Portable ID transmitter for an authentication system and method for operating an authentication system

Description

[0001] The invention relates to an authentication system and a method for operating the authentication system. In particular, the invention relates to an authentication system with which a portable ID transmitter can be authenticated to the vehicle in order to enable vehicle functions for an operator carrying the portable ID transmitter.

[0002] Various so-called keyless entry systems are known from the state of the art. These are based on radio communication between a vehicle-based infrastructure and a portable ID transmitter. The desired authentication is carried out within the framework of the radio communication, for example, by exchanging and verifying encrypted authorization data.

[0003] WO 2016 / 046105 A1 discloses a system for locking / opening and / or starting a vehicle using BLE communication and UWB communication.

[0004] EP 0 965 710 A2 describes a vehicle control system which, among other things, provides for several antennas to be arranged on the vehicle.

[0005] EP 2 800 068 A2 describes a passive entry passive start (PEPS) system that uses UWB radio communication.

[0006] US 2007 / 0162191 A1 describes a control system of a vehicle.

[0007] GB2538341 A discloses a passive entry passive start (PEPS) system with an ID transmitter, which uses UWB radio communication with multiple UWB antennas, LF wake-up signals, and UHF response signals. WO 2016 / 059451 A1 also describes a passive access system to a vehicle with an ID transmitter, in which UWB radio communication is implemented with multiple parallel UWB antennas and the position of the ID transmitter is determined based on the signal strength of LF signals.

[0008] In the field of keyless entry systems, the use of low-frequency (LF) and high-frequency (HF) radio waves is well-known and widely used. Combined communication using LF / HF systems is also well-known.

[0009] In radio-based authorization systems, security is of crucial importance, especially against compromise of the radio communication being conducted. When enabling a vehicle function using portable ID transmitters, the determination of a position, a distance, or a similar value, for example, to verify the plausibility of the bidirectional communication being conducted, is known from the state of the art. For example, it is known to evaluate the signal strength of an LF radio communication between a portable ID transmitter and a vehicle-side authentication device. A complementary or alternative concept for increasing security against compromise can simply be based on limiting the transmission power of an LF communication.By limiting the transmission power of an LF communication between the vehicle and the ID transmitter, it is ensured that, for example, an LF wake-up signal sent from the vehicle to the ID transmitter can only be received by the other communication partner if a maximum distance between the ID transmitter and the vehicle is not exceeded.

[0010] Many of the known authentication systems still suffer from the fundamental disadvantage that LF or HF radio communication can be extended, for example, in the context of so-called relay station attacks. Countermeasures are required to prevent such or other compromises, some of which are, however, complex.

[0011] It is therefore an object of the invention to improve the known authentication methods so that they provide effective, but at the same time comparatively inexpensive, protection against compromise of the transmitted signals.

[0012] The object is achieved according to the invention with an authentication system having the features of claim 1 and with a method having the features of claim 11.

[0013] According to the invention, a vehicle authentication system is provided. The authentication system comprises a portable ID transmitter and a vehicle-mounted authentication arrangement. The ID transmitter comprises, in a housing: a supply battery, a microcontroller, UWB transmit and receive circuits controlled by the microcontroller for communication with a vehicle-side control unit, an LF receive circuit coupled to the microcontroller for receiving LF wake-up signals transmitted in the LF frequency range.

[0014] When the LF receiving circuit has received an LF wake-up signal, the microcontroller is configured to transmit a UWB signal for reception by a UWB interface of the vehicle coupled to the vehicle-side control unit. Furthermore, the microcontroller is configured to detect the reception of a UWB response signal by the UWB transmit and receive circuits, which also have a suitable UWB antenna. In response to the detected UWB response signal, the microcontroller can detect and evaluate the time difference between the transmission of the UWB signal and the reception of the UWB response signal. The microcontroller can evaluate the result of the evaluation to determine whether the time difference or a value derived from the time difference does not exceed a predetermined maximum value.According to the invention, the microcontroller is designed to transmit a radio signal having an enable value to the vehicle-side control unit depending on the result of the test.

[0015] An essential aspect of the method according to the invention is based on the use of ultra-wideband communication.

[0016] In principle, the use of ultra-wideband (UWB) radio signals for some applications is well known from the state of the art. However, commercially available transceivers for this purpose have only recently become available.

