JP7728068B2 - Control device and control method - Google Patents

Description

The present invention relates to a control device and a control method.

Conventionally, there is technology that uses random numbers generated by a control device to authenticate a device that updates a program executed by the control device. For example, this type of control device has technology that intermittently obtains timer values and updates a buffer used to generate random numbers (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2021-26290

However, with conventional technology, when a high-precision timer is used, the variation in the generated random numbers decreases, reducing authentication accuracy and potentially reducing security during program updates.

The present invention has been made in consideration of the above, and aims to provide a control device and control method that can increase the variance of random numbers.

To solve the above-mentioned problems and achieve the objectives, the control device according to the present invention includes a control unit. The control unit performs a buffer update process that updates a random number generation buffer based on a timer value each time the timer value is intermittently acquired, and a random number generation process that generates a random number used to authenticate the update control device that controls program updates, based on the updated buffer. During the period in which the buffer update process is being performed, the control unit changes the update timing of the buffer by performing a transmission process that transmits communication data to an external device and an interrupt process in response to the communication data received from the external device.

This invention makes it possible to increase the variance of random numbers.

FIG. 1 is a functional block diagram showing an example of the configuration of a program update system including a control device according to an embodiment. FIG. 2 is a functional block diagram illustrating an example of the configuration of the control device according to the embodiment. FIG. 3 is a diagram for explaining a method for updating entropy by the random number generation unit. FIG. 4 is a sequence diagram showing the procedure of the authentication process executed in the program update system according to the embodiment.

Embodiments of the control device and control method disclosed herein are described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

Figure 1 is a functional block diagram showing an example configuration of a program update system S including a control device 1 according to an embodiment. The program update system S shown in Figure 1 updates the program executed by the control device 1 using an update control device 100 authenticated by the control device 1.

As shown in FIG. 1, the program update system S according to the embodiment includes a control device 1, an engine 10, an external device 50, and an update control device 100.

The control device 1 is an ECU (Electronic Control Unit) mounted on the vehicle C, and executes the control method according to the embodiment. The control device 1 also performs control related to the vehicle C. In this disclosure, the control device 1 controls the engine 10 mounted on the vehicle C by executing a control program for the engine 10.

The control device 1 also communicates with the update control device 100 to update the control program of the engine 10. The control device 1 also performs processing related to authentication of the update control device 100. Specifically, when the control device 1 receives a random number request from the update control device 100, it generates a random number to be used to authenticate the update control device 100 and transmits it to the update control device 100.

Specifically, the control device 1 generates random numbers by performing a buffer update process and a random number generation process. The buffer update process is a process that updates the buffer used for random number generation based on the timer value each time the timer value is intermittently obtained. The random number generation process is a process that generates a random number used for authenticating the update control device 100 based on the buffer updated by the buffer update process. Details of the buffer update process and the random number generation process will be described later.

The control device 1 and the update control device 100 each generate an authentication key using a random number. The control device 1 then obtains the authentication key generated by the update control device 100 and performs authentication by comparing it with the authentication key it generated.

Here, conventionally, the period during which buffer update processing is performed is fixed. Therefore, when a high-precision timer is used, the lag in the buffer update timing becomes small, which can lead to a decrease in the variance in the generated random numbers. As a result, using such random numbers can reduce authentication accuracy, potentially reducing security during program updates.

The control device 1 according to the embodiment therefore changes the buffer update timing by performing interrupt processing during the period in which the buffer update process is being performed.

Specifically, during the period when the buffer update process is being performed, the control device 1 changes the buffer update timing by performing a transmission process to send communication data to the external device 50 and an interrupt process in response to the communication data received from the external device 50.

In other words, the control device 1 according to the embodiment temporarily interrupts the buffer update process, which is performed at regular intervals, and interrupts it with another process, thereby intentionally shifting the update timing of the buffer update process.

In addition, the time required from sending communication data to receiving a response depends on the processing status of the external device 50 and is therefore not constant each time. In other words, the timing of interrupt processing will not be the same each time.

As a result, the control device 1 performs interrupt processing at different times each time, changing the update timing at various times and thereby varying the entropy of the buffer. In other words, the control device 1 according to the embodiment can increase the variation in the random numbers generated by the buffer.

