JPH0715429A - Detection method of disapproved usage discrimination signal - Google Patents

Abstract

PURPOSE: To prevent a calling charge from being added to the charge of another subscriber by operating an identification signal which is likely to be obtained without any authorization due to the wire tapping of the exchange of information passing through a message transmission channel. CONSTITUTION: In a message transmission system, fixed data such as a subscriber number and the identification code of a subscriber's station stored in the subscriber's station are compared with fixed data stored in a switchboard and evaluated during the set-up of connection and evaluated. Then, additional variable data are allowed to exist in a subscriber's station T and a switchboard Z. A time of achieving connection with the switchboard, the fixed data and the variable data are both transmitted, compared, and evaluated. At the time of detecting the unauthorized use of an identification signal assigned to the subscriber's station, the number of times of the successful connection of the subscriber's station is used as the variable data, the subscriber's station and the switchboard are respectively provided with counters ZZ and ZZ1, and the counting positions of those counters are increased only by 1 at each time of successful connection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention In a message transmission system, the present invention stores fixed data such as a subscriber number and a subscriber station identification code stored in a subscriber station in a switch during connection setup. The fixed data and the variable data are transmitted together, evaluated, and the additional variable data is present in the subscriber station and the exchange, and when the connection to the exchange is achieved, the fixed data and the variable data are transmitted together, compared, and evaluated. Then
The present invention relates to a method for detecting unauthorized use of an identification signal assigned to a subscriber station.

To distinguish between different subscriber stations of a message transmission system, so-called identification signals can be used. Call charges are generally calculated based on the subscriber station identification code.

[0003]

2. Description of the Related Art In a radio transmission system, the charge calculation for a call started at a mobile radio station is performed by a radio exchange. German Patent No. 24.19.615
A subscriber station (mobile radio station) identification method capable of detecting unauthorized use of an identification signal (subscriber number and identification code) of a mobile radio station in a wireless transmission system is described. In the mobile radio station, the identification signal is stored in an identification signal generator, for example, a magnetic card. In order to operate a mobile radio station,
The identification signal generator is inserted into the slot of the control unit of the mobile radio station, the reading device of the control unit reads the data, and this data is supplied to the control device in the control unit. To prevent illegal duplication of the magnetic card based on the entry in the telephone directory where the subscriber number is stored, a second is given to each subscriber of the wireless transmission system.
The "secret" subscriber number (code) is given and stored in a magnetic card.

In the case of the German patent DE 24.19.615, the identity is checked by checking whether there is a correspondence between the subscriber identification code and the subscriber number. An identification code for identity verification, which is formed by using an encryption key unknown to the subscriber, is transmitted from the mobile radio station to the radio exchange. In the wireless exchange, the identification code given by the mobile wireless station is decrypted using the reverse encryption rule. The calling number (subscriber number) of the associated mobile station is obtained by a decoding operation using the identification code.

An illegal identification signal, for example an identification signal formed without using an encryption rule unknown to the subscriber, is actually decrypted by the wireless exchange and transmitted to the mobile radio station as an identification code. However, the identification signal thus obtained does not match the identification signal corresponding to the subscriber number of the mobile radio station. Therefore, if the received identification code is compared, for example, with an identification code receiver, to the subscriber number stored on the magnetic card, it is detected that they do not correspond and the established connection is cut off.

However, the method using a fixed encryption (encoding) rule provides almost no protection against an unauthorized identification signal obtained by unauthorized wiretapping of information exchange in a wireless transmission channel. I can't. When the exchange of information on the radio transmission channel is heard, the call charge for this mobile radio station is transferred to other radio transmission systems by operating the identification signal generator in the mobile radio station and the control device (identification code receiver). It can be charged to the subscriber.

