COMMUNICATION DEVICE, RANGE MEASURING DEVICE, AND AUTHENTICATION METHOD IN COMMUNICATION DEVICE

Abstract

Provided are a communication device, a distance measuring device, and an authentication method in the communication device with which confidentiality of communication is improved.　This communication device includes: a sharing processing unit for performing a process for sharing, with other devices, data relating to a first frequency and a second frequency that are used for communication with the other devices; a transmission / reception unit for transmitting and receiving high-frequency signals to and from the other devices; and an authentication unit that authenticates the other devices as legitimate other devices when the authentication unit has received, from the other devices, a high-frequency signal of the first frequency after the transmission / reception unit transmits the high frequency signal of the first frequency to the other devices, and has also received, from the other devices, a high-frequency signal of the second frequency after the transmission / reception unit transmits the high-frequency signal of the second frequency to the other devices.

Description

[Technical field]

[0001] The present invention relates to a communication device, a distance measuring device, and an authentication method in a communication device. [Background technology]

[0002] Conventionally, there has been a distance measuring device including a first device having a first transceiver that transmits a first known signal corresponding to a first carrier frequency and a second known signal corresponding to a second carrier frequency different from the first carrier frequency, and receives a third known signal corresponding to the first carrier frequency and a fourth known signal corresponding to the second carrier frequency; a second device having a second transceiver that transmits the third known signal and the fourth known signal and receives the first and second known signals; and a calculation unit that calculates a distance between the first device and the second device based on the phases of the first to fourth known signals, wherein the first transceiver and the second transceiver perform a total of four transmissions and receptions, that is, one transmission and reception each of the first and third known signals, and one transmission and reception each of the second and fourth known signals (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-128341 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional distance measuring devices can be applied to smart key entry systems for vehicles and provide countermeasures against so-called relay attacks, but the device on the vehicle and the smart key communicate with each other according to a fixed transmission order and transmission frequency that is determined in advance, so the confidentiality of the communication is insufficient. In other words, the countermeasures against relay attacks are insufficient.

[0005] It is therefore an object of the present invention to provide a communication device, a distance measuring device, and an authentication method in a communication device that improves the confidentiality of communication. [Means for solving the problem]

[0006] A communication device of an embodiment of the present invention includes a sharing processing unit that performs processing to share data regarding a first frequency and a second frequency used for communication with another device with the other device, a transceiver unit that transmits and receives a high-frequency signal between the other device and the other device, and an authentication unit that authenticates the other device as a legitimate other device when the transceiver unit transmits a high-frequency signal of the first frequency to the other device and then receives a high-frequency signal of the first frequency from the other device and when the transceiver unit transmits a high-frequency signal of the first frequency to the other device and then receives a high-frequency signal of the second frequency from the other device. Effect of the Invention

[0007] It is possible to provide a communication device, a distance measuring device, and an authentication method in a communication device that improves the confidentiality of communication. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a vehicle 10 and a smart key 20 in which distance measuring devices 100A and 100B of an embodiment are mounted, respectively. [Diagram 2] FIG. 1 illustrates a distance measuring device 100A according to an embodiment. [Diagram 3] FIG. 1 is a diagram showing an example of communication for distance measurement; [Figure 4] FIG. 13 is a diagram showing phase characteristics with respect to frequency F obtained by distance measurement. [Diagram 5] FIG. 13 is a diagram showing an example of communication for distance measurement in the presence of an unauthorized device A. [Figure 6] 13 is a diagram showing the phase characteristics with respect to frequency F obtained by distance measurement in the presence of an unauthorized device A. FIG. [Figure 7]FIG. 11 is a diagram showing an example of table data for adjusting the frequency of a high-frequency signal. [Figure 8] FIG. 11 is a diagram illustrating an example of shared adjustment data. [Figure 9] FIG. 11 is a flowchart showing a sharing process, a frequency setting process, an authentication process, and a distance measurement process under normal conditions. [Figure 10] FIG. 11 is a flowchart showing a sharing process, a frequency setting process, and an authentication process in an abnormal state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a description will be given of embodiments to which a communication device, a distance measuring device, and an authentication method in a communication device of the present invention are applied.

[0010] <Embodiment> 1 is a diagram showing a vehicle 10 and a smart key 20 equipped with distance measuring devices 100A and 100B of an embodiment, respectively. As an example, a configuration will be described in which the distance measuring device 100A is equipped in a smart entry system mounted on the vehicle 10, and the distance measuring device 100B is equipped in the smart key 20 of the vehicle 10. As an example, the distance measuring devices 100A and 100B communicate using BLE (Bluetooth Low Energy (registered trademark)).

[0011] At least one of the distance measuring device 100A of the vehicle 10 and the distance measuring device 100B of the smart key 20 measures the distance between the vehicle 10 and the smart key 20, and the locks on the doors, trunk, etc. of the vehicle 10 are unlocked when the distance measured by the distance measuring device 100A or 100B is an appropriate distance.

