KR101357074B1 - Secure key establishment method using a key agreement mechanism based on PKI - Google Patents

Abstract

The present invention relates to a security key setting method using a public key-based key sharing mechanism that can efficiently set a security key for encrypted communication between a smart meter, a data collection device, and an AMI server in a smart grid environment. The two devices each generate two random values, exchange two random values generated through a public key-based encryption method, and transfer one random value among the random values of the exchanged party to the other party again. If the agreement is performed and the key agreement is made, the security key is set using the remaining random values among the random values generated by the two devices.

Description

Secure key establishment method using a key agreement mechanism based on PKI}

The present invention relates to a security key setting method in a smart grid that can efficiently set a security key for encrypted communication between a smart meter, a data collection device and an advanced metering infrastructure (AMI) server in a smart grid environment.

Due to technological advancement and economic growth, the production and supply of electric power has become the most important essential element in the world, but it still depends on fossil fuels and its efficiency is very low. The use of fossil fuels has increased awareness of environmental degradation, and the interest in smart grid technology incorporating information and communication technology into existing unidirectional power grid systems has increased, especially in advanced countries. It is becoming.

The Smart Grid is a next-generation intelligent power grid that integrates information technology (IT) with existing power grids to increase the efficiency of power supply and use by exchanging real-time information in both directions between power suppliers and consumers.

In the smart grid, all electric devices that are operated by electricity are connected to a wired and wireless network, and they are made in an organic relationship by exchanging information with each other. Existing power systems generally have more than 10% of reserve power and store it because it is impossible to predict power usage.However, in the smart grid environment, the energy usage prediction is analyzed by analyzing the energy used by the smart meter in real time. It is possible to distribute energy efficiently.

The core infrastructure of this smart grid is the advanced metering infrastructure (AMI), a remote metering system. This is a system for efficiently managing energy, as shown in FIG. 1, a smart meter 10 installed in each home and measuring device usage information and power usage of each home, and the smart meter 10. The AMI server 50 collects the device usage information and power usage amount of each home. In this case, the AMI server 50 may collect data of the plurality of smart meters 10 via a data collection unit 30. Here, the data collection device 30 communicates with a plurality of adjacent smart meters 10 through a neighbor area network (NAN), and communicates with the AMI server 50 through a wide area network (WAN).

Through this AMI, real-time energy usage information can be collected, and energy management can be used to reduce the energy costs of homes and businesses, and the overall energy usage can be managed efficiently.

AMI is a power service informatization infrastructure between end consumers and utilities, and is a smart meter-based core infrastructure system essential for smart grid operation. Unlike conventional AMR (Automated Meter Reading) which simply reads only the measured value, it is possible to remotely connect / disconnect based on two-way communication and open protocol based on smart meter and prepaid plan ( It enables the application of various plans such as prepayment, RTP, critical peak pricing, and time-of-use pricing.

While smart grid system has such various advantages, it is possible to access external network through wired / wireless wireless network, unlike existing power grid system, which has no threat to security because it is a closed structure that is inaccessible from external network. Since the smart meter can be accessed, it can be exposed to various risk factors such as hacking, malware worms, and viruses, which may cause loss of consumer's personal information and industrial system paralysis.

Therefore, in the smart grid, authentication for the AMI meter 10 is necessary for enhanced security.

The present invention is to provide a security key setting method using a public key-based key sharing mechanism that can efficiently set the security key for encryption communication between the smart meter, the data collection device and the AMI server in a smart grid environment.

As a means of solving the above problem, the present invention is a step of the first device receiving a first message from the second device, including the first, second random value generated by the second device and encrypted with the public key of the first device ; The second device includes a second message that is encrypted by the first device by the public key of the second device, including the first random value included in the received first message, the third and fourth random values generated by the first device. Transmitting to; And when the third device receives the third random value from the second device after transmitting the second message, determines that a key agreement has been made, and then generates a second random value included in the first message and a self-generated second value. A method of setting a security key using a public key-based key sharing mechanism, comprising: generating a first security key to be used for encrypted communication with a second device from a random value.

The security key setting method may further include transmitting, by the first device, its certificate to the first device according to a security key setting request from a second device before receiving the first message from the second device. It may further include.

The security key setting method further includes the step of the first device receiving a certificate of the second device together with the first message to validate the certificate of the second device, wherein the second device If the credential is valid, the second message may be transmitted to the second device.

