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Abstract

Content

Introduction

The concept of industrial espionage arose with the advent of industry and is an integral part of relations in countries where along with the state there are other forms of ownership. The essence of industrial espionage is the desire to master the secrets of competitors in order to obtain maximum commercial benefits. It consists in obtaining any information on the latest scientific and technical developments (know-how), commercial plans, the state of affairs, etc. It is being conducted by all available means, including the use of special technical means and the bribing of officials. However, in spite of the fact that industrial espionage in direct formulation does not affect the interests of the state, it is an illegal activity, as it encroaches on the constitutional rights of citizens. The state stands on the protection of these rights, which means that their violation leads to criminal liability. Speech information is one of the main sources of information, data on the person's personal life or financial, research and production activities of the organization, that is, information that is not widely publicized (sometimes completely secret). Despite the significantly increased role of automated information systems (AIS), voice information in message flows is still prevalent. The speaking person, the environment of the propagation of acoustic, vibro-acoustic and electromagnetic oscillations, the propagation lines of electrical oscillations, the technical means of detecting and processing these oscillations form a channel of unauthorized access to information subject to protection. As a result, the protection of voice information is one of the most important tasks in the overall complex of measures to ensure the information security of the facility. To intercept it, a person interested in obtaining information can use a wide arsenal of portable means of acoustic speech intelligence, which allows to intercept speech information via direct acoustic, vibro-acoustic, electro-acoustic and opto-electronic (acousto-optical) channels. The main of these funds include:

  • portable radio sound recording equipment (dictophones, tape recorders);
  • directional microphones;
  • electronic stethoscopes;
  • electronic devices for interception of voice information (embedded devices) with sensors of microphone and contact types with the transmission of information by radio-optical (in the infrared wavelength range) and ultrasonic channels, electric power networks, telephone lines, connecting lines of auxiliary technical means or specially paved channels ;
  • optoelectronic (laser).

    In this paper, the issue of protecting voice information from hidden sound recording by means of the first type of the above-mentioned means — dictaphones — is considered. In particular, the protection of voice information from a hidden record.

    1. Theme urgency

    The urgency of this issue is that at present the urgent task is to ensure the protection of negotiations from the latent recording by electronic means of registration. Today, the acquisition and use of hidden means of transmitting information through the radio channel is sharply limited by legislation. In this situation, the use of dictaphones is the cheapest, easy-to-use and legal way of registering voice information. This class of equipment (in connection with the rapid development of electronics) has become superminiature in size and allows the recording of large amounts of information.

    Currently, a large number of models for suppressing electronic devices for recording voice information are offered to protect the object from information leakage, which differ in their different characteristics. This leads to the complexity of choosing the optimal suppression method. Therefore, in order to solve this problem, it is necessary to propose an optimal method that will allow to comprehensively take into account the determining characteristics of the suppressors of electronic devices for interception of speech information.

    2. Goal and tasks of the research

    Research and selection of the most effective technical solutions for suppression of electronic devices for interception and recording of speech information.

    The main objectives of the study:

    1. Research of mechanisms of interception of speech information;
    2. Analysis of methods and investigation of suppression mechanisms;
    3. Highlighting the most effective method of suppressing recording devices;
    4. Based on the chosen method, we propose a model of the future device.

    Object of the research: electronic devices for interception of speech information.

    The subject of the research: methods of suppression of electronic devices for interception and recording of speech information.

    3. Review of research and development

    In work [1], an effective method of protecting voice information from its interception by technical means is proposed — suppression of the receiving devices of these means by active electromagnetic interference. The principle of operation of these devices is based on the generation of high-power pulsed high-frequency noise signals. The interference signals radiated by directional antennas, acting on the elements of the electronic circuitry of the recorder (in particular, the low-frequency amplifier), induce noise signals in them. Consequently, simultaneously with the information signal (speech), a recorded and detected noise signal is recorded, which leads to a significant distortion of the first.

    In work [2] the acoustic system of adaptive suppression of an information signal is offered. The principle of operation of the system is to create within the limits of the guard zone with the help of compensating acoustic systems an area within which the sound level is either absent or significantly weakened or distorted to an illegible state.

    In work [3], a highly effective ultrasonic radiator was considered for use in a room protection system against leakage of voice information through an acoustic channel. Such directional radiators can be used to create limited zones with difference frequencies at a given point in the room, in which it is necessary to ensure write suppression.

