KR20210094932A - Device and Method for Schedulability Verification of Security Reinforcement Techniques in Real time Devices - Google Patents

Abstract

A device for verifying the schedulability of security reinforcement techniques in a real-time device comprises: a basic task assignment unit for allocating, to a processor, at least one basic task with a set deadline; an additional task allocation unit allocating, to the processor, an additional task, which has the highest priority compared to each of the assigned basic tasks and to which a security enhancement technique is applied, so that the additional task is performed before execution of each basic task; a task performance unit for performing a task in accordance with the priorities of the assigned basic task and each additional task; and a deadline determination unit for calculating, in real time, a time in point corresponding to the least common multiple of the periods of the basic task from a process in which the task is performed, and determining whether deadline of the basic task is met on the basis of the calculated time in point. Therefore, the device can dynamically verify the schedulability of an independent security enhancement technique while variously changing and applying the independent security enhancement technique in an environment of the real-time device.

Description

Device and Method for Schedulability Verification of Security Reinforcement Techniques in Real time Devices

The present invention relates to a technology for verifying the schedulability of application of security enhancement, and more particularly, security in a real-time device that dynamically verifies its schedulability while variously changing and applying an independent security enhancement technology in a real-time device environment. The present invention relates to an apparatus and method for verifying schedulability of a sexual enhancement technique.

Recently, security attacks on real-time devices used in autonomous vehicles, smart factories, and power grids have become a problem. An attack that malfunctioned the car by injecting the highest packet into the car's CAN bus (a type of Denial-of-Service attack) occurred in the United States, and an incident occurred in which a hacker controlled the furnace by infecting the factory automation control system. . In addition, the possibility of cyberattacks on infrastructure such as airport systems, power grids, and power plants is increasing.

Accordingly, various security reinforcement techniques are being developed to prevent cyber attacks on real-time devices as described above. Representative cyber attacks include firmware tampering attacks, unauthorized data access, replay attacks, and arbitrary ladder logic execution.

Meanwhile, as a counter measure for this, security enhancement technologies such as integrity check, data encryption, runtime overflow attack detection, and traffic monitoring are applied. However, application of this security enhancement technology requires a new schedulability verification in a real-time device. The reason is that the task performed on the real-time machine has a real-time constraint that it must meet the deadline. Accordingly, verifying whether all tasks satisfy the deadline is called schedulability verification.

However, a security enhancement technique that checks whether or not its own code is tampered with before a specific task is performed increases the execution time of the task and may cause a problem of violating scheduleability.

Therefore, there is a need to develop a security enhancement technique that still satisfies the real-time constraint despite the increased execution time or still satisfies the real-time constraint regardless of a given environment.

In addition, various techniques have been proposed to verify whether a real-time device satisfies the deadline, that is, schedulability, but most of them calculate the worst case execution time (WCET) using static analysis and determine whether it satisfies the deadline. Verification is common. Accordingly, there is a need to develop a technology for dynamically verifying security enhancement technology by changing it in various ways, that is, for immediate verification or incremental verification.

Japanese Laid-Open Patent Publication No. 2007-219937

Accordingly, the present invention has been proposed in consideration of the above matters, and it is an object of the present invention to dynamically verify schedulability while variously changing and applying an independent security enhancement technique in a real-time device environment.

In addition, the present invention adopts a black box approach, and an object of the present invention is to verify schedulability even if the existing source code is not disclosed.

In addition, an object of the present invention is to enable it to be easily applied to various security enhancement technologies.

In addition, the present invention uses dynamic analysis, and an object of the present invention is to enable immediate verification or incremental verification while modifying a security enhancement technique.

Further, it is an object of the present invention to obtain maximum security enhancement in a given environment.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the schedulability verification apparatus according to the application of the security enhancement technology in a real-time device according to the technical idea of the present invention includes a basic task allocator for allocating at least one or more basic tasks for which a deadline is determined to a processor; An additional task allocator that has the highest priority compared to each of the assigned basic tasks and assigns an additional task to which a security enhancement technology is applied to the processor to be performed before each basic task is performed, the assigned basic task and the priority for each additional task A task performing unit that performs a task according to the ranking, calculates in real time a time point corresponding to the least common multiple of the periods of the basic task from the process in which the task is performed, and determines whether the deadline of the basic task is satisfied based on this It may include a deadline determination unit.

