JP2018066207A - Portable machine and communication control method for preventing relay attack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unintended operation of a vehicle caused by a relay attack.SOLUTION: A portable machine for application to a smart keyless entry system further includes RF intensity detection circuits (22-25) for receiving a reflected wave of a high frequency signal transmitted from an RF transmission circuit and calculating a signal intensity level of the reflected wave. A controller (21) outputs second information as a high frequency signal while smart keyless entry operation is not being performed and determines that the portable machine is in a still state when a situation in which a signal intensity level calculated based on a reflected wave of a harmonic signal corresponding to the second information is within the range of two thresholds lasts for a stop determination time or longer. First information indicating a match of the collation results in the smart keyless entry operation is stopped while the portable machine is being determined to be in a still state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a portable device that is improved in security without impairing the convenience of a smart keyless entry system, and a communication control method that prevents a relay attack.

  Conventionally, a smart keyless entry system has been developed that can perform radio communication by radio waves between a portable device possessed by a vehicle user and the vehicle, and control a door of the vehicle.

  In the smart keyless entry system, a low frequency signal is output from the vehicle by pressing a switch provided on the door. On the other hand, the portable device receives the low frequency signal, responds with the high frequency signal, and performs door control.

  However, in recent years, there has been a problem that a vehicle having a smart keyless entry function is stolen or intruded by a method called a relay attack. This relay attack is an illegal technique for intentionally installing a repeater, enabling wireless communication, and performing vehicle control even when a portable device is located at a distance where radio waves do not reach.

  FIG. 17 is an exemplary diagram showing a positional relationship between the vehicle and the portable device in a state where the smart keyless entry does not operate. Specifically, FIG. 17 shows a state in which the vehicle on which the vehicle-mounted device 1 is mounted and the portable device 2 exist at a distance L of several tens of meters, corresponding to an environment where radio waves do not reach. Is shown. In addition, the expression “vehicle 1” used in the following description means a vehicle on which the in-vehicle device 1 is mounted.

  On the other hand, FIG. 18 is an exemplary view when a relay attack using a repeater is performed with respect to the positional relationship of FIG. As shown in FIG. 18, by providing the repeater 3 between the vehicle 1 and the portable device 2, a malicious user 4 can perform door control by relaying a low-frequency signal and a high-frequency signal. turn into.

  For this reason, conventionally, a method has been developed in which unlocking is not performed by reducing the output value of the response signal returned by the portable device 2 (see, for example, Patent Document 1).

JP 2010-121297 A

However, the prior art has the following problems.
In the method according to Patent Document 1, the portable device 2 cannot distinguish whether it is a signal directly received from the vehicle 1 or a signal via the repeater 3. For this reason, the technique according to Patent Document 2 has a problem that it is difficult to determine whether or not a relay attack is being performed.

  The present invention has been made to solve the above-described problems, and provides a portable device capable of preventing unintended vehicle operation due to a relay attack, and a communication control method for preventing a relay attack. Objective.

  The portable device according to the present invention is applied to a smart keyless entry system that performs radio communication by radio waves between a portable device possessed by a user of the vehicle and the vehicle and executes a predetermined control operation on the vehicle. An LF receiving circuit that receives a low-frequency signal output from a vehicle as activation information for a control operation, an RF transmitting circuit that transmits a high-frequency signal, and a reflection of the high-frequency signal transmitted from the RF transmitting circuit When a low frequency signal is received via an RF intensity detection circuit that receives a wave and calculates a signal intensity level of a reflected wave and an LF reception circuit, data set in advance corresponding to the low frequency signal and activation information A controller that outputs first information indicating that the matching results are matched as a high-frequency signal through the RF transmission circuit when the matching results match. An RF intensity detection circuit that receives a reflected wave of a high-frequency signal transmitted from the RF transmission circuit and calculates a signal intensity level of the reflected wave, and the controller performs a smart keyless entry operation, Second information different from the first information is output as a high-frequency signal via the RF transmission circuit, and the signal intensity level calculated by the RF intensity detection circuit is acquired based on the reflected wave of the harmonic signal corresponding to the second information. If the signal strength level is in the two preset threshold ranges for more than a predetermined stationary determination time, it is determined that the portable device is stationary, and the stationary state Is determined, the output of the high-frequency signal corresponding to the first information is stopped.

