JPH05151114A - Radio wave sniffing prevention system - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to a radio wave snooping prevention system, and an object thereof is to prevent the wiretapping of information by decoding leaked radio waves from a computer system at low cost. [Configuration] The data output section 2A of the computer main body 1
The complementary signal generating circuit 12 is connected to the complementary signal generating circuit 12 during a period (between pulses) during which no information signal pulse (for example, an image signal pulse of RGB) output from the data output unit 2A is output. Is generated and transmitted to the display device 9 via the wiring 13 in the cable 7 for transmitting the information signal pulse. In addition, the data output unit 2A
Then, the false information signal generation unit 14A is connected to generate a false information signal to make it impossible to decipher the leaked radio wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave theft prevention system which prevents image information and other data information from being stolen by radio waves leaked from a computer system.

[0002]

2. Description of the Related Art FIG. 8 is an explanatory view of a conventional example.
Is a computer body, 2 is an image output unit, 3 is a dot clock generator, 4 is an RGB dot generator, 5 is an image data memory, 6 is a driver, 7 is a cable, 8 is a receiver, 9
Is a display device, and 10 is a display unit.

Conventionally, for example, the computer main body 1 and the display device 9 are connected by a cable 7, image data processed in the computer main body 1 is sent to the display device 9 via the image output unit 2, and the display unit 10 is operated. I was going to display it.

In this case, for example, the image output section 2 of the computer main body 1 is provided with a dot clock generator 3, an RGB dot generator 4, an image data memory 5, a driver 6 and the like. Then, the driver 6 controls ON / OFF of each of the RGB signals output from the RGB dot generator 4 by the image data output from the image data memory 5. In this case, control is performed in synchronization with the dot clock output from the dot clock generator 3.

By the ON / OFF control by the driver 6, each signal of RGB is sent out to the cable 7 and independently controlled by the control circuit (R, R) in the display device 9.
G, B control circuits). The RGB signals at this time are transmitted as serial signals (transmission of serial data).

The horizontal synchronizing signal H and the vertical synchronizing signal V generated by the image signal generator 4 are sent to the display device 9 through the cable 7 as they are. Each control circuit of the display device 9 uses the received horizontal synchronizing signal H and vertical synchronizing signal V to process and control each signal of RGB, and displays it on the display unit 10 (for example, “H” as shown in the drawing). Shaped image).

In such a case, leaked radio waves are generated from the computer main body 1 or the cable 7. Therefore, for example, when the leaked radio wave is received by the receiver 8 having a highly sensitive antenna, the same image as the image displayed on the display unit 9 can be reproduced.

Therefore, the information processed by the computer system is leaked. As described above, the fact that information leaks from leaked radio waves has recently been regarded as a problem, and a technique aimed at preventing wiretapping has been considered.

For example, there has been considered a method of strengthening the shield of the computer system to prevent the leaked radio waves from being emitted, or to reduce the leaked radio waves. However, what is actually implemented is only the leaked radio wave reduction method that does not cause radio interference to televisions, radios, and the like.

[0010]

SUMMARY OF THE INVENTION The above-mentioned conventional device has the following problems. (1) In general, a large number of leaked radio waves modulated by the timing of image signals or the like are generated from the computer main body, the display device of the computer, or the cables connected thereto.

Although this radio wave is extremely weak, the leaked radio wave contains image information, for example. Therefore, an image can be reproduced by receiving such a leaked radio wave with a receiver equipped with a highly sensitive antenna and performing detection processing as a video signal.

Therefore, as long as the leaked radio waves can be received, the information in the computer system can be stolen. (2) A method of strengthening the shield has been considered in order to prevent information leakage, but such a method is costly and requires a shield mechanism on the operating surface, which makes it easier to use. bad. Therefore, it is not a practical method.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a conventional problem and to prevent the wiretap of image information due to the decoding of leaked radio waves from a computer system at low cost.

[0014]

FIG. 1 is a principle diagram of the present invention. FIG. 1A is a principle explanatory diagram (1), and FIG. 1B is a principle explanatory diagram (No. 2).

In the figure, the same symbols as in FIG. 8 indicate the same components.
Further, 11 is a control circuit, 12 is a complementary signal generation circuit, 13
Is a complementary signal wiring, and 14A is a false information signal generator. The present invention has the following configuration to solve the above problems.