The control device 1 according to the embodiment will be described in detail below with reference to Figure 2 and subsequent figures.

Next, an example functional configuration of the control device 1 according to the embodiment will be described using Figure 2. Figure 2 is a functional block diagram showing an example configuration of the control device 1 according to the embodiment. The control device 1 shown in Figure 2 is connected to the engine 10, an external device 50, and an update control device 100.

The engine 10 is the power source for the vehicle C. The engine 10 generates power under the control of the control device 1, and applies the rotational force obtained from the generated power to the drive wheels of the vehicle C.

The external device 50 is, for example, an ECU that controls the vehicle C. Note that the external device 50 is not limited to an ECU, and may also be an external server, etc. In other words, the external device 50 may be any device that is capable of two-way communication with the control device 1.

The update control device 100 is, for example, a terminal device owned by the worker performing the update work, and is detachably connected to the control device 1. The update control device 100 can be any type of terminal device, such as a smartphone, desktop PC, laptop PC, or tablet PC.

As shown in FIG. 2, the control device 1 includes a control unit 2 and a memory unit 3. The control unit 2 includes a vehicle control unit 21, an update control unit 22, and a clock generation unit 23. The memory unit 3 stores a first program 31, a second program 32, and a buffer 33.

The control unit 2 includes a microcomputer with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various other circuits. The control unit 2 controls the operation of the control device 1 by having the CPU execute programs stored in the ROM using the RAM as a working area. The control unit 2 may also be configured with hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). The memory unit 3 is configured with storage devices such as non-volatile memory, flash memory, or a hard disk drive.

In this disclosure, the first program 31 is a control program for the engine 10 and is a program to be updated by the update control device 100. The first program 31 is executed by the vehicle control unit 21.

The second program 32 is a program for updating the first program 31. The second program 32 is executed by the update control unit 22.

Buffer 33 stores entropy 331 for generating random numbers used to authenticate the update control device 100.

Next, we will explain each function of the control unit 2 (vehicle control unit 21, update control unit 22, and clock generation unit 23).

The vehicle control unit 21 executes the first program 31 stored in the memory unit 3 to control the engine 10.

The update control unit 22 executes the second program 32 stored in the memory unit 3 to update the first program 31 stored in the memory unit 3. The functional configuration of the update control unit 22 will be described later.

The clock generation unit 23 generates multiple clock signals with different frequencies. The clock generation unit 23 outputs the generated clock signals to the vehicle control unit 21 and the update control unit 22. The vehicle control unit 21 and the update control unit 22 operate in synchronization with the clock signals. The clock signals are also used to generate timer values in the buffer update process of the update control unit 22.

Next, the functional configuration of the update control unit 22 will be described in detail. As shown in FIG. 2, the update control unit 22 includes an authentication unit 221, a random number generation unit 222, an authentication key generation unit 223, and a timing change unit 224.

The authentication unit 221 communicates with the update control device 100 to authenticate the update control device 100. Specifically, when the authentication unit 221 receives a random number request from the update control device 100 requesting the transmission of a random number, it transmits a random number generated by the random number generation unit 222 (described below) to the update control device 100.

In addition, after transmitting the random number to the update control device 100, the authentication unit 221 obtains an authentication key generated based on the random number from the update control device 100, and also obtains an authentication key generated by the authentication key generation unit 223, which will be described later.

Then, the authentication unit 221 authenticates the update control device 100 based on the authentication key generated by the update control device 100 and the authentication key generated by the authentication key generation unit 223, and transmits the authentication result to the update control device 100.

Specifically, if the authentication key generated by the update control device 100 matches the authentication key generated by the authentication key generation unit 223, the authentication unit 221 authenticates the update control device 100 and notifies the update control device 100 that it has been authenticated.

On the other hand, if the authentication key generated by the update control device 100 does not match the authentication key generated by the authentication key generation unit 223, the authentication unit 221 notifies the update control device 100 that the update control device 100 cannot be authenticated. At this time, the authentication unit 221 may request the update control device 100 to regenerate (or resend) the authentication key.

The random number generation unit 222 executes the buffer update process and random number generation process shown in Figure 1. The random number generation unit 222 executes the buffer update process using the clock signal received from the clock generation unit 23.

