JP5454489B2 - Wireless communication apparatus and communication system - Google Patents

Description

  The present invention relates to a wireless communication apparatus and a communication system that wirelessly transmit data including a transmission time.

  Conventionally, in order to prevent data transmitted wirelessly from being falsified by a malicious third party, a method of transmitting a transmission data by adding a message authentication code (Message Authentication code) to the transmission data is known (for example, (See Patent Document 1).

JP 2010-258864 A

  By the way, in the technique described in Patent Document 1, when transmission time information indicating a time for transmitting transmission data is added to the transmission data, data transmission is performed according to the following procedure.

  First, when there is a transmission request for transmission data, current time information is acquired. Then, the current time information is added to the transmission data as transmission time information. Hereinafter, the transmission data with the transmission time information added is referred to as transmission time-added transmission data.

  Thereafter, a message authentication code is generated using transmission time-added transmission data as original data, and the generated message authentication code is added to the transmission time-added transmission data, and then wireless transmission is performed.

Therefore, there is a difference corresponding to the time required for generating the message authentication code between the time when the wireless transmission was actually performed and the transmission time indicated by the transmission time information added to the transmission data.
Therefore, when the wireless communication device that has received the transmission data synchronizes its own clock based on the transmission time information included in the data, the time of the clock of the wireless communication device that transmitted the data and the data are received. There is a problem that the above difference occurs between the time of the clock of the wireless communication device and the synchronization accuracy between the transmitting wireless communication device and the receiving wireless communication device cannot be obtained.

  The present invention has been made in view of these problems, and makes it possible to match the time when transmission data is actually transmitted with the transmission time indicated by the transmission time information added to the transmission data. The purpose is to provide technology.

  In the wireless communication apparatus according to claim 1, which is made to achieve the above object, first, the transmission time determination unit determines a data transmission time that is a time for wirelessly transmitting data, and the generation unit determines the data transmission time. A message authentication code or an electronic signature is generated based on transmission time additional data composed of the transmission time information shown and data transmitted at the data transmission time. Then, when the transmission means reaches the data transmission time determined by the transmission time determination means, the transmission means wirelessly transmits data composed of the message authentication code or electronic signature generated by the generation means and transmission time additional data.

  In the wireless communication device configured as described above, a message is determined based on data (transmission time additional data) to which transmission time information is added after the transmission unit determines data transmission time (data transmission time) in advance. An authentication code or electronic signature is generated, and thereafter, when the data transmission time is reached, data composed of the message authentication code or electronic signature and transmission time additional data is wirelessly transmitted. For this reason, the time when the wireless communication apparatus actually wirelessly transmits data can coincide with the data transmission time indicated by the transmission time information included in the transmitted data.

  Therefore, the wireless communication device that has received the data transmitted from the wireless communication device synchronizes the time of its own clock with the data transmission time indicated by the transmission time information in the received data, thereby Synchronization accuracy can be improved.

  Further, in the wireless communication device according to claim 1, as described in claim 2, the generation time calculation means generates the message authentication code or the electronic signature based on the data length of the transmission time additional data. The time required for the generation is calculated, and the transmission time determination means completes the generation of the message authentication code or the electronic signature based on the generation required time calculated by the generation time calculation means. The data transmission time may be determined so as to be after the generation completion time.

  That is, in the wireless communication device according to claim 2, based on the data length of the transmission time additional data, a time at which generation of a message authentication code or an electronic signature is completed (generation completion time) is predicted, and this generation completion time The data transmission time is set later. For this reason, it is difficult to generate a situation where the generation of the message authentication code or the electronic signature is completed after the data transmission time determined by the transmission time determination means. Thereby, after the data transmission time indicated by the transmission time information included in the data to be transmitted, the wireless communication device actually transmits data, and the time when the wireless communication device actually wirelessly transmits, Occurrence of a situation in which the data transmission time indicated by the transmission time information included in the transmitted data does not match can be suppressed.

