RU2503132C2 - Method of protecting distributed random antenna - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method of protecting a distributed random antenna involves connecting to a distributed random antenna through N interfacing devices N interference generators which protect the distributed random antenna, wherein M+K of the N interfacing devices include M amplitude modulators which, under the action of M of the N interference generators, perform stochastic amplitude modulation, as well as K angle modulators which, under the action of K of the N interference generators, perform stochastic angle modulation of information signals and interference generated by the distributed random antenna.

EFFECT: high efficiency of protecting distributed random antennae.

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Description

The invention relates to the field of protection of confidential information (CI) and can be used to protect radio systems, combined by the term "distributed random antennas" (SAR).

To ensure KI protection, it is important to identify and sequentially shut off all technical leakage channels, including along connecting lines (SL), leaving the premises to be protected (PZP) in the external environment. Examples of PPPs are premises (office rooms, meeting rooms and booths, conference rooms) designed to work with KI during meetings, negotiations, conferences, etc. Examples of SLs acting as PCA are power supply, grounding, warning, security and fire alarm systems; cable lines of external, internal office and computer communications; pipes of ventilation systems and central heating; metal parts of load-bearing structures in buildings, etc.

The negative features of the leakage channels of CI through SAR are:

- the complex and often ambiguous (previously unpredictable) nature of the excitation associated with the conversion of the original signal generated by the source of the KI (hereinafter KI signal) into KI signals diverging along the SL. The sources of KI can be both the main (directly involved in the processing, transmission and reception of KI signals) technical means (TS), that is, working equipment, and auxiliary (not participating in these processes, but located in the PZP-system and power supply, grounding, security and fire alarms, alerts, communications, computers, office equipment, etc.);

- usually a fundamentally different nature of the propagation of the KI signal inside the PZP and the KI signals in the trunk, with which TS located in the PZP are connected to external public equipment. As a result of this, CI signals can, with low attenuation, go far beyond the PPZ through the SAR and become accessible to the attacker;

- difficulties in modeling (mathematical, physical, computer) sources of CI and SL, acting as SAR;

- the negative dynamics of the ecological and ergonomic characteristics of the PZP when using most known methods and means of eliminating the leakage channels of CI - leading to thermal, noise and electromagnetic pollution of the PZP, deterioration of the microclimate (increased humidity and a change in the composition of the air without ventilation), a decrease in the level of natural geomagnetic background, etc. .P. In some cases, the undesirable factors are also the high cost, weight and dimensions of the equipment for protecting the PPP.

As a variety of random antennas (see classification in [1-2]), SARs have not been sufficiently studied at present. Methods of information protection PCA also have a number of unexplored features. This is due, firstly, to the fact that, unlike SLs, which form the main communication channels (through which KI signals go to “legitimate” - authorized consumers of KI), due to SAR, side channels (leakage channels of KI) arise through which KI signals are sent to unauthorized KI consumers - attackers. When organizing information protection of the trunk of main channels, the limitation is the absence of unacceptable interference for legitimate consumers of CI. When protecting PCA, this restriction does not exist, since only attackers connect to them.

Secondly, reliable and universal methods of passive protection of SLs ("tight" electromagnetic shielding, grounding, filtering of KI signals [3-8]) for PCA protection are often not applicable. The main and most promising means in this case is the active protection of KI - using various kinds of intentional interference (protective noise, imitating, sighting). Thirdly, since KI signals through SAR can go far beyond the PPP with low attenuation, an attacker can use highly efficient stationary equipment for his own purposes. Therefore, when organizing the protection of CI, it is necessary by all available means - including new scientific and technical ideas - to increase its universality and effectiveness.

The following methods are known for active protection of KI, based on the use of signals of a special kind (deliberate interference), called up by the energy method (for masking noise interference) or by causing maximum information damage (for imitation interference) to "suppress" KI signals in all available and potential leak channels, in order to make it difficult for an attacker to intercept and process CI with the help of the available vehicles [3-8]:

- linear noise, which is implemented using a noise generator that delivers a signal with a level of Um (t) to all trunk lines subject to protection;

- spatial noise, which refers to the creation of an electromagnetic field (EMF) within the PZP with a structure and characteristics that protect the KI from interception through electromagnetic leakage channels;

- code noise - used when it is impossible to use other types of active protection associated with EMF;

- self-noise, which is a specific type of computer noise, when either the computers standing next to them work in such a way that the EMFs of their KI signals distort each other, or one computer operates in multiprogram mode when it is difficult for an intruder to extract the KI signal to extract the KI.

