JP6992309B2 - Transmitter, receiver, and communication method - Google Patents

Description

The present invention relates to a transmitting device, a receiving device, and a communication method.

The communication system mounted on the vehicle may comply with, for example, the E2E (End to End) protocol described in the specifications of AUTOSAR (Automotive Open System Architecture). In the E2E protocol, the transmission device includes the error detection code such as a CRC (Cyclic Redundancy Check) code and the counter value in the data frame and transmits the data together with the data to be transmitted. On the other hand, the receiving device confirms the correctness (consistency) and the receiving order of the received data based on the error detection code and the counter value included in the data frame.

Further, in the communication system described in Patent Document 1, the first communication node uses the counter value as a seed based on the data transmitted to the second communication node and the counter value indicating the transmission order of the data. , The first error detection code is calculated. Then, the first communication node transmits a data frame including the first error detection code and data to the second communication node. On the other hand, the second communication node receives the data frame from the first communication node, and the counter value is based on the data included in the received data frame and the counter value indicating the reception order of the data. Is used as a seed to calculate the second error detection code. Then, the second communication node determines whether the second error detection code and the first error detection code included in the data frame match, and based on the determination result, the data included in the data frame is used. Perform the corresponding processing.

In addition to the above-mentioned Patent Document 1, the techniques described in Patent Documents 2 to 5 are known as related techniques.

Japanese Unexamined Patent Publication No. 2013-207600 Japanese Unexamined Patent Publication No. 2013-219710 Japanese Unexamined Patent Publication No. 2014-056381 Japanese Unexamined Patent Publication No. 2016-021623 Japanese Patent Publication No. 2015-511905

However, in the above-mentioned communication system using the counter value, the counter value increases or decreases by a predetermined number (for example, 1) from the initial value (for example, 1) each time a data frame is transmitted. Therefore, for example, when the initial data frame is transmitted or when the initial value of the counter value is used due to an abnormality in which the counter value cannot be acquired, it is easy to specify the counter value which is the seed. As a result, in the above-mentioned communication system using the counter value, for example, it becomes easy to intercept the data frame, analyze the data frame, identify the counter value as the seed, tamper with the data, and hijack the communication. .. In addition, for example, in the communication system described in Patent Document 1, since the communication node is provided with a physical counter for generating a counter value, the size of the communication node becomes large, and the communication node is placed in a predetermined space of the vehicle. It may not be possible to store it.

An object according to one aspect of the present invention is to provide a communication device in which communication security is ensured.

The transmission device according to the present invention includes a hash value processing unit, a data frame generation unit, and a communication module. The hash value processing unit calculates the hash value for the transmission target data this time by using the transmission target data, the encryption key, and the hash function. The data frame generation unit generates a data frame including the transmission target data, the current hash value, and the previous hash value calculated for the previously transmitted data prior to the transmission target data. The communication module sends a data frame.

According to the transmission device according to one embodiment, it is possible to provide a communication device in which the security of communication is ensured.

It is a figure which shows the structural example of the communication system which includes the communication apparatus according to 1st Embodiment. It is a figure which shows the exemplary flow of the transmission processing performed by the communication apparatus according to 1st Embodiment. It is a figure which shows the structural example of the data frame generated by the communication apparatus according to 1st Embodiment. It is a figure which shows the exemplary flow of the reception processing performed by the communication apparatus according to 1st Embodiment. It is a figure which shows the exemplary flow of the reception processing performed by the communication apparatus according to 1st Embodiment. It is a figure which shows an example of the hash value preservation list according to 1st Embodiment. It is a figure which shows the exemplary flow of the reception processing performed by the communication apparatus according to 2nd Embodiment. It is a figure which shows the exemplary flow of the reception processing performed by the communication apparatus according to 2nd Embodiment. It is a figure which shows the structural example of the data frame generated by the communication apparatus according to 3rd Embodiment. It is a figure which shows the structural example of the data frame generated by the communication apparatus according to 4th Embodiment. It is a figure which shows the exemplary flow of the transmission processing performed by the communication apparatus according to 4th Embodiment. It is a figure which shows the exemplary flow of the reception processing performed by the communication apparatus according to 4th Embodiment. It is a figure which shows the exemplary flow of the reception processing performed by the communication apparatus according to 4th Embodiment. It is a figure which shows the structural example of the data frame generated by the communication apparatus according to 5th Embodiment. It is a figure which shows the structural example of the data frame generated by the communication apparatus according to 6th Embodiment.

