DE102017206008B4 - Key device, authentication device, authentication system, method for releasing a vehicle and computer-readable storage medium - Google Patents

Abstract

Key device (20), in particular for a vehicle (10), comprising:a key transmitting device (23) which is designed to:- send a key data signal (31), in particular to the vehicle (10), wherein the key data signal (31) encodes a key data sequence (30); and- send a confirmation data signal (41), in particular to the vehicle (10), wherein the confirmation data signal (41) encodes a confirmation data set (40), whereina key computing device (21) which is designed to generate the confirmation data signal (41) using a spreading technique, characterized in thata spreading code (44) is selected such that the power density (47) of the confirmation data signal (41) at a measuring distance from the key transmitting device (23) is lower than the noise power density (61).

Description

The invention relates to a key device, an authentication device, an authentication system, a method for releasing a vehicle and a computer-readable storage medium.

Modern vehicles, such as cars or trucks, have beardless key systems. The beardless keys allow access to the vehicle without the driver having to insert the key into a lock. In addition, it is possible to start the vehicle, e.g. at the push of a button, if the beardless key is inside the driver's passenger compartment.

Previous beardless key systems can be exposed to attacks by hackers.

A well-known approach to increasing the security of beardless key systems is to use acceleration sensors in the key. The key then only sends signals when the key is moving. Another possibility is to use runtime measurements to ensure that a key signal is only accepted by the vehicle if the response to a request is within its very narrow time window. If a runtime measurement of the signals is carried out, the distance of the key to the receivers in the vehicle can be determined. This means that it can be ensured that the key is in or near the vehicle.

Improving security using time-of-flight measurements is extremely complex. It is usually necessary for the key to be inside the passenger compartment in order to start the vehicle. The distance between the key and a receiving device inside the vehicle is therefore very small. Since the signals propagate at the speed of light, measuring the time of flight is very complex.

For example, several receivers must be installed on the vehicle. This makes the system very complex and expensive.

From the WO 2016/059451 A1 is a passive access system for a vehicle in which a break-in attempt can be detected and prevented by redundantly measuring a distance between the vehicle and the key and comparing the measurements.

From the DE 10 2007 028 732 A1 A method is known for keeping the necessary spreading codes smaller when using passive access systems of a vehicle by multiple spreading of payload data in order to enable applications over longer distances.

The DE 10 2015 017 146 A1 describes a method for determining the distance between a vehicle and a key.

Based on this prior art, the object of the present invention is to provide a key device, an authentication device, an authentication system, a method for unlocking a vehicle and a computer-readable storage medium that eliminate the aforementioned disadvantages. In particular, a key device is to be provided that increases the theft security of a vehicle. Furthermore, a corresponding authentication device, an authentication system, a method for unlocking a vehicle and a computer-readable storage medium are to be provided.

This object is achieved by the key device according to claim 1, the authentication device according to claim 8, the authentication system according to claim 11, the method for releasing a vehicle according to claim 13 and by the computer-readable storage medium according to claim 19.

• eine Schlüssel-Sendeeinrichtung, die dazu ausgebildet ist:
  • - ein Schlüsseldatensignal, insbesondere an das Fahrzeug, zu senden, wobei das Schlüsseldatensignal eine Schlüsseldatenfolge kodiert und
  • - ein Bestätigungsdatensignal, insbesondere an das Fahrzeug, zu senden, wobei das Bestätigungsdatensignal einen Bestätigungsdatensatz kodiert,

wobei eine Schlüssel-Recheneinrichtung vorgesehen ist, die dazu ausgebildet ist, das Bestätigungsdatensignal unter Verwendung einer Spreiztechnik zu erzeugen.In particular, the object is achieved by a key device, in particular for a vehicle, comprising:

• a key transmitting device designed to:
  • - to send a key data signal, in particular to the vehicle, wherein the key data signal encodes a key data sequence and
  • - to send a confirmation data signal, in particular to the vehicle, wherein the confirmation data signal encodes a confirmation data set,

wherein a key computing device is provided which is adapted to generate the confirmation data signal using a spreading technique.