The security key setting method may include a third message generated by a first device and a third message encrypted with a public key of the first device and including fifth and sixth random values generated by a third device. Receiving from the second device a message including a random value and encrypted with the first security key; The first device includes a fifth random value included in the third message, first and second random values included in the message received from the second device, and third and fourth random values generated by the first device; Sending a sixth message encrypted with a public key of a third device to the third device; After the first device transmits the sixth message, if a third random value is received from the third device through the second device, it is determined that a key agreement has been made, and thus the fourth random value and the third message generated by the first device. The method may further include generating a second security key to be used for encrypted communication with the third apparatus using the sixth random value included in the.

The method of setting a security key further includes the step of the first device receiving a certificate of the third device through a second device and validating the received certificate of the third device. If the certificate is valid, the sixth message may be transmitted to the third device.

In addition, the present invention is another means for solving the above-described problem, the first device includes a first message encrypted by the public key of the first device including the first, second random value generated by the second device Transmitting to; Receiving, by the second device, a second message including the third and fourth random values generated by the first device and the first random value and encrypted with the public key of the second device; Decoding, by the second device, the second message and transmitting a third random value from among the third and fourth random values included in the second message to the first device; And when the second device checks the first random value included in the second message and matches the generated first random value, it is determined that a key agreement has been made, and thus the second random value generated by the second device. And generating a first security key to be used for encrypted communication with a first device from a fourth random value included in the second message. to provide.

The security key setting method may include: receiving, by a second device, a key setting request to a first device to receive a certificate of the first device; And verifying, by the second device, the validity of the certificate of the first device, and when the certificate of the first device is valid, transmitting the first message to the first device.

The security key setting method may further include a third message including the fifth and sixth random values generated by the third device and encrypted with the public key of the first device, and the seventh random generated by the third device. Receiving a fourth message from the third device, the fourth message including a value and encrypted with the public key of the second device; Transmitting a third message included in the fourth message, a fifth message including a first random value and a second random value generated by the fourth message and encrypted with a first security key to the first device; Receiving a first random value and a third random value from the third device, and transmitting a third random value to the first device; If the received first random value coincides with the first random value generated by the self, using the seventh random value included in the fourth message and the second random value generated by the third device, Generating a third security key for the encrypted communication of may further include.

The security key setting method may include, when the key setting request is received from a third device before the second device receives the fourth message, transmits its own certificate and the certificate of the first device to the third device. The method may further include receiving a certificate of a third device together with the fourth message from the third device, and transmitting the received third device certificate together with the fifth message to the first device. .

In addition, according to another aspect of the present invention, there is provided a method for setting a security key for encrypted communication with a first device and a second device by a third device. Generate a sixth and seventh random value, generate a third message by encrypting the fifth and sixth random values with the public key of the first device, and generate the third message, identification information of the third device, and the seventh Generating a fourth message obtained by encrypting a random value with the public key of the second device and transmitting the fourth message to the second device; From the first device that has received the third message through the second device, the first and second random values generated in the second device, the third and fourth random values generated in the first device and the fifth random Receiving a sixth message containing the value and encrypted with the public key of the third device; Extracting first and third random values from the sixth message and transmitting the first and third random values to the second device; And if the fifth random value included in the sixth message and the fifth random value generated by the sixth random message are identical to each other, the second device from the second random value included in the sixth message and the seventh random value generated by the sixth random message; Generating a third security key for encrypted communication, and generating a second security key for encrypted communication with the first device from the fourth random value included in the sixth message and the sixth random value generated by the third device; It can provide a security key setting method using a public key-based key sharing mechanism, characterized in that it comprises a step.

The security key setting method may include: obtaining a certificate of a first device or a second device by requesting a key device from a third device to set a key; The method may further include verifying validity of certificates of the first and second devices, and when the certificates of the first and second devices are valid, transmitting the fourth message to the second device.

According to the present invention, in the smart grid system, using a public key-based key agreement mechanism, a smart meter installed in the customer, a data collection device for collecting data between multiple smart meters, and a security key for encrypted communication between the AMI server By setting, the security key can be set without setting the key for encryption in advance, and the confidentiality of the data and the set key transmitted for key establishment can be maintained, and the two-way authentication and key setting can be performed with a small amount of calculation. There is a possible effect.

