DE102023000480A1 - Charging point, quantum network, method and vehicle for quantum cryptographic key transmission - Google Patents

Abstract

The invention relates to a charging point (14, 15) designed to charge the drive battery of a vehicle (20, 30) via a charging cable (50), which is optically coupled to a service station (13) via a fiber optic quantum connection (17) designed for a quantum cryptographic key exchange and which has a fiber optic branch (51) optically coupled to the fiber optic quantum connection (17). The fiber optic branch (51) is designed for optical coupling to the vehicle (20, 30), wherein the service station (13) is designed as a trustworthy node and is designed for the quantum cryptographic key exchange with at least one further trustworthy node (11, 12) via a quantum connection (16, 17).
The invention further relates to a quantum network (10) for quantum cryptographic key transmission to a vehicle (20, 30), a method for quantum cryptographic key transmission via such a quantum network (10) and a vehicle (20, 30) which can be coupled to a charging point (14, 15) for quantum cryptographic key transmission.

Description

The invention relates to a charging point for charging the drive battery of a vehicle according to the preamble of claim 1. The invention further relates to a quantum network for a quantum cryptographic key exchange with a vehicle according to the preamble of claim 4. Furthermore, the invention relates to a vehicle according to the preamble of claim 6 and a method for quantum cryptographic key transmission according to the preamble of claim 9.

Modern vehicles are increasingly dependent on secure, particularly confidential communication, whether to transmit messages from vehicle occupants or to exchange operational data between the vehicle and a central server, for example that of the vehicle manufacturer. Vehicles move in a communication infrastructure that is inherently considered insecure and untrustworthy, for example in a mobile data network or in a public WLAN (Wide Local Area Network).

To secure communication, secret cryptographic keys agreed between a vehicle and its respective communication partner are used to encrypt messages or data symmetrically on both sides in a simple and efficient manner. To counteract the risk of eavesdropping, such cryptographic keys must be changed regularly. It is also essential to ensure that such keys are not themselves intercepted when they are transmitted to a vehicle, thereby compromising all communication based on them.

Quantum key distribution (QKD) methods are known as a method for exchanging provably secret cryptographic keys between two participants who exchange photons or photon pairs via an optical connection and reconstruct cryptographic keys based on their quantum mechanical properties.

From the document CN108696353A A method and a system for quantum key distribution as well as a service station are known. A quantum key is used as a data set, which is encrypted and transmitted using an encryption technique that is not based on quantum encryption. This expands the application area of quantum keys.

The invention is based on the object of specifying an improved charging point for charging a drive battery of a vehicle, which enables a quantum cryptographic transmission of keys to a vehicle. This object is achieved according to the invention with a charging point with the features of claim 1.

The invention is also based on the object of specifying an improved quantum network for the quantum cryptographic transmission of keys to a vehicle. This object is achieved according to the invention with a quantum network having the features of claim 4.

The invention is also based on the object of specifying an improved vehicle that is set up for quantum cryptographic reception of keys. This object is achieved according to the invention with a vehicle having the features of claim 6.

The invention is also based on the object of specifying an improved method for the quantum cryptographic transmission of keys to a vehicle. This object is achieved according to the invention with a method having the features of claim 9.

Advantageous embodiments of the invention are the subject of the subclaims.

According to a first aspect of the invention, a charging point which is set up to charge the drive battery of a vehicle, preferably an electric vehicle, which can be connected to this charging point via a charging cable, is optically coupled to a service station via a fiber optic quantum connection and has a fiber optic branch which is optically coupled or connected to the fiber optic quantum connection.

A fiber optic branch is connected to an assigned charging point via a point-to-point fiber optic connection. The fiber optic branch can be connected to a vehicle via the assigned charging point using a fiber optic connection (i.e. can be optically coupled). Preferably, such a fiber optic connection between the charging point and the vehicle is integrated into the charging cable.

Here and in the following, a fiber optic branch is to be understood as a branching point of the fiber optic quantum connection emanating from the service station and also the fiber optic connection that continues from this branching point to the respective assigned charging point, which is further set up for optical coupling with a vehicle.