A core of the invention is therefore that the key transmitting device transmits two signals to the vehicle. A two-stage security system is thus provided. Firstly, by means of the confirmation data set and the associated confirmation data signal and secondly with the key data sequence and the associated key data signal. The key data signal encodes a key data sequence and the confirmation data signal encodes a confirmation data set.

The confirmation data signal can be sent, for example, in response to a request signal from the vehicle. It is therefore used to confirm that the key device is in the vicinity of the vehicle. Since the confirmation data signal is generated using a spreading technique, it can only be reconstructed with knowledge of the spreading technique used. Security is therefore increased by the fact that the confirmation data signal cannot be reconstructed without knowledge of the spreading technique used.

In one embodiment, the key transmitting device can be designed to generate the confirmation data signal by bit-by-bit coding, in particular by means of an XOR operation, of the confirmation data set with a spreading code.

Bit-by-bit coding provides a particularly efficient method for generating the confirmation data signal. When a spreading code is used, this acts as a second code, since the signal cannot be reconstructed without it.

In one embodiment, a key synchronization device may be provided, wherein the key computing device may be configured to generate the confirmation data signal using the key synchronization device.

It is therefore possible for the confirmation data signal to be generated using a key synchronization device. For example, the confirmation data signal can be generated synchronously with a reference signal. In addition, knowledge of the synchronization behavior is important so that the spreading technique can be used effectively. The embodiment described therefore increases the quality of the confirmation data signal.

In one embodiment, the key transmitting device can be designed to transmit synchronization data, in particular to a/the vehicle, wherein the synchronization data can be used to determine a distance between the key device and a/the vehicle.

The key device of the embodiment described above further increases security by allowing measurement of the distance between the key device and the vehicle. A third level of security is thus provided. Distance measurement is advantageous in order to ensure that the key device is inside the vehicle.

A spreading code is selected such that the power density of the confirmation data signal at a measuring distance from the key transmitting device, in particular within a measuring distance of less than 300 cm, preferably less than 100 cm, is lower than the, in particular thermal, noise power density.

By using a spreading code for the spreading technique that is selected such that the power density of the confirmation data signal is lower than the noise power density, it becomes impossible for a third party to reconstruct the confirmation data signal without knowing the exact spreading code. The confirmation data signal is essentially lost in the noise. This results in a significant increase in security.

In one embodiment, the confirmation data record has a length of less than 128 bits, in particular less than or equal to 64 bits, preferably exactly one bit.

The confirmation data set can therefore be very short. This means that very low transmission power can be used.

In one embodiment, the confirmation data signal can be assigned a baud rate and a chip rate, wherein the ratio of chip rate and baud rate indicates a spreading factor which is in particular greater than 10 ³ , preferably greater than 10 ³ .

The baud rate indicates the number of symbols transmitted per unit of time. The chip rate indicates the number of chips transmitted per unit of time. A chip indicates a single elementary modulation state. With a spreading factor greater than 1, the chip rate is therefore greater than the baud rate. This means that a large number of chips are transmitted per symbol.

• - eine Empfangseinrichtung zum Empfangen:
  • ◯ eines Schlüsseldatensignals, wobei das Schlüsseldatensignal eine Schlüsseldatenfolge kodiert; und
  • ◯ eines Bestätigungsdatensignals, wobei das Bestätigungsdatensignal einen Bestätigungsdatensatz kodiert;
• - eine Sperreinrichtung, die dazu ausgebildet ist, ein Freigabesignal zu erzeugen, wenn der Bestätigungsdatensatz und die Schlüsseldatenfolge durch die Sperrvorrichtung validiert sind,

wobei eine Dekodiereinrichtung vorgesehen ist, die dazu ausgebildet ist, den Bestätigungsdatensatz aus dem Bestätigungsdatensignal unter Verwendung einer Spreiztechnik wiederherzustellen, wobei ein Spreizcode derart ausgewählt ist, dass die Leistungsdichte des Bestätigungsdatensignals in einem Messabstand von der Schlüssel-Sendeeinrichtung geringer ist als die Rauschleistungsdichte.The object is further achieved in particular by an authentication device, in particular for a vehicle, in particular for a key device as described above, comprising:

• - a receiving device for receiving:
  • ◯ a key data signal, the key data signal encoding a key data sequence; and
  • ◯ an acknowledgement data signal, the acknowledgement data signal encoding an acknowledgement data set;
• - a locking device which is designed to generate an enable signal when the confirmation data set and the key data sequence are validated by the locking device,

wherein a decoding device is provided which is designed to recover the confirmation data set from the confirmation data signal using a spreading technique, wherein a spreading code is selected such that the power density of the confirmation data signal at a measuring distance from the key transmitting device is lower than the noise power density.

The authentication device processes the confirmation data set and the key data sequence to generate an enable signal. Using two separate signals to generate the enable signal increases the security of the authentication device. Security is particularly increased by using a spreading technique to recover the confirmation data set, as described above.

In one embodiment, the decoding device can be designed to restore the confirmation data set by bit-by-bit decoding, in particular by means of an XOR operation, of the confirmation data signal with a spreading code.

Using bit-by-bit decoding is a particularly efficient way of processing signals. It also increases the security of the authentication device because knowledge of the spreading code is necessary to recover the confirmation record.

In one embodiment, the decoding device may be configured to recover the confirmation data set using synchronization data associated with the confirmation data signal.

To restore the acknowledgement record, synchronization data can be used, which e.g. indicates how the received acknowledgement data signal must be correlated with a spreading code. This further increases security, since the synchronization data must also be received to successfully restore the acknowledgement record.

• - eine Schlüsseleinrichtung wie vorstehend beschrieben,
• - eine Authentifizierungseinrichtung, wie sie vorstehend beschrieben wurde,

wobei die die Schlüsseleinrichtung und die Authentifizierungseinrichtung dazu ausgebildet sind, um einen gemeinsamen Spreizcode zu verwenden.The object is further achieved by an authentication system, in particular for a vehicle, comprising:

• - a key device as described above,
• - an authentication device as described above,

wherein the key device and the authentication device are adapted to use a common spreading code.

In one embodiment, the authentication system may comprise a decoding device which may be configured to synchronize the authentication device with the key device with respect to the spreading code.

This results in similar or identical advantages as those already described in connection with the key device and the authentication device.

• - Erzeugen eines Bestätigungsdatensignals aus einer Bestätigungsdatenfolge unter Verwendung eines Spreizcodes;
• - Senden des Bestätigungsdatensignals und eines Schlüsseldatensignals, das eine Schlüsseldatenfolge kodiert;
• - Empfangen des Bestätigungsdatensignals und des Schlüsseldatensignals;
• - Wiederherstellen der Bestätigungsdatenfolge aus dem Bestätigungsdatensignal unter Verwendung des Spreizcodes;
• - Validieren der Bestätigungsdatenfolge und der Schlüsseldatenfolge;
• - Freigeben eines Fahrzeugs, wenn die Bestätigungsdatenfolge und die Schlüsseldatenfolge validiert sind

wobei der Spreizcode derart ausgewählt ist, dass die Leistungsdichte des Bestätigungsdatensignals in einem Messabstand von der Schlüssel-Sendeeinrichtung geringer ist als die Rauschleistungsdichte.The object is further achieved by a method for releasing a vehicle, which comprises the following steps:

• - generating an acknowledgement data signal from an acknowledgement data sequence using a spreading code;
• - transmitting the acknowledgement data signal and a key data signal encoding a key data sequence;
• - Receiving the confirmation data signal and the key data signal;
• - recovering the acknowledgement data sequence from the acknowledgement data signal using the spreading code;
• - Validating the confirmation data sequence and the key data sequence;
• - Releasing a vehicle when the confirmation data sequence and the key data sequence are validated

wherein the spreading code is selected such that the power density of the confirmation data signal at a measuring distance from the key transmitting device is lower than the noise power density.