1 is a block diagram illustrating an AMI structure of a smart grid to which the present invention is applied.
2 is a message flow diagram illustrating a security key setting procedure between a data collection device and an AMI server according to an embodiment of the present invention.
3 is a message flow diagram illustrating a security key setting procedure for a smart meter according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, detailed description of well-known functions or constructions that may obscure the subject matter of the present invention will be omitted. It should be noted that the same constituent elements are denoted by the same reference numerals as possible throughout the drawings.

In the AMI environment of the smart grid as shown in FIG. 1, in order to ensure security, the communication device, specifically, the smart meter 10 and the data collection device 30 and the AMI server 50 are transmitted upon initial authentication and key setting. Maintain the confidentiality of the data, the main data to and from the AMI server 50, including the demand response (DR) information, and meter reading information stored in the data collection device 30, each of the AMI All transmitted through the communication section (smart meter 10 and data collection device 30 section, data collection device 30 and AMI server 50 section, smart meter 10 and AMI server 50 section, etc.) Ensuring integrity of information, non-repudiation of meter reading or demand response information, and mutual authentication at initial device registration are required.

The present invention relates to maintaining the confidentiality of the data transmitted during key establishment in the smart grid, among the security requirements described above.

In the AMI implementation of the smart grid, in establishing a security key between the smart meter 10, the data collection device 30, and the AMI server 50, a public key-based key agreement mechanism is used. Specifically, through the analysis of the key agreement mechanisms proposed in ISO / IEC 11770-3, two-way authentication is possible and a key operation mechanism with a small amount of operation is selected and used. The key agreement mechanism used in the present invention is that two devices for establishing a security key each generate a random value and perform a key agreement by exchanging a random value generated through a public key structure. By using a key agreement mechanism of a key structure, a security key to be used for encryption communication between the smart meter 10, the data collection device 30, and the AMI server 50 is stably and efficiently set.

In describing the security key setting method using the public key-based key agreement mechanism according to the present invention in detail below, for convenience of understanding, two random values generated for key agreement in the data collection device 30 Denotes the first and second random values, and two random values generated by the AMI server 50 for key agreement are referred to as third and fourth random values and generated by the smart meter 50 for key agreement. The three random values are called fifth, sixth, and seventh random values.

2 and 3 are message flow diagrams illustrating a method for setting a security key according to the present invention, and show an example applied to the AMI structure shown in FIG.

According to the present invention, first, the data collection device 30 and the AMI server 50 to collect and store the data transmitted from the plurality of smart meters 10 located within a certain range, and then transmits to the AMI server 50 at a predetermined period. ) Is a security key setting, the process is described with reference to FIG.

,

)는 데이터 수집 장치(30)와 AMI 서버(50) 양측에서 모두 신뢰할 수 있는 공인된 인증 기관(CA: Certification Authority)에서 발급될 수 있으며, 상기 인증 기관을 통해서 유효성을 검증할 수 있다.First, in order to perform a public key-based key agreement procedure, the data collection device 30 and the AMI server 50 each have their own certificate for authenticating their public key.

,

) May be issued by an accredited certification authority (CA) that is trusted by both the data collection device 30 and the AMI server 50, and may be validated through the certification authority.

In addition, the security key setting between the data collection device 30 and the AMI server 50 may be started by the data collection device 30 transmitting a security key setting request to the AMI server 50 (S115). .

)를 데이터 수집 장치(30)로 전송할 수 있다(S120).In addition, the AMI server 50 that receives the security key setting request from the data collection device 30 has its own certificate (for authentication of the public key).

) May be transmitted to the data collection device 30 (S120).

)에 대한 유효성을 검증하여(S125), 상기 인증서(

)가 유효한 경우, 두 개의 랜덤값

,

(이하, 제1, 제2 랜덤값이라 함)을 생성하고, 상기 생성한 제1, 제2 랜덤값을 AMI 서버(50)의 공개키로 암호화하여 제1 메시지(

)를 생성한다(S130). 여기서, 자신을 식별할 수 있는 데이터 수집 장치(30)의 식별 정 보(

)를 상기 제1, 제2 랜덤값과 함께 암호화할 수 있다.The data collection device 30 is a certificate of the AMI server 50 received after the security key setting request (

) To validate (S125), the certificate (

) Is valid, two random values

,

(Hereinafter, referred to as first and second random values) and encrypts the generated first and second random values with the public key of the AMI server 50 to generate the first message (

) Is generated (S130). Here, the identification information of the data collection device 30 that can identify itself (

) May be encrypted together with the first and second random values.

