WO2023286908A1

WO2023286908A1 - Method and apparatus for modulating bit, and method and apparatus for representing message

Info

Publication number: WO2023286908A1
Application number: PCT/KR2021/011137
Authority: WO
Inventors: 우사무엘
Original assignee: 단국대학교 산학협력단
Priority date: 2021-07-16
Filing date: 2021-08-20
Publication date: 2023-01-19

Abstract

Disclosed are a method and an apparatus for modulating a bit, and a method and an apparatus for representing a message. According to one embodiment of the present invention, provided is a method for modulating a bit in a communication network that performs communication by using a voltage difference between wires constituting a communication bus, the method comprising the steps of: identifying at least one bit transmitted by at least one node coupled to the communication bus; and representing a modulated bit for the identified bit on the communication bus, on the basis of a switching operation of a switching unit that turns on or off the connection between the wires. According to another embodiment of the present invention, provided is a method for representing a message in a communication network that performs communication by using a voltage difference between wires constituting a communication bus, the method comprising the steps of: acquiring one or more message candidates usable in the communication network; and representing at least one target message from among the message candidates on the communication bus, on the basis of a switching operation of a switching unit that turns on or off the connection between the wires.

Description

Method and device for modulating bits and method and device for representing messages

The present invention relates to a method and apparatus for modulating bits and a method and apparatus for representing a message. More particularly, the present invention relates to a method and apparatus capable of modulating a recessive bit into a dominant bit as well as a dominant bit into a recessive bit, and to a method and apparatus expressing a desired message through such modulation.

The convergence of automobiles and ICT (information and communication technologies) has become a new paradigm for next-generation automobile development. For example, various types of advanced driving assist systems (ADAS) are installed in recent automobiles for driver safety and convenience.

However, as the number of electronic/electrical systems installed in automobiles increases, various cyber attacks that occurred in the existing ICT environment are being transferred to the automobile environment.

As an example of a cyber attack transferred to a vehicle environment, a data frame injection attack in which a malicious data frame is injected into a vehicle's communication network may be mentioned. A data frame injection attack may perform a data frame replay attack, an impersonation attack, a DoS attack that consumes network resources, and the like.

Another example of a cyber attack that has migrated to the automotive environment is an attack that injects a dominant bit into the vehicle's communication network. An attack that injects dominant bits can perform a DoS attack that paralyzes the function of the ECU mounted in a vehicle, or a DoS attack that infiltrates the mediation process and interferes with communication between ECUs.

Meanwhile, a system for protecting a communication network of a vehicle from various attacks as described above is also being studied. A system for protecting the vehicle's communication network can be divided into an attack detection system (intrusion detection system, IDS) and a vehicle's communication network protection system from detected attacks (intrusion prevention system, IPS).

The IDS can determine whether a specific message corresponds to an attack message through a method of comparing the transmission schedule of messages used in the communication network with that of a specific message, and a method of comparing a pre-stored ID with a specific message ID. there is.

The IPS can defend the communication network through a method of generating an error frame and broadcasting it to the communication network, a method of separating a node that sent an attack message from the communication network, a method of changing the impedance level of nodes, and the like. In addition, IPS can defend communication networks by modulating bits in attack messages.

In relation to a defense method of modulating bits in an attack message, in the case of a communication network (target communication network) that performs communication using a voltage difference between wires constituting a communication bus, such as CAN (controller area network), wired AND configuration properties apply.

Therefore, when a defense method of modulating bits in an attack message is applied in a target communication network, only a method of modulating recessive bits in an attack message into dominant bits is possible, and a method of modulating dominant bits in an attack message into recessive bits is performed. Can't. Ultimately, due to these characteristics, there is a limitation in that the communication network can be defended against various attacks only within a limited range.

An object of one embodiment of the present invention is to provide a modulation method and apparatus capable of modulating a dominant bit into a recessive bit as well as modulating a recessive bit into a dominant bit.

Another object of the present invention is to provide a method and apparatus for expressing a message based on a method capable of modulating a recessive bit into a dominant bit and modulating a dominant bit into a recessive bit.