In one embodiment, validating may include comparing the key data sequence with a validation code.

In one embodiment, recovering may include correlating the received acknowledgement data signal with the spreading code.

In one embodiment, restoring may include synchronizing with respect to the spreading code.

In one embodiment, synchronization may be performed using a fixed synchronization interval.

In one embodiment, a distance measurement may be performed, wherein the distance measurement may be performed using synchronization.

The object is further achieved by a computer-readable storage medium containing instructions that cause (at least) one processor to implement a method as described above when the instructions are executed by the processor.

This results in similar or identical advantages as those already described in connection with the key device or the authentication device.

The invention is described below using embodiments, which are explained in more detail using figures.

• 1 eine perspektivische Draufsicht auf ein Fahrzeug;
• 2 eine schematische Darstellung eines Fahrzeugs und eines Fahrzeugschlüssels;
• 3a das Spreizen eines Signals;
• 3b das Entspreizen eines Signals;
• 4 ein gespreiztes Signal;
• 5a ein Signal vor der Spreizung;
• 5b ein Signal nach der Spreizung, welches eine Leistungsdichte unterhalb der Rauschleistungsdichte aufweist;
• 6 ein Sequenzdiagramm, welches die Funktionsweise der Erfindung in einem ersten Ausführungsbeispiel zeigt; und
• 7 ein Sequenzdiagramm, welches die Funktionsweise der Erfindung in einem zweiten Ausführungsbeispiel zeigt.

Here we show:

• 1 a perspective top view of a vehicle;
• 2 a schematic representation of a vehicle and a vehicle key;
• 3a spreading a signal;
• 3b despreading a signal;
• 4 a spread signal;
• 5a a signal before spreading;
• 5b a signal after spreading which has a power density below the noise power density;
• 6 a sequence diagram showing the operation of the invention in a first embodiment; and
• 7 a sequence diagram showing the operation of the invention in a second embodiment.

In the following, the same reference numbers are used for identical or equivalent parts.

1 shows schematically an authentication system 1, which comprises a vehicle 10 and a vehicle key 20. The vehicle key 20 is in the embodiment of the 1 arranged inside the vehicle 10. In this state, the vehicle 10 is enabled for starting. This means that a driver can start the vehicle 10, for example, by pressing a start button.

In the case where the vehicle key 20 is outside the vehicle 10, the driver of the vehicle 10 cannot start the vehicle 10.

The 2 shows a schematic representation of the authentication system 1, which comprises the vehicle 10 and the vehicle key 20. The vehicle key 20 comprises a key computing device 21, a key storage device 22, a key transmitting device 23 and a key synchronization device 24.

To release the vehicle 10, the vehicle key 20 sends two signals via its key transmitting device 23: a key data signal 31 and a confirmation data signal 41.

In the embodiment shown, the key data signal 31 comprises a key data sequence 30, which is part of an encryption method. The encryption method can be an asymmetric or a symmetric encryption method. In the simplest case, secret key data is therefore transmitted via the key data signal 31.

The confirmation data signal 41 is an additional signal that is required to release the vehicle 10. The confirmation data signal 41 is a signal that is spread using a spreading code and does not transmit any useful data as such. Rather, only a single bit is transmitted using the confirmation data signal 41 in the embodiment shown.

The vehicle 10 comprises a vehicle receiving device 11 for receiving the key data signal 31 and the confirmation data signal 41. In addition, the vehicle 10 comprises a vehicle computing device 14 for processing the received signals 31 and 41 and a vehicle storage device 15 for storing the transmitted data. For communication between the key device 20 and the vehicle 10, the vehicle 10 further comprises a vehicle transmitting device 13. If the vehicle computing device 14 determines that the key data signal 31 has transmitted a permissible key data sequence 30 and if the vehicle computing device 14 determines that the confirmation data signal 41 has been received, the vehicle locking device 12 releases the vehicle 10. This means that the driver of the vehicle 10 can then start the vehicle 10.

