JP2020061625A - Unauthorized communication prevention system and unauthorized communication prevention method - Google Patents

Abstract

To provide an unauthorized communication prevention system and an unauthorized communication prevention method, capable of ensuring accuracy of determination that communication is unauthorized communication.SOLUTION: An unauthorized communication prevention system 19 obtains propagation characteristics of a radio wave Si transmitted through Bluetooth communication to calculate a measured value Dx according to a distance between communication devices from the propagation characteristics. A determination processing unit 44 determines whether communication between the communication devices is authorized or unauthorized by comparing the measured value Dx and a specified value Dk. When a confirmation unit 45 detects a determination result that the communication is unauthorized communication a plurality of times (continuous detection), it determines the communication as unauthorized communication. When it is determined that the communication is unauthorized communication, a control unit 46 takes measures against the unauthorized communication.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an unauthorized communication prevention system and an unauthorized communication prevention method for preventing unauthorized establishment of authentication communication.

  2. Description of the Related Art Conventionally, there is known a distance measuring system in which radio waves are communicated between a terminal and its communication partner to measure the distance between them and to judge the validity of the measured distance (see Patent Document 1, etc.). It is considered that this type of distance measuring system will be used as an unauthorized communication prevention system that sets whether communication is valid or invalid based on the result of judgment as to whether the measured values calculated through radio wave communication between two persons are valid or not. Has been done. The unauthorized communication prevention system, for example, obtains a measurement value according to the distance between the terminal and its communication partner, and when this measurement value is determined to be valid (within a predetermined range), for example, wirelessly between the two parties. The establishment of the executed ID collation is permitted. This enables the terminal to operate the communication partner.

JP, 2014-227647, A

In this main unauthorized communication prevention system, there is a need to accurately detect unauthorized communication.
An object of the present invention is to provide an unauthorized communication prevention system and an unauthorized communication prevention method capable of ensuring the accuracy of determination that communication is unauthorized communication.

  An unauthorized communication prevention system that solves the above problem obtains a measured value according to the distance between the first communication device and the second communication device when communication is established between the two devices, and based on the measured value. In addition, a determination unit that determines whether the communication between the two parties is legitimate communication or unauthorized communication, a confirmation unit that confirms whether or not the determination result that is determined as unauthorized communication occurs multiple times, and the unauthorized communication When a determination result that is determined to be multiple times occurs, as a countermeasure against the unauthorized communication, a control unit that controls communication when the first communication device and the second communication device perform wireless authentication. Prepared

  According to this configuration, when the determination result that the communication is the unauthorized communication is detected a plurality of times, the communication when the first communication device and the second communication device perform the wireless authentication is controlled to be appropriate for the unauthorized communication. Take appropriate action. As described above, when the determination result that the communication is the unauthorized communication is detected plural times, it is advantageous to accurately determine the unauthorized communication if the determination result of the unauthorized communication is determined and the countermeasure is taken. Becomes Therefore, it is possible to ensure the accuracy of determining that the communication is unauthorized.

  In the unauthorized communication prevention system, the confirmation unit confirms whether or not the determination results that are determined to be unauthorized communication are continuous, and the control unit is configured to determine whether the determination results that are determined to be unauthorized communication are continuous. It is preferable to take measures against the unauthorized communication. According to this configuration, it is possible to deal with the illegal communication under the situation where the communication is likely to be illegally established by a third party.

  In the unauthorized communication prevention system, it is preferable that the confirming unit causes the control unit to take countermeasures against the unauthorized communication when the determination result in which the measured value has a remarkably incorrect value is detected a plurality of times. According to this configuration, it is possible to deal with the illegal communication under the situation where the illegal communication by the third party is likely to be attempted.

  In the unauthorized communication prevention system, the confirmation unit uses the measurement value and an index value different from the measurement value, and from a composite determination of these values, a determination result that the communication is determined to be unauthorized communication is performed a plurality of times. It is preferable to confirm whether or not it occurs. According to this configuration, it is advantageous to accurately determine whether the communication is legitimate communication or unauthorized communication.