[0012] Here, as an example, the distance measuring device 100A of the vehicle 10 performs distance measurement and notifies the distance measuring device 100B of the smart key 20 of the result of the distance measurement. The distance measuring devices 100A and 100B have the same configuration as an example. Therefore, in the following, when there is no need to distinguish between the distance measuring devices 100A and 100B, they will be simply referred to as distance measuring device 100. Of the distance measuring device 100A of the vehicle 10 and the distance measuring device 100B of the smart key 20, the distance measuring device 100B that does not perform distance measurement is an example of another device. Here, as an example, the distance measuring device 100B of the smart key 20 is an example of another device.

[0013] <Configuration of distance measuring device 100A> 2 is a diagram showing a distance measuring device 100A according to an embodiment. As described above, the distance measuring device 100A of the vehicle 10 and the distance measuring device 100B of the smart key 20 have the same configuration. Here, the distance measuring device 100A that performs distance measurement will be described.

[0014] The distance measuring device 100A includes an antenna 101, a transmitting / receiving unit 110, a signal generating unit 120, and an MCU (Micro Computer Unit) 130. The antenna 101 is connected to the transmitting / receiving unit 110.

[0015] The communication device 100S of the embodiment is an apparatus obtained by removing the ranging unit 135 from the ranging device 100A of the embodiment. That is, the communication device 100S includes the antenna 101, the transmitting / receiving unit 110, the signal generating unit 120, and the parts of the MCU 130 other than the ranging unit 135. For this reason, the antenna 101, the transmitting / receiving unit 110, the signal generating unit 120, and the parts of the MCU 130 other than the ranging unit 135 are denoted by the symbol 100S in parentheses.

[0016] The transmitting / receiving unit 110 is connected to the antenna 101, the signal generating unit 120, and the MCU 130. The transmitting / receiving unit 110 has a transmitting circuit including a PA (Power Amplifier) ​​for transmission and the like, a receiving circuit including an LNA (Low Noise Amplifier) ​​for reception and the like, and a switch for switching between the transmitting circuit and the receiving circuit.

[0017] The transmitting / receiving unit 110 transmits a high-frequency signal (continuous wave) output from the signal generating unit 120 to the ranging device 100B via the antenna 101, and receives a high-frequency signal (continuous wave) transmitted from the ranging device 100B via the antenna 101. In addition to transmitting and receiving high-frequency signals, the transmitting / receiving unit 110 transmits and receives data and the like to and from the ranging device 100B using, for example, packet signals of BLE (Bluetooth Low Energy (registered trademark)). For example, the frequency of the high-frequency signal and the packet signal is the 2.4 GHz band. The 2.4 GHz band has multiple channels with different frequencies.

[0018] The signal generating unit 120 has an oscillation circuit 121, a frequency adjustment unit 122, and a multiplication unit 123. The oscillation circuit 121 is an OSC (Oscillator) and oscillates a high-frequency signal (continuous wave) of, for example, 32 MHz. 32 MHz is an example of a fundamental frequency, and is the oscillation frequency of the oscillation circuit 121. The frequency adjustment unit 122 and the multiplication unit 123 are realized by, for example, an IC (Integrated Circuit). The frequency adjustment unit 122 and the multiplication unit 123 are described as blocks of functions realized by the IC.

[0019] The frequency adjustment unit 122 adjusts the frequency of the high-frequency signal oscillated by the oscillation circuit 121. The frequency adjustment unit 122 adjusts the frequency of the high-frequency signal input from the oscillation circuit 121 to a frequency obtained by adding an adjustment amount set by a frequency setting unit 133 of the MCU 130 to the fundamental frequency, and outputs the high-frequency signal with the adjusted frequency to the multiplication unit 123. The frequency adjustment unit 122 adjusts the frequency of the high-frequency signal by changing a parameter corresponding to the electrostatic capacitance of two electrodes of the quartz crystal oscillator.

[0020] Multiplier 123 multiplies the frequency (fundamental frequency+adjustment amount) of the high frequency signal input from frequency adjuster 122, and outputs a high frequency signal having a frequency in the 2.4 GHz band to transmitter / receiver 110. Multiplier 123 multiplies the frequency of the high frequency signal by changing a parameter indicating the frequency magnification.

[0021] The MCU 130 has a main control unit 131, a shared processing unit 132, a frequency setting unit 133, an authentication unit 134, a distance measurement unit 135, and a memory 136. The memory 136 is an example of a storage unit. The MCU 130 is realized by a microcomputer including, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an internal bus. The main control unit 131, the shared processing unit 132, the frequency setting unit 133, the authentication unit 134, and the distance measurement unit 135 are functional blocks showing the functions of a program executed by the MCU 130. The memory 136 is a functional representation of the memory of the MCU 130.

[0022] The main control unit 131 is a processing unit that executes processes other than those executed by the shared processing unit 132, the frequency setting unit 133, the authentication unit 134, and the distance measuring unit 135, and supervises the control process of the MCU 130. In addition, the main control unit 131 controls the operation of the oscillation circuit 121 of the signal generating unit 120.