Hereinafter, embodiments will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 is a diagram showing a configuration example of a communication system including a communication device according to the first embodiment. In the configuration example shown in FIG. 1, the communication system 1 includes a plurality of communication devices 2-1 to 2-N (N is an integer of 2 or more), and the plurality of communication devices 2-1 to 2-N are communication lines. Connect to each other via 3. In the following description, when a plurality of communication devices 2-1 to 2-N are not particularly distinguished, they may be referred to as communication device 2. The communication system 1 may be a communication system conforming to the specifications of CAN (Controller Area Network).

The communication device 2 is a communication node of the communication system 1. The communication device 2 is, for example, an electronic control unit (ECU) mounted on a predetermined position of a vehicle. Hereinafter, the communication device 2 will be described as a device having a transmission function of generating and transmitting a data frame including transmission target data and a reception function of receiving and processing a data frame including reception target data. However, one or more communication devices 2 among the plurality of communication devices 2 constituting the communication system 1 may be a transmission device having no receiving function or a receiving device having no transmitting function. good. Therefore, the communication device 2 is an example of a transmission device and a reception device according to the embodiment.

The communication device 2 includes a control unit 21, a storage unit 22, and a communication module 23. The control unit 21, the storage unit 22, and the communication module 23 are connected to each other via the bus 24. Note that FIG. 1 shows the components for convenience only for the communication device 2-1. However, the other communication device 2 may include the same components as the communication device 2-1. Further, the other communication device 2 may include only the component having a transmission function as the transmission device, or may include only the component having the reception function as the reception device among the components of the communication device 2-1. ..

The control unit 21 is composed of, for example, a CPU (Central Processing Unit), a multi-core CPU, or a programmable device (FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), or the like). The control unit 21 controls the operation of the entire communication device 2. For example, the control unit 21 generates a data frame including transmission target data to be transmitted to another communication device 2. Further, for example, the control unit 21 executes a predetermined process on the data frame received from the other communication device 2. The control unit 21 includes a hash value processing unit 211, an error detection code calculation unit 212, a data frame generation unit 213, an error detection unit 214, and a data frame processing unit 215. These components 211 to 215 cooperate with each other to execute a desired process. The specific operation of each component included in the control unit 21 will be described later.

The storage unit 22 is composed of, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage unit 22 stores a program that defines the processing operation of the control unit 21, a public key and a hash function specified in advance by the communication device 2, and data processed by the control unit 21. The public key may be a CAN Identifier Base ID or a CAN Identifier extension ID indicating a data frame transmitted by the communication device 2. Further, the public key may be an arbitrary numerical value that can be received by the receiving device as the data of the data frame transmitted by the communication device 2.

The communication module 23 is composed of, for example, a modulator, a demodulator, or the like. For example, the communication module 23 modulates the data frame generated by the control unit 21 according to a predetermined communication method, and transmits the data frame to the communication device 2 which is the destination of the data frame. Further, for example, the communication module 23 demodulates a data frame received from another communication device 2 according to a predetermined communication method, and outputs the data frame to the control unit 21.

An exemplary flow of transmission processing and reception processing executed by the communication device 2 will be described below.
<< Transmission processing >>
FIG. 2 is a diagram showing an exemplary flow of transmission processing executed by the communication device according to the first embodiment. The communication device 2 may execute a series of transmission processes as shown in FIG. 2 each time transmission target data is generated.