Another public service is the teletext transmission system. TE KA DE Technical Report (TE KA DE Technisc
he Mitteilungen), 1980, page 21, Chapter 5, "Relay Scheme (Verbindungsaufbau)", states that the setup of the connection from the subscriber is initiated by activating the remote control of the television set. ing. If the line from the subscriber station to the teletext exchange is free, the automatic selection of the calling number assigned to the exchange starts after closing the loop necessary to supply the teletext modem (modulator / demodulator) with current. To be done. The subscriber number stored in the subscriber station, if a connection to the exchange can be made
(Identification signal) via the control device provided in the subscriber station,
Transmit to teletext exchange. For example, an identification signal consisting of up to the 11th place of the ISO (Information Standards Organization) 7-bit code and an additional check byte is used in teletext exchanges to check authorization and to check the correct calculation of charges. There is. Furthermore, provision may be made for the teletext exchange to request a so-called secret code (identification code) before it can access the information components stored therein.

Also in this case, the identification signal (subscriber number and identification code) may be heard using a method similar to that used for eavesdropping on telephone conversations,
The identification signal stored in the identification signal generator of the teletext modem can be altered for fraudulent purposes.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a call charge to a message transmission system by manipulating an identification signal that may be obtained without authorization by eavesdropping on the exchange of information over the message transmission channel. It is to prevent adding to the charges of other subscribers.

[0010]

According to the method of the present invention, in a message transmission system, during connection setup,
Fixed data such as the subscriber number, subscriber station identification code stored at the subscriber station is compared to the fixed data stored at the switch, evaluated, and additional variable data is present at the subscriber station and switch. , In transmitting the fixed data and the variable data together in achieving the connection to the exchange, comparing, evaluating and detecting the unauthorized use of the identification signal assigned to the subscriber station, the subscriber station Is used as variable data, each of the subscriber station and the exchange has a counter, and the counting positions of these counters are incremented by 1 for each successful connection.

According to the method of claim 1, unauthorized users can be illegally copied by illegally copying the identification signal generator or eavesdropping on the exchange of information via the message transmission system. Unauthorized use of the obtained identification signal can be detected. As stated in claim 1 fixed data such as subscriber numbers and identification codes are combined with variable data. Even if the stored fixed data is copied, the fraudulent user is still unable to make calls at the expense of other subscribers. The reason is that an unauthorized user does not know variable data. An unauthorized user cannot copy the stored fixed data and make a call at the expense of other subscribers of the message transmission system until he hears the variable data. However, since the variable data changes during the operation of the two subscriber stations, it is only by chance that the fraudulent use of service during the first call or first period is undetectable. Over the course of a long period of time, during other operations of the two subscriber stations, variable data that are not equal are set, which results in different comparison results in the exchange,
An unauthorized user cannot make an attempt to use the service without detecting unauthorized use of the identification signal. Another advantage of the method according to the invention is that the data volume of the fixed data can be reduced due to the variable data volume, so that the identification signal generator (fixed data storage), eg a magnetic card, can be of simple construction.

When the number of successful call setups of the subscriber station is used as the variable data according to claim 1, the comparison and evaluation process in the exchange can be easily simplified. The reason is that the encoded data, especially the counting positions can be compared using a logic circuit having a simple structure.

In most cases, manipulation of the identification signal is performed by eavesdropping on information exchanges over the message transmission channel. The method according to claim 3 uses an encryption device to obtain an encrypted counting position. Since the unauthorized user does not know the instantaneous counting position or the rule for encrypting this counting position, the security measure can be further improved.

In order to prevent the possibility that the encryption rule for encrypting (encoding) the counting position may be decrypted by repeated attempts, as described in claim 4 of the claims,
Additional fixed data is supplied to the encryption device and this is combined with the counting position supplied to the encryption device. This allows
Since different encryption rules are generated for different subscriber stations of a message transmission system, a great deal of effort is required to decrypt the encryption rules.