First, in the buffer update process, the random number generation unit 222 counts each clock signal with a different frequency received from the clock generation unit 23. The random number generation unit 222 obtains each count value of the clock signal as a timer value, and updates each bit value of the entropy 331 stored in the buffer 33 based on each timer value. The method for updating the entropy 331 will be described later using Figure 3.

When the random number generation unit 222 receives a random number request from the update control device 100, it terminates the buffer update process and performs random number generation processing. Specifically, when the random number generation unit 222 receives a random number request from the update control device 100, it reads entropy 331 from buffer 33 and converts the read entropy 331 into a random number.

Note that the algorithm for generating random numbers is not limited as long as the random numbers are generated based on entropy 331. Furthermore, the random numbers may be true random numbers or pseudo-random numbers.

In addition, when transmission processing or interrupt processing is performed by the timing change unit 224 (described later), the random number generation unit 222 temporarily suspends the buffer update processing and resumes the buffer update processing after the transmission processing or interrupt processing is completed.

Furthermore, it is preferable that the random number generation unit 222 set the processing priority of the buffer update process lower than other processes executed by the control unit 2 other than interrupt processing. This allows processes other than interrupt processing to be given priority over the buffer update process, thereby making it possible to vary the entropy 331.

The random number generation unit 222 sends the generated random number to the authentication key generation unit 223 and also to the update control device 100 via the authentication unit 221.

The authentication key generation unit 223 generates an authentication key using the random number received from the random number generation unit 222. The authentication key generation unit 223 outputs the generated authentication key to the authentication unit 221. The algorithm used to generate the authentication key is not particularly limited. For example, the Advanced Encryption Standard (AES) is used to generate the authentication key. The encryption key used to generate the authentication key in the authentication key generation unit 223 may be the same as or different from the encryption key used to generate the authentication key in the update control device 100.

The timing change unit 224 changes the update timing of the buffer 33 during the buffer update process by performing a transmission process to send communication data to the external device 50 and an interrupt process in response to communication data received from the external device 50 while the buffer update process is being performed by the random number generation unit 222.

For example, the timing change unit 224 performs the transmission process at a predetermined timing during the period in which the buffer update process is being performed. The timing of the transmission process may be fixed, such as a predetermined time (e.g., one second) after the start of the buffer update process, or may be random.

Alternatively, the timing change unit 224 may perform the transmission process in response to a notification sent from the external device 50. Furthermore, the transmission process may be performed multiple times rather than just once, and the number of times the transmission process is performed may vary each time.

Furthermore, the communication data sent is dummy data that includes only a response request to the control device 1. In other words, when the external device 50 receives the communication data, it does not perform any processing other than responding to the control device 1. This allows the processing performed by the external device 50 to be minimized (only responding to the control device 1).

The communication data may be data that instructs the external device 50 to respond after performing a specified process. This causes variation in the timing at which a response to the communication data is received, thereby making it possible to further vary the entropy 331.

Then, after performing the transmission process, the timing change unit 224 performs interrupt processing to receive a response to the communication data transmitted from the external device 50. As a result, the buffer processing by the random number generation unit 222 is temporarily suspended and the interrupt processing by the timing change unit 224 is performed, thereby varying the entropy 331 in the buffer 33.

Note that the interrupt processing is a process that simply receives a response to the communication data, and it is preferable that no processing other than the reception processing is performed on the response to the communication data. This makes it possible to vary the entropy 331 while minimizing the processing load on the update control unit 22.

Next, we will use Figure 3 to explain how the random number generation unit 222 updates entropy 331. Figure 3 is a diagram for explaining how the random number generation unit 222 updates entropy 331. Figure 3 explains an update method using three timer values (first timer value to third timer value) obtained from three clock signals with different frequencies.

As shown in FIG. 3, the random number generation unit 222 first performs a logical operation on any two of the first to third timer values. In the example shown in FIG. 3, the random number generation unit 222 extracts the least significant bit values (bold frames) of the first and third timer values and calculates the exclusive OR 200. In FIG. 3, if the least significant bit value of the first timer value is "1" and the least significant bit value of the third timer value is "0," the output bit value of the exclusive OR 200 is "1."

