GB2351171A

GB2351171A - Access control and/or anti-theft system

Info

Publication number: GB2351171A
Application number: GB0013026A
Authority: GB
Inventors: Christian Vorlaufer
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1999-06-15
Filing date: 2000-05-31
Publication date: 2000-12-20
Anticipated expiration: 2020-05-31
Also published as: GB0013026D0; DE19927253A1; GB2351171B; DE19927253C2; FR2795121B1; FR2795121A1

Abstract

In an access control and/or anti-theft system using a portable transponder (1), eg. for an automobile, as a security measure against an unauthorised remote query, the transponder (1) is equipped with a movement sensor (2) and sends back its reply code signal upon receiving a query code signal only if the transponder was moved during a certain time interval prior to the authorisation check.

Description

2351171

Description

Control system, more particularly automobile access control system or antitheft system and methods designed for this purpose The invention relates to a control system, preferably an automobile control system with a control device mounted on the automobile, more particularly for access control and/or anti-theft function, which performs an authorisation check using an identity transmitting device (referred to below as transponder) issued to authorised users before carrying out the function which is to be controlled. In general, in the authorisation check a query code signal is sent to the transponder which it answers with an answer signal which is checked for correctness by the control system on the vehicle. The range of the transmitting signal is ordinarily relatively small so that data communications can be carried out only in the immediate vicinity of the automobile. Theoretically, however, an unauthorised remote query (also designated as full duplex attack) is conceivable in which the query code signal is recorded without authorisation and analysed.

Such a control system according to the pre -characterising clause of Claim 1 is known from DE 44 09 167 Cl in which the portable transponder has a distance detection means and in which the communication is immediately terminated in the event the distance between the control device and the transponder is too great.

From DE 196 04 206 AI a control system according to the precharacterising clause of Claim 1 is known in which a user inputs the identification code (PIN) via a key pad of the transponder.

From GB 2 279 479 A is known a permanently built-in alarm system for a vehicle in which a compass is used as a movement sensor.

2 From DE 94 14 476 Ul is known a device for monitoring a parked vehicle which is placed in the parked vehicle and among other things has an inclination sensor.

The object of the invention is to still further reduce the possibility of an unauthorised query of this kind.

Claims

This object is realised with the features mentioned in Claim 1.

Furthermore a method for controlling the authorisation check process is created with the invention in accordance with Claim 7.

Advantageous embodiments of the invention are given in the subclaims.

According to the invention, as an additional criterion in the authorisation check an examination is made as to whether the transponder was moved within a short time interval such as 10 to 3 0 seconds prior to the authorisation check. In so doing, the invention makes use of the fact that an authorised user as a rule will have walked to the vehicle immediately prior to performing the authorisation check or will have seated himself immediately beforehand on the seat of the automobile so that the transponder carried by the user was exposed to strong movements, accelerations and shocks. If in contrast an unauthorised remote query is attempted, the likelihood is quite high that the transponder immediately prior to the authorisation query will not have been moved since the authorised user, by way of example, will have already been seated in the office chair for an extended period of time or will have laid aside the bag containing the transponder or the corresponding article of clothing such as a coat. Only if this additional criterion of an immediately preceding movement of the transponder is fulfilled will the control device release the emission of the correct reply code signal. This additional security criterion can be easily 3 realised since the transponder merely must be equipped with a supplemental movement sensor and a timer or another time-determining circuit. No interventions in the components of the control system on the vehicle are necessary. Thus even existing systems can very easily be retrofitted through exchange of the transponder.

The movement sensor can be designed as a mechanical movement switch or as a mechanically oscillating formation; it influences a circuit with an output signal which changes time-dependently, continuously, in increments, or in jumps.

The time-determining circuit can be variously configured such as an RC element with a large discharge time constant or as a time counter.

The invention can be used with control systems of any type, thus also for control of functions other than an access control and/or an anti-theft function, for example for checking the authorisation for use of a lock box, an automatic teller machine, or the like.

The invention will be described below with the aid of embodiment examples with reference to the drawings.

Figure 1 shows a transponder for a control system, Figure 2 shows an embodiment form of a circuit for detecting movement and time specification, Figure 3 shows a modified embodiment of a movement sensor with attached control circuit, and Figure 4 shows an embodiment with clock counter.