  In the unauthorized communication prevention system, the determination unit changes the channel from one of the first communication device and the second communication device to the other to transmit a plurality of radio waves, and based on the phase difference of the radio waves of each channel, It is preferable to obtain a measured value and determine from the measured value whether the communication between the two parties is regular communication or unauthorized communication. According to this configuration, when radio waves are transmitted on a plurality of channels and whether the communication is legitimate or fraudulent based on the measurement value obtained from the phase difference of the radio waves of the respective channels, if the communication is attempted fraudulently, It is necessary to tamper with the phase information, but with random tampering, the probability that unauthorized communication will be established is low. Therefore, if an unauthorized communication is attempted, there is a high possibility that the unauthorized communication will be repeated many times, and the number of times the determination result of the authenticity / illegal communication is the unauthorized communication increases. It can be said that this is highly effective in detecting unauthorized communication without omission when confirming the correctness of communication using the determination logic of this example.

  An illegal communication preventing method for solving the above-mentioned problem is to obtain a measured value according to a distance between the first communication device and the second communication device when communication is established between the two communication devices, and use the measured value as a basis. First, a step of determining whether the communication between the two parties is a legitimate communication or a fraudulent communication, a step of confirming whether or not the determination result of the fraudulent communication occurs a plurality of times, and the fraudulent communication. When a determination result that is determined to occur occurs a plurality of times, a step of controlling communication when the first communication device and the second communication device perform wireless authentication is provided as a countermeasure against the unauthorized communication.

  According to the present invention, it is possible to ensure the accuracy of determination that communication is illegal communication.

The block diagram of the electronic key system of one Embodiment. Schematic diagram of the unauthorized communication prevention system. The concrete block diagram of an unauthorized communication prevention system. 6 is a flowchart executed when determining whether the communication is regular communication or unauthorized communication. FIG. 6 is a view showing an example of unauthorized communication by radio relay. Explanatory drawing which shows the determination logic of concrete communication. The schematic diagram which shows the authenticity / illegal judgment logic of communication of another example.

An embodiment of the unauthorized communication prevention system and the unauthorized communication prevention method will be described below with reference to FIGS.
As shown in FIG. 1, the vehicle 1 includes an electronic key system 4 that performs wireless ID verification with the terminal 2 to execute or permit the operation of the vehicle-mounted apparatus 3. The electronic key system 4 is a key operation-free system that executes ID verification (smart verification) with the terminal 2 by narrow-range wireless communication triggered by communication from the vehicle 1. The vehicle-mounted device 3 includes, for example, a door lock device 5 and an engine 6. The terminal 2 is a terminal mainly having a key function, that is, a so-called electronic key.

  The vehicle 1 includes a verification ECU (Electronic Control Unit) 7 that performs ID verification, a body ECU 8 that manages a power supply of vehicle-mounted electrical components, and an engine ECU 9 that controls the engine 6. These ECUs are electrically connected via a communication line 10 in the vehicle. In the memory (not shown) of the verification ECU 7, the key ID of the terminal 2 registered in the vehicle 1 and the key unique key used when authenticating the ID verification are registered. The body ECU 8 controls the door lock device 5 that switches locking and unlocking of the vehicle door 11.

  The vehicle 1 includes a communication unit 12 that executes communication in the vehicle 1. The communication unit 12 executes communication with the terminal 2 by bidirectional communication (smart communication) of LF (Low Frequency) -UHF (Ultra High Frequency), for example. In this case, the communication from vehicle 1 to terminal 2 is preferably LF communication, and the communication from terminal 2 to vehicle 1 is preferably UHF communication.

  The terminal 2 includes a terminal control unit 15 that controls the operation of the terminal 2 and a communication unit 16 that executes communication in the terminal 2. The communication unit 16 performs wireless communication with the communication unit 12 of the vehicle 1 via the short range wireless communication. A unique key ID and a unique key of the terminal 2 are written and stored in a memory (not shown) of the terminal control unit 15.