The 3a and 3b show the spreading and despreading of a signal. In the example of the 3a A confirmation data set 40 should be created by means of a spreading code 44 so that the confirmation data signal 41 is generated. In the embodiment shown, the confirmation data set 40 comprises only a single bit, which is set to the value 1. The confirmation data set 40 is vectorially converted into confirmation data 45 using the spreading code 44 by means of an XOR operation. This means that each bit of the spreading code 44 is individually processed with the bit of the confirmation data set 14 using the XOR operation. The spread confirmation data 45 is transmitted from the key device 20 to the vehicle 10 in the confirmation data signal 41.

The 3b shows how the vehicle 10 restores the confirmation data set 40 from the received confirmation data signal 41. For this purpose, the spreading code 44 is stored in the vehicle memory device 15 and is processed with the received confirmation data 45 using the XOR operation. This results in confirmation data 46 after decoding, from which the confirmation data set 40 can be restored.

The 4 shows the relationship between the confirmation data set 40 and the confirmation data signal 41. In the upper section of the 4 shows how the confirmation data set 40 behaves over time. Since the confirmation data set 40 consists of only a single bit with the value 1, the value is 1 over all times t0-t7. In contrast, the lower part of the 4 the confirmation data signal 41 over the times t0-t7. As the 3a and 3b As can be seen, the confirmation data signal 41 has the value 0 at times t0 and t1. At times t2, t3 and t4 the signal 41 has the value 1. At times t5, t6 and t7 the value drops back to the value 0. For one value of the confirmation data set 40, eight values are therefore transmitted in the confirmation data signal 41. The values of the confirmation data set 40 are called symbols and the values of the confirmation data signal 41 are called chips.

The 5a and 5b show how the confirmation data signal 41 can be hidden in the thermal noise floor 60 by a suitable spreading code 44.

The 5a shows how the confirmation data signal 41 is transmitted over a large number of frequencies f when no code spreading is used. The power density of the confirmation data signal 47 is significantly higher than the power density 61 of the background noise 60. In the embodiment shown, the signal 41 therefore has a signal-to-noise ratio that is significantly greater than 1.

The noise floor 60 is determined, for example, by thermal influences.

The 5b shows the confirmation data signal 41 after code spreading. The spreading code 44 is selected such that the power density 47 of the confirmation data signal 41 is below the power density 61 of the background noise 60. The confirmation data signal 41 therefore has a signal-to-noise ratio of less than 1.

Because the power density 47 of the confirmation data signal 41 is below the power density 61 of the background noise signal 60, the confirmation data signal 41 can only be recognized by the vehicle receiving device 11 if the spreading code 44 is known on the vehicle side. The spreading code 44 therefore acts as a security mechanism.

6 shows a sequence diagram which illustrates the signals sent and received by the vehicle 10 and the key 20. In a first step, the vehicle 10 sends a request signal 50 to the vehicle key 20. In step S1, the vehicle key 20 generates a confirmation data signal 41 in response to the request signal 50 using a spreading code 44. A key data signal 31 is also generated with which key data 30 is transmitted. The confirmation data signal 41 and the key data signal 31 are transmitted in parallel or approximately in parallel to the vehicle 10. The vehicle 10 reconstructs the confirmation data sequence 40 from the confirmation data signal 41 in step S4 using the spreading code 44. In step S5, it is then checked whether the confirmation data sequence 40 is correct and whether the transmitted key data sequence 30 is correct. For this purpose, the received key data sequence 30 is compared with data stored in the vehicle storage device 15. Preferably, the data is already stored in the key device 20 and in the vehicle storage device 15 at the factory.

If the correct data has been received, the vehicle 10 is released in step S6. This means that the driver can now start the vehicle 10.

In the 7 An embodiment is shown in which, in addition to the 6 synchronization and distance measurement are carried out using the method shown.

