RU11430U1 - DEVICE FOR PROTECTING CONFIDENTIAL NEGOTIATIONS - Google Patents

Abstract

A device for protecting confidential negotiations, containing a series-connected generator of electric noise in the frequency range of masked acoustic information and an electro-acoustic emitter, characterized in that it includes a device for processing masked acoustic information that contains a microphone, headphones for the number of participants in confidential negotiations and a two-channel digital adaptive filter, to the first input of which the microphone output is connected, to the second input connected to the second output of the generator of electrical noise signal in the range masked frequency acoustic information, and to output - headphones.

Description

DEVICE FOR PROTECTING CONFIDENTIAL NEGOTIATIONS

The utility model relates to the field of secret communications and can be used as a means of protection against listening to confidential conversations conducted indoors or outdoors.

A confidential communication device 1 is known, comprising a telephone installation, a speech converter unit connected to an input of a communication channel through a first cryptographic unit, a second cryptographic unit and a second speech converter installed at the output of the communication channel, as well as switching means and a controlled power supply.

A number of devices are also known that provide encoding and decoding of a speech signal when using radiotelephone communication channels.

So, in the device for conducting secret negotiations 2 on the transmitting side, the speech spectrum signals are modulated and emitted in the form of a sequence of eight types of signals combined in a certain way relative to the upper and lower frequencies of the selected band, and on the receiving side, the sequence is demodulated and synchronized by means of a signal input into every parcel combination.

MPK N04K 1/00

In secret communication devices 3, 4, in addition to manipulating an analog speech signal, a digital control signal is used, transmitted in pauses of speech to change the code and the type of modulation of secret information.

A common drawback inherent in these devices is that they are designed only for two participants in the exchange of confidential information and cannot provide simultaneous notification and interaction of a wider circle of persons participating in negotiations. In addition, these devices do not provide protection against eavesdropping devices that can be installed in the locations of participants in the exchange of information, which is especially important when conducting meetings in closed rooms.

A known method of protection against eavesdropping 5, which consists in the fact that a masking signal is applied to the information signal in the form of alternately supplied tonal signals of different frequencies. At the receiving end of the communication line, a masking signal is suppressed, and its amplitude is adjusted so that it turns out to be large enough to block the normal operation of the listening device, but small enough for the receiver used in this communication system.

The disadvantage of this method when used to protect against eavesdropping devices installed indoors, is the ability to quite easily identify the frequency spectrum of the masking signal, which, when retrofitting the eavesdropping device with an appropriate filtering system, reduces the efficiency of the method.

A more effective way of actively counteracting the technical means of listening to the room is to create an acoustic noise signal in the room in a band that covers the sound area of the frequency range and exceeds the useful acoustic signal in intensity.

Numerous devices are known for generating random signals in the field of audio frequencies, equipped with means for adjusting the band, power and other characteristics of noise 6, 7. The use of intense noise interference in a room neutralizes listening devices.

The disadvantage of these devices is the uncomfortable environment for people in the room, which impedes the information exchange between negotiators, and at high noise levels makes it almost impossible.

There is also known a device for generating camouflage acoustic noise on a window pane 8, by the totality of features and the problem to be solved, which is closest to the proposed device and adopted as a prototype. The prototype device contains an uncorrelated electrical noise signal generator, a bandpass filter, a power amplifier and an electrodynamic converter mounted directly on the glass surface and exciting it in a wide frequency band of the sound range. Intense vibrations of the protected surface under the influence of a noise signal mask a useful acoustic signal, and thereby block the operation of external listening devices: laser and directional microphones of stethoscopes, etc. The advantage of the device is the high comfort of conducting confidential negotiations in a protected room.

The disadvantage of the prototype device is that it does not provide protection for participants in confidential negotiations from eavesdropping equipment installed in the immediate vicinity of the participants in the negotiations.

The task at hand is to provide effective protection against listening to confidential negotiations conducted both indoors and outdoors, while creating comfortable conditions for negotiators.

The essence of the proposed solution lies in the fact that in the device for protecting confidential negotiations, containing a series-connected generator of electric noise signal in the frequency range of masked acoustic information and an electro-acoustic emitter, a device for processing masked acoustic information is introduced, which contains a microphone, head phones according to the number of participants in confidential negotiations and a two-channel digital adaptive filter, to the first input of which an output is connected microphone connected to a second input of the second output of the electric generator of the noise signal in the range masked frequency acoustic information, and to output - headphones.

The essence of the proposed solution is illustrated by a further description and drawing, which presents a structural diagram of the device.

