ITMI20011109A1 - PROCEDURE DEVICE TO MANAGE AN AUTHORIZATION SYSTEM - Google Patents

Description

Description

State of the art

The invention starts from a device and a method for managing an authorization system in accordance with the genre of the independent claims. An access system comprising a portable electronic key with a transmitter is already known from WO 00/05696. A receiver is preferably arranged in a motor vehicle. Transmitter and receiver are designed to communicate with each other to exchange authentication data. The transmitter transmits a signal which the receiver converts into spectral signals. The access system guarantees access only when the spectral data coincides with a characteristic spectral signature for the transmitter. The spectral signature is a suitable quantity for detecting manipulation attempts caused by an additional amplifying station. However, if a manipulator is able to forward the signal sent by the electronic key to the receiver without variations in frequency distortions, even those who are not authorized can access the vehicle.

The invention has the task of further increasing the safety against undue attempts at manipulation. This problem is solved by the features of the independent claims.

Advantages of the invention

The authorization system according to the invention comprises an electronic key with a transmitter. A base station with a handset is provided in a secure location. The transmitter sends to the receiver a signal which converter means, contained in the base station, convert into at least one spectral information. The base station contains comparator means which compare the spectral information with an attested spectral information and, in the event of a match, produce an authorization signal. According to the invention, the electronic key comprises means of variation, which modify the spectral information contained in the signal to be transmitted with respect to a spectral information transmitted in a previous transmission operation. The signal sent by the electronic key to the receiver, preferably arranged in a motor vehicle, can therefore be selectively influenced during each transmission process. The expected spectral information is adapted accordingly to the influence of the spectral information of the signal. In this way, the information procuring an authorization is permanently modified, so that it is impossible for an unauthorized person, listening to the communication, to access the vehicle.

With the spectral information obtained from the transmitted signal, the amplitudes respectively the amplitude ratios for certain frequencies or the intensity of the signals within one or more frequency bands are used. A frequency-related spectral information is especially suitable since by using an additional amplifier station the resulting nonlinearities can be readily detected to recognize manipulation attempts. Preferably a signal consisting of two tones / frequencies is provided as the signal, the spectral information of which is varied by a variation of the respective (transmission) amplitudes for certain frequencies. With a targeted variation of the amplitude with each transmission operation, the received signal strength in a frequency band varies continuously and thus varies the spectral information of the transmitted signal. Especially the ratio of the signal intensity of a frequency band associated with the first frequency, with reference to the signal intensity of a second frequency band associated with the second frequency, can preferably be used as spectral information, since this eliminates the influence of the distance of the key from the base station on the signal.

In a suitable embodiment, the variation means comprise a receiver which receives a transmitted stimulus. The means of variation influence the spectral signature to be transmitted of the signal depending on the stimulus. The stimulus is sent by the base station and at the same time used to produce, after an algorithm, stored identically in the key, the expected spectral information. In this way it is possible to perform a compensation of the currently expected spectral information in a simple way.

In an appropriate execution, a microcontroller is provided in the key, which from the stimulus of the base station determines a response for authentication.

This response is returned to the base station receiver which compares the incoming response signal with an expected response signal. Only in the case of a correspondence is access and / or authorization to drive guaranteed. With this additional authentication process it is possible to further increase security, since in addition to the correspondence of the spectral information, a concrete response must also necessarily reach the base station. Furthermore, only information will have to be sent, and precisely the stimulus, from which the electronic key determines two characteristic quantities: firstly the influence of the spectral information of the signal, secondly the determination of the response signal necessary for the access. A random number is preferably used as a stimulus. Consequently, it is possible to further increase the safety against listening.

A further advantageous development provides that in order to influence the spectral information only a part, preferably the beginning, of the information contained in the stimulus is treated. The authorization procedure can be accelerated in this way, since it will not necessarily have to wait for the end of the stimulus data transmission to affect the spectral information of the signal. In this way the signal can be quickly returned and processed by the base station to check the authorization.