In this case, the additional task may be a task to which a security enhancement technique is applied by a scheduler or by using a semaphore.

The deadline determination unit may determine whether the deadline of the basic task is satisfied according to a determination expression of whether the deadline is satisfied of the task expressed by Equation 1 below.

<Equation 1>

Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )

(T _i : the i-th task, LCM: a time point corresponding to the least common multiple of the cycles of the basic task, P _i : the cycle of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test)

On the other hand, the schedulability verification apparatus according to the application of the security enhancement technology in the real-time device according to the technical idea of the present invention includes a priority reversal time detection unit that detects in real time a time when the priority is reversed from the process of performing the task, It may further include a priority control unit for controlling the priority of the basic task when the detected priority is reversed.

The priority control unit lowers the priority of the additional task and then controls the priority of the basic task and the additional task by using a priority inheritance protocol, or by using a shadow task The priority of the basic task and the additional task may be controlled by performing security enhancement for each basic task and the additional task.

In order to achieve the above object, the schedulability verification method according to the application of the security enhancement technology in the real-time device according to the technical idea of the present invention is to allocate at least one basic task with a set deadline to the processor in the basic task allocator. A basic task assignment step, an additional task assignment step of assigning an additional task having the highest priority compared to each of the assigned basic tasks in the additional task allocating unit to the processor to be performed before each basic task is performed, to which a security enhancement technology is applied; A time point corresponding to the least common multiple of the periods of the basic task from the task performing step of performing the task according to the priority of the assigned basic task and the additional task in the task performing unit, and the process of performing the task in the deadline determining unit The calculation may include a deadline determining step of determining whether the deadline of the basic task is satisfied based on the calculation in real time.

In this case, the additional task may be a task to which a security enhancement technique is applied by a scheduler or by using a semaphore.

In the step of determining the deadline, it may be determined whether the deadline of the basic task is satisfied according to the formula for determining whether the deadline of the task is satisfied by Equation 1 below.

<Equation 1>

Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )

(T _i : the i-th task, LCM: a time point corresponding to the least common multiple of the cycles of the basic task, P _i : the cycle of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test)

On the other hand, the schedulability verification method according to the application of the security enhancement technology in the real-time device according to the technical idea of the present invention is to detect in real time the time when the priority is reversed from the process of performing the task in the priority reversal time detection unit. The method may further include a priority control step of controlling the priority of the basic task at a time point when the priority detected by the priority control unit is reversed.

The priority control step may include lowering the priority of the additional task and then controlling the priorities of the basic task and the additional task using a priority inheritance protocol, or using a shadow task The priority of the basic task and the additional task may be controlled by performing security enhancement for each of the basic task and the additional task.

According to the schedulability verification apparatus and method of the security enhancement technology in the real-time device as described above,

First, it has the effect of dynamically verifying its scheduleability while variously changing and applying independent security enhancement technology in a real-time device environment.

Second, by adopting the black box approach, it has the effect of verifying the schedulability even if the existing source code is not disclosed.

Third, it has an effect that can be easily applied to various security enhancement technologies.

Fourth, by using dynamic analysis, it has the effect that immediate verification or incremental verification is possible while modifying the security enhancement technology.

Fifth, it has the effect of obtaining maximum security reinforcement in a given environment.

1 is a view showing a task performance result when a security enhancement technology is not applied in a general real-time device.
2 is a view showing a task performance result when a security enhancement technology is applied in a general real-time device.
3 is a view showing a result of an increase in task execution time by a security enhancement test in a general real-time device.
4 is a block diagram illustrating an apparatus for verifying scheduleability of a security enhancement technique in a real-time device as an embodiment of the present invention;
5 is a flowchart illustrating a method for verifying scheduleability of a security enhancement technique in a real-time device as an embodiment of the present invention;
6 is a flowchart illustrating a priority control process in a method for verifying scheduleability of a security enhancement technique in a real-time device as an embodiment of the present invention;
7 is a diagram illustrating a task execution process according to the application of a security enhancement technology in a real-time device as an embodiment of the present invention.
8 is a diagram illustrating a schedulability verification result of a security enhancement technique in a real-time device as an embodiment of the present invention;

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings. The features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Prior to this, the terms or words used in the present specification and claims are based on the technical idea of the present invention based on the principle that the inventor can appropriately define the concept of the term in order to describe his invention in the best way. It should be interpreted with the corresponding meaning and concept. In addition, it should be noted that, when it is determined that the detailed description of known functions and configurations related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof is omitted.