  The vehicle 1 periodically LF-transmits a wake signal from the communication unit 12 to activate the terminal 2 in the standby state. When the communication unit 16 receives the wake signal transmitted from the communication unit 12, the terminal 2 switches from the standby state to the activated state, and transmits the ACK signal to the vehicle 1 from the communication unit 16 by UHF. When the communication ECU 12 receives the ACK signal transmitted from the terminal 2 and recognizes the establishment of communication, the verification ECU 7 executes ID verification (smart verification). The smart collation includes key ID collation for confirming the correctness of the key ID registered in the terminal 2, challenge response authentication using a predetermined encryption key, and the like.

  When the communication with the terminal 2 located outdoors is established, the verification ECU 7 performs smart verification (outdoor smart verification) with the terminal 2. The establishment of smart verification (outdoor smart verification) with the terminal 2 located outdoors is a condition for permitting or executing the operation of the door lock device 5 by the body ECU 8. When the communication with the terminal 2 located indoors is established, the verification ECU 7 executes smart verification (indoor smart verification) with the terminal 2. The establishment of smart verification (indoor smart verification) with the terminal 2 located indoors is one condition for permitting the transition operation of the vehicle power supply (start operation of the engine 6).

  As shown in FIG. 2, the vehicle 1 and the terminal 2 are provided with a function (unauthorized communication prevention system 19) for determining whether the communication is legitimate / illegal by obtaining a measurement value Dx according to the distance between the two through communication. Prepare The unauthorized communication prevention system 19 includes a first communication device 20 provided on one of the vehicle 1 and the terminal 2 and a second communication device 21 provided on the other of these. In the case of this example, for example, the first communication device 20 is the terminal 2 and, for example, the second communication device 21 is the vehicle 1 (collation ECU 7). The communication between the first communication device 20 and the second communication device 21 is preferably, for example, Bluetooth (registered trademark).

  The unauthorized communication prevention system 19 transmits and receives radio waves Si between a first communication device 20 and a second communication device 21 that are wirelessly connected over a plurality of channels, and shows propagation characteristics (for example, amplitude and phase) in each of these channels. Ask. Then, the unauthorized communication prevention system 19 equivalently calculates the propagation time of the impulse, that is, the measured value Dx, by synthesizing the obtained propagation characteristics of a plurality of channels and inverse Fourier transforming the propagation characteristics obtained by the synthesizing. .

  The unauthorized communication prevention system 19 transmits the radio wave Si from the first communication device 20 to the second communication device 21 to measure the propagation characteristics, and also transmits the radio wave Si from the second communication device 21 to the first communication device 20. To measure the propagation characteristics. As described above, in the unauthorized communication prevention system 19 of the present example, the radio waves Si are transmitted and received between the first communication device 20 and the second communication device 21, and both the first communication device 20 and the second communication device 21 Propagation characteristics are measured.

  As shown in FIG. 3, the unauthorized communication prevention system 19 includes a determination unit 22 that determines whether communication (smart communication) is correct based on a measurement value Dx obtained from radio wave communication between two parties. When the communication is established between the first communication device 20 and the second communication device 21 (transmission of wake signal-ac signal), the determination unit 22 of this example measures the measured value Dx according to the distance between the two. Then, based on the measured value Dx, it is determined whether the communication between the two parties is regular communication or unauthorized communication. The determination unit 22 includes a radio wave transmission unit 23 that transmits the radio wave Si for distance measurement, a radio wave reception unit 24 that receives the radio wave Si for distance measurement, and a process execution unit that executes a series of processes from the transmitted and received radio waves Si. And 25.

  The radio wave transmission unit 23 includes a waveform generation unit 28, a modulation unit 29, a DA converter 30, a mixer 31, an oscillator 32, and a transmission antenna 33. The waveform generation unit 28 generates a periodic signal Sk composed of a binarized code as the radio wave Si for distance measurement, and outputs this to the modulation unit 29. The periodic signal Sk is a signal in which the binary coded "0" and "1" are switched for each period. The modulator 29 performs GFSK (Gaussian Frequency Shift Keying) modulation on the input signal. The periodic signal Sk is modulated by the modulator 29, D / A converted by the DA converter 30, and the baseband signal Sb is superimposed on the carrier wave of the oscillator 32 by the mixer 31 and transmitted from the transmitting antenna 33. .