A well-known direction in the development of active protection methods is the use of simulated interference generators capable of causing maximum information damage to a potential attacker at low EMF levels in the environment (which is necessary to improve the electromagnetic compatibility of the vehicle and ensure the safety of working conditions of KI personnel and consumers) [9]. Methods of amplitude and angular (frequency, phase) modulation of signals are known from the level of technological development [10].

The closest in technical essence is the method of linear noise [8, p.188, Fig.8.9] (prototype of the invention), which, in relation to the conditions of the problem being solved, provides for connecting intentional noise interference generators to the PCA through N devices that provide information protection PCA. The considered KI signal in a given time-frequency domain is U _c (t) = U ₀ (t) cos Ф (t), where the signal amplitude is U ₀ (t) = U _A + U ₁ (t); U _A is the amplitude of the carrier signal, U ₁ {t) is the KI signal modulating the amplitude; phase angle of the signal Φ (t) = ω _c t + φ _c t + Ω (t), where ω _c and φ _c are, respectively, the carrier frequency and phase of the carrier signal, Ω ₁ (t) is the KI signal modulating the phase angle, t is the current time. The idea of linear noise is to add noise interference U _w (t) to U _c (t), that is, the formation of an additive signal mixture and interference of the form U _c (t) + U _w (t) = U ₀ ( t) cos Φ (t) + U _w (t). In the accepted designations of amplitude modulation (AM) corresponds to the addition of the modulating KI signal U ₁ (t) to U _A as part of the factor U ₀ (t); angular modulation (AM) - the effect of Ω ₁ (t) on the terms in the composition of the angular factor Ф (t): for frequency modulation (FM) - on ω _с (t); during phase modulation (FM), by φ _c (t).

Intentional interference on the basis of the effect on the KI signal can be divided into two categories: additive interference (AP) U _AP (t), which meets the condition U (t) = U _c (t) + U _AP (t), where U (t ) is the signal received by the attacker's vehicle; and the multiplicative interference (MP) U _MP (t) corresponding to the condition U (t) = k _MP U _c (t) · U _MP (t), where k _MP is a dimension coefficient depending on the implementation of the MP. A generalization of the prototype method is to use as U _AP (t) instead of U _W (t) a simulation interference U _u (t) - similar in properties to U _c (t), but not related to modulating KI signals U ₁ (t) and Ω ₁ (t).

The main disadvantage of the prototype method is the ability to significantly reduce the effectiveness of PCA protection by using an attacker using known methods to increase the noise immunity of receiving signals of any particular type (analog, digital) when processing an additive signal mixture and intentional noise interference U (t) = U _c (t) + U _AP (t) = U _c (t) + U _w (t) [11]. In addition, practice shows that in order to ensure the required effectiveness of PCA protection, the levels of U _w (t) should be sufficiently large, which is associated with an increase in the environmental hazard of the PCA protection system for the environment by the electromagnetic factor.

When using simulated interference similar in parameters to the KI signal, the information damage caused to the attacker depends on the accuracy of the interference reproducing the parameters of the KI signals - which, at the same time, must be devoid of a specific KI content [9; 12-13]. These requirements contradict each other, which significantly complicates the possibility of implementing this method of PCA information protection. The use of simulation interference also complicates the need for constant synchronization of interference with the KI signal.

When protecting SARs, in which KI signals circulating accompanying computer operation circulate, the main interest is represented by the digital modulation types FM-2 and AM-2 [14-15]. However, if external radiating radio devices (such as Bluetooth, etc.) are used in computer networks, signals with other types of PA can also act as KI signals.

When analyzing possible options for intercepting CI with the help of analytical calculation or by the method of computer simulation [2; 12-13] determine how AP and MP of various types affect the noise immunity of receiving KI signals with the specified modulation. It is taken into account that real interference and KI signals usually have mutually overlapping frequency energy spectra and intensities corresponding to the condition P _p ≥P _c , where P _p and P _C are the average power of the interference and KI signal at the input of the attacker's TS [12- 13].