[0023] The sharing processing unit 132 performs a sharing process for sharing shared adjustment data between the ranging devices 100A and 100B. The shared adjustment data is data that represents rules regarding frequencies used when the ranging devices 100A and 100B transmit high-frequency signals to each other for authentication processing. Details of the shared adjustment data will be described later with reference to FIG. 8. Details of the sharing process will be described later with reference to FIG. 9.

[0024] The frequency setting unit 133 performs a frequency setting process that sets an adjustment amount to be added to the fundamental frequency in the frequency adjustment unit 122 of the signal generation unit 120 based on data regarding the frequency of the high-frequency signal shared between the distance measuring devices 100A and 100B by the sharing process of the sharing processing unit 132.

[0025] When the ranging devices 100A and 100B transmit high-frequency signals to each other for distance measurement, the authentication unit 134 performs an authentication process to authenticate that the communication partner of the ranging device 100A is the ranging device 100B, which is an example of a legitimate other device, based on the relationship between the frequencies of the transmitted and received high-frequency signals. In the authentication process, the authentication unit 134 determines whether the communication partner is the ranging device 100B or a device other than the ranging device 100B (an example of an unauthorized other device). Details of the authentication process will be described later with reference to FIG. 8.

[0026] When authentication is established by the authentication unit 134, the distance measuring unit 135 performs distance measurement to the distance measuring device 100B. As an example, the distance measuring unit 135 performs distance measurement in a ToA (Time Of Arrival) format. The distance measuring unit 135 obtains a relationship between the phase and the frequency based on the phase difference of the high frequency signal received from the distance measuring device 100B, and calculates and outputs the distance from the relationship between the frequency and the phase.

[0027] The memory 136 stores programs and data necessary for the main control unit 131 to execute various processes, and programs and data necessary for the sharing processing unit 132, frequency setting unit 133, authentication unit 134, and ranging unit 135 to execute processes for sharing processing, frequency setting processing, authentication processing, and ranging processing, respectively.

[0028] <Communication for distance measurement> FIG. 3 is a diagram showing an example of communication for distance measurement. In FIG. 3, the time axis is from top to bottom. The distance measuring devices 100A and 100B transmit and receive at mutually determined frequencies. As an example, (1) the distance measuring device 100A transmits a high-frequency signal of frequency F1, and the distance measuring device 100B receives the high-frequency signal of frequency F1 from the distance measuring device 100A. (2) The distance measuring device 100B transmits a high-frequency signal of frequency F1, and the transmitted high-frequency signal is received by the distance measuring device 100A. That is, (1) and (2) transmit and receive high-frequency signals at the same frequency F1. The distance measuring device 100A obtains a phase φ1 of the transmitted and received high-frequency signals at the frequency F1. The phase φ1 corresponds to the remainder when the distance L between the distance measuring devices 100A and 100B is divided by the wavelength λ1 of the frequency F1. That is, L=(n+φ1)×λ1. n is a positive integer. The transmission and reception of (3) and (4) are the same as (1) and (2), except that the frequency is changed to F2.

[0029] FIG. 4 is a diagram showing the characteristics of the phase φ with respect to the frequency F obtained by distance measurement. The distance measuring device 100A repeatedly performs the process described with reference to FIG. 3 to obtain the phase φ1 of the round trip at the frequency F1 between the high frequency signal transmitted at (1) and the high frequency signal received at (2) shown in FIG. 3, and obtain the phase φ2 of the round trip at the frequency F2 between the high frequency signal transmitted at (3) and the high frequency signal received at (4) shown in FIG. 3. Then, the distance measuring device 100A obtains the ratio of the distance L to the speed of light c as the ratio of the phase difference (φ2-φ1) between the phase φ1 at the frequency F1 and the phase φ2 at the frequency F2 to the difference (F2-F1) between the frequencies F1 and F2. That is, L / c=((F2-F1) / (φ2-φ1)). The distance measuring device 100A can obtain the distance L by multiplying the obtained ratio by the speed of light c.

[0030] In addition, while the ranging devices 100A and 100B are performing transmission and reception processing of high frequency signals at frequency F (constant value) as shown in Fig. 3, the phase of the high frequency signal received from the ranging device 100B is approximately constant. The oscillator circuits 121 that the ranging devices 100A and 100B each have variations in offset of natural frequency and variations in oscillation frequency due to temperature characteristics, but the phase of the high frequency signal that the ranging device 100A receives from the ranging device 100B is approximately constant while the ranging device 100A is performing transmission and reception processing of high frequency signals as shown in Fig. 3.

[0031] <Communication when unauthorized device A is present> FIG. 5 is a diagram showing an example of communication for distance measurement when an unauthorized device A is present. The unauthorized device A is typically a communication terminal operated by a person who launches a relay attack to steal the vehicle 10. As in FIG. 3, the distance measuring devices 100A and 100B transmit and receive signals (1) to (3), and the device A receives the high-frequency signal of frequency F2 transmitted from the distance measuring device 100A at (3), and the device A receives the high-frequency signal of frequency F2 transmitted from the device A at (4). The device A receives the high-frequency signal of frequency F2 transmitted from the distance measuring device 100A to the distance measuring device 100B, detects that transmission and reception are being performed at frequency F2, and transmits the high-frequency signal of frequency F2 while impersonating the distance measuring device 100B.