)를 더 전송할 수 있다.The data collection device 30 transmits the generated first message to the AMI server 50 (S135). At this time, the data collection device 30 has its own certificate (with a first message)

) Can be sent further.

,

(이하, 제3, 제4 랜덤값이라 함)을 생성하고, 상기 생성한 제3, 제4 램덤값을 데이터 수집 장치(30)로 전달하기 위한 제2 메시지(

)를 생성한다(S145). 상기 제2 메시지는 자신이 생성한 제3, 제4 랜덤값을 데이터 수집 장치(30)의 공개키로 암호화하여 생성할 수 있으며, 데이터 수집 장치(30)로부터 제1, 제2 랜덤값을 수신하였음을 확인하기 위해 상기 수신한 제1 메시지에서 획득한 제1 랜덤값과, 보안 키 설정 대상을 식별하기 위한 자신, 즉, AMI 서버(50)의 식별 정보(

)가 더 포함되어 암호화될 수 있다.When the AMI server 50 receives the encrypted first message including the first and second random values generated by the data collection device 30 and the certificate of the data collection device 30, the received data collection device Validating the certificate of (30) (S140), if the certificate of the data collection device 30 is valid, two random values

,

(Hereinafter, referred to as a third and fourth random values), and a second message (for transmitting the generated third and fourth random values to the data collection device 30)

) Is generated (S145). The second message may be generated by encrypting the third and fourth random values generated by the public key of the data collection device 30, and received the first and second random values from the data collection device 30. In order to confirm the first random value obtained from the received first message and the identification information of the self, that is, the AMI server 50 for identifying a security key setting target (

) May be further included and encrypted.

The AMI server 50 transmits the generated second message to the data collection device 30 (S150).

을 AMI 서버(50)로 전송하여, 자신이 제3, 제4 랜덤값을 안전하게 수신하였음을 알린다(S155).In addition, the data collection device 30 that receives the second message transmitted from the AMI server 50 decodes the received second message with its own secret key, and then includes the first random value, the third and the fourth included in the message. After obtaining the random value, the third random value of the

It transmits to the AMI server 50, it informs that it has securely received the third, fourth random value (S155).

(이하, 제1 보안키라 함)를 도출하여 설정한다(S160, S165). 이때, 상기 제1 보안키는 특정 키 유도 함수(Key derivation function)를 통해서 도출될 수 있다.Through the above process, each of the AMI server 50 and the data collection device 30 that exchanges two random values generated by each other, and confirms that the other party has received them, respectively receive the message (the first message or Encryption communication between one of the random values (second random value or fourth random value) obtained in the second message) and one of the random values generated by itself (the fourth random value or the second random value). Common security key to use

(Hereinafter referred to as a first security key) is derived and set (S160 and S165). In this case, the first security key may be derived through a specific key derivation function.

As a result, the data collection device 30 and the AMI server 50 can set the same first security key to be used for encrypted communication with each other, and then, encrypted communication is performed using the first security key ( S170).

In the smart grid environment according to the present invention, as described above, after a security key is set between the data collection device 30 and the AMI server 50, the smart meter 10, the data collection device 30, and the smart meter 10. ) And a security key between the AMI server 50 is set. In the AMI structure of FIG. 1, the smart meter 10 is connected to the AMI server 50 through the data collection device 30, but considering the application range of various smart grids, the smart meter 10 may be used. It may also be necessary to communicate with the AMI server 50 directly. In consideration of this, the present invention enables to set a security key between the smart meter 10 and the AMI server 50. In the direct communication between the smart meter 10 and the AMI server 50, the data collection device 30 is delivered as it is without additional processing for the data.

Referring to FIG. 3, a security key setting procedure between the smart meter 10, the data collection device 30, and the AMI server 50 will be described below.

)를 저장하고 있다.The smart meter 10 installed on the user side, like the data collection device 30 and the AMI server 50, is a certificate issued through a trusted certificate authority (

) Is being saved.

When the smart meter 10 intends to communicate with the data collection device 30 and the AMI server 50, the smart meter 10 transmits a security key setting request (Req.) To the connected data communication device 30 (S175).

,

)를 상기 스마트 미터(10)로 전송한다(S180).The data collection device 30 is a certificate for public key authentication of the data collection device 30 and the AMI server 50 (

,

) Is transmitted to the smart meter 10 (S180).

