JP7252829B2 - wireless communication system - Google Patents

Description

The present invention relates to wireless communication technology.

In wireless communication, if it is easy for a third party to spoof and illegally intervene, the reliability is compromised. Conventionally, a spoofing countermeasure using a frame counter is known.

According to spoofing countermeasures using a frame counter, even if an unauthorized device intercepts a data frame sent from a wireless transmitter to a wireless receiver and duplicates the intercepted data frame and attempts to intervene illegally, If a data frame sent from a radio transmitter to a radio receiver arrives at the radio receiver first, a frame counter check on the radio receiver side can prevent unauthorized intervention.

However, if the frame counter included in the intercepted data frame is tampered with by an unauthorized device, the unauthorized intervention cannot be prevented only by checking the frame counter on the wireless receiver side.

Therefore, a countermeasure against spoofing using a frame counter can be strengthened by adding an authentication code (for example, CMAC: Cipher-based Message Authentication Code) generated based on a frame counter and a security key to a data frame. This enhancement prevents unauthorized intervention even if an unauthorized device modifies the frame counter contained in the intercepted data frames.

For example, Japanese Unexamined Patent Application Publication No. 2002-200002 discloses a countermeasure against spoofing in wireless communication.

JP 2007-13366 A

The spoofing countermeasures using the frame counter described above and the strengthening measures described above have the following weaknesses. If a data frame sent from a wireless transmitter to a wireless receiver fails to reach the wireless receiver, an unauthorized device intercepts the data frame sent from the wireless transmitter to the wireless receiver, and duplicates the intercepted data frame. and the unauthorized device attempts unauthorized intervention, the unauthorized intervention will be successful.

An object of the present invention is to improve the reliability of wireless communication in view of the above situation.

A wireless transmitter disclosed in this specification includes: a first management unit that manages a transmission frame counter; a first wireless communication unit that transmits a first data frame including the transmission frame counter to a wireless receiver; and the first wireless communication unit, upon receiving an acknowledgment returned from the wireless receiver in response to the first data frame, transmits a second data frame including the transmission frame counter to the wireless receiver. and the first management unit sets the value of the transmission frame counter included in the first data frame and the value of the transmission frame counter included in the second data frame to different values (first configuration ). Note that the transmission form of the first data frame is not particularly limited. Therefore, for example, one first data frame may be divided and transmitted in the form of a plurality of divided data. Similarly, the transmission form of the second data frame is not particularly limited. Therefore, for example, one second data frame may be divided and transmitted in the form of a plurality of divided data.

Further, in the radio transmitter having the first configuration, either one of the payload portion of the first data frame and the payload portion of the second data frame is dummy data (second configuration), good too.

Further, in the wireless transmitter having the first configuration, the payload portion of the first data frame is the first half divided data, and the payload portion of the second data frame is the second half divided data (third configuration). There may be.

Further, in the wireless transmitter having the first configuration, the payload section of the first data frame and the payload section of the second data frame may be the same data (fourth configuration).

In addition, the wireless transmitter having any one of the first to fourth configurations above includes a confirmation unit for confirming an authentication code included in the acknowledgment, and the first wireless communication unit receives the acknowledgment, The configuration (fifth configuration) may be such that the second data frame is transmitted to the wireless receiver.

Further, in the wireless transmitter having any one of the first to fifth configurations, an acknowledgment determination unit is provided, the first management unit manages an acknowledgment received frame counter, and the acknowledgment determination unit controls the acknowledgment A configuration for determining whether or not the first wireless communication unit has normally received the acknowledgment based on the magnitude relationship between the acknowledgment transmission frame counter included in the response and the acknowledgment reception frame counter (sixth configuration) may be

A wireless receiver disclosed in this specification includes a second management unit that manages a received frame counter, a second wireless communication unit that receives a first data frame and a second data frame, and the first data frame. a determination unit that determines whether the second wireless communication unit has normally received the first data frame based on the magnitude relationship between the transmission frame counter and the reception frame counter included in the second When the determination unit determines that the second wireless communication unit has received the first data frame normally, the management unit updates the received frame counter, and the second wireless communication unit receives the determination unit. If the second wireless communication unit is determined to have received the first data frame normally by and the updated received frame counter, the second wireless communication unit determines whether or not the second data frame is normally received, and the determination unit determines whether the second wireless communication unit receives the A configuration for processing reception of the first data frame and the second data frame as normal data reception only when it is determined that the first data frame and the second data frame have been received normally (a seventh configuration ).

Further, in the radio receiver having the seventh configuration, the acknowledgment may include an authentication code (eighth configuration).