(1) A radio wave sniffing prevention system for preventing information snooping due to radio waves leaked from a computer system, which is provided in a data output section 2A provided in the computer main body 1 for outputting serial information signal pulses. , A complementary signal generating circuit 12 for detecting the presence or absence of the output of the information signal pulse and generating a pseudo complementary signal pulse capable of complementing the information signal pulse is connected, and during the period in which the information signal pulse is not output, The complementary signal pulse is generated and transmitted on the same path (cable 7) as the information signal pulse.

(2) In the complementary signal generating circuit 12 having the structure (1), the intensity of the complementary signal pulse is changed in accordance with the combination of a plurality of pulses forming the information signal pulse.

(3) In the complementary signal generation circuit 12 of the configuration (1), complementary signal pulses are independently generated for a plurality of pulses forming the information signal pulse, and the same path as the complementary signal pulse ( The cable 7) is used for transmission.

(4) A radio wave sniffing prevention system for preventing information snooping due to radio waves leaked from a computer system, and a data output section 2A provided in the computer main body 1 for outputting serial information signal pulses, A false information signal generation unit 14A that generates a false information signal synchronized with the information signal pulse is connected, and the false information signal generated by the false information signal generation unit 14A is radiated and output as a radio wave.

(5) A radio wave sniffing prevention system for preventing information snooping due to radio waves leaked from a computer system, and a data output unit 2A provided in the computer main body 1 for outputting serial information signal pulses. , A false information signal generation unit 14A that generates a false information signal synchronized with the information signal pulse is connected, and the false information signal generated by the false information signal generation unit 14A is connected to the same path as the original information signal pulse ( The cable 7) is used for transmission.

(6) A radio wave sniffing prevention method for preventing information snooping from a computer system group in which a plurality of computer systems are collectively arranged, and a serial information signal pulse provided in the main body of each computer system. The information signal pulses output from the respective computer systems are synchronized by connecting the data output sections for outputting the information signal pulses and commonly using the synchronization signal for creating the information signal pulses between the respective computer systems. ..

(7) Configurations (1), (2), (3),
The information signal pulse of (4), (5) or (6) was used as an image signal.

[0023]

The operation of the present invention based on the above construction will be described with reference to FIG. (Operation of Configuration (1)) In FIG. 1A, for example, when an information signal pulse (for example, an image signal) is sent from the data output unit 2A of the computer main body 1 to the display device 9 via the cable 7, the cable 7 is particularly leaked. Radio waves are easily emitted.

In such a case, a complementary signal is generated by the complementary signal generator 12 during the period (between pulses) where there is no information signal pulse, and the interpolation signal wiring 13 in the cable 7 is generated.
To the display device 9 via.

In this way, even if a leaked radio wave leaking from the cable 7 or the like is received and reproduced, the information (for example, an image) becomes a combination of the original information and the complementary information, and the content is discriminated. Things will be impossible.

(Operation of Configuration (2)) For example, in the case where the information signal pulse is an image signal pulse composed of RGB, the intensity of the complementary signal is changed by the combination of RGB, so that there are differences in screen color and darkness. Corresponding measures to prevent thieves can be taken.

(Operation of Structure (3)) An information signal pulse is transmitted from the data output section 2A to the display device 9 via the cable 7. In this case, the information signal pulse is RGB.
If the image signal is, the received signal is sent from the control circuit 11 to the display unit 10 and displayed.

In such a case, the information signal pulse is RGB
The above-mentioned three types of signal pulses are combined, and a complementary signal is generated for each of these signals and is independently transmitted to the display device 9 via the cable 7.

In this way, since each information signal pulse can be dealt with independently, it is possible to more reliably prevent information snooping. (Operation of Configuration (4)) As shown in FIG. 1B, a false information signal generation unit 14A is connected to the data output unit 2A, and a false information signal (for example, generated by using a random number) synchronized with the data output unit 2A is generated. Generated signal).

This false information signal is sent to the computer main body 1
Radiates as a radio wave from. In this way, the leaked radio waves due to the original information signal pulse (for example, the image signal pulse) and the leaked radio waves due to the newly radiated false information signal are mixed, and even if these radio waves are received, the information is stolen. It becomes impossible to see.

(Operation of Structure (5)) The false information signal generated by the false information signal generator 14A of FIG. 1B is fed through the same cable as the cable 7 for transmitting the original information signal pulse (eg, image signal pulse). To transmit.