1 is a diagram illustrating a task performance result when a security enhancement technology is not applied in a general real-time device. At this time, including FIG. 1, the tasks in the general real-time device shown in FIGS. 2 and 3 below are composed of three tasks. And, the three tasks may be called basic tasks.

,

,

은 각각 5, 10, 20이라는 주기를 가질 수 있다. 0 시점에서 주기가 가장 적은

은 우선적으로 스케줄링될 수 있다. 그리고

의 수행이 완료되면, 그 이후

,

가 순서대로 스케줄링될 수 있다. 각 태스크는 주기적으로 다시 스케줄링이 될 수 있다.Each task in a typical real-time device shown in FIG. 1 is

,

,

may have a period of 5, 10, and 20, respectively. At time 0, the period with the fewest

may be preferentially scheduled. And

After the execution of

,

may be scheduled in order. Each task can be re-scheduled periodically.

) 완료를 보장받아야 실시간 제약조건을 만족할 수 있다.If two or more tasks are to be simultaneously performed at the same time, the order may be determined by priority. On the other hand, all tasks have their own task execution time (

) must be guaranteed to satisfy the real-time constraint.

2 is a view showing a task performance result when a security enhancement technology is applied in a general real-time device.

)이 보안성 강화 검사를 수행하는 시간(

)만큼 늘어날 수 있다. 이 때 늘어난 수행시간(

)은 여전히 실시간 제약조건, 즉 주기 이전에 태스크 수행이 완료되는 것을 만족해야한다.FIG. 2 can be said to be a representative example of a security enhancement technique, such as data encryption that checks whether an execution image has been tampered with before performing a task, or checks a stack overflow during task execution. When the security enhancement technology is applied, the execution time of each task (

) the time (

) can be increased by In this case, the increased execution time (

) must still satisfy the real-time constraint, that is, that the task is completed before the cycle.

3 is a view showing a result of an increase in task execution time by a security enhancement test in a general real-time device.

의 증가에 따른 다양한 시나리오로서, 도 3(a)은

에 의해

가 증가되었으나 여전히 실시간 제약조건을 만족하는 경우를 나타낸 도면이고, 도 3(b)은

가 더 증가되어 선점이 발생되었으나 여전히 실시간 제약조건을 만족하는 경우를 나타낸 도면이고, 도 3(c)은

가 더욱 증가되어 실시간 제약조건을 만족하지 못하는 경우를 나타낸 도면이다.In more detail, Figure 3

As various scenarios according to the increase of

by

is increased, but still satisfies the real-time constraint, and FIG. 3(b) is

It is a diagram showing a case where preemption occurred but still satisfies the real-time constraint by increasing

It is a diagram showing a case in which the real-time constraint is not satisfied due to further increase.

In FIG. 3(b) , a new cycle of Task 1 is started at time 5 while Task 3 is being performed, and Task 3 may be preempted because it has a lower priority than Task 1. In other words, it can be said that Task 3 stops execution and Task 1 is executed. After that, when the execution of Task 1 is completed, Task 3 may resume execution. Also, it can be said that all tasks satisfy the real-time constraint.

가 더욱 증가되어 실시간 제약조건을 위배하는 경우라 할 수 있다. 즉, Task 3이 자신의 주기 30 동안에 수행해야할

시간을 할당받지 못해 마감시간을 위반하게 되는 것이다.In Fig. 3(c)

It can be said that it is a case of violating the real-time constraint by increasing further. That is, task 3 must perform during its cycle 30.

If you are not allotted time, you will be breaking the deadline.

If the application of the security enhancement technology does not satisfy the real-time constraint, a big problem may occur in the real-time device. Accordingly, when the security enhancement technology is applied, a new technology capable of accurately verifying the schedulability is required.

For this, several issues must be considered.

First, various technologies must be applied to enhance security. This means that new technologies should be easily adaptable to a variety of technologies.

Second, many commercial real-time devices do not want to disclose their source code. Therefore, it should be possible to verify the application of security enhancement and the schedulability without modifying existing tasks (or allowing only minimal modifications).