A quantum connection is understood here and in the following as an optical connection that is set up and suitable for quantum cryptographic transmission or for the quantum cryptographic exchange of cryptographic keys. Such methods, also known as quantum key distribution (QKD), can be based on the distribution of individual photons whose quantum mechanical properties are known or measurable, or on the distribution of photon pairs with quantum mechanically entangled states. QKD protocols are known, for example the Ekert protocol or the BB84 protocol, which enable two participants to agree on a cryptographic key based on observable quantum mechanical properties of the exchanged photons and additional information exchanged over a communication channel that is not particularly secure against eavesdropping. The cryptographic security of such exchanged keys is based on the fact that unauthorized eavesdropping on the QKD protocol changes the quantum mechanical properties of the photons in such a way that this can be detected by the participants.

A quantum link can be formed by a free optical path through air or vacuum as an over-the-air (OTA) quantum link, for example between a stationary terrestrial station and a satellite. Alternatively, a quantum link can be formed by photon transmission in an optical fiber as a fiber-optic quantum link.

The fiber optic branch optically connected to the fiber optic quantum connection between the service station and the charging point is set up for optical coupling with the vehicle, whose drive battery can be charged via the charging cable.

The service station is designed as a node that is trustworthy in the cryptographic sense. A trustworthy node is understood here and in the following as a node that cannot be considered cryptographically compromised. Even if messages are available in plain text on such a trustworthy node through the implementation of cryptographic protocols, it can be assumed that an attacker cannot gain access to such messages, for example through physical access restrictions.

The service station is also set up for quantum cryptographic key exchange with at least one other trusted node via a quantum connection. For example, the service station can be connected to a satellite via an OTA quantum connection. However, it is also possible for the service station to be connected to another trusted node via a fiber optic quantum connection.

One advantage of the invention is that during the time that a vehicle is connected to such a charging point for electrically charging its drive battery, a quantum cryptographic and thus extremely secure connection for transmitting secret cryptographic keys to the vehicle also exists and can be used. Using such secret keys, the vehicle can then exchange messages in a secure manner, even in a potentially vulnerable environment, for example when communicating via a mobile data network. The secure data exchange can be provided both for operational functions of the vehicle, for example for authenticated software updates, and for communication between vehicle occupants.

Keys exchanged securely in this way can also be used for particularly simple symmetric encryption methods without jeopardizing the confidentiality of the transmitted messages. This can also improve the efficiency of encryption in the vehicle.

In one embodiment, an absorption bandpass filter is optically integrated into the fiber optic branch, which allows photons with a wavelength within a passband to pass through and absorbs photons with a wavelength outside the passband. Preferably, the passband of a charging point is selected so that it does not overlap with the passband of any other charging point that is coupled to the same service station.

This means that different charging points can be supplied with photons of different wavelengths from a service station. Only those photons whose wavelength lies in the passband of the respective absorption bandpass filter of the fiber optic branch are transmitted from a charging point to the vehicle connected to it. All other photons (intended for vehicles at other charging points in the same service station) are absorbed as they travel along this fiber optic branch.

An advantage of this design is that not every charging point has to be connected to the service station via a separate fiber optic cable, but in principle all charging points can be connected to the service station via a single fiber optic cable. This can significantly reduce the installation effort.

In one embodiment, the fiber optic branch is integrated into the charging cable and can be connected to the vehicle via a single plug. This makes connecting a vehicle to such a charging point particularly simple and reliable.

According to a second aspect of the invention, a quantum network set up for a quantum cryptographic key exchange between at least one first participant and at least one vehicle comprises at least two trustworthy nodes, wherein two trustworthy nodes are optically connected to one another via a quantum connection set up for a quantum cryptographic key exchange, and wherein at least one of the trustworthy nodes is designed as a service station with at least one associated charging point according to the first aspect of the invention, which can be optically connected to the vehicle by means of a fiber optic branch.

The advantages of such a quantum network correspond to the advantages of a charging point for a vehicle according to the first aspect of the invention. In particular, keys can be securely transmitted to a vehicle using such a quantum network without the publicly accessible part of a charging infrastructure for electric vehicles having to be extensively protected, since a compromise, for example when an attacker intercepts an optical signal that is extracted from the fiber optic branch of a publicly accessible charging point, is recognizable to the participants involved in the key exchange.