Further, in the radio receiver having the seventh or eighth configuration, the authentication code included in the first data frame may be included in the payload portion of the acknowledgment (ninth configuration).

In the radio receiver having any one of the seventh to ninth configurations, the second management unit manages an acknowledgment transmission frame counter, and the acknowledgment includes the acknowledgment transmission frame counter (the tenth configuration).

The radio communication system disclosed in this specification includes a radio transmitter having any one of the first to sixth configurations and a radio receiver having any one of the seventh to ninth configurations ( 11th configuration). However, when the radio communication system includes the radio transmitter having the fifth configuration, the radio communication system includes the radio receiver having the eighth or ninth configuration. Further, when the radio communication system includes the radio transmitter having the sixth configuration, the radio communication system includes the radio receiver having the tenth configuration.

The smart lock disclosed in this specification has a configuration (twelfth configuration) including the wireless receiver according to any one of the seventh to ninth configurations.

The alarm device disclosed in this specification has a configuration (thirteenth configuration) including the wireless receiver according to any one of the seventh to ninth configurations.

A smart meter disclosed in this specification has a configuration (a fourteenth configuration) including the wireless receiver according to any one of the seventh to ninth configurations.

According to the wireless communication technology disclosed in this specification, unauthorized intervention by impersonation by a third party becomes difficult, so reliability can be improved.

FIG. 1 shows a schematic configuration of a radio communication system according to the first embodiment; FIG. 2 is a diagram for explaining an outline of a communication sequence of the wireless communication system according to the first embodiment; FIG. FIG. 4 is a diagram for explaining a modification of the communication sequence of the wireless communication system according to the first embodiment; FIG. 2 is a diagram for explaining an outline of a communication sequence of the wireless communication system according to the first embodiment; FIG. FIG. 2 is a diagram for explaining an outline of a communication sequence of the wireless communication system according to the first embodiment; FIG. A diagram showing a schematic configuration of a wireless communication system according to a second embodiment. A diagram for explaining an outline of a communication sequence of a wireless communication system according to a second embodiment. Conceptual diagram showing a configuration example of a data frame FIG. 4 is a conceptual diagram showing a configuration example of an acknowledgment according to the first data frame in the second embodiment; A diagram for explaining an outline of a communication sequence when a data frame is divided and transmitted. A diagram for explaining an outline of a communication sequence when a data frame is divided and transmitted. Diagram for explaining an outline of a communication sequence when retransmitting a data frame when no acknowledgment has been received Schematic external view of smart lock, alarm, and smart meter

<First embodiment>
FIG. 1 is a diagram showing a schematic configuration of a radio communication system SYS1 (hereinafter abbreviated as "radio communication system SYS1") according to the first embodiment. A radio communication system SYS1 comprises a radio transmitter 1 and a radio receiver 2 . The communication method between the wireless transmitter 1 and the wireless receiver 2 is not particularly limited as long as it is a communication method in which a data frame is transmitted from the wireless transmitter 1 and an acknowledgment is returned when the wireless receiver 2 receives the data frame. For example, a MAC protocol conforming to IEEE802.15.4 can be used.

The radio transmitter 1 includes a radio communication section 11 and a control section 12 .

The wireless communication unit 11 includes a high-frequency circuit that modulates a data frame into a high-frequency signal, an antenna that converts the high-frequency signal into a radio wave, and the like. Therefore, the data frame is transmitted from the radio transmitter 1 to the radio receiver 2 while being modulated with a high frequency signal.

The control unit 12 controls the radio communication unit 11 . The control unit 12 includes a management unit 12A and a data frame generation unit 12B. The management unit 12A manages the transmission frame counter. The data frame generator 12B generates data frames. A data frame generated by the data frame generator 12B includes a transmission frame counter and an authentication code generated based on the security key. The security key used by the data frame generator 12B is stored by the controller 12. FIG. An authorization code may be generated, for example, based on a transmitted frame counter in addition to the security key. For example, a microcomputer can be used as the control unit 12 .

The radio receiver 2 includes a radio communication section 21 and a control section 22 .

The wireless communication unit 21 includes an antenna that converts a high frequency signal into a radio wave, a high frequency circuit that demodulates the high frequency signal into a data frame, and the like.