  Further, in the wireless communication device according to claim 2, the latest data transmission time which is the data transmission time for the latest data transmission in the wireless communication device, and at least one data transmission after the latest data transmission time When the next data transmission time, which is the data transmission time, is preset, the transmission time determination means, as described in claim 3, when the latest data transmission time is before the generation completion time. The next data transmission time after the generation completion time may be set as the data transmission time, and the next next time that is later than the generation completion time and the earliest after the generation completion time as described in claim 4 A time before the data transmission time may be set as the data transmission time.

  Thereby, in the wireless communication device according to claim 3, when the latest data transmission time cannot be determined as the data transmission time, the next data transmission time in which the transmission time is already set can be used. The data transmission time can be easily determined. Further, in the wireless communication device according to claim 4, when the most recent data transmission time cannot be determined as the data transmission time, the wireless communication according to claim 3 is not performed until the next data transmission time is reached. Data can be transmitted earlier than the device.

Moreover, the radio | wireless communications system of Claim 5 is comprised with the radio | wireless communication apparatus of any one of Claims 1-4.
According to the wireless communication system configured as described above, the same effect as that of the wireless communication device according to any one of claims 1 to 4 can be obtained, and synchronization timing of the wireless communication system can be protected. A highly secure wireless communication system can be realized.

1 is an explanatory diagram showing an outline of a configuration and operation of a wireless communication system 1. FIG. It is a functional block diagram which shows the outline | summary of the process which communication apparatus 2A, 2B, 2C, ... performs. It is a flowchart which shows a frame transmission process. It is a flowchart which shows a frame verification process. It is a timing chart for demonstrating the setting method of estimated transmission time ts. It is a timing chart for demonstrating the setting method of the estimated transmission time ts in another embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram showing an outline of the configuration and operation of the wireless communication system 1.
As shown in FIG. 1 (a), the wireless communication system 1 of the present embodiment includes a plurality of communication devices 2A installed as road devices in the vicinity of a vehicle's traveling path, and mounted on the vehicle. It comprises communication devices 2B, 2C,... That perform wireless communication with other vehicles.

  The communication device 2A has a periodic transmission function for periodically transmitting various information such as traffic information to surrounding vehicles. The communication devices 2B, 2C,... Receive a transmission request from a control device mounted on the vehicle. Thus, it has a random transmission function for transmitting the state of the host vehicle or the like to a road machine or another vehicle.

  For communication between the communication devices 2A, 2B, 2C,..., A common communication channel is used. When the communication devices 2B, 2C,. It is determined whether or not the channel is free, and data transmission is started when the communication channel is free.

  The communication device 2A performs regular transmission. The period of this periodic transmission is determined in advance, and the communication device 2A is assigned which period within one periodic transmission cycle is used for regular transmission. Yes.

  The communication device 2A notifies the assigned regular transmission period to the other communication devices 2B, 2C,... By regular transmission, and the other communication devices 2B, 2C,. Prohibits random transmission.

  That is, in the present embodiment, the communication device 2A having a periodic transmission function, as shown in FIG. 1B, transmits a frame composed of transmission time data, periodic transmission data, and a MAC (Message Authentication code) or an electronic signature. , Send regularly to the surroundings. The transmission time data is information indicating the time at which the communication device 2A transmits a frame. The regular transmission data includes various information such as traffic information, and regular transmission period information indicating the start timing of the regular transmission period and the length (period length) of the regular transmission period. The MAC or electronic signature is generated using a transmission message composed of transmission time data and regular transmission data as original data.

  Then, when the other communication devices 2B, 2C,... Having the random transmission function receive the frame transmitted by the communication device 2A, they are shown in FIG. 1 (c) based on the periodic transmission period information included in the frame. As described above, the random transmission prohibition period is set so that the random transmission is not started within the regular transmission period of the communication device 2A, and the random transmission period is set within the period other than the random transmission prohibition period (random transmission period). Send.

