RU2492581C2 - Method for information protection in distributed random antenna - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: distributed random antenna protection device has N interference generators (3) connected to the distributed random antenna through corresponding interface devices (2), and M nonlinear elements (4), where M is less than or equal to N, which are included in the distributed random antenna, wherein each of the M interface devices is connected to the corresponding nonlinear element, through which under the effect of M<N interferences, random integrated-differential frequency conversion of information signals and interference emitted by the distributed random antenna is carried out.

EFFECT: high efficiency of protecting a distributed random antenna on confidential information leakage channels.

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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, united 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 PPP - systems and power supplies, 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) to protect SARs are often not applicable. The main and most promising means in this case is the active protection of CI - using various kinds of deliberate interference (obstructive noise, imitation sighting, etc.). 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 active defense of CI, it is necessary by all available means - including new scientific and technical ideas - to increase its versatility and effectiveness.

The following methods are known for active protection of CI, based on the use of deliberate interference designed to energetically (for masking noise interference) or by causing maximum information damage (for imitation interference) to "suppress" CI - signals in all potential leakage channels to make it difficult for an attacker to intercept and treatment of CI with the help of the available TS [3-5]:

- linear noise, which is implemented using a noise generator that delivers a signal with a level of U _W (t) in 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 surrounding space (which is necessary to improve the electromagnetic compatibility of the vehicle and ensure the safety of working conditions of KI personnel and consumers) [5].

From the level of technological development, methods of amplitude and angular (frequency, phase) signal modulation are known [6]. There is a proposal to use channels obtained by sum-difference conversion in the frequency domain for covert communication between subscribers using reflective surfaces with controlled parameters [7]. The corresponding methodological apparatus for assessing the effectiveness of non-linear radio communications and radio suppression is described in [8]. There is also a method of determining signal attenuation in SAR, based on the use of a nonlinear sum-difference frequency (RF) conversion [9].

The closest in technical essence is the method of linear noise [3, p.188, Fig.8.9] (prototype of the invention), which, in relation to the conditions of the problem, involves connecting intentional jammers to the RSA through N devices that provide RSA information protection . The considered KI signal in a given time-frequency domain is U _c (t) = U ₀ (t) cos Φ (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 + Ω ₁ (t), where ω _c and φ _c are the carrier frequency and phase of the carrier signal, respectively, 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 _c (t); during phase modulation (FM), on φ _c (t).

Intentional interference according to the principle of influence on the KI signal can be divided into two categories: additive interference (AP) U _AP (t), which meets the condition U (t) = U _с (t) + U _AP (t) - signal received by the attacker ; and the multiplicative interference (MP) U _MP (t), corresponding to U (t) = k _MP U _c (t) · U _MP (t), where k _MP is a dimension coefficient depending on the method of MP implementation. 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 SAR information protection by using an attacker to use known methods for detecting and improving 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]. This becomes possible largely due to the fact that the frequency energy spectra of the KI signal G _c (ω, t) and noise interference G _P (ω; t), where ω is the circular frequency, are in no way interconnected and vary in time independently apart laws.

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 [12-14]. These requirements contradict each other, which complicates the possibility of implementing this PCA protection method. The use of simulation interference also complicates the need for constant synchronization of interference with the KI signal.

In order to eliminate the disadvantages inherent in the prototype method, the present invention proposes to associate the spectra of the KI signal G _c (ω; t) and the intentional interference G _P (ω; t) using the stochastic RF conversion of the KI signal U _C (t) and interference U _P (t) on a nonlinear element (NE), introduced for this purpose in the composition of the SAR.

After the UHF conversion, the total spectrum of the KI signal and the interference takes the form G _CP (ω _mn ; t), where ω _mn = | m ω _c ± n ω _П |; m; n [1; 2 ...] are the conversion coefficients that determine the order of m + n components of U _mn (t) in the converted signal U _SP (t). In accordance with the accepted terminology [10], when the NE is interfered with by U _P (t) by SLs that are part of the SAR, the used RFM conversion is an analogue of the Raman conversion, and when external influence of the noise by ether is an analog of the intermodulation conversion.

The technical result of the invention is to increase the efficiency of information protection in SAR by using a joint RF conversion of the KI signal U _C (t) with the energy spectrum G _C (ω; t) and intentional interference U _P (t) with the energy spectrum G _P (ω ; t) on the NE introduced into the composition of the SAR, the result of which is the formation of a stochastically converted signal U _CP (t) with the spectrum G _CP (ω _mn ; t), where ω _mn = | m ω _with ± nω _П |; m; n [1; 2 ...] are the coefficients of the SHF transform, which determine the order m + n of its components U _mn (t).

The essence of the proposed method of protecting information in a distributed random antenna is that it provides for connecting to a distributed random antenna through N interface devices N interference generators that provide information protection for a distributed random antenna, and differs in that it consists of M from among N interface devices nonlinear elements are introduced, with the help of which, under the influence of M≤N interference, a joint stochastic sum-difference frequency conversion of information signals is carried out the crosstalk and interference emitted by the distributed random antenna.

Figure 1 shows a diagram of the implementation of the prototype - a known method of linear noise with reference to the SAR with a complex multi-story structure, where 1 - SAR in the form of a branched heterogeneous SL; 2 - interface device (total number N); 3 - intentional interference generator (total number M).