The control section 22 controls the wireless communication section 21 . The control unit 22 includes a management unit 22A, a determination unit 22B, and a confirmation unit 22C. The management unit 22A manages the reception frame counter. The determination unit 22B determines whether or not the wireless communication unit 21 has normally received the data frame. The confirmation unit 22C confirms whether or not the authentication code included in the data frame is a legitimate authentication code based on the security key. The security key used by the confirmation unit 22C is stored by the control unit 22. FIG. For example, when the authentication code is generated based on the transmission frame counter and the payload part included in the data frame in addition to the security key, the confirmation unit 22C uses the transmission frame counter and the payload part included in the data frame and the control unit Based on the security key stored by 22, it is confirmed whether the authentication code contained in the data frame is a valid authentication code. A microcomputer, for example, can be used as the control unit 22 .

FIG. 2A is a diagram for explaining an outline of a communication sequence of the radio communication system SYS1. At the start of the communication sequence shown in FIG. 2A, the management unit 12A manages the value of the transmission frame counter as "3", and the management unit 22A manages the value of the reception frame counter as "2".

When the wireless transmitter 1 receives a data transmission instruction from a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1), the data frame generator 12B is managed by the manager 12A. generating a first data frame including a transmitted frame counter that is The wireless communication unit 11 modulates and transmits the first data frame. When the wireless communication unit 11 transmits the first data frame, the management unit 12A updates the value of the transmission frame counter to "4". In this embodiment, the transmission frame counter and the reception frame counter are each incremented by one when updated, but the increment value is not limited to one. Note that, unlike the present embodiment, the initial values of the transmission frame counter and the reception frame counter may be made sufficiently large so that the transmission frame counter and the reception frame counter are decremented when they are updated. Further, in the present embodiment, the transmission frame counter is updated after the data frames (the first data frame and the second data frame) are generated. The transmission frame counter may be updated before the first data frame, second data frame) is generated. That is, the timing of updating the transmission frame counter is not limited, and the transmission frame counter is adjusted so that the value of the transmission frame counter included in the first data frame and the value of the transmission frame counter included in the second data frame are different values. It should be updated.

When the wireless communication unit 21 receives the first data frame, the determination unit 22B determines whether the wireless communication unit 21 normally receives the first data frame based on the magnitude relationship between the transmission frame counter and the reception frame counter included in the first data frame. It determines whether or not it has been received. Specifically, the determination unit 22B determines that the wireless communication unit 21 has successfully received the first data frame when the transmission frame counter included in the first data frame is greater than the reception frame counter.

If the determination unit 22B determines that the wireless communication unit 21 has normally received the first data frame, the management unit 22A updates the value of the received frame counter to "3", and the wireless communication unit 21 Send a response. However, if the confirmation unit 22C confirms that the authentication code included in the first data frame is not a valid authentication code, the first data frame is discarded and the wireless communication unit 21 does not transmit an acknowledgment. In this way, when an abnormality is confirmed by the confirmation unit 22C and the wireless communication unit 21 does not transmit an acknowledgment, the wireless communication unit 21 may not transmit anything. can be

When the radio communication unit 11 receives the acknowledgment, the data frame generation unit 12B generates a second data frame including the transmission frame counter managed by the management unit 12A, and the radio communication unit 11 generates the second data frame. Modulate and transmit.

When the wireless communication unit 11 transmits the second data frame, the management unit 12A updates the value of the transmission frame counter to "5".

When the wireless communication unit 21 receives the second data frame, the determination unit 22B determines whether the wireless communication unit 21 normally receives the second data frame based on the magnitude relationship between the transmission frame counter and the reception frame counter included in the second data frame. It determines whether or not it has been received. Specifically, when the transmission frame counter included in the second data frame is greater than the reception frame counter, the determination unit 22B determines that the wireless communication unit 21 has successfully received the second data frame.

If the determination unit 22B determines that the wireless communication unit 21 has normally received the second data frame, the management unit 22A updates the value of the received frame counter to "4", and the wireless communication unit 21 Send a response. However, if the confirmation unit 22C confirms that the authentication code included in the second data frame is not a valid authentication code, the second data frame is discarded and the wireless communication unit 21 does not transmit an acknowledgment. In this way, when an abnormality is confirmed by the confirmation unit 22C and the wireless communication unit 21 does not transmit an acknowledgment, the wireless communication unit 21 may not transmit anything. can be

Only when the determination unit 22B determines that the wireless communication unit 21 has normally received the first data frame and the second data frame, the control unit 22 allows the reception of the first data frame and the second data frame to be performed normally. Process as data reception. For example, the control unit 22 controls a device (for example, a wireless A data reception notification is output to a microcomputer or the like accessible to the receiver 2 . However, if the first data frame or the second data frame is discarded, the control unit 22 does not treat the reception of the first data frame and the second data frame as normal data reception.