,

,

(이하, 제5, 제6, 제7 랜덤값이라 함)을 생성한다(S195). 여기서 제5 랜덤값을 키 동의를 위한 랜덤값이고, 제6, 제7 랜덤값은 각각 AMI 서버(50) 및 데이터 수집 장치(30)와의 보안키 유도를 위한 랜덤값이다.The smart meter 10 verifies the validity of the certificate of the received data collection device 30 and the AMI server 50 (S190), if valid three random values

,

,

(Hereinafter referred to as fifth, sixth, and seventh random values) is generated (S195). Here, the fifth random value is a random value for key agreement, and the sixth and seventh random values are random values for deriving a security key from the AMI server 50 and the data collection device 30, respectively.

,

를 생성한다(S200). 구체적으로 설명하면, 우선 제5, 제6 랜덤값을 AMI 서버(50)의 공개키로 암호화하여 AMI 서버(50)와의 키 동의를 위한 제3 메시지를 생성한다. 더불어, 상기 스마트 미터(10)는 상기 제3 메시지에 스마트 미터(10)의 식별 정보

및 데이터 수집 장치(30)의 식별정보

를 더 포함시킬 수 있다. 이는 상기 제3 메시지를 수신하게 될 AMI 서버(50)에서 보안키 설정 대상이 데이터 수집 장치(30)에 연결된 스마트 미터(10)임을 알 수 있도록 한다. 이어서 상기 스마트 미터(10)는 상기 생성한 제3 메시지와 데이터 수집 장치(30)에 전달된 제6 랜덤값을 데이터 수집 장치(30)의 공개키로 암호화하여 제4 메시지를 생성한다. 상기 제4 메시지에는 스마트 미터(10)의 식별 정보

가 더 포함될 수 있다.The smart meter 10 uses the fifth to seventh random values to encrypt the third and fourth messages for key agreement with respect to each of the data collection device 30 and the AMI server 50.

,

To generate (S200). Specifically, first, the fifth and sixth random values are encrypted with the public key of the AMI server 50 to generate a third message for key agreement with the AMI server 50. In addition, the smart meter 10 is identification information of the smart meter 10 in the third message.

And identification information of the data collection device 30.

It may further include. This allows the AMI server 50 that will receive the third message to know that the target for setting the security key is the smart meter 10 connected to the data collection device 30. Subsequently, the smart meter 10 encrypts the generated third message and the sixth random value transmitted to the data collection device 30 with the public key of the data collection device 30 to generate a fourth message. The fourth message includes identification information of the smart meter 10.

May be further included.

를 더 전송할 수 있다.The smart meter 10 transmits the generated fourth message to the data collection device 30 (S205). At this time, the smart meter 10 is a certificate of the smart meter 10 for its own public key authentication with a fourth message

Can be further transmitted.

를 생성한다(S215). 상기 단계 S210에서 생성한 제1, 제2 랜덤값은 앞서 도 2의 단계 S130에서 데이터 수집 장치(30)와 AMI 서버(50)와의 보안 키 설정을 위해 생성한 제1, 제2 랜덤값과는 다를 수 있다.When the fourth message and the certificate of the smart meter 10 are received, the data collecting device 30 decrypts the fourth message to obtain a third message and a seventh random value included in the fourth message. After generating the first and second random values (S210), the fifth message is generated by encrypting the generated first and second random values and the third message obtained from the fourth message with the first security key set in FIG. 2.

(S215). The first and second random values generated in step S210 are different from the first and second random values generated for setting a security key between the data collection device 30 and the AMI server 50 in step S130 of FIG. 2. can be different.

The data collection device 30 transmits the generated fifth message to the AMI server 50 (S220). At this time, the received certificate of the smart meter 10 is transmitted together.

That is, the data collection device 30 passes only to the AMI server 50 without performing validation of the certificate of the smart meter 10, and validates the certificate of the smart meter 10 in the AMI server 50. Verification is done.

를 더 포함할 수 있다.When the AMI server 50 receives the fifth message together with the certificate of the smart meter 10 from the data collection device 30, the AMI server 50 verifies the validity of the received certificate of the smart meter 10 (S225), If valid, a third and fourth random values (which may be different from the third and fourth random values generated in step S145 of FIG. 2) are generated, and the received fifth message is decrypted with a first security key to generate a third random value. After acquiring the message, the first and second random values, and further decrypting the third message with its own secret key to obtain the fifth and sixth random values, the third and fourth random values generated by the user are obtained. In operation S230, the first, second, and fifth random values are encrypted with the public key of the smart meter 10 to generate a sixth message. The sixth message includes identification information of the AMI server 50.