In this case, since the original information signal pulse and the false information signal are transmitted in the same cable 7, it becomes more difficult to distinguish the leaked radio waves by each signal.

(Operation of Configuration (6)) In this case, an environment in which a plurality of computer systems are collectively arranged in the computer system group and radio waves leaking from the respective computer systems from the outside are mixed and received It is in.

In each computer system, different information signal pulses are transmitted independently,
The information signal pulses (eg image signal pulses) in each system are perfectly synchronized.

Therefore, even if the leaked radio waves are received, the leaked radio waves from the respective computer systems are overlapped, and it is impossible to determine the contents thereof.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. (Explanation of the First Embodiment) FIG. 2 is an explanatory view of the first embodiment of the present invention, in which the same reference numerals as those in FIGS. 1 and 8 indicate the same parts. Further, R is a terminating resistor, OR is an OR gate, 17 is a driver element (NOT gate), and 18 is a buffer.

In the first embodiment, in the computer main body 1,
This is an example in which the complementary signal generating circuit 12 is provided, and when there is no RGB image signal, a pseudo signal that complements the image signal is generated.
As shown in FIG. 2, the computer main body 1 and the display device 9 are connected by a cable 7, an image signal is sent from the computer main body 1 to the display device 9 via the cable 7, and an image is displayed on the display device 9.

The computer main body 1 includes a dot clock generator 3, an image data memory 5 and an R as in the conventional case.
GB dot generator 4, image data memory 5, driver 6
Although an image output unit composed of, etc. is provided, a complementary signal generating circuit 12 is further added.

The complementary signal generating circuit 12 is composed of an OR gate OR for inputting signals from respective RGB lines, a driver element 17, and a buffer 18. Further, the cable 7 is provided with a complementary signal wiring 13 for connecting between the complementary signal generating circuit 12 and the display device 9.

The driver element 17 of the complementary signal generating circuit 12 has the same structure as the driver element in the conventional driver 6, and these are provided in the same IC. The buffer 18 is provided on the output side of the driver 6 and has RGB
The same buffer provided for each image signal of is used.

Although the display device 9 is provided with a control circuit for each of the RGB image signals, a control circuit for controlling the complementary signal is provided separately from the control circuit.
Then, in the control circuit for the complementary signal, the complementary signal wiring 13 is connected to the terminating resistor R in advance.

The control for preventing the wiretapping due to the leaked radio waves will be described below. RGB transmitted from the computer body 1 to the display device 9 via the cable 7.
Each image signal is a pulse as shown in FIG. 2, and when it is displayed on the display unit 10 based on this signal, an image as shown in the figure is obtained.

In this case, each of the RGB image signals has, for example, a pulse when it is at the V ₁ level and no pulse when it is at the 0 level (this definition is used for explanation).
In this way, if any one of the RGB signals has a pulse, the output of the OR gate OR becomes the V ₁ level, and therefore the complementary signal generating circuit 12 outputs the complementary signal (M pulse). Not done.

However, when all the RGB signals have no pulse, the output of the OR gate OR becomes 0 level. Therefore, at this time, the complementary signal is output from the buffer 18,
It is sent to the display device 9 through the complementary signal wiring 13.

That is, when all the RGB image signals have no pulse, a pseudo signal (complementary signal) that complements the pulse signals is generated and transmitted from the computer body 1 to the display device 9. This complementary signal is displayed on the display device 9
Inside, it is consumed by the terminating resistor R.

In this case, a leaked radio wave is generated from the computer main body 1, the cable 7, etc., but the leaked radio wave due to the RGB image signal and the leaked radio wave due to the complementary signal M are mixed.

Therefore, the image signal contained in the leaked radio wave is at a substantially constant level V ₁ (actually, the intensity of the radio wave is slightly different when there is one RGB pulse and when there are two RGB pulses).

Therefore, when the leaked radio wave is received by the receiver 8, the reproduced image is an image in which the entire surface is similarly painted. That is, even if the leaked radio wave is received and the image information is reproduced, the image is a combination of the original image and the complementary image, and it is impossible to determine the content thereof.

(Explanation of the Second Embodiment) FIG. 3 is an explanatory view of the second embodiment, in which the same reference numerals as those in FIGS. 1 and 2 designate the same parts. Further, Tr ₁ is a transistor, R _{1 to} R ₅ are resistors, B _{1 to} B ₃ are buffers, and Vcc is a power source.