When the wireless communication unit 11 receives an acknowledgment after transmitting the second data frame, the control unit 12 sends a transmission success notification to a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1). to output

Here, the case where the first data frame does not reach the wireless receiver 2 will be described with reference to FIG. At the start of the communication sequence shown in FIG. 3, the management unit 12A manages the value of the transmission frame counter as "3", and the management unit 22A manages the value of the reception frame counter as "2".

When the wireless transmitter 1 receives a data transmission instruction from a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1), the data frame generator 12B is managed by the manager 12A. generating a first data frame including a transmitted frame counter that is The wireless communication unit 11 modulates and transmits the first data frame. When the wireless communication unit 11 transmits the first data frame, the management unit 12A updates the value of the transmission frame counter to "4".

In order to impersonate the wireless transmitter 1, the unauthorized device intercepts the first data frame and duplicates and uses the first data frame. When the wireless communication unit 21 receives the first data frame transmitted from the unauthorized device, the determination unit 22B determines whether the wireless communication unit 21 It is determined whether or not the first data frame has been successfully received. Specifically, the determination unit 22B determines that the wireless communication unit 21 has successfully received the first data frame when the transmission frame counter included in the first data frame is greater than the reception frame counter.

If the determination unit 22B determines that the wireless communication unit 21 has normally received the first data frame, the management unit 22A updates the value of the received frame counter to "3", and the wireless communication unit 21 Send a response. Since the first data frame transmitted from the unauthorized device is a copy of the first data frame transmitted from the wireless transmitter 1, the authentication code contained in the first data frame transmitted from the unauthorized device is valid authentication. is the code.

Since the first data frame does not reach the radio receiver 2 , the acknowledgment does not reach the radio transmitter 1 . Since the radio transmitter 1 does not receive an acknowledgment for the first data frame, it does not transmit the second data frame. Since the wireless transmitter 1 does not transmit the second data frame, unauthorized devices cannot intercept the second data frame and duplicate the second data frame in order to impersonate the wireless transmitter 1 . Also, since the unauthorized device does not know the security key stored in the control unit 12, it cannot create the second data frame containing the correct authentication code.

As a result, the control unit 22 does not process reception of the first data frame as normal data reception. Further, when a timeout occurs, the control unit 12 outputs a transmission failure notification to a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1, etc.). Thus, the wireless communication system SYS1 can prevent unauthorized intervention by impersonating the wireless transmitter 1 by an unauthorized device. Therefore, according to the wireless communication system SYS1, reliability can be improved.

Note that, unlike the present embodiment, the data frame may not include the authentication code. In this case, although it is possible for an unauthorized device to tamper with the transmission frame counter and create a second data frame, it is possible to prevent a situation in which unauthorized intervention succeeds simply by duplicating the data frame. Therefore, reliability can be improved.

Next, with reference to FIG. 4, the possibility that unauthorized intervention will succeed when the first data frame does not reach the wireless receiver 2 will be described. At the start of the communication sequence shown in FIG. 4, the management unit 12A manages the value of the transmission frame counter as "3", and the management unit 22A manages the value of the reception frame counter as "2".

When the wireless transmitter 1 receives a data transmission instruction from a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1), the data frame generator 12B is managed by the manager 12A. generating a first data frame including a transmitted frame counter that is The wireless communication unit 11 modulates and transmits the first data frame. When the wireless communication unit 11 transmits the first data frame, the management unit 12A updates the value of the transmission frame counter to "4".

The rogue device intercepts the first data frame and impersonates the wireless receiver 2 and sends back an acknowledgment to the wireless transmitter 1 .

When the radio communication unit 11 receives the acknowledgment, the data frame generation unit 12B generates a second data frame including the transmission frame counter managed by the management unit 12A, and the radio communication unit 11 generates the second data frame. Modulate and transmit.

When the wireless communication unit 11 transmits the second data frame, the management unit 12A updates the value of the transmission frame counter to "5".

The rogue device intercepts the second data frame and impersonates the wireless receiver 2 and sends back an acknowledgment to the wireless transmitter 1 .

When the wireless communication unit 11 receives an acknowledgment after transmitting the second data frame, the control unit 12 sends a transmission success notification to a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1). to output

After returning an acknowledgment to the wireless transmitter 1 in response to the second data frame, the unauthorized device duplicates and uses the first and second data frames intercepted in advance to impersonate the wireless transmitter 1 . Since the operation of the wireless receiver 2 after the unauthorized device impersonates the wireless transmitter 1 is the same as in FIG. 2A, the description is omitted.

<Second embodiment>
FIG. 5 is a diagram showing a schematic configuration of a radio communication system SYS2 (hereinafter abbreviated as "radio communication system SYS2") according to the second embodiment. In the second embodiment, the description of the same parts as in the first embodiment will be omitted as appropriate, and the parts different from the first embodiment will be mainly described.

