WO1996036162A1

WO1996036162A1 - Subscriptionless telephone, control module therefor and secure telephone equipment including the telephone and security module

Info

Publication number: WO1996036162A1
Application number: PCT/FR1996/000710
Authority: WO
Inventors: Fabienne Blanchet-Newton
Original assignee: Schlumberger Industries S.A.
Priority date: 1995-05-12
Filing date: 1996-05-10
Publication date: 1996-11-14
Also published as: FR2734115A1; RU2154349C2; FR2734115B1

Abstract

A telephone equipment for transmitting information on a telephone line (10), comprising a telephone (14) of a type not requiring subscription and connectable to the telephone line, and a control module (16) mounted in parallel on said telephone line and associated with the telephone. The telephone transmits to the module, at predetermined times, predetermined information (K'i) obtained by means of an algorithm and a random number, and the number of the called telephone. The module produces information (Ki) on the basis of the same algorithm and the same random number, and compares it to the information (K'i). If there is no match, the module (16) activates the blocking circuit (18).

Description

TELEPHONE SET WITHOUT SUBSCRIPTION, MODULE

ASSOCIATED CONTROL AND TELEPHONE INSTALLATION

SECURE INCLUDING SAID TELEPHONE AND

SAID SECURITY MODULE

The present invention relates to a telephone set of the type without subscription, intended to be connected to a telephone line of a telephone installation for the transmission of information, as well as a control module intended to be associated with said telephone set.

It also relates to a telephone installation for the transmission of information on a telephone line comprising a telephone station of the type without subscription and connectable to said telephone line, and a control module mounted in parallel on said telephone line and associated with said telephone station.

More specifically, the present invention relates to such an installation applied to the case of a telephone set preferably with prepayment by card or other, that is to say in the case of a telephone set installed in a private place or possibly public and in which the payment of the telephone charge is done mainly using a memory card or the like without having to pay a subscription for this telephone set. The invention is particularly advantageous in the case of immediate payment by the user. Indeed, it is understood that in this case it is necessary to avoid that the telephone set integrating an immediate payment procedure cannot be replaced by a normal set in which case the telephone calls could be obtained free of charge by a fraudster since there is no subscription. However, the invention is also applicable in the case where telephone charging is done by counting charging pulses sent at a telephone exchange. Similarly, the invention also applies to the case where the telephone set has its own tax table for telephone communications, that is to say the case where there are no charging pulses emitted on the line.

More generally, the invention applies to each time it is necessary to establish an authentication between a telephone set and an associated module mounted on a hardware transmission line or not before possibly interrupting the exchange of information in order to avoid any attempt at fraud.

To solve this problem, the following solution has been proposed: during the initial phase of establishing the telephone communication, coded quantities are exchanged between the transmitter and the receiver making it possible to control access to the communication. Such a system only partially solves the problem. It has also been proposed to encode the information to be transmitted at the level of the transmitter and a symmetrical decoding at the level of the receiver. However, since the transmission of information takes the form of analog frequency signals, the coding and decoding operations are relatively complex.

In European patent No. 0 335 768 in the name of the applicant, it has been proposed to solve this problem by mounting on the telephone line a control module associated with each telephone set to be secured. The telephone set has a particular structure and circuits which allow the exchange between the control module and the telephone set of authentication information which is compared to verify that the telephone set is authorized to be used. However, if the solution proposed in this European patent is effective, it requires the use of telephone sets of a specific type and relatively complex control modules which must be connected on the line at all times. In addition, it appears that certain types of fraud can still be implemented.

An object of the present invention is to provide a telephone set, a control module and an installation for transmitting telephone information which provide even better protection against fraud and which can be implemented with standard type telephone sets. through the introduction into these stations of an additional module of structure as simple as possible, and by mounting of a control module on the line on demand.

To achieve this object, according to the invention, the telephone set of the non-subscription type, intended to be connected to a telephone line of a telephone installation for the transmission of information, is characterized in that said telephone set comprises:

- means for transmitting the number of a called telephone set,

means for implementing a first predetermined algorithm for calculating initial information from the number called and from a random number and for developing successive authentication information from the initial information,

- Means for transmitting authentication information on said telephone line at predetermined times.

