Method for protection of speech data signal, transferred along communication lines

FIELD: technologies for preventing interception of data.

SUBSTANCE: transferred signal is concealed via adding noises to communication line in speech frequency range with linear addition of speech data signal with noise signal of higher level. Concealment is removed via adaptive filtration of received signal with compensation of noise component and separation of data component. Addition of noises to communication line is performed from the side of sensor. Noise signal during addition of noises and adaptive filtration is formed of a sum of counts of several noise series with nonevent sizes via their random querying. At the beginning of each communication session a signal is sent to side of receiver, characterizing order of querying of series, and starting signal, providing for synchronism of noises addition and filtering processes. All operations are performed by means of microprocessors, mounted on both sides of communication line, dependently of loaded software providing for change of direction of transmission and protection of speech data signal. Invention allows to simplify protection while providing for absolute confidentiality of transmitted data.

EFFECT: higher reliability.

6 cl, 4 dwg

 

The invention relates to communication technology, mainly with a telephone or other wired connection) lines and is intended for use in counteracting commercial and industrial espionage.

There are ways to avoid listening to the talks on the telephone line, based on the generation of in-line noise, preventing the dial from outside, are connected in parallel, telephone or hinder the perception of it speech signals due to their masking (FR 2655224 A1, 31.05.1991; EN 92006880 AND 20.01.1995; EN 14794 U1, 27.08.2000; EN 2054812 C1, 20.02.1996).

The disadvantages of the known technical solutions are determined by their complexity and the need for significant upgrading of existing telephone systems.

The closest to the invention is a method of protection of speech information signal transmitted over a wired communication lines, from unauthorized eavesdropping, according to which the exercise on the receiver side masking of the signal being transmitted by the degradation of the communication line in the speech frequency range with a linear addition of speech information signal from exceeding its level noise signal, and demeterova there by adaptive filtering of the received signal with the compensation of the noise component and the release of information is leaving (EN 2112319 C1, H 04 To 1/00, 27.05.1998; EN 2195785 C1, H 04 M 1/68, 27.12.2002 - prototype).

However, to ensure the quality of protection used in the known method the noisiness of the line on the receiver side does not eliminate the need for additional protective measures on the side of the transmitter, including coding of speech information signal, with considerable difficulty implementing method.

Object of the invention is the simplification of protection to ensure absolute confidentiality of transmitted information. The technical result is expressed in increased reliability of communication subscribers without risk of being overheard.

The problem is solved in that in the method of protection of speech information signal transmitted by the communication lines from unauthorized eavesdropping, according to which perform masking of the signal being transmitted by the degradation of the communication line in the speech frequency range with a linear addition of speech information signal from exceeding its level noise signal, and demeterova by adaptive filtering of the received signal compensated noise component and an information component selection, the noisiness of the line of communication from the transmitter, the noise signal in the noise and adaptive filtering form of su whom we count several noise sequences with unequal sizes by their random survey moreover, at the beginning of each communication session to transmit over the communication channel at the receiver side the signal characterizing the polling order of the sequence, and the starting signal providing simultaneous processes of degradation and filtering.

The task promote private significant features of the invention.

All composite operations are performed using established on both sides of the line of microprocessors, which, depending on downloaded programs changing the direction of transmission and protection of the speech information signal.

During the formation of the noise signal from session to session from each recorded in the memory of the microprocessor sequence take on one count, put them and throw in a line and when you reach the end of any sequence is transferred in its beginning, while the spectral density of the noise signal are distributed uniformly in the frequency range of the information signal and the received signal level adjust via AGC.

The noisiness of the line-side transmitter and adaptive filtering of the signal at the receiver side is performed using the implemented chip noise generators with identical characteristics, while on the receiver side is performed by the frequency of the clock generator, part of the gene is atora noise.

The polling order of the sequences passed on the wire and take out of it with the help of the implemented chip modems.

On the receiver side the transmitted start signal detect mode in continuous scan detector using the scheme of the SHOW.

Figure 1 shows the General structure of the communication system with protection under the proposed method. Figure 2 and 3 shows a functional diagram of subsets of the transmitter and receiver. Figure 4 shows the functional scheme used on the receiver side of the start signal detector.

The communication system includes a transmitter/receiver 1 (1), wire, such as a phone, the communication line 2 and the receiver/transmitter 3. Below, the operation of the communication system and its protection when working in the terminal 1 in transmitter mode, and the terminal 3 - mode receiver.

In the transmitter 1 includes a microphone 4 (figure 2), the generator 5 noise shaper 6 service signals (of the order of the survey), the modem 7, a driver 8 start signal and linear node 9.

In the receiver 3 includes a linear node 10 (3), the detector 11 start signal, the synchronization block 12, a modem 13, the adaptive filter 14, block 15 automatic frequency and telephone 16.

Linear nodes 9 and 10 together with line 2 forming the communication channel.

The detector 11 starter is ignal includes a limiter connected in series 17 (4), the frequency detector 18, a filter 19 lowpass bandpass filter 20 and the threshold block 21.