  The radio wave reception unit 24 includes a reception antenna 34, a mixer 35, an oscillator 36, an AD converter 37, and a Fourier transform unit 38. When the reception antenna 34 receives the radio wave Si of the periodic signal Sk transmitted from the radio wave transmission section 23, the radio wave reception section 24 converts the received radio wave into a baseband signal Sb by the mixer 35, and the AD converter 37 converts the received radio wave into an A / A signal. D-convert. The Fourier transform unit 38 performs a Fourier transform (FFT transform) on the signal after the A / D conversion to extract the propagation characteristic of the radio wave Si. The propagation characteristics consist of a data group of the amplitude and phase of the radio wave Si. The propagation characteristic is preferably a DC component propagation characteristic which is a characteristic value when the frequency is “0” in the frequency spectrum after the Fourier transform (after the FFT transform).

  The unauthorized communication prevention system 19 performs the measurement of the propagation characteristic at the time of communication on all the channels to be communicated. When the communication is Bluetooth, there are a plurality of channels (for example, 40 channels), and therefore the propagation characteristics are measured on all the channels (CH1, CH2, ..., CHn). Thus, in the case of this example, the radio wave Si is transmitted at a plurality of frequencies by transmitting the radio wave Si at a plurality of channels.

  The processing execution unit 25 includes a multiplication unit 41, a synthesis unit 42, an inverse Fourier transform unit 43, and a determination processing unit 44. The multiplication unit 41, the synthesis unit 42, the inverse Fourier transform unit 43, and the determination processing unit 44 may be provided in either the first communication device 20 or the second communication device 21.

  The multiplication unit 41 has a propagation characteristic measured by transmitting radio waves from the first communication device 20 to the second communication device 21, and a propagation characteristic measured by transmitting radio waves from the second communication device 21 to the first communication device 20. Is multiplied by. As described above, the multiplication unit 41 of this example transmits the radio wave from the first communication device 20 to the second communication device 21 and the FFT result obtained by transmitting the radio wave from the second communication device 21 to the first communication device 20. The obtained FFT result is multiplied.

The combining unit 42 combines the extracted propagation characteristics of a plurality of channels. The synthesizing unit 42 of this example obtains frequency data H (f) which is a vector in which the propagation characteristics of each channel are arranged.
The inverse Fourier transform unit 43 performs an inverse Fourier transform on the combined propagation characteristics to calculate a measurement value Dx according to the distance between the first communication device 20 and the second communication device 21. The inverse Fourier transform unit 43 in this example performs an inverse Fourier transform on the frequency data H (f) obtained by the synthesizing unit 42, and obtains time data y (t) as the measured value Dx from this calculation.

  The determination processing unit 44 determines the validity of the measurement value Dx (time data y (t)) calculated by the inverse Fourier transform. The determination processing unit 44 of the present example compares the measured value Dx with a predetermined specified value Dk, and when the measured value Dx is less than the specified value Dk, the communication of the first communication device 20 and the second communication device 21 is normally communicated. To determine. On the other hand, when the measured value Dx is greater than or equal to the specified value Dk, the determination processing unit 44 determines that the communication between the first communication device 20 and the second communication device 21 is illegal communication. When the determination processing unit 44 determines that the communication is illegal, even if the ID collation and the challenge response authentication are established in the smart collation, the determination processing unit 44 does not shift the smart collation to establishment. Further, if the determination processing unit 44 determines that the communication is illegal, and if the smart communication is being executed, the smart communication is terminated midway and the smart collation is not established.

  When it is determined that the communication between the first communication device 20 and the second communication device 21 is unauthorized communication, the unauthorized communication prevention system 19 again executes (retry) the process of determining whether the communication is legitimate / unauthorized. Therefore, when the communication between the first communication device 20 and the second communication device 21 is illegal communication, a series of processes for transmitting and receiving the radio wave Si, measuring the propagation characteristic, and obtaining the measurement value Dx are performed again.

  The unauthorized communication prevention system 19 includes a confirmation unit 45 that confirms whether or not the determination result of the unauthorized communication is multiple times in the determination of the authenticity / illegal communication. The confirmation unit 45 of this example confirms whether or not the determination results of the unauthorized communication are continuous.