According to an embodiment of the present invention, a method for modulating a bit in a communication network that performs communication using a voltage difference between wires constituting a communication bus, wherein one or more nodes connected to the communication bus transmit checking the bit; and expressing a modulation bit for the checked bit on the communication bus based on a switching operation of a switching unit for turning on or off the connection between the wires. is provided.

According to another embodiment of the present invention, a device connected to a communication network that performs communication using a voltage difference between wires constituting a communication bus and modulates bits, wherein the connection between the wires is turned on Or a transceiver including a switching unit to be turned off; and a control unit that checks one or more bits transmitted by one or more nodes connected to the communication bus, wherein the control unit controls the transceiver so that modulation bits for the checked bits are expressed on the communication bus. A device is provided.

According to another embodiment of the present invention, as a method of expressing a message in a communication network that performs communication using a voltage difference between wires constituting a communication bus, one that can be used in the communication network obtaining the above message candidates; and presenting one or more target messages from among the message candidates to the communication bus based on a switching operation of a switching unit for turning on or off the connection between the wires. is provided.

According to another embodiment of the present invention, a device that expresses a message to a communication network that performs communication using a voltage difference between wires constituting a communication bus, which can be used in the communication network. an acquisition unit that obtains the above message candidates; a transceiver including a switching unit for turning on or off the connection between the wires; and a control unit controlling a switching operation of the switching unit so that one or more target messages from among the message candidates are expressed on the communication bus.

According to an embodiment of the present invention, since a recessive bit can be modulated into a dominant bit and a dominant bit can be modulated into a recessive bit, a defense method capable of adaptively responding to various attacks can be presented.

Effects obtainable in the present disclosure are not limited to the effects mentioned above, and other effects not mentioned may be clearly understood by those skilled in the art from the description below. will be.

1 is a diagram for explaining the overall structure of CAN.

2 is a diagram for explaining the structure of an ECU corresponding to a CAN node.

3 is a diagram for explaining a CAN transceiver.

4 is a diagram for explaining a data frame used for CAN.

5 is a diagram for explaining a CAN mediation process.

6 is a diagram for explaining a method of expressing bits in CAN.

7A is a block diagram of a device for modulating bits according to an embodiment of the present invention.

7b and 7c are views for explaining various embodiments of a transceiver.

8A to 9B are flowcharts for explaining various embodiments of the present invention.

10 is a block diagram of a device for presenting a message according to another embodiment of the present invention.

11A and 11B are flowcharts for explaining various other embodiments of a method of expressing a message.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

The terms used in the present invention are general terms that are currently widely used as much as possible while considering the functions in the present invention, but they may vary according to the intention of a person skilled in the art, case law, or the emergence of new technologies. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

When it is said that a certain part "includes" a certain component throughout the specification, it means that it may further include other components without excluding other components unless otherwise stated. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. . In addition, when a part is said to be "connected" to another part throughout the specification, this includes not only the case of being "directly connected" but also the case of being connected "through another element therebetween".

The method of modulating bits proposed through this specification (hereinafter referred to as 'modulation method') can be applied to a communication network (target communication network) that performs communication using a voltage difference between wires constituting a communication bus.

The target communication network may include a controller area network (CAN) applied to industrial automation equipment, medical equipment, automobiles, and the like. Hereinafter, the present invention will be described with a focus on CAN, and among them, the present invention will be described with a focus on CAN applied to automobiles.

In this specification, terms related to the target communication network will be replaced with terms related to CAN as follows.

Communication Bus: CAN Bus

Wires: CAN_H (CAN high) and CAN_L (CAN low)

Communication Network: CAN

CAN is a multi-master serial bus protocol based on sender identification (ID). CAN has been established as an ISO international standard and is most often used in constructing in-vehicle communication networks.

CAN is a communication protocol composed of only a physical layer and a data link layer of the OSI model. The physical layer is divided into High Speed CAN and Low Speed CAN according to communication speed, and in this specification, the present invention will be described based on High Speed CAN.

The overall structure of CAN is shown in FIG. As shown in FIG. 1, a CAN bus (CAN BUS) may be composed of two communication lines and resistors connected to both ends of the two communication lines. The two communication lines may be divided into CAN_H and CAN_L, and one or more electronic control units (ECUs) constituting a node may be connected to CAN_H and CAN_L, respectively.

