JP4673147B2 - Information leakage prevention signal output control method and information leakage prevention signal output control apparatus - Google Patents

Description

  The present invention relates to an information leakage prevention technique for preventing leakage of information due to reception and reproduction of electromagnetic waves radiated from information equipment.

  Conventionally, unnecessary electromagnetic waves radiated unintentionally from information devices such as computers and communication devices are generated from electrical signals in the information device or in an interface connecting the information devices. Contains image information. In the case of a known information interface, the image information itself can be reproduced by receiving and reproducing the unnecessary electromagnetic wave.

  FIG. 16 shows an example 100 of an analog RGB signal generation circuit used for transmitting a computer image signal. As shown in FIG. 17, the signal includes a vertical synchronizing signal (V), a horizontal synchronizing signal (H), and an RGB signal (horizontal line dot luminance signal) as signals of the circuit 100, and the vertical synchronizing signal ( V), a horizontal synchronizing signal (H), and a red component (R), a green component (G), and a blue component (G) of the RGB signal are transmitted. As shown in FIG. 17, the signal displayed as image information is an analog signal corresponding to the luminance of the dots, and the period of the luminance column corresponds to the period of the dot clock signal.

  In order to convey information, the electrical signal has periodicity according to various image resolution standards such as CGA, EGA, VGA, SVGA, QVGA, XGA, WXGA, SXGA, and UXGA, and a synchronization signal is transmitted. When unnecessary radio waves including information are received by the receiver of the reproducing apparatus 200 as shown in FIG. 18 and input to the RGB signal of the display through the filter and the horizontal / vertical synchronizing signal is input, an image can be reproduced on the display.

  Further, in the reproduction apparatus 200A as shown in FIG. 19, the image can be reproduced by A / D converting the signal, finding the synchronization signal on the software, and returning the serial signal at the interval of the horizontal synchronization signal.

Therefore, as a conventional technique, a method for preventing information leakage by generating a false signal as a countermeasure has been devised. For example, as shown in FIG. 22A, there are known a method of creating a mask signal for RGB signals, a method of randomly assigning a time delay to RGB signals as shown in FIG. ).
JP-A-6-83296

  However, in the above-described prior art, as a means for preventing information leakage due to leaked electromagnetic waves, the level of leaked electromagnetic waves can be reduced by inserting a filter circuit into a computer interface cable (such as a serial signal interface) as shown in FIG. Pressing is also done.

  However, this method can only deal with those that are connected with an interface cable. For example, a cable exists between a desktop computer and a display, but measures could not be taken with an integrated laptop computer. Further, since the information itself is transmitted through the cable, it is impossible to reliably remove the information from the leaked electromagnetic wave, and even if a filter is attached to the unshielded casing, the leaked electromagnetic wave is not always reduced.

  Further, as shown in FIG. 21, there is known a method for reducing leakage electromagnetic waves by providing an electromagnetic shield on the computer casing itself. However, although it is possible to reliably reduce electromagnetic waves, the shield is expensive. In the case of information communication equipment, there is an interface cable for transmitting and receiving information, and it has been very difficult to shield it reliably.

Further, in the method of creating the mask signal as shown in FIG. 22A, the radiated electromagnetic wave is generated by the differential component (di / dt) of the current signal of the RGB signal or the differential component (dv / dt) of the voltage signal. Because the signal pattern close to is radiated, the actual time waveform of the leaked electromagnetic wave becomes a waveform as shown in FIG. 22B, and the synthesized leaked electromagnetic wave becomes a waveform as shown in FIG. The signal is reproduced by adding an appropriate filter circuit or integration circuit.

  Further, if a false signal is randomly generated as in the method shown in FIG. 23, the S / N ratio of the receiver is deteriorated and reproduction can be made difficult. However, as shown in FIG. By applying a synchronization signal such as a vertical synchronization signal from the signal and taking a time average, or by taking a signal sequence of several screens and performing autocorrelation processing, it is possible to remove random components, and the signal is reproduced. It was.

  The present invention has been made in view of such problems, and an object thereof is to prevent leakage of information due to reproduction of electromagnetic waves radiated from information equipment.

The present invention according to claim 1 is an output level variable type information leakage prevention device for preventing leakage of electromagnetic waves radiated from information equipment and preventing data information contained therein from being reproduced and leaked. A clock signal extraction unit that is connected to an information signal interface provided in the information device and extracts a clock component of the information signal, and a first pseudo clock that is synchronized with the clock component extracted by the clock signal extraction unit A clock signal generator for generating a second pseudo clock signal having a signal or a phase difference designated in advance with respect to the first pseudo clock signal, and the pseudo clock generated by the clock signal generator signal n following differential signal (n: integer), de Yuti ratio of the pseudo clock signal signals with a reduced duty ratio of the pseudo clock signal A signal for which the offset position in the amplitude direction of the signal having been reduced is changed, a prevention signal generation unit that generates one or more, and an antenna that is installed in or around the information device and that can emit electromagnetic waves One or more means for applying a signal to a circuit pattern, various cables connected to the information device, an internal circuit of the information device, and applying a signal to one or more locations of a metal casing of the information device The prevention signal output unit that outputs the prevention signal generated by the prevention signal generation unit as the prevention signal, the radiated electromagnetic waves inside or around the information device, and observed on various cables connected to the information device Leakage signal that receives one or more of a conductive signal, an induced voltage signal on an internal circuit board of the information device, and an induced voltage signal observed at a metal casing of the information device A receiving unit, on the basis of the said observation signal measured by the leakage signal receiving unit comprises a, a protection signal adjusting section for adjusting the output level of the protection signal output from the protection signal output unit.