In one embodiment, the quantum network comprises at least one satellite and at least one service station connected to at least one satellite via an over-the-air (OTA) quantum connection. This means that a quantum cryptographic key transfer can also take place between a distant participant, for example the manufacturer of a vehicle or a service company commissioned by it, and a vehicle. In addition, both a satellite and an OTA quantum connection to a satellite have a particularly high level of reliability and security against eavesdropping.

According to a third aspect of the invention, a vehicle comprising a central vehicle computer can be electrically and optically coupled to a charging point according to the first aspect of the invention, wherein the central vehicle computer is set up for the reconstruction of a quantum cryptographic key transmitted via the fiber optic branch from the charging point. The advantages of such a vehicle correspond to the advantages of a charging point according to the first aspect of the invention. In particular, such a vehicle can communicate very securely with the quantum cryptographic keys obtained at a charging point even in potentially unsafe communication environments, for example while moving in the coverage area of a mobile network.

In one embodiment, a vehicle comprises a single photon detector that is set up for wavelength-selective detection of photons fed into the vehicle via a charging point with a wavelength that can be set depending on the charging point. This makes it possible to supply vehicles connected to different charging points of the same service station with photons of a wavelength that is each matched to the charging point via a single fiber optic quantum connection. This can reduce the installation effort for connecting a plurality of charging points to a service station.

In one embodiment, a vehicle comprises a memory for securely storing at least one cryptographic key transmitted quantum-cryptographically via a charging point. This allows at least one, preferably a large number of cryptographic keys to be transmitted to the vehicle during the charging process and stored in the memory for later use. The supply of quantum-cryptographically transmitted keys can thus take place at longer time intervals. A network of charging points according to the first aspect of the invention can also be designed to be correspondingly thinner.

In a method for quantum cryptographic key transmission from a first participant to a vehicle, according to a fourth aspect of the invention, the vehicle is connected to the fiber optic branch of a charging point according to the first aspect of the invention, which is connected to the first participant via a quantum network set up for quantum cryptographic key transmission, which comprises at least one service station assigned to the charging point.

The vehicle identifies itself to this service station (assigned to its charging point) via a conventional connection that does not lead to quantum cryptographic key transfer. transmission, for example via a conventional wired Internet connection or a mobile data network.

The service station transmits the identity of each vehicle connected to a charging point to the first participant via a conventional connection. This conventional connection can be made, for example, via a satellite, which is also used for quantum cryptographic key transmission, but using a radio connection instead of the optical OTA quantum connection.

For each vehicle that is assigned to the service station by being connected to one of its charging points at least optically via the fiber optic branch, the first participant transmits a cryptographic key via the quantum network, for example by generating single photons with polarizations according to an agreed polarization basis or by generating photon pairs with entangled polarization states. Furthermore, the first participant transmits the assignment of a cryptographic key to a vehicle to the service station via a conventional connection, for example via a satellite-switched radio connection.

The service station transmits a cryptographic key intended for a vehicle to at least the charging point to which the vehicle is connected via the fiber optic branch.

The advantages of such a method correspond to the advantages of a charging point according to the first aspect of the invention. In particular, the method enables the transmission of secure cryptographic keys using a simple charging infrastructure, with special security precautions only being required with regard to the service stations, but not with regard to the charging points with public access.

In one embodiment of the method, photons with a wavelength are generated for the quantum cryptographic key transmission of a cryptographic key intended for a vehicle, which is determined depending on the charging point to which the vehicle was connected via the fiber optic branch. By using photons with different wavelengths depending on the charging point, it is possible to connect several or even all charging points of a service station to it via a single fiber optic quantum connection. This can reduce the installation effort compared to a solution in which each charging point is connected to the service station via its own fiber optic quantum connection.

In one embodiment of the method, the number of remaining unused cryptographic keys is determined for a vehicle and, depending on this, a need for the quantum cryptographic transmission of new cryptographic keys is determined. Depending on this need, a hint to find a charging point is presented in the vehicle, for example via a display of an infotainment unit.

An advantage of this embodiment is that new cryptographic keys can be obtained in good time using the particularly secure quantum cryptographic method, in particular in connection with an electrical charging of the vehicle battery that is required anyway and thus without additional time expenditure.