  The unauthorized communication prevention system 19 includes a control unit 46 that controls communication between the first communication device 20 and the second communication device 21 based on the confirmation result of the confirmation unit 45. When a plurality of determination results that are determined to be unauthorized communication occur, the control unit 46 of the present example performs the wireless authentication of the first communication device 20 and the second communication device 21 as a countermeasure against the unauthorized communication. Control communication. The control unit 46 determines the determination result that the communication is the unauthorized communication and executes the countermeasure against the unauthorized communication when the determination results that are determined to be the unauthorized communication continue. As measures against this, for example, there is a process of tightening (decreasing the value) the specified value Dk used for determining whether or not the communication is unauthorized, or forcibly stopping the function (smart function) of the smart verification system.

Next, the operation and effect of the unauthorized communication prevention system 19 of the present embodiment will be described with reference to FIGS. 4 to 6.
As shown in FIG. 4, in step 101, the first communication device 20 transmits the radio wave Si to the second communication device 21, and causes the second communication device 21 to measure the propagation characteristic. In the case of the present example, first, the waveform generation unit 28 generates a periodic signal Sk in which “0” and “1” are periodically repeated, and outputs this to the modulation unit 29. The modulator 29 GFSK-modulates the periodic signal Sk of the repeated signal of “0” and “1”, and outputs this to the DA converter 30. The DA converter 30 D / A converts the modulated signal. The baseband signal Sb D / A-converted by the DA converter 30 is placed on a carrier wave by the mixer 31, and is transmitted from the transmission antenna 33 as a radio wave Si. When the radio wave Si is transmitted in a plurality of channels, the radio wave Si of each channel is transmitted by being placed on a corresponding carrier.

  The second communication device 21 receives the radio wave Si transmitted from the first communication device 20 with the reception antenna 34. The signal received by the receiving antenna 34 is converted into the baseband signal Sb through the mixer 35. The baseband signal Sb is A / D converted by the AD converter 37 and output to the Fourier transform unit 38. The Fourier transform unit 38 Fourier transforms the signal after A / D conversion, and measures the propagation characteristic (amplitude and phase of frequency spectrum) of the baseband signal Sb. The propagation characteristic is preferably, for example, the propagation characteristic of the center frequency of the received radio wave received by the radio wave receiving unit 24.

  In step 102, the second communication device 21 transmits the radio wave Si to the first communication device 20 and causes the first communication device 20 to measure the propagation characteristics (amplitude and phase). That is, the radio wave Si is transmitted from the second communication device 21 to the first communication device 20, and the propagation characteristics (amplitude and phase) are also measured in the first communication device 20. Note that the measurement of the propagation characteristics is the same as the case of performing radio wave transmission from the first communication device 20 to the second communication device 21, and thus the description thereof is omitted.

  When the propagation characteristics are measured in the round trip of the first communication device 20 and the second communication device 21, respectively, the multiplication unit 41 transmits the radio waves from the first communication device 20 to the second communication device 21 and measures the propagation characteristics. The (FFT result) is multiplied by the propagation characteristic (FFT result) measured by transmitting the radio wave from the second communication device 21 to the first communication device 20. As a result, even if a clock error or an initial phase error of the PLL occurs in each device of the unauthorized communication prevention system 19, these errors appear as phase errors of opposite signs on the transmission side and the reception side. The multiplication of the results cancels these errors.

  In step 103, the first communication device 20 and the second communication device 21 sequentially measure the propagation characteristics in each communication channel. When the communication is Bluetooth, there are a plurality of channels (for example, 40 channels), so that the propagation characteristics of communication (round trip) are measured in all of the channels. Therefore, for example, when the radio waves of CH2 to CHn are transmitted and received, the propagation characteristics H (f2) to H (fn) of the center frequencies f2 to fn of each channel are obtained. The propagation characteristics of a plurality of frequencies are measured because impulses cannot be created with the propagation characteristics of one frequency.

  In step 104, the combining unit 42 combines the round-trip propagation characteristics of all channels. In the case of this example, the combining unit 42 creates a vector in which the propagation characteristics of each channel are arranged. In this example, [H (f1), H (f2), ..., H (fn)] is obtained as a vector in which the propagation characteristics of each channel are arranged, that is, frequency data H (f).

