KR101701307B1 - Method for transmitting data - Google Patents

Abstract

The data transmitting method in which a transmitting node included in a first sub-network belonging to a network system for transmitting data transmits data to a receiving node included in a second sub-network belonging to the network system, comprises: a step in which the transmitting node transmits, to a gateway node, a first cipher text which is a message encrypted by using a first group key that is a group key of the first sub-network; a step in which the gateway node changes the first cipher text into a second cipher text which is encrypted by using a second group key that is a group key of the second sub-network; and a step in which the gateway node transmits the second cipher text to the receiving node.

Description

[0001] METHOD FOR TRANSMITTING DATA [0002]

An embodiment according to the concept of the present invention relates to a method of transmitting data in a vehicular network system, in which data transmitted between nodes included in different subnetworks are transmitted without being decoded by a gateway node It is about how you can do it.

Recently, automobiles have been equipped with various electronic control devices, which is called a fusion of automobile industry and IT industry. Such an electronic control unit is referred to as an electronic control unit (ECU). The ECU can be a small computer with a microprocessor. Fuel injection control of the engine by the engine control unit is one of the functions of the ECU. Almost all functions necessary for running and managing the vehicle such as the transmission, attitude control, airbag control, tire air pressure control, etc., . In other words, while the conventional vehicle internal devices are mainly composed of mechanical devices, recently, electronic devices including ECUs are predominant.

As a result, the term hacking has come to be used in the automobile industry. In 2010, a team of researchers from the University of Washington in the United States first introduced cases of controlling vehicles by sending malicious control packets to vehicle ECUs. For example, in a state where the accelerator pedal of the vehicle is not moving, the fuel injection control packet is maliciously transmitted to the ECU responsible for the engine, so that the vehicle is accelerated.

Unlike conventional hacking, which is aimed at information capture, the influence of vehicle hacking is becoming a bigger problem because it is related to driver 's life. Accordingly, various methods for preventing such vehicle hacking have been researched, and the present invention relates to a secure group key exchange technique between vehicle ECUs capable of fundamentally preventing such vehicle hacking. Cryptographic primitives such as encryption, message authentication, etc. may be applied through a securely exchanged group key.

The root cause of car hacking is that each node in the vehicle's internal network communicates without any cryptographic method applied. When each ECU transmits its own data, it can solve this problem by encrypting the data and transmitting the encrypted data.

In order to apply this encryption scheme, each ECU must securely share a secret key in advance, and can perform encryption or decryption based on the secret key.

Therefore, the present invention proposes a group key exchange protocol capable of securely exchanging the same group key among legitimate ECUs belonging to a vehicle internal network. Also, a re-encryption scheme is proposed in which a gateway ECU (gateway ECU) can change the encryption key of the ciphertext without going through the process of decrypting the ciphertext.

Korean Patent Publication No. 10-2014-0078917

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method and system for transmitting encrypted messages between nodes included in different subnetworks, in which a gateway node decrypts ciphertexts encrypted with a first encryption key, To a data transmission method that can be provided.

A method of transmitting data according to an embodiment of the present invention is a method in which a transmitting node included in a first sub network included in a network system transmits data to a receiving node included in a second sub network included in the network system Wherein the transmitting node transmits to the gateway node a first cipher text in which the message is encrypted using a first group key that is a group key of the first subnetwork, the gateway node transmits the first cipher text to the second sub- To a second cipher text encrypted with a second group key which is a group key of the network, and the gateway node transmitting the second cipher text to the receiving node.

According to the method of transmitting data according to the embodiment of the present invention, nodes included in each of a plurality of subnetworks included in a network system can share a secure group key.

In addition, according to the method of transmitting data according to the embodiment of the present invention, a message can be transmitted to a receiving node included in another subnetwork without exposing a plaintext corresponding to a cipher text to a gateway ECU.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully understand the drawings recited in the detailed description of the present invention, a detailed description of each drawing is provided.
1 shows a network system according to an embodiment of the present invention.
2 is a flowchart illustrating a data communication method in the network system shown in FIG.
FIG. 3 is a flowchart specifically illustrating the re-encryption key generation step shown in FIG.
4A to 4E are views for explaining the group key sharing step shown in FIG.

It is to be understood that the specific structural or functional description of embodiments of the present invention disclosed herein is for illustrative purposes only and is not intended to limit the scope of the inventive concept But may be embodied in many different forms and is not limited to the embodiments set forth herein.