When the transmission target data to be transmitted to the other communication device 2 is generated in the control unit 21 in step S101, the hash value processing unit 211 executes the process of step S102. In step S102, the hash value processing unit 211 calculates the current hash value for the transmission target data using the transmission target data, the encryption key, and the hash function. This time, the hash value refers to the data included in the data frame, that is, the hash value calculated for the transmission target data (or reception target data). The encryption key is a key used to encrypt the hash value.

In step S103, the hash value processing unit 211 determines whether or not the current hash value calculated in step S102 matches the previous hash value. The previous hash value refers to a hash value calculated by the hash value processing unit 211 for the data previously transmitted prior to the transmission target data (or reception target data). The hash value for the previously transmitted data is calculated as the hash value this time by the hash value processing unit 211 in step S102 during a series of transmission processes for the data. Then, the hash value processing unit 211 stores the current hash value for the previously transmitted data as the previous hash value for the data to be transmitted next time after the data in the storage unit 22.

When it is determined that the hash value matches the previous hash value this time (“YES” in step S103), the transmission target data and the data previously transmitted prior to the target data are the same, so the transmission target data is re-assigned. No need to send. Therefore, in step S104, the hash value processing unit 211 discards the transmission target data, and the series of transmission processing for the transmission target data ends.

On the other hand, when it is determined that the hash value does not match the previous hash value (“NO” in step S103), the series of transmission processes proceeds to step S105. In step S105, the error detection code calculation unit 212 calculates the error detection code based on the transmission target data, the current hash value, and the previous hash value. In step S106, the data frame generation unit 213 generates a data frame including the transmission target data, the error detection code, the current hash value, and the previous hash value.

FIG. 3 is a diagram showing a configuration example of a data frame generated by a communication device according to the first embodiment. Note that FIG. 3 shows the data fields in the standard format of the data frame defined by CAN, but the data frames are not shown such as SOF (Start Of Frame) and ID (Identifier). Other fields may also be included. In the configuration example shown in FIG. 3, one byte is assigned to each of the error detection code, the current hash value, and the previous hash value in the 8-byte data field. Further, as shown by the fields described as "data 1" to "data 5" in FIG. 3, 5 bytes are assigned to the data (transmission target data or reception target data) whose minimum data unit is 1 byte. ing.

In the example shown in FIG. 3, the previous hash value included in the data frame transmitted by the communication device 2 two times before is the hash value A, and the hash value this time is the hash value B. The previous hash value included in the data frame transmitted last time by the communication device 2 is the hash value B, and the hash value this time is the hash value C. The previous hash value included in the data frame transmitted by the communication device 2 this time is the hash value C, and the hash value this time is the hash value D. As described above, the current hash value of the previous data frame is the previous hash value of the previous data frame, and the current hash value of the previous data frame is the previous hash value of the current data frame. Therefore, the communication device 2 (for example, the receiving device) on the receiving side refers to the current hash value and the previous hash value of the received plurality of data frames, respectively, so that the data included in the plurality of data frames (reception target data) can be obtained. ) Can be specified.

In step S107, the communication module 23 transmits the data frame generated by the data frame generation unit 213 to another communication device 2 which is the destination of the data frame.
In this way, the communication device 2 calculates the hash value for the transmission target data this time by using the transmission target data, the encryption key, and the hash function. Then, the communication device 2 generates and transmits a data frame including the transmission target data, the current hash value, and the previous hash value calculated for the previously transmitted data prior to the transmission target data. Therefore, the communication device 2 on the receiving side compares the previous hash value in the received data frame with the current hash value in the data frame processed prior to the data frame to change the processing order of the data to be received. You can check it. Further, the communication device 2 on the receiving side can confirm the correctness of the data to be received by verifying the hash value this time in the data frame.

Therefore, according to the communication device according to the embodiment, it is possible to ensure the safety of communication at a high ASIL (Automotive Safety Integrity Level) without using the counter value or increasing the number of data of the error detection code. Further, according to the communication device according to the embodiment, the size of the communication node does not increase due to the provision of the physical counter in the communication device.
<< Reception processing >>
4 (A) and 4 (B) are diagrams showing an exemplary flow of reception processing executed by the communication device according to the first embodiment. The communication device 2 may execute a series of reception processes as shown in FIGS. 4A and 4B each time a new data frame is received.