It is known from the prior art that APs significantly affect the noise immunity of receiving KI signals from AM [11], therefore they are capable of providing sufficiently effective protection for SAR. In turn, MPs with AM with a passive pause are ineffective, however, with CMs they are also able to significantly reduce the noise immunity of receiving KI signals. Since KI signals with AM and AM can simultaneously circulate in SAR that are subject to information protection, it is advisable to use AP and MP together to eliminate the disadvantages of the prototype method.

The proposed solution to the problem is to subject the mixture of the KI signal and noise to additional stochastic modulation: AM using intentional interference U ₂ (t) and AM using intentional interference Ω ₂ (t). In this case, a total KI signal of the form U _Ω (t) cos _{Ω Ω} U _P (t) will be generated in the SAR, where the amplitude of the total signal is U _Ω (t) = k _MP U ₀ (t) U _MP (t) = k _MP [U _A U _MP (t) + U ₁ (t) U _MP (t)], and its phase angle is Ф _Ω (t) = Ф (t) + Ω ₂ (t) = ω _c t + φ _с + Ω ₁ (t) + Ω ₂ (t). The intentional additive interference in this case is the noise converted in the process of stochastic AM and AM using the functions U ₂ (t) and Ω ₂ (t), which in general can be written as U _П (t) = U _ш [t; U ₂ (t); Ω ₂ (t)].

Thus, instead of modulating the amplitude of the KI signal U ₁ (t) in the prototype, when implementing the proposed method for protecting the SAR in the total KI signal, the product U ₁ (t) · U ₂ (t) will appear, and instead of the phase angle Ф (t) = ω _c t + φ _c + Ω ₁ (t) is the phase angle Ф _Ω (t) = ω _c t + φ _c + Ω ₁ (t) + Ω ₂ (t), as a result of which the noise immunity of reception in the side channel is reduced for KI signals with AM and AM. The use of low-power MF also reduces the power level of the AP, which leads to an increase in the ecological purity of the SAR protection system by the electromagnetic factor without compromising its effectiveness.

The technical result of the invention is to increase the protection efficiency of SAR by additional stochastic modulation of the mixture of the KI signal and the AP U _c (t) + U _AP (t) circulating in the SAR: AM using intentional interference U ₂ (t) and PA using intentional interference Ω ₂ (t). An additional result is an increase in the ecological purity of the SAR protection system by the electromagnetic factor by reducing the noise interference field strength U _AP (t) necessary to ensure the specified SAR information security.

The essence of the proposed method for protecting a distributed random antenna, including connecting to a distributed random antenna through N interfacing devices for interference generators, which provide information protection for a distributed random antenna, consists in the fact that M amplitude modulators are introduced into M + K from among N interfacing devices, which under the influence of M from among N interference generators, stochastic amplitude modulation is performed, as well as K of angular modulators, which under the influence of K from among N generators interference moat carried stohaoticheskuyu angle-modulated information signals and noise radiated random distributed antenna.

Figure 1 shows a prototype linear noise method of PCA with a complex multi-story structure, where 1 - PCA in the form of a branched heterogeneous SL; 2 - interface device (total number N, highlighted by dashed contour lines); 3 - interference generator (total number N).

Figure 2 illustrates the proposed method of information protection PCA, where 1 - PCA in the form of a branched heterogeneous SL; 2 - interface device (total number N, highlighted by dashed contour lines); 3 - interference generator (total number N); 4 - amplitude modulator (total number M, are part of M interface devices); 5 - angular modulator (total number K, are a part of K interface devices); M + K N N.

Figure 3 represents an embodiment of a joint implementation of a device for coupling an nth interference generator U _2n (t) and a device having a resistance Z _2m (t) - highlighted by a dashed contour line modulated by an mth interference generator U _2m (t).

Figure 4 shows an equivalent circuit for connecting the interface device shown in Figure 3 to points AA in the PCA.

Figure 5 shows graphs of the dependence of the probability p _{n of the} erroneous reception of KI signals on the signal-to-noise ratio during the combined and single exposure of an attacker TS of various types of imitation interference.

The known prototype method is as follows.