Next, the random number generation unit 222 performs a logical operation on the output bit value of the obtained exclusive OR 200 and the least significant bit value of the second timer value. In the example shown in Figure 3, the random number generation unit 222 obtains the exclusive OR 201 of the output bit value of the obtained exclusive OR 200 and the least significant bit value of the second timer value. In Figure 3, when the output bit value is "1" and the least significant bit value of the second timer value is "0", the output bit value of the exclusive OR 201 is "1".

Next, the random number generation unit 222 performs a logical operation on the output bit value of the exclusive OR 201 and the least significant bit value of the pre-update entropy 331 stored in the buffer 33 stored in the memory unit 3. In the example shown in Figure 3, the exclusive OR 202 is calculated between the output bit value of the exclusive OR 201 and the least significant bit value of the pre-update entropy 331. In Figure 3, if the output bit value is "1" and the least significant bit value of the pre-update entropy 331 is "1", then "0" is output as the output bit value of the exclusive OR 202.

The random number generation unit 222 then updates the entropy 331 by replacing the least significant bit value of the entropy 331 before the update with the output bit value of the exclusive OR 202. In the example shown in Figure 3, the least significant bit value "1" of the entropy 331 before the update is updated to the least significant bit value "0" after the update.

In other words, the random number generation unit 222 updates the entropy 331 of the buffer 33 using the value resulting from the logical operation of the three timer values and the entropy 331 before the update. In this way, by performing a buffer update process that includes elements of the three timer values and the entropy 331 before the update, it is possible to vary the entropy 331.

In addition, by using three timer values with different frequencies, the randomness of the results of the logical operation of the three timer values can be increased, thereby varying the entropy 331.

Note that Figure 3 shows an example of updating the least significant bit value of entropy 331, but after updating the least significant bit value, the bit value one level higher is updated using the same update method as shown in Figure 3. In other words, after updating the bit value at the current update position, the buffer update process is performed with the bit value one level higher as the new update position. Then, when the update of the most significant bit value is complete, the buffer update process returns to the least significant bit value and is performed again.

Note that the buffer update process is not limited to exclusive OR, but may also be logical OR, logical AND, or a combination of multiple types of logical operations. Furthermore, the timer value used in the logical operation is not limited to the least significant bit value, but may be a bit value at any position.

Next, the authentication process steps executed in the program update system S according to the embodiment will be described using Figure 4. Figure 4 is a sequence diagram showing the processing steps of the authentication process executed in the program update system S according to the embodiment. The authentication process shown in Figure 4 is performed by the driver (owner) of vehicle C when the vehicle C is brought to a dealer. At the dealer, an operator connects the update control device 100 to the control device 1 and starts communication with the control device 1, thereby performing the authentication process.

As shown in FIG. 4, first, the update control device 100 sends a repro mode transition request (step S1). Repro mode is a mode in which a second program that updates a program is executed, and the repro mode transition request is a message instructing the control device 1 to start the update control unit 22.

Next, when the control device 1 receives a repro mode transition request from the update control device 100, it sends a repro mode transition response to the update control device 100 (step S2). The repro mode transition response is a message notifying the start of the transition to repro mode.

When the update control device 100 receives a repro mode transition response from the control device 1, it waits until a preset waiting time has elapsed, and after the waiting time has elapsed, it executes step S10, which will be described later. The waiting time is determined based on the repro mode transition time required for the control device 1 to stop the vehicle control unit 21 and start the update control unit 22. Specifically, the waiting time should be longer than the repro mode transition time.

After transmitting the reproduction mode transition response, the control device 1 executes a reset process (step S3). Specifically, the reset process stops the vehicle control unit 21 (stops execution of the first program 31) and starts the update control unit 22 (starts execution of the second program 32).

Next, the control device 1 activates the update control unit 22 and acquires the timer value (step S4). Next, the control device 1 updates the value of one bit among the bit values in the entropy 331 of the buffer 33 based on the acquired timer value (step S5).

Next, the control device 1 executes a transmission process to transmit communication data to the external device 50 (step S6). Note that the transmission process can be performed at any timing during the standby time (the time from step S2 to step S10). Also, while Figure 4 shows an example in which the transmission process is performed once, it may be performed two or more times.