In step S201, the communication module 23 receives the data frame transmitted by the other communication device 2. In step S202, the error detection unit 214 extracts an error detection code from the received data frame. Further, in step S203, the error detection code calculation unit 212 calculates the error detection code based on the reception target data included in the received data frame, the current hash value, and the previous hash value.

In step S204, the error detection unit 214 determines whether or not the error detection code extracted from the received data frame and the error detection code calculated by the error detection code calculation unit 212 match.

When it is determined that the error detection code extracted from the received data frame and the error detection code calculated by the error detection code calculation unit 212 do not match (“NO” in step S204), the data to be received, the hash value this time, and the hash value. At least one of the previous hash values is incorrect. Therefore, in step S205, the data frame processing unit 215 discards the received data frame. Then, the data frame processing unit 215 returns the series of reception processing to step S201 in order to receive the data frame without error. The data frame generation unit 213 may generate an error frame indicating that the received data frame has an error. Then, the communication module 23 may transmit an error frame to the communication device 2 that has transmitted the received data frame.

On the other hand, when it is determined that the error detection code extracted from the received data frame and the error detection code calculated by the error detection code calculation unit 212 match (“YES” in step S204), the error detection unit 214 uses step S206. Proceed to the process of. In step S206, the error detection unit 214 determines whether or not there is a data frame waiting to be processed. The processing-waiting data frame is a data frame other than the data frame received in step S201, and refers to a data frame in which a series of reception processing as shown in FIGS. 4A and 4B has not been completed.

When it is determined that there is no data frame waiting to be processed (“NO” in step S206), in step S207, the error detection unit 214 extracts the hash value from the received data frame this time. Then, in step S208, the error detection unit 214 stores the extracted hash value this time in the hash value storage list in the storage unit 22. The hash value storage list is a list in which hash values are stored this time, including data frames for which a series of reception processes have not been completed.

On the other hand, when it is determined that there is a data frame waiting to be processed (“YES” in step S206), in step S209, the error detection unit 214 extracts the previous hash value and the current hash value from the received data frame. Then, in step S210, the error detection unit 214 compares the extracted previous hash value with the current hash value already stored in the hash value storage list. By such comparison, the error detection unit 214 sorts the received data frame and the data frame waiting to be processed in the order of transmission of the data frame. Further, in step S211 the error detection unit 214 saves the current hash value of the sorted data frame in the hash value storage list.

For example, if the extracted previous hash value is the hash value C, the extracted current hash value is the hash value D, and the current hash values already stored in the hash value storage list are the hash value B and the hash value C. Suppose. Under this assumption, the same current hash value as the extracted previous hash value C exists in the hash value storage list. Therefore, the received data frame and the data frame waiting to be processed are sorted in the order of the hash value B, the hash value C, and the hash value D this time. Further, the hash value B, the hash value C, and the hash value D are stored in the hash value storage list in the sort order of the data frame.

In step S212, the error detection unit 214 determines whether or not the current hash value included in the last processed data frame and the previous hash value included in the first data frame sorted in the transmission order of the data frames match. judge. The last processed data frame refers to a data frame in which a series of reception processes as shown in FIGS. 4 (A) and 4 (B) is finally completed. For example, when there is no data frame waiting to be processed, the error detection unit 214 determines whether or not the current hash value included in the last processed data and the previous hash value included in the data frame received in step S201 match. judge.

When it is determined that the current hash value included in the last processed data frame and the previous hash value included in the first data frame do not match (“NO” in step S212), the received target data included in the first data frame is selected. There is data that will be processed first. That is, there is data that should have been transmitted (or should be received first) before the reception target data included in the first data frame. Therefore, the error detection unit 214 returns the series of reception processing to step S201 in order to receive the data frame including the data scheduled to be processed first.