Third, since the designer tries to enhance security as much as possible, it should be possible to quantitatively suggest the range of security enhancement technology that can be applied maximally while satisfying real-time in a given system condition.

4 is a block diagram illustrating an apparatus for verifying scheduleability of a security enhancement technique in a real-time device as an embodiment of the present invention.

Referring to FIG. 4 , as an embodiment of the present invention, an apparatus for verifying schedulability of a security enhancement technology in a real-time device is largely a basic task assignment unit 100 , an additional task assignment unit 200 , a task performing unit 300 , It may include a deadline determination unit 400 .

The basic task allocator 100 may allocate at least one or more basic tasks for which a deadline is determined to the processor. This can be said to be a component for being assigned a basic task to be performed in a real-time device environment.

The additional task allocator 200 may allocate an additional task to the processor to be performed before each basic task allocated from the basic task allocator 100 is performed. This can be said to be a component for being assigned a separate task in order to variously change and apply independent security enhancement technology in a real-time device environment. In this case, the additional task has the highest priority compared to each of the assigned basic tasks, and may be a task to which the security enhancement technology is applied. Additionally, additional tasks have no periodicity and can be performed first before each basic task is started.

On the other hand, the additional task may be a task to which a security enhancement technology is applied by a scheduler or by using a semaphore. The reason is that in order to perform additional tasks for the security enhancement check, it must be started using a scheduler or notified using a semaphore.

The task performing unit 300 may perform a task according to the priority of the basic task allocated from the basic task allocator 100 and the additional task allocated from the additional task allocator 200 . This can be said to be a component in which the execution order of tasks is determined and performed according to the priority of each task.

The deadline determining unit 400 calculates in real time a time point corresponding to the least common multiple of the cycles of the basic task from the process in which the task performing unit 300 is performed, and determines whether the deadline of the basic task is satisfied based on this can judge This is a component for dynamically verifying the schedulability of each task while variously changing and applying independent security enhancement technology in a real-time device environment.

At this time, the deadline determining unit 400 may determine whether the deadline of the basic task is satisfied according to the task for determining whether the deadline is satisfied, expressed by Equation 1 below.

<Equation 1>

Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )

(T _i : i-th task, LCM: a time point corresponding to the least common multiple of the periods of the basic task, P _i : the period of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test)

Meanwhile, as shown in FIG. 4 , an apparatus for verifying scheduleability of a security enhancement technology in a real-time device as an embodiment of the present invention may include a priority reversal time detection unit 500 and a priority control unit 600 . .

The priority reversal time detection unit 500 may detect in real time a time at which the priority is reversed from the process in which the task is performed by the task execution unit 300 . This may be referred to as a component for detecting a priority inversion problem in which the priority of tasks is inverted by an additional task having the highest priority during execution of basic tasks.

The priority control unit 600 may control the priority of the basic task when the priority detected by the priority reversal time detection unit 500 is reversed. This can be said to be a component for solving the problem of priority inversion that may be caused by allocating an additional task having the highest priority.

In more detail, the priority control unit 600 may lower the priority of the additional task and then control the priority of the basic task and the additional task by using a priority inheritance protocol. Alternatively, the priority control unit 600 may control the priority of the basic task and the additional task by performing security enhancement for each of the basic task and the additional task using a shadow task. The reason for using the priority inheritance protocol or shadow task to control the priority is as follows.

Additional tasks should initially have the lowest priority. That way, it doesn't interfere with other tasks, that is, the basic tasks. However, when execution starts for the security enhancement check, it should be performed by raising the priority of the related task, not the low priority. For this, a priority inheritance protocol is used to control the priority of tasks. Furthermore, as a method that can be used for priority control instead of the priority inheritance protocol, a shadow task having the same priority as the associated task may be used.

5 is a flowchart illustrating a method for verifying schedulability of a security enhancement technology in a real-time device as an embodiment of the present invention, and FIG. 6 is an embodiment of the present invention, schedulability verification of a security enhancement technology in a real-time device. It is a flowchart showing the priority control process in the method.

First, referring to FIG. 5 , as an embodiment of the present invention, the schedulability verification method of the security enhancement technology in a real-time device is largely a basic task assignment step (S100), an additional task assignment step (S200), and a task execution step (S300). , it may include a deadline determining step (S400).