For this purpose, a wake-up signal 90 is first sent from the vehicle 10 to the vehicle key 20. In response to receiving the wake-up signal 90, the key 20 sends a confirmation signal 91 to the vehicle 10. The vehicle 10 now sends two signals. Firstly, a request signal 92 is sent to the vehicle key 20 and secondly, a first synchronization signal 93 is sent using a spreading technique as described above. After a previously defined and constant synchronization interval Sync1 has elapsed, the vehicle key 20 sends a second synchronization signal 94 to the vehicle 10.

The vehicle 10 now determines a synchronization interval Sync2, which indicates the time period that has elapsed since the first synchronization signal 93 was sent and the second synchronization signal 94 was received. If the synchronization interval Sync1 and the synchronization interval Sync2 are known on the vehicle 10, it can be determined what the travel time of the signals between the vehicle 10 and the key device 20 is, since the speed of the signals is determined by the speed of light.

Using the determined travel times of the signals, the vehicle 10 can determine the distance of the key 20 from the vehicle 10. If it is determined that the key 20 is most likely located inside the vehicle 10, the vehicle 10 sends a third synchronization signal 95 to the key device 20. All synchronization signals 93, 94, 95 are generated using a spreading technique. Using the third synchronization signal 95, the vehicle key 20 generates a key data signal 96 associated with the request signal 92. The key data signal 96 includes a code that can be verified by the vehicle 10.

The 7 The embodiment shown has a variety of security mechanisms. Firstly, it is necessary for the key device 20 and the vehicle 10 to know the spreading code used to generate and receive the synchronization signals 93, 94, 95. In addition, the data transmitted via the key data signal 96 must be correct.

At this point, it should be noted that all parts described above, viewed individually and in any combination, in particular the details shown in the drawings, are claimed as essential to the invention. Modifications to this are familiar to the person skilled in the art.

List of reference symbols:

1

authentication system

10

vehicle

11

vehicle receiving device

12

vehicle locking device

13

vehicle transmitter

14

vehicle computing device; decoding device

15

vehicle storage device

20

vehicle key

21

key computing device

22

key storage device

23

key transmitter

24

key synchronization device

30

key data sequence

31

key data signal

40

confirmation record

41

confirmation data signal

42

length of the confirmation data sequence

43

spread confirmation data signal

44

spreading code

45

confirmation data after spreading

46

confirmation data after decoding

47

power density of the confirmation data signal

50

request signal

60

background noise signal

61

power density of the noise floor

70

synchronization data

80

release signal

XOR

XOR operation

S1-S6

procedural steps

90

wake-up signal

91

confirmation signal

92

request signal

93

first synchronization signal

94

second synchronization signal

95

third synchronization signal

96

key data signal

t1-t7

points in time

Sync1

synchronization interval

Sync2

synchronization interval

Claims (19)