The embodiments according to the concept of the present invention can make various changes and can take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example, without departing from the scope of the right according to the concept of the present invention, the first element may be referred to as a second element, The component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like are used to specify that there are features, numbers, steps, operations, elements, parts or combinations thereof described herein, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

Hereinafter, terms used in the present specification will be summarized below. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Terms Explanation GK _A  Group key of subnetwork A K _{AB A} Re-encryption key for changing the cipher text encrypted with the group key GK _A to the cipher text encrypted with the group key GK _B , h ()  Cryptographic hash function Z ^* _p  Finite group g  A generator of a finite group

1 shows a network system according to an embodiment of the present invention.

The network system 10, which may be a vehicular network system, may include at least one or more subnetworks. The subnetwork may be any one of a CAN (Controller Area Network), a LIN (Local Interconnect Network), a CAN FD (CAN with Flexible Data Rate), and a Flexlay network. Only the second subnetwork B and the third subnetwork C are shown, but the present invention is not limited to the number of subnetworks included in the network system 10.

The first subnetwork (Network A) may be a CAN, the second subnetwork (Network B) may be a Flexlay network, and the third subnetwork (Network C) may be a CAN FD.

Each subnetwork includes a plurality of nodes, and communication between nodes included in different subnetworks is performed through a gateway node. Specifically, the first subnetwork (Network A) includes n nodes (n is a natural number of 1 or more), the second subnetwork (Network B) includes x (x is a natural number of 1 or more) The subnetwork (Network C) may include y (y is a natural number of 1 or more) nodes.

In addition, the node herein may mean an ECU that controls each electronic device, and the gateway node may mean a gateway ECU. In addition, the ECU and the gateway ECU may be a concept including a transceiver for transmitting and receiving information, and the transceiver may be implemented separately from the ECU or the gateway ECU according to an embodiment.

2 is a flowchart illustrating a data communication method in the network system shown in FIG. Specifically, FIG. 2 illustrates a process in which a transmitting node included in a first sub-network A transmits data to a receiving node included in a second sub-network B as an example.

Referring to FIGS. 1 and 2, a plurality of nodes included in a sub network share a group key of the sub network (S100). That is, a plurality of nodes included in the first sub-network Nwtwork A share a first group key GK _A , which is a group key of the first sub-network A, A plurality of included nodes share a second group key (GK _B ) which is a group key of the second subnetwork (Network B). A detailed description of the group key sharing process will be given later. The group key shared in step S100 may mean an encryption key used in encrypting or decrypting a message.

In step S200, the gateway ECU generates a re-encryption key (S200). A detailed description of the re-encryption key generation process will be given later.

The transmitting node included in the first sub-network A encrypts the message m to be transmitted to the receiving node (S300). The transmitting node may encrypt the message m using the group key GK _A of the first subnetwork (Network A). Specifically, the cipher text (c) can be generated using the following equation (1).

In Equation (1), "r" is an arbitrary random number.

The transmitting node transmits the generated cipher text c to the gateway ECU (S400). The gateway ECU having received the cipher text c re-encrypts the cipher text c encrypted with the first group key GK _A with the cipher text c 'encrypted with the second group key GK _{B in} operation S600. That is, the gateway ECU encrypts the cipher text (c) with the group key (GK _B ) of the second subnetwork (Network B), which is a subnetwork to which the transmitting node belongs, so that the transmitting node can decrypt the cipher text Can be converted into a cipher text (c '). Re-encoding may be performed using Equation (2) below.

In step S800, the gateway ECU transmits the re-encrypted cipher text c 'to the receiving node.

In step S900, the receiving node included in the second subnetwork (Network B) can receive the cipher text c 'from the gateway ECU and decrypt the received cipher text c' to obtain the message m.

First, the receiving node extracts the ciphertext (c ') from the ciphertext c' using the second group key GK _B , more specifically, the inverse number GK _B ^{- 1} of the second group key GK _B , g ^r can be calculated.

Next, as shown in Equation (4), the receiving node can calculate the inverse of g ^r obtained through Equation (3), and use it to acquire the message (m).

FIG. 3 is a flowchart specifically illustrating the re-encryption key generation step shown in FIG.

The re-encryption key K _AB is encrypted with the group key GK _B of the second subnetwork B as the cipher text c encrypted with the group key GK _A of the first subnetwork A (C '), which may be referred to as a change key according to an embodiment.