[0017] The fundamentals of ultra-wideband technology have been known for a long time. However, it has only recently become accessible for use in a wide range of applications, not least due to more liberal regulations.

[0018] Ultra-wideband technology is a short-range radio communication technology based on the transmission of short signal pulses covering a wide range of frequencies within a wide frequency bandwidth. The width of the covered frequency ranges depends primarily on the regulatory requirements of the respective territorial area. The signals are modulated using methods such as on / off keying, pulse amplitude modulation, or pulse position modulation.

[0019] A disadvantage of UWB communication compared to established LF and / or HF communication is the comparatively high energy consumption of many currently available transceivers suitable for UWB communication.

[0020] However, UWB communication has the fundamental advantage that, due to the transmission of pulses, distance is determined using a time-of-flight-based approach, which is often referred to as the time-of-flight method. For example, the distance between the first UWB antenna and the portable ID transmitter can be determined by sending a UWB signal from the first UWB antenna to the portable ID transmitter, a UWB transceiver of the portable ID transmitter responding to this signal, and a unit coupled to the first UWB antenna, such as a control unit, evaluating the received response signal. This is done by evaluating the elapsed time between transmission and reception. The distance to the ID transmitter, the processing time within the ID transmitter, and the distance from the ID transmitter to the first UWB antenna are taken into account.If, as in this example, the runtime is evaluated on the vehicle side, only the processing time within the ID transmitter needs to be stored on the vehicle side so that a corresponding correction of the time measured on the vehicle side between transmission of the UWB signal and reception of the UWB response can be made.

[0021] Experience has shown that the accuracy of such a UWB-based distance determination is significantly higher for the typically intended ranges than is the case with other methods, such as signal strength determination, typically using RSSI measurements of RF or BLE communication. The accuracy of UWB-based distance determinations is often on the order of 10 to 20 cm.

[0022] Because the pure propagation time of the UWB signal is relatively short compared to the processing time, any additional processing of the signal, for example, for manipulation of the signal as part of a relay station attack, could be detected due to the unexpectedly long total time between the transmission of a UWB signal and the arrival of the corresponding response. Compromises, for example, of the type described in the relay station attacks, are therefore only possible, if at all, with very complex methods.

[0023] Another advantage of using UWB signals is that, due to the large number of frequencies used, signal shadowing is very unlikely. This is because, for at least some of the frequencies used simultaneously, there is a high probability that there will always be a line of sight between the transmitter and receiver. One reason for this is that diffraction effects or reflections can be expected for some frequencies.

[0024] According to the invention, the authentication arrangement is designed to A) Selecting a UWB antenna from the number of UWB antennas of the authentication arrangement as the selected UWB antenna. The UWB antenna is selected at least as a function of one or more received signal strengths of at least one LF signal transmitted between the authentication arrangement and the ID transmitter. Embodiments not according to the invention may also provide for selection as a function of one or more received signal strengths of at least one HF signal transmitted between the ID transmitter and the authentication arrangement, wherein both possible transmission directions may be provided, and / or as a function of at least one proximity signal from one or more proximity sensors arranged on the vehicle; The invention further provides: B) Controlling the selected UWB antenna to perform UWB communication between the ID transmitter and the authentication arrangement. According to the invention, the ID transmitter is equipped with hardware (sufficiently high computing power, storage means with sufficient storage capacity) and programmed in such a way that it can determine the distance of the ID transmitter from a vehicle having a UWB interface completely independently. Carrying out this determination comprises transmitting a UWB signal, which causes a vehicle-mounted UWB transceiver adapted to the ID transmitter and / or a vehicle-mounted UWB antenna coupled to a control unit to transmit a UWB response signal.

[0025] Furthermore, the determination includes the correction of the time elapsed between the transmission of the UWB signal and the reception of the UWB response signal by the time period, previously communicated to the ID transmitter, for the reception, evaluation and transmission processes required by the vehicle-side infrastructure.

[0026] Essentially, the key aspect is checking whether the detected time difference is smaller than the specified maximum time difference. The latter is determined by knowing the electronically induced latency and specifying the maximum permitted propagation time for radio transmission, which is directly linked to a maximum tolerated distance. The electronically induced latency results, for example, from signal processing in the vehicle's control unit.