[0032] 6 is a diagram showing the characteristics of phase φ with respect to frequency F obtained by distance measurement when an unauthorized device A is present. When transmitting and receiving (1) to (4) with distance measuring device 100B, the characteristics of phase with respect to frequency F shown by the solid line are obtained, and when the high frequency signal received from device A at timing (4) is used, the characteristics of phase with respect to frequency F shown by the dashed line are obtained. The characteristics of phase with respect to frequency F shown by the dashed line are the characteristics of phase with respect to frequency F obtained from the high frequency signal of frequency F received from device A at timing (4).

[0033] In this way, when the ranging device 100A receives a high-frequency signal from device A different from the ranging device 100B, the phase gradient with respect to frequency in the phase characteristics with respect to frequency F required by the ranging unit 135 changes, causing a phase shift. From this, it can be determined that the ranging device 100A is receiving a high-frequency signal from a device other than the ranging device 100B (here, device A).

[0034] In this way, when ranging device 100A is transmitting and receiving a high-frequency signal with ranging device 100B, if ranging device 100A receives a high-frequency signal from a device other than ranging device 100B (here, device A), changes occur in the phase characteristics with respect to frequency F and the characteristics of the phase change over time, making it possible to determine that ranging device 100A is receiving a high-frequency signal from a device other than ranging device 100B (here, device A).

[0035] Therefore, by actively utilizing the changes that occur in the phase characteristics with respect to frequency F and the temporal change characteristics of the phase, it is possible to determine that ranging device 100A is receiving a high-frequency signal from a device other than ranging device 100B (here, device A).

[0036] Fig. 7 is a diagram showing an example of table data of the frequency adjustment amount of the high frequency signal. The table data shown in Fig. 7 is data in a table format in which the ID (Identifier) ​​of the frequency adjustment amount of the high frequency signal is associated with the adjustment amount. The table data of the frequency adjustment amount of the high frequency signal is stored in the memory 136.

[0037] The frequency adjustment unit 122 reads an adjustment amount from the shared adjustment data in accordance with the rules represented by the common adjustment data stored in the memory 136, adjusts the frequency of the high-frequency signal input from the oscillator circuit 121 to a frequency obtained by adding the read-out adjustment amount to the fundamental frequency, and outputs the high-frequency signal with the adjusted frequency to the multiplication unit 123.

[0038] <Shared Coordination Data> 8 is a diagram showing an example of the common adjustment data. The common adjustment data represents a rule regarding the frequency used when the ranging devices 100A and 100B transmit high-frequency signals to each other for authentication processing, and is an example of data regarding the frequency used by the ranging devices 100A and 100B for communication.

[0039] The shared adjustment data includes data representing an adjustment ID used in the first and second transmission from the ranging device 100A to the ranging device 100B and the first and second transmission from the ranging device 100B to the ranging device 100A. The order of transmission between the ranging devices 100A and 100B is determined in the shared adjustment data such that the ranging device 100A starts transmission, and whichever of the ranging devices 100A and 100B receives the high-frequency signal transmits the high-frequency signal next.

[0040] Although a case will be described here in which high-frequency signals are transmitted and received twice between the ranging devices 100A and 100B, the number of transmissions and receptions may be any number equal to or greater than two. The shared adjustment data includes the order and adjustment IDs for all transmissions and receptions of high-frequency signals between the ranging devices 100A and 100B.

[0041] As an example, the shared adjustment data indicates that the first transmission from the ranging device 100A to the ranging device 100B is performed at a frequency F0 using an adjustment amount f0, and the first transmission from the ranging device 100B to the ranging device 100A is performed at a frequency F0 using an adjustment amount f0. Also, the shared adjustment data indicates that the second transmission from the ranging device 100A to the ranging device 100B is performed at a frequency F0 using an adjustment amount f0, and the second transmission from the ranging device 100B to the ranging device 100A is performed at a frequency F1 using an adjustment amount f1. Here, the frequency F0 is an example of a first frequency, and the adjustment amount f0 is an example of a first adjustment amount. Also, the frequency F1 is an example of a second frequency, and the adjustment amount f1 is an example of a second adjustment amount.

[0042] <Normal processing> 9 is a diagram showing a flowchart showing the sharing process, frequency setting process, authentication process, and ranging process under normal circumstances. The normal circumstances are a state in which a relay attack by device A is not being performed. Here, a process flow under normal circumstances will be described from when ranging devices 100A and 100B perform the sharing process until ranging device 100A performs the ranging process via frequency setting process and authentication process. The communication partner of ranging device 100A under normal circumstances is ranging device 100B, which is another authorized device.