As shown in FIG. 2 , ECUs connected to the CAN bus may include a microcontroller, a CAN controller, and a CAN transceiver.

CAN controllers can perform tasks that occur at the data link layer. Specifically, the CAN controller may determine whether the message (received message) transmitted from the CAN transceiver is valid data, and then, if the data is valid, it may be transmitted to the microcontroller. In addition, the CAN controller may transmit a message (transmission message) to be transmitted by the microcontroller to the CAN transceiver.

CAN transceivers may perform tasks related to the physical layer. Specifically, the CAN transceiver may convert a transmit/receive message transmitted from a CAN bus or microcontroller into an electrical signal. That is, the CAN transceiver may convert data transferred from the microcontroller into CAN communication data, and convert CAN communication data transferred from the CAN bus into data for reception by the microcontroller.

An example of a CAN transceiver is shown in FIG. 3 . A CAN transceiver may represent bits on a CAN bus and may sample bits from the CAN bus. Here, expressing bits may mean transmitting bits, and extracting bits may mean receiving bits.

The CAN transceiver can transmit bits to the CAN bus using the TX-driver (Driver) and switching elements, and can receive bits using the Receiver. When data is transmitted from a microcontroller, a data frame can be generated by the CAN controller and transmitted bit by bit to the CAN transceiver.

When a dominant bit (bit '0') is expressed on the CAN bus, the CAN controller inputs '0' to the TX driver of the CAN transceiver, and the TX driver outputs '1' in response. At this time, as two switches included in the CAN transceiver are turned on, V _DD and V _SS are output. Accordingly, as shown in FIG. 6 , a voltage of 3.5 [V] is applied to CAN_H and a voltage of 1.5 [V] is applied to CAN_L. As a result, a voltage difference of 2 [V] occurs between CAN_H and CAN_L, and the dominant bit is expressed on the CAN bus.

When a recessive bit (bit '1') is expressed on the CAN bus, the CAN controller inputs '1' to the TX driver of the CAN transceiver, and the TX driver outputs 0 in response. At this time, as two switches included in the CAN transceiver are turned off, a voltage difference of 0 [V] occurs between CAN_H and CAN_L as shown in FIG. 6, and thus a recessive bit is expressed on the CAN bus.

CAN can perform communication using various messages such as data frame, remote frame, error frame, overload frame, and the like. An example of a data frame used for CAN is shown in FIG. 4 .

A data frame includes a start of frame (SOF), an arbitration field, a control field, a data field, a cyclic redundancy check field (CRC field), an acknowledgment field (ACK field), and an end EOF (EOF) field. of frame) and INT (intermission) fields.

SOF consists of one dominant bit, indicates the beginning of a message, and is used for node synchronization.

The mediation field is used to mediate collisions between messages when messages are transmitted simultaneously from two or more nodes. As shown in FIG. 4, the arbitration field is composed of an identifier (ID) having a size of 11 bits or 29 bits and a remote transmission request (RTR) bit having a size of 1 bit. The value of the RTR bit is used to determine whether the corresponding frame is a data frame (bit value 0) or a remote frame (bit value 1).

The control field includes an identifier extension (IDE) bit and a data length code (DLC) bit. The IDE bit is used to distinguish a standard frame from an extended frame, and the DLC bit is used to indicate the number of bytes in a data field.

The data field is used to transfer information from one node to another, and may include data of 0 bytes to 8 bytes.

The CRC field is used to check whether there is an error in the message, and is composed of a CRC sequence generated using a bit string from the SOF to the data field and a CRC delimiter (DEL). All CAN controllers that correctly receive the message set the ACK bit value to '0' and transmit it. The node that sent the message checks whether there is an ACK bit, and if the ACK bit is not found, transmission is retried.

EOF consists of 7 recessive bits and is used to signal the end of a message. The INT field consists of 3 recessive bits and indicates idle time until the next arbitration process.

An example for explaining the arbitration process of CAN is shown in FIG. 5 . When a plurality of nodes simultaneously transmit messages, an arbitration process is performed, and through the arbitration process, a node with the highest priority transmits a message first.