Key device (20), in particular for a vehicle (10), comprising: a key transmitting device (23) which is designed to: - send a key data signal (31), in particular to the vehicle (10), wherein the key data signal (31) encodes a key data sequence (30); and - send a confirmation data signal (41), in particular to the vehicle (10), wherein the confirmation data signal (41) encodes a confirmation data set (40), wherein a key computing device (21) which is designed to generate the confirmation data signal (41) using a spreading technique, characterized in that a spreading code (44) is selected such that the power density (47) of the confirmation data signal (41) at a measuring distance from the key transmitting device (23) is lower than the noise power density (61). Key device (20) according to claim 1 , characterized in that the key transmitting device (23) is designed to generate the confirmation data signal (41) by bit-by-bit coding, in particular by means of an XOR operation (XOR), of the confirmation data set (40) with a spreading code (44). Key device (20) according to one of the preceding claims, characterized by : a key synchronization device (24), wherein the key computing device (21) is designed to generate the confirmation data signal (41) using the key synchronization device (24). Key device (20) according to one of the preceding claims, in particular claim 3 , characterized in that the key transmitting device (23) is designed to transmit synchronization data (94), in particular to a/the vehicle (10), wherein the synchronization data (94) can be used to determine a distance between the key device (20) and a/the vehicle (10). Key device (20) according to one of the preceding claims, characterized in that the measuring distance from the key transmitting device (23) is less than 300 cm, preferably less than 100 cm, wherein the power density within the measuring distance is lower than the, in particular thermal, noise power density (61). Key device (20) according to one of the preceding claims, characterized in that the confirmation data record (40) has a length (42) less than or equal to 128 bits, in particular less than or equal to 64 bits, preferably exactly 1 bit. Key device (20) according to one of the preceding claims, characterized in that a baud rate and a chip rate are assigned to the confirmation data signal (41), wherein the ratio of chip rate and baud rate indicates a spreading factor which is in particular greater than 10 ³ , preferably greater than 10 ⁵ . Authentication device (10), in particular for a vehicle (10), in particular for a key device (20) according to one of the preceding claims, comprising: - a receiving device (11) for receiving o a key data signal (31), wherein the key data signal (31) encodes a key data sequence (30); and o a confirmation data signal (41), wherein the confirmation data signal (40) encodes a confirmation data set (41); - a blocking device (12) which is designed to generate an enable signal (80) when the confirmation data set (40) and the key data sequence (30) are validated by the blocking device (12), wherein a decoding device (14) which is designed to recover the confirmation data set (40) from the confirmation data signal (41) using a spreading technique, characterized in that a spreading code (44) is selected such that the power density (47) of the confirmation data signal (41) at a measuring distance from the key transmitting device (23) is lower than the noise power density (61). Authentication facility after claim 8 , characterized in that the decoding device (14) is designed to restore the confirmation data set (40) by bit-by-bit decoding, in particular by means of an XOR operation (XOR), of the confirmation data signal (41) with a spreading code (44). Authentication facility after claim 8 or 9 , characterized in that the decoding device (14) is designed to restore the confirmation data set (40) using synchronization data (70) associated with the confirmation data signal (41). Authentication system (1), in particular for a vehicle (10), comprising: - a key device (20) according to one of the Claims 1 until 7 ; - an authentication device (10) according to one of the Claims 8 until 10 , characterized by , that the key device (20) and the authentication device (10) are designed to use a common spreading code (44). Authentication system (1) according to claim 1 , characterized by a/the decoding device (14) which is designed to synchronize the authentication device (10) with the key device (20) with regard to the spreading code (44). Method for releasing a vehicle (10), comprising the following steps: - generating (S1) a confirmation data signal (41) from a confirmation data sequence (40) using a spreading code (44); - sending (S2) the confirmation data signal (41) and a key data signal (31) which encodes a key data sequence (30); - receiving (S3) the confirmation data signal (41) and the key data signal (31); - restoring (S4) the confirmation data sequence (40) from the confirmation data signal (41) using the spreading code (44); - validating (S5) the confirmation data sequence (40) and the key data sequence (30); - releasing (S6) a vehicle (10) when the confirmation data sequence (40) and the key data sequence (30) are validated, characterized in that a spreading code (44) is selected such that the power density (47) of the confirmation data signal (41) at a measuring distance from the key transmitting device (23) is lower than the noise power density (61). procedure according to claim 13 , characterized in that the validation (S6) comprises comparing the key data sequence (30) with a validation code (32). Method according to one of the Claims 13 or 14 , characterized in that the restoring (S4) comprises a correlation of the received confirmation data signal (41) with the spreading code (44). Method according to one of the Claims 13 until 15 , characterized in that the restoring (S4) comprises synchronizing with respect to the spreading code (44). Method according to one of the Claims 13 until 16 , especially after claim 16 , characterized in that synchronization is carried out using a fixed synchronization interval. Method according to one of the Claims 13 until 16 , especially after claim 17 , characterized by a distance measurement, wherein the distance measurement is carried out using a/the synchronization. Computer-readable storage medium containing instructions that cause (at least) one processor to perform a method according to one of the Claims 13 - 18 to implement when the instructions are executed by the processor.

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