The control module intended to be associated with the telephone set according to the invention, is characterized in that said module is mounted in parallel on said telephone line and comprises:

- Means for detecting on said telephone line the number called and a signal for detecting the start of use of the telephone set.

means for developing said random number and transmitting it over said telephone line,

means for implementing a second predetermined algorithm corresponding to the first for calculating an initial value from said called number and said random number and for developing successive authentication information,

means for comparing at said predetermined times the initial information received with the calculated initial information and the successive information authentication received with successive authentication information developed, - means for inhibiting said telephone line based on the results of said comparisons if the authentication information received does not correspond to the calculated authentication information. Finally, the telephone installation for the transmission of information over a telephone line comprising a telephone station of the non-subscription type and connectable to said telephone line, and a control module mounted in parallel on said telephone line and associated with said telephone station, characterized in that said telephone set includes

. means for transmitting the number of the called telephone set,. means for implementing a first predetermined algorithm for calculating initial information from the called number and from a random number and for developing successive authentication information from the initial information, and. means for transmitting authentication information on said telephone line at predetermined times, and in that said control module comprises: means for detecting on said telephone line the number called and a signal for detecting the start of use of the telephone set,. means for developing said random number and transmitting it over said telephone line,

. means for implementing a predetermined algorithm corresponding to the first one for calculating an initial value from said called number and said random number and for developing successive authentication information,

. means for comparing at said predetermined times the initial information received with the information initial calculated and the successive authentication information received to the successive authentication information prepared; and

. means for inhibiting said telephone line as a function of the results of said comparisons if the authentication information received does not correspond to the calculated authentication information.

It is understood that such an installation makes it possible to obtain a very high degree of security since not only the successive authentication information depends on a random number but that, moreover, it depends on the number of the telephone station called. It is also understood that this installation is relatively simple and that at the level of the telephone set to secure the modifications to be made compared to the standard telephone circuit of the set are limited. In addition, it is understood that the connection to the telephone line of the control module with its inhibition means is very simple.

Other characteristics and advantages of the present invention will appear better on reading the following description of several embodiments of the invention given by way of nonlimiting examples. The description refers to the appended figures in which:

- Figure 1 is a simplified view showing the mounting of a telephone set and a control module according to the invention;

- Figure 2 shows schematically the circuits of the telephone set to be secured;

- Figure 3 shows the circuits of the control module in schematic form; and - Figure 4 shows a possible form of development of authentication information.

Referring first to Figure 1, we will describe the entire installation applied to a telephone set of the type without subscription. In this figure, there is shown the telephone line 10 connected to a telephone exchange. telephone without subscription 14 is connected to line 10. According to the invention, the telephone set 14 is associated with a control module 16 which is also mounted on line 10 and which is associated with a controlled switch or inhibition circuit 18 by the control module 16. The telephone set 14 comprises, in addition to the standard telephone circuits 20 and, preferably, the prepayment means 22 which may be with memory card or with coins, specific circuits constituting a particular module 24 which must be mounted on the telephone set 14 to make it compatible with the control module 16. As already indicated, the principle of the invention is to exchange periodically between the telephone set 14 and the associated control module 16 authentication information which is linked in particular to the number of the telephone set called. Referring now to FIG. 2, we will describe in more detail the circuits of the specific module which must be introduced into the telephone set 14 to make it compatible with the control module 16.

These circuits include a microprocessor or microcontroller 30 associated in particular with a specific program memory 32 which may be of the PROM type. The microprocessor 30 can advantageously control the standard telephone circuits 34 as well as the prepayment control circuits 36. The prepayment can be carried out by electronic memory card via the reader 38 or by means of coins via the '' an appropriate coin acceptor. The circuits also include a frequency signal generator 40 controlled by the microprocessor 30 as well as a frequency signal decoder 42 whose digital output is connected to the microprocessor 30. Finally an adaptation circuit 44 makes it possible to connect to the telephone line 10 all of the circuits of the telephone set just described.