The principle of protection against unauthorized listening, as already mentioned, based on the transmission of speech information signal, disguised noise hindrance, followed by demeterova at the receiving side, where the noise level is much higher than the informational component. As the noise used analog noise with the spectral density of the voltage evenly (or any other way) distributed in the above frequency band. A distinctive feature of this protection is that the noisiness of conduct on the part of the transmitter 1, and the amplitude-frequency response of the communication channel is neither transmitting nor receiving side of the communication channel is unknown, and the noise characteristics close to the characteristics of thermal noise.

Complete functional subsets of the transmitter 1 and receiver 3 located at opposite ends of the communication line 2, executed on microprocessors and are only loaded into their programs. At any point in time, each of them may act as a transmitter and as a receiver.

One of the main nodes of the transmitter 1 is the generator 5 noise. As in the receiver 3, and in particular in the adaptive filter 14, there should be a noise generator with the absolute is about the same characteristics, this requirement has imposed certain restrictions on the choice of the method of forming a noise sequence.

The signal generator 5 noise is generated from the sum of several noise sequences (6 sequences)stored in the memory of the processor with the capacity and resources of the processor. The number of times each sequence is a Prime number, and the dimensions of the sequences are not equal. This is done in order to increase the repetition period of the total sequence. If each sequence to take on one count, fold them up and give to the communication channel, then do the same with the next count, and when you reach the end of the recorded sequence to move in its beginning, the repetition of the total sequence may occur over tens of millions of years when the total number of counts of sequence not more than 10,000, which is quite a bit for modern microprocessor.

To exclude the frequency of the noise signal from session to session, in the transmitter 1 is implemented such an algorithm run the generator at which the poll each of the six sequences is performed in an arbitrary order, i.e. each session begins with a survey of the memory cells with arbitrary addresses. At the beginning of each session paradoxopoda sequences using a modem 7 transmitter 1 is transmitted over the communication channel to the input of the receiver 3, where accepted by modem 13. The modem 7 and 13 are only in the initial stage of communication and, thus, are intended only for the transmission Protocol of the survey.

In addition, the signal transmitter 1 provides the synchronization signal is the start signal, from which noise generators of the receiver 3 and the transmitter 1 are synchronously.

Structurally, the receiver 3 does not differ from the transmitter. The difference is in the programs that perform the receiver 3 and the transmitter 1. The detector 11 starting signal receiver 3 based on the following scheme SHOWS (broadband filtering - restrict - narrowband filtering), which together implement the blocks 17-21. The detector 11 is in constant scanning, that is, constantly analyzes the presence at the input of the receiver 3 start signal. After detecting a starting signal receiver 3 is transferred sequentially in the processing modes of service signals of the synchronization signal and the working of the noise signal.

The main problem solved by using receiver 3, is the separation of signal information and noise components. This task is performed by the adaptive filter 14, which contains a noise generator similar to the generator 5, and compensate the noise component received by the receiver 3 signal. The adaptive filter 14 is manifested in his Pris is osoblivosti to the existing noise.

Using the filter 14 is also automatic frequency control automatic fine tuning the clock frequency of the reference oscillator of the receiver to the frequency of the same generator of the transmitter 1.

To ensure more stable operation of the adaptive filter 14 and all communication systems in General, in the receiver 3 has a mechanism AGC - automatic gain control. The AGC algorithm is quite simple, as the input of the receiver 3 during the entire communication session continually present a noise signal with a fixed level, in 12 to 16 times higher than the level of speech information signal. In this case, once is enough to measure the signal level at the receiver input 3 and using the appropriate program to install the required gain of the receiver 3. This algorithm eliminates harmonic distortion of the input signal associated with the constant tracking of a signal level and a constant change of the gain of the receiver 3.

1. Method of protection of speech information signal transmitted by the communication lines from unauthorized eavesdropping, according to which perform masking of the signal being transmitted by the degradation of the communication line in the speech frequency range with a linear addition of speech information signal from exceeding its level noise signal, and demeterova through the om adaptive filtering of a received signal compensated noise component and an information component selection, characterized in that the noisiness of the line of communication from the transmitter, the noise signal in the noise and the adaptive filter is formed from the sum of the counts of several noise sequences with unequal sizes through their open-ended survey, and at the beginning of each communication session to transmit over the communication channel at the receiver side the signal characterizing the polling order of the sequence, and the starting signal providing simultaneous processes of degradation and filtering.

2. The method according to claim 1, characterized in that all composite operations are performed using established on both sides of the line of microprocessors, which, depending on downloaded programs changing the direction of transmission and protection of the speech information signal.

3. The method according to claim 2, characterized in that when forming the noise signal from session to session from each recorded in the memory of the microprocessor sequence take on one count, put them and throw in a line and when you reach the end of any sequence is transferred in its beginning, while the spectral density of the noise signal are distributed uniformly in the frequency range of the information signal and the received signal level adjust via AGC.

4. The method according to claim 2 or 3, characterized in that cluttered the e line connection on the transmitter side and adaptive filtering of the signal at the receiver side is performed using the implemented chip noise generators with identical characteristics, at the receiver side is performed by the control clock generator included in the noise generator.

5. The method according to claim 2, characterized in that the polling order of the sequences passed on the wire and take out of it with the help of the implemented chip modems.

6. The method according to claim 2, characterized in that on the side of the receiver transmitted start signal detect mode in continuous scan detector using the scheme of the SHOW.



 

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