4 In Figure I the construction of an identity signaller in the form of a transponder I is depicted which is configured here as a chip card, but which can have any other desired form such as the form of a key. Transponder I contains a movement sensor 2 and a time sensor 3 connected thereto which in turn is connected to a control or evaluating means 4 (for example a microprocessor or microcontroller). Control and evaluating circuit 4 is equipped with a transmission antenna 5 for emitting signals to a not-depicted control device which serves by way of example as an access control system or an anti-theft system for an automobile and with a receiving circuit 6 for receiving query code signals applied to the control device. The components on the vehicle side can be of known construction and by way of example can be designed such that upon activation of a door handle or of an ignition button, a query code signal is emitted by the control device through its transmitting antenna which transponder I receives through its receiving circuit 6 and feeds to the control and evaluation circuit 4. Circuit 4 checks whether the query code signal is directed to it and if this is the case, transmits a reply code signal through transmitting antenna 5 back to the control device which is checked in the control device for correctness, for example through comparison with an expected target code signal. If the received reply code signal is correct, the control device controls the associated function, for example unlocking the doors.

Movement sensor 2 can be constructed as an acceleration sensor with mechanically moved element, for example based on semiconductors or in other manner, which responds to the movements of the jolts, vibrations, and accelerations occurring upon movements of the person carrying the transponder and generates an analogue output signal or one which jumps between two or more levels depending on the acceleration variable at a given moment. Since the movement sensor is not provided here primarily for absolute measurement of the intensity of movement or acceleration but rather is to distinguish between rest state and relatively strong movements, a simply constructed sensor which can only distinguish between the two conditions "acceleration below a certain threshold value" and "acceleration above the threshold value" and by way of example generates a digital signal with the level "zero" or "one". Since walking movements of the carrier ordinarily are linked with accelerations in all three space coordinate directions, it is sufficient to, use an acceleration sensor sensitive in only one direction. Naturally, however, acceleration sensors can also be used which are sensitive in two or in all three space coordinate directions.

Time-determination circuit 3 is activated by movement sensor 2 each time, or is fed with a change of the output signal sensor 2, when it detects a movement above the specified threshold value. Time-determination circuit 3 is set to a fixed time interval such as 5 to 30 seconds, preferably 5 to 10 seconds, and during this time period generates after each detennination of a movement by movement sensor 2 an output signal injected into control and evaluation circuit 4, for example with high logical level. At high output signal level, control and evaluation circuit 4 thus receives the information that the last movement detected by movement sensor 2 is a shorter distance in the past than the predetermined time interval. In this case, control and evaluation circuit 4 will then respond to a received query code signal, generating a reply code signal 5. Otherwise, i.e. in the event of movement of transponder I which lies farther in the past than the predeten-nined time interval and thus an output signal of timedetermination circuit 3 which is again decreasing, control and evaluation circuit 4 suppresses the generation of the reply code, so that the function controlled by the control device of the vehicle is not performed.

6 In Figures 2 to 4, various detailed embodiments of movement sensor 2 and of ti me- determining circuit 3 are depicted. Figure 2 shows a circuit in which movement sensor is configured as a mechanical movement switch 7, 7' which presses switch 7 into the closed position upon the exceeding of a certain acceleration value. Component 7' can be a weight which as a result of inertia cannot follow movements quickly and accordingly press switch 7 into closed position. The time-determining circuit contains a capacitor 8, one layer of which is connected to ground and the other terminal of which is connected with closed switch 7 to supply voltage Vs. Connected parallel with capacitor 8 is a high resistance discharge resistor 9 through which capacitor 8, which with closed switch 7 is charging, is discharged again with high time constant. The capacitor voltage is applied to the input of a voltage comparator 10 the other comparison input of which is fed with reference voltageVREF. The output of voltage comparator 10 is connected with an input of control circuit 4. During movements of the transponder, capacitor 8 is charged by the supply voltage through switch 7 which repeatedly closes with short time constant and discharges with lack of movement and thus with switch 7 being open for a relatively long period according to an e-function. The discharge time constant and comparison voltage VREFare set such that capacitor voltage 8 has dropped upon expiration of the predetermined time interval to reference voltageVREF SO that the output signal of voltage comparator 10 is switched over and as a result the expiration of the predetermined time interval without movement is signalled to control circuit 10.