As will be explained later, the frequency signal generator 40 is used to format the various authentication information in the form of frequency. In the appended figure 4, a particular type of frequency signals has been shown which can be used for the preparation of authentication information. The particular form of this signal depends on the chosen mode of production thereof. If the mode of FIG. 4 is used, the coding circuit which receives the authentication value controls the frequency generator 40 so that the latter delivers a signal of frequency f ₀ during the synchronization period of duration T then according to the value of K _Q , for each period T, it controls or does not control the development of the signal of frequency f ₀ according to the binary value of the period T considered. This period is for example equal to 20 ms. The frequency generator 40 therefore delivers only the frequency f ₀ . This frequency is higher than that of the voice message and preferably equal to 12 or 16 kHz. Referring now to FIG. 3, the main circuits of the control module 16 will be described. It essentially comprises a microprocessor or microcontroller 50 associated with a specific program memory 51. The microprocessor 50 controls a generator of frequency signals 52 of the same kind as the generator 40 of the telephone set and receives information from an analog signal decoder 54. The inputs and outputs respectively of the signal generator 52 and the decoder 54 are connected to the telephone line 10 via an adapter circuit 56. In addition, the microprocessor 50 is connected by its output 50a to a control circuit 58 which is itself directly connected to the muting switch 18 mounted on the telephone line 10. Finally the module control comprises a circuit 59 for detecting the off-hook of the telephone set which is connected to the microprocessor 50. The operation of the inst llation is as follows. When the control module 16 detects the off-hook of the handset of the station on line 10 thanks to the circuit 59, the control module is activated. Upon detection, the control module 16 transmits on the line, via the generator 52, a random number a which is preferably produced by the microprocessor 50 by setting work of specific software stored in memory 51. This random number transmitted preferably in the form of frequency signals is also detected by the telephone set 14 by means of the decoder 42. The microprocessor 30 of the telephone set then puts in implements an algorithm, the parameters of which are stored in memory 32 to develop initial authentication information K ' ₀ . This initial information depends on both the random number received and the number of the extension called. The microprocessor 30 then controls the emission by the generator 40 of a frequency signal representative of the initial authentication information K ′ _Q.

This emission is detected by the decoder 54 of the control module and the authentication information transmitted in digital form to the microprocessor 50. The microprocessor 50, by implementing a predetermined algorithm, works out from the random number a and the number of the station called initial authentication information K _Q. This initial information K ₀ developed is compared to the initial information K ' _D received from the telephone set. If there is compatibility between K ₀ and K ' _Q , this means that the telephone set is authorized to be used. Either the two algorithms implemented by the telephone set and the control module are identical and in this case the authentication information produced by the set and the authentication information produced by the control module must be identical for the set be allowed. Either the two algorithms are different but correlated with each other and, consequently, the authentication information K ₀ and K ' ₀ will always be different even if the telephone set is authorized. Of course it is the comparison program which will detect the correlation between K ₀ and K ' _D.

After this initial authentication of the telephone set 14, the telephone set transmits at predetermined times successive authentication information K'i. Preferably, the information K'i is produced using the algorithm from l previous authentication information K'i_ι. She can also directly depend on the number called and the random number a. Preferably, the coding algorithm is a DES type algorithm. This authentication information is sent on line 10 and detected by the control module 16. The microprocessor of the control module then prepares its authentication information Kj and compares it with the information K '. If the information matches, the telephone transmission continues until the next authentication information is issued. Otherwise, the control module controls the inhibition circuit 18 which causes the interruption of the telephone link.

The predetermined times of transmission by the telephone set of authentication information K'i can be defined in different ways depending on the type of installation envisaged.

In a first embodiment, the telephone set can include a time base which transmits a signal whose period corresponds to the time interval between the preparation and the transmission of two successive authentication information items K'i . This mode of implementation is therefore completely independent of the management of payment for telephone communications. It therefore applies even if the use of the telephone set is free, the control of the telephone set being motivated by other reasons than payment.

In the case where the telephone set has its own charging table, the predetermined times for the transmission of authentication information can be determined by the transmission of the direct debit charge by the table itself. The authentication information detected by the control module triggers by the latter the development of its own authentication information. When the telephone set does not have an internal charging or billing table, it is the reception of the charging pulses sent by the telephone exchange which determines the predetermined times leading to the preparation and the transmission by the telephone set of new authentication information.