The second embodiment is an example in which the intensity of the complementary signal is changed by combining the RGB image signals. As shown in FIG. 3, a complementary signal generating circuit 12 is provided in the computer main body 1 to generate a complementary signal.

In this example, the complementary signal generating circuit 12
A transistor Tr ₁ , resistors R _{1 to} R ₅ , and a buffer B.
_{1 to} B ₃ and the driver element 17 are provided, and the collector of the transistor Tr ₁ is connected to the power source of + Vcc.

This circuit uses RGB signals as input signals, and the transistor Tr ₁ is controlled by the level of each RGB signal (whether or not there is a pulse). Then, a pseudo complementary signal M is output from the collector of the transistor Tr ₁ . This complementary signal is sent to the display device 9 as in the first embodiment.

In this case, as shown in FIG. 3, R, G,
If all B image signals are at level V ₁ (with pulse), B ₁ → R ₃ → R ₂ , B ₂ → R ₄ → R ₂ , B ₃ → R ₅
→ Current flows through the route of R ₂ and transistor Tr
_An electric current flows through the route of ₁ base → emitter → GND.

As a result, the collector current of the transistor Tr ₁ becomes large (maximum current) and a voltage drop occurs at the resistor R ₁ . Therefore, the collector of the transistor Tr ₁ is
It becomes almost the GND potential (level 0). Therefore, at this time, the pseudo complementary signal M output from the collector of the transistor Tr ₁ becomes almost 0 level.

Next, when the R and G signals are at level V ₁ (with pulse) and the B signal is at level 0 (without pulse),
No current flows in the route of B ₃ → R ₅ . Therefore, the base current of the transistor Tr ₁ is reduced accordingly and the collector current is also reduced. As a result, the collector potential of the transistor Tr ₁ becomes higher than that in the above case.

Further, R is level V ₁ (with pulse),
When G and B are at level 0 (no pulse), no current flows in the paths B ₂ → R ₄ and B ₃ → R ₅ , but only in the path B ₁ → R ₃ . As a result, the collector current of the transistor Tr ₁ is further reduced and the collector potential is also increased.

All the RGB signals have level 0.
When (no pulse), since the base current of the transistor Tr ₁ disappears, the collector voltage of the transistor Tr ₁ is the same + Vcc power supply voltage.

As described above, the intensity of the complementary signal is changed according to the state of each of the RGB image signals (with or without pulse), and the signal is transmitted from the computer main body 1 to the display device 9. The level of the image signal included in the radio wave leaking from the cable 7 and the like is set to a substantially constant level.

Therefore, it is possible to take measures against the difference in screen color and the density. (Explanation of Third Embodiment) FIG. 4 is an explanatory view of the third embodiment, in which the same reference numerals as those in FIGS. 1 to 3 designate the same parts.

The third embodiment is an example in which a complementary signal is generated for each of the RGB image signals. As shown in FIG. 4, the complementary signal generation circuit 12 is composed of a driver element 17 provided in the driver 6 and a buffer 18.

In this case, a series circuit of the driver element 17 and the buffer 18 is formed for each of R, G, and B, and the pseudo complementary signals MR, MG, and MB are generated from each buffer 18, and the display device 9 is produced. Send to.

The cable 7 has three complementary signal wirings 1 for transmitting complementary signals for each of RGB.
3 is provided. Therefore, the terminating resistor R is also connected to each wiring 13.

Now, if the image signal R is level V ₁ (with pulse), the complementary signal MR corresponding to this signal becomes level 0. If the image signal R is level 0 (no pulse), the complementary signal MR is level V ₁ . In this way, the complementary signal MR becomes a signal obtained by inverting the image signal R.

Similarly for the image signals G and B, the complementary signal MG is a signal obtained by inverting the image signal G, and the complementary signal M
B is a signal obtained by inverting the image signal B. Thus, R
Since a complementary signal is generated for each GB signal, the original image signal appears to be continuous from the outside. Therefore, even if leaked radio waves are received by the receiver 8, a correct image cannot be reproduced, and it is possible to reliably prevent information snooping.