As shown in FIG.

The AMI server 50 transmits the generated sixth message to the smart meter 10 through the data collection device 30 (S235). At this time, the data collection device 30 transmits the sixth message to the smart meter 10 as it is.

Receiving the sixth message, the smart meter 10 decrypts the sixth message with its own secret key and is included in the first message. Acquire the second, third, fourth, and fifth random values, check whether the fifth random value matches the fifth random value generated in step S195, and recognize that the key agreement has been made. In order to confirm the key agreement, the first random value and the third random value are transmitted to the data collection device 30 (S240).

The data collection device 30 checks whether the first random value among the received first and third random values matches the first random value generated in step S210, and if it matches, recognizes that the key agreement is made. In operation S245, the remaining third random value is transmitted to the AMI server 50.

Thereafter, the AMI server 50 checks whether the third random value received through the data collection device 30 matches the third random value generated in the step S230, and if it matches, recognizes that the key agreement is made. In operation S250, a second security key to be used for communication with the smart meter 10 is generated and set from the fourth random value generated by the self and the sixth random value obtained from the third message (S250).

The data collection device 30 generates and sets a third security key to be used for encryption communication with the smart meter 10 from the second random value generated by the device and the seventh random value obtained from the fourth message previously received. (S255).

Subsequently, the smart meter 10 generates a second security key for communication with the AMI server 50 and a third security key for communication with the data collection device 30 (S260). Specifically, the smart meter 10 generates a second security key from the fourth random value obtained from the sixth message and the sixth random value generated by the smart meter 10 in step S195, and obtains the second random key from the sixth message. A third security key is generated and set using the random value and the seventh random value generated in step S195.

Thereafter, the smart meter 10 and the data collection device 30 are encrypted communication using the third security key, and the encrypted communication using the second security key is performed between the smart meter 10 and the AMI server 50 ( S265, S270).

The security key setting method of the present invention described above may be implemented in software form readable by various computer means and recorded on a computer readable recording medium. Here, the recording medium may include program commands, data files, data structures, and the like, alone or in combination. Program instructions to be recorded on a recording medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. For example, the recording medium may be an optical recording medium such as a magnetic medium such as a hard disk, a floppy disk and a magnetic tape, a compact disk read only memory (CD-ROM), a digital video disk (DVD) Includes a hardware device that is specially configured to store and execute program instructions such as a magneto-optical medium such as a floppy disk and a ROM, a random access memory (RAM), a flash memory, do. Examples of program instructions may include machine language code such as those generated by a compiler, as well as high-level language code that may be executed by a computer using an interpreter or the like. Such hardware devices may be configured to operate as one or more software to perform the operations of the present invention, and vice versa.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention, and are not intended to be exhaustive or to limit the invention to the precise form disclosed. It is self-evident to those who have knowledge. Furthermore, although specific terms are used in this specification and the drawings, they are used in a generic sense only to facilitate the description of the invention and to facilitate understanding of the invention, and are not intended to limit the scope of the invention.

10: Smart Meter
30: Data Collection Unit (DCU)
50: Advanced Metering Infrastructure (AMI) server

Claims (12)