  In addition, the communication control method for preventing a relay attack according to the present invention performs wireless communication by radio waves between a portable device possessed by a user of the vehicle and the vehicle, and executes a predetermined control operation on the vehicle. A communication control method for preventing a relay attack executed in a portable device applied to a smart keyless entry system, wherein the portable device receives a low-frequency signal output from a vehicle as activation information of a control operation. When the low frequency signal is received via the step and the LF receiving circuit, the low frequency signal and the preset data corresponding to the activation information are collated, and when the collation result matches, During the second step of outputting the first information indicating that the matching results match as a high-frequency signal, and during the smart keyless entry operation, the first information A third step of outputting second information different from the information as a high-frequency signal, a fourth step of receiving a reflected wave of a harmonic signal corresponding to the second information, and calculating a signal intensity level of the reflected wave; When the state in which the signal intensity level calculated in the step is within two preset threshold ranges continues for a predetermined stationary determination time or longer, it is determined that the portable device is stationary. There are five steps and a sixth step in which the output of the high-frequency signal corresponding to the first information is stopped while the stationary state is determined by the fifth step.

  According to the present invention, the signal strength of the high frequency signal is monitored while the smart keyless entry operation is not performed, and the wireless response is stopped when it is determined that the portable device is in a stationary state according to the monitoring result. It has. As a result, it is possible to obtain a portable device that can prevent unintended vehicle operation due to a relay attack and a communication control method that prevents a relay attack.

It is a block diagram of the vehicle equipment 1 and the portable device 2 which are used by the smart keyless entry which concerns on Embodiment 1 of this invention. It is the figure which showed the specific example of RF transmission in Embodiment 1 of this invention. It is the figure which showed the specific example of RF reception at the time of stationary in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is the figure which showed the transition state of the signal strength level input into a controller. In Embodiment 1 of this invention, it is the figure which showed the specific example of RF reception in the state which the human body which carried the portable device moved from the stationary state. In Embodiment 1 of this invention, it is the figure which showed the specific example of the stationary determination performed with a controller. It is the figure which showed the structure different from FIG. 1 of the portable device in Embodiment 1 of this invention. It is the figure which showed the structure of the portable machine in Embodiment 2 of this invention. It is the figure which showed the structure different from FIG. 8 of the portable device in Embodiment 2 of this invention. In Embodiment 3 of this invention, it is the figure which showed the specific example of RF reception when it becomes a stationary state again after becoming a movement state. In Embodiment 3 of this invention, it is the figure which showed the transition state of the signal strength level input into a controller. It is the figure which showed the time change of the signal strength level in Embodiment 3 of this invention, and the time change of the moving average of a signal strength level. In Embodiment 3 of this invention, it is the figure which showed the specific example of the stationary determination performed with a controller. In Embodiment 4 of this invention, it is a figure for demonstrating the noise level by the repeater using the amplifier of high gain. It is a figure which shows the monitoring result of the signal strength level at the time of RF signal OFF in Embodiment 4 of this invention. In Embodiment 4 of this invention, it is the figure which showed the specific example which determines whether the relay attack is performed using the signal strength level at the time of RF signal OFF. It is the illustration figure which showed the positional relationship of a vehicle and a portable machine in the state where a smart keyless entry does not operate | move. It is an illustration figure when the relay attack using a repeater is performed with respect to the positional relationship of FIG.

  Hereinafter, preferred embodiments of a portable device and a communication control method for preventing a relay attack according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an in-vehicle device 1 and a portable device 2 used in the smart keyless entry according to Embodiment 1 of the present invention. The in-vehicle device 1 includes a switch 11, a controller 12, an LF transmitter 13, an LF transmission antenna 14, an RF receiver 15, and an RF reception antenna 16.

  On the other hand, the portable device 2 includes a controller 21, an RF transmitter 22, an RF transmission antenna 23, an RF intensity detector 24, an RF reception antenna 25, an LF receiver 26, and an LF reception antenna 27.