  In step 105, the inverse Fourier transform unit 43 performs an inverse Fourier transform on the combined propagation characteristic (frequency data H (f)). In the case of this example, the vector (frequency data H (f)) is used as input data, and this is subjected to inverse Fourier transform, and the calculation result is obtained. The calculation result of the inverse Fourier transform can be acquired as time data y (t). The time data y (t) is represented by [y (t1), y (t2), ..., Y (tn)]. Note that t1 to tn are time data corresponding to the propagation characteristics H (f1) to H (fn). The determination processing unit 44 uses the measured value Dx obtained from the time data y (t) to determine whether the communication is legitimate / illegal from the measured value Dx.

  As shown in FIG. 5, it is assumed that an unauthorized communication is attempted in which an LF radio wave is relayed between the vehicle 1 and the terminal 2 by a relay device to illegally establish authentication (smart verification) between these two parties. In this fraudulent act, in order to make the terminal 2 appear to be located in the vicinity of the vehicle 1, the phase information of the radio wave Si for distance measurement is falsified at random and relayed, and the correctness determination of communication is illegally established. And However, since this fraudulent act is determined with a low probability, in practice, in the determination of the validity of the measured value Dx, the determination result that the measured value Dx becomes the specified value Dk or more continues many times. is assumed.

  In the case of unauthorized communication using a repeater, the confirmation unit 45 should confirm that the measured value Dx is the specified value Dk or more multiple times, and in this case, the vehicle 1 and the terminal 2 in the established state are tried. Take corrective action against unauthorized communication. Therefore, when the confirmation unit 45 confirms that the measured value Dx is equal to or greater than the specified value Dk, the confirmation unit 45 determines the determination result that the communication is illegal communication and notifies that the illegal communication is to be dealt with. Request) to the control unit 46.

  When the countermeasure execution request is input from the confirmation unit 45, the control unit 46 executes countermeasures against unauthorized communication through the radio relay. The control unit 46 of the present example tightens (decreases the value) the specified value Dk used in the determination of whether the communication is legitimate / illegal as a measure against the illegal communication through the radio relay, or functions of the smart verification system (smart function). Or forcibly stop. Therefore, it becomes difficult for the communication correctness determination to be fraudulently transferred to establishment, and it is possible to prevent establishment of unauthorized communication by a third party.

  The unauthorized communication prevention system 19 may have a function (return function) of returning the smart verification system from the stop when the smart verification system (smart function) is forcibly stopped. In this case, it is preferable that the return of the smart verification system is a process that imposes an operation of the terminal 2 by the user, for example. The operation of the terminal 2 by the user is, for example, operation of various buttons provided on the terminal 2 (remote operation by wireless communication), or immobilizer communication in which the terminal 2 is held over the short-range wireless antenna of the vehicle 1 to perform authentication by RFID. There are operations etc.

  Now, in the case of this example, when the determination result that communication is unauthorized communication is detected multiple times (continuous detection), the communication when the first communication device 20 and the second communication device 21 perform wireless authentication is controlled. Then, appropriate measures are taken against the unauthorized communication. In this way, if the determination result that communication is unauthorized communication is detected multiple times (continuous detection), by determining the determination result that there is unauthorized communication and taking corrective action, it is possible to accurately determine unauthorized communication. It is advantageous to do. Therefore, it is possible to ensure the accuracy of determining that the communication is unauthorized communication.

  The confirmation unit 45 confirms whether or not the determination results of the unauthorized communication are continuous. The control unit 46 executes the process for the unauthorized communication when the determination results of the unauthorized communication are continuous. Therefore, it is possible to deal with the illegal communication under the situation where the communication is likely to be illegally established by a third party.

  The confirmation unit 45 may cause the control unit 46 to take countermeasures against the unauthorized communication when the determination result in which the measured value Dx takes a significantly unreasonable value is detected a plurality of times. The remarkably unreasonable value is preferably a value (eg, 50 m or 100 m) sufficiently larger than the specified value Dk. In this case, when the measured value Dx is the specified value Dk or more, but when the judgment result is a remarkably unreasonable value or less, the judgment is retried without judging the communication as unreasonable, and the measured value Dx is a remarkably unreasonable value. When is detected multiple times, the communication is recognized as illegal and the countermeasure is taken. Therefore, it is possible to deal with the illegal communication under a situation where there is a high possibility that the illegal communication is attempted by a third party.