  Further, the present invention according to claim 2 is the invention according to claim 1, wherein the prevention signal output unit is configured such that the prevention signal output unit is radiated electromagnetic waves inside or around the information device, and conduction observed on various cables connected to the information device. Measuring one or more of a sex signal, an induced voltage signal on an internal circuit board of the information device, and an induced voltage signal observed at a metal casing of the information device instead of the leakage signal receiving unit, and measuring Based on the observed signal, the prevention signal adjustment unit adjusts the output level of the prevention signal output from the prevention signal output unit.

According to a third aspect of the present invention, in the first aspect, the prevention signal adjusting unit is configured to output the prevention signal before outputting the prevention signal based on a result of the leakage signal reception unit measuring the observation signal. Determination means for determining an output level of the prevention signal from the prevention signal generation unit to the prevention signal output unit, or the prevention signal output unit from the prevention signal generation while the leakage signal reception unit measures the observation signal Any one of the determination means for adaptively determining the output level of the prevention signal is selected.

According to a fourth aspect of the present invention, in the first aspect, the information signal is generated from the RGB signal and horizontal / vertical synchronization signal of the information device, or the RGB signal and horizontal / vertical synchronization signal of the information device. And the clock component is a dot clock signal of the information device.

  Further, in the present invention described in claim 5, when the information signal is RGB and horizontal / vertical synchronization signal of the information device according to claim 1 or 4, the clock signal extraction unit and the clock signal generation unit Instead of generating a pseudo clock signal from the dot clock signal of the information device, a pseudo clock signal is generated from one or more of the R signal, G signal, and B signal of the information device.

According to a sixth aspect of the present invention, there is provided an output level variable type information leakage prevention method for preventing leakage electromagnetic waves radiated from information equipment from being decoded and preventing data information contained therein from being reproduced and leaked. The clock signal extraction unit connected to the information signal interface provided in the information device extracts the clock component of the information signal, and the clock signal generation unit extracts the clock component from the clock signal extraction unit. Generating a first pseudo clock signal synchronized with the clock component or a second pseudo clock signal having a phase difference designated in advance with respect to the first pseudo clock signal; and a prevention signal generation unit in, n order differential signal of the clock signal generating pseudo clock signal generated by the unit (n: integer), the pseudo clock signal Signal with a reduced duty ratio of No., the step of generating a signal for changing an offset position in an amplitude direction of the signal with reduced de Yuti ratio of pseudo clock signal, any one or more of, prevention signal output unit In, the signal equipment to the antenna and circuit pattern which can be radiated electromagnetic waves installed in or around the information equipment, various cables connected to the information equipment, the internal circuit of the information equipment, the metal of the information equipment A step of outputting the prevention signal generated by the prevention signal generation unit as the prevention signal by one or more means of applying a signal to one or more locations of the housing; Radiation electromagnetic waves inside or around information equipment, conductive signals observed on various cables connected to the information equipment, internal circuit base of the information equipment A step of receiving at least one of the induced voltage signal and the induced voltage signal observed at the metal casing of the information device; and the observation signal measured by the leakage signal receiver at the prevention signal adjustment unit And adjusting the output level of the prevention signal output from the prevention signal output unit.

  According to a seventh aspect of the present invention, in the sixth aspect of the present invention, in the prevention signal output unit, the radiated electromagnetic wave inside or around the information device, the conduction observed on various cables connected to the information device. Measuring at least one of a sex signal, an induced voltage signal on an internal circuit board of the information device, and an induced voltage signal observed at a metal casing of the information device instead of the leakage signal receiving unit; The prevention signal adjustment unit adjusts the output level of the prevention signal output from the prevention signal output unit based on the measured observation signal.

Further, according to the present invention of claim 8, in the prevention signal adjustment unit according to claim 6, based on a result of the leakage signal reception unit measuring the observation signal, the output of the prevention signal is performed in the prevention signal adjustment unit. Determining the output level of the prevention signal from the prevention signal generation unit to the prevention signal output unit, or from the prevention signal generation to the prevention signal output unit while the leakage signal reception unit measures the observation signal Selecting one of the steps of adaptively determining the output level of the prevention signal.

According to a ninth aspect of the present invention, in the sixth aspect, the information signal is generated from an RGB signal and a horizontal / vertical synchronizing signal of the information device, or an RGB signal and a horizontal / vertical synchronizing signal of the information device. And the clock component is a dot clock signal of the information device.