On the other hand, when it is determined that the current hash value included in the last processed data frame and the previous hash value included in the first data frame match (“YES” in step S212), the hash value processing unit 211 performs step S213. Proceed to the process of. In step S213, the hash value processing unit 211 calculates the hash value 1 (first hash value) using the hash function and the reception target data included in the first data frame. For example, when there is no data frame waiting to be processed, the hash value processing unit 211 calculates the hash value 1 by using the hash function and the reception target data included in the data frame received in step S201. Further, in step S213, the hash value processing unit 211 calculates the hash value 2 (second hash value) using the public key, the hash function, and the current hash value included in the first data frame. For example, when there is no data frame waiting to be processed, the hash value processing unit 211 calculates the hash value 2 using the public key, the hash function, and the current hash value included in the data frame received in step S201.

In step S214, the error detection unit 214 determines whether or not the hash value 1 calculated by the hash value processing unit 211 and the hash value 2 match. For example, when there is a data frame waiting to be processed, in step S214, the error detection unit 214 includes the hash value 1 calculated by the hash value processing unit 211, the public key, the hash function, and the current hash including the first data frame. It is determined whether or not the hash value 2 calculated by using the value and the hash value 2 match. Further, for example, when the processing waiting data frame does not exist, the error detection unit 214 determines whether or not the hash value 1 calculated by the hash value processing unit 211 and the hash value 2 match.

When it is determined that the hash value 1 calculated by the hash value processing unit 211 and the hash value 2 do not match (“NO” in step S214), there is an error in the reception target data included in the first data frame. Therefore, in step S215, the error detection unit 214 deletes the hash value corresponding to the first data frame from the hash value storage list this time. Further, the data frame processing unit 215 discards the first data frame. Then, the data frame processing unit 215 returns the series of reception processing to step S201 in order to receive the data frame without error. The data frame generation unit 213 may generate an error frame indicating that there was an error in the first data frame. Then, the communication module 23 may transmit an error frame to the communication device 2 that has transmitted the first data frame.

On the other hand, when it is determined that the hash value 1 calculated by the hash value processing unit 211 and the hash value 2 match (“YES” in step S214), the error detection unit 214 proceeds to the process of step S216. In step S216, the error detection unit 214 deletes the current hash value preceding the previous hash value in the first data frame from the hash value storage list. FIG. 5 is a diagram showing an example of a hash value storage list according to the first embodiment. For example, when the process of step S216 is executed for the current data frame shown in FIG. 3, as shown in FIG. 5, the current hash value B preceding the previous hash value C in the current data frame is hashed. Removed from the value storage list. When the processing after step S212 is executed for the current data frame, a series of reception processing for the previous data frame and the previous data frame is completed. Therefore, since it is not necessary to confirm the transmission order of the data frames prior to the current data frame, the current hash value B preceding the previous hash value C in the current data frame is deleted from the hash value storage list.

In step S217, the data frame processing unit 215 executes processing based on the reception target data included in the first data frame.
In this way, the communication device 2 confirms the processing order of the data to be received by comparing the previous hash value in the received data frame with the current hash value in the data frame processed prior to the data frame. .. Further, the communication device 2 confirms the correctness of the reception target data by verifying the hash value this time in the received data frame. Therefore, according to the communication device according to the embodiment, it is possible to ensure the safety of communication with high ASIL without using the counter value or increasing the number of data of the error detection code. Further, according to the communication device according to the embodiment, the size of the communication node does not increase due to the provision of the physical counter in the communication device.

The present invention is not limited to the above embodiments, and various improvements and changes can be made without departing from the gist of the present invention. For example, the above-mentioned first embodiment may be improved or modified as in the second to sixth embodiments shown below. Further, two or more embodiments among the first to sixth embodiments may be combined.
<Second embodiment>
Of the communication devices 2 constituting the communication system 1, at least one communication device 2 may be a communication history recording device that records the communication history of data frames transmitted / received between the other communication devices 2. In this case, the communication device 2 for transmitting the data frame may transmit the data frame to the communication history recording device in addition to the communication device 2 on the receiving side, which is the original destination of the data frame. Further, the communication history recording device may perform a series of reception processes as shown in FIGS. 6 (A) and 6 (B). 6 (A) and 6 (B) are diagrams showing an exemplary flow of reception processing executed by the communication device according to the second embodiment.