In one embodiment of the method, at least one suggested route for the vehicle is determined in such a way that an electrical supply and also a supply of at least one cryptographic key is possible at at least one charging point along the determined suggested route. This means that cryptographic keys can be provided for the vehicle without additional time expenditure during electrical charging.

Embodiments of the invention are explained in more detail below with reference to drawings.

• 1 schematisch ein Ende-zu-Ende Quantennetzwerk zum Austausch kryptographischer Schlüssel an einem Ladepunkt und
• 2 eine Mehrzahl von Fahrtroutenvorschlägen eines Routenplanungssystems.

Showing:

• 1 schematically an end-to-end quantum network for exchanging cryptographic keys at a charging point and
• 2 a number of route suggestions from a route planning system.

Corresponding parts are provided with the same reference numerals in all figures.

1 shows schematically a quantum network 10 for the secure exchange of cryptographic keys between a first participant A and a second participant B. The quantum network 10 enables a consistently quantum cryptographically secured exchange of keys from one participant A, B to the other participant B, A and is therefore also referred to below as an end-to-end quantum network 10.

In the present case, at least one cryptographic key is sent from the first participant A to the second participant B, but the end-to-end quantum network 10 can also be set up for a transmission of cryptographic keys or other messages in the opposite direction.

The first participant A is assumed to be stationary in this case, but can also be mobile. For example, the first participant A can be a central server of a vehicle manufacturer from which software updates are distributed. The participant B is assigned to a first vehicle 20 and is therefore mobile. Messages or data intended for the participant B are decrypted in a central vehicle computer 21 of the first vehicle 20 and can optionally also be displayed via one or more display devices (not shown in detail) (for example via a display of an infotainment unit).

In a normal operating mode, in particular while the second participant B is on the move, the participants A, B exchange messages or data via a conventional mobile connection 400 which is in principle not trustworthy and which is mediated, for example, via a cellular network. The confidentiality of the data or messages is only ensured by using a secret cryptographic key known only to the participants A, B. Such keys cannot therefore be transmitted via a network which, like the conventional mobile connection 400, is considered to be potentially compromised.

The invention proposes an end-to-end quantum network 10 for the exchange of cryptographic keys, the structure and functioning of which is explained in more detail below.

The use of quantum connections or quantum networks for the optical transmission of a random number common to two communicating participants A, B and known only to them is known as quantum key exchange (Quantum Key Distribution QKD) in various embodiments from the prior art, for example as the BB84 protocol or as the Ekert protocol.

These methods are based on photons being exchanged optically between participants A and B. Bit values are assigned to quantum mechanical characteristics of the photons (for example a polarization position). By comparing detection results with regard to these quantum mechanical characteristics via a communication channel, which only has to be forgery-proof but not tap-proof, participants A and B can determine validly transmitted bit values. The tap-proof nature of such methods is based on the fact that the determined quantum mechanical characteristics of the photons are changed during tap-tapping and that these changes are recognized by comparing the detection results between participants A and B. The bit values assigned to such "tapped" photons are subsequently ignored by the receiving participant B.

Based on the validly transmitted bit values, a cryptographic key can be reconstructed that is only known to the two participants A and B. This means that encrypted messages can be considered confidential even if they are sent over a network that is fundamentally vulnerable.

In principle, any direct optical path along which the transmitted photons experience sufficiently weak attenuation can be used to transmit the photons. Direct transmission is possible both via optical fibers and through air or in a vacuum (over-the-air OTA). However, direct optical transmission to a mobile or moving receiver such as a vehicle 20 is technically impossible or impractical.

The invention proposes to use an end-to-end quantum network 10 instead of a direct optical connection between the participants A and B, in which an optical signal received from a preceding trusted node 11 to 15 is amplified in trusted nodes 11 to 15 and transmitted as an amplified signal to a subsequent trusted node 11 to 15.

In the topology of the end-to-end quantum network 10, neighboring trusted nodes 11 to 15 exchange photons and can thus determine whether a message transmitted by a preceding trusted node 11 to 15 has been intercepted by an attacker. The trustworthiness (i.e. the non-compromiseability) of a trusted node 11 to 15 can be ensured by various measures known from the state of the art, for example by restricting physical access options.

