KR20080067550A - Method and system for three-party authenticated key exchange using smart cards - Google Patents

Abstract

A method and a system for exchanging a key among three-party using a smart card and a recording medium thereof are provided to improve the security by performing an authentication and key exchange between a client and a client without exposing session key information, which is exchanged between the clients, to a server. A method for exchanging a key among three-party using a smart card includes the steps of: selecting a first random number and a second random number as a predetermined random number at a smart card of a source client, transmitting an encryption sentence having the second random number to a server, and transmitting the encryption sentence having the first random number to a target client(310); transmitting the encryption sentence having the second random number to the target client(320); selecting third and fourth random numbers as a predetermined random number in the smart card of the target client, decoding the encryption sentence having the second random number, calculating the second random number, calculating a session key using the second and fourth random numbers(330), and transmitting the encryption sentence having the third and fourth random numbers to the source client(340); and decoding the encryption sentence having the third and fourth random numbers in the smart card of the source client, calculating the session key using the second and fourth random numbers, and sharing the session key(350).

Description

Three-way key exchange method using smart card, recording medium and three-party key exchange system using smart card {Method and System for three-party authenticated key exchange using smart cards}

1 illustrates a conventional smart card / terminal mutual authentication method.

2 is a block diagram of a three-party key exchange system using a smart card according to an embodiment of the present invention.

3 is a flowchart illustrating a three-party key exchange method using a smart card according to another embodiment of the present invention.

4 is a flowchart illustrating a three-party key exchange method using a smart card according to another embodiment of the present invention.

5 is a flowchart illustrating a three-party key exchange method using a smart card according to another embodiment of the present invention.

FIG. 6 is a detailed flowchart of a cipher text relay process in FIG. 3.

7 illustrates the process of FIG. 4 for each round.

The present invention relates to authentication and key exchange, and more particularly, to a three-way key exchange method using a smart card, a recording medium and a three-way key exchange system using a smart card.

The development of wired / wireless communication and the Internet has raised the need for various information security services. Therefore, the necessity of developing various technologies for practically implementing information security services has been raised, and many researches on these technologies are divided and executed for various purposes.

(Session) key exchange between subjects, which is the subject of this study, is a technology in the field of information security. Only one cryptographically secure key between entities communicating on a public network (e.g., ad-hoc networks, mobile networks, home networks), when confidential communication between entities is guaranteed, or when there is a need to authenticate each other The problem can easily be solved if you can share it. That is, secret communication can be implemented by encrypting the communication message with a shared key using a secret key encryption algorithm (for example, DES, AES, SEED, etc.). In addition, the integrity of the communication message is a MAC (Massage Authentication Code) algorithm. It can be implemented by using as a key of. And authentication to each other can be realized by proving that the information about the shared secret information (usually the key value) is known. That is, in order to implement secure communication, key exchange between objects must be preceded first. Therefore, key exchange is an indispensable element in information security technology.

1 is an example of a mutual authentication method between smart cards / terminals using a conventional common cryptography system. First, when user A requests authentication using a smart card, the terminal generates a random number R1 and delivers it to the smart card ( 1), the smart card receives this and transmits the result of encryption using the key KSA stored in the terminal together with the random number R2 generated by the smart card (2). Then, the terminal encrypts R1 using the user A's private key KSA, and compares it with the result delivered by the smart card, and if it is the same, recognizes it as a smart card of A (3), and then random number R2 delivered by the smart card. It is encrypted by the KSA and delivered to the smart card (4), the smart card authenticates the terminal through the same process (5).

However, in the case of the user authentication using the conventional cipher system, all of the user's keys must be stored in the terminal, and when a new user joins, there is a problem in stability as well as administrative difficulties in registering a new key in all the terminals.

Recently, in the implementation of a user authentication system using a conventional encryption system and a smart card, a user using a smart card using a user ID concept reduces the number of keys managed by a computer terminal to one and enables mutual authentication between the card and the terminal. An authentication method is presented.