The wireless communication system SYS2 is a wireless communication system that can prevent unauthorized intervention by impersonating both the wireless receiver 2 and the wireless transmitter 1 by an unauthorized device.

The control unit 12 also includes a confirmation unit 12C and an acknowledgment determination unit 12D in addition to a management unit 12A and a data frame generation unit 12B.

Based on the security key, the confirmation unit 12C confirms whether or not the authentication code included in the acknowledgment corresponding to the first data frame is a valid authentication code. The security key used by the confirmation unit 12C is stored by the control unit 12. FIG. For example, if the authentication code is generated based on not only the security key but also the acknowledgment transmission frame counter and the payload section included in the acknowledgment in response to the first data frame, the verification unit 12C Based on the acknowledgment transmission frame counter and payload part included in the acknowledgment in response and the security key stored by the control unit 12, the authentication code included in the acknowledgment in response to the first data frame is determined to be a regular authentication code. Check whether there is

The management unit 12A also manages an acknowledgment reception frame counter in addition to the transmission frame counter. The management unit 22A also manages an acknowledgment transmission frame counter in addition to the reception frame counter.

The acknowledgment determination unit 12D determines whether or not the wireless communication unit 11 has normally received the acknowledgment corresponding to the first data frame.

FIG. 6 is a diagram for explaining an outline of a communication sequence of the radio communication system SYS2. At the start of the communication sequence shown in FIG. 6, the management unit 12A manages the value of the transmission frame counter as "3" and manages the value of the acknowledgment reception frame counter as "1", and the management unit 22A controls the value of the reception frame counter as "3". It is assumed that the value is managed as "2" and the value of the acknowledgment transmission frame counter is managed as "2".

Note that the acknowledgment corresponding to the first data frame is written as "ACK+" in FIG. 6 because it has a structure including a payload part to which an authentication code and an acknowledgment transmission frame counter are attached.

When the wireless transmitter 1 receives a data transmission instruction from a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1), the data frame generator 12B is managed by the manager 12A. generating a first data frame including a transmitted frame counter that is The wireless communication unit 11 modulates and transmits the first data frame. When the wireless communication unit 11 transmits the first data frame, the management unit 12A updates the value of the transmission frame counter to "4".

When the wireless communication unit 21 receives the first data frame, the determination unit 22B determines whether the wireless communication unit 21 normally receives the first data frame based on the magnitude relationship between the transmission frame counter and the reception frame counter included in the first data frame. It determines whether or not it has been received. Specifically, the determination unit 22B determines that the wireless communication unit 21 has successfully received the first data frame when the transmission frame counter included in the first data frame is greater than the reception frame counter.

If the determination unit 22B determines that the wireless communication unit 21 has normally received the first data frame, the management unit 22A updates the value of the received frame counter to "3", and the wireless communication unit 21 performs the management Send an acknowledgment that includes an acknowledgment sent frame counter maintained by unit 22A. However, if the confirmation unit 22C confirms that the authentication code included in the first data frame is not a valid authentication code, the first data frame is discarded and the wireless communication unit 21 does not transmit an acknowledgment.

When the wireless communication unit 21 transmits an acknowledgment, the management unit 22A updates the value of the acknowledgment transmission frame counter to "3". In this embodiment, the acknowledgment sent frame counter and the acknowledgment received frame counter are each incremented by one when updated, but the increment value is not limited to one. Note that unlike the present embodiment, the initial values of the acknowledgment transmission frame counter and the acknowledgment reception frame counter are set sufficiently large so that the acknowledgment transmission frame counter and the acknowledgment reception frame counter are decremented when they are updated. good too.

When the radio communication unit 11 receives the acknowledgment, the acknowledgment determination unit 12D determines whether the radio communication unit 11 receives the first data frame based on the magnitude relationship between the acknowledgment transmission frame counter and the acknowledgment reception frame counter included in the acknowledgment. determines whether an acknowledgment in response to has been successfully received. Specifically, if the acknowledgment transmission frame counter included in the acknowledgment is greater than the acknowledgment reception frame counter, the acknowledgment determination unit 12D determines whether the wireless communication unit 11 normally sends the acknowledgment corresponding to the first data frame. Determine that it has been received.

If the acknowledgment determination unit 12D determines that the wireless communication unit 11 has normally received the acknowledgment corresponding to the first data frame, the management unit 12A updates the value of the acknowledgment received frame counter to "2". and the wireless communication unit 11 transmits the second data frame. However, if the confirmation unit 12C confirms that the authentication code included in the acknowledgment in response to the first data frame is not a valid authentication code, the wireless communication unit 11 does not transmit the second data frame.