The arbitration process is performed based on the wired AND configuration characteristics of CAN. For example, it is assumed that node 1 (ECU 1) and node 2 (ECU 2) want to transmit a message at the same time, node 1's ID is '10011111111' and ECU 2's ID is '11011111111'. After SOF, node 1 and node 2 transmit the ID in 1-bit unit to the CAN bus. When transmitting the second bit in the ID, node 1 outputs a recessive bit and node 2 outputs a dominant bit, so only the dominant bit output by node 2 is expressed on the CAN bus due to the wired AND configuration feature. At this time, node 2 switches to receiving mode.

Methods proposed through this specification can be largely classified into perfect bit modification (PBM), target id attack (TIA), and bus possession attack (BPA).

The 'attack' of TIA and BPA proposed through this specification may mean neutralizing a corresponding attack by modulating one or more bits in an attack frame or expressing a message. TIA can be understood as TIM (target id modification) as it modulates one or more bits in a specific attack frame, BPA can be understood as BPM (bus possession modification) as it expresses the modulated message exclusively on the CAN bus .

실시예 1 - PBMExample 1 - PBM

PBM is a method capable of modulating dominant bits in a message into recessive bits, and can implement wired OR configuration characteristics as well as wired AND configuration characteristics.

PBM can selectively apply wired AND configuration characteristics and wired OR configuration characteristics according to whether a bit to be modulated corresponds to a dominant bit or a recessive bit. For example, in PBM, when the bit to be modulated is a recessive bit, the wired AND configuration characteristic is applied to modulate the recessive bit into the dominant bit, and when the bit to be modulated is the dominant bit, the wired OR configuration characteristic is applied to the dominant bit. can be modulated with recessive bits.

As such, the feature of the PBM that can selectively apply the wired AND configuration characteristics and the wired OR configuration characteristics can be implemented by a switching operation of a switching unit located in a device implementing the PBM.

A block diagram of a device 700 for modulating a bit according to the first embodiment (hereinafter referred to as a 'modulation device') is shown in FIG. 7A, and a flowchart for a method for modulating a bit based on the first embodiment is shown in FIG. and Figure 8b.

As shown in FIG. 7A, the modulation device 700 may include a transceiver 710 and a control unit 720, and the transceiver 710 includes a transceiver unit 712 and a switching unit 714. It can be.

The switching unit 714 is connected to both CAN_H and CAN_L, and can turn on or off the connection between CAN_H and CAN_L. Here, 'on' may mean shorting between CAN_H and CAN_L, and 'off' may mean opening between CAN_H and CAN_L.

The transceiver 710 is 1) implemented in a form in which one transceiver unit 712 and one switching unit 714 are combined ( FIG. 7B ), or 2) two

transceiver units

716 and 718 and one switching unit. (714) may be implemented in a combined form.

In the case of 1), data in the form of a square wave generated by a controller (not shown) located at the front end may be used as an input. In the case of 2), a bit generated by a transceiver (not shown) located at the front end may be used as an input value.

In this configured state, the control unit 720 can check one or more bits transmitted by the node connected to the CAN bus (S810).

If the bit is confirmed, the control unit 720 can control the transceiver 710. That is, the controller 720 may control the transceiver unit 712 and the switching unit 714 (switching operation of the switching unit). Through the control of the control unit 720 (based on the switching operation of the switching unit), a modulated bit for the checked bit (bit modulated on the checked bit) can be expressed on the CAN bus (S812).

As described above, the PBM can selectively apply wired AND configuration characteristics and wired OR configuration characteristics depending on whether the bit to be modulated corresponds to a dominant bit or a recessive bit. same.

When the checked bit is the dominant bit (S822), the control unit 720 may turn on the switching unit 714 (S824). Through this, since CAN_H and CAN_L are shorted and the voltage difference between CAN_H and CAN_L becomes 0 [V], a recessive bit, which is a modulation bit for a dominant bit, can be expressed on the CAN bus (S824). That is, when a dominant bit is modulated into a recessive bit, a wired OR configuration characteristic may be applied.