Into the lines forming the SAR 1 (see Figure 1) through N interface devices 2 are connected the intentional noise jammers 3, which protect the SAR by forming instead of the circulating KI signal U _c (t) = U ₀ (t) cos Φ (t) a mixture of signal and noise AP of the form U _C (t) + U _ш (t) = U ₀ (t) cosФ (t) + U _ш (t). If necessary, reduce the AP levels necessary for effective protection of the SAR, instead of the noise AP, a simulated interference U _u (t) is used - similar in properties to U _c (t), but not associated with modulating KI signals.

The connection diagram of the intentional noise jamming generators 3 to points AA in the SAR corresponds to Figure 3 in the absence of stochastic modulation: when U _2m (t) = 0 and Z _2m (t) = const; equivalent circuit Figure 4 - a special case of r _2m (t) + jx _2m (t) = const.

The main disadvantage of the prototype method is the ability to significantly reduce the effectiveness of SAR information protection by using an attacker using known methods to increase the noise immunity of receiving signals of any kind when processing a mixture of a KI signal and a noise AP of the form U (t) = U _c (t) + U _AP (t) = U _c (t) + U _w (t) [11-13]. To ensure the required effectiveness of the SAR protection, the levels of U _w (t) should be sufficiently large, which is associated with the environmental hazard of the SAR protection system for the environment (personnel, KI consumers) by the electromagnetic factor.

When using simulation APs similar in parameters to the KI signal, the information damage caused to the attacker depends on the accuracy of the reproduction of the AP parameters of KI signals - which, at the same time, should be devoid of KI content [9; 12-13]. These requirements contradict each other and significantly complicate the implementation of this PCA protection method. The use of imitation APs also complicates the need for constant synchronization of interference with the KI signal.

In order to eliminate these drawbacks, the proposed invention proposes to subject the mixture of the KI signal and noise AP to additional stochastic modulation: AM using U ₂ (t) and AM using Ω ₂ (t), that is, to use the maximum capabilities of these APs and MP at the same time.

The proposed method is as follows.

To the SLs forming PCA 1 through N interface devices 2, which include M≤N amplitude modulators 4 (see Figure 2), interference generators 3 are connected, which protect the PCA by means of a stochastic AM mixture of the KI signal and noise AP using U ₂ (t) and a stochastic CM using Ω ₂ (t). The result of this is the formation in the SAR of a KI signal of the form U _Ω (t) cos Φ _Ω (t) + U _П (t), the amplitude of the total signal is U _Ω (t) = k _MP U ₀ (t) U _MP (t) = k _MP [U _A U _MP (t) + U ₁ (t) U _MP (t)], and the phase angle Ф _Ω (t) = Ф (t) + Ω ₂ (t) = ω _c t + φ _c + Ω ₁ (t) + Ω ₂ (t). Thus, instead of modulating the amplitude of the KI signal U ₁ (t) in the prototype, when implementing the proposed method for protecting the SAR in the total KI signal, the product U ₁ (t} · U ₂ (t) appears, and instead of the phase angle Ф (t) = ω _c t + φ _c + Ω ₁ (t) is the phase angle Φ _Ω (t) = ω _c t + φ _c + Ω ₁ (t) + Ω ₂ (t). The result is a decrease in noise immunity of reception in the side channel for KI signals with AM and AM (FM and FM): although MP with AM (for KI signals with a passive pause) are ineffective, with AM (FM and FM) they can significantly reduce the noise immunity of receiving KI signals with an active pause [11- 13 ] Since KI signals with AM and AM can be circulated simultaneously in PCA to be protected, it is advisable to use AP and MP together (see the graphs of Figure 5 below) - especially since the use of MP allows a decrease in the level of field strength of the AP, which leads to to improve the environmental friendliness of the PCA protection system without compromising its effectiveness.