  Further, in the present invention of claim 10, when the information signal is RGB or horizontal / vertical synchronization signal of the information device according to claim 6 or 9, the clock signal extraction unit and the clock signal generation unit Instead of generating a pseudo clock signal from the dot clock signal of the information device, a step of generating a pseudo clock signal from any one or more of the R signal, G signal, and B signal of the information device is executed.

  According to the present invention, information leakage due to reproduction of electromagnetic waves radiated from information equipment can be prevented.

<First Embodiment>
FIG. 1 is an example of an output level variable information leakage prevention apparatus and an information leakage prevention signal output method according to an embodiment. In FIG. 1, the information leakage prevention apparatus 1, the clock signal extraction unit 11, the clock signal generation unit 12, the prevention signal generation unit 13, the prevention signal generation circuit 131, the output amplifier unit 132, and the prevention signal output unit 14. (141, 142,..., 14n), leakage signal receiving unit 15, leakage signal receiving sensor unit 16, prevention signal adjusting unit 17, information device 2, and serial signal interface (information signal interface) of information device 2 ) 3 is shown. In FIG. 1, the ground line and the ground terminal of the serial signal interface 3 and the prevention signal output unit 14 are omitted.

  FIG. 2 shows an example of a measurement image of the leaked electromagnetic wave of the dot luminance signal leaked from the luminance column, dot luminance signal sequence, serial signal interface 3 and the like of the information device 2.

  In FIG. 1, a clock signal extraction unit 11 receives an RGB signal, a horizontal synchronization signal (H), and a vertical synchronization signal via a serial signal interface 3 such as an external image signal port equipped in an information device 2 such as a notebook computer. When (V) is received, a dot clock signal that is the highest frequency of the serial signal is extracted from the received signal. Instead of the dot clock signal of the serial signal, a method of extracting a fluctuation pattern of any one of the R signal, G signal, and B signal may be used.

  Next, the clock signal generation unit 12 determines whether the pseudo clock signal (first pseudo clock signal) synchronized with the dot clock signal extracted by the clock signal extraction unit 11 or the first pseudo clock signal in advance. The pseudo clock signal (second pseudo clock signal) having the designated phase difference is output to the prevention signal generation unit 13.

Prevention signal generation circuit 131 of the prevention signal generator 13, n order differential signal of the pseudo clock signal from the clock signal generation element 12 (n: integer), similar to signal to the differential signal of the pseudo clock signal, the pseudo clock signal signal changing the offset position of the amplitude direction of de Yuti ratio reduced the signal, any one or more generated by a protection signal, the output amplifier 132 to prevent the signal output section 14 output level is adjusted by Sent to.

Incidentally, prevention signal generation circuit 131, in the case of generating a differential signal of the pseudo clock signal when decreasing the duty ratio of the differentiating circuit, pseudo clock signal may be utilized, such as the duty ratio conversion circuit. Also, when generating a signal for changing an offset position in an amplitude direction of the signal with reduced de Yuti ratio, in addition to de Yuti ratio converting circuit, or a method in which a combination of offset circuit.

  One or more prevention signal output units 14 are installed in or around the information device 2, apply signals to an antenna or circuit pattern capable of emitting electromagnetic waves, various cables connected to the information device 2, and the inside of the information device 2. Any one or more methods of applying a signal to one or more locations such as a circuit and a metal casing of the information device 2 can be used alone or in combination. It is possible to make it difficult to efficiently decode and decode leaked electromagnetic waves radiated in the direction.

  Here, examples of the prevention signal output unit 14 by electromagnetic radiation include a monopole antenna, a dipole antenna, a triaxial orthogonal dipole antenna, a loop antenna, a triaxial orthogonal loop antenna, a biconical antenna, and a coil capable of electromagnetic radiation. Alternatively, conductor cables, circuit patterns, and the like having a form similar to these antennas can be used, and the method of radiating the prevention signal to the space has the effect of making it difficult to receive and decode the leakage electromagnetic waves of the information device 2 from the outside.

  3 is classified into a loop type antenna 141 (FIG. 3A) and a dipole type antenna 142 (FIG. 3B) around the display unit 21 of the information device 2 (inside or on the surface of the display frame unit 22). This is an example when a possible conductor cable is installed, and it is possible to efficiently receive and decode leaked electromagnetic waves from outside without installing a separate antenna for preventing signal emission around the information device 2 or inside the main body. This is an example that can be made difficult.

  In addition, as an example of applying a prevention signal to one or more locations such as various cables connected to the information device 2, the internal circuit of the information device 2, and the metal housing of the information device 2, A preventive signal is applied by wrapping a conductor cable around the serial signal interface 3 or power line, and a preventive signal is applied by arranging the conductor cable parallel to the serial signal interface 3 or power line of the information apparatus 2. Install a current probe on the serial signal interface 3 or power line, etc. to apply the prevention signal, apply the prevention signal directly to the internal circuit of the information device 2, directly apply the prevention signal to the metal casing of the information device 2 For example, a method of applying a voltage to the electrode can be considered.

