JPS6074888A - Picture scramble and descramble system - Google Patents

Abstract

PURPOSE:To improve the private properties of pictures and also to keep high picture quality by exchanging the periods before and after the intermediate point for each horizontal scan cycle to define it as a picture period of each horizontal scan cycle of a scramble picture and varying the position of the intermediate point for each horizontal cycle. CONSTITUTION:The digitized original picture signals supplied in parallel to line memories 10 and 11 are written alternately for every horizontal scan cycle and also read out alternately to be supplied to a D/A converter 17-b via AND gates 14 and 15 and an OR gate 16 to which read signals are applied respectively. Then the scrambled analog picture signals are extracted. In a write mode the digitized original pictures are written alternately from 0 of counters 19 and 20 for each horizontal cycle and in the order as shown by a figure (1). In a read mode out of memories 10 and 11, the initial values equal to the binary codes of key signals are set to counters 19 and 20 as shown by a figure (2) under the control of an address control circuit 18. The reading is started at and after the memory address at an intermediate point (b).

Description

Detailed Description of the Invention The present invention provides image information only to a specific receiving device when transmitting an image signal, and hides the image information from other receiving devices. Regarding an image scrambling/descrambling method in which the WII image signal is restored after being disturbed so as to be restorable, image scrambling/descrambling can be achieved by simple signal processing with less risk of image information leakage and less image quality deterioration of the restored image. This is how it was done.

Prior Art This type of image scrambling/descrambling method is required in the technical field of image transmission such as communication and broadcasting, regardless of whether it is wireless or wired.In recent years, there has been a strong tendency to emphasize the value of image information. However, as creators become more interested in copyright protection, the need for it is increasing. - In image transmission such as communications and broadcasting, it is often possible for the image to be received by a large number of unspecified receiving devices, making it easy for image information to be arbitrarily acquired without permission. Therefore, when transmitting image information, the image signal is removed from its normal state and transmitted in a state that is disturbed in a specific manner, so that only an authorized receiving device can restore the image signal to its normal state and obtain the image information. This is why this kind of image scrambling/descrambling method has become necessary, and in recent years it has been seen as particularly useful for wireless or wired pay television systems and television program distribution systems using satellite transmission channels. It is.

Therefore, it is desirable for this type of image scrambling/descrambling method to satisfy the following conditions.

(1) It is difficult to detect original image information from scrambled images.

(2) It is extremely difficult to restore a normal image without using a regular receiving device.

(3) Images restored to a normal state by a regular receiving device have little deterioration in image quality and no loss of information.

(4) All signal processing devices for scrambling image signals and restoring them to a normal state are simple and inexpensive.

Conventionally, the following methods have been typical as image scrambling/descrambling methods that are desired to satisfy such conditions.

(1) Transmitting the image signal by replacing the regular synchronization signal commonly used in the image signal with another form of synchronization information.

(2) Add a specific interference component to the 1fil image signal.

(8) Scanning with randomly selected polarities of image signal components
Flip about the line.

However, all of these conventional image scrambling/descrambling methods have some drawbacks. In other words, (1) the method of concealing synchronization information can almost maintain image synchronization by adjusting the oscillation frequency of the synchronous oscillator in any image receiving device, so there is a risk that the contents of the image information can be roughly determined. . (2) In the method of adding interference components, interference components with a simple configuration are easily removed;
On the other hand, since it is difficult to completely remove additional interference components during normal reception, the quality of the restored image tends to deteriorate. Furthermore, (8) the method of inverting the polarity of the image signal component has the drawback that image contour information tends to remain in the scrambled image, resulting in insufficient confidentiality.

The purpose of the present invention is to eliminate the drawbacks of the conventional method described above, satisfy the above-mentioned requirements, make it difficult to infer image information even when looking at the entire image, and have almost no image quality deterioration in the normal restored image. Furthermore, it is an object of the present invention to provide an image scrambling/descrambling method in which unauthorized image restoration is extremely difficult, and in which image signal processing can be performed using relatively inexpensive equipment.