(Explanation of Fourth Embodiment) FIG. 5 is an explanatory view of the fourth embodiment, in which the same reference numerals as those in FIGS. 1 to 4 designate the same parts. Further, 19 is a driver for converting false image data into RGB signals, 20 is a random number generator, and 21 is a random number R
Decoder for converting into 3 bits of GB, 22 is an antenna.

The fourth embodiment is an example in which a false image signal using random numbers is generated and a false radio wave is emitted from the antenna. As shown in the figure, the computer main body 1 is provided with the false image signal generator 14 and the antenna 22.

The false image signal generator 14 is provided with a random number generator 20, a decoder 21 and a driver 19, and the dot clock generator 3 is connected to the random number generator 20. Also,
The driver 19 has an input side connected to the RGB dot generator 4 and an output side connected to the antenna 22.

In this case, the driver 19 has the same configuration as the driver 6. The random number generator 20 is assumed to generate a random number of 0 to 7, and the decoder 21
Then, the generated random number is decoded to generate a random 3-bit RGB signal, which is supplied to the driver 21.

In the driver 6, each of the RGB signals output from the RGB dot generator 4 is on / off controlled by the image data output from the image data memory 5.
As a result, RGB image signals are transmitted to the display device 9.

Separately from this, in the driver 19, RGB
Each of the RGB signals output from the dot generator 4 is on / off controlled by the signal output from the decoder 21 and supplied to the antenna 22.

That is, the random 3-bit RGB signal decoded by the decoder 21 is combined with the signal of the RGB dot generator 4 and converted into an RGB signal at exactly the same timing as the image signal, which becomes a false image signal. ..
The false image signal output from the driver 19 is
It is supplied to the antenna 22 and radiated as a radio wave.

As described above, by generating a plurality of synchronized false image information and radiating the radio wave from the antenna 22, the leaked radio wave including the original image data and the newly generated false image information are generated. It becomes impossible to separate and receive the leaked radio waves including.

Therefore, even if the receiver 8 receives the leaked radio wave and reproduces the image information, the image is a combination of the original image and the false image, and the contents cannot be discriminated. (Explanation of the fifth embodiment) FIG. 6 is an explanatory view of the fifth embodiment, in which the same reference numerals as those in FIGS. Further, reference numeral 15 indicates wiring for false signals.

The fifth embodiment is an example in which a false image signal using a random number is generated and transmitted to the display device 9 via a cable. In this example, the false image signal generator 14 is provided with a random number generator 20, a decoder 21, and a driver 19.

Then, the output of the driver 19 is connected to the display device 9 through the wire 15 for false signal.
This false signal wiring 15 uses three RGB lines,
In the display device 9, each is connected to a terminating resistor R.

This example is the same as the fourth example until the driver 19 generates a false image signal.
The false image signal is transmitted to the display device 9 for each RGB by using the wiring 15 for the false signal.

The leaked radio waves thus generated are generated from the same place as the leaked radio waves caused by the original image signal. That is, since the leaked radio waves caused by the original image signal and the leaked radio waves caused by the false image signal are generated under the same condition, it becomes more difficult to distinguish the radio waves of the respective signals.

(Explanation of Sixth Embodiment) FIG. 7 is an explanatory view of the sixth embodiment, in which the same reference numerals as those in FIGS. 1 to 6 designate the same parts. Further, 23 is an image control unit, SW is a switch, and I
N indicates an input terminal and OUT indicates an output terminal.

The third embodiment is an example of preventing radio wave snooping in a computer system group in which a plurality of computer systems are collectively arranged. System S as shown
Each of the systems ₁ to S ₃ (computer system) is provided with an image output unit including a dot clock generator 3, an image control unit 23 and the like.

Then, the image output sections of the respective systems are connected by a cable so that the image signals output from the respective systems are synchronized. In this case, one of the systems is used as a reference to synchronize the other systems.

In the illustrated example, the dot clock generated by the dot clock generator 3 of the system S ₁ and the horizontal synchronizing signal H and the vertical synchronizing signal V generated by the image controller 23 are connected to another system S by a cable. ₂ 、 S ₃ etc.

In the image output section of each system, image data is created using the same dot clock and horizontal and vertical synchronizing signals and transmitted to the display device via the cable 7. Then, the display is performed on the display unit 10. in this case,
The contents of the image data output from each system are independent, but they are all synchronized signals.