  And it has the effect of making leakage electromagnetic waves difficult to receive and deciphering from the outside by electromagnetically coupling or electrostatically coupling a prevention signal to the leakage electromagnetic wave radiation location of the information equipment 2. The prevention signal output unit 14 is simplified by using the circuit pattern or element in the prevention signal generation unit 13 as an output unit of the prevention signal such as a radiating antenna without being installed separately. A method of configuring may be used.

  The leakage signal receiving unit 15 radiates electromagnetic waves (first observation signal) inside or around the information device, and conductivity observed on various cables connected to the information device via the leakage signal receiving sensor 16. Signal (second observation signal), induced voltage signal on the internal circuit board of the information device (third observation signal), induced voltage signal (fourth observation) observed at the metal casing of the information device 2 One or more of (signal).

  The leak signal receiving sensor 16 is a monopole antenna, a dipole antenna, a triaxial orthogonal dipole antenna, a loop antenna, a triaxial orthogonal loop antenna, or an electromagnetic field measurement when detecting electromagnetic waves radiated into the space. A probe, a biconical antenna, an electronic element capable of measuring electromagnetic waves such as a coil or a capacitor, or a conductor cable or a circuit pattern having a form similar to these antennas can be used.

  Further, when detecting conductive signals on various cables connected to the information device 2, a current probe is used. When detecting an induced voltage induced on the circuit board or metal casing of the information device 2, a voltage probe is used. Etc., or one or more sensors can be installed at the same time.

  Based on the observation signal measured by the leakage signal receiving unit 15, the prevention signal adjusting unit 17 determines that the intensity of the prevention signal is a leakage signal (radiated electromagnetic wave to space, conductive induction signal to various cables, internal circuit, etc. From the prevention signal output unit 14 so as to be equal to or greater than the intensity (maximum absolute intensity in an arbitrary time interval, average intensity in an arbitrary time interval, average power intensity in an arbitrary time interval, etc.) It has a function of adjusting the output level of the output prevention signal.

  In addition, the adjustment process measures the output level of the leakage signal from the information device 2 before the output of the prevention signal, and based on the result, the prevention signal output level from the prevention signal generation unit 13 to the prevention signal output unit 14 (A first output level adjustment method of the prevention signal) and a method of adaptively determining the output level of the prevention signal while measuring the output level of the leakage signal from the information device 2 (the prevention signal first level). 2 output level adjustment method) can be selected.

  In addition, in the second method for adjusting the output level of the prevention signal, a leakage signal from the information device 2 (radiated electromagnetic wave to the space, conductive induction signal to various cables, induction voltage to the internal circuit board, etc.) The total value of the prevention signals from the prevention signal output unit 14 is detected by the leakage signal reception sensor unit 16.

  In this process, the intensity of the prevention signal is greater than or equal to the intensity of the leaked signal from the information device 2 (maximum absolute intensity in any time interval, average intensity in any time interval, average power intensity in any time interval, etc.) In addition to the setting, the prevention signal adjustment unit 17 adjusts the output level of the prevention signal from the prevention signal output unit 14 so that the electromagnetic wave intensity radiated to the space is equal to or less than the electric field strength regulation such as VCCI. can do.

  When the prevention signal application means is a conductive induction signal on various cables or an induction voltage of a circuit board or metal housing, measure the relationship between the prevention signal application intensity and the radiated electromagnetic wave intensity in advance. The electromagnetic wave intensity at the reference point may be adjusted by adjusting the electromagnetic wave intensity at the reference point to be equal to or lower than the electromagnetic field regulation, or by observing the electromagnetic wave intensity radiated into the space at the leakage signal receiving sensor unit 16. Any of the methods of adjusting so as to be below the field regulation can be adopted, and the cooperation processing of the output amplifier 132 and the prevention signal adjusting unit 17 can be realized by an auto gain controller or the like.

  With the configuration described above, there is an effect that it is difficult to receive and decode leaked electromagnetic waves radiated from the information device 2 from the outside with a simple device configuration.

  Next, the operation of the information leakage prevention apparatus 1 described above will be described with reference to FIG. FIG. 4 is an example in which the prevention signal generation unit 131 uses a first-order differentiation circuit. The information leakage prevention apparatus 1 extracts the dot clock signal sequence b1 from the dot luminance signal a1 acquired from the information device 2. At the same time as generating the pseudo clock signal, the prevention signal d1 is generated by differentiating the pseudo clock signal.

From the information device 2, via a serial signal interface 3 or the power supply line, although the dot luminance signal leakage electromagnetic wave c1 characteristics have close to the differential waveform of the dot brightness signal a1 is emitted at the periphery of the information device 2 If the prevention signal d1 is output so as to have a higher intensity than the leakage electromagnetic wave c1, the prevention signal d1 will be observed as the leakage electromagnetic wave e1 when combined, so that it is impossible to receive and decode the leakage electromagnetic wave c1. It becomes possible.