That is, the image scrambling/descrambling method of the present invention extremely reduces the correlation of images between scanning lines (by irregularly moving the position of an image on a horizontal scanning line in an image signal for each scanning line). The periods before and after the midpoint of the image period are swapped for each horizontal scanning period in the original image signal to form an image period for each horizontal scanning period in the scrambled image signal. The scrambled image signal is constructed by varying the position of the intermediate point.

EXAMPLES Below, the present invention will be described in detail by way of examples with reference to the drawings.

First, the basic configuration of the transmitter and receiver for image scramble transmission to which the method of the present invention is applied is shown in Figure 1 (
Shown in a) and (1)3, respectively. In the illustrated transmitting device, a scrambling device 3 scrambles standard television image signals from a television camera 1 and a VTR 2.
The scrambled image signal is converted into a scrambled image signal and transmitted via the transmitter 4 and the transmitting antenna 5. - In the illustrated receiving device, the scrambled image signal received via the receiving antenna 6 and receiver 7 is supplied to the descrambling device 8, converted to a standard format image signal, and supplied to the image display device 9. and display image information.

The principle of the image scrambling method of the present invention for transmitting image information using a transmitting/receiving device having such a configuration is shown in FIG. 2(a) and (
1)). In the image scrambling method of the present invention, the midpoint of the image period a to C following the horizontal synchronizing signal and color burst signal of each horizontal scanning period in the original image signal waveform as shown in FIG. The periods a to b and b to c before and after are replaced as shown in Figure 2 (in Figure 2), and the midpoint is changed to Figure 2 (a).
, as shown in (b), a scrambled image signal is constructed by changing the signal for each successive horizontal scanning period.

As a result, the original image shown in FIG. 3(a), which is represented by 12 scanning lines for simplicity, becomes as shown in FIG. It does not have to be completely concealed, and since the image period of each horizontal scanning cycle is simply divided into two and swapped back and forth, the signal waveform is hardly damaged and can be almost completely restored. .

Specifically, in the image scrambling/descrambling method of the present invention, as described above, the position information of the midpoint of the boundary that divides the image period into two is converted into a binary encoding key (N number) and is separated from the scrambled image signal. For example, the key signal can be transmitted on a digitized audio signal transmission channel, and if necessary, the signal format of the key signal can be changed and encrypted, so that the means for restoring the original image signal can be almost completely concealed. can.

Note that in order to receive such a scrambled image signal and restore it to the original image signal, first, the encrypted key signal is decoded and the position of the midpoint of the image/period for each successive horizontal scanning period is detected. , the original image signal waveform can be easily obtained by performing signal processing in the reverse process to that on the transmitting side.

Next, FIG. 4 shows an example of the configuration of the scramble device 8 on the transmission side that performs signal processing for image scrambling according to the method of the present invention as described above. In the scrambling device having the configuration shown in the figure, the input original image signal is guided to the analog-to-digital converter 17-a and digitized, and then
It is supplied to line memories 10 and 11 in parallel. These 1-line memories 10 and 11 output a square wave signal whose polarity is inverted every horizontal scanning period, which is formed by supplying horizontal synchronizing pulses to the distribution unit 12, and converts the signal into a Q signal depending on the presence or absence of the inverter 18.
Furthermore, since signals with polarities reversed are applied as write/read signals, the write state is alternately set and the read state is alternately set in each horizontal scanning period. Therefore, the digitized original image signals supplied in parallel to those one-line memos IJ 10 and 11 are alternately written and read out every horizontal scanning period, and the respective readout signals are applied to the digitized original image signals IJ14 and IJ14. .15 and the OR gate 16 to the digital-to-analog converter 17-b, and is extracted in the form of a scrambled analog image signal as will be described later. In addition,
In the case of digitizing and transmitting a scrambled image signal, it goes without saying that the output of the ORG 16 can be taken out as it is as a scrambled image signal.

Therefore, ■The writing of the original image signal to the line memory 10.11 is based on the initial value of the address counter 19.
0" to Q sequential memory addresses by the counting output pulses of the digitized sample clock period, so that the digitized original image signal is output alternately every horizontal scanning period in the order of 9 as shown in FIG. 2(a). are written respectively.