FIG. 2A is a functional block diagram illustrating an outline of processing executed by the communication device 2A.
As illustrated in FIG. 2A, the communication device 2 </ b> A includes a data input unit 11, a data processing unit 12, a MAC / electronic signature processing unit 13, and a transmission unit 14.

  Among these, the data input unit 11 is configured to be able to input data by wire or wirelessly with an information station installed outside the communication device 2A. From this information station, data indicating various information such as traffic information is input. Then, the data is transmitted to the data processing unit 12.

  The data processing unit 12 generates a transmission message by adding transmission time data to the data received from the data input unit 11, transmits the generated transmission message to the MAC / electronic signature processing unit 13, and transmits the MAC / electronic signature. The MAC or electronic signature received from the processing unit 13 is added to the transmission message to generate a frame, and the generated frame is transmitted to the transmission unit 14. The data processing unit 12 includes a clock (not shown) that counts time by counting the internal clock, and uses this clock to determine the transmission time indicated by the transmission time data.

  The MAC / electronic signature processing unit 13 generates a MAC or electronic signature using the transmission message received from the data processing unit 12 as original data, and transmits the generated MAC or electronic signature to the data processing unit 12.

The transmission unit 14 receives a frame from the data processing unit 12 and transmits the frame wirelessly.
Note that the communication device 2A is configured around a well-known microcomputer including a CPU, ROM, RAM, I / O, and a bus line that connects these components. Based on a program stored in the ROM, the communication device 2A The data input unit 11, the data processing unit 12, the MAC / digital signature processing unit 13, and the transmission unit 14 are executed.

FIG. 2B is a functional block diagram illustrating an outline of processing executed by the communication devices 2B, 2C,.
As shown in FIG. 2B, the communication devices 2B, 2C,... Have a data input / output unit 21, a data processing unit 22, a MAC / electronic signature processing unit 23, a transmission / reception unit 24, a synchronization processing unit 25, and a data storage. Part 26 is provided.

  Among these, the data input / output unit 21 inputs transmission data from the control device mounted on the automobile, transmits the data to the data processing unit 22, and transmits transmission data (control data) from the data processing unit 22 to the control device. When received, control data is transmitted to the control device.

  Further, when receiving data from the data input / output unit 21, the data processing unit 22 generates a transmission message by adding additional information such as a header to the received data, and the generated transmission message is subjected to MAC / electronic signature processing. The frame is generated by adding the MAC or electronic signature received from the MAC / electronic signature processing unit 23 to the transmission message, and the generated frame is transmitted to the transmission / reception unit 24.

  Further, when receiving a frame from the transmission / reception unit 24, the data processing unit 22 transmits a verification request message including the received frame and a verification command to the MAC / electronic signature processing unit 23, and receives a verification result (acceptance or rejection). At the same time, when the data processing unit 22 receives the acceptance as the verification result from the MAC / electronic signature processing unit, the message included in the received frame is stored in the data storage unit 26.

  Further, when it is necessary to transmit control data to the control device, the data processing unit 22 receives a message from the data storage unit 26, generates control data from the received message, and transmits the generated control data to the data input / output unit. To 21.

  The MAC / electronic signature processing unit 23 verifies the MAC or electronic signature of the received frame of the verification request message received from the data processing unit 22, and transmits a verification result (acceptance or rejection) to the data processing unit 22.

  In addition, when the frame is received from the data processing unit 22, the transmission / reception unit 24 wirelessly transmits the frame, and when the frame is wirelessly received, the transmission / reception unit 24 transmits the frame to the data processing unit 22.

  The synchronization processing unit 25 includes a clock (not shown) that counts the time by counting the internal clock. Then, when the data processing unit 22 receives the acceptance as the verification result from the MAC / electronic signature processing unit, the synchronization processing unit 25 synchronizes the clock with the time indicated by the transmission time data added to the received frame.

  In addition, when the data processing unit 22 receives acceptance as a verification result from the MAC / electronic signature processing unit, the data storage unit 26 stores a message included in the received frame, and stores the stored message as a data processing unit. 22 to send.