The first device receives from the second device a first message that is encrypted with the public key of the first device and includes a first random value generated for key agreement at the second device and a second random value generated for deriving a security key. Making;
Generating, by the first device, a third random value for key agreement and a fourth random value for deriving a security key;
A second message including a first random value included in the first message received by the first device, third and fourth random values generated by a key agreement of the first device, and encrypted with the public key of the second device; 2 sending to the device; And
If the first device receives a third random value from the second device after the transmission of the second message, the second device determines that a key agreement has been made, and the second random value and the self contained in the first message are determined. And generating a first security key to be used for encrypted communication with the second device from the generated fourth random value. The method of claim 1,
Before the first device receives the first message from the second device, transmitting the certificate to the first device according to a security key setting request from the second device. Security key setting method using public key based key sharing mechanism. The method of claim 1,
Receiving, by the first device, the certificate of the second device together with the first message to validate the certificate of the second device;
And if the certificate of the second device is valid, transmit the second message to the second device. The method of claim 1,
The first device includes fifth and sixth random values generated by the third device and includes a third message encrypted with the public key of the first device and the first and second random values generated by the second device; Receiving a message encrypted with a first security key from the second device;
The first device includes a fifth random value included in the third message, first and second random values included in the message received from the second device, and third and fourth random values generated by the first device; Sending a sixth message encrypted with a public key of a third device to the third device;
After the first device transmits the sixth message, if a third random value is received from the third device through the second device, it is determined that a key agreement has been made, and thus the fourth random value and the third message generated by the first device. And generating a second security key to be used for encrypted communication with the third apparatus using the sixth random value included in the public key-based key sharing mechanism. 5. The method of claim 4,
The first device further comprises receiving a certificate of the third device through a second device and validating the received third device's certificate,
And when the certificate of the third device is valid, transmit the sixth message to the third device. Generating, by the second device, a first random value for key agreement and a second random value for deriving a security key;
Transmitting to the first device a first message including the first and second random values generated by the second device and encrypted with the public key of the first device;
A second random value generated by the second device for key agreement in the first device, a fourth random value generated for deriving a security key and the first random value, and encrypted with a public key of the second device. 2 receiving a message from the first device;
Decrypting, by the second device, the second message and transmitting a third random value among the third and fourth random values included in the second message to a first device to inform a key agreement; And
If the second device matches the first random value included in the second message and the first random value generated by the second device, the second device determines that the key agreement has been made, and thus generates the second random value generated by the second device. Generating a first security key to be used for encrypted communication with a first device from a value and a fourth random value included in the second message. Way. The method according to claim 6,
Receiving, by a second device, a key setting request to the first device to receive a certificate of the first device; And
The second device further validating a certificate of the first device;
And if the certificate of the first device is valid, send the first message to the first device. The method of claim 6, wherein the second device,
A third message including a fifth random value generated for key agreement in the third device and a sixth random value generated for deriving a security key from the first device and encrypted with the public key of the first device, in the third device Receiving from the third device a fourth message including a seventh random value generated for deriving a security key with the second device and encrypted with the public key of the second device;
Transmitting a third message included in the fourth message, a fifth message including a first random value and a second random value generated by the fourth message and encrypted with a first security key to the first device;
Receiving a first random value and a third random value from the third device, and transmitting the third random value to the first device;
If the received first random value coincides with the first random value generated by the self, using the seventh random value included in the fourth message and the second random value generated by the third device, Generating a third security key for the encrypted communication of the security key setting method using a public key based key sharing mechanism, characterized in that it further comprises. 9. The method of claim 8,
Transmitting a certificate of the first device and a certificate of the first device to the third device if a key setting request is received from the third device before the second device receives the fourth message. A security key setting method using a public key based key sharing mechanism. The device of claim 8, wherein the second device is
Receiving a certificate of a third device from the third device together with the fourth message, and transmitting the received third device's certificate together with the fifth message to the first device; How to set up security key using mechanism. A method in which a third device sets a security key for encrypted communication with first and second devices, the third device comprising
Generate a fifth random value for key agreement, a sixth random value for deriving a security key with a first device, and a seventh random value for deriving a security key with a second device, and generate the fifth and sixth random values Generates a third message encrypted with the public key of the first device, generates a fourth message encrypted with the third message, identification information of the third device, and the seventh random value with the public key of the second device, Sending the fourth message to a second device;
From the first device receiving the third message through the second device, a first random value for key agreement generated in the second device and a second random value for deriving a security key, a key generated in the first device Receiving a sixth message including a third random value for agreement, a fourth random value for deriving a security key, and the fifth random value and encrypted with a public key of a third device;
Extracting first and third random values from the sixth message and transmitting the first and third random values to the second device;
If the fifth random value included in the sixth message and the fifth random value generated by the sixth message match, the second random value included in the sixth message and the seventh random value generated by the sixth message are compared with the second device. Generating a third security key for encrypted communication, and generating a second security key for encrypted communication with the first device from a fourth random value included in the sixth message and a sixth random value generated by the third message; Security key setting method using a public key-based key sharing mechanism, characterized in that it comprises a. 12. The method of claim 11,
Requesting, by the third device, to set a key from the second device, acquiring certificates of the first and second devices;
Further comprising validating a certificate of the first and second devices,
And if the certificates of the first and second devices are valid, transmitting the fourth message to the second device.

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