As described in claim 5 or claim 6, the subscriber station transmits only a part of the encoded counting position as variable data, and this part transmits a predetermined bit. It is obtained by selecting the position or by performing cross addition. If an unauthorized user eavesdrops on the exchange of information over the message transmission channel, the unauthorized user will only be able to know a part of the encoded counting position and not the entire counting position. In the case of this cross addition, the same cross addition is always associated with a large number of counting positions, and for example, the decimal cross addition 5 is added to the counting position 00.
5,122,221. Therefore, an unauthorized user can only guess the entire counting position, which is usually detected during the unauthorized user's first attempt.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENT The block circuit of FIG. 1 shows the circuit used in the method according to the invention in a subscriber station T and a switch Z of a message transmission system. The subscriber station T and the exchange Z respectively have control units STT and STZ, which control the set-up of the connection. If the subscriber station T wishes to use the services of the exchange Z, the exchange Z requests the subscriber station T to send its identification signal. In order to identify itself, the subscriber station T uses an identification signal generator K by means of a transceiver device SET.
G, for example, the identification code stored in the magnetic card is transmitted to the exchange Z via the message transmission channel L. The identification signal transmitted thereby has the subscriber number TNR and the first identification code K1 stored in the identification signal generator KG. In the exchange Z, the transmitted identification signal is received by the transmission / reception device SEZ, is supplied to the control device STZ, and the identification signal (subscriber number TNR is stored in the identification signal data file KD by the control device STZ. And the first identification code K1) for evaluation.

In the method according to the invention shown in FIG. 1, the subscriber station T and the exchange Z are provided with varying additional data.
In this example, the number of successful connections from the subscriber station T is used as variable data. The counting position ZS ^* of the counter ZZ provided at the subscriber station T is incremented, for example, by 1 for each successful connection. The counting position ZS ^* that can be taken out from the output terminals Q _{O to} Q _{n of the} counter ZZ is transmitted via the message transmission channel L by the transmission / reception device SET, received by the transmission / reception device SEZ in the exchange Z, and supplied to the control device STZ. The counting position of the counter ZZ1 for each successful connection of the subscriber station T is incremented by 1 by the control unit STZ. If the counting position increases by a number greater than 1 for example due to a linearly increasing difference and reaches a maximum value, it is necessary, for example for control purposes, to provide a counter and a storage for the last used difference. The exchange Z is provided with a plurality of counters ZZ1, ..., ZZM for M different subscriber stations.

According to the method described with reference to FIG. 1, the subscriber number TNR, the first identification code K1 and the counting position ZS ^* of the counter are controlled by the control unit STT at the subscriber station T during the setup process of the connection. It is transmitted to the exchange Z and compared with the subscriber number TNR and the first identification code K1 stored in the identification signal data file KD in the exchange and the counting position of the counter ZZ1.

If the subscriber number TNR, the first identification code K1 and the variable data, eg the counting positions, are equal to each other at the subscriber station and the exchange, the subscriber activates the services of the exchange Z.

If the counters ZZ and ZZ1 have different counting positions from each other, the exchange Z is assigned a second identification code K.
The subscriber station T is requested by the identification command to send 2. The exchange Z compares the received second identification code K2 with the identification code K2 stored in the identification signal data file KD,
If the two identification codes K2 do not match, the alarm device is triggered.

If the two identification codes match, the central control unit STZ sets the counter ZZ1 at the counting position of the counter ZZ of the subscriber station T. At the setting up of each subsequent successful connection, the two counting positions are incremented by one. The identification signal of the subscriber station T is stored in the exchange Z. Counters ZZ and ZZ1 during the setup process of the next connection
If the count positions of the two match, the identification number of the subscriber station T is excluded from storage. If all of the following comparisons do not match, the subscriber station T is blocked.

In the embodiment shown in FIG. 1, the counting position ZS ^* of the counter ZZ of the subscriber station T is supplied to the encryption device VE which produces the encrypted counting position VZS ^* . The exchange Z has a decryption device EE corresponding to the encryption device VE, and this decryption device EE also extracts the encrypted counting position VZS from the counting position ZS of the counter ZZ1. When the identification process includes a step of comparing the encrypted counting positions VZS ^* and VZS, the identification operation can be easily performed. A rogue user who does not know the encoding rules and the counting position ZS ^* of the counter ZZ can only accidentally transmit the correct variable data, so in general a rogue user will stop after a number of unsuccessful attempts. Let's do it.

In order to further improve the security measure, additional fixed data, more specifically a second identification code K2, which is also known to the exchange Z, is also supplied to the encryption device VE. The encryption device VE of the subscriber station T generates an encoded counting position VZS ^* from the combination of the second identification code K2 and the counting position ZS ^* supplied to it. By using the deciphering device EE in the exchange Z, the deciphering device EE performs the same deciphering process as described above for the counting position ZS of the counter ZZ1. The results obtained thereby are compared in the same way as described above.