Thus, a connection between participants A, B mediated via an end-to-end quantum network 10 can be assigned the same cryptographic security as the direct exchange of photons or entangled photon states.

In the present embodiment, the first participant A exchanges photons from a trustworthy node designed as a terrestrial station 12 via an OTA quantum connection 16 with a trustworthy node designed as a satellite 11. In the satellite 11, a received message is transmitted via a further OTA quantum connection 16 in photons, which are transmitted to a service station 13, which also represents a trustworthy node.

The service station 13 is assigned at least one, in this case several, charging points 14, 15, which are set up to charge vehicles 20, 30 and are also designed as trusted nodes. The charging points 14, 15 are connected to the service station 13 via fiber optic quantum connections 17. For this purpose, a fiber optic cable leading away from the service station 13 is divided into fiber optic branches 51, so that each of the charging points 14, 15 is assigned a fiber optic branch 51, which establishes a quantum connection 17 between the service station 13 and the respective charging point 14, 15.

For charging, the vehicles 20, 30 are connected to a charging point 14, 15 via a charging cable 50 known from the prior art. Parallel to the charging cable 50 and preferably integrated into this charging cable 50 is a 1 not shown in detail, which connects the vehicle 20, 30 with the associated fiber optic branch 51 and thus a 1 only schematically shown quantum connection 17 between the charging point 14, 15 and a central vehicle computer 21, 31 of the respective vehicle 20, 30.

By means of the optical fiber guided from the fiber optic branch 51 to the charging point 14, 15, the optical signal guided from the service station 13 to an associated charging point 14, 15 is fed into a vehicle 20, 30 in a manner explained in more detail below, i.e.: a direct optical connection mediated via fiber optic without intermediate optical-electrical converters is established between the service station 13, 14 and the vehicle 20, 30.

In an embodiment illustrated with reference to the first vehicle 20, an absorption bandpass filter 52 is incorporated into the glass fiber connecting the first charging point 14 to the associated glass fiber branch 51, which allows photons with a wavelength A lying in the passband between λ ₁ ≤ λ ≤ λ ₂ to pass through and absorbs photons of other wavelengths λ < λ ₁ , λ > λ ₂ so that the latter are not transmitted to the vehicle 20.

In an embodiment illustrated using a further vehicle 30, a single photon detector 32 is arranged on the vehicle side between the end point of a fiber optic cable integrated into the charging cable 50 for connection between the associated fiber optic branch 51 and the central vehicle computer 31, the mode of operation of which will be explained below.

The quantum connections 16, 17 can be used to transmit photons or pairs of entangled photon states whose quantum mechanical properties are determined. However, it is also possible to transmit messages via these quantum connections 16, 17 in a conventional optical manner, i.e. via an optical signal encoded according to a line code, so that these quantum connections 16, 17 always also provide the additional possibility of conventional connections 40.

Such conventional connections 40, for example those mediated via line codes, can be provided both via fiber optic cables and wirelessly in the free optical path. Of course, however, the transmission of a message along a conventional connection 40 between two trustworthy nodes 11 to 15 is not secure against eavesdropping, unlike the quantum cryptographic transmission of keys.

In the following, embodiments of methods for the secure transmission of cryptographic keys from the first participant A via the end-to-end quantum network 10, which is formed from the quantum connections 16, 17 and the trusted nodes 11 to 15, are explained.

A first embodiment will be explained using the first vehicle 20, the drive battery of which is to be charged at the first charging point 14. When the charging cable 50 is electrically connected to the first vehicle 20, the fiber optic branch 51 is simultaneously optically connected to a photon receiving and transmitting device (not shown in detail) of the first vehicle 20. For this purpose, a fiber optic connected to the fiber optic branch 51 can be integrated into the charging cable 50 or designed as a separate cable. For example, a fiber optic plug is integrated into the charging plug of the charging cable 50, which is optically coupled to a fiber optic socket on the first vehicle 20 when plugged in.