In contrast, when the checked bit is a recessive bit (S822), the control unit 720 may turn off the switching unit 714 (S826). Also, since the control unit 720 inputs '0' to the transceiver unit 710, the transceiver unit 710 may transmit the dominant bit to the CAN bus. Through this, since CAN_H and CAN_L are opened and the voltage difference between CAN_H and CAN_L becomes 2 [V], the dominant bit, which is a modulation bit for the recessive bit, can be expressed on the CAN bus (S828). That is, when modulating recessive bits into dominant bits, wired AND configuration characteristics may be applied.

In this way, the present invention can modulate recessive bits into dominant bits as well as modulate dominant bits into recessive bits. Therefore, the present invention can adaptively respond to both an attack of modulating a recessive bit into a dominant bit and an attack of modulating a dominant bit into a recessive bit.

실시예 2 - TIAExample 2 - TIA

TIA is a method capable of modulating only messages using a specific ID, and is based on the PBM described above. Here, a message using a specific ID may correspond to an attack message transmitted by an attack node to the CAN bus for attack. Therefore, TIA is a method of neutralizing the attack by selectively modulating only the attack message transmitted by the attacking node through the CAN bus.

As shown in FIG. 9A , when TIA is applied, the controller 720 may monitor bits transmitted through the CAN bus and detect a predetermined target message among one or more messages transmitted through the CAN bus (S910). .

For example, the controller 720 may detect a target message by monitoring an arbitration field of messages transmitted through a CAN bus. A predetermined target message may correspond to an attack message, and a node transmitting the target message may correspond to an attack node. Hereinafter, in order to distinguish it from the target message (second target message) mentioned in Example 3, the target message mentioned in Example 2 will be referred to as a first target message.

When the first target message is detected, a process of modulating bits may be performed based on the PBM method described above.

First, the controller 720 can check one or more bits in the first target message (S912). If the bit is confirmed, the control unit 720 can control the transceiver 710. That is, the controller 720 may control the transceiver unit 712 and the switching unit 714 . Through the control of the controller 720, the modulation bits for the checked bits may be expressed on the CAN bus (S812).

Specifically, when the checked bit is the dominant bit (S822), the controller 720 may turn on the switching unit 714 (S824). Through this, since CAN_H and CAN_L are shorted and the voltage difference between CAN_H and CAN_L becomes 0 [V], a recessive bit, which is a modulation bit for a dominant bit, can be expressed on the CAN bus (S824).

In contrast, when the checked bit is a recessive bit (S822), the control unit 720 may turn off the switching unit 714 (S826). Also, since the control unit 720 inputs '0' to the transceiver unit 710, the transceiver unit 710 may transmit the dominant bit to the CAN bus. Through this, since CAN_H and CAN_L are opened and the voltage difference between CAN_H and CAN_L becomes 2 [V], the dominant bit, which is a modulation bit for the recessive bit, can be expressed on the CAN bus (S828).

Meanwhile, messages transmitted by various nodes are sequentially expressed on the CAN bus. Therefore, in order to accurately detect the first target message among them, it is necessary to accurately detect the mediation process in which the ID of the message is expressed.

If the first target message is detected by comparing a predetermined ID bit with all bits represented on the CAN bus, a lot of power may be consumed in detecting the first target message. Therefore, there is also a need to reduce power consumption by comparing only bits represented on the CAN bus with predetermined ID bits during the arbitration process.

To satisfy this need, the control unit 720 may be configured to detect an arbitration process and detect the first target message only with bits represented on the CAN bus during the detected arbitration process.

First, the control unit 720 may detect the timing of the mediation process by monitoring the bits transmitted through the CAN bus (S920). For example, the control unit 720 may detect a time point when one dominant bit is expressed on the CAN bus as the time point of the mediation process after the recessive bit is continuously expressed on the CAN bus a preset number of times or more (S922).

A recessive bit presented on the CAN bus consecutively more than a preset number of times may include EOF and INT fields in previous messages. Accordingly, the preset number of consecutively expressed recessive bits may be 10 or more. One dominant bit represented on the CAN bus may correspond to SOF in the current message.

Therefore, if one dominant bit is presented on the CAN bus after the recessive bit is consecutively presented on the CAN bus more than a preset number of times, the bits subsequently expressed on the CAN bus may be bits of an arbitration field in the current message.

When the timing of the arbitration process is detected, the controller 720 may detect the first target message by monitoring bits transmitted to the CAN bus during the arbitration process (S924).