[0027] Initiating and performing distance detection has the advantage that, unlike the vehicle, the ID transmitter already knows that it is in the vicinity of the vehicle because it has already been awakened by the LF signal. Distance measurement can therefore begin without the need for a triggering process by the vehicle. This can potentially reduce the time required to determine the distance. A further advantage is that the LF signals, the reception of which requires only very low energy consumption, have already resulted in an initial pre-selection of potentially addressable ID transmitters. The number of UWB communications required by the vehicle can thus be significantly reduced, thereby achieving energy savings.

[0028] Preferably, the radio signal is a UWB signal.

[0029] If the ID sensor check shows that the time difference does not exceed the specified value, this is communicated to the vehicle's control unit. For this purpose, an enable value is transmitted via a radio signal—in the simplest case, a binary value or a code, for example—that informs the vehicle's control unit that the distance check by the ID sensor has produced the desired result.

[0030] One embodiment provides that the microcontroller is configured to transmit an authorization code with the radio signal.

[0031] For example, it can be provided that a challenge-response list is stored on a memory device on the ID transmitter side, which is coupled to the microcontroller. It can be provided that the microcontroller is configured to transmit a response value associated with the challenge value with the radio signal if the UWB response signal includes a challenge value.

[0032] According to the invention, the ID transmitter is designed to check a number of LF signals for an identity identifier, detect signal strength values ​​for the LF signals, and respond to the reception of the LF signals with an RF response signal. The RF response signal comprises the identity identifier of the LF signal with the strongest signal strength value and / or a list of identity identifiers with the associated signal strength values.

[0033] According to the invention, this information will be used when implementing a suitable method, for example by a vehicle-side control unit, to prioritize on the vehicle side from a number of UWB antennas arranged at a distance from one another on the vehicle, as to which of the UWB antennas is preferentially controlled.

[0034] A predefined minimum time interval after the RF response signal can be provided for the UWB response signal. This allows for the anticipation of an expected further movement of an operator toward the vehicle. This increases the probability that the operator is sufficiently close to the vehicle to be reached by the UWB signal. This eliminates the need for an otherwise necessary transmission of a further UWB signal if the minimum time interval is appropriately adjusted (based on empirical data and depending on the accepted false triggering rate).

[0035] According to one embodiment, it can be provided that the microcontroller carries out LF / HF communication and UWB communication at least partially in parallel with the advantage of a corresponding time saving.

[0036] According to a further embodiment, it can be provided that the LF receiving circuit and / or the UWB transmitting and receiving circuits are designed to assume a reduced-energy state in which they are not ready to receive and not ready to transmit compared to their normal operating state, and are coupled to a motion sensor in such a way that when the ID transmitter is moved, the LF receiving circuit and / or the UWB transmitting and receiving circuits are put into the normal operating state.

[0037] Furthermore, the ID transmitter can be designed as an exclusively passively activated ID transmitter, with a housing designed without a manually operable control element. This allows the ID transmitter to be used as a key fob and serves exclusively for passive function activation.

[0038] For functionality as a key fob, the ID transmitter can have a mechanical coupling element for coupling a key.

[0039] A second ID transmitter can be provided, which is designed as a manual HF radio key such that, by manually actuating a button arranged on the second ID transmitter, an HF request signal adapted to the vehicle-side control unit is transmitted to request a vehicle function. The second ID transmitter forms an authentication system with the ID transmitter. The two ID transmitters of the authentication system can be mechanically connected to each other with the mechanical coupling element, for example, a key chain ring, whereby no communication between the two is permitted.

[0040] According to this concept, a key system consisting of the ID transmitter and the second ID transmitter is provided, whereby the keys are designed to communicate with the same vehicle, but cannot communicate with each other. This concept enables a physical separation between the passive ID transmitter and the active ID transmitter (the second ID transmitter). This offers the advantage that two independently operating ID transmitters, depending on their equipment, are each allowed complete authentication to the vehicle and can therefore also be used separately. However, both can also serve as backups for each other if one of the two is not functioning, for example, due to a dead battery.