[0043] First, the sharing processing unit 132 of the ranging device 100A performs a sharing process with the sharing processing unit 132 of the ranging device 100B (step S1). The sharing processing unit 132 of the ranging device 100A generates shared adjustment data and transmits it to the ranging device 100B. For example, the ranging device 100A may generate shared adjustment data in advance and store it in the memory 136, and the sharing processing unit 132 may read it from the memory 136 and transmit it to the ranging device 100B. Alternatively, the ranging device 100A may use a random number table or the like to extract an adjustment amount from table data of the adjustment amount of the frequency of the high frequency signal shown in FIG. 7 to generate shared adjustment data and transmit it to the ranging device 100B. The ranging device 100A may transmit the shared adjustment data to the ranging device 100B by, for example, a packet signal. As a result, the ranging device 100B obtains the shared adjustment data and stores it in the memory 136.

[0044] When the distance measuring device 100A finishes the sharing process, it generates a high-frequency signal of frequency F0 using the adjustment amount f0 according to the shared adjustment data as a high-frequency signal for the first transmission (step S2A). More specifically, the frequency adjustment unit 122 of the distance measuring device 100A reads out the adjustment amount f0 according to the rule represented by the shared adjustment data stored in the memory 136, adjusts the frequency of the high-frequency signal input from the oscillation circuit 121 to a frequency (fc+f0) obtained by adding the adjustment amount f0 to the fundamental frequency fc, and outputs the frequency to the multiplication unit 123. The multiplication unit 123 multiplies the frequency (fc+f0) and outputs a high-frequency signal of frequency F0 in the 2.4 GHz band. In this way, a high-frequency signal of frequency F0 is generated as a high-frequency signal for the first transmission.

[0045] After completing the sharing process, the ranging device 100B generates a high-frequency signal of frequency F0 as a high-frequency signal for the first transmission using the adjustment amount f0 according to the shared adjustment data (step S2B). The method of generating the high-frequency signal of frequency F0 is the same as that of the ranging device 100A in step S2A.

[0046] In the first transmission, the distance measuring device 100A transmits the high-frequency signal with the frequency F0 generated in step S2A to the distance measuring device 100B (step S3A).

[0047] The distance measuring device 100B receives the first high frequency signal from the distance measuring device 100A (step S3B).

[0048] In the first transmission, the distance measuring device 100B transmits the high-frequency signal with the frequency F0 generated in step S2B to the distance measuring device 100A (step S4B).

[0049] The distance measuring device 100A receives the first high frequency signal from the distance measuring device 100B (step S4A).

[0050] The distance measuring unit 135 of the distance measuring device 100A calculates the phase gradient with respect to the frequency F based on the phase difference between the high frequency signal of the frequency F0 transmitted in step S3A and the high frequency signal of the frequency F0 received in step S4A (step S5A). The phase gradient with respect to the frequency F calculated by the distance measuring unit 135 is represented by the characteristic representing the phase gradient with respect to the frequency F as shown in FIG.

[0051] The ranging device 100B generates a high-frequency signal of frequency F1 as a high-frequency signal for the second transmission by using the adjustment amount f1 according to the common adjustment data (step S5B). More specifically, the frequency adjuster 122 of the ranging device 100B reads out the adjustment amount f1 according to the rule represented by the common adjustment data stored in the memory 136, adjusts the frequency of the high-frequency signal input from the oscillation circuit 121 to a frequency (fc+f1) obtained by adding the adjustment amount f1 to the fundamental frequency fc, and outputs the adjusted frequency to the multiplier 123. The multiplier 123 multiplies the frequency (fc+f1) to output a high-frequency signal of frequency F1 in the 2.4 GHz band. In this way, the high-frequency signal of frequency F1 is generated as a high-frequency signal for the second transmission.

[0052] In the second transmission, the distance measuring device 100A transmits the high-frequency signal with the frequency F0 generated in step S2A to the distance measuring device 100B (step S6A).

[0053] The distance measuring device 100B receives the second high frequency signal from the distance measuring device 100A (step S6B).

[0054] In the second transmission, the distance measuring device 100B transmits the high-frequency signal with the frequency F1 generated in step S5B to the distance measuring device 100A (step S7B).

[0055] The distance measuring device 100A receives the second high frequency signal from the distance measuring device 100B (step S7A).

[0056] Distance measuring unit 135 of distance measuring device 100A calculates the phase gradient for frequency F based on the phase difference between the high frequency signal of frequency F0 transmitted in step S6A and the high frequency signal of frequency F1 received in step S7A (step S8). Since the phase difference between the transmitted high frequency signal of frequency F0 and the received high frequency signal of frequency F1 is different from the phase difference between the transmitted high frequency signal of frequency F0 and the received high frequency signal of frequency F0 in step S5A, the phase gradient for frequency F calculated in step S8 should be different from the phase gradient for frequency F calculated in step S8.

[0057] The authentication unit 134 of the ranging device 100A judges whether the phase gradient for the frequency F calculated by the ranging unit 135 in step S5A and the phase gradient for the frequency F calculated by the ranging unit 135 in step S8 are shifted by the difference between the frequency F0 and the frequency F1 (step S9). Step S9 is a process for judging whether the communication partner is transmitting a high-frequency signal according to the rule represented by the shared adjustment data. The shared adjustment data is held only by the ranging device 100A and the ranging device 100B, which is a legitimate other device, and is not held by any communication partner other than the ranging device 100B. Such a process of step S9 is a process for authenticating whether the communication partner of the ranging device 100A is the ranging device 100B, which is a legitimate other device.