  The communication devices 2B, 2C,... Are mainly composed of a well-known microcomputer comprising a CPU, ROM, RAM, I / O and a bus line connecting these components. Based on the data input / output unit 21, the data processing unit 22, the MAC / digital signature processing unit 23, the transmission / reception unit 24, the synchronization processing unit 25, and the data storage unit 26.

  In the wireless communication system 1 configured as described above, the communication device 2A executes a frame transmission process for generating and transmitting a frame, and the communication devices 2B, 2C,... Perform a frame verification process for verifying the received frame. Run.

  FIG. 3 is a flowchart showing the frame transmission process, and FIG. 4 is a flowchart showing the frame verification process. FIG. 5 is a timing chart for explaining a method of setting the predicted transmission time ts.

  Next, the procedure of frame transmission processing executed by the communication device 2A will be described with reference to FIG. This frame transmission process is a process repeatedly executed while the CPU of the communication device 2A is activated.

  When this frame transmission process is executed, the communication device 2A first determines in S10 whether or not data is input from the outside of the communication device 2A. If no data is input (S10: NO), the frame transmission process is temporarily terminated.

  On the other hand, when data is input (S10: YES), the transmission order instruction value i is set to 1 in S20, and the current time t0 is acquired from the clock included in the data processing unit 12 in S30. . Thereafter, in S40, the future transmission time ti is acquired. The future transmission time ti indicates the i-th frame transmission time based on the current time t0. In the present embodiment, the communication device 2A has a single periodic transmission period so that the frame is transmitted only once after a preset fixed time tf (see FIG. 5) has elapsed since the start of the periodic transmission period. The transmission time at is set. That is, the time at which the communication device 2A transmits a frame has already been determined. When the periodic transmission cycle is Tp, the future transmission time ti is expressed by the following equation (1). Note that i is an integer of 1 or more.

ti = t1 + Tp × (i−1) (1)
In S50, the difference between the future transmission time ti and the current time t0 is calculated as a transmission delay time Δt, and in S60, the data determined to be input in the process of S10 and the information indicating the future transmission time ti. And the time required to generate a MAC or electronic signature using a transmission message composed of periodic transmission period information as original data (hereinafter referred to as MAC / electronic signature generation processing time tm) as the data length of the original data Calculate based on

  Thereafter, in S70, it is determined whether or not the transmission delay time Δt is longer than the MAC / electronic signature generation processing time tm. If the transmission delay time Δt is not longer than the MAC / electronic signature generation processing time tm (S70: NO), the transmission order instruction value i is incremented (added by 1) in S80, and the process proceeds to S30. The above process is repeated.

  On the other hand, when the transmission grace time Δt is longer than the MAC / electronic signature generation processing time tm (S70: YES), the predicted transmission time ts is set to the future transmission time ti in S90. After that, in S100, a MAC or electronic signature is obtained with the transmission message composed of the data determined to be input in the process of S10, the predicted transmission time information indicating the predicted transmission time ts, and the periodic transmission period information as original data. Generate. In S110, a frame composed of the predicted transmission time information, the data determined to be input in the process of S10, the periodic transmission period information, and the MAC or electronic signature generated in the process of S100 is generated. .

  Thereafter, in S120, it is determined whether or not the current time is the predicted transmission time ts. If the current time is not the predicted transmission time ts (S120: NO), the process of S120 is repeated, and the process waits until the current time becomes the predicted transmission time ts. On the other hand, when the current time is the predicted transmission time ts (S120: YES), in S130, the frame generated in the process of S110 is wirelessly transmitted, and the frame transmission process is temporarily ended.

  Next, the procedure of frame verification processing executed by the communication devices 2B, 2C,... Will be described with reference to FIG. This frame verification process is a process repeatedly executed while the CPUs of the communication devices 2B, 2C,.