For example, it is assumed that the system S ₁ has leaked radio waves, the system S ₂ has leaked radio waves, and the system S ₃ has leaked radio waves. In such cases,
Since the respective leaked radio waves are mixed, even if received by an external receiver, the contents reproduced from the images cannot be discriminated.

In this way, it is possible to prevent image snooping without generating a false image signal. In particular, the effect increases as the number of systems increases. It can also be realized at low cost. The switch SW in the figure is a switch that switches when each system operates independently.

(Other Embodiments) The embodiments have been described above, but the present invention can be implemented as follows. (1) It is applicable not only to image signals but also to other serial data signals.

(2) Not only the leaked radio waves from the cable,
It is possible to reliably prevent snooping from leaking radio waves from the computer body or terminal devices.

[0087]

As described above, the present invention has the following effects. (1) With a simple configuration, it is possible to prevent the image information contained in the leaked radio waves from being sniffed. Therefore, the security of the computer system can be improved and
The cost is also low.

(2) Especially, a leaked radio wave is apt to be emitted from the cable connecting the computer main body and the display device. However, not only the leaked radio wave from this portion but also the leaked radio wave generated from the computer main body can be surely imaged. Information snooping can be prevented.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is an explanatory diagram of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a second embodiment.

FIG. 4 is an explanatory diagram of a third embodiment.

FIG. 5 is an explanatory diagram of a fourth embodiment.

FIG. 6 is an explanatory diagram of a fifth embodiment.

FIG. 7 is an explanatory diagram of a sixth embodiment.

FIG. 8 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Computer Main Body 2 Image Output Section 7 Cable 9 Display Unit 10 Display Section 11 Control Circuit 12 Complementary Signal Generation Circuit 13 Complementary Signal Wiring 14 False Image Signal Generation Section

Claims (7)

[Claims] 1. A radio wave sniffing prevention method for preventing information snooping due to radio waves leaking from a computer system, comprising a data output section (serial number) for outputting a serial information signal pulse provided in a computer main body (1). 2A) is connected to a complementary signal generating circuit (12) for detecting the presence or absence of the output of the information signal pulse and generating a pseudo complementary signal pulse (M) capable of complementing the information signal pulse, The same signal path as the information signal pulse (7) is generated by generating the complementary signal pulse in a period in which no signal pulse is output.
Radio wave snooping prevention method characterized by transmitting over the air. 2. In the complementary signal generating circuit (12), the intensity of the complementary signal pulse (M) is determined by a plurality of pulses (RGB) forming the information signal pulse.
The method of preventing radio wave snooping according to claim 1, wherein the method is changed according to the combination of 3. The complementary signal generating circuit (12) comprises a plurality of pulses (RGB) forming the information signal pulse.
On the other hand, a complementary signal pulse (MR, MG, MB) is independently generated, and the complementary signal pulse is independently transmitted through the same path (7) as the information signal pulse. The method of preventing radio wave snooping according to item 1. 4. A radio wave sniffing prevention method for preventing information snooping due to radio waves leaking from a computer system, comprising a data output section (2A) for outputting serial information signal pulses provided in a computer body (1). ) Is connected to a false information signal generation unit (14A) that generates a false information signal synchronized with the information signal pulse, and the false information signal generated by the false information signal generation unit (14A) is radiated as a radio wave. A radio wave snooping prevention method characterized by outputting. 5. A radio wave snooping prevention system for preventing information snooping due to radio waves leaking from a computer system, comprising a data output section (serial number) for outputting a serial information signal pulse provided in a computer body (1). 2A) is connected to a false information signal generation unit (14A) that generates a false information signal synchronized with the information signal pulse, and the false information signal generated by the false information signal generation unit (14A) is replaced with the original false information signal. A radio wave snooping prevention method characterized in that it is transmitted through the same path (7) as the information signal pulse. 6. A plurality of computer systems (S₁, S
₂, S₃...)
It is a radio wave sniffing prevention method that prevents the snooping of information from the group.
Are installed in the main body (1) of each computer system.
A data output section (2 that outputs realistic information signal pulses
A) are connected to each other, and the synchronization signal for creating the information signal pulse is
Computer system (S ₁, S₂, S₃...) common
Information signal pulse output from each computer system
Radio wave snooping prevention method characterized by synchronizing the. 7. The radio wave sniffing prevention system according to claim 1, wherein the information signal pulse is an image signal.