  In this example, an example of a first-order differentiation circuit is shown, but even when n is 2 or more, the same operation can be easily performed. Instead of the dot clock signal, the R signal, the G signal, A method of extracting the fluctuation pattern of any one of the B signal sequences may be used.

FIG. 5 shows an example in which leakage electromagnetic waves are prevented when an N- fold period circuit is used, and a prevention signal d2 that is a double period of the pseudo clock signal generated from the extracted dot clock signal b1 is generated and output. When the prevention signal d2 is output in the vicinity of the information device 2 so as to be higher than the leakage electromagnetic wave c1, the electromagnetic wave of the prevention signal d2 is received as the leakage electromagnetic wave e2 when combined, and thus leaks from the information device 2. It becomes difficult to receive and decode the electromagnetic wave c1.

  Further, a method of generating and outputting a signal having both positive and negative amplitudes by shifting the offset position of the prevention signal d2 in the amplitude direction (FIG. 5 (d′ 2) is an example of a prevention signal in which the offset position is shifted), and offset. A method of generating and outputting a signal subjected to random number processing so that the amplitude fluctuation of the signal whose position is shifted does not always become positive and negative may be used.

  Note that the serial signal interface of the information device 2 includes a conductor cable wound around the serial signal interface 3 of the information device 2 and a power supply line, and the conductor cable is arranged in parallel with the serial signal interface 3 of the information device 2 and the power supply line. When the prevention signal is output by means such as installing a current probe on the power line 3 or the power line, that is, when the dot luminance signal is suppressed at a stage before spatial emission, the prevention target signal is the original dot luminance. A signal component having characteristics closer to those of the original signal, not a differential component of the signal, is targeted.

  Therefore, when the prevention signal is not applied due to spatial antenna radiation, the dot clock signal itself or a method of applying a clock signal that is doubled in frequency or more is an electromagnetic wave at the installation location of the information device 2 or the like. Depending on the conditions due to leakage, it is more effective.

  FIG. 6 shows an example in which the prevention signal generation circuit 131 uses the duty ratio conversion circuit to prevent leakage electromagnetic waves, and generates the prevention signal d3 in which the duty ratio of the pseudo clock signal generated from the extracted dot clock signal b1 is reduced. 4 can generate a signal having an effect similar to that of the differentiation circuit of FIG. 4, that is, a waveform having a variation pattern similar to the leaked electromagnetic wave radiated from the information device 2, so that the same effect can be realized with an easy electronic circuit. can do.

  In addition, the offset position in the amplitude direction of the prevention signal d3 is shifted to generate and output a signal having both positive and negative amplitudes, and further, the amplitude fluctuation of the signal whose offset position is shifted must be alternately positive and negative. A method of generating and outputting a signal to which random number processing has been added may be used.

  Note that a method using a random signal generation circuit or the like can also be used to generate a prevention signal by applying a random fluctuation pattern signal (white noise) to the prevention signal shown in FIGS. A method of making the leaked electromagnetic wave radiated from the device 2 more disturbed and making it difficult to receive and decode from a remote place may be used.

  In addition to applying a random signal, frequency modulation is performed using a modulation circuit, so that reception decoding from the outside can be made more difficult. Further, the pseudo clock signal is not completely synchronized with the original luminance signal a1, but can be set as a pseudo clock signal by setting a phase difference designated in advance. For example, the pseudo clock signal is extracted by the clock signal extraction unit 11 By generating a pseudo clock signal having a phase difference of 180 degrees with respect to the dot clock signal generated by the prevention signal generator 12, it is possible to have an effect of suppressing the leaked electromagnetic wave radiated into the space.

  FIG. 7 shows an example in which the luminance signal sequence is reproduced by the reproducing apparatus 200A shown in FIG. 19 when the present embodiment is applied. (A) is when the output level of the prevention signal is not adjusted, and (b). Indicates that when the output level of the prevention signal is adjusted, the intensity change of the luminance signal sequence is almost constant, and it can be confirmed that the information reproduction is difficult. In this example, it can also be confirmed that the latter in which the output level is adjusted has a smaller signal intensity, making it difficult to reproduce information from the outside more efficiently.

  Therefore, according to the information leakage prevention apparatus of the embodiment, the dot clock is extracted via the serial signal output port of the information device 2, and the prevention signal such as the differential component of the pseudo clock is generated and prevented in various forms. Based on unnecessary electromagnetic waves radiated from information communication devices such as computers and communication devices, a third party can adjust the level of the prevention signal according to the output intensity of the leakage signal from the information device at the same time that the signal is output. It is possible to reliably prevent unauthorized use by intercepting and reproducing information from a remote location.

  In particular, in this embodiment, the effect can be exhibited in a notebook personal computer or the like in which the computer main body and the display are integrated without having an interface. Further, since it can be realized with a simple circuit configuration, it is possible to prevent an increase in cost as in the case of using an electromagnetic shield.