When the wireless communication unit 11 transmits the second data frame, the management unit 12A updates the value of the transmission frame counter to "5".

When the wireless communication unit 21 receives the second data frame, the determination unit 22B determines whether the wireless communication unit 21 normally receives the second data frame based on the magnitude relationship between the transmission frame counter and the reception frame counter included in the second data frame. It determines whether or not it has been received. Specifically, when the transmission frame counter included in the second data frame is greater than the reception frame counter, the determination unit 22B determines that the wireless communication unit 21 has successfully received the second data frame.

If the determination unit 22B determines that the wireless communication unit 21 has normally received the second data frame, the management unit 22A updates the value of the received frame counter to "4", and the wireless communication unit 21 Send a response. However, if the confirmation unit 22C confirms that the authentication code included in the second data frame is not a valid authentication code, the second data frame is discarded and the wireless communication unit 21 does not transmit an acknowledgment.

Acknowledgments in response to the second data frame are general acknowledgments. In other words, unlike the acknowledgment response to the first data frame, the acknowledgment response to the second data frame does not include the payload section to which the authentication code and the acknowledgment transmission frame counter are attached. Note that, unlike the present embodiment, the acknowledgment for the second data frame may also include a payload portion, like the acknowledgment for the first data frame.

When the wireless communication unit 21 transmits an acknowledgment, the management unit 22A updates the value of the acknowledgment transmission frame counter to "4".

Only when the determination unit 22B determines that the wireless communication unit 21 has normally received the first data frame and the second data frame, the control unit 22 allows the reception of the first data frame and the second data frame to be performed normally. Process as data reception. For example, the control unit 22 controls a device (for example, a wireless A data reception notification is output to a microcomputer or the like accessible to the receiver 2 . However, if the first data frame or the second data frame is discarded, the control unit 22 does not treat the reception of the first data frame and the second data frame as normal data reception.

When the wireless communication unit 11 receives an acknowledgment after transmitting the second data frame, the control unit 12 sends a transmission success notification to a device that can access the wireless transmitter 1 (for example, a microcomputer that can access the wireless transmitter 1). to output

<Configuration example of data frame>
FIG. 7 is a conceptual diagram showing a configuration example of a data frame. The data frame has a structure in which a header P1, a payload part P2, a random number P3, a transmission frame counter P4, and an authentication code P5 are arranged in order from the top. Configurations different from the configuration example shown in FIG. 7 include, for example, (1) a configuration without a random number section, (2) a configuration in which a transmission frame counter is located between the header and the payload section, and (3) a transmission frame A configuration in which the counter is included in the header, and (4) a configuration in which at least two of the above (1) to (3) are combined are conceivable.

In the configuration example shown in FIG. 7, the authentication code P5 is CMAC. The authentication code P5 is generated by AES-CMAC (Advanced Encryption Standard Cipher-based Message Authentication Code) using the header P1, the payload part P2, the random number P3, the transmission frame counter P4, and the security key stored in the control unit 12. Calculated. Note that, unlike the present embodiment, the authentication code may be calculated by an algorithm other than AES-CMAC. Algorithms other than AES-CMAC include, for example, CBC-MAC (Cipher Block Chaining Message Authentication Code). Also, unlike the present embodiment, even if the scrambling process is performed by a method such as encrypting part or all of the header and subsequent parts using another security key, or taking an exclusive OR with an arbitrary sequence. good.

Either one of the payload portion P2 of the first data frame and the payload portion P2 of the second data frame may be dummy data. Dummy data preferably contains random numbers. By including random numbers in the dummy data, the security level of the authentication code P5 calculated using the dummy data can be increased.

Further, the data to be transmitted from the radio transmitter 1 to the radio receiver 2 is divided into the first half divided data and the second half divided data, and the payload part P2 of the first data frame is replaced with the first half divided data. may be used as the second half divided data.

Also, the payload part P2 of the first data frame and the payload part P2 of the second data frame may be the same data. In this case, although the security level of the authentication code P5 is lowered, the processing load on the wireless transmitter 1 can be reduced.

Instead of making the random number P3 of the first data frame and the random number P3 of the second data frame the same, by regenerating the random number P3 when generating the second data frame, the authentication code P5 of the second data frame security level can be increased.