Next, the control device 1 executes interrupt processing in response to the communication data received from the external device 50 (step S7). Note that the control device 1 may wait for the buffer update processing (obtaining the timer value and updating the buffer) between steps S6 and S7, or may perform the buffer update processing until the communication data response is received in step S7.

Next, the control device 1 acquires the timer value (step S8) and updates the value of one bit among the bit values in the entropy 331 of the buffer 33 based on the acquired timer value (step S9).

Next, after the waiting time has elapsed, the update control device 100 sends a random number request requesting the transmission of a random number (step S10). The random number request is a message requesting the transmission of a random number used to authenticate the update control device 100.

Next, when the control device 1 receives a random number request from the update control device 100, it terminates the buffer update process and obtains the updated buffer 33 (step S11).

The control device 1 then generates a random number using the entropy 331 stored in the acquired buffer 33 (step S12). The control device 1 then transmits a random number response including the generated random number to the update control device 100 (step S13).

Next, the control device 1 and the update control device 100 each generate an authentication key using a random number (step S14). Next, the update control device 100 transmits the generated authentication key to the control device 1 (step S15).

Next, the control device 1 performs authentication processing for the update control device 100 by comparing the authentication key it generated with the authentication key received from the update control device 100 (step S16).

The control device 1 then transmits an authentication result response to the update control device 100, including an authentication result based on the comparison result of the authentication keys (step S17). For example, if the two authentication keys match, the control device 1 transmits an authentication result response indicating that the update control device 100 has been authenticated; if the two authentication keys do not match, the control device 1 transmits an authentication result response indicating that the update control device 100 cannot be authenticated.

As described above, the control device 1 according to the embodiment includes a control unit 2. The control unit 2 performs a buffer update process that updates the random number generation buffer 33 based on the timer value each time the timer value is intermittently acquired, and a random number generation process that generates a random number used to authenticate the update control device 100 that controls the update of the program (first program 31) based on the updated buffer 33. While the buffer update process is being performed, the control unit 2 changes the update timing of the buffer 33 by performing a transmission process that transmits communication data to the external device 50 and an interrupt process in response to communication data received from the external device 50. This allows for greater variation in the random numbers.

Further advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

REFERENCE SIGNS LIST 1 control device 2 control unit 3 storage unit 10 engine 21 vehicle control unit 22 update control unit 23 clock generation unit 31 first program 32 second program 33 buffer 50 external device 100 update control device 221 authentication unit 222 random number generation unit 223 authentication key generation unit 224 timing change unit 331 entropy C vehicle S program update system

Claims (7)

a control unit that performs a buffer update process that updates a buffer for random number generation based on a timer value every time the timer value is intermittently acquired, and a random number generation process that generates a random number used for authenticating an update control device that controls program updates based on the updated buffer,
The control unit
a control device that changes the update timing of the buffer by performing a transmission process for transmitting communication data to an external device and an interrupt process in response to the communication data received from the external device during the period in which the buffer update process is being performed. The control unit
2. The control device according to claim 1, wherein the buffer update process is performed to update the entropy stored in the buffer based on a logical operation result of a plurality of the timer values generated based on clock signals with different frequencies. The control unit
3. The control device according to claim 2, wherein the entropy before update is updated based on a result of a logical operation between the plurality of timer values and the entropy before update. The control unit
4. The control device according to claim 1, wherein the buffer update process is set to have a lower processing priority than other processes executed by the control unit other than the interrupt process. The interrupt processing includes:
5. The control device according to claim 1, wherein the process is to receive a response to the communication data. The communication data is
6. The control device according to claim 1, wherein the control device includes only a response request for requesting a response to the communication data. a control step of performing a buffer update process for updating a buffer for random number generation based on a timer value every time the timer value is intermittently acquired, and a random number generation process for generating a random number to be used for authenticating an update control device that controls program updates based on the updated buffer,
The control step includes:
a control method characterized by changing the update timing of the buffer by performing a transmission process for transmitting communication data to an external device and an interrupt process in response to the communication data received from the external device during the period in which the buffer update process is being performed.