As can be understood from the comparison between FIGS. 4A and 4B and FIGS. 6A and 6B, the communication device 2 which is a communication history recording device has a hash value processing unit 211. When it is determined that the calculated hash value 1 and the hash value 2 match (“YES” in step S214), the processes of step S216 and step S217 are not executed. That is, the communication device 2 which is a communication history recording device does not delete the current hash value saved in step S208 or step S211 from the hash value storage list in order to verify the communication history between the other communication devices 2 at a later date. Further, since the communication device 2 which is a communication history recording device is not the communication device 2 on the receiving side which is the original destination of the received data frame, the processing based on the reception target data included in the received data frame is not performed. Instead, as shown in FIGS. 6 (A) and 6 (B), the communication device 2 which is a communication history recording device receives new data frames transmitted / received between the other communication devices 2 in order to receive new data frames. The series of reception processing is returned to step S201.

In this way, if the communication system 1 is provided with the communication device 2 for recording the communication history between the other communication devices 2, the communication history between the other communication devices 2 can be recorded, for example, at the time of diagnosing a vehicle failure. Can be verified.
<Third embodiment>
As shown in FIG. 7, the transmission target data (or reception target data) of the data frame may include time data indicating the current time. FIG. 7 is a diagram showing a configuration example of a data frame generated by a communication device according to a third embodiment.

As can be understood from the comparison between FIGS. 3 and 7, the data frame generated by the communication device 2 according to the third embodiment is a time indicating the current time in the “first data” field or the like. Contains data. Therefore, when the transmission target data including the time data is generated in step S101, the communication device 2 that transmits the data frame transmits the transmission data including the time data, the encryption key, and the hash function in step S102. Calculate the hash value for the target data this time. Further, the communication device 2 that has received the data frame calculates the hash value 1 by using the hash function and the reception target data including the time data in step S213. Further, the communication device 2 that has received the data frame calculates the hash value 2 by using the public key, the hash function, and the current hash value included in the first data frame.

In this way, if the time data indicating the current time is included in the transmission target data (or reception target data), the current hash value calculated by the communication device 2 on the transmission side and the reception side of the data frame matches the previous hash value. It becomes difficult. Therefore, according to the communication device 2 according to the third embodiment, it is possible to make it easier to specify the transmission order of the data frames in step S210 or the like.
<Fourth Embodiment>
As shown in FIG. 8, the data frame generated by the communication device 2 according to the fourth embodiment does not have to include an error detection code. FIG. 8 is a diagram showing a configuration example of a data frame generated by a communication device according to a fourth embodiment. FIG. 9 is a diagram showing an exemplary flow of transmission processing executed by the communication device according to the fourth embodiment. 10 (A) and 10 (B) are diagrams showing an exemplary flow of reception processing executed by the communication device according to the fourth embodiment.

As can be understood from the comparison between FIGS. 3 and 8, the data frame generated by the communication device 2 according to the fourth embodiment does not include an error detection code. Therefore, as shown in FIG. 9, the communication device 2 that transmits the data frame does not execute the process of step S105 for calculating the error detection code. Further, the communication device 2 that transmits the data frame generates a data frame that does not include the error detection code in step S106A.

Further, as shown in FIGS. 10A and 10B, the communication device 2 that has received the data frame extracts the reception target data and the hash value this time from the received data frame in step S202A. Further, in step S203A, the communication device 2 calculates the hash value 1 by using the hash function and the reception target data included in the received data frame. Further, in step S203A, the communication device 2 calculates the hash value 2 by using the public key, the hash function, and the current hash value included in the received data frame. Then, in step S204A, the communication device 2 determines whether or not the hash value 1 and the hash value 2 match. When it is determined that the hash value 1 and the hash value 2 do not match (“NO” in step S204A), in step S205, the communication device 2 discards the received data frame. On the other hand, when it is determined that the hash value 1 and the hash value 2 match (“YES” in step S204A), the communication device 2 proceeds to step S206. Subsequent processing is the same as reception processing performed by the communication device 2 according to the first embodiment.