  In smart keyless entry operation, the following two-way communication is performed. That is, radio waves are radiated from the LF transmitting antenna 14 by pressing the switch 11 on the in-vehicle device 1 side. On the other hand, the LF reception antenna 27 on the portable device 2 side receives the radio wave radiated from the LF transmission antenna 14 and radiates the radio wave from the RF transmission antenna 23 to respond.

  Next, the operation will be described in detail. The controller 12 identifies that the switch 11 has been pressed when the switch 11 on the in-vehicle device 1 side is pressed, for example, when the port state changes from High to Low. The controller 12 then sends information indicating that the switch 11 has been pressed to the LF transmitter 13 as, for example, a preset binary data (H, L) string.

  The LF transmitter 13 modulates the binary data string and outputs a low-frequency signal such as an LF (Lower Frequency) band binary ASK (Amplitude Shift Keying) modulated wave. The low frequency signal output from the LF transmitter 13 is radiated to the space as a radio wave via the LF transmission antenna 14.

  The emitted low frequency signal is received by the LF receiving antenna 27 of the portable device 2 and input to the LF receiver 26. The LF receiver 26 demodulates the low frequency signal and outputs binary data to the controller 21.

  The controller 21 collates the binary data string registered in advance with the demodulated binary data. If both data match, the controller 21 sends, for example, a preset binary data (H, L) sequence to the RF transmitter 22 as data indicating that they match.

  The RF transmitter 22 modulates a binary data string, which is data indicating that they match, and outputs it as a high-frequency signal such as a UHF (Ultra High Frequency) band binary FSK (Frequency Shift Keying) modulated wave, for example. The high frequency signal output from the RF transmitter 22 is radiated to the space as a radio wave via the RF transmission antenna 23.

  The high-frequency signal radiated to the space is received by the RF receiving antenna 16 of the in-vehicle device 1 and input to the RF receiver 15. The RF receiver 15 demodulates the high frequency signal and outputs binary data to the controller 12.

  The controller 12 collates the received binary data with an identification signal registered in advance. Then, if the verification is correct, the controller 12 performs, for example, an operation such as unlocking the door lock on the driver's seat as the operation corresponding to the switch 11.

  Here, while the smart keyless entry operation as described above is not performed, the controller 21 outputs repeated data of a binary data string, for example. Then, the RF transmitter 22 performs modulation corresponding to the binary data.

  Note that the RF transmitter 22 may perform FSK modulation on the modulated data string as, for example, fixed data of H or L, and output a CW (Continuous Wave) signal.

  The high frequency signal is radiated to the space as a radio wave via the RF transmission antenna 23. The radio wave radiated to the space is received by the RF receiving antenna 25 and input to the RF intensity detector 24.

  The RF intensity detector 24 converts the received high frequency signal into a signal intensity level. For the conversion to the signal strength level, for example, a diode detection method, a square detection method, or the like is used.

  The converted signal intensity level is input to the controller 21 and stored as data. FIG. 2 is a diagram showing a specific example of RF transmission in the first embodiment of the present invention. In order to reduce current consumption, the controller 21 may perform control so that the high-frequency signal is intermittently turned on and off when data is repeatedly output as shown in FIG. In this case, the controller 21 controls the RF intensity detector 24 so as to detect the signal intensity level when transmission is ON.

  Here, the signal intensity level will be supplementarily described. FIG. 3 is a diagram showing a specific example of RF reception at rest in Embodiment 1 of the present invention. A case where the surrounding environment including the human body 5 does not change is considered, for example, a case where it is stationary as shown in FIG. The relationship between the portable device 2 and the human body 5 is indicated by a relative position with respect to the portable device 2. In this case, the radio wave radiated from the RF transmission antenna 23 reaches the human body 5 and is reflected by the human body 5. The reflected radio wave is received by the RF receiving antenna 25.

  FIG. 4 is a diagram showing a transition state of the signal intensity level input to the controller 21 in the first embodiment of the present invention. When the human body 5 is stationary and the surrounding environment does not change, the signal intensity level input to the controller 21 is stable, for example, as in the section (a) in FIG.

  Next, FIG. 5 is a diagram illustrating a specific example of RF reception in a state where the human body 5 carrying the portable device 2 has moved from a stationary state in Embodiment 1 of the present invention. Consider a case in which the portable device 2 is moving together with the human body 5 from the stationary state shown in FIG. 3, for example, as shown in FIG. In this case, as in the state 1 in FIG. 5A, the radio wave radiated from the RF transmitting antenna 23 reaches the human body 5 and is reflected. However, the RF receiving antenna 25 has a distance and phase different from those in FIG. Will be received.