- When reading from the 1-line memory 10.11, a binary code key signal indicating a different position for each horizontal scanning period of the midpoint of the image period shown in FIGS. 2(a) and (b) is used. Under the control of the supplied address control circuit 18,
Since an initial value equal to the binary code of the key signal is set in the address counters 19 and 20, reading starts from the memory address at the intermediate point and goes around. Therefore, alternate digitized scrambled image signals are read out from the one-line memos IJ 10 and 11 every horizontal scanning period in the order shown in FIG. 2).

According to the image scrambling of the present invention method as described above,
Since only the signal position on the image period time axis in the original image signal is changed, the signal band of the scrambled image signal is the same as the signal band of the original image signal, and it can be transmitted using the normal image signal transmission path. I can do it. Further, as described above, since writing and reading are performed alternately in the pair of one-line memories at line intervals, continuous scramble signal processing can be performed in real time.

Note that the descrambling device 8 on the receiving side shown in FIG. However, the initial value of the address counter when reading one line of memory for restoring the original image signal is
In the scrambler 3, the period a in FIG.
The difference is that the descrambling device 8 makes the first period correspond to c, whereas the first period corresponds to c.

Next, FIG. 5 shows another configuration example of the address control system of the one-line memory in the circuit device shown in FIG. In the memory address control system having the configuration shown in the figure, the setting of the initial value of the address counter when reading a scrambled image signal from the one-line memory is simplified as shown in the following. In other words, the initial value of the address counter needs to be different for each horizontal scanning line in correspondence with the intermediate point that is different for each horizontal scanning line, but if a key signal representing the initial value is transmitted for each horizontal scanning line, The amount of key signal transmission increases and transmission efficiency decreases.

On the other hand, in the memory address control system shown in FIG. -H the binary symbol that makes up the signal
The signal is held in the latch circuit 21 and then supplied to the input terminal of the shift register 22. This shift register 22 has an output end fed back to an input end, is configured in an endless connection, and is driven by a horizontal synchronizing pulse to flash the input binary code in a horizontal scanning period. Therefore, since the output binary code is sequentially and repeatedly added to the middle of the input binary code, this shift register 22
Pseudo-random signals (PN signals) consisting of binary symbols of different formats are taken out in parallel in each line-sequential horizontal scanning period.This PN signal is supplied as an initial value to the address counter 28 in each horizontal scanning period. For example, it is no longer necessary to transmit the key signal every horizontal scanning period, and the amount of transmission can be significantly reduced.Furthermore, since the initial value of the sear address counter 23 is randomized by the PN signal,
The vertical correlation in the scrambled image is extremely reduced.

Next, in order to reduce the amount of key signal transmission, as shown in Figure 6, it is necessary to limit the range of the position of the midpoint that divides the image period into two and set it in advance to an appropriate number N. ,for example,
The initial value of the address counter of N and Oshi corresponding to the midpoint position of N and Oshi is stored on the receiving side, and only the initial value number of N and Oshi is used as a key signal as a simple binary stamp signal. It is also possible to transmit the information by In other words, the position of the midpoint that bisects the image period is set at four points of the color subcarrier frequency to ensure phase continuity of the carrier color signal.
If we were to select sample points from double the sampling frequency, there would be more than 700 points, but in order to maintain the confidentiality of image information appropriately, the type N of the intermediate point position should be set to 16 or 8.
Setting it to 2 is sufficient. Therefore, to transmit the intermediate point position information of 700 points, it is necessary to transmit 10 bits of address bits, but if N=32, 5
If you transmit a key signal that is a binary number of bits, you will be able to use it.