As described above, the data frame generated by the communication device 2 according to the fourth embodiment does not include the error detection code, and the communication device 2 that has received the data frame uses a hash value instead of the error detection code. To verify the integrity of the data frame. Therefore, according to the communication device according to the fourth embodiment, the processing time for calculating the error detection code can be shortened. Further, as can be understood from the comparison between FIGS. 3 and 8, in the data frame according to the fourth embodiment, transmission target data (or reception target data) may be added instead of the error detection code. can.
<Fifth Embodiment>
As shown in FIG. 11, the size of each of the current hash value and the previous hash value included in the data frame may be half of the minimum data unit constituting the data frame. FIG. 11 is a diagram showing a configuration example of a data frame generated by the communication device according to the fifth embodiment.

As can be understood from the comparison between FIGS. 3 and 11, in the data frame generated by the communication device 2 according to the fifth embodiment, half of the minimum data units constituting the data frame are the previous hash value and the current time. Assign to each hash value. Specifically, for example, in a CAN-compliant data frame, 4 bits, which is half of the minimum data unit 1 byte constituting an 8-byte data frame, are allocated to the hash value this time and the hash value last time, respectively. As a result, the number of data that can be transmitted and received in the data frame can increase "data 6" as shown in FIG. 11 in addition to "data 1" to "data 5" as shown in FIG.

For example, in a data frame compliant with CAN FD, 4 bits, which is half of the minimum data unit 1 byte constituting a 64-byte data frame, may be allocated to the hash value this time and the hash value last time, respectively. Further, for example, in a data frame compliant with in-vehicle Ethernet, 4 bits, which is half of the minimum data unit 1 byte constituting the 46-byte data frame, may be allocated to the hash value this time and the hash value last time, respectively.

As described above, according to the fifth embodiment, the number of data that can be transmitted / received in the data frame can be increased.
<Sixth Embodiment>
As shown in FIG. 12, the magnitudes of the current hash value and the previous hash value may be twice or more the minimum data unit constituting the data frame. FIG. 12 is a diagram showing a configuration example of a data frame generated by the communication device according to the sixth embodiment.

As can be understood from the comparison between FIGS. 3 and 12, in the data frame generated by the communication device 2 according to the sixth embodiment, the hash value of the previous time is more than twice the minimum data unit constituting the data frame. And this time, it is assigned to each hash value. Specifically, for example, in a CAN-compliant data frame, three times (3 bytes) of the minimum data unit 1 byte constituting an 8-byte data frame is allocated to the hash value this time and the hash value of the previous time, respectively. In this case, the number of data that can be transmitted / received in the data frame is one (1 byte in total).

For example, in a data frame compliant with CAN FD, eight times (8 bytes) of the minimum data unit 1 byte constituting a 64-byte data frame may be allocated to the hash value this time and the hash value of the previous time, respectively. In this case, the number of data that can be transmitted / received in the data frame is 55 (55 bytes in total). Further, for example, in a data frame compliant with in-vehicle Ethernet, eight times (8 bytes) of the minimum data unit 1 byte constituting the 46-byte data frame may be allocated to the hash value this time and the hash value last time, respectively. In this case, the number of data that can be transmitted / received in the data frame is 29 (29 bytes in total).

As described above, according to the sixth embodiment, the security of communication can be enhanced by increasing the number of data of the hash value constituting the data frame.