[0058] For example, theoretical value data representing a theoretical value representing a difference between a theoretical value of a phase gradient with respect to frequency F obtained when a high frequency signal with frequency F0 is transmitted and received, and a theoretical value of a phase gradient with respect to frequency F obtained when a high frequency signal with frequency F0 is transmitted and received, may be calculated and stored in memory 136 of distance measuring device 100A. Then, in step S9, if the difference between the phase gradient with respect to frequency F calculated by distance measuring unit 135 in step S5A and the phase gradient with respect to frequency F calculated by distance measuring unit 135 in step S8 is within ±5% of the theoretical value of the difference represented by the theoretical value data stored in memory 136, authentication unit 134 of distance measuring device 100A may determine that there is a deviation by the amount of the difference between frequency F0 and frequency F1.

[0059] Furthermore, the authentication unit 134 of the distance measuring device 100A may calculate the theoretical value of the difference represented by the theoretical value data in step S9 and use it for the determination in step S9. In this case, it is not necessary to store the theoretical value data in the memory 136 in advance.

[0060] If the authentication unit 134 of the distance measuring device 100A determines that there is a shift corresponding to the difference between the frequency F0 and the frequency F1 (S9: YES), it determines that authentication has been established (step S10Y).

[0061] If the authentication is successful, the ranging device 100A performs a ranging process with the ranging device 100B (step S11). In the ranging process, high-frequency signals are transmitted and received between the ranging devices 100A and 100B at a predetermined frequency, and the ranging unit 135 of the ranging device 100A obtains a phase gradient with respect to frequency F from the phase difference between the high-frequency signal transmitted to the ranging device 100B and the high-frequency signal received from the ranging device 100B, and calculates the distance from the ranging device 100A to the ranging device 100B based on the phase gradient with respect to frequency F.

[0062] As described above, under normal circumstances, the difference in inclination is in accordance with the rules represented by the shared adjustment data, so authentication is established and the ranging device 100A can perform ranging processing with the ranging device 100B, which is another authorized device. As a result, the smart key 20 including the ranging device 100B can unlock the doors, trunk, and the like of the vehicle 10 equipped with the ranging device 100A.

[0063] <Processing in the event of an abnormality> FIG. 10 is a diagram showing a flowchart showing the sharing process, frequency setting process, and authentication process in an abnormal state. An abnormal state is a state in which a relay attack by device A is being performed. Here, a process flow will be described from when ranging devices 100A and 100B perform the sharing process, until a relay attack by device A occurs and ranging device 100A performs the frequency setting process and authentication process. In an abnormal state, authentication is not established, so ranging device 100A does not perform ranging process. In FIG. 10, the same processes as those shown in FIG. 9 are assigned the same step numbers, and their explanations may be omitted.

[0064] First, the sharing processing unit 132 of the distance measuring device 100A performs a sharing process with the sharing processing unit 132 of the distance measuring device 100B (step S1). This is the same as step S1 shown in FIG.

[0065] After completing the sharing process, the ranging device 100A generates a high-frequency signal of frequency F0 using the adjustment amount f0 according to the shared adjustment data as a high-frequency signal for the first transmission (step S2A). Similarly, after completing the sharing process, the ranging device 100B generates a high-frequency signal of frequency F0 using the adjustment amount f0 according to the shared adjustment data as a high-frequency signal for the first transmission (step S2B).

[0066] In the first transmission, the distance measuring device 100A transmits the high-frequency signal with the frequency F0 generated in step S2A to the distance measuring device 100B (step S3A).

[0067] At this time, device A performs a relay attack and receives the high-frequency signal with frequency F0 transmitted by the distance measuring device 100A (step S3C).

[0068] The device A generates a high-frequency signal with a frequency F0, and transmits it to the distance measuring device 100A, disguised as the distance measuring device 100B (step S4C).

[0069] The distance measuring device 100A receives the high frequency signal of frequency F0 transmitted from device A as the first high frequency signal (step S4A). The distance measuring device 100A determines that it has received the high frequency signal of frequency F0 from the distance measuring device 100B.

[0070] The distance measuring unit 135 of the distance measuring device 100A calculates the phase gradient with respect to the frequency F based on the phase difference between the high frequency signal of the frequency F0 transmitted in step S3A and the high frequency signal of the frequency F0 received in step S4A (step S5A). The phase gradient with respect to the frequency F calculated in step S5A is substantially the same as the gradient calculated in step S5A under normal conditions shown in FIG.

[0071] In the second transmission, the distance measuring device 100A transmits the high-frequency signal with the frequency F0 generated in step S2A to the distance measuring device 100B (step S6A).

[0072] The device A masquerades as the distance measuring device 100B and receives the second high frequency signal from the distance measuring device 100A (step S6C).

[0073] The device A masquerades as the distance measuring device 100B and transmits a high-frequency signal of frequency F0 to the distance measuring device 100A in the second transmission (step S7C).