Next, the configuration of the transmitting side scramble device 8 shown in FIG. 1(a) can be simplified as shown in FIG. 7. In the illustrated configuration, as shown in FIG. 4, charge-coupled devices (COD
, l, etc., to form a scrambled image signal according to the present invention. That is, the original image signal is supplied to the sampling circuit 24, sampled, and then sequentially supplied to the two-line delay circuit 25 in real time. The 2-line delay circuit 25: A selector control circuit that transfers sample values of the original image signal sequentially through the horizontal scanning period to the analog data selector 26 for two lines in parallel, and drives it by the input key signal. According to the control signal from 2.7, image signal sample values are taken out in the order shown in FIG. One line of scrambled image signal in analog signal form is extracted.

Next, aspects of signal formation that prevent image quality deterioration during transmission of scrambled picture No. 14 according to the method of the present invention are sequentially shown in FIGS. 8(a) to 8(d).

In general, both ends of the image period of each horizontal scanning period of the image signal are damaged by limitations on the signal transmission band during signal processing and transmission to form a composite signal, resulting in image quality deterioration such as a decrease in signal amplitude. Normally, such image quality deterioration appears at both ends of the screen and is hardly noticeable. On the other hand, in the scrambled image signal of the method of the present invention, the image signal components in the center where the image quality deterioration is easily noticeable are moved to both ends of the image period and transmitted, so that the original image is transmitted on the receiving side. When the signal is restored and displayed, the above-mentioned deterioration in image quality becomes extremely noticeable. In the scramble signal formation according to the embodiment shown in FIG. 8, as shown in FIG. A period exceeding the intermediate point shown in FIG.

Therefore, in the received signal after passing through the transmission path, the high-frequency components are blocked and the signal waveforms at both ends are distorted, as shown in (0) in the same figure, but if these parts are gated and removed, In the restored image signal in which the curved end portions are returned to the center portion, no distortion of the signal waveform appears, as shown in FIG. 3(d), and good image quality can be maintained.

Various types of signal processing that are suitable to be added in order to increase the effect of image scrambling according to the present invention, which performs the signal processing as described above, will be listed.

In the signal processing shown in FIG. 9, the synchronization signal of one standard television set is replaced with digital synchronization information, leaving only the part that serves as a trigger, and synchronization cannot be achieved with a general television receiver. In this way, image confidentiality is increased.

In addition, in the signal processing shown in FIG.
As shown in (a) of the same figure, the position of the color burst signal with respect to the horizontal synchronization signal is changed, including the period of the color burst signal, as shown in (b) of the same figure. Therefore, with respect to such a scrambled color image signal, phase synchronization of the carrier color signal is impossible in a general television receiver, and the secrecy of the color image is significantly increased.

Furthermore, in the signal processing of the mode shown in FIG. 11, in the image scrambling of the present invention method, the key signal itself, which is a binary symbol indicating the position of the midpoint that bisects the image period for each horizontal scanning period, is As shown in the figure (al), the received encryption key signal is transmitted via the encryption circuit 29, and on the receiving side, as shown in the figure, the received encryption key signal is converted into a binary code via the post-encryption circuit 30. It is used to descramble the received scrambled image signal. Therefore, even if the existence of the key signal is detected and an attempt is made to illegally descramble it, the key signal itself is encrypted, so unless the code can be deciphered, it will be impossible to restore the original image signal. becomes.

In the above explanation, the present invention method image scramble φ
Although descrambling has been described as being applied exclusively to composite color image signals such as the NTSO system, the application of the method of the present invention applies to composite color image signals as well.
It can be applied not only to the O method but also to the PAL method, SEOAM method, etc. Furthermore, in addition to the composite color image signal in which the carrier color signal is frequency-multiplexed with the luminance signal, MAO, which has been proposed as a new television system,
()4ultiplexed Analogue co
TOICT Time Compressed Inte as a high-definition television system and
12(a), the image period of each horizontal scanning period is divided into two and the image period of each horizontal scanning period is divided into two and transmitted separately in a time-division manner. For example, in the image signal (b
) The image scrambling and descrambling according to the present invention can be applied as shown in FIG.

Effects As is clear from the above explanation, the following remarkable effects can be achieved by implementing the image scrambling/descrambling of the present invention.

(1) It is almost impossible to detect the image information of the original image from the scrambled image.