  Further, during the movement, the relationship between the portable device 2 and the human body 5 changes as in the state 2 in FIG. For this reason, the signal intensity level changes, for example, as in the section (b) in FIG. Thus, as shown in the state 1 in FIG. 5A and the state 2 in FIG. 5B, the relationship between the portable device 2 and the human body 5 changes every moment while the human body 5 is moving.

  After that, when the movement is finished and the stationary state as shown in FIG. 3 is returned, the signal intensity level is the same as that in the section (a) as in the section (c) in FIG. Will return to the value. As described above, since the reflected wave from the surrounding environment is received by the RF receiving antenna 25, the signal intensity level changes according to the surrounding environment.

  FIG. 6 is a diagram illustrating a specific example of stillness determination executed by the controller 21 in the first embodiment of the present invention. As shown in FIG. 6, for example, when two threshold values are set as A and B, the controller 21 determines that the signal strength level is within the range of the threshold values A and B, and determines that it is in a stationary state. In this case, it can be determined that the vehicle is moving.

  Usually, the user of the smart keyless entry system operates while moving so as to approach the vehicle 1. Therefore, when it is determined that the controller 21 is in a stationary state continuously, for example, for 5 seconds, the controller 21 repeats despite the user being stationary at a position away from the vehicle 1. 3, it is determined that a relay attack may be performed. When it is determined that the state is a continuous stationary state, the controller 21 is set so as not to return an RF response in the smart keyless entry operation.

  Therefore, as shown in FIG. 18, even when a relay attack that relays radio waves is executed and a low-frequency signal is received by the portable device 2 via the repeater 3, In an environment where 2 is determined to be in a stationary state, a configuration in which an RF response signal is not returned from the portable device 2 can be realized. As a result, it is possible to prevent unintended vehicle operation due to the relay attack.

  In the first embodiment, the frequency of smart keyless entry and the frequency of RF intensity detection are the same, but different frequency bands may be used. FIG. 7 is a diagram showing a configuration different from FIG. 1 of the portable device 2 according to Embodiment 1 of the present invention. As shown in FIG. 7, the portable device 2 may employ a configuration further including an RF transmitter 28 and an RF transmission antenna 29, and may use different frequencies for the smart keyless entry frequency and the RF intensity detection frequency.

Embodiment 2. FIG.
FIG. 8 is a diagram showing the configuration of the portable device 2 according to Embodiment 2 of the present invention. The portable device 2 according to the second embodiment includes the RF transmitting antenna 23 and the RF receiving antenna 25 in FIG. More specifically, in the second embodiment, a directional coupler 32 is provided at the output of the RF transmitter 22, and an RF antenna 31 and an RF intensity detector 24 are provided at the output of the directional coupler 32. Yes.

  Therefore, the operation of the RF antenna 31 and the directional coupler 32 newly introduced in the second embodiment will be mainly described below. Other components are the same as those in the first embodiment.

  The high frequency signal output from the RF transmitter 22 is input to the directional coupler 32. The directional coupler 32 may be anything as long as it can separate the transmission wave from the RF transmitter 22 and the reflected wave acquired via the RF antenna 31. The directional coupler 32 outputs the high frequency signal received from the RF transmitter 22 to the RF antenna 31. Further, the directional coupler 32 outputs the reflected wave received via the RF antenna 31 to the RF intensity detector 24.

  In the first embodiment, two RF transmitting antennas 23 and RF receiving antennas 25 are provided as RF antennas. On the other hand, in the second embodiment, by providing the directional coupler 32 described above, it is possible to make one of the RF antennas 31 for both transmission and reception.

  Even in such a configuration, even when a relay attack that relays radio waves is executed and a low-frequency signal is received, the RF response signal should not be returned as in the first embodiment. it can. As a result, it is possible to prevent unintended vehicle operation due to the relay attack.