The photon receiving and transmitting device is coupled to the central vehicle computer 21 and in this combination is set up to exchange photons with the first charging point 14 via the fiber optic branch 51, with regard to to verify their quantum mechanical coherence (that is: to check whether a received photon has been read out by an attacker without authorization) and to reconstruct a cryptographic key transmitted with the photons. In this way, a transmission chain is established from the first participant A to the first vehicle 20, which exclusively includes secure quantum connections 16, 17 and trustworthy nodes 11 to 15.

Since the first charging point 14 is also designed as a trustworthy node and the connection between it and the first vehicle 20 is designed as a fiber optic quantum connection 17, the secure key transmission cannot be compromised even in the event of an attack on the first charging point 14 or on the fiber optic branch 51, because a key intercepted by an attacker is recognized as compromised due to the loss of quantum mechanical coherence and is discarded.

In addition, the photon receiving and transmitting device provides the functions of a conventional optical-electrical modulator/demodulator and can thus exchange messages with the subscriber A via a conventional connection 40, which runs along the glass fibers and direct optical paths used for the quantum connections 16, 17, but which does not use quantum mechanical detection methods, but rather conventionally modulated optical signals.

When the quantum connection 17 is established along the fiber optic branch 51, the central vehicle computer 21 informs the first participant A that it is ready to receive cryptographic keys. This message is encrypted with a cryptographic key that has already been agreed upon and exchanged between the participants A, B.

The first vehicle 20 identifies itself to the first charging point 14 by means of an identifier that is transmitted via the conventional connection 40 (i.e. not secured by quantum cryptography). Such an identifier can, for example, be a character string that is permanently assigned to the first vehicle 20 in the form of a vehicle identification number (VIN). However, a temporarily assigned identifier in the form of a one-time assigned token is also possible.

In the same way as the first vehicle 20, additional vehicles 30 can also identify themselves at another charging point 15, which is assigned to the same service station 13 as the first charging point 14. The service station 13 records which vehicle 20, 30 is connected to which charging point 14, 15 and transmits this assignment to the first participant A. This transmission takes place along the direct optical path between the satellite 11 and the service station 13 or the terrestrial station 12 of the participant A, but without using quantum cryptographic encryption.

After participant A is informed that participant B is at the first charging point 14, he begins to send at least one key to the first charging point 14. A key is sent as a packet or packet sequence of photons (or entangled photon states) via the OTA quantum connections 16 and the satellite 11 connected in between to the service station 13. In parallel, the assignment of the photon packet transmitted in each case to a charging point 14, 15 connected to the service station 13 is transmitted via the conventional connection 40 via the satellite 11 to the service station 13. The exchange of the polarization filter bases used for the key transmission between the terrestrial station 12 and the service station 13 also takes place via this conventional connection 40.

The service station 13 generates new photons according to the photons received from the satellite 11 and assigns them to the charging points 14, 15 that were specified by the participant A as the destination.

In a particularly simple, in 1 In an embodiment not shown, this assignment can be made by laying a fiber optic quantum connection 17 between the service station 13 and each charging point 14, 15 and the service station 13 coupling newly generated photons exclusively into the fiber optic connection that leads to the charging point 14, 15 for which the cryptographic key is intended. A disadvantage of this embodiment is that fiber optic connections must be laid multiple times over at least part of the distance between the service station 13 and the charging points 14, 15.

To remedy this disadvantage, another, in 1 In the embodiment shown, the entirety of all charging points 14, 15 can be connected to the associated service station 13 via a single common fiber optic quantum connection 17. In this embodiment, the assignment of the charging point 14, 15 designated as the receiver is carried out via the wavelength of the photons newly generated by the service station 13.

For keys intended for transmission to the first charging point 14, Photons of a first wavelength λ ₁ are generated, and for keys intended for transmission to a further charging point 15, photons of a further, different wavelength λ ₂ ≠ λ ₁ .

To select the photons with the first wavelength λ ₁ intended for a first charging point 14, an absorption bandpass filter 52 can be installed in its fiber optic branch 51 (i.e. in the fiber optic that connects the first charging point 14 to the fiber optic branch 51), which allows these photons to pass through unhindered (i.e. coupled into the connected first vehicle 20). Photons of a different wavelength, for example photons of the second wavelength λ ₂ intended for the further charging point 15, are absorbed in the absorption bandpass filter 52.