Further suitable developments result from the further dependent claims and from the description.

Drawings

An embodiment of the invention is shown in the drawing and is described in more detail below. Figure 1 shows a block diagram and Figure 2 shows characteristic signal patterns of the device according to the invention.

Description of the example of realization

The authorization system consists of an electronic key 4 and a base station 8 arranged in correspondence with a place to be protected. As regards this place to be protected, it is, for example, the passenger compartment of a motor vehicle. The base station 8 comprises a receiver 10 which forwards an incoming signal 14 via the antenna 12, a receiver apparatus 36 and an analog-digital converter 38 to a microcontroller 40 of the base station 8. The microcontroller 40 controls a local oscillator 42, which correspondingly affects the receiver apparatus 36. The microcontroller 40 exchanges data with a transmitter / receiver 39, which is arranged in the base station 8 and emits a stimulus 60 and subsequently receives a response 62. The microcontroller 40 compares the information spectral incoming with the expected spectral information. In the case of a correspondence, the microcontroller 40 produces an authorization signal 41, by means of which, for example, a closing system, not indicated in more detail, in the sense of an opening or immobilizer, is eliminated in order to obtain the authorization to run.

The electronic key 4 comprises a transmitter 6, which is formed by a first (radio frequency) oscillator 30 producing a first sound f2 and by a second (radio frequency) oscillator 32 producing a second sound f2. The output signal of the second oscillator 32 serves an attenuator 54 as an input signal. The output signal of the attenuator 54 like that of the first oscillator 30 is fed to an antenna switch 34. The output signal of the antenna switch 34 is sent by an antenna 7 as a signal 14. The attenuator 54 is controlled by a microcontroller 50 of the key 4. The microcontroller 50 exchanges data with a transmitter / receiver 52 receiving the stimulus 60. The microcontroller 50 calculates from the stimulus 60 the response 62 which is subsequently sent to the base station 8.

The base station 8 is placed in a protected place, such as in the passenger compartment of a vehicle and controls access to the protected place. When the key 4 is approached within a defined area of the antenna 12 of the receiver 10, the base station 8 excites the key 4 and consequently causes its transmitter 6 to start transmitting to the receiver 10. Data is transmitted using LF signal which establish a communication link between key 4 and base station 8. The data transmitted between key 4 and base station 8 is defined by a communication protocol, which is followed by key 4 and the station base 8 and includes the transmission of authentication data from the key 4 to the receiver 10. Access to a protected place is guaranteed by the base station 8 only when the transmitted authentication data coincides with the authentication data stored by the base station 8. The authentication takes place through the transmitters / receivers 39 and 52 with the aid of the stimulus 60 and the response 62. After an algorithm memorized in the microcontroller 40 the st basic action 8 produces a stimulus 60. In this regard it is preferably a random number. In parallel to this, the base station 8 carries out an internal determination of the expected response signal, which is calculated on the basis of an established algorithm. The stimulus 60 sent by the transmitter / receiver 39 of the base station 8 is received by the transmitter / receiver 52 of the electronic key 4 and is forwarded by this to the local microcontroller 50. The identical algorithm is implemented in the microcontroller 50, as in the microcontroller 40 arranged from the base station side. The microcontroller 50 of the electronic key 4 from the incoming stimulus 60 calculates the response 62. The transmitter / receiver 52 sends this response 62 to the receiver / transmitter 39 of the base station 8 which the microcontroller 4 of the base station 8 evaluates. If the response received 62 and the response certifies, previously generated by the microcontroller 40 of the base station 8 concur, then a first authorization criterion is satisfied.