  In the second embodiment, the frequency of smart keyless entry and the frequency of RF intensity detection are the same, but different frequency bands may be used. FIG. 9 is a diagram showing a configuration different from FIG. 8 of portable device 2 according to Embodiment 2 of the present invention. As shown in FIG. 9, the portable device 2 employs a configuration in which the RF transmission antenna 23 and the RF antenna 31 are provided separately. By adopting such a configuration, the frequency for smart keyless entry by the RF transmitter 22 and the RF transmission antenna 23 and the frequency for RF intensity detection by the RF antenna 31 and the RF transmitter 33 can be made different.

Embodiment 3 FIG.
In the third embodiment, the case where the surrounding environment changes will be described in detail. For example, let us consider a case where the relative positional relationship between the portable device 2 and the human body 5 shifts from a stationary state as shown in FIG. 3 to a moved state as shown in FIG. FIG. 10 is a diagram illustrating a specific example of RF reception in the third embodiment of the present invention when the mobile device enters the stationary state after entering the moving state. FIG. 11 is a diagram showing a transition state of the signal intensity level input to the controller 21 in Embodiment 3 of the present invention.

  In FIG. 10, the smartphone 6 is illustrated along with the portable device 2. In FIG. 11, the RF reception waveforms in the section (a) before movement and the section (b) during movement are the same as the waveforms described in FIG. Therefore, the explanation will be focused on the section (c) after the movement is completed.

  As shown in FIG. 10, consider a case in which the portable device 2 receives reflected waves from both the human body 5 and the smartphone 6. In the section (c) after the end of the movement, the transmitted wave reaches the human body 5 and is reflected by the human body 5, and since the smartphone 6 is present, the transmitted wave also reaches the smartphone 6 and is reflected by the smartphone 6. The reflected wave from the smartphone 6 arrives at the human body 5, is reflected by the human body 5, and is input to the RF receiving antenna 25 of the portable device 2.

  In this way, a combined wave of reflected waves from the human body 5 and the smartphone 6 is received by the RF receiving antenna 25. For this reason, for example, the signal intensity level becomes a stable value at a value like the section (c) in FIG. 11, and is different from the stable value in the section (a) before the movement.

とした場合、図１２のようなデータが得られる。 FIG. 12 is a diagram showing a time change of the signal intensity level and a time change of the moving average of the signal intensity level in the third embodiment of the present invention. Specifically, the signal strength is St (t), and the moving average of the signal strength is

In such a case, data as shown in FIG. 12 is obtained.

  FIG. 13 is a diagram showing a specific example of stillness determination executed by controller 21 in Embodiment 3 of the present invention. In FIG. 6 in the first embodiment, the controller 21 performs the stillness determination using St (t) as the signal intensity level. On the other hand, in the third embodiment, the following St ′ (t) is introduced as a stationary determination signal in consideration of the fact that the stable values of the sections (a) and (c) are different. To do.

  As illustrated in FIG. 13, by using St ′ (t), the controller 21 can determine the first embodiment even if the stable values of the section (a) and the section (c) are different. Similarly, if the signal intensity level is within the range of the thresholds A and B, it can be determined that the camera is stationary.

  Usually, the user of the smart keyless entry system operates while moving so as to approach the vehicle 1. Therefore, when it is determined that the controller 21 is in a stationary state continuously, for example, for 5 seconds, the controller 21 repeats despite the user being stationary at a position away from the vehicle 1. 3, it is determined that a relay attack may be performed. When it is determined that the state is a continuous stationary state, the controller 21 is set so as not to return an RF response in the smart keyless entry operation.

  Therefore, as shown in FIG. 18, even when a relay attack that relays radio waves is executed and a low-frequency signal is received by the portable device 2 via the repeater 3, In an environment where 2 is determined to be in a stationary state, a configuration is provided in which an RF response signal is not returned from the portable device 2. As a result, it is possible to prevent unintended vehicle operation due to the relay attack.

Embodiment 4 FIG.
In the fourth embodiment, for example, a defense method against a relay attack in a situation where the portable device 2 is further away from the vehicle 1 by several tens of meters will be described.

  In order to perform a relay attack in a situation where the portable device 2 is further away from the vehicle 1 by several tens of meters, when the amplification type repeater 3 is used, the vehicle 1 far away is For operation, a high gain amplifier is used in the repeater 3.