Preferably, the control of the immediate payment of the communication, when such a payment exists, is entirely managed by the telephone set itself as is the case in standard telephone sets, the control module not intervening in this procedure.

Claims

1. Telephone station (14) of the type without subscription, intended to be connected to a telephone line of a telephone installation (11) for the transmission of information, characterized in that said telephone station (14) comprises:

- means for transmitting the number of a called telephone set,

- Means (30) for implementing a first predetermined algorithm for calculating initial information (K ' ₀ ) from the called number and a random number and for developing successive authentication information (K'i) to from the initial information (K ' ₀ ),

- Means (40, 44) for transmitting authentication information (K'j) on said telephone line at predetermined times.

2. Telephone set according to claim 1, characterized in that it comprises means for transmitting time pulses at a predetermined period, said pulses defining said predetermined instants.

3. Telephone set according to claim 2, characterized in that it comprises an internal charging table, and in that said time pulses are charging pulses.

4. Telephone set according to claim 1, characterized in that said predetermined times are defined by charging pulses emitted by the telephone exchange of the installation (11).

5. Telephone set according to any one of claims 1 to 4, characterized in that it comprises means (36, 38) for prepayment of taxes and means for transmitting an acknowledgment signal each time a tax is acquitted.

6. Control module (16) intended to be associated with the telephone set (14) according to one of claims 1 to 4, characterized in that said module (16) is mounted in parallel on said telephone line and comprises: means for detecting on said telephone line the number called and a signal for detecting the start of use of the telephone set (14). means (50) for developing said random number and transmitting it over said telephone line, means (50) for implementing a second predetermined algorithm corresponding to the first to calculate an initial value (K _Q ) from said called number and said random number and to develop successive authentication information (Ki), means (50) for comparing at said predetermined times the initial information (K ' ₀ ) received with the calculated initial information (K _Q ) and the successive information authentication (K'i) received to the successive authentication information (Ki) developed, means (58) for inhibiting said telephone line according to the results of said comparisons if the authentication information (Ki) received does not correspond to the calculated authentication information (Ki).

7. Control module according to claim 6, characterized in that it comprises means for developing new authentication information (Ki) on receipt of the corresponding identification information sent by said telephone set (14).

8. Control module according to one of claims 6 or 7, intended to be associated with a telephone set according to claim 5, characterized in that said module comprises means for inhibiting the transmission of information in the absence of signal of acquittal.

9. Telephone installation for the transmission of information over a telephone line (10) comprising a telephone set (14) of the type without subscription and connectable to said telephone line, and a control module (16) mounted in parallel on said telephone line and associated with said telephone set, characterized in that said telephone set (14) comprises:

- means for transmitting the number of a called telephone set, - means (30) for implementing a first predetermined algorithm for calculating initial information (K ′ _Q ) from the number called and from a random number, and to develop successive authentication information (K'i) from the initial information (K ' ₀ ), - means (40, 44) for transmitting authentication information on said telephone line at predetermined times ( K'i),

- And in that said control module (16) comprises:

means for detecting on said telephone line the number called and a signal for detecting the start of use of the telephone set,

- means (50) for developing said random number and transmitting it on said telephone line,

means (50) for implementing a second predetermined algorithm corresponding to the first one for calculating an initial value (K ₀ ) from said called number and said random number and for developing successive authentication information (Ki),

- Means (50) for comparing at said predetermined times the initial information (K ' _D ) received with the calculated initial information (K ₀ ) and the successive authentication information (K'i) received with the successive authentication information (Ki) developed,

- Means (58) for inhibiting said telephone line as a function of the results of said comparisons if the authentication information (Ki) received does not correspond to the authentication information (Ki) calculated.

10. Installation according to claim 9, characterized in that the first and second algorithms are identical.

11. Installation according to one of claims 9 or 10, characterized in that each authentication information comprises a succession of binary values, a first binary state consisting in the absence of a signal, the other binary state consisting in the presence of a frequency signal.