In the basic task allocation step, the basic task allocator 100 may allocate at least one basic task for which a deadline is set to the processor ( S100 ). This can be said to be a step for receiving a basic task to be performed in a real-time device environment.

In the additional task assignment step, the additional task assignment unit 200 may assign an additional task to the processor to be performed before each basic task assigned from the basic task assignment step S100 is performed (S200). This is a step to be assigned a separate task in order to variously change and apply independent security enhancement technology in a real-time device environment. In this case, the additional task has the highest priority compared to each of the assigned basic tasks, and may be a task to which the security enhancement technology is applied. Additionally, additional tasks have no periodicity and can be performed first before each basic task is started.

On the other hand, the additional task may be a task to which a security enhancement technology is applied by a scheduler or by using a semaphore. The reason is that in order to perform additional tasks for the security enhancement check, it must be started using a scheduler or notified using a semaphore.

In the task performing step, the task performing unit 300 may perform a task according to the priority of the basic task assigned from the basic task assignment step S100 and the additional task assigned from the additional task assignment step S200 ( S300). This can be said to be a step in which the execution order of the tasks is determined and performed according to the priority of each task.

The deadline determining step calculates in real time a time point corresponding to the least common multiple of the cycles of the basic task from the process in which the task performing step (S300) is performed in the deadline determining unit 400, and based on this, It may be determined whether the deadline is met (S400). This is a step to dynamically verify the schedulability of each task while variously changing and applying independent security enhancement technology in a real-time device environment.

In this case, the deadline determining step ( S400 ) may determine whether the deadline of the basic task is satisfied according to an expression for determining whether the deadline is satisfied of the task expressed by Equation 1 below.

<Equation 1>

Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )

(T _i : the i-th task, LCM: a time point corresponding to the least common multiple of the cycles of the basic task, P _i : the cycle of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test)

Meanwhile, as shown in FIG. 6 , the priority control process in the schedulability verification method of the security enhancement technology in a real-time device as an embodiment of the present invention includes a basic task assignment step (S100) and an additional task assignment step (S200) , along with the task performing step (S300), may further include a priority reversal time detection step (S500) and a priority control step (S600).

In the priority reversal time detection step, the priority reversal point detection unit 500 may detect in real time a time point at which the priority is reversed from the process in which the task is performed by the task execution step S300 ( S500 ). This may be referred to as a step for detecting a priority inversion problem in which the priority of tasks is inverted by an additional task having the highest priority during execution of basic tasks.

The priority control step may control the priority of the basic task at the point in time when the priority detected by the priority reversal time detection step (S500) in the priority control unit 600 is reversed (S600). This is a step to solve the priority inversion problem that may be caused by allocating an additional task having the highest priority.

In more detail, the priority control step S600 may lower the priority of the additional task and then control the priority of the basic task and the additional task using a priority inheritance protocol. Alternatively, the priority control unit 600 may control the priority of the basic task and the additional task by performing security enhancement for each of the basic task and the additional task using a shadow task. The reason for using the priority inheritance protocol or shadow task to control the priority is as follows.

Additional tasks should initially have the lowest priority. That way, it doesn't interfere with other tasks, that is, the basic tasks. However, when execution starts for the security enhancement check, it should be performed by raising the priority of the related task, not the low priority. For this, a priority inheritance protocol is used to control the priority of tasks. Furthermore, as a method that can be used for priority control instead of the priority inheritance protocol, a shadow task having the same priority as the associated task may be used.

7 is a diagram illustrating a task execution process according to the application of a security enhancement technology in a real-time device as an embodiment of the present invention. In this case, Task 0 is an additional task, and Task 1, Task 2, and Task 3 are basic tasks.

As shown in Figure 7, the embodiment of the present invention can be modeled as if each task three of the _{T i (E i, P i} , D i) when the n number of tasks in real time device operations. In this case, E _i , P _i , and D _i can be said to be the execution time, period, and deadline of the i-th task, T _{i , respectively.} And, in the embodiment of the present invention, it can be assumed that all tasks are periodic, the period and the deadline are the same (ie, P _i , = D _i ), and it can be assumed that the task with a small period has a higher priority. . This is based on the assumption that many real-time devices, such as automobiles or smart factories, satisfy this assumption, but the present invention can be easily extended to environments in which cycles and deadlines are not the same or where aperiodic tasks exist.