[0041] A further aspect of the invention relates to a method. The method provides for operating an authentication system of a vehicle to authenticate a portable ID transmitter to the vehicle. The authentication serves the purpose of enabling a vehicle function for an operator carrying the portable ID transmitter.

[0042] The authentication system includes the portable ID transmitter and a vehicle-side authentication arrangement.

[0043] The authentication arrangement comprises a number of UWB antennas, at least a first UWB antenna and a second UWB antenna. The first UWB antenna and the second UWB antenna are arranged spaced apart from each other on the vehicle. The method provides at least the following steps: A) Selecting a UWB antenna from the number of UWB antennas of the authentication arrangement as the selected UWB antenna. According to the invention, the UWB antenna is selected at least as a function of one or more received signal strengths of at least one LF signal transmitted between the authentication arrangement and the ID transmitter, and / or not according to the invention as a function of one or more received signal strengths of at least one HF signal transmitted between the ID transmitter and the authentication arrangement, wherein both possible transmission directions can be provided, and / or not according to the invention as a function of at least one proximity signal from one or more proximity sensors arranged on the vehicle;According to the invention, B) the selected UWB antenna is controlled to carry out UWB communication between the ID transmitter and the authentication arrangement; C) the UWB communication is carried out between the ID transmitter and the authentication arrangement; D) a propagation time of a UWB signal of the UWB communication between the ID transmitter and the selected UWB antenna is detected; E) whether the propagation time of the UWB signal is less than a predetermined maximum propagation time is checked.

[0044] According to the invention, before controlling a UWB antenna to carry out UWB communication, a selected UWB antenna is selected from the number of UWB antennas. By selecting a selected UWB antenna, it can be achieved under favorable circumstances that the information required for distance determination can be obtained by controlling only some of the UWB antennas of the authentication arrangement. If this is the case, further UWB communication using the other existing UWB antennas of the authentication arrangement can be dispensed with. The method according to the invention therefore advantageously reduces the energy required to carry out UWB communication during an authentication process.

[0045] Preferably, the first UWB antenna is part of a first UWB transceiver, and the second UWB antenna is part of a second UWB transceiver. This allows for a compact design and simple configuration.

[0046] According to the invention, the selected UWB antenna is controlled. Controlling the selected UWB antenna enables UWB communication between the ID transmitter and the authentication device.

[0047] To transmit a UWB signal, the ID transmitter explained above is used, which, in turn, via a UWB transmitting and receiving circuit (preferably designed as a UWB transceiver), initiates the transmission of a UWB signal, which is then detected and answered by the selected UWB antenna, whereupon the response transmitted as a UWB signal is detected and evaluated by the ID transmitter.

[0048] To technically implement the control of the selected UWB antenna, it can be provided, for example, that the authentication arrangement has UWB transceivers that include a UWB antenna as a component. For example, in a regular state, it can be provided that the first UWB transceiver with the first UWB antenna is in a non-transmitting and non-receiving state, and that, after a UWB antenna has been selected, a vehicle-mounted control unit controls the UWB transceiver with the selected UWB antenna in order to place the UWB antenna in a receive-ready state. Alternatively, it can also be provided that the vehicle-mounted control unit puts the UWB antenna in a transmit-ready state in a similar manner and initiates the transmission of the aforementioned UWB signal via the selected UWB antenna.

[0049] By transmitting a UWB signal and responding to the UWB signal, the UWB communication is carried out as intended according to the invention. Subsequently, the propagation time of the UWB signal can be recorded and the intended check can be performed to determine whether the propagation time of the UWB signal is less than a specified maximum propagation time.

[0050] If the propagation time of the UWB signal is less than a specified maximum propagation time, the vehicle can assume that the bidirectional UWB communication has not been extended. Depending on security requirements, the maximum propagation time can be adjusted to ensure a sufficiently high accuracy of the distance determination, while at the same time ensuring that compromise of the UWB signal can be ruled out or largely ruled out within the recorded maximum propagation time.