(2) It is extremely difficult to restore the scrambled image signal to the original image signal unless restoration is performed in its normal form.

(3) A restored original image that has been restored in a normal manner has extremely little deterioration in image quality compared to the original image.

Therefore, the image scrambling/descrambling according to the present invention has high confidentiality of image information and can sufficiently maintain the quality of the image information.

For example, when the image scrambling/descrambling of the present invention is applied to an image signal digitized using an A/D and D/A converter and a one-line memory,
There is little damage to the image, and the image quality can be maintained sufficiently.

In addition, if ~ is supplied to the pseudo-random signal generation shift register as a key signal specifying the position of the image period division point for each horizontal scanning period, the key signal itself is transmitted intermittently,
During that time, the dividing point position can be designated by binary symbology of a pseudorandom signal generated based on the key signal, so the amount of key signal transmission can be significantly reduced.

Further, when the positions of the image period dividing points are limited to a plurality of appropriate types, the amount of key signal transmission can be reduced and the scrambling circuit device can be simplified.

Further, when image scrambling according to the present invention is performed using an analog delay circuit, it is possible to obtain a low-mounted scrambling circuit device with a simple configuration.

In addition, if extra signal parts are extended and added to both ends of the image period for each horizontal scanning period in a scrambled image signal, even if the signals at both ends of the multi-image period are damaged due to band limitations of the transmission path, etc. It is possible to eliminate this effect from appearing in the center of the restored image.

Furthermore, if the synchronization signal is also replaced with digital synchronization information, image confidentiality can be further increased.

Furthermore, if the color burst signal period is included in the image period and the image period is divided and replaced according to the method of the present invention, the confidentiality of the color image information will be further increased, and it will be impossible to restore the original image signal unless the code is broken. Become.

In addition, the image scrambling and Φ descrambling of the present invention method can be widely applied to composite color image signals of all methods, and furthermore, to color image signals of a method of time-division multiplexing transmission of time-axis compressed luminance and color image signals. The following effects can be mentioned.

Furthermore, the image scrambling/descrambling according to the method of the present invention can be applied not only to image transmission such as image communication and television broadcasting, but also to image package media such as VTRs and video discs.
Similar effects can be achieved by applying the present invention not only to image signals similar to television, but also to image signals such as facsimile and photo transmission.

Note that, of course, if a plurality of intermediate division points are provided for each image period, image confidentiality can be further increased.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic configuration of an image scramble transmission device, and Figures 2 (a) and (b) are image scramble transmission devices according to the present invention.
Signal waveform diagrams sequentially showing the principle of the descrambling method; FIGS. FIG. 5 is a block diagram showing a configuration example of the image scramble/descramble circuit device according to the invention; FIG. Block diagram; FIG. 6 is a signal waveform diagram showing an example of how image periods are divided for each horizontal scanning period in the image scrambling/descrambling circuit device; FIG. 7 is an image scrambling/descrambling circuit according to the present invention. A block diagram showing another configuration example of the apparatus; FIGS. 8(a) to (1) are signal waveform diagrams sequentially showing other aspects of image period division in image scrambling/descrambling according to the present invention; 9 is a signal waveform diagram showing still another aspect of the image period division, and FIGS. 11 (al, (b) is a block diagram sequentially showing a configuration example of a circuit device that encrypts and transmits a key signal specifying the division position of the image period division, and FIG. 12 (a), (
b) is a signal waveform diagram sequentially showing still another aspect of the image period division. ■... Television camera 2... VTR 3... Scrambler 4... Transmitter 5... Transmitting antenna 6... Receiving antenna 7.
...Receiver 8...Descrambling device 9...Image display device 10, 11...L line memory 12...% frequency divider 13...Inverter 14, 1
5...AND gate 16...OR gate 17-a.
・Analog self-digital converter 17-b...Digital Φ analog converter, ]8...Address control circuit 19, 20...Address counter 2]...Latch circuit 22...PN signal generation shift register 23 ...Address counter 24...Sampling circuit 25...
2-line delay circuit 26...analog data selector 27...selector control circuit 28...low-pass filter 2
9... Encryption circuit 80... Decryption circuit. Patent applicant: Japan Broadcasting Association Figure 1 Figure 2 Figure 3 <a) (b> To memory Figure 6 n1 Color Figure 8 Figure 9 rlA Figure 10 Figure 11! Continuation of page 1 0 Invention Masanori Saito Zoku Institute, Setagaya-ku, Tokyo