[0074] The distance measuring device 100A receives a second high frequency signal from the device A masquerading as the distance measuring device 100B (step S7A).

[0075] Distance measuring unit 135 of distance measuring device 100A calculates the phase gradient for frequency F based on the phase difference between the high frequency signal of frequency F0 transmitted in step S6A and the high frequency signal of frequency F0 received in step S7A (step S8). Since the high frequency signal of frequency F0 is received in step S7A, the calculated phase gradient for frequency F is substantially the same as the phase gradient for frequency F calculated in step S5A.

[0076] The authentication unit 134 of the ranging device 100A determines whether the phase gradient for frequency F calculated by the ranging unit 135 in step S5A differs from the phase gradient for frequency F calculated by the ranging unit 135 in step S8 by the amount of difference between frequency F0 and frequency F1 (step S9).

[0077] As a result, the authentication unit 134 of the distance measuring device 100A determines that the deviation is not equal to the difference between the frequency F0 and the frequency F1 (S9: NO), and determines that the authentication is not established (authentication not established) (step S10N).

[0078] Since the authentication is not established, the distance measuring device 100A ends the series of processes (END) without performing distance measuring processing, because a relay attack has occurred.

[0079] As described above, in the case of an abnormality, the difference in inclination according to the rule represented by the shared adjustment data is not obtained, so authentication is not established, and the distance measuring device 100A recognizes that the communication partner is another unauthorized device. Therefore, the vehicle 10 keeps the doors, trunk, etc. locked without unlocking them.

[0080] As described above, the ranging device 100A shares the shared adjustment data with the ranging device 100B in the sharing process. Then, when the ranging device 100A transmits a high-frequency signal of frequency F0 to the ranging device 100B and then receives a high-frequency signal of frequency F0 from the ranging device 100B, and when the ranging device 100A transmits a high-frequency signal of frequency F0 to the ranging device 100B and then receives a high-frequency signal of frequency F1 from the ranging device 100B, using the frequencies F0 and F1 included in the shared adjustment data, the ranging device 100B is authenticated as a legitimate other device. Only the ranging device 100B, which is a legitimate other device, has the shared adjustment data other than the ranging device 100A, and no unauthorized device has the shared adjustment data. Therefore, an unauthorized device cannot transmit or receive according to the rules represented by the shared adjustment data, and highly confidential communication can be realized.

[0081] Therefore, it is possible to provide the communication device 100S, the distance measuring device 100, and the authentication method in the communication device, which improves the confidentiality of communication.

[0082] The distance measuring device 100A also includes an oscillator circuit 121 that oscillates a high-frequency signal of a fundamental frequency fc, a frequency adjustment unit 122 that adjusts the frequency of the high-frequency signal oscillated by the oscillator circuit 121, and a multiplication unit 123 that multiplies the high-frequency signal whose frequency has been adjusted by the frequency adjustment unit 122. The shared processing unit 132 shares data representing adjustment amounts f0 and f1 to be added to the fundamental frequency fc as data relating to the frequencies F0 and F1. The frequency adjustment unit 122 generates a high-frequency signal of a frequency obtained by adding the adjustment amount f0 to the fundamental frequency fc, and generates a high-frequency signal of a frequency obtained by adding the adjustment amount f1 to the fundamental frequency fc. The multiplication unit 123 outputs a high-frequency signal of a frequency F0 by multiplying the high-frequency signal of a frequency obtained by adding the adjustment amount f0 to the fundamental frequency fc, and outputs a high-frequency signal of a frequency F1 by multiplying the high-frequency signal of a frequency obtained by adding the adjustment amount f1 to the fundamental frequency fc.

[0083] Therefore, by adding the adjustment amounts f0 and f1 to the fundamental frequency fc and multiplying it, high-frequency signals of frequencies F0 and F1, respectively, can be generated, and stable operation can be achieved by using an oscillator circuit 121 with an oscillation frequency lower than the frequencies F0 and F1 of the high-frequency signals to be transmitted and received.

[0084] In addition, since the distance measuring device 100A includes a memory 136 that stores data representing the adjustment amounts f0 and f1, the data representing the adjustment amounts f0 and f1 stored in the memory 136 can be used to easily and reliably generate high-frequency signals of frequencies F0 and F1.

[0085] The memory 136 also stores data indicating the order of using the adjustments f0 and f1. When the transmitting / receiving unit transmits a high-frequency signal of frequency F0 to the ranging device 100B and then receives a high-frequency signal of frequency F0 from the ranging device 100B, and then receives a high-frequency signal of frequency F1 from the ranging device 100B after transmitting the high-frequency signal of frequency F0 to the ranging device 100B, the authentication unit 134 authenticates the ranging device 100B as a legitimate other device. In this way, the accuracy of the authentication process can be improved by using the order of using the adjustments f0 and f1, and it is possible to provide the communication device 100S, the ranging device 100, and the authentication method in the communication device that further improves the confidentiality of communication.