<Configuration example of acknowledgment corresponding to first data frame in second embodiment>
FIG. 8 is a conceptual diagram showing a configuration example of an acknowledgment according to the first data frame in the second embodiment. The acknowledgment corresponding to the first data frame in the second embodiment has a header P11, a payload part P12, an acknowledgment transmission frame counter P13, and an authentication code P14 arranged in order from the beginning. Note that, as a configuration different from the configuration example shown in FIG. 8, for example, (1) a configuration in which the acknowledgment transmission frame counter is located between the header and the payload section, and (2) the acknowledgment transmission frame counter is included in the header. and (3) a combination of the above (1) and (2).

In the configuration example shown in FIG. 8, the authentication code P14 is CMAC. The authentication code P14 is calculated by AES-CMAC using the header P11, the payload part P12, the acknowledgment transmission frame counter P13, and the security key stored in the controller 22. FIG.

It is desirable to include the authentication code of the first data frame in the payload portion P12. Thus, in the second embodiment, when the radio transmitter 1 receives an acknowledgment corresponding to the first data frame, whether or not the authentication code included in the payload part P12 matches the authentication code of the first data frame. can be confirmed. This confirmation can ensure that the acknowledgment corresponding to the first data frame really corresponds to the first data frame, thus increasing the security level of the acknowledgment corresponding to the first data frame. .

<When dividing the data frame for transmission>
9 and 10 are diagrams for explaining an outline of a communication sequence when a data frame is divided and transmitted. For example, when the size of the payload portion included in the data frame is large, the wireless transmission unit 1 divides the data frame and transmits the data frame.

9 and 10 show a case where the first data frame is divided into two pieces of divided data ("first DF-1" and "first DF-2" in the figures) in the second embodiment.

FIG. 9 shows a case where the first data frame is simply divided into two pieces of divided data. In this case, the determination unit 22B determines whether or not the wireless communication unit 21 has normally received the first data frame when the two pieces of divided data are complete.

In FIG. 10, the payload part of the first data frame is divided into two, each allocated to two divided data, and each of the two divided data contains a header, a random number, a transmission frame counter, and an authentication code. indicates the case. In this case, the determination unit 22B determines whether or not the wireless communication unit 21 has normally received the first data frame each time it receives the divided data.

<When retransmitting a data frame when no acknowledgment is received>
FIG. 11 is a diagram for explaining an outline of a communication sequence when retransmitting a data frame when an acknowledgment has not been received.

FIG. 11 shows that in the second embodiment, the acknowledgment corresponding to the first data frame does not reach the wireless transmitter 1, and the wireless transmitter 1 retransmits the first data frame, and the acknowledgment corresponding to the first data frame is The second time it reaches the wireless transmitter 1, the acknowledgment corresponding to the second data frame does not reach the wireless transmitter 1, the wireless transmitter 1 retransmits the second data frame, and the acknowledgment corresponding to the second data frame reaches the radio transmitter 1 for the second time.

When the wireless transmitter 1 retransmits a data frame, it may retransmit the same data frame that was transmitted in the past and did not receive an acknowledgment. A data frame with an updated transmission frame counter may be transmitted.

<Application example>
The radio transmitter 1 and radio receiver 2 can be installed in various products.

For example, the wireless receiver 2 can be mounted on the smart lock X1 shown in FIG. 12(a), and the wireless transmitter 1 can be mounted on the control device that controls the smart lock X1. Although the installation location of the smart meter X1 is not particularly limited, it is installed, for example, at the entrance door Y1 of the house as shown in FIG. 12(a).

For example, the wireless receiver 2 can be mounted on the alarm X2 shown in FIG. 12(b), and the wireless transmitter 1 can be mounted on the control device that controls the alarm X2. The alarm X2 includes a sensor Y2 that detects an abnormality, and a speaker Y3 that outputs alarm sounds and alarm messages.

For example, the wireless receiver 2 can be mounted on the smart meter X3 shown in FIG. 12(c), and the wireless transmitter 1 can be mounted on the control device that controls the smart meter X3. The smart meter X3 has a display section Y4 that displays the weighing result. Although the measurement target of the smart meter X3 is not particularly limited, for example, electricity usage, gas usage, and the like can be mentioned. Note that unlike the appearance example shown in FIG. 12(c), a smart meter may be realized by externally attaching the unitized wireless receiver 2 to the meter main body.

<Others>
Various modifications can be made to the various technical features disclosed in this specification without departing from the gist of the technical creation in addition to the above-described embodiments. That is, the above-described embodiments should be considered as examples and not restrictive in all respects, and the technical scope of the present invention is not limited to the above-described embodiments. It is to be understood that a range and equivalents are meant to include all changes that fall within the range.