[0051] The ID transmitter explained above enables the vehicle to select a UWB antenna from the number of available antennas, which is then controlled to conduct UWB communication. By selecting a UWB antenna from the available UWB antennas, the implementer of the method for a specific application is given the option of reducing the energy required for UWB communication depending on one or more previously recorded parameters. Depending on the practicality and / or security requirements pursued or to be considered by the implementing developer, different parameters can be used. It is advisable to use a less energy-intensive method than UWB communication to record these parameters, or to use existing, already recorded parameters.Based on this data, it can then be determined by means of a control means, preferably a vehicle-side control means, with which UWB antenna a UWB communication is carried out and / or in which order various of the existing UWB antennas are used for a UWB communication.

[0052] According to the invention, the selection of the UWB antenna is made depending on the received signal strength of an LF signal that is sent from the authentication arrangement to the ID transmitter, as already indicated at the beginning. For this purpose, the ID transmitter explained at the beginning, which can be configured for LF communications, is used. The term LF interface refers to a set of devices required for LF communication and includes at least one LF antenna and a receiving circuit coupled to the LF antenna. Such an arrangement is already provided in many cases in connection with the ID transmitters mentioned at the beginning, as well as with the ID transmitter according to the invention in one of its developments.For example, an LF signal can be sent from one or more LF interfaces of the vehicle-side authentication arrangement to the ID transmitter, which receives it with an LF receiving device and subsequently determines the signal strength. For example, it can be provided that two LF interfaces arranged at different positions in the vehicle each send a differently coded LF signal to the ID transmitter, and the ID transmitter sends the detected signal strength values, for example in the form of RSSI values, together with the respective code of the ID transmitter back to the vehicle-side HF interfaces. Such data can then be evaluated by a vehicle-side control device. As a result of the evaluation, it can be determined, for example, that the UWB antenna of the authentication arrangement that is closest to the LF interface with the strongest LF signal is controlled with priority.

[0053] In a further development of the method, it is provided that the above-mentioned steps B) to E) are initially carried out with a first selected UWB antenna and, if the propagation time of the UWB signal between the ID transmitter and the first selected antenna is greater than a predetermined maximum propagation time, at least steps B) to E) are carried out again. In contrast to the first execution of steps B) to E), the repeated execution of steps B) to E) is carried out with a second selected UWB antenna with the aim of checking whether the propagation time of the UWB signal between the ID transmitter and the second selected antenna is less than the predetermined maximum propagation time.

[0054] It is therefore provided that, in addition to carrying out the method according to the invention using a first selected antenna, in the event of failure, a second UWB antenna of the vehicle-side authentication arrangement is selected to perform a distance determination. This increases the reliability of the method. In a case in which, for example, there is a - albeit unlikely - shadowing of the first UWB antenna, an incorrect result of the distance determination is avoided even if the ID transmitter is actually sufficiently close to the vehicle. By sequentially repeating method steps B) to E), first with the first UWB antenna and then with the second UWB antenna, the prioritization of the UWB antennas is taken into account. This ensures that in many cases the method is already successful with the first selected antenna.The increase in reliability is therefore not accompanied by a disproportionate increase in energy consumption.

[0055] Further details, features and advantages of the method according to the invention and its further development will become apparent from the following description in conjunction with the drawings in which exemplary embodiments of the invention are shown.

[0056] It is understood that the features mentioned above and explained below can be used not only in the specified combination, but also in other combinations or on their own. They show: Fig. 1 : a schematic representation of an ID transmitter according to the invention and an authentication system of a vehicle; Fig. 2 : a flowchart of an exemplary process sequence of the method according to the invention.

[0057] Fig. 1 Key system 1 for an authentication system of a vehicle can be seen. The key system 1 comprises an embodiment of the ID transmitter 3 according to the invention and a second ID transmitter 2 . The ID transmitter 3 has a supply battery 9. Furthermore, there are: a microcontroller 12, UWB transmit and receive circuits 11 controlled by and connected to the microcontroller 12 for communication with a vehicle-side control unit, an LF receive circuit 10 controlled by and connected to the microcontroller 12 for receiving LF wake-up signals transmitted in the LF frequency range. The ID transmitter 3 also has a housing 13 designed as a closed housing without any operating elements. The second ID transmitter 2 has an HF transmit and receive interface 5 controlled by a microcontroller 6, which enables a function of a vehicle upon pressing the operating element 7 designed as a button. Only active operation is provided, but no passive functionality of the second ID transmitter. A key bit 4 is provided for mechanical function enablement.A mechanical coupling element 8 designed as a connecting ring connects the ID transmitter and the second ID transmitter in a separable and reconnectable manner; the ID transmitter thus functions as a key fob.

