied to the latch circuit 402 whose latch operation is controlled by the pulse T1. The pulse T1 is for delaying the scrambled (descrambled) voice data by one frame with respect to the time data. This is because the decoder side must descramble at the same timing as the encoder side based on the time data, and the decoder side needs to know the time data in advance.

Next, the output of the latch circuit 402 is input as address data to the ROM 403 in which initial value data is stored. As a result, the initial value data of the random number based on the PN pattern corresponding to the time data is sequentially updated and read from the ROM 403 in response to the change over time of the time data. This data is parallel output, this initial value data is the timing pulse
The data is input to the P / S conversion circuit 403 that performs conversion at T2, converted into serial data, and input via the gate circuit 405 to the shift register 406 that is the main element of the PN pattern generator. The shift register 406 includes ι stages, and a predetermined logic circuit 407 is connected to each output terminal group. And in this circuit,
The signal from the final bit output terminal is fed back to the gate circuit 405, and the gate circuit 405 again returns the shift register 406.
Are input as data. Note that the gate circuit 405
Guides the initial value data to the shift register 406 when it is at "L" low level, and guides the final bit signal to the shift register 406 when it is at "H" high level. Then, the random number data from the logic circuit 407 is derived as descramble data in the scramble (descramble) audio data period through the AND circuit 408 which performs a gate operation by the scramble (descramble) operation selection signal G2 from the timing generator 316. To be done. The operation selection signal G2 is a signal that becomes high level during the audio data period, and
The AND circuit 408 opens the gate corresponding to the voice data period. The S / P conversion circuit 401, the P / S conversion circuit 404, and the shift register 406 are driven by a common clock signal CK.

Next, the operation of FIG. 6 will be described with reference to FIG. FIG. 7 is a timing chart for explaining random number data updated by time data over three frames (n, n + 1, n + 2). The circuit on the decoder side will be described.

If the time changes from X to Y during the period of the frame n, the latch circuit 402 latches the time data X in the frame n and the time data Y in the frame (n + 1). As a result, the ROM 403 stores the frame
During the period, the initial value data corresponding to the time data X is read, and the load pulse generated immediately before the end of frame n
T2 (see arrow position Load) is output from the AND circuit 408 during the frame (n + 1) period by controlling the gate circuit 405 so that the initial value data corresponding to the time data X is input to the shift register 406. The random number data is a function f (X) having the time data X as a parameter. As can be seen by comparing this random number data with the scrambled voice data (f), the generation times of both data coincide with each other, and the scrambled voice data (f) is descrambled by the random number data f (X), It becomes data (c).

Similarly, in the load pulse generated immediately before the end of the frame (n + 1), the initial value data corresponding to the time data Y is changed to the frame (n + 2) because the time data changes to Y in the frame (n + 1). The scrambled audio data can be descrambled by the random number data f (Y) given to the first scrambled audio data and then generated according to this data. (G) shows the transmission data and corresponds to (d) of FIG.

As is clear from the above description, in the present embodiment, the key information is not transmitted for descramble, and this key information is managed by both the broadcasting station side and the receiver side. The data disclosed to the public are transmission time data. Therefore, even if a non-subscriber tries to eavesdrop on a scrambled pay broadcast by mischief, it is difficult to decipher the initial value.

As described above, this embodiment uses the clock data transmitted from the broadcasting station side to the receiver side as a signal for descrambling to realize a pay broadcasting system that is extremely difficult to decipher.

The transmission time data need only be the time data itself as long as it changes with time. Furthermore, the subscription broadcasting system of the present embodiment can be applied to any form regardless of whether it is paid or free.

[Effects of the Invention] As described above, according to the present invention, since data for scramble decoding is not directly transmitted, confidentiality is high,
Moreover, since the pattern changes with the passage of time, there is an advantage that the scrambling effect is high.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing the basic concept of the present invention, and FIG.
FIG. 4 is a circuit diagram showing an encoder side of a subscription broadcasting system according to an embodiment of the present invention, FIG. 3 is a circuit diagram showing a decoder side of the same embodiment, and FIGS. 4 and 5 explain the operation of the present invention. 6 is a circuit diagram showing an example of a concrete circuit of the random number generator used in the embodiments of FIGS. 2 and 3, and FIG.
FIG. 6 is a time chart diagram for explaining the operation of FIG.
FIG. 8 is a circuit diagram showing an example of a decoder side circuit in a conventional subscribing broadcasting system. 3 ... Scrambler, 5 ... Random number generator, 6 ... Data superimposing circuit, 10 ... Data separating circuit, 11 ... Descrambler, 12 ... Random number generator, 215 ... Clock circuit.

Claims (1)

(57) [Claims] 1. A subscribing broadcasting system for scrambling a broadcast signal according to random number data on the encoder side and transmitting the scrambled signal to a decoder side, comprising a clock data generating means for generating transmission time data on the encoder side and a means for generating the random number data. There is a random number data generation unit whose initial value is changed with time based on the transmission time data from the clock data generation unit, and scrambles the broadcast signal by the random number data from the random number data generation unit, Means for transmitting the scrambled broadcast signal to the decoder side together with the transmission time data, and reproducing the initial value from the transmission time data on the decoder side, and for descramble matching the encoder side based on the reproduced initial value. At least scramble decryption means that generates random number data Subscription broadcasting system characterized by comprising