  Further, as shown in FIG. 6, the confirmation unit 45 uses the measurement value Dx and an index value different from the measurement value Dx, and the determination result of the unauthorized communication is determined from the composite determination of these values. It may be confirmed whether or not a plurality of occurrences occur. As an example of this, for example, when another index value is “integration of the difference (Dk−Dx) between the measured value Dx and the specified value Dk”, the difference when the measured value Dx becomes the specified value Dk or more is not so large. If it is not significant, the determination result of the unauthorized communication is transferred to the confirmation, on the condition that the number of times of the unauthorized communication is large (the example in the upper part of FIG. 6). If the difference when the measured value Dx is equal to or larger than the specified value Dk is large, the determination result of the unauthorized communication is transferred to the confirmation even if the number of times the unauthorized communication is determined is small (the example in the lower part of FIG. 6). ). Therefore, it is advantageous to accurately determine whether the communication is regular communication or unauthorized communication.

  The distance measuring method of the unauthorized communication preventing system 19 is a distance measuring method using a Bluetooth communication signal. In the case of this method, the determination unit 22 changes the channel from one of the first communication device 20 and the second communication device 21 to the other and transmits a plurality of radio waves Si, and the measured value is based on the phase difference of the radio waves Si of each channel. Dx is obtained, and it is determined from the measured value Dx whether the communication between the two parties is regular communication or unauthorized communication. By the way, in the case of this distance measuring method, it is necessary to falsify the phase information of the radio wave Si in order to illegally establish the communication, but it can be said that the probability of establishing the illegal communication is low with random falsification. . Therefore, if an unauthorized communication is attempted, there is a high possibility that the unauthorized communication will be repeated many times, and the number of times the determination result of the authenticity / illegal communication is the unauthorized communication increases. It can be said that this is highly effective in detecting unauthorized communication without omission when confirming the correctness of communication using the determination logic of this example.

The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
As shown in FIG. 7, an unauthorized communication determination method is, for example, by transmitting and receiving radio waves between the first communication device 20 and the second communication device 21, and measuring the time (time stamp etc.) required for the transmission and reception of the radio waves. Alternatively, a method of determining whether the communication is legitimate / illegal may be used. In this case, it is preferable to use, for example, UWB (Ultra Wide Band) radio waves as the radio waves to be transmitted and received.

  When the measured value Dx is equal to or greater than the specified value Dk, a series of processes from measurement to determination is retried without confirming the communication authenticity / illegal judgment result, and the situation of illegal communication occurs multiple times. In addition, any mode may be used as long as the determination result of the unauthorized communication is confirmed.

Communication for wireless authentication may be either distance measurement communication or smart verification communication.
The measurement value Dx is not limited to the distance measurement value that is the distance between the first communication device 20 and the second communication device 21, and other parameters such as the received signal strength (RSSI) when the radio wave Si is received. You may change to.

The detection of unauthorized communication a plurality of times is not limited to continuous detection, and may be discontinuous, for example.
The measures to be taken when an unauthorized communication is detected are not limited to the examples described in the embodiments, and various methods can be applied as long as the establishment of communication between two parties can be prevented.

The other index value is not limited to the difference when the measured value Dx is equal to or more than the specified value Dk or the number of NG judgments, and various other parameters can be appropriately adopted.
-Wireless authentication is not limited to smart verification, and may be any communication that can confirm whether the terminal 2 is correct.

  -Whether the communication is correct or not is not limited to being performed on a plurality of channels, but may be performed using only one channel. In this case, the radio frequency Si is transmitted a plurality of times by switching the center frequency of the baseband signal in one channel, and the correctness of communication is determined using each radio wave Si.

-Propagation characteristics are not limited to both amplitude and phase, and may be only one. Parameters other than these may be used as the propagation characteristics.
The propagation characteristic may be a characteristic value other than the DC component.