1 Communication system 2 Communication device 3 Communication line 21 Control unit 22 Storage unit 23 Communication module 24 Bus 211 Hash value processing unit 212 Error detection code calculation unit 213 Data frame generation unit 214 Error detection unit 215 Data frame processing unit

Claims (11)

It ’s a transmitter,
A hash value processing unit that calculates a hash value for the transmission target data this time using a transmission target data, an encryption key, and a hash function, and a hash value processing unit.
A data frame generation unit that generates a data frame including the transmission target data, the current hash value, and the previous hash value calculated for the data previously transmitted prior to the transmission target data.
A communication module that transmits the data frame and
An error detection code calculation unit that calculates an error detection code based on the transmission target data, the current hash value, and the previous hash value .
Equipped with
The data frame generation unit is a transmission device that generates a data frame including the transmission target data, the current hash value, the previous hash value, and the error detection code. The transmitting device according to claim 1 .
The transmission target data includes time data indicating the current time. The transmitting device according to claim 1 or 2 .
A transmission device characterized in that the magnitudes of the current hash value and the previous hash value are half of the minimum data unit constituting the data frame. The transmitting device according to claim 1 or 2 .
A transmission device characterized in that the magnitudes of the current hash value and the previous hash value are at least twice the minimum data unit constituting the data frame. It is a receiving device
A communication module that receives a data frame including transmission target data, this time hash value, and the previous hash value calculated for the previously transmitted data prior to the transmission target data.
It is provided with a data frame processing unit that executes processing based on the reception target data included in the data frame when the current hash value and the previous hash value match.
Further provided with an error detection code calculation unit that calculates an error detection code based on the reception target data included in the received data frame, the current hash value, and the previous hash value.
When the error detection code calculated by the error detection code calculation unit and the error detection code extracted from the received data frame do not match, the data frame processing unit discards the received data frame. The receiving device. The receiving device according to claim 5 .
When there is a data frame waiting to be processed other than the received data frame, the received data frame and the said data frame according to the previous hash value included in the received data frame and the current hash value included in the waiting data frame. It also has an error detection unit that sorts the data frames waiting to be processed in the order in which the data frames are transmitted.
When the hash value included in the last processed data frame and the previous hash value included in the first data frame sorted in the transmission order of the data frame match, the hash value processing unit said. The first hash value is calculated using the hash function and the data included in the first data frame, and the public key specified in advance by the transmitting device, the hash function, and the present time included in the data frame. Calculate the second hash value using the hash value and
The receiving device is characterized in that the data frame processing unit executes processing based on the data included in the first data frame when the first hash value and the second hash value match. The receiving device according to claim 5 or 6 .
The receiving device, characterized in that the receiving target data includes time data indicating the current time. The receiving device according to any one of claims 5 to 7 .
A receiving device characterized in that the magnitudes of the current hash value and the previous hash value are half of the minimum data unit constituting the data frame. The receiving device according to any one of claims 5 to 7 .
A receiving device characterized in that the magnitudes of the current hash value and the previous hash value are at least twice the minimum data unit constituting the data frame. The receiving device according to any one of claims 5 to 9 .
When the receiving device is a communication history recording device that records the communication history between the transmitting device that transmitted the received data frame and another receiving device that is the destination of the received data frame, the data frame. The processing unit stores the hash value included in the received data frame in the hash value storage list, and waits for the reception of a new data frame without executing the processing based on the reception target data. Receiver. A communication method executed by a transmitting device and a receiving device.
The transmitter is
The hash value for the transmission target data is calculated this time using the transmission target data, the encryption key, and the hash function.
A data frame including the transmission target data, the current hash value, and the previous hash value calculated for the data previously transmitted prior to the transmission target data is generated.
Send the generated data frame and
The receiving device is
Receive the data frame and
The current hash value included in the previously processed data frame prior to the received data frame, and includes the current hash value calculated for the data included in the previously processed data frame and the received data frame. When the hash value is the previous hash value and the previous hash value calculated for the data previously transmitted prior to the reception target data included in the received data frame matches, the hash function and the reception target data are used. The first hash value is calculated using, and the second hash value is calculated using the public key specified in advance by the transmitting device, the hash function, and the current hash value included in the data frame. ,
A communication method comprising executing a process based on the reception target data when the calculated first hash value and the second hash value match.

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