For example, the radio transmitter 1 is a radio transceiver (first radio transceiver) that also has the same function as the radio receiver 2, and the radio receiver 2 is a radio transceiver that also has the same function as the radio transmitter 1 ( second radio transmitter/receiver).

The first wireless transceiver may separately manage the transmission counter and the acknowledgment transmission counter, or may collectively manage the transmission counter and the acknowledgment transmission counter without distinction. Also, the first wireless transceiver may manage the reception counter and the acknowledgment reception counter separately, or may collectively manage the reception counter and the acknowledgment reception counter without distinguishing between them.

Similarly, the second wireless transceiver may separately manage the transmission counter and the acknowledgment transmission counter, or may collectively manage the transmission counter and the acknowledgment transmission counter without distinction. Also, the second radio transceiver may manage the reception counter and the acknowledgment reception counter separately, or may collectively manage the reception counter and the acknowledgment reception counter without distinguishing between them.

Products to which the above-described first wireless transmitter/receiver is applied are not particularly limited, but are suitable for products that transmit and receive highly confidential data, for example. Examples of products that send and receive highly confidential data include smart locks and smart meters.

1 wireless transmitter 2 wireless receiver 11, 21 wireless communication unit 12, 22 control unit 12A, 22A management unit 12B data frame generation unit 12C, 22C confirmation unit 12D acknowledgment determination unit 22B determination unit SYS1, SYS2 wireless communication system X1 smart Lock X2 Alarm X3 Smart meter

Claims (12)

a first management unit that manages a transmission frame counter;
a first wireless communication unit that transmits a first data frame including the transmission frame counter to a wireless receiver;
an acknowledgment determination unit ;
When the first wireless communication unit receives an acknowledgment returned from the wireless receiver in response to the first data frame, the first wireless communication unit transmits a second data frame including the transmission frame counter to the wireless receiver,
The first management unit sets the value of the transmission frame counter included in the first data frame and the value of the transmission frame counter included in the second data frame to different values ,
the transmitted frame counter is always incremented or always decremented when updated;
The first management unit manages an acknowledgment received frame counter,
The acknowledgment determination unit determines whether or not the first wireless communication unit has normally received the acknowledgment based on the magnitude relationship between the acknowledgment transmission frame counter and the acknowledgment reception frame counter included in the acknowledgment. Judging, radio transmitter. 2. The wireless transmitter of claim 1, wherein one of the payload portion of the first data frame and the payload portion of the second data frame is dummy data. 2. The radio transmitter according to claim 1, wherein the payload portion of said first data frame is first half divided data, and the payload portion of said second data frame is second half divided data. 2. The wireless transmitter of claim 1, wherein the payload portion of the first data frame and the payload portion of the second data frame are the same data. A confirmation unit for confirming the authentication code included in the acknowledgment,
The wireless transmitter according to any one of claims 1 to 4, wherein said first wireless communication unit, upon receiving said acknowledgment, transmits said second data frame to said wireless receiver. a second management unit that manages a received frame counter;
a second wireless communication unit that receives the first data frame and the second data frame;
a determination unit that determines whether or not the second wireless communication unit has normally received the first data frame based on the magnitude relationship between the transmission frame counter and the reception frame counter included in the first data frame; prepared,
If the determination unit determines that the second wireless communication unit has successfully received the first data frame, the second management unit updates the received frame counter,
the second wireless communication unit, if the determination unit determines that the second wireless communication unit has successfully received the first data frame, transmits an acknowledgment;
The determination unit determines whether the second wireless communication unit normally receives the second data frame based on a magnitude relationship between the updated transmission frame counter and the updated reception frame counter included in the second data frame. determine whether or not
normal reception of the first data frame and the second data frame only when the determination unit determines that the second wireless communication unit has normally received the first data frame and the second data frame; processed as data reception of
The second management unit manages an acknowledgment transmission frame counter,
the acknowledgment includes the acknowledgment transmission frame counter;
The wireless receiver, wherein the second management unit updates the acknowledgment transmission frame counter when the second wireless communication unit transmits an acknowledgment. 7. The wireless receiver of Claim 6 , wherein said acknowledgment includes an authentication code. 8. A radio receiver according to claim 6 or 7 , wherein the authentication code contained in said first data frame is included in the payload portion of said acknowledgment. a radio transmitter according to any one of claims 1 to 5 ;
A radio communication system comprising a radio receiver according to any one of claims 6 to 8 . A smart lock comprising a wireless receiver according to any one of claims 6-8 . An alarm comprising the radio receiver according to any one of claims 6-8 . A smart meter comprising the wireless receiver according to any one of claims 6 to 8 .

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