The first representative node, which is the representative node of the first sub-network (Network A), and the second representative node, which is the representative node of the second sub-network (Network B), select random numbers (S210). That is, the first representative node may select the first random number R _A and the second representative node may select the second random number R _B. The first representative node may be a predetermined node among a plurality of nodes included in the first subnetwork (Network A), and may be the first node in the group key sharing step according to an embodiment. Also, the second representative node may be a predetermined node among a plurality of nodes included in the second sub-network (Network B), and may be the first node in the group key sharing step according to an embodiment.

)을 생성하고, 제1 계산값(

)을 게이트웨이 ECU를 경유하여 제2 대표 노드로 송신한다. 또한, 상기 제2 대표 노드는 제2 난수(R_B)를 유한 그룹의 생성원(g)에 지수승하여 제2 계산값(

)을 생성하고, 제2 계산값(

)을 게이트웨이 ECU를 경유하여 제1 대표 노드로 송신한다.In step S230, each of the first representative node and the second representative node exponentially multiplies the selected random number in the source (g) of the finite group to exchange calculated values calculated. That is, the first representative node exponentially multiplies the first random number R _{A with} the generation source g of the finite group to generate a first calculation value

), And generates a first calculation value (

To the second representative node via the gateway ECU. Also, the second representative node exponentially multiplies the second random number (R _B ) with the generation source (g) of the finite group to generate a second calculation value

), And generates a second calculated value (

To the first representative node via the gateway ECU.

)에 지수승하여 공유값(

)을 생성하고, 상기 제2 대표 노드는 제2 난수(R_B)를 상기 제1 대표 노드로부터 수신한 제1 계산값(

)에 지수승하여 공유값(

)을 생성할 수 있다.In step S250, the first representative node and the second representative node can generate the shared value h using the calculated value received from the other party and the random number selected by the first representative node and the second representative node. That is, the first representative node receives the first random number R _A from the second representative node

) To exponentiate to a shared value (

), And the second representative node generates a second calculated value (R _B ) from the first representative node

) To exponentiate to a shared value (

Can be generated.

In step S270, the first representative node and the second representative node multiply the reciprocal number of their group key by the shared value, or multiply the reciprocal of the shared value by the own group key, and generate the calculated value And transmits it to the gateway ECU. That is, the first representative node generates a third calculated value h * GK _A ^-1 or h ^-1 * GK _A using the shared value h and the first group key GK _A , 3 The calculated value can be sent to the gateway ECU. Also, the second representative node generates a fourth calculated value h ^-1 * GK _B or h * GK _B ^-1 using the eigenvalue h and the second group key GK _B , 4 The calculated value can be transmitted to the gateway ECU.

In step S290, the gateway ECU may generate the re-encryption key (GK _A ^-1 * GK _B ) using the third calculation value and the fourth calculation value received from the first representative node and the second representative node .

4A to 4E are views for explaining the group key sharing step shown in FIG. A process of sharing the first group key GK _A by the nodes included in the first subnetwork A will be described with reference to FIG.

First, each of n nodes (n is a natural number of 2 or more) included in the first subnetwork (Network A) selects its own random number. That is, the first node (ECU 1A) is a first random number, select the (r _1A), and the k-th node (ECU kA, k is a natural number greater than or equal to 1 less than n, or such) is the k-th random number (r _kA) Select.

)을 계산한다. 또한, 제1 ECU(ECU 1A)는 연산값(

)을 제2 ECU(ECU 2A)에게 송신한다.Referring to FIG. 4A, the first ECU (ECU 1A) exponentially multiplies the first random number r _1A by a generation source g of a finite group which is a public parameter,

). Further, the first ECU (ECU 1A)

To the second ECU (ECU 2A).

)에 지수승하여 연산값(

)을 생성한다. 또한, 제2 ECU(ECU 2A)는

를 제3 ECU(ECU 3A)로 송신한다.Referring to FIG. 4B, the second ECU (ECU 2A) outputs the second random number r _2A as an operation value (

) And multiplying the calculated value (

). Further, the second ECU (ECU 2A)

To the third ECU (ECU 3A).

를 제4 ECU(ECU 4A)로 송신한다.Referring to FIG. 4C, the third ECU (ECU 3A) performs an operation using the third random number r _3A and the value received from the second ECU (ECU 2A)

To the fourth ECU (ECU 4A).