  By the way, in general, unnecessary electromagnetic waves are regulated in electromagnetic intensity as shown in FIG. 8, for example, so as not to affect the radio frequency used in communication and broadcasting. It is possible to adjust the strength of the prevention signal to be within the regulation range by observing the leakage signal from the signal, feeding back the result, and determining the output of the prevention signal (FIG. 9 (When the prevention signal is applied, the prevention signal electromagnetic wave is within the regulation).

<Second Embodiment>
FIG. 10 is another example of the information leakage prevention apparatus 1 according to the embodiment. In FIG. 10, 18 is a directional coupler. In this example, the information leakage prevention apparatus 1 serves as both a prevention signal output means and a means for grasping the reception intensity of the leakage signal leaked from the information equipment 2. The prevention signal output unit 13 is connected by the directional coupler 18. Since the output signal (prevention signal) and the input signal to the leakage signal receiving unit 15 can be input and output by the prevention signal output unit 14, the configuration of the information leakage prevention apparatus 1 is simplified.

<Third Embodiment>
FIG. 11 shows another example of the information leakage prevention apparatus according to the embodiment. In FIG. 11, a serial signal distribution circuit 19 is shown. The example of FIG. 11 is applied when the computer main body and the image display unit (display) are not integrated like a desktop computer, and a distribution circuit 19 is added to the information leakage prevention apparatus 1 to display This is an example in which a function for passing an image signal is provided. Therefore, by adopting the configuration example of FIG. 11, even when the display is not integrated with the main body, the effect of making it difficult to receive and decode leaked electromagnetic waves radiated from the information device 2 from the outside.

<Fourth embodiment>
FIG. 12 is another example of the information leakage prevention apparatus according to the embodiment. In this example, the function of the information leakage prevention device 1 is incorporated in the information device 2, and a dot clock signal can be acquired from the image signal generation circuit 30 of the information device 2, and the information leakage prevention device is connected to the information device 2. The same effect can be obtained even when it is built in the information device 2 without externally attaching 1.

<Fifth embodiment>
FIG. 13 is another example of the information leakage prevention apparatus according to the embodiment. FIG. 13 shows an example in which the function of the information leakage prevention device 1 is built in the information device 2. Since the dot clock signal can be directly acquired from the dot clock signal generation unit of the information device 2, the information leakage prevention device 1. Need not include a clock signal extraction unit and a clock generation unit.

Therefore, according to the information leakage prevention apparatus according to this embodiment, directly obtains the dot clock signal from the information device such as a computer, a differential signal of the pseudo clock signal, the signal generated by a method of reducing the duty ratio of the clock signal , the signal for changing the offset position of the amplitude direction of the signal with reduced de Yuti ratio of the clock signal to generate one or more, for the information device 2 can output a protection signal of the leakage electromagnetic wave, in the information equipment 2 The same effect can be obtained even when it is built in.

<Sixth Embodiment>
FIG. 14 is another example of the information leakage prevention apparatus according to the embodiment. In FIG. 14, a serial signal distribution circuit B <b> 20 targeted for other than RGB signals is shown. The information leakage prevention apparatus shown in FIG. 14 can be applied not only to the RGB signals of the information device 2 but also to general serial signals that transmit (= include) image information. 2 video signals (component video signal, composite video signal, separate video signal, etc.) generated from the RGB signal and horizontal / vertical synchronization signal, USB signal including image information, Ethernet (registered trademark) signal including image information, etc. It can cope with even.

  Here, the serial signal distribution circuit B20 can distribute the serial signal of the information device 2 to the information leakage prevention device 1 and external peripheral devices (printer, FAX, video device, etc.). The clock signal extraction unit 11 can extract the clock signal component of the serial signal received via the distribution circuit. The clock generation unit 12 generates a signal of the extracted clock component (the highest clock signal or the like), and includes a prevention signal generation unit 13 and a prevention signal output unit 14.

  Therefore, according to the information leakage prevention apparatus 1A in the present embodiment, it is possible to obtain the same effect for any serial signal that transmits image information. can do.

  According to the embodiment described above, it is possible to prevent a third party from remotely inputting image information from unnecessary electromagnetic waves radiated from an information communication device such as a computer, a communication device, and a video display projector. Yes, image information can be prevented from being illegally used.

  In addition, it can be used in a notebook PC integrated with a display without an image information interface cable, and can be realized with a simple circuit configuration, thus preventing a significant increase in costs such as shielding. .

  In addition, since the embodiment can be applied to any serial signal format, it is highly versatile as a countermeasure against information leakage due to leaked electromagnetic waves, and can be incorporated in an information communication device such as a computer in advance, and at the same time in various directions. It has the effect that the leaked electromagnetic wave to be radiated can be effectively prevented from being received from a remote place.