The second access authorization criterion is determined as follows with the aid of the spectral information of the signal 14. The microcontroller 50 of the electronic key 4, depending on the stimulus received 60, in accordance with a further or the same algorithm determines the influence of the spectral information of the signal 14 to be sent through the antenna 7. The signal 14 preferably consists of two sounds of fundamental frequency 20, 22 with the corresponding frequencies fi and f2. The amplitudes Al, A2 of the sounds of fundamental frequency 20,22 serve as spectral information to vary of the signal 14. The stimulus 60 by means of an algorithm increased in the microcontroller 40,50 defines the ratio between the amplitudes Al on A2. On the occasion of each transmission process, the stimulus 60 varies and therefore also the ratio between the amplitudes Al on A2 to be determined again and again. During the first transmission process, the ratio between the amplitudes has the value 1 (transmission spectrum 25 in Figure 2). In the context of a second access authorization operation, a stimulus 60 is received which is varied with respect to the stimulus 60 previously received and which the microcontroller 50 converts into a ratio between the amplitudes Al 'on A2' varied, for example 2 on 1 ( transmission spectrum 25 'in figure 2). To obtain a ratio between the amplitudes Al 'on A2' of 2 on 1, the microcontroller 50 controls the attenuator 54 of the second sound of fundamental frequency f2 in a corresponding manner. Subsequently the signal 14 is sent in the form of the transmission spectrum 25 '.

The reception spectra 21, 21 'of the signal 14 are detected by the receiver 10 of the base station 8. In addition to the fundamental sounds 20,22 of the frequencies fi, f2 with the corresponding amplitudes Al, Al', A2, A2 ', also two third-order intermodulation sounds 24,26. The fundamental sounds 20,22 are found in the neighboring frequency channels C2 and C3, while the intermodulation sounds 24,26, formed by combining the fundamental sounds 20,22, have a smaller amplitude and are located in a lower frequency channel CI and in a higher frequency channel C4. An RSSI spectral information of the signal 14, indicating the intensity of the input signal in the respective frequency channel CI up to C4, is detected by the receiver 36. Thus the amount of energy / signal strength received in each of the CI channels up to C4. The spectral information RSSI, produced by the receiver 36, is a voltage proportional to the energy which is in the respective frequency channel C1 up to C4. The signal strength for each CI frequency channel up to C4 can therefore be used to determine the spectral information. The local oscillator 42 controls the receiver 36, so that the intensity of the RSSI signal is raised for the second and third channels C2, C3, in which the fundamental sounds 20,22 are expected. The RSSI signal strength is proportional to the amplitude A1, A2 of the transmitted signal 14. The ratio is formed from the signal strength of the second channel C2 and the signal strength of the third channel C3.

With the first transmission operation, a stimulus 60 was sent to the electronic key 6 which corresponds to a ratio between the amplitudes A1 on A2 equal to 1. Therefore, even in the case of regular access, the ratio between the signal intensities of the second and the third channel C2, C3 must be equal to 1. This expected ratio of 1 is known to the base station 8, since the microcontroller 40 according to the same algorithm as the microcontroller 50 of the electronic key 4 determines the ratio between the expected amplitudes. If the actual ratio between the amplitudes, formed by the ratio between the intensity of current of the second and third frequency channels C2, C3, corresponds to the expected ratio thus previously determined by the microcontroller 40 of the base station 8, the second condition of authorization. The locking system not shown is operated in the direction of an opening.

For the second authorization operation the microcontroller 40 produces a varied stimulus 60, executed as a random number. From the stimulus 60 thus sent, both the microcontroller 40 of the base station 8 and also the microcontroller 50 of the electronic key 4, on the basis of a coincident algorithm, determine the new ratio between the amplitudes Al 'on A2' of the second (subsequent) authorization operation. The microcontroller 50 of the electronic key 4 controls the attenuator 54 so that the ratio between the amplitudes Al 'on A2' previously determined as 2 on 1 is obtained (corresponding to the embodiment example according to Figure 2). The signal 14 is subsequently sent. The base station 8 defines the RSSI signal strength in the second and third channels C2 and C3. From these the report is formed again. This ratio determined as spectral information is compared with the ratio between the amplitudes of 2 on 1 expected and previously calculated. In the case of a correspondence between the spectral information and the spectral information attests, the second authorization criterion is again satisfied. The microcontroller 40 produces a corresponding authorization signal 41, with which either the locking system or the immobilizer (or other safety-relevant components) is controlled.