Used as sensor for recognition of movement in a further embodiment is a mechanical resonator with slight damping which continues to oscillate for a certain period of time after the occurrence of a movement. The amplitude of the oscillation is then the basis for the decision. In Figure 3, such an 7 embodiment is schematically shown. Acceleration sensor I I comprises a housing 12 in the interior hollow space of which a mass body 13 is mounted symmetrically between two springs 14 so that following excitation through an acceleration it continues to oscillate for a relatively long time with decreasing amplitude. A switch 15, for example a microswitch, is arranged on the housing wall to the side of mass body 13 which in the event of oscillating mass body with an oscillation amplitude above a certain value is activated periodically by mass body 13. Control circuit 4 periodically queries the switch condition of switch 15 and from its periodic activation recognises the presence of oscillations of mass body 13, i.e., the fact that movement sensor 11 was exposed to sufficiently strong accelerations at less than the predetermined time interval. If control circuit 4 in contrast determines that switch 15 is not (or is no longer) activated, this represents an indication of oscillations which have already decayed, i.e. long lack of movement of transponder I with the result that the control circuit no longer answers the query code signal.

Figure 4 shows an embodiment with a time signaller in the form of a counter 16 which counts a clock signal occurring at a fixed frequency and upon reaching a certain count corresponding to the predetermined length of time emits an output signal to control circuit 4. The reset input of the counter is connected through the movement sensor configured in the form of a mechanical movement switch or acceleration circuit to high voltage Vs so that counter 16 is reset upon each response of the movement sensor and thus begins to count again from the beginning. Only when the movement sensor has not moved at least during the predetermined period of time and thus no reset signal is applied to the reset terminal does counter 16 count to the predetermined count level and then emits a constant output signal to control circuit 4. As soon as movements are subsequently detected again, counter 16 is reset and thus a 8 signal is given to the control circuit that the last movement lay less far in the past than the predetermined time interval and thus incoming query code signals can be answered with the reply code signal. Counter 16 can be configured as a software counter and thus be integrated as a part of control circuit 4 which ensures a very compact, energy saving, and reliably functioning construction.

9 Claims 1. Control system, in particular automobile control system, with a control device, in particular an access control and/or anti-theft control device, and a portable transponder (1) serving as an identity signaller which has a control device (4) and communicates wirelessly with the control device for authorisation checking, characterised in that the transponder (1) is equipped with a movement sensor (2, 7, V, 11, 17), and that the control device (4) in an authorisation check examines whether the transponder (1) was moved within a certain time interval before the authorisation check, and releases the transmission of the identification code only upon fulfilment of this criterion.
2. Control system according to Claim 1, characterised by a time signaller circuit (3; 8, 9, 10; 16) which generates an output signal which changes based on time and serves for determining the passage of a predetermined time interval.
3. Control system according to Claim 1 or 2, characterised in that the movement sensor is a mechanical movement switch (7, T) which is inserted in the charging path of a capacitor (8) which is provided with a discharge circuit (9) whereby the output voltage of the capacitor (8) represents a measure of the length of time since the last movement of the transponder (1) which led to a closing of the mechanical movement switch (7, T).
4. Control system according to Claim 1 or 2, characterised in that the movement sensor (11) is a mechanical resonator with an elastically suspended mass body (13) which continues to oscillate in a damped manner following stimulation.
5. Control system according to Claim 1 or 2, characterised by a counter (16) which counts a clock signal and the reset input voltage of which is controlled by a movement sensor (17) such that the counter upon expiration of the predetermined time interval without reception of a signal at the reset input has counted to a certain count level and applies a corresponding signal to the control circuit (4).
6. Control system according to Claim 5, characterised in that the counter is configured as a software counter and is a part of the control circuit (4).
7. Method for carrying out an authorisation test between a control device and a portable transponder (1) which communicates with the control device wirelessly in which in carrying out an authorisation check it is also checked whether the transponder (1) was moved during a predetermined time interval prior to performance of the authorisation check or not, and the transponder sends its identity code only if during the predetermined time interval a transponder movement in excess of a certain threshold value was detected.