RU2185034C2 - Device for protecting telephone line against unauthorized access to trunk communication system - Google Patents

Abstract

FIELD: telephone communications; protection of trunk communication system users from unauthorized access. SUBSTANCE: device is installed in telephone exchange at line input of telephone set user and has counter and speaker verification module, their inputs being connected to communication line and outputs, via INHIBIT gate to control input of switch connected in parallel with communication line through shunt; speaker verification module is connected to memory unit wherein user s password is entered. EFFECT: enhanced reliability of protecting users of wire and radio telephone sets against unauthorized access. 2 cl, 1 dwg

Description

 The invention relates to techniques for telephone communications and can be used to combat telephone piracy, namely, to protect telephone networks from unauthorized use of subscriber numbers for long-distance or international calls.

 Currently, devices for making telephone calls based on the analysis of information accompanying the telephone call itself are widely known [1]. The subscriber's telephone call is routed over the telephone line to the terminal equipment block of the automatic telephone exchange (PBX), which analyzes the information accompanying such a call. This information is divided into independent call attributes, such as the calling number and the called number. After that, a search is made in the number list and it is checked whether it contains an entry corresponding to the attributes of the call. If no match is found, the call is rejected. If one or more matches are found, the call is routed according to the information contained in that number list entry that has the most optimal match. Moreover, the user has the ability to easily modify the number lists. However, in this case, telephone communication cannot be sufficiently protected from unauthorized interference, and the information that accompanies a telephone call is not personified enough to solve such problems.

 Similar disadvantages are also present in the voice notification system, which provides transmission from an electronic telephone exchange of information such as a message about a changed number, a message about the absence, a message about the absence of interference, a message of its own number, a message of an outgoing call number and a message of selective speech of an incoming call [2]. When providing various additional services, such a system does not provide the main thing - protecting the telephone network from outside interference, especially when using paid long-distance and international calls.

 Abroad, the costs associated with telephone piracy are estimated at billions of dollars a year and continue to grow. Despite many forms of such piracy, two main categories prevail in modern networks: service intervention and subscription piracy. Service interventions include, for example, the illegitimate use of calling cards, mobile phones or telephone lines, while subscription piracy occurs when an intruder who does not intend to pay for a service claims to be a new consumer. The latter type of piracy is the most difficult to determine and in any case, losses from such types of piracy are a significant problem. In existing telecommunication systems, the identification of persons illegally using cards, mobile phones, telephone lines, subscriber accounts, etc. it is possible only some time after their activity is quite long, that is, such systems do not respond to illegal users in real or near real time.

 One of the effective ways of establishing the owner’s authenticity is voice verification, in which the caller’s speech sample is compared with previously stored “voice prints” [3]. The type of data entering the authentication unit varies depending on the method used, for example, the analysis of voice prints, the analysis of other biometric characteristics, a password word, etc. The subscriber is instructed to dial a specific number, which is interpreted as a request to establish communication with the authentication system. The system accumulates data on the basis of a specific authentication method (password words, voice verification, etc.) and the corresponding calls are marked for identifying the intruder by the likelihood principle, the probability of the presence of the intruder for each call is evaluated taking into account the behavioral characteristics of the particular subscriber and the intruder. If the authenticity of the subscriber, that is, the owner of the number, is established, then the regular call continues, and if the voice prints do not agree with the received and accumulated speech images, then such a call is blocked.

 The disadvantage of such a system is usually due to the fact that the owner’s authentication algorithm leads to the need to interrupt each call, which causes certain inconvenience for legal subscribers. In addition, such a system due to the complexity of the equipment (special external systems or a service management system were used to collect authenticity information) leads to significant material costs and unjustified delays in processing calls over the network.

 A known security system for data transmission over the telephone network, which contains an authorized user device and user verification system [4]. The user's portable device is easily compatible with a telephone (including a mobile one), a computer or a microphone for transmitting the so-called “DTMF” tones (multi-frequency signals of a dual-tone dialing keypad) to a verification system available for the telephone network.

 A user device, in one embodiment, stores voice data representing voice characteristics of an authorized user and access code data to a verification system. In another embodiment, the user device generates standard tones representing the region of the frequency spectrum in which the user's voice lies. User identification information includes data related to user characteristics such as user-selected identification numbers or words (e.g., password words or passphrases), identifying characteristics (e.g., eye color, place of birth, etc.), as well as spectral representation , semantic structure, user voice rhythm. The verification system based on the data spoken by the user determines the level of certainty at which the current pronunciation is consistent with the pronunciation of the user who has his user device. In determining the significance and authorized user, the verification system serves as a channel for user access to various service systems, such as telephone or banking system, mail order companies, the Internet and others. Typically, the system processor asks the user to pronounce a password or passphrase into the handset, and for greater security, it may require the introduction of a personal identification number through the keypad of the telephone or computer. After the amplitude correction of tone signals representing the current speech data, the processor transfers the stored speech data from the memory module to the analyzer, which compares the speech data with the tones of the current speech sample representing the user’s password word or passphrase, making recognition independent of the speaker. The analyzer then determines that the confirmed password word or passphrase is the same as it is stored in the memory module, and also determines that the speech frequencies representing the user-approved password word or passphrase are the same as they are stored in the memory module. Typically, when the likelihood of tones matching the stored speech data is more than 80%, the user is considered authorized.