In a further integration it is also possible to use the signal strength of the intermodulation points 24,26 with the additional authorization criterion. For this purpose, the signal intensity of the first channel C1 and of the fourth channel C4 is determined and this is compared with a spectral signature which has been previously formed. A deviation indicates that a manipulation amplifier station has been inserted which manifests itself as a result of the resulting frequency distortions. In the event of a significant move, no authorization is given.

In the embodiment example, the relationship between the signal intensities (spectral formation) was used as a further criterion - in addition to the question-answer procedure - for an authorization; however, it could also form the only authorization criterion.

The signal 14 is preferably transmitted in the other frequency range, while the stimulus 60 and the response 62 are transmitted in the low frequency range.

Claims (1)

Claims 1.-An authorization system with an electronic key (4) comprising at least one transmitter (6) for transmitting at least one signal (14) to at least one receiver (10) of a base station (8), where the base station (8) comprises conversion means (36,38,42) converting the transmitted signal (14) into at least one spectral information (Al, A2, RSSI), and comparator means (40) for comparing the spectral information (Al, A2, RSSI) with an expected spectral information and to produce an authorization signal (41) in case of correspondence between the spectral information (A1, A2, RSSI) and the expected spectral information, characterized in that the electronic key (4) comprises means of variation (50,52,54) to vary the spectral information (A1, A2, RSSI), transmitted in the signal (14) with respect to a spectral information transmitted in a previous transmission process. 2.-Access system according to Claim 1, characterized in that the variation means (50,52,54) comprise a receiver (52) which receives a sent stimulus (60), where the variation means modify the information spectral (A1, A2, RSSI) of the signal (14) depending on the stimulus (60). 3.-Access system according to one of the preceding claims, characterized in that the amplitude (A1, A2) is used as spectral information (A1, A2, RSSI), which appears for a given frequency (f1, f2) and, or the signal strength (RSSI) detected in a specific frequency band (C1, C2, C3, C4). 4.-Access system according to one of the preceding claims, characterized in that the base station (8) comprises calculation means (40) which determine the expected spectral information depending on the stimulus sent (60). 5.-Access system according to one of the preceding claims, characterized in that the variation means (50,52,54) modify the spectral information (RSSI, A1, A2) of the signal (14) with each transmission of the signal ( 14). 6. Access system according to one of the preceding claims, characterized in that the transmitter (6) comprises at least one frequency generator (30,32) which equips the signal (14) with at least two frequency components (20,22) . 7.-Access system according to one of the preceding claims, characterized in that a microcontroller (50) is provided in the key (4) which from the stimulus (60) determines a response (62) for authentication. 8. Access system according to one of the preceding claims, characterized in that a random number is used as the stimulus (60). 9. Access system according to one of the preceding claims, characterized in that the variation means (50,52,54) process only a part, preferably the beginning of the information sent in the stimulus (60). 10.-Procedure for granting the authorization, characterized by the following phases: - reception of a transmitted stimulus (60) by means of an electronic key (4) transmission of a signal (14), whose spectral information (A1, A2, RSSI) was influenced by means of variation (50,52,54) depending on the stimulus (60) - reception of the signal sent (14) by means of a base station (8) producing an authorization signal (41) - conversion of the signal (14) into a spectral information (A1, A2, RSSI) and comparison of the spectral information (A1, A2, RSSI) with an expected spectral information, wherein in case of correspondence an authorization signal (41) is produced to grant the authorization to drive and / or access a motor vehicle. 11. Process according to Claim 10, characterized in that a response (62) is determined from the stimulus (60) which is sent to the base station (8), whereby the base station (8) guarantees a travel authorization and, or access only when the received response (62) coincides with an expected response.