The photon receiving and transmitting device of the further vehicle 30 ignores these missing photons for the key reconstruction in the same way as photons whose polarization basis differs between the first and second participants A, B (i.e. which were intercepted). A key sent by the first participant A is reconstructed using only the photons that were received with the correct polarization basis at the intended charging point 14, 15.

In an alternative embodiment, illustrated using the additional charging point 15, the absorption bandpass filter 52 is omitted and instead a single photon detector 32 with an adjustable detection frequency is arranged in the additional vehicle 30 connected there to receive the optical signal coupled in via the fiber optic branch 51. Such single photon detectors 32 are known, for example, from the publication H. Li et al., “Multispectral superconducting nanowire single photon detector,” Optics express, vol. 27, no. 4, pp. 4727-4733, 2019, doi: 10.1364/OE.27.004727 known.

The conventional connection 40 is used to inform the other vehicle 30 of the wavelength (or color) of the photons intended for the other charging point 15. The single photon detector 32 is set according to this wavelength and only photons of this wavelength are detected. This can reduce the number of unsuccessful transmission attempts for photons (due to absorption in an absorption bandpass filter 52).

A further advantage of this embodiment is that even in the event of a successful eavesdropping attempt at a charging point 14, 15 or at a connection from the service station 13 thereto, only a portion of the vehicles 20, 30 supplied with keys from the service station 13 need be warned of their potential compromise if the eavesdropping was limited to a particular wavelength.

The time required to charge the drive battery at a charging point 14, 15 is typically sufficient for the quantum cryptographically secured transmission of a large number of keys and it will prove useful to store these keys on a central vehicle computer 21, 31 assigned to the central vehicle computer 21, 31 in 1 to store in a memory not shown in detail.

In an advantageous embodiment, the central vehicle computer 21, 31 can issue a notification via a display device indicating that a special charging point 14, 15 set up for quantum cryptographically secure key transmission should be visited if the number of unused keys falls below a predetermined minimum number. Such a notification can be given, for example, via the display of an infotainment unit that can be used for vehicle navigation.

It is also possible to take the location of such charging points 14, 15 into account when planning the route, as shown schematically in 2 shown. For the route guidance from a starting point S to a destination Z, if the acquisition of new cryptographic keys is required, a first route suggestion R1 is preferably selected, along which there is at least one charging point 14, 15 that is set up for quantum-cryptographically secure key transmission. In contrast, a second route suggestion R2 with a conventional charging station L and a third route suggestion R3 without any charging option are given less priority, although they offer a shorter route.

List of reference symbols

10

Quantum network, end-to-end quantum network

11

Satellite, trusted node

12

terrestrial station, trusted node

13

Service station, trusted node

14

first loading point, trusted node

15

additional charging point, trusted node

16

Over-the-Air (OTA) quantum connection

17

Fiber optic - quantum connection

20

first vehicle

30

second, additional vehicle

21, 31

central vehicle computer

32

Single Photon Detector

40

conventional connection

50

Charging cable

51

Fiber optic branch

52

Absorption bandpass filter

400

conventional mobile connection

AWAY

first, second participant

R1, R2, R3

first to third route suggestion

L

conventional charging station

S

Starting point

Z

Destination

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• CN108696353A [0005]

Cited non-patent literature

• H. Li et al., “Multispectral superconducting nanowire single photon detector,” Optics express, vol. 27, no. 4, pp. 4727-4733, 2019, doi: 10.1364/OE.27.004727 [0079]

Claims (12)