  Furthermore, since the prevention signal output level for information leakage can be adjusted according to the leakage signal intensity from the information device, not only can the influence of the outputted prevention signal on the surrounding electromagnetic environment be minimized. This has the effect that the prevention signal can be output at a level corresponding to the electromagnetic wave radiation characteristics of the information equipment.

  Various modifications and changes can be made to the present embodiment without departing from the technical scope of the present embodiment. For example, except for the example of FIG. 14, the RGB and horizontal / vertical signal synchronization signals are used, but the present invention is not limited to RGB image signals, and can be applied to all serial signals for transmitting image information.

  FIG. 15 is a specific application example, (a) is used for a single information device (for example, a notebook PC, a mobile phone, a PDA terminal, etc.), and (b) is a display 21 of the information device 2 and the information device 2. Usage at the time of connection (for example, between a computer and a video monitor, between a computer and a video projector), (c) Usage at the time of connection between information devices (between information devices such as computers and printers, information devices such as computers and FAX Between the information device such as a computer and a copy agency, between the information device such as a computer and a video device, between terminals of a TV conference system, between an information device such as a computer and a communication device, etc.). According to the information leakage preventing apparatus according to the present embodiment, information transmitted during these various connection forms can be efficiently prevented from being received and decoded by a third party.

2 shows an example of an information leakage prevention apparatus and an information leakage prevention signal output method according to the first embodiment. The measurement image example of the leakage electromagnetic wave of the dot luminance signal which leaked from the information equipment based on 1st Embodiment is shown. The case where the conductor cable which can be classified into an antenna is installed in the peripheral part of the display part of information equipment concerning a 1st embodiment is shown. The example which the prevention signal production | generation part of the information leakage prevention apparatus based on 1st Embodiment uses the primary differentiation circuit is shown. An example of preventing leakage electromagnetic waves when an N- fold period circuit is used will be described. An example in which the prevention signal generation circuit according to the first embodiment prevents leakage electromagnetic waves using a duty ratio conversion circuit will be described. An example in which a luminance signal string of leaked electromagnetic waves is reproduced by a conventional reproducing apparatus by applying the first embodiment will be described. An example of electromagnetic intensity regulation will be shown. In 1st Embodiment, when a prevention signal is applied, a mode that the prevention signal electromagnetic wave is settled in regulation is shown. An example based on 2nd Embodiment is shown. An example according to the third embodiment will be described. An example according to the fourth embodiment will be described. An example based on 5th Embodiment is shown. An example according to the sixth embodiment will be described. Another modification of the embodiment will be described. An example of an analog RGB signal generation circuit used to transmit an image signal of a conventional computer is shown. An example of analog RGB signals used for transmitting image signals of a conventional computer is shown. The receiver of the conventional reproducing | regenerating apparatus is shown. 1 shows a conventional playback device. An example in which a filter circuit is inserted into an interface cable of a computer will be shown as a means for preventing information leakage due to conventional leakage electromagnetic waves. A method of reducing electromagnetic leakage by applying an electromagnetic shield to a conventional computer casing itself will be described. A conventional mask signal (a), a time waveform (b) of the leaked electromagnetic wave, and a leaked electromagnetic wave (c) in which they are synthesized are shown. Indicates a random false signal. A configuration example in which information can be reproduced by reproducing electromagnetic waves radiated from information equipment is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Information leakage prevention apparatus 2 Information apparatus 3 Serial signal interface 11 Clock signal extraction part 12 Clock signal generation part 13 Prevention signal generation part 14 Prevention signal output part 15 Leakage signal reception part 16 Leakage signal reception sensor part 17 Prevention signal adjustment part 131 Prevention signal generation circuit 132 Output amplifier

Claims (10)