  When this frame verification process is executed, the communication devices 2B, 2C,... First determine in S210 whether or not a frame has been received from the communication device 2A. Here, when the frame is not received (S210: NO), the frame verification process is temporarily ended.

  On the other hand, when a frame is received (S210: YES), a transmission message (that is, transmission time data and periodic transmission shown in FIG. 1B) is transmitted from the frame determined to be received in S210 in S220. Data) and MAC or electronic signature. In step S230, the MAC or electronic signature of the received message is verified.

  In S240, the process is divided depending on whether or not the verification in S230 is accepted. When the verification in S230 is rejected (S240: NO), the frame determined to have been received in the process of S210 is discarded in S250, and the frame verification process is temporarily ended.

  On the other hand, if the verification in S230 is accepted (S240: YES), the message included in the received frame is stored in S260, and the time indicated by the transmission time data extracted in S220 is further stored in S270. In addition, the clock included in the synchronization processing unit 25 is synchronized, and the frame verification process is temporarily ended.

  In the communication device 2A of the wireless communication system 1 configured as described above, first, the predicted transmission time ts for wirelessly transmitting the frame is determined (S30 to S90), and the input data, the predicted transmission time information, and the periodic transmission period information are used. A message authentication code (MAC) or electronic signature is generated based on the configured transmission message (S100). When the predicted transmission time ts is reached (S120: YES), a frame composed of a transmission message and a message authentication code (MAC) or an electronic signature is wirelessly transmitted (S130).

  In the communication apparatus 2A configured as described above, a time for transmitting a frame is determined in advance, and then a message authentication code (MAC) or an electronic signature is obtained based on data (transmission message) to which predicted transmission time information is added. After that, when a predicted transmission time ts is reached, a frame composed of a message authentication code (MAC) or electronic signature and a transmission message is wirelessly transmitted. For this reason, the time when the communication device 2A actually wirelessly transmits the frame can be matched with the predicted transmission time ts indicated by the predicted transmission time information included in the transmitted frame.

  Therefore, the communication devices 2B, 2C,... That have received the data transmitted from the communication device 2A synchronize their clock time with the time indicated by the predicted transmission time information in the received data, thereby enabling the communication device 2A. Synchronization accuracy can be improved.

  Further, based on the data length of the transmission message, a time required to generate the message authentication code (MAC) or the electronic signature (MAC / electronic signature generation processing time tm) is calculated (S60), and the message authentication code (MAC) Alternatively, the predicted transmission time ts is determined so as to be later than the time when the generation of the electronic signature is completed (hereinafter also referred to as the authentication code / electronic signature generation completion time) (S30 to S90).

  For this reason, it is difficult to generate a situation in which the generation of the message authentication code (MAC) or the electronic signature is completed after the determined predicted transmission time ts. As a result, the communication device 2A transmits the actual frame after the predicted transmission time ts indicated by the predicted transmission time information included in the frame to be transmitted, the time when the communication device 2A actually wirelessly transmits, and the transmission The occurrence of a situation in which the predicted transmission time ts indicated by the predicted transmission time information included in the received frame does not match can be suppressed.

  The time at which the communication device 2A transmits a frame has already been determined. If the most recent data transmission time at the communication device 2A is t1 (see FIG. 5), the subsequent data transmission time is expressed by the above equation (1). It is set in advance. Then, the earliest data transmission time after the authentication code / electronic signature generation completion time tc (see FIG. 5) is set as the predicted transmission time ts (S30 to S90). For example, as shown in FIG. 5, when the latest data transmission time t1 is before the authentication code / electronic signature generation completion time tc, the time t2 (= t1 + Tp) set as the next data transmission time is used. The predicted transmission time is ts.

  As a result, when the most recent data transmission time in the communication device 2A cannot be determined as the predicted transmission time ts, the data transmission time for which the time has already been set can be used, so the predicted transmission time ts can be easily set. Can be determined.