The proposed device contains installed in the premises for confidential negotiations, the generator 1 of the electric noise signal in the frequency range of masked acoustic information, the output of which is connected to an electro-acoustic emitter 2, made, for example, in the form of an electrodynamic transducer with a horn that emits sound waves in all directions in which it is possible to place eavesdropping devices, and a device 3 for processing masked acoustic information. The device 3 contains a microphone 4 connected to the first input of the two-channel digital adaptive filter 5, and head phones (headphones) b, according to the number of participants in confidential negotiations, connected to the output of the digital adaptive filter 5. The second input (reference signal input) of the digital adaptive filter 5 is connected to the second output of the generator 1 of the electric noise signal.

electric noise signal can be performed similarly to pseudorandom signal generators, considered, for example, in work 9. A two-channel digital adaptive filter 5 can be similar to the known ones described, for example, in work 10.

The proposed device operates as follows.

In the room where negotiations are conducted, under the influence of an electric noise signal generated by the generator lj emitter 2, acoustic noise is created that masks the speech signal (masked acoustic information) of the sources of 7 acoustic information (negotiators). Thus, an acoustic signal is present in the room, which is a mixture of masking noise and speech of negotiators (masked acoustic information). This mixture as the main signal through the microphone 4 is fed to the first input of a two-channel digital adaptive filter 5. At the second input of the filter 5 receives "pure noise (reference signal) directly from the generator 1 of the electric noise signal. The two-channel digital adaptive filter 5 processes both signals and, through the headphones 6, gives the negotiators a speech signal cleared of masking noise.

Compensation of the noise component in the mixture of masking noise and speech is provided when implementing a two-channel digital adaptive filter 5 with a finite impulse response of the filter error minimization algorithm, which is defined as the difference between the main signal and the noise estimate. The noise estimate is calculated from P of the last samples of the reference signal, taking into account the delay p that occurs when the noise signal passes from the electro-acoustic emitter 2 to the microphone 4, by P linear prediction coefficients. At each iteration of the calculations, which coincides with the sampling period of the input and output signals of the two-channel digital adaptive filter 5, new linear prediction coefficients are calculated depending on the values of the filter error signal and the reference signal. As a result, the two-channel digital adaptive filter 5 suppresses the correlated components of the main and reference signals, and a “speech-free speech signal” remains at its output.

The mathematical description of the operation of the two-channel digital adaptive filter 5 can be represented by the following expressions:

p y (n) S w (n, i) x (n-p-i)

e (n) z (n) - y (n)

w (n + l, i) w (n, i) + m (n) x (n-p-i),

z (n) is the next count of the main signal,

x (n) is the next reference signal count,

y (p) - the next countdown of the noise estimate,

e (p) - the next countdown of the error signal,

w (n, i) is the next value of the linear prediction coefficient,

m is a coefficient that determines the rate of adaptation,

P is the number of linear prediction coefficients,

p is the delay of the acoustic signal,

n is the value of the discrete time, (, 2, 3, ...)

i is the number of the linear prediction coefficient (, 2, ..., P).

sign is the symbol sign of the function e (n).

Thus, as a result of using the proposed solution, a technical effect is achieved consisting in blocking by an intense noise signal the operation of listening devices installed both inside and outside the room. At the same time, participants in confidential negotiations do not experience inconvenience associated with being in a noisy space,

because are in the headset b and hear speech cleared of masking noise.

The presented description, drawings and the existing elemental base allow us to easily manufacture the proposed device in production and use it to create technical means of protecting confidential negotiations.

LIST OF REFERENCES

1.RF, certificate No. 8194 for a utility model, IPC НО4К 1/00, publication October 16, 1998.

2. Japan, accepted application No. 3-4144, IPC Н04К 1/04, publication 1/22/91.

3. Japan, accepted application No. 1-58701, IPC Н04К 1/00, publication 13.12.89.

4. France, application No. 2625391, IPC Н04К 3/00, publication 06/30/89.

5. PCT, application No. 90/14722, IPC Н04К 1/02, publication November 29, 1990

6. RF patent for invention, IPC G10K 3/00, publication 16.10.98g.

7. Catalog of the exhibition “Security Systems - 94, St. Petersburg, 1994, p. 47.

8.RF, certificate No. 3068 for a utility model, IPC NOZV 29/00, publication October 16, 1996, prototype.

9.L. J. Hoffman Modern methods of information security. M.: Sov. Radio, - 1980, - S. 89-91.

10.A. Weiss and D. Mitra. Digital Adaptivs: Conditions for Convergence, Rats of Convergence, Effect of Noise and Errors Arising from the Implementation, IEEE Trans. On Information Theory, vol. IT-25 (Nov. 1979), pp. 637-652.

Claims (1)

A device for protecting confidential negotiations, containing a series-connected generator of electric noise in the frequency range of masked acoustic information and an electro-acoustic emitter, characterized in that it includes a device for processing masked acoustic information that contains a microphone, headphones for the number of participants in confidential negotiations and a two-channel digital adaptive filter, to the first input of which the microphone output is connected, to the second input connected to the second output of the generator of electrical noise signal in the range masked frequency acoustic information, and to output - headphones.