The correctness determination of communication is not limited to being performed after the distance measurement, and the timing to be performed before or during the distance measurement is not particularly limited.
The periodic signal Sk is not limited to the periodic signals of “0” and “1”, and may be a signal of only “0” or only “1”, for example. Further, the combination of “0” and “1” can be changed as appropriate as long as the binarization code is periodically repeated, such as a signal in which a data group of “0”, “0”, and “1” is repeated. .

The first communication device 20 may be a high function mobile phone having an electronic key function.
-Various frequencies can be adopted as the frequency of the radio wave.
The digital code is not limited to the binarized code, and may be changed to another code on the assumption that modulation such as QPSK (Quadrature Phase Shift Keying) is used.

The modulator 29 is not limited to GFSK, and may be changed to another member such as simple FSK.
The calculation of the measurement value Dx is not limited to the calculation using the Fourier transform (inverse Fourier transform), and another calculation method may be adopted.

  The first communication device 20 is not limited to the terminal 2 (electronic key) and the second communication device 21 is not limited to the vehicle 1. For example, the first communication device 20 may be a wireless communication type personal computer and the second communication device 21 may be a wireless LAN router.

  The unauthorized communication prevention system 19 is not limited to a system that transmits and receives radio waves to measure a distance. For example, it may be a unidirectional method in which radio waves are transmitted from only one of the first communication device 20 and the second communication device 21 to the other to measure the distance. In addition, the first communication device 20 and the second communication device 21 exchange radio waves with each other, and again, the radio wave is transmitted from one of the first communication device 20 and the second communication device 21 to the other, and then the propagation characteristic is obtained. Therefore, distance measurement between two persons may be performed.

The communication method is not limited to Bluetooth or UWB, and other communication such as wireless LAN may be used.
The unauthorized communication prevention system 19 is not limited to being used in an electronic key system for wirelessly authenticating an electronic key for a vehicle, and may be applied to various systems and devices.

  1 ... Vehicle, 2 ... Terminal, 20 ... 1st communication machine, 21 ... 2nd communication machine, 22 ... Judgment part, 45 ... Confirmation part, 46 ... Control part, Dx ... Measured value.

Claims (6)

When communication is established between the first communication device and the second communication device, a measurement value according to the distance between the two parties is obtained, and based on the measurement value, the communication between the two parties is legitimate communication or illegal. A determination unit that determines which of the communication is,
A confirmation unit that confirms whether or not the determination result that is determined as unauthorized communication occurs multiple times,
A control unit that controls communication when the first communication device and the second communication device perform wireless authentication as a countermeasure against the unauthorized communication when the determination result determined to be the unauthorized communication occurs a plurality of times. Unauthorized communication prevention system with and. The confirmation unit confirms whether or not the determination results determined to be unauthorized communication are continuous,
The unauthorized communication prevention system according to claim 1, wherein the control unit executes a countermeasure against the unauthorized communication when the determination results that are determined to be the unauthorized communication continue. The unauthorized communication prevention system according to claim 1 or 2, wherein the confirmation unit causes the control unit to take countermeasures against the unauthorized communication when the determination result in which the measured value has a remarkably incorrect value is detected a plurality of times. . The confirmation unit uses the measured value and an index value different from the measured value, and confirms whether or not a judgment result that is judged as unauthorized communication occurs multiple times from a composite judgment of these values. The unauthorized communication prevention system according to any one of claims 1 to 3. The determination unit changes the channel from one of the first communication device and the second communication device to the other to transmit a plurality of radio waves, obtains the measurement value based on the phase difference of the radio waves of each channel, and The unauthorized communication prevention system according to any one of claims 1 to 4, wherein it is determined from the measured value whether the communication between the two parties is regular communication or unauthorized communication. When communication is established between the first communication device and the second communication device, a measurement value according to the distance between the two parties is obtained, and based on the measurement value, the communication between the two parties is legitimate communication or illegal. Determining which of the communications is,
A step of confirming whether or not a judgment result that is judged as illegal communication occurs plural times,
When a determination result that is determined to be unauthorized communication occurs a plurality of times, as a countermeasure against the unauthorized communication, a step of controlling communication when the first communication device and the second communication device perform wireless authentication. Unauthorized communication prevention method equipped with.