An example implementation of a pairing device 2 based on a transformer connected to the PCA 1 at points AA is illustrated in FIG. 3. The electric circuit of the primary winding of the transformer here includes the generator of the nth interference U _2n (t), which determines the AP level at points AA taking into account the transformation coefficient W ₂ / W ₁ , and modulator 4 is a device capable of changing its complex internal resistance Z _2m (t) = R _2m (t) + jX _2m (t) under the influence of the mth interference generator U _2m (t) /

The equivalent circuit of this interface device 2 is shown in FIG. 4: its parameters u _2n (t) ≈U _2n (t) · W ₂ / W ₁ and z _2m (t) ≈ (W ₂ / W ₁ ) ² Z _2m (t) are determined taking into account the parameters of the transformer. Figure 4 shows that on points AA through the interface device 2, in addition to the AP with the level of U _2n (t), an MP with the level of U _2m (t) acts, changing the resistance z _2m (t) of the PCA section between these points, i.e. stochastic AM of the mixture of the KI signal and the AP circulating in the SAR is carried out. A special case of stochastic AM corresponds to x _2m (t) = const; The special case of stochastic CM corresponds to r _2m (t) = const. The condition for the absence of stochastic modulation (see the description of the prototype method) is r _2m (t) + jx _2m (t) = const.

Diagrams of two transformerless variants (similar to the transformer version of Fig. 3) for connecting to a PCA modulator 4 with complex internal resistance Z _2m (0 is illustrated in Fig. 5 ( a - galvanic connection through resistors R _P ; 6 - capacitive connection through capacitors C _P ).

Fig.6 shows graphs of the dependence of the probability p _{n of} erroneous reception of KI signals on the signal-to-noise ratio h ² under the combined and single exposure to simulated noise of the AM-2 or FM-2 type with levels from 0.1 to 0.5 from the level power of the KI signal: a ) KI signal AM-2; b) KI signal FM-2; solid lines - calculation results, thickened points - data of statistical computer simulation; Charts 1-3 - the combined effects of interference AM-2 and FM-2; graphs 4-6 - exposure to a single interference FM-2. The graphs of Fig. 6 prove the effectiveness of the combined use of simulation interference of the AM-2 and FM-2 type for PCA protection in the range of signal-to-noise ratio h ² ≤128 and signal-to-noise ratio 0.1 ... 0.5. From a comparison of pairs of curves 1 and 4; 2 and 5; 3 and 6, the respective joint and a single use of said interference, it is seen that the predicted probability of erroneous reception p _oui CI-signal as the modulated-2 AM and FM-modulated to 2, with the combined effect on the interference attacker TC significantly

increases (with the exception of curves 1 and 4 of Fig. 6 a for h ² ≥2, when the _osh with a single interference FM-2 is so large that the SAR does not really need protection with the help of additional interference).

The solid lines in the graphs of Fig. 6 correspond to the calculation results by the method [12-13], the thickened points correspond to the data of statistical computer simulation (the sample size for each point of the curve in Fig. 6 is 1677239 information symbols; the test KI signal represents one period m-sequences 16777216 = 2 ²⁴ characters long and an additional 23 zero characters at the end, and the imitation interference is a pseudo-random sequence of 1677239 characters [12-13]).

The data of Fig. 6 show, firstly, that when protecting the SAR to prevent leakage of CI [3-8], along with noise APs U _w (t), it is advisable to use simulation MPs formed using U _u (t). Secondly, the use of simulated MP U _u (t). In the protection system that is identical to CI signals but does not contain CI allows even with significant ratios of signal-to-noise levels h ² and an optimal method of signal demodulation in an attacker's TS to provide r _osh ≈0.5. Thirdly, that the MP emitters for the region h ² ≤128 should provide single interference levels of at least half of the power level of the KI signal type FM-2 and at least a quarter of the power level of the KI signal type AM-2 - this suggests that for the considered KI signals, the type of FM-2 modulation of single MPs is more preferable. Fourth, and most importantly, interference of the FM-2 and AM-2 type is best used together - especially if the type of modulation of the KI signal in the SAR is unknown - while the MP power levels in the region of large values of h ² can be 0.15 ... 0.2 of the power level of the KI signal.

The proposed method is universal and simple, it is convenient for implementation and automation, it allows to increase the efficiency and environmental friendliness by the electromagnetic factor of the PCA information protection system.

LITERATURE

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Claims (1)

A method for protecting a distributed random antenna, including connecting to a distributed random antenna through N interference device couplers that provide protection for a distributed random antenna, characterized in that M amplitude modulators are introduced into the M + K from among the N coupler devices, which under the influence of M from the number N of interference generators carry out stochastic amplitude modulation, as well as K of angular modulators, which under the influence of K from among N interference generators carry out stochastic Glov modulation information and interference signals emitted by a random distributed antenna.

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