The wireless communication system 1 can realize a highly secure wireless communication system that can protect the synchronization timing of the wireless communication system.
In the embodiment described above, the communication device 2A is the wireless communication device according to the present invention, the processes at S30 to S90 are the transmission time determining means according to the present invention, the processing at S100 is the generating means according to the present invention, and the processes at S120 and S130 are the present invention. The transmission means and the transmission message are transmission time additional data in the present invention.

  Further, the processing of S60 is the generation time calculation means in the present invention, the MAC / electronic signature generation processing time tm is the required generation time in the present invention, the data transmission time t1 is the latest data transmission time in the present invention, and the data transmission time t2 is in the present invention. Is the next data transmission time.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.
For example, in the embodiment described above, the present invention is applied to a device that wirelessly transmits data within a periodic transmission period that is repeated at regular intervals. However, the present invention is not limited to this, and data including a transmission time is included. Any wireless communication device that performs wireless transmission may be used.

  In the above embodiment, the wireless transmission of data only once within the periodic transmission period is shown. However, the present invention can be applied even to an apparatus that wirelessly transmits data multiple times within the periodic transmission period. it can. For example, as shown in FIG. 6A, in the case where data is preset to be transmitted at times t1, t2, and t3 within a regular transmission period, the latest data transmission time t1 is an authentication code / electronic signature. When the time is before the generation completion time tc, the time t2 set as the next data transmission time may be set as the predicted transmission time ts.

  Alternatively, as shown in FIG. 6B, for example, the data transmission time is set in advance so that data is transmitted at times t1 and t2 within a regular transmission period, and the interval between time t1 and time t2 is the data transmission time. In the longer case, when the latest data transmission time t1 is before the authentication code / electronic signature generation completion time tc, it is after the authentication code / electronic signature generation completion time tc and before the data transmission time t2. This time t1 ′ may be the predicted transmission time ts. Thus, data can be transmitted at a time earlier than the data transmission time t2 without waiting until the data transmission time t2.

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 2A, 2B, 2C ... Communication apparatus, 11 ... Data input part, 12 ... Data processing part, 13 ... MAC and electronic signature processing part, 14 ... Transmission part, 21 ... Data input / output part, 22 ... Data processing unit, 23... MAC / electronic signature processing unit, 24... Transmission / reception unit, 25.

Claims (5)

Transmission time determining means for determining a data transmission time which is a time for wirelessly transmitting data;
Generating means for generating a message authentication code or an electronic signature based on transmission time additional data composed of transmission time information indicating the data transmission time and data transmitted at the data transmission time;
When the data transmission time determined by the transmission time determination means is reached, a transmission means for wirelessly transmitting data composed of the message authentication code or electronic signature generated by the generation means and the transmission time additional data. A wireless communication device comprising: Based on the data length of the transmission time additional data, the generation unit includes a generation time calculation unit that calculates a generation required time that is a time required for the generation unit to generate the message authentication code or the electronic signature,
The transmission time determining means includes
Based on the generation required time calculated by the generation time calculation means, the data transmission time is set to be after a generation completion time that is a time at which the generation means completes generation of the message authentication code or electronic signature. The wireless communication device according to claim 1, wherein the wireless communication device is determined. The latest data transmission time that is the data transmission time for the latest data transmission in the wireless communication device, and the next data transmission time that is the data transmission time for at least one or more data transmissions after the most recent data transmission time; Is preset,
The transmission time determining means includes
The wireless communication according to claim 2, wherein when the latest data transmission time is before the generation completion time, the next data transmission time after the generation completion time is set as the data transmission time. apparatus. The latest data transmission time that is the data transmission time for the latest data transmission in the wireless communication device, and the next data transmission time that is the data transmission time for at least one or more data transmissions after the most recent data transmission time; Is preset,
The transmission time determining means includes
When the latest data transmission time is before the generation completion time, the time that is after the generation completion time and before the next data transmission time earliest after the generation completion time is The wireless communication apparatus according to claim 2, wherein a data transmission time is set.   A wireless communication system comprising the wireless communication device according to any one of claims 1 to 4.

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