실시예 3 - BPAExample 3 - BPA

BPA is a method of presenting a modulated message on a CAN bus for a desired period of time, and is based on the PBM described above. Also, the BPA can occupy transmit rights on the CAN bus for a desired amount of time.

An example of a device (hereinafter referred to as 'expressing device') 1000 expressing a message according to BPA is shown in FIG. 10 . The expression device 1000 may include an acquisition unit 1010, a transceiver 1020, and a control unit 1030, and the transceiver 1020 may include a transceiver unit 1022 and a switching unit 1024. can

The transceiver 1020 may correspond to the transceiver 710 represented in FIG. 7A in its function, and the control unit 1030 may also correspond to the controller 720 represented in FIG. 7A in its function. Therefore, the expression device 1000 may be configured to further include an acquisition unit 1010 in the modulation device 700 .

The acquisition unit 1010 may obtain one or more messages (message candidates) usable for CAN (S1110). Message candidates may include one or more of 1) first message candidates, 2) second message candidates, and 3) third message candidates.

The first message candidate may correspond to a message transmitted to the CAN bus by nodes connected to the CAN bus. The second message candidate may correspond to a message obtained by modulating one or more bits in the first message candidate. The third message candidate may correspond to a message for inducing nodes connected to the CAN bus to enter a safe mode.

The acquisition unit 1010 may acquire the first message candidate by receiving and storing messages transmitted through the CAN bus by nodes connected to the CAN bus. Also, the acquisition unit 1010 may acquire the second message candidate by modulating and storing one or more bits in the first message candidate. Furthermore, the acquisition unit 1010 may obtain a third message candidate by newly generating a message for inducing entry into the safe mode or by receiving and storing an input message from the outside.

When message candidates are obtained, processes of expressing one or more messages (target messages) from among the message candidates on the CAN bus may be performed. Processes for presenting target messages on the CAN bus may be performed based on PBM. Hereinafter, in order to distinguish it from the target message (first target message) mentioned in Example 2, the target message mentioned in Example 3 will be referred to as a second target message.

First, the controller 1030 may control the transceiver 1020 so that the second target message is expressed on the CAN bus. That is, the control unit 1030 can control the transceiver unit 1022 and the switching unit 1024, and the bits in the second target message can be expressed on the CAN bus through such control by the control unit 1030 (S1112). .

Specifically, when the bit in the second target message is a recessive bit (S1122), the controller 1030 can turn on the switching unit 1024 (S1124). Through this, since CAN_H and CAN_L are shorted and the voltage difference between CAN_H and CAN_L becomes 0[V], a recessive bit can be expressed on the CAN bus (S1124).

In contrast, when the bit in the second target message is a recessive bit (S1122), the control unit 1030 may turn off the switching unit 1024 (S1126). Also, since the control unit 1030 inputs '0' to the transceiver unit 1022, the transceiver unit 1022 may transmit the dominant bit to the CAN bus (S1128). Through this, since CAN_H and CAN_L are opened and the voltage difference between CAN_H and CAN_L becomes 2 [V], the dominant bit can be expressed on the CAN bus (S1128).

Through this process, the representation device 1000 may express the entire second target message on the CAN bus by expressing all bits in the second target message on the CAN bus.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above are illustrative in all respects, and should be understood as non-limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention. do.

Meanwhile, the processes shown in FIGS. 8a, 8b, 9a, 9b, 11a and 11b can be implemented as computer readable codes on a computer readable recording medium. A computer-readable recording medium includes all types of recording devices in which data that can be read by a computer system is stored. That is, the computer-readable 　recording medium may be a non-transitory medium such as ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc., and may also be a carrier wave (eg, It may further include a transitory medium such as transmission over the Internet) and a data transmission medium. In addition, the computer-readable recording medium may be distributed to computer systems connected through a network, and computer-readable codes may be stored and executed in a distributed manner.