[0086] Furthermore, the distance measuring device 100A has a configuration in which a distance measuring unit 135 is added to the communication device 100S. The distance measuring unit 135 measures the distance to the distance measuring device 100B authenticated as a genuine other device by the authentication unit 134 based on a phase difference between a high-frequency signal transmitted by the distance measuring device 100A to the distance measuring device 100B authenticated as a genuine other device by the authentication unit 134 and a high-frequency signal received by the distance measuring device 100A from the distance measuring device 100B authenticated as a genuine other device by the authentication unit 134. Therefore, it is possible to provide a distance measuring device 100 that can perform distance measurement processing with improved confidentiality of communication.

[0087] In the above, a configuration has been described in which the first transmission from ranging device 100A to ranging device 100B is performed at frequency F0 using an adjustment amount f0, the first transmission from ranging device 100B to ranging device 100A is performed at frequency F0 using an adjustment amount f0, the second transmission from ranging device 100A to ranging device 100B is performed at frequency F0 using an adjustment amount f0, and the second transmission from ranging device 100B to ranging device 100A is performed at frequency F1 using an adjustment amount f1.

[0088] However, the frequency combination (F0, F0) in the first transmission and reception and the frequency combination (F0, F1) in the second transmission and reception may be reversed, or the order may not matter. Even in this case, authentication processing can be performed between the ranging devices 100A and 100B using a frequency combination that cannot be known by unauthorized devices, thereby improving the confidentiality of communication.

[0089] The above describes exemplary embodiments of a communication device, a ranging device, and an authentication method in a communication device of the present invention. However, the present invention is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0090] This international application claims priority to Japanese patent application No. 2021-183686, filed on November 10, 2021, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0091] 10 Vehicles 20 Smart Key 100, 100A, 100B range finder 100S Communication Equipment 101 Antenna 110 Transmitter / receiver 120 Signal Generator 130 MCU 131 Main control unit 132 Shared Processing Unit 133 Frequency setting section 134 Authentication Department 135 Ranging section 136 Memory

Claims

1. a sharing processing unit that performs processing for sharing data regarding a first frequency and a second frequency used for communication with another device with the other device; A transceiver unit for transmitting and receiving high-frequency signals to and from the other device; an authentication unit that authenticates the other device as a legitimate other device when the transceiver unit receives a high frequency signal of the first frequency from the other device after transmitting the high frequency signal of the first frequency to the other device and when the transceiver unit receives a high frequency signal of the second frequency from the other device after transmitting the high frequency signal of the first frequency to the other device; 23. A communication device comprising:

2. an oscillator circuit for oscillating a high frequency signal having a fundamental frequency; a frequency adjusting unit that adjusts the frequency of a high-frequency signal oscillated by the oscillation circuit; a multiplication unit that multiplies the high-frequency signal whose frequency has been adjusted by the frequency adjustment unit; Further comprising: the sharing processing unit shares data representing a first adjustment amount and a second adjustment amount to be added to the fundamental frequency as data related to the first frequency and the second frequency, the frequency adjustment unit generates a high-frequency signal having a frequency obtained by adding the first adjustment amount to the fundamental frequency, and generates a high-frequency signal having a frequency obtained by adding the second adjustment amount to the fundamental frequency, 2. The communication device according to claim 1, wherein the multiplier unit outputs a high-frequency signal of the first frequency by multiplying a high-frequency signal of a frequency obtained by adding the first adjustment amount to the fundamental frequency, and outputs a high-frequency signal of the second frequency by multiplying a high-frequency signal of a frequency obtained by adding the second adjustment amount to the fundamental frequency.

3. The communication device of claim 2 , further comprising a storage unit that stores data representative of the first adjustment amount and the second adjustment amount.

4. the storage unit further stores data representing an order in which the first adjustment amount and the second adjustment amount are used; 4. The communication device according to claim 3, wherein the authentication unit authenticates the other device as a legitimate other device when the transceiver unit transmits a high-frequency signal of the first frequency to the other device, receives the high-frequency signal of the first frequency from the other device, and then transmits a high-frequency signal of the second frequency to the other device, after the transceiver unit has transmitted the high-frequency signal of the first frequency to the other device.

5. A communication device according to any one of claims 1 to 4, a distance measuring unit that measures a distance to the other device authenticated as the genuine other device by the authentication unit based on a phase difference between a high-frequency signal that the transmitting / receiving unit transmits to the other device authenticated as the genuine other device by the authentication unit and a high-frequency signal that the transmitting / receiving unit receives from the other device authenticated as the genuine other device by the authentication unit; A ranging device comprising:

6. a sharing processing unit that performs processing for sharing data regarding a first frequency and a second frequency used for communication with another device with the other device; a transceiver unit for transmitting and receiving high-frequency signals to and from the other device; A communication device comprising: An authentication method in a communication device, wherein when the transceiver unit transmits a high-frequency signal of the first frequency to the other device and then receives a high-frequency signal of the first frequency from the other device, and when the transceiver unit transmits a high-frequency signal of the first frequency to the other device and then receives a high-frequency signal of the second frequency from the other device, the other device is authenticated as a legitimate other device.

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