Figure 2 illustrates the implementation scheme of the proposed method of information protection in SAR, where 1 - SAR in the form of a branched heterogeneous SL; 2 - interface device (total number N); 3 - intentional interference generator (total number N); 4 - NE element conventionally shown as a semiconductor diode (total number M≤N).

Figure 3 shows embodiments of a device for interfacing an interference generator U _n (t) with a PCA connected to a PCA at points AA, in the presence of NE: a) using inductive coupling through a transformer; b) - using capacitive coupling through capacitors C _P ; c) - using galvanic coupling through resistors R _P , g) - using external exposure to interference from the antenna AP.

Figure 4 presents spectrograms for the signal circulating in the SAR when the noise generator and the 890 MHz signal generator are connected in it (upper curve); and with the 890 MHz signal generator turned off (lower curve): a) in the frequency band up to 2 GHz; b) - in the frequency band up to 3 GHz.

The known prototype method is as follows.

To the SL forming PCA 1 (see Figure 1), through N interface devices 2, interference generators 3 are connected, which protect the information in the PCA by generating instead of the KI signal circulating in it U _c (t) = U ₀ (t) cos Φ (t) of the mixture of signal and noise AP of the form U _with (t) + U _ш (t) = U ₀ (t) cos Φ (t) + U _ш (t). The frequency energy spectra G _c (ω; t) of the KI signal U _C (t) and G _P (ω; t) of the intentional interference U _P (t) are not related here (separated in the time-frequency domain). If necessary, reduce the AP levels necessary for effective PCA protection, instead of the noise AP, a simulation interference U _u (t) is used - similar in properties to U _C (t), but unrelated to modulating KI signals.

The main disadvantage of the prototype method is the ability to reduce the effectiveness of SAR information protection by using an attacker to use known methods for detecting and increasing the noise immunity of receiving 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] - which is facilitated by the mutual independence of their spectra G _c (ω; t) and G _П (ω; t). To eliminate this, it is proposed to relate the spectra of the KI signal G _c (ω; t) and the intentional interference G _P (ω; t) using the SRF conversion of the KI signal U _c (t) and the interference U _P (t) on the NE introduced in the composition of the PCA.

The proposed method is as follows.

To the SLs forming PCA 1, through N interface devices 2, which include NE 4 (see Figure 2), interference generators 3 are connected that provide informational protection of the PCA similarly to the prototype method - however, taking into account the stochastic KF signal U _c (t) and interference U _P (t) on each of M≤N NE 4. After the RF conversion, the KI signal and interference spectrum takes the form G _CP (ω _mn ; t), where ω _mn = | m ω _with ± nω _P |; m; n [1; 2 ...] are the conversion coefficients that determine the order of m + n components of U _mn (t) in the converted signal U _SP (t). Thus, in this case, instead of the KI signal U _С (t) with the frequency energy spectrum G _С (ω; t) and interference U _П (t) with the spectrum G _П (ω; t), a common stochastic transformed signal circulates in the SAR U _SP (t). From the prior art [10-14], it is known, firstly, that it is substantially more difficult for an attacker to separate a KI signal and a noise having a joint stochastic spectrum G _SP (ω _mn ; t) than a signal and a noise having independent from each other the spectra G _С (ω; t) and G _П (ω; t). Secondly, that there is the possibility of dynamic control of the spectrum of G _CP (ω _mn , t) by changing the interference characteristics U _P (t). The result of this is a decrease in the noise immunity of receiving CI signals in the CI leakage channel and, accordingly, increasing the efficiency of information protection in SAR.

Figure 3 illustrates embodiments of a device 2 for coupling an interference generator U _P (t) 3 with a PCA 1 connected to it at points AA, in the presence of NE 4 in the form of a semiconductor diode: a) using inductive coupling through a transformer with a coefficient transformation W ₁ / W ₂ , where W _1,2 is the number of turns, respectively, in the primary and secondary windings; b) - using capacitive coupling through capacitors C _P ; c) - using galvanic coupling through resistors R _P ; g) - using external exposure to interference from the antenna AP.

Figure 4 presents the experimental spectrograms obtained using the Rode & Schwarz analyzer for a signal circulating in the PCA 1 when a noise generator 3 and a signal generator 890 MHz are connected in it (upper curves); and with the 890 MHz signal generator turned off (lower curves): a) in the frequency band up to 2 GHz; b) - in the frequency band up to 3 GHz. On the spectrograms of Fig. 4, the differences between the spectra G _C (ω; t) of the harmonic signal of 890 MHz are clearly visible - the emissions in the upper graphs; G _P (ω; t) noise interference - lower graphs; and the joint spectrum G _CP (ω _mn ; t) are the upper graphs.

The joint spectrum G _SP (ω _mn ; t) is noticeably more uniform and “stretched” in the high-frequency region (up to 2-3 GHz) compared to the interference spectrum G _P (ω; t), the harmonic spectrum G _c (ω; t ) against its background, is significantly less noticeable due to the appearance of new numerous components U _mn (t) after the UHF conversion. For real KI signals with a more complex form of G _c (ω; t), the stochastic UHF conversion complicates the task of the attacker even more and increases the efficiency of protecting the KI circulating in the SAR. The proposed method is universal and simple, it is convenient for implementation in automatic mode and improves the efficiency of information protection in PCA.

LITERATURE

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Claims (1)

A distributed random antenna (PCA) protection device containing N interference generators connected to the PCA through appropriate interface devices, and M non-linear elements, where M is less than or equal to N input to the PCA, with each of the M interface devices connected to a corresponding non-linear element.

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