In more detail, each task may request the application of enhanced security to the additional task (Task 0) before performing the task according to its own cycle. This can be requested by the scheduler or advertised using a semaphore. Then, the additional task (Task 0) may apply the security enhancement technology to the task to be newly performed. For example, by calculating a hash with MD5, it is possible to check the integrity of a task or perform encryption/decryption of data to be processed.

When the security enhancement application is completed, the corresponding task can be actually performed. In this case, it may have an advantage that security can be strengthened without the need to modify basic tasks. In addition, since only the additional task (Task 0) needs to be changed, it may have the advantage of being able to easily apply and verify various security enhancement techniques.

However, such a security enhancement application may cause a priority inversion problem. In other words, since the priority of the additional task (Task 0) is high, a priority inversion problem may occur during execution of other tasks, that is, basic tasks. In this case, lower the priority of the additional task (Task 0), which is a security enhancement task, and use the priority inheritance protocol, or create a shadow task that enhances security for each task. method can be used.

In the embodiment of the present invention, in order to determine whether the real-time constraint is satisfied, it is determined whether each task _{satisfies the execution time (E i} , ) to be secured at the time of the least common multiple (LCM) of all task periods. can be judged on the basis of

In the embodiment of Figure 7, the cycles of Task 1, Task 2, and Task 3 are 5, 10, and 20, respectively, and their LCM can be said to be 20. Thus, it is possible to check that each task T _i to point 20 with the following equation (1).

<Equation 1>

Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )

(T _i : the i-th task, LCM: a time point corresponding to the least common multiple of the cycles of the basic task, P _i : the cycle of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test)

For example, if Task 3 is _{scheduled for more than 20 periods of E 3} + S ₃ , it can be said that the time constraint is satisfied. Task 2 also satisfies the time constraint if it is scheduled for more than (20/10) * (E ₂ + S _{2 ) period.}

If the sum of the remaining times by avoiding the times of the least common multiple is greater than the sum of the times that the additional task (Task 0) can perform (time constraint is satisfied O), it can be said that the task can be performed.

If the sum of the remaining times by avoiding the times of the least common multiple is not greater than the sum of the times that the additional task (Task 0) can perform (time constraint satisfaction X), this imposes a real-time constraint that is more important than security enhancement. Since it is not satisfied, it can be determined that it is not possible to strengthen the security by this much in the current task set. In this case, alternatives such as reducing the number of basic tasks or changing the cycle of the basic tasks may be required.

That is, in order to perform a separate task (additional task Task 0) for security enhancement, at least scheduling that satisfies Equation 1 must be performed.

8 is a diagram illustrating a schedulability verification result of a security enhancement technique in a real-time device as an embodiment of the present invention.

As shown in FIG. 8 , the schedulability verification of the security enhancement technology in the real-time device as an embodiment of the present invention can be said to be verified in an environment in which a real-time operating system is installed on an actual embedded board. At this time, with the board's T _i TMS320C28335 board (150MHz C28x CPU, 68KB RAM, 512KB Flash), real-time operating system used is an uC / OS2. In this verification experiment, a workload with three basic tasks was configured, and the period of each basic task was set to 10, 20, and 40. And when the security reinforcement technology is introduced by changing the execution time of each basic task, it was checked whether the scheduling possibility was satisfied, and if so, to what extent security reinforcement is possible.

The security enhancement technology used in this verification experiment is the MD5 algorithm, which can check whether the memory image of the basic task maintains integrity or has been tampered with.

As a result, as shown in FIG. 8 , when the execution time of each basic task is set to (5, 5, 9), it can be confirmed that the real-time constraint is violated when security enhancement is introduced. As the execution time decreases, it can be seen that the size of the memory that can be inspected increases to enhance security.

In this verification experiment, integrity check with MD5 was applied as a security enhancement technology, but in order to ensure data confidentiality, a technology such as LEA (Lightweight Encryption Algorithm) can be applied and scheduling possibility can be analyzed.

Through this, the present invention can enhance security while satisfying the requirements of a real-time control system (real-time device) as it is. In addition, it can be applied to the actual system without static analysis, and the schedulability can be verified while modifying the security analysis function.

The present invention can be applied and utilized in fields using real-time devices, such as an autonomous vehicle, an unmanned factory automation system, an adaptive power plant, and a CPS (Cyber Physical System).