를 제5 ECU(ECU 5A)로 송신한다. Referring to FIG. 4D, the fourth ECU (ECU 4A) performs an operation using the fourth random number r _4A and the value received from the third ECU (ECU 3A)

To the fifth ECU (ECU 5A).

를 수신하고, 수신된 값에 제n 난수(r_nA)를 지수승하여

를 연산한다.Since their is a node (ECU kA) receives the operation result from the previous node to select a random number (r _kA) the operation result to the index seunghan calculating a value, and the node (ECU (k + 1) A ) received from the previous node, As shown in FIG. Similarly, referring to FIG. 4E, the n-th node is connected to the (n-1)

, And the n-th random number r _nA is exponentially multiplied with the received value

.

연산하고, 연산값을 제i ECU(ECU iA)로 송신한다. 즉, 제n ECU(ECU nA)는 제1 ECU(ECU 1A)로

를 전송하고, 제2 ECU(ECU 2A)로

를 전송하고, 제3 ECU(ECU 3A)로

를 전송할 수 있다.Further, the n-th ECU (ECU nA)

And transmits the calculated value to the i-th ECU (ECU iA). That is, the n-th ECU (ECU nA) is connected to the first ECU (ECU 1A)

And transmits it to the second ECU (ECU 2A)

And transmits it to the third ECU (ECU 3A)

Can be transmitted.

)는 제1 서브 네트워크(Network A)에 포함된 모든 노드들 각각이 선택한 난수들의 곱을 유한 그룹의 생성원(g)에 지수승한 값이 될 수 있다. Each of the nodes other than the n-th node (ECU nA) can generate the group key (GK _A ) by exponentially increasing the value received from the n-th node (ECU nA). That is, the group key of the first sub-network (Network A)

May be a value obtained by multiplying the product of the random numbers selected by each of all the nodes included in the first subnetwork A by the exponentiation factor g of the finite group.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: Network system
Network A: first sub-network
Network B: Second sub-network
Network C: Third subnetwork

Claims (6)

A method for transmitting data to a receiving node included in a first sub-network included in a network system, the receiving node including a second sub-network included in the network system,
Transmitting to the gateway node a first cipher text in which the transmitting node has encrypted a message using a first group key which is a group key of the first subnetwork;
The gateway node changing the first ciphertext to a second ciphertext encrypted with a second group key that is a group key of the second subnetwork; And
The gateway node sending the second ciphertext to the recipient node,
The gateway node uses the re-encryption key to change the first ciphertext to the second ciphertext,
Wherein the re-
Selecting a first random number and a second random number by a first representative node included in the first sub network and a second representative node included in the second sub network;
Wherein the first representative node and the second representative node determine whether or not the first representative value is a first calculated value calculated by exponentially multiplying the first random number by the generation source of the finite group, Exchanging a second calculated value calculated by performing an exponential multiplication on the generation source of the finite group;
The first representative node and the second representative node calculating a product of the first random number and the second random number as a shared value which is a value obtained by multiplying the product of the generation of the finite group by the product of the first random number and the second random number;
The gateway node receiving from the first representative node a third calculated value which is a value obtained by multiplying the shared value by the reciprocal of the first group key and receiving the second group key from the second representative node in an inverse number of the shared value Receiving a fourth computed value that is a multiplied value; And
Wherein the gateway node generates the re-encryption key, which is a product of the third calculated value and the fourth calculated value,
A method for transmitting data. The method according to claim 1,
Wherein the network system is a vehicular network system,
Wherein the first subnetwork or the second subnetwork is a CAN (Controller Area Network), a CAN FD (CAN with Flexible Data Rate), a LIN (Local Interconnect Network) or a Flexlay network. The method according to claim 1,
Each of the transmitting node and the receiving node is an electronic control unit (ECU) for controlling the operation of the corresponding electronic device,
Wherein the gateway node is a gateway ECU. The method according to claim 1,
The method of transmitting data includes:
And the receiving node decrypting the second cipher text using the second group key. The method according to claim 1,
Wherein the first group key is a value obtained by multiplying a product of a random number selected by each of a plurality of nodes included in the first sub network by an exponentiation factor g of a finite group,
Wherein the second group key is a value obtained by multiplying a product of a random number selected by each of a plurality of nodes included in the second sub-
A method for transmitting data. delete

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