In an output level variable type information leakage prevention device for preventing leakage electromagnetic waves radiated from information equipment and preventing data information contained therein from being reproduced and leaked,
A clock signal extraction unit connected to an information signal interface provided in the information device and extracting a clock component of the information signal;
A first pseudo clock signal synchronized with the clock component extracted by the clock signal extraction unit or a second pseudo clock signal having a phase difference designated in advance with respect to the first pseudo clock signal is generated. A clock signal generator to be
N-th order differential signal of the pseudo clock signal said generated by the clock signal generator (n: integer), a signal with reduced duty ratio of the pseudo clock signal, reduced de Yuti ratio of pseudo clock signal A prevention signal generation unit that generates any one or more of signals obtained by changing the offset position in the amplitude direction of the signal;
Signal application to antennas and circuit patterns installed inside or around the information device capable of emitting electromagnetic waves, various cables connected to the information device, internal circuit of the information device, metal casing of the information device A prevention signal output unit that outputs the prevention signal generated by the prevention signal generation unit as the prevention signal by any one or more means of applying a signal to one or more locations of
Radiated electromagnetic waves inside or around the information device, conductive signals observed on various cables connected to the information device, induced voltage signal on the internal circuit board of the information device, metal casing of the information device A leakage signal receiver that receives any one or more of the induced voltage signals observed at
A prevention signal adjusting unit that adjusts an output level of the prevention signal output from the prevention signal output unit based on the observation signal measured by the leakage signal receiving unit;
An output level variable type information leakage prevention apparatus comprising: The prevention signal output unit includes:
Radiated electromagnetic waves inside or around the information device, conductive signals observed on various cables connected to the information device, induced voltage signal on the internal circuit board of the information device, metal casing of the information device Measure one or more of the induced voltage signals observed in place of the leakage signal receiver,
The output level variable information according to claim 1, wherein the prevention signal adjustment unit adjusts an output level of the prevention signal output from the prevention signal output unit based on the measured observation signal. Leakage prevention device. The prevention signal adjustment unit includes:
Determining means for determining an output level of the prevention signal from the prevention signal generation to the prevention signal output unit before outputting the prevention signal, based on a result of the leakage signal reception unit measuring the observation signal;
Alternatively, any one of determination means for adaptively determining an output level of the prevention signal from the prevention signal generation unit to the prevention signal output unit while the leakage signal reception unit measures the observation signal The output level variable type information leakage prevention apparatus according to claim 1, wherein: The information signal is an RGB signal and horizontal / vertical synchronization signal of the information device, or a video image signal generated from the RGB signal and horizontal / vertical synchronization signal of the information device, and the clock component is a dot of the information device. 2. The output level variable type information leakage prevention apparatus according to claim 1, wherein the output level variable information leakage prevention apparatus is a clock signal. When the information signal is the RGB and horizontal / vertical synchronization signal of the information device, the clock signal extraction unit and the clock signal generation unit generate the pseudo clock signal from the dot clock signal of the information device, instead of generating the pseudo clock signal. A pseudo clock signal is generated from any one or more of the R signal, G signal, and B signal of
5. The output level variable type information leakage prevention apparatus according to claim 1, wherein the output level is variable. In an output level variable information leakage prevention method for preventing leakage of electromagnetic waves radiated from information equipment and preventing data information contained therein from being reproduced and leaked,
Extracting a clock component of the information signal in a clock signal extraction unit connected to an information signal interface provided in the information device;
In the clock signal generation unit, the first pseudo clock signal synchronized with the clock component extracted by the clock signal extraction unit or a second phase difference designated in advance with respect to the first pseudo clock signal Generating a pseudo clock signal of:
In the prevention signal generation unit, n order differential signal of the clock signal generating pseudo clock signal generated by the unit (n: integer), a signal with reduced duty ratio of the pseudo clock signal, the pseudo clock signal de Generating any one or more of signals having a changed offset position in the amplitude direction of the signal having a reduced duty ratio;
In the prevention signal output unit, signal application to the antenna or circuit pattern capable of emitting electromagnetic waves installed in or around the information device, various cables connected to the information device, the internal circuit of the information device, Outputting the prevention signal generated by the prevention signal generation unit as the prevention signal by any one or more means of applying a signal to one or more locations of the metal casing of the information device;
In the leakage signal receiving unit, radiated electromagnetic waves inside or around the information device, conductive signals observed on various cables connected to the information device, induced voltage signal on the internal circuit board of the information device, the information Receiving any one or more of the induced voltage signals observed at the metal housing of the device;
In the prevention signal adjusting unit, adjusting the output level of the prevention signal output from the prevention signal output unit based on the observation signal measured by the leakage signal receiving unit;
An output level variable type information leakage prevention method characterized by comprising: In the prevention signal output unit,
Radiated electromagnetic waves inside or around the information device, conductive signals observed on various cables connected to the information device, induced voltage signal on the internal circuit board of the information device, metal casing of the information device Measuring any one or more of the induced voltage signals observed in place of the leakage signal receiver,
Based on the measured observation signal, the prevention signal adjustment unit adjusts the output level of the prevention signal output from the prevention signal output unit;
The output level variable information leakage prevention method according to claim 6, further comprising: In the prevention signal adjustment unit,
Determining an output level of the prevention signal from the prevention signal generation to the prevention signal output unit before outputting the prevention signal based on a result of the leakage signal reception unit measuring the observation signal;
Alternatively, the leakage signal receiving unit adaptively determines the output level of the prevention signal from the prevention signal generation unit to the prevention signal output unit while measuring the observation signal. 7. The output level variable type information leakage prevention method according to claim 6, further comprising a step of selecting. The information signal is an RGB signal and horizontal / vertical synchronization signal of the information device, or a video image signal generated from the RGB signal and horizontal / vertical synchronization signal of the information device, and the clock component is a dot of the information device. 7. The output level variable type information leakage prevention method according to claim 6, wherein the information level is a clock signal.   When the information signal is the RGB and horizontal / vertical synchronization signal of the information device, the clock signal extraction unit and the clock signal generation unit generate the pseudo clock signal from the dot clock signal of the information device, instead of generating the pseudo clock signal. 10. The output level variable information leakage prevention method according to claim 6, wherein a step of generating a pseudo clock signal from any one or more of the R signal, the G signal, and the B signal is executed.

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