Claims (1)

[Scope of Claims] 1. Periods before and after the midpoint of the image period are exchanged for each horizontal scanning period in the original image signal to form an image period for each horizontal scanning period in the scrambled image signal, and the horizontal scanning period of the original image signal is An image scrambling e-descrambling method characterized in that the scrambled image signal is constructed by varying the position of the intermediate point every cycle. In the system according to claim 1, a key signal representing information on the position of the intermediate point in each horizontal scanning period in the original image signal is transmitted separately from the scrambled image signal, and the key signal is transmitted separately from the scrambled image signal. An image scrambling/descrambling method characterized in that the scrambled image signal is restored to the original image signal based on a signal. & In the system according to claim 1 or 8, the original image signal is digitized and written into a memory, and when reading the digitized original image signal from the memory, the data before and after the intermediate point are An image scrambling/descrambling method characterized by replacing periods. 4. In the method described in claim 2, a pre-originated image is generated by a pseudo-random binary code signal generated from an endlessly connected shift register in which an initial value is set by the binary-encoded key signal. An image scrambling/descrambling method characterized by sequentially setting the position of the intermediate point for each horizontal scanning period in a signal. & In the method according to any one of claims 1 to 4, the positions of the intermediate points in the image period are set in a predetermined order from among a plurality of positions set in advance for each horizontal scanning period. An image scrambling/descrambling method characterized by selecting 6. In the system according to claim 2, sequentially delayed image signal sample values obtained by supplying the sequentially sampled original image signals to a delay element are selectively applied in accordance with the key signal. An image scrambling/descrambling method, characterized in that the scrambled image signal is formed by extracting the scrambled image signal. ? , In the method described in any one of paragraphs 1 to 6 of the range of % allowance request, the periods exceeding the midpoint are added to the periods before and after the midpoint to perform swapping and transmission. Characteristic image scrambling-descrambling method. & An image scrambling/descrambling method according to any one of claims 1 to 7, characterized in that a synchronization signal in the scrambled image signal is replaced with a digital synchronization information signal. 9. An image scrambling/descrambling method according to any one of claims 1 to 8, characterized in that a color burst signal period is added to the image period before the intermediate point. . lOl In the system according to claim 2, the received scrambled image signal is digitized and written in a memory, and the periods before and after the midpoint are exchanged based on the received key signal to read from the memory. An image scramble/descramble system characterized in that the original image signal is restored by reading out the original image signal. IL In the method described in claim 4, the intermediate point of each horizontal scanning period is determined by the pseudo-random binary code generated from the endlessly connected shift register in which the initial value of the received key signal is set. An image scrambling/descrambling method characterized in that the original image signal is restored from the received scrambled image signal by sequentially setting positions. 1Z In the method according to claim 5, the position of the intermediate A in the image period is selected in the predetermined order for each horizontal scanning period from among the plurality of preset positions. . An image scrambling/descrambling method, characterized in that the original image signal is restored from the received scrambled image signal. 1 & Claim 6 In the system according to claim 6, sequentially delayed image signal sample values obtained by supplying the received and sequentially sampled scrambled image signals to a delay element are provided in accordance with the received key signal. An image scrambling/descrambling method characterized in that the original image signal is restored by selectively extracting it. 14. In the method described in claim 1, the original image signal is restored from the received scrambled image signal by removing periods added beyond the intermediate point from the periods before and after the intermediate point, respectively. An image scrambling/descrambling method that is characterized by: 15. The system according to claim 8 is characterized in that the original image signal is restored by forming a synchronization signal based on the digital synchronization information signal in the received scrambled image signal. A method of descrambling during image scrambling.