Although described and illustrated in connection with a preferred embodiment for illustrating the technical idea of the present invention above, the present invention is not limited to the configuration and operation as shown and described as such, and deviates from the scope of the technical idea. It will be apparent to those skilled in the art that many changes and modifications can be made to the invention without reference to the invention. Accordingly, all such suitable changes and modifications are to be considered as falling within the scope of the present invention.

100: basic task assignment unit 200: additional task assignment unit
300: task execution unit 400: deadline determination unit
500: priority reversal point detection unit 600: priority control unit

Claims (10)

a basic task allocator for allocating at least one or more basic tasks for which a deadline is determined to the processor;
an additional task allocator for allocating, to the processor, an additional task having the highest priority compared to each of the assigned basic tasks and applying a security enhancement technology to the processor to be performed before the execution of each of the basic tasks;
a task performing unit for performing a task according to the assigned priority of the basic task and the additional task; and
In a real-time device comprising a; schedulability verification device of security enhancement technology. The method of claim 1,
a priority reversal time detection unit for detecting in real time a time point at which the priority is reversed from the process in which the task is performed; and
The schedulability verification apparatus of a security enhancement technique in a real-time device further comprising a; a priority control unit for controlling the priority of the basic task when the detected priority is reversed. According to claim 1, wherein the deadline determining unit,
A schedulability verification apparatus of a security enhancement technology in a real-time device that determines whether the deadline of the basic task is satisfied according to a determination expression of whether the deadline of the task is satisfied by the following equation (1).
<Equation 1>
Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )
(T _i : the i-th task, LCM: a time point corresponding to the least common multiple of the cycles of the basic task, P _i : the cycle of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test) The method of claim 1, wherein the additional task comprises:
A device for verifying the schedulability of a security enhancement technology in a real-time device to which the security enhancement technology is applied by request from a scheduler or by using a semaphore. The method of claim 2, wherein the priority control unit,
lower the priority of the additional task and then use a priority inheritance protocol to control the priority of the basic task and the additional task;
A schedulability verification apparatus of a security enhancement technique in a real-time device for controlling the priority of the basic task and the additional task by performing security enhancement for each basic task and the additional task using a shadow task. a basic task assignment step of allocating at least one or more basic tasks for which a deadline is determined to a processor in the basic task assignment unit;
an additional task allocating step of allocating, in the additional task allocator, an additional task having the highest priority compared to each of the assigned basic tasks, and to which a security enhancement technology is applied, to the processor to be performed before each basic task is performed;
a task performing step of performing a task in the task performing unit according to the assigned priority of the basic task and each additional task; and
A deadline determining step of calculating in real time a time point corresponding to the least common multiple of the periods of the basic task from the process in which the task is performed in the deadline determining unit, and determining whether the deadline of the basic task is satisfied based on this; A method of verifying the schedulability of a security enhancement technology in a real-time device, including 7. The method of claim 6,
Priority reversal time detection step of detecting in real time the time when the priority is reversed from the process of performing the task in the priority reversal time detection unit; and
The schedulability verification method of a security enhancement technology in a real-time device further comprising; a priority control step of controlling the priority of the basic task at a time when the detected priority is reversed by the priority control unit. The method of claim 6, wherein the step of determining the deadline comprises:
A schedulability verification method of a security enhancement technology in a real-time device for determining whether the deadline of the basic task is satisfied according to a determination expression of whether a deadline of the task is satisfied expressed by Equation 1 below.
<Equation 1>
Total scheduled time of T _i >= (LCM / P _i ) * (E _i + S _i )
(T _i : the i-th task, LCM: a time point corresponding to the least common multiple of the cycles of the basic task, P _i : the cycle of the i-th task, E _i : the execution time of the i-th task (Execution time), S _i : security time to perform a sexual enhancement test) The method of claim 6, wherein the additional task comprises:
A method of verifying the schedulability of a security enhancement technology in a real-time device to which the security enhancement technology is applied by requesting from a scheduler or using a semaphore. The method of claim 7, wherein the priority control step comprises:
lower the priority of the additional task and then use a priority inheritance protocol to control the priority of the basic task and the additional task;
A method of verifying schedulability of a security enhancement technique in a real-time device for controlling the priority of the basic task and the additional task by performing security enhancement for each basic task and the additional task using a shadow task.

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