[0058] Fig. 2 A first possible procedure for carrying out the method according to the invention using the ID transmitter according to the invention can be seen.

[0059] The exemplary method implementation provides that in a step 201, the approach of an operator to the first proximity sensor is detected. The proximity sensor outputs a corresponding proximity signal in step 202. Because the first proximity sensor and the antenna of the first vehicle UWB interface are arranged in the door handle and coupled to one another, it is provided that the first control means switches the first UWB antenna from a non-transmitting and / or non-receiving state to a transmitting state (step 203). A first vehicle-side LF interface outputs an LF wake-up signal (step 203), and the first control means controls a vehicle UWB interface to switch the first vehicle UWB interface from a non-transmitting and / or non-receiving state to at least a receiving state.The ID transmitter then sends a UWB signal, which the first vehicle UWB interface receives. The transmitted UWB signal responds to the vehicle's UWB interface with a UWB response signal (step 204). The ID transmitter receives the response signal and determines a propagation time of the UWB signal and the UWB response signal between the ID transmitter and the first vehicle UWB interface. The ID transmitter transmits the propagation time or a parameter derived from it, preferably via UWB, to a data receiver in the vehicle (step 205). After detecting the propagation time of the UWB signal between the ID transmitter interface and the first vehicle UWB interface, the ID transmitter checks whether the propagation time of the UWB signal is less than a predetermined maximum propagation time. If this is the case, the ID transmitter is considered to be within the space in which release is permitted (secure bubble).Furthermore, a compromise of the signal, for example, through a relay station attack, is deemed not to have occurred. However, if it is determined in step 206 that the propagation time is greater than the specified maximum propagation time, the process sequence continues analogously with step 208, but using the second UWB antenna.

Claims

1. Authentication system for a vehicle, comprising a portable ID transmitter (3) and a vehicle-side authentication arrangement, wherein the authentication arrangement comprises a number of UWB antennas with at least a first UWB antenna and a second UWB antenna arranged at a distance from each other on the vehicle, wherein the ID transmitter (3) has a housing (13): - a supply battery (9), - a microcontroller (12), - UWB transmitter and receiver circuits (11) controlled by the microcontroller (12) for communication with a control unit on the vehicle, - an LF receiver circuit (10) coupled to the microcontroller (12) for receiving LF wake-up signals transmitted in the LF frequency range, whereby the microcontroller (12) is set up to, when the LF receiver circuit has received an LF wake-up signal, transmit a UWB signal for reception by a UWB interface of the vehicle, which is coupled to the vehicle's control unit, to receive a UWB response signal, to capture the time difference between sending the UWB signal and receiving the UWB response signal, to check whether the time difference or a value derived from the time difference does not exceed a specified maximum value, and depending on the result of the checking, transmit a radio signal to the vehicle's control unit that has an enable value wherein the ID transmitter is designed to check a number of LF signals for an identity identifier, to detect signal strength values for the LF signals and to respond to the reception of the LF signals with an RF response signal which includes the identity code of the LF signal with the strongest signal strength value and / or a list of identity codes with the assigned signal strength values, whereby the authentication arrangement is designed to carry out: selecting a UWB antenna from the number of UWB antennas of the authentication arrangement as the selected UWB antenna, the UWB antenna being selected at least as a function of the received signal strength or the received signal strengths of the at least one LF signal which is transmitted between an LF interface of the authentication arrangement and the ID transmitter; and controlling the selected UWB antenna to perform UWB communication between the ID transmitter and the authentication device.

2. Authentication system according to claim 1, characterised in that the microcontroller is set up to transmit a UWB signal to the control unit on the vehicle as the radio signal.

3. Authentication system according to claim 1 or claim 2, characterised in that the microcontroller is set up to transmit an authorisation code with the radio signal.

4. Authentication system according to claim 3, characterised in that a challenge-response list is stored on a memory means on the ID transmitter side, which is coupled to the microcontroller (12), and in that the microcontroller (12) is designed to transmit a response value assigned to the challenge value with the radio signal, if the UWB response signal comprises a challenge value.