 The disadvantage of such a system is its complexity, requiring significant modification of the end equipment of the network and subscriber units. Each such device must be equipped with a user device that stores speech samples and works in dialogue mode with a verification system, and the intruder can use his specially equipped device. To access the verification system, tones of various categories are used, as well as temporary signals and warning signals. In addition, when the analyzer determines the matching within 60% -80%, i.e. the state of uncertainty, the system will additionally ask the user a number of questions for recognition, dependent on the speaker and not related to speech files, such as data on the individual identification number, the first four digits of the number, the last four digits of the number, social policy number, date of birth, the maiden name of the mother, the names of the children, the dates of birth of the children and the like, and access is denied only if the answers to all the questions are incorrect. With individual incorrect answers, the system repeats some questions and may even ask for the user's address in an attempt to detect the intruder. All this creates inconvenience in gaining access, for example, to a telephone line for a fairly quick connection when conducting long-distance or international calls.

 To partially eliminate the noted drawbacks, a fairly simple device is known for protecting telephone communications from unauthorized access, made in the form of a long-distance code blocker with a limited number of digits [5]. Typically, the maximum number of digits of a long-distance call number does not exceed eight, while long-distance calls are made by dialing nine digits: “8” + area code (at least three digits) + number of the called party (at least five digits), and for an international — more than nine digits . Thus, if you limit the number to eight digits, you can insure yourself against unauthorized use of the number for expensive long-distance and especially international calls. To do this, the device includes a current sensor, a PBX call filter, a bar time limiter, a count pulse generation circuit, a counter and a key. The pulses generated by the current sensor arrive at the counter, which counts the groups of pulses, that is, the number of digits of the dialed number. When eight digits are reached, the counting stops and a key is turned on from the meter’s output, through which the line is shunted by the load resistance. By blocking the corresponding discharge of the counter, dialing becomes impossible for 10-12 s, which is determined by the time constant of the charging circuit of the prohibition time limiter. The protective effect is achieved by the fact that on all long-distance exchanges, due to their high load, the waiting time for each digit of the number is reduced. If during the dialing of the long-distance code, a pause occurs between the digits for more than 8-10 s, the telephone exchange hangs up the line even with the subsequent dialing by the intruder of the digits of the number.

 The disadvantages of this device are the ability to access long-distance communication by replacing the subscriber’s device with another device that does not have such a device, and the need to pause when dialing long-distance numbers, the duration of which is determined by the parameters of the PBX call filter, which creates inconvenience for the subscriber. The use of a current sensor connected in series with a telephone while receiving a pulse code does not allow line protection when a pirate device is connected in parallel, since when the main telephone is hung up, dialing pulses are not perceived by such a current sensor. If such a device is installed on the PBX, then the legitimate subscriber will not be able to use long-distance communication if necessary, since there is no possibility of its remote disconnection. The device does not solve the problem of countering piracy for radiotelephones.

 For radiotelephones, pirated connections in the radio channel zone are most often used, when the portable unit is imitated using a scanner, making unauthorized long-distance communication from neighboring rooms. In the case of cellular telephones, connections are made in the cellular communication area at radio frequencies. To protect cordless telephones, a coded line access device via a single digit or a line coding device using a pulse two-digit code is used [6].

 In a coded access device, when the handset is removed from the device, the line is also shunted by the load resistance, but due to the presence of a current sensor, it is possible to receive one digit of the code selected by the switch. If this number is correctly dialed, the key is disabled and the line is free for further dialing. The line coding device uses a line voltage sensor, which eliminates unauthorized access from a parallel device, as in the case of a serial current sensor (see above). Pulses when formed directly on the linear wires of the line, that is, they are perceived by the PBX equipment as a set of the first two digits of a regular number. Such line protection devices can be used in conjunction with a radiotelephone or a conventional device when simple code protection is required against all types of connections. The last device can also be installed on the PBX output terminals, then it prevents the illegal use of the line even if the loop of the PBX subscriber is broken.

 However, when installing the described devices in stationary units of radiotelephones and if they are disconnected and connected to a conventional device, pirated long distance communication can be carried out without hindrance. The disadvantage is the need for a constant set of special code digits for access to the line.