    4. Devices for suppressing operating sound recording devices

    The recorder can be suppressed, that is, create conditions under which recording is impossible. In recent years, various depressors of dictophones have been used more often, in which both acoustic and electromagnetic interference can be used. There are the following types of impact on voice recorders:

    • on microphones in the acoustic range;
    • on electronic circuits of the sound recording device.

    4.1. Countermeasures using the principle of directly affecting the microphone

    These systems can be divided into two groups:

    • exposure to a microphone in the ultrasonic range to overload the microphone amplifier;
    • the use of the generator of active acoustic noise in the speech range.

    The means of ultrasonic suppression emit powerful ultrasonic oscillations (ultrasonic vibrations) that are inaudible to the human ear. Modern dictaphones are usually equipped with either an electret microphone or a capacitor, the upper limit of the bandwidth of which is 25-27 kHz and falls into the ultrasonic frequency range. That is, these recorders perceive ultrasonic ultrasonics, as a result of which single-frequency and two-frequency ultrasonic suppressors are used [4].

    The advantage of ultrasonic suppression systems — single-frequency and two-frequency — is the concealment of counteraction. However, their effectiveness is sharply reduced if measures are taken to counteract suppression in advance, as is done in special means, namely:

    • the microphone of the voice recorder can be covered with a filter of a special material that limits the bandwidth of the audio range;
    • in the path of the microphone amplifier, establish a low-pass filter with a cut-off frequency below 0.3-4 kHz;
    • microphones with a bandwidth of up to 4 — 5 kHz are used in dictophones.

    The second group of suppression means, using generators of active acoustic noise in the speech range, is used in limited cases. However, to date, a large number of active vibro-acoustic camouflage has been created, successfully used to suppress voice interception facilities.

    Along with noise interference, for the purpose of active acoustic masking, "speech-like" noise, chaotic pulse sequences, etc. are used.

    Improving the comfort of conducting conversations is to optimize the interference spectrum, ensuring compliance with the required standards for the protection of information with a minimum integrated level of interference [5].

    In systems of acoustic masking, as a rule, noise of the type "white" and "pink" noise is used. "Speech-like" noise is formed (synthesized) from speech signals. In this case, the formation of interference from both the concealed signal and from uncorrelated speech fragments (segments) uncorrelated is possible. It is known that for one and the same radiated power, speech-like noises (interference) have a somewhat greater masking effect. The additional masking capabilities of such interference, in comparison with the rest of the above, are explained by their structural similarity to the masked speech signals. As a result, the human auditory mechanism is unable to isolate a useful speech signal against speech-like interference even with speech / noise ratios higher than when masked by dispersive noise [6].

    4.2. Dictaphone suppression systems by affecting electronic circuits of a sound recorder

    The principle of the electromagnetic suppressors of dictophones is the same, they are a generator of electromagnetic radiation of sufficiently high power operating in the microwave range (as a rule, these radio interference generators have a relatively narrow band of radiation, so as to minimize interference to radio receivers of various purposes and maximize the spectral density of the signal) . The frequencies at which these devices operate are more often around 1 GHz, although there are exceptions. Power — units of watts, for example, 5-6 W [7].

    Structurally, the dictaphone suppressors consist of a generator, power supply and antenna. Electromagnetic interference they radiate in a directional way: usually a cone of 60-70 degrees, directed in one direction (the back lobe of radiation is practically absent). It is in this zone that dictaphone suppression occurs. A directional signal makes it possible to substantially increase the intensity of the electromagnetic field in the suppression zone and to reduce the interference induced on the electronic equipment located outside the suppression zone (office equipment, computers, television sets, etc.). Since the noise signal is induced directly in the input circuits, another listening device with microphones is equally well suppressed.

    The EM suppressors of dictaphones have disadvantages

    1. Adverse effects on the human body. Many devices of this class have medical certificates. As a rule, they indicate at what distance and how much time a person can safely be in the zone of the main lobe. For example, for one of the products at distances of 1.5 m, this time is up to 40 minutes per day, at a distance of 2.0 m to 1 hour, and in the zone of the rear and side lobes, the time is not limited. Here it is possible to give such a comparison: cell phones for all its prevalence have a greater impact (harmful) on the human body than the suppressors [9].
    2. The source of noise electromagnetic radiation interferes with conventional radio electronic equipment. Radio receivers, active acoustic speakers, conventional telephones, office radiotelephones with analog radio channels, audio and video intercoms, household televisions, computer monitors are most affected. If the position of the suppressors is unsuccessful, there may be false alarms of the security and fire alarms. In fact, almost all of these problems can be solved by a competent installation, location relative to other radioelectronic devices and, as already mentioned above, a proper location relative to the owner.

    References

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