Charging point (14, 15) set up for charging the drive battery of a vehicle (20, 30) via a charging cable (50), characterized in that the charging point (14, 15) is optically coupled to a service station (13) via a fiber optic quantum connection (17) set up for a quantum cryptographic key exchange and has a fiber optic branch (51) optically coupled to the fiber optic quantum connection (17) and set up for optical coupling to the vehicle (20, 30), wherein the service station (13) is designed as a trustworthy node and is set up for the quantum cryptographic key exchange with at least one further trustworthy node (11, 12) via a quantum connection (16, 17). Charging point (14, 15) after Claim 1 , characterized in that an absorption bandpass filter (52) is optically integrated into the glass fiber branch (51), which allows photons with a wavelength within a passband to pass and absorbs photons with a wavelength outside the passband, wherein the passband of a charging point (14, 15) is selected so as not to overlap with the passband of any other charging point (14, 15) coupled to the same service station (13). Charging point (14, 15) according to one of the preceding claims, characterized in that the fiber optic branch (51) is integrated into the charging cable (50) and can be connected together with the latter to the vehicle (20, 30) via a single plug. Quantum network (10) set up for a quantum cryptographic key exchange between at least one first participant (A) and at least one vehicle (20, 30), characterized in that the quantum network (10) comprises at least two trustworthy nodes (11 to 15), wherein two trustworthy nodes (11 to 15) are optically connected to one another via a quantum connection (16, 17) set up for a quantum cryptographic key exchange, and wherein at least one of the trustworthy nodes (11 to 15) is designed as a service station (13) with at least one associated charging point (14, 15) according to one of the preceding claims, which can be optically connected to the vehicle (20, 30) by means of a respective fiber optic branch (51). Quantum network (10) according to Claim 4 , characterized in that the quantum network (10) comprises at least one satellite (11) and a service station (13) connected to at least one satellite (11) via an over-the-air (OTA) quantum connection (16). Vehicle (20, 20) comprising a central vehicle computer (21, 31), characterized in that the vehicle (20, 30) is equipped with a charging point (14, 15) according to one of the Claims 1 until 3 can be coupled electrically and optically and that the central vehicle computer (21, 31) is set up for the reconstruction of a cryptographic key transmitted quantum cryptographically via the fiber optic branch (51) from the charging point (14, 15). Vehicle (20, 30) after Claim 6 , characterized in that the vehicle (20, 30) comprises at least one single photon detector (32) which is designed for the wavelength-selective detection of photons fed into the vehicle (20, 30) via a charging point (14, 15) with a wavelength that can be set depending on the charging point (14, 15). Vehicle (20, 30) after Claim 6 or 7 , characterized in that the vehicle (20, 30) has a memory for the secure storage of at least one cryptographic key transmitted quantum cryptographically via a charging point (14, 15). Method for quantum cryptographic key transmission from a first participant (A) to a vehicle (20, 30), characterized in that - the vehicle (20, 30) is connected to the fiber optic branch (51) of a charging point (14, 15) according to one of the Claims 1 until 3 which is connected to the first participant (A) via a quantum network (10) set up for quantum cryptographic key transmission, comprising at least one service station (13) assigned to the charging point (14, 15), - the vehicle (20, 30) identifies itself to the service station (13) via a conventional connection (40, 400) not qualified for quantum cryptographic key transmission, - the service station (13) transmits the identities of the vehicles (20, 30) connected via an assigned charging point (14, 15) to the first participant (A) via a conventional connection (40, 400), - the first participant (A) transmits a cryptographic key for each of the vehicles (20, 30) assigned to the service station (13) via the quantum network (10), wherein the first participant (A) assigns the cryptographic key to a vehicle (20, 30) via a conventional connection (40, 400) and - the service station (13) has a cryptographic key intended for a vehicle (20, 30) min at least to the charging point (14, 15) to which the vehicle (20, 30) was connected by means of the fiber optic branch (51). Procedure according to Claim 9 , characterized in that for the quantum cryptographic key transmission of a cryptographic key intended for a vehicle (20, 30), photons are generated with a wavelength which is determined depending on the charging point (14, 15) to which the vehicle (20, 30) was connected by means of the fiber optic branch (51). Procedure according to Claim 9 or 10 , characterized in that a need for the quantum cryptographic transmission of new cryptographic keys is determined on the basis of a number of unused cryptographic keys still remaining for a vehicle (20, 30), and an indication for finding a charging point (14, 15) is presented in the vehicle (20, 30) depending on this need. Procedure according to one of the Claims 9 until 11 , characterized in that at least one travel route suggestion (R1 to R3) for the vehicle (20, 30) is determined in such a way that an electrical supply and a supply with at least one cryptographic key is possible along the travel route suggestion (R1 to R3) at at least one charging point (14, 15).

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