 Closest to the proposed one is a device for protection against unauthorized access to automatic long-distance and international calls, containing a voltage sensor, a counter start-up preparation circuit, a counter, a ban enable circuit, a key, and a shunt resistance [7]. When you remove the handset of the telephone set, the counter of the device connected in parallel to the device starts counting pulses after 1.5-2 s, after dialing the number "8" or any combination of calling the operator (for example, "07") and a short pause (waiting for a long dial tone ) upon the output of the corresponding discharge of the counter, the key is turned on, the line is shunted by a small resistance and further dialing becomes impossible.

 Such a device does not require a set of special codes. However, it has an insufficient degree of protection due to the possibility of access to the line by replacing the subscriber’s device with another device that does not have such a device. A similar protection problem for radiotelephones is not resolved. Thus, the above mentioned disadvantages are also inherent in such a device.

 The problem to which the invention is directed is to create a device that provides reliable protection against unauthorized access to telephone networks from both wired and radiotelephones during long-distance and international calls with the number of legal subscribers.

 To achieve the goal, a device for protecting the telephone line from the block is connected with a counter, connected to the communication line by a counting input, and a corresponding output output with a control input of a key connected in parallel to the communication line via a shunt element, and a verification module is introduced the password memory of the owner of the number, the input of which is connected to the communication line, and the output is connected to the inverting input of the "Prohibition" logic element, the non-inverting input of which oedinen with the counter output, and the output - to the control key input, the apparatus taken on the automatic telephone exchange subscriber line at the input.

 Preferably, the speaker verification module is configured to process the intonational, spectral and / or semantic features of the user's voice.

 The device is installed on an automatic telephone exchange (PBX) and connected to a communication line at the input of a subscriber's number on an automatic telephone exchange. The verifier memory module can be configured to store a large number of subscriber passwords. The device can perform additional services to the subscriber from the PBX after identifying his password.

 The counter circuit can be configured to receive the first digit of the code and the second digit of the code without pauses between them or limit the number of digits of the dialed number or prohibit the sum of the digits of the number with coded access to the communication line. This extends the range of blockers used, some of which are mentioned above.

 The invention is illustrated in the drawing, which shows a structural diagram of the proposed device.

элемента 7 подключен к ключу 8, включенному параллельно линии 3 связи через шунтирующий элемент 9 (например, резистор около 3 кОм или конденсатор для тонового режима набора или RC-цепочку). Счетчик 5 может быть выполнен на микросхеме К561ИЕ8, а логический элемент 7 и ключ 8 - на микросхеме КР1014КТ1А аналогично [6, 7]. Модуль 6 верификации связан с блоком 10 памяти, имеющим достаточную емкость для хранения заранее записанного пароля абонента или паролей всех АТС (при объединенной памяти).Device 1 for protecting the telephone line from unauthorized access to long-distance communication is switched on at the exchange 2 at the entry point of line 3 from the apparatus 4 of the subscriber user. The device 1 contains a counter 5 and a verification module 6, connected by their inputs to the communication line 3, and outputs - with a logic element 7 that performs the prohibition function. In this case, the output X _{1 of the} counter 5 is connected to the direct input of the logic element "Prohibition" 7, and the output X _{2 of} the verification module 6 is inverted. Exit

Element 7 is connected to a key 8 connected in parallel to the communication line 3 through a shunt element 9 (for example, a resistor of about 3 kΩ or a capacitor for tone dialing mode or an RC circuit). The counter 5 can be performed on the chip K561IE8, and the logic element 7 and key 8 on the chip KR1014KT1A similarly [6, 7]. Verification module 6 is connected to a memory unit 10 having sufficient capacity to store a pre-recorded subscriber password or passwords of all PBXs (with combined memory).

 Known modules for recognizing and verifying a user by his voice usually form several typical parameters according to the standard sentence or password word spoken by the user and compare them with the average parameters stored in the memory unit [8]. Based on the results of the comparison, probability values are generated that the sentence is pronounced by the corresponding user, and this value is compared with a threshold value. If this value exceeds the threshold value, the module considers that the user is verified.

 Systems are also widely known that automatically identify and recognize the speaker, providing him access to communication channels or the user's system [9], or use cards that store speech samples [10, 11]. Speech recognition modules are widely known in other fields of technology, for example, in the automation of checkpoints in institutions and the development of “voice keys” that provide authorized access for certain individuals to data banks or special-purpose mechanisms on the basis of the presentation by these persons of a certificate of identity of their speech [12 , 13], as well as in security systems when organizing access to telecommunication communication channels based on speech recognition [14], in addition to those mentioned above.

 The device operates as follows.