A further improvement of the security measure can be achieved by transmitting only a part TZS ^* of the counting position ZS ^* as variable data by the subscriber station T during the setup process of the connection. For this purpose, the subscriber station T is provided with a selection circuit AST, for example for selecting a predetermined bit position from the encrypted counting position VZS ^* supplied to it. In another embodiment, the encrypted counting position VZS ^* supplied by the selection circuit AST ^.
Is cross-added. The switching circuit Z is also provided with a selection circuit ASZ so that a part TZS is selected from the counting position ZS corresponding to the selection circuit AST in the subscriber station T and comparison is performed. Alternatively, the encrypted counting position VZ is selected by the selection circuit ASZ.
Cross-add S.

An unauthorized user may access the message transmission channel L
If you are wiretapping the exchange of information through the, this shall only be able to obtain only a portion of the encrypted counted position VZS ^*, to obtain a complete encryption counting position VZS ^* Can not. In the case of transmitting only a part of the counting positions during the cross addition process or by selecting a predetermined bit part, a plurality of counting positions ZS ^* are possible, and thus an unauthorized user can obtain a complete counting position ZS ^*. You can only try to guess. In general, a fraudulent user's first attempt to infer variable data has already been detected and appropriate measures can be taken.

The method according to the invention is also useful in banking and credit card operations where fixed and variable data are stored on magnetic cards. The variable data in this case is the current transaction status of the subscriber or one secret word of a set of secret words.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit used in an embodiment of a method of the present invention.

[Explanation of symbols]

 T subscriber station Z exchange STT, STZ control device KG identification signal generator SET, SEZ transmission / reception device L message transmission channel KD identification signal data file ZZ, ZZ1, ZZM counter VE encryption device EE decryption device AST, ASZ selection circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location 8732-5K H04L 11/26

Claims (6)

[Claims] 1. In a message transmission system, during set up of a connection, fixed data such as a subscriber number, an identification code of the subscriber station, stored in the subscriber station is compared with fixed data stored in the exchange. And evaluate
Additional variable data for subscriber stations (T) and exchanges (Z)
Existing, and in connection with the exchange (Z), fixed data and variable data are transmitted together, compared, evaluated and the unauthorized use of the identification signal assigned to the subscriber station is detected. In this case, the number of successful connections of the subscriber station (T) is used as variable data, each of the subscriber station (T) and the exchange (Z) has a counter (ZZ, ZZ1), and these counters (ZZ, ZZ,
A method for detecting unauthorized use of an identification signal, characterized in that the counting position of ZZ1) is increased by 1 for each successful connection. 2. The identification signal unauthorized use detection method according to claim 1, wherein fixed data and variable data are stored in a magnetic card. 3. The method for detecting unauthorized use of an identification signal according to claim 1, wherein the counting position (ZS ^* ) of the counter (ZZ) of the subscriber station (T) is supplied to the encryption device (VE). A method for detecting unauthorized use of an identification signal, wherein an encrypted counting position (VZS ^* ) is generated from the counting position (ZS ^* ) by an encryption device. 4. The method for detecting unauthorized use of an identification signal according to claim 3, wherein additional fixed data (K2), which is also known to the exchange (Z), is supplied to the encryption device (VE). A method for detecting unauthorized use of an identification signal, characterized in that an encrypted counting position (VZS ^* ) is generated from the additional fixed data by an encryption device (VE). 5. The method for detecting unauthorized use of an identification signal according to claim 1, wherein a part (TZS ^* ) of the counting position (ZS ^* ) is set up during connection setup ^.
Transmitted only as variable data by the subscriber station (T),
A method for detecting unauthorized use of an identification signal, characterized in that a selection circuit (AST) selects a predetermined bit position from the encrypted counting position (VZS ^* ) supplied thereto. 6. The knowledge according to any one of claims 1 to 4.
In the separate signal unauthorized use detection method, the connection
Up counting position (ZS^*) Part (TZS ^*) Only
It is transmitted as variable data by the subscriber station (T) and selected
On the road (AST) the counting position (VZ
S^*) To form a cross addition value
Another signal unauthorized use detection method.