  FIG. 14 is a diagram for explaining the noise level due to repeater 3 using an amplifier with a high gain in the fourth embodiment of the present invention. 14A shows the noise level when there is no amplification due to the gain of the repeater 3, and FIG. 14B shows the noise level when there is amplification due to the gain of the repeater 3. FIG.

  When amplifying with an amplifier, the noise level increases over a wide band as shown in FIG. Therefore, the controller 21 changes the stillness determination time by monitoring the fluctuation of the noise level.

  A specific operation for changing the stillness determination time based on the determination result of the noise level will be described next. At times other than the smart keyless entry operation, the controller 21 performs control so that the RF signal is intermittently turned ON and OFF as shown in FIG. The operation for determining the stationary state when the RF signal is ON is as described above.

  The controller 21 according to the fourth embodiment acquires signal intensity level data from the RF intensity detector 24 even when the RF signal is OFF. FIG. 15 is a diagram showing a monitoring result of the signal intensity level when the RF signal is OFF in Embodiment 4 of the present invention. For example, as shown in FIG. 15, the signal strength level when the RF signal is OFF results in an increase in the noise level during the relay attack.

  FIG. 16 is a diagram showing a specific example of determining whether or not a relay attack is performed using the signal strength level when the RF signal is OFF in the fourth embodiment of the present invention. For example, as shown in FIG. 16, when the threshold value is C, the controller 21 can determine that the relay attack has occurred if the signal intensity level when the RF signal is OFF is equal to or higher than the threshold value C.

  When the controller 21 determines that the relay attack is being performed, the controller 21 sets the stillness determination period used when the RF signal is turned on, for example, as short as 5 sec to 1 sec. Then, the controller 21 is set so as not to return the RF response in the smart keyless entry operation when the stationary state continues for 1 sec or more continuously.

  In the fourth embodiment, one threshold is used when the RF signal is OFF, but a plurality of thresholds may be set. In this case, the controller 21 can set different stillness determination periods according to the detection result of the noise level for each threshold value.

  Therefore, it is possible to realize a configuration in which the signal intensity level when the RF transmission is OFF can be monitored and the stillness determination can be performed early according to the monitoring result. As a result, a relay attack that relays radio waves is executed, and even when a low frequency signal is received by the portable device 2 via the repeater 3, it is possible to prevent an RF response signal from being returned earlier. Unintended vehicle operation due to relay attack can be prevented.

  DESCRIPTION OF SYMBOLS 1 In-vehicle apparatus, 2 portable apparatus, 3 repeater, 6 smart phone, 11 switch, 12 controller, 13 LF transmitter, 14 LF transmission antenna, 15 RF receiver, 16 RF reception antenna, 21 controller, 22 RF transmitter , 23 RF transmit antenna, 24 RF intensity detector, 25 RF receive antenna, 26 LF receiver, 27 LF receive antenna, 28 RF transmitter, 29 RF transmit antenna, 31 RF antenna, 32 directional coupler, 33 RF transmit vessel.

The portable device according to the present invention is applied to a smart keyless entry system that performs radio communication by radio waves between a portable device possessed by a user of the vehicle and the vehicle and executes a predetermined control operation on the vehicle. LF receiver circuit that receives a low-frequency signal output from the vehicle as control operation start information, an RF transmitter circuit that transmits a high-frequency signal, and a low-frequency signal received through the LF receiver circuit the case, executes the matching processing between the low frequency signal set in advance in response to the activation information data, if the comparison result is matched, the high frequency of the first information indicating that the verification results match And a controller that outputs the signal as a signal via an RF transmission circuit, receives a reflected wave of the high-frequency signal transmitted from the RF transmission circuit, and calculates the signal intensity level of the reflected wave. Further comprising a circuit, the controller, while not performing the smart keyless entry operation, the second information different from the first information via an RF transmission circuit outputs a high-frequency signal, a high frequency signal corresponding to the second information The signal intensity level calculated by the RF intensity detection circuit based on the reflected wave is acquired, and the state where the signal intensity level is within two preset threshold ranges continues for a predetermined stationary determination time or longer. If it is determined that the portable device is stationary, the output of the high-frequency signal corresponding to the first information is stopped while the portable device is determined to be stationary.