Claims

A method of modulating bits in a communication network that performs communication using a voltage difference between wires constituting a communication bus, comprising:

checking one or more bits transmitted by one or more nodes connected to the communication bus; and

Based on a switching operation of a switching unit for turning on or off the connection between the wires, expressing a modulation bit for the checked bit on the communication bus.
According to claim 1,

The step of expressing

When the checked bit is a dominant bit, turning on the switching unit to express a recessive bit to the communication bus.
According to claim 1,

The step of expressing

turning off the switching unit when the checked bit is a recessive bit; and

and transmitting a dominant bit to the communication bus to represent the dominant bit to the communication bus.
According to claim 1,

Monitoring bits transmitted through the communication bus to detect a predetermined target message among one or more messages transmitted through the communication bus;

The checking step is

and checking one or more bits in the target message.
According to claim 4,

The detection step is

detecting the timing of an arbitration process by monitoring bits transmitted through the communication bus; and

and detecting the target message by monitoring bits transmitted to the communication bus during the arbitration process.
According to claim 5,

The step of detecting the time point of the mediation process,

and detecting a time point when one dominant bit is transmitted through the communication bus after successive transmissions of recessive bits equal to or greater than a preset number of times through the communication bus as the time point of the arbitration process.
A device connected to a communication network that performs communication using a voltage difference between wires constituting a communication bus and modulates bits, comprising:

a transceiver including a switching unit for turning on or off the connection between the wires; and

And a control unit for checking one or more bits transmitted by one or more nodes connected to the communication bus,

The control unit,

and controlling the transceiver such that a modulation bit for the identified bit is expressed on the communication bus.
According to claim 7,

The control unit,

turning on the switching unit so that a recessive bit is represented on the communication bus if the identified bit is a dominant bit.
According to claim 7,

The control unit,

turning off the switching unit when the checked bit is a recessive bit;

The transceiver,

and transmits a dominant bit to the communication bus.
According to claim 7,

The control unit,

Monitoring bits transmitted through the communication bus to detect a predetermined target message among one or more messages transmitted through the communication bus;

Apparatus characterized by verifying one or more bits in the target message.
According to claim 10,

The control unit,

By monitoring the bits transmitted to the communication bus, detecting the point of arbitration process (arbitration process),

and detecting the target message by monitoring bits transmitted through the communication bus during the arbitration process.
According to claim 11,

The control unit,

and detecting a time point when one dominant bit is transmitted through the communication bus as the time point of the mediation process after more than a predetermined number of recessive bits are continuously transmitted through the communication bus.
A method of expressing a message to a communication network that performs communication using a voltage difference between wires constituting a communication bus, comprising:

obtaining one or more message candidates usable in the communication network; and

Expressing one or more target messages from among the message candidates to the communication bus based on a switching operation of a switching unit for turning on or off the connection between the wires.
According to claim 13,

The step of expressing

characterized in that by turning on the switching unit, a recessive bit in the target message is expressed on the communication bus.
According to claim 13,

The step of expressing

turning off the switching unit when a bit in the target message is a dominant bit; and

and transmitting a dominant bit to the communication bus, thereby representing the dominant bit in the target message to the communication bus.
According to claim 13,

The message candidate,

a first message candidate transmitted to the communication bus by one or more nodes connected to the communication bus; and

and a second message candidate obtained by modulating one or more bits in the first message candidate.
According to claim 13,

The message candidate,

and a third message candidate for inducing one or more nodes connected to the communication bus to enter a safe mode.
A device expressing a message to a communication network that performs communication using a voltage difference between wires constituting a communication bus, comprising:

an acquisition unit that obtains one or more message candidates usable in the communication network;

a transceiver including a switching unit for turning on or off the connection between the wires; and

and a control unit controlling a switching operation of the switching unit so that one or more target messages from among the message candidates are expressed on the communication bus.
According to claim 18,

The control unit,

and turning on the switching unit so that a recessive bit in the target message is presented on the communication bus.
According to claim 18,

The control unit,

When a bit in the target message is a dominant bit, turning off the switching unit;

The transceiver,

and transmitting the dominant bit to the communication bus.
According to claim 18,

The message candidate,

a first message candidate transmitted to the communication bus by one or more nodes connected to the communication bus; and

and a second message candidate obtained by modulating one or more bits in the first message candidate.
According to claim 18,

The message candidate,

and a third message candidate for inducing one or more nodes connected to the communication bus to enter a safe mode.