Линия 3 связи шунтируется сопротивлением 9 и дальнейший набор номера становится невозможным. Так осуществляется защита от несанкционированного доступа к международной связи с любой точки линии от аппарата 4 до входа в АТС 2.After removing the handset of the telephone set 4 on the device 1, connected in parallel with the device, the supply voltage appears and after 1.5-2 s the counter 5 and the verification module 6 are ready for operation. If the digit “8” is then dialed (access to long-distance or international calls), then at the output of counter 5 a signal X ₁ = 1 appears, which, in the absence of a ban from verification module 6 (X ₂ = 0), closes key 8 through logic element 7

Communication line 3 is shunted by resistance 9 and further dialing becomes impossible. This provides protection against unauthorized access to international communications from any point on the line from device 4 to the entrance to ATS 2.

и ключ 8 не замыкаются. Линия связи работает в обычном режиме, позволяя дальнейший набор номера и междугородные переговоры.For authorized access to intercity communication, the number owner, simultaneously with dialing the number "8", speaks his password (word, number, set of numbers, phrase for a few seconds) to the handset. In the verification module 6, the incoming password is compared with the number owner password stored in memory 10 in advance. If the passwords match, then at the output of the verification module 6, a signal X ₂ = 1 appears, which is fed to the inverting input of the logic element 7. The output voltage of the element 7

and key 8 does not close. The communication line operates as usual, allowing further dialing and long-distance calls.

When dialing any number that does not start with the number "8" (long distance communication), the signal is X ₁ = 0 and, regardless of the signal of the verifier (X ₂ = 0 or 1), the output of logic element 7 is voltage Y = 0, key 8 is not closed and the communication line is operating in normal operating mode.

The output X _{2 of} the verification module 6 can be used to access the subscriber to additional PBX services, for example, to bank payments by phone, since the presence of the signal X ₂ = 1 confirms the authenticity of the password and voice of the number owner.

 Using the speaker verification module as part of telephone communication devices allows you to create a security system that is practically not subject to outside interference, since the user's speech characteristics cannot be simulated by unauthorized persons. This allows us to solve the problem precisely in relation to systems for protecting telephone communications from unauthorized access.

 The user's voice can vary in spectral composition depending, for example, on the physical condition of the user (in particular, illness) and in this case the speaker verification mode can change, for example, according to the intonational and semantic features of the voice, the password word in the mode of independence from the speaker, and so on. like that. Various capabilities of the verification and recognition module can be implemented algorithmically on the basis of several or even one chip, which allows you to create a compact design of the device as a whole.

 Installing the device on the input terminals of the PBX eliminates the possibility of using extraneous devices of intruders. The absence in this case of a dialogue mode during verification reduces the time of authorized access, which represents additional convenience to subscribers. All this increases the effectiveness of counteracting the currently widespread telephone piracy.

Sources of information
1. RU 2099895 C1, MKI H 04 M 1/66, publ. 1997.

 2. RU 2118061 C1, MKI H 04 M 3/50, publ. 1998.

 3. WO 99/52261, MKI H 04 M 3/38, publ. 1999.

 4. WO 97/31472, MKI H 04 M 3/38, publ. 1997.

 5. I. N. Balakhnichev and others. “The fight against telephone piracy", Minsk, OOM "Our city", 1999, p. 82-86.

 6. Ibid., Pp. 86-97, 118-119.

 7. Ibid., Pp. 78-80.

 8. EP 0154020, MKI G 10 L 5/06, publ. 1985.

 9. US 4837830, MKI G 10 L 5/06, publ. 1989.

 10. US 4961229, MKI G 10 L 5/06, publ. 1990.

 11. US 4827518, MKI G 10 L 5/06, publ. 1989.

 12. SU 1453442, MKI G 10 L 9/06, 1989.

 13. SU 1675936, MKI G 10 L 9/06, 1991.

 14. EP 0533396, MKI G 07 C 9/00, publ. 1993.

Claims (2)

 1. A device for protecting a telephone line from unauthorized access to long-distance communication, comprising a meter, the input of which is connected to the communication line of the device with an automatic telephone exchange (PBX), and a key connected in parallel to the communication line through a shunt element, characterized in that a verification module is introduced the caller’s password talking to the memory unit and the “Prohibition” logic element, the output of which is connected to the control input of the key, while the input of the speaker verification module is connected to the communication line, and the output to the inverter to the input of the logic element "Prohibition", the output of the corresponding discharge of the counter is connected to the non-inverting input of the logic element "Prohibition", and the inputs of the counter and the speaker verification module are connected to the input of the communication line on the exchange.  2. The device according to p. 1, characterized in that the output of the speaker verification module is the subscriber’s access to additional PBX services.