5. Authentication system according to one of the preceding claims, characterised in that the UWB signal is transmitted with a predetermined minimum time interval after the RF response signal.

6. Authentication system according to one of the preceding claims, characterised in that the microcontroller is designed to carry out LF communication and UWB communication at least partially in parallel.

7. Authentication system according to one of the preceding claims, characterised in that the LF receiving circuit and / or the UWB transmitting and receiving circuits are designed to assume an energy-reduced state, in which they are not ready to receive and not ready to transmit compared to their normal operating state, and are coupled to a motion sensor in such a way that when the ID transmitter is moved, the LF receiving circuit and / or the UWB transmitting and receiving circuits are / are set to the normal operating state.

8. Authentication system according to one of the preceding claims, characterised in that the ID transmitter (3) is designed as an exclusively passively activatable ID transmitter (3), the housing (13) of which is designed without a manually operable operating element.

9. Authentication system according to claim 8, characterised in that the ID transmitter has a mechanical coupling element (8) for coupling a key (2).

10. Authentication system for a vehicle according to one of the preceding claims, comprising the ID transmitter (3) and a second ID transmitter (2), wherein the second ID transmitter (2) is designed as a manual HF radio key in such a way that by manually actuating a button (7) arranged on the second ID transmitter (2), an RF request signal adapted to the control unit on the vehicle is transmitted to request a vehicle function, so that the ID transmitter (3) and the second ID transmitter (2) form a key system and are designed to communicate with a same vehicle, but not with each other.

11. Method of operating an authentication system of a vehicle for authenticating a portable ID transmitter to the vehicle for enabling vehicle functions for an operator carrying the portable ID transmitter, wherein the ID transmitter (3) has in a housing (13): - a supply battery (9), - a microcontroller (12), - UWB transmitter and receiver circuits (11) controlled by the microcontroller (12) for communication with a control unit on the vehicle, - an LF receiver circuit (10) coupled to the microcontroller (12) for receiving LF wake-up signals transmitted in the LF frequency range, whereby the microcontroller (12) is set up to, when the LF receiver circuit has received an LF wake-up signal, transmit a UWB signal for reception by a UWB interface of the vehicle, which is coupled to the vehicle's control unit, to receive a UWB response signal, to record the time difference between sending the UWB signal and receiving the UWB response signal, to check whether the time difference or a value derived from the time difference does not exceed a specified maximum value, and depending on the result of the checking, transmit a radio signal to the vehicle's control unit that has an enable value wherein the ID transmitter is designed to check a number of LF signals for an identity identifier, to detect signal strength values for the LF signals and to respond to the reception of the LF signals with an RF response signal which includes the identity code of the LF signal with the strongest signal strength value and / or a list of identity codes with the assigned signal strength values, wherein the authentication system comprises the portable ID transmitter and a vehicle-side authentication arrangement, wherein the authentication arrangement comprises a number of UWB antennas with at least a first UWB antenna and a second UWB antenna arranged spaced apart from each other on the vehicle, wherein the method comprises at least the following steps: A) Selecting a UWB antenna by a control device on the vehicle side from the number of UWB antennas of the authentication arrangement as the selected UWB antenna, wherein the selection of the UWB antenna takes place at least as a function of a received signal strength or several received signal strengths of the at least one LF signal which is transmitted between the LF interface of the authentication arrangement and the ID transmitter; B) Controlling the selected UWB antenna to perform UWB communication between the ID transmitter and the authentication device; C) Carrying out the UWB communication between the ID transmitter and the authentication device; D) Detecting of a runtime of a UWB signal of the UWB communication between the ID transmitter and the selected UWB antenna; E) Checking whether the runtime of the UWB signal is shorter than a specified maximum runtime, whereby the UWB signal is detected and analysed by the ID transmitter.

12. Method according to claim 11, wherein steps B) to E) are carried out with a first selected UWB antenna and, if the propagation time of the UWB signal between the ID transmitter and the first selected antenna is greater than a specified maximum propagation time, at least steps B) to E) are performed with a second selected UWB antenna to check whether the propagation time of the UWB signal between the ID transmitter and the second selected antenna is less than the predetermined maximum propagation time, which represents a position of the ID transmitter within a predetermined space surrounding the second selected UWB antenna.