In addition, the communication control method for preventing a relay attack according to the present invention performs wireless communication by radio waves between a portable device possessed by a user of the vehicle and the vehicle, and executes a predetermined control operation on the vehicle. A communication control method for preventing a relay attack executed in a portable device applied to a smart keyless entry system, wherein the portable device receives a low-frequency signal output from a vehicle as activation information of a control operation. a step, when receiving the low frequency signal by the first step, when the low-frequency signal and in response to the activation information performs matching processing with the preset data, the verification result is a match, collation During the second step of outputting the first information indicating that the results coincide with each other as a high-frequency signal, and the smart keyless entry operation, A third step of outputting the second information different from the broadcast as a radio frequency signal, and a fourth step of receiving a reflected wave of the high frequency signal to calculate the signal intensity level of the reflected wave corresponding to the second information, a fourth step When the state in which the signal intensity level calculated in step 2 is within two preset threshold ranges continues for a predetermined stationary determination time or longer, it is determined that the portable device is in a stationary state. While the step is determined to be in the stationary state by the fifth step, there is a sixth step for stopping the output of the high-frequency signal corresponding to the first information.

Claims (4)

A portable device that is applied to a smart keyless entry system that performs radio communication by radio waves between a portable device possessed by a user of the vehicle and the vehicle, and executes a predetermined control operation on the vehicle. ,
An LF receiving circuit that receives a low-frequency signal output from the vehicle as activation information of the control operation;
An RF transmission circuit for transmitting a high-frequency signal;
An RF intensity detection circuit that receives a reflected wave of the high-frequency signal transmitted from the RF transmission circuit and calculates a signal intensity level of the reflected wave;
When the low-frequency signal is received via the LF receiver circuit, the low-frequency signal and a preset data corresponding to the activation information are collated, and the collation result matches. A controller that outputs, as the high-frequency signal, the first information indicating that the matching result is matched via the RF transmission circuit, and
An RF intensity detection circuit that receives a reflected wave of the high-frequency signal transmitted from the RF transmission circuit and calculates a signal intensity level of the reflected wave;
The controller is
While the smart keyless entry operation is not performed, the second information different from the first information is output as a high frequency signal via the RF transmission circuit,
The signal intensity level calculated by the RF intensity detection circuit based on the reflected wave of the harmonic signal corresponding to the second information is acquired, and the signal intensity level falls within two preset threshold ranges However, if it continues for a predetermined stationary determination time or more, it is determined that the portable device is in a stationary state,
A portable device that stops outputting a high-frequency signal corresponding to the first information while it is determined to be in the stationary state. 2. The portable device according to claim 1, wherein when the second information is output as a high-frequency signal via the RF transmission circuit, the controller performs control so as to be an intermittent signal that is periodically turned on and off. The controller outputs the signal intensity level calculated by the RF intensity detection circuit at the OFF time when outputting the second information as a high-frequency signal to be the intermittent signal via the RF transmission circuit. It is acquired as a noise level, variably set so that the stillness determination time becomes shorter as the value of the noise level is larger, and it is determined whether or not the portable device is in a stationary state.
The portable device according to claim 2. It is executed by a portable device applied to a smart keyless entry system that performs radio communication by radio waves between a portable device possessed by a user of the vehicle and the vehicle, and executes a predetermined control operation on the vehicle. A communication control method for preventing relay attacks,
In the portable device,
A first step of receiving a low-frequency signal output from the vehicle as activation information of the control operation;
When the low-frequency signal is received via the LF receiver circuit, the low-frequency signal and a preset data corresponding to the activation information are collated, and the collation result matches. A second step of outputting, as a high-frequency signal, first information indicating that the matching results match;
A third step of outputting second information different from the first information as a high-frequency signal while the smart keyless entry operation is not performed;
Receiving a reflected wave of a harmonic signal corresponding to the second information, and calculating a signal intensity level of the reflected wave;
When the state where the signal intensity level calculated in the fourth step is within two preset threshold ranges continues for a predetermined stationary determination time or longer, the portable device is in a stationary state. A fifth step of determining that there is,
A communication control method for preventing a relay attack, comprising: a sixth step of stopping output of a high-frequency signal corresponding to the first information while being determined to be in the stationary state by the fifth step.

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