In other words, the conventional authentication method using a smart card generates an authentication secret key of an arbitrary user in the card issuing center and issues an ID, a secret information, a password and an authentication secret key, which are disclosed to the smart card, User authentication is performed using the stored information. At this time, the step of issuing the ID, password and authentication secret key is a step in which the user determines the ID to be used by the user to request registration with the card issuance center along with the password, and the card issuance center uses the authentication secret key using the ID Comprising a step of issuing, and issuing a smart card containing the ID of the public information and the password and authentication secret of the secret information.

At this time, for authentication and key exchange between two entities (client-server), the client performs this by using a smart card issued from the server. This technique makes it impossible to authenticate and exchange keys between clients.

In the conventional key exchange method, five data exchanges are required for two clients to perform authentication and key exchange. That is, five rounds are required.

In addition, in the conventional key exchange method, the client performs this by using a smart card issued from the server for authentication and key exchange between two entities (client-server). However, this technique does not allow clients to authenticate and exchange keys.

Therefore, the conventional key exchange method using a smart card requires a large number of data exchanges for authentication between clients, fast authentication is not possible, and authentication and key exchange between clients are not easy.

Accordingly, the first technical problem to be achieved by the present invention is to enable client-client authentication and key exchange, improve server security by preventing the server from knowing session key information exchanged between clients, and improve key exchange. It is possible to limit the number of data exchanges for three times or less, and to provide a three-way key exchange method using a smart card capable of high-speed authentication while using a smart card.

It is a second object of the present invention to provide a computer-readable recording medium having recorded thereon a program for executing a three-way key exchange method using the smart card on a computer.

The third technical problem to be achieved by the present invention is to provide a three-way key exchange system using a smart card to which the three-way key exchange method using the smart card is applied.

In order to achieve the first technical problem, the present invention provides a key exchange method of a system including a server, a source client issued with a smart card from the server, and a target client, wherein the random card is a random number in the smart card of the source client. Selecting a first random number and a second random number, transmitting a cipher text including the second random number to the server, and transmitting a cipher text including the first random number to the target client, wherein the server sends the cipher text including the first random number to the target client. Transmitting a cipher text including a second random number, selecting a third random number and a fourth random number which are random numbers in the smart card of the target client, and then deciphering the cipher text including the second random number to calculate a second random number Compute a session key using the second random number and the fourth random number, and include the third random number and the fourth random number. Transmitting a cipher text to the source client and decrypting the cipher text including the third random number and the fourth random number in the smart card of the source client, and calculating a session key using the second random number and the fourth random number. Provided is a three-way key exchange method using a smart card, including sharing a session key.

In order to achieve the second technical problem, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the three-way key exchange method using the smart card on a computer.

In order to achieve the third technical problem, the present invention provides a system including a target client, a source client to authenticate with the target client, and a server for issuing a first smart card and a second smart card to the source client and the target client, respectively. Wherein the source client selects a random random first and second random numbers, generates a cipher text including the second random number and a cipher text including the first random number, and selects a third random number selected by the target client. And decrypting a cipher text including a fourth random number, computing a session key using the second random number and the fourth random number, and sharing a session key with the first smart card and the second random number. And transmit a cipher text including the first random number to the target client. And a target, the target client decrypts a cipher text including the second random number to calculate a second random number, selects a third random number and a fourth random number which are random numbers, and selects the second random number and the fourth random number. A target cipher text is transmitted using a second smart card for calculating a session key using the session key and generating a cipher text including the third random number and the fourth random number, and a cipher text including the third random number and the fourth random number to the source client. And a server, wherein the server provides a three-way key exchange system using a smart card including a server ciphertext relay that transmits a ciphertext including the second random number to the target client.

The present invention relates to a method in which two entities carrying a smart card (client-client) indirectly mutually authenticate with the help of a server that is a smart card issuer and exchange a cryptographically secure session key.

An object of the present invention is to provide a technical proposal for client-client authentication and key exchange. The present invention prevents the server from knowing the session key information exchanged between clients. An object of the present invention is to limit the number of times of data exchange to three or less.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention. However, embodiments of the present invention illustrated below may be modified in many different forms, and the scope of the present invention is not limited to the embodiments described below.

2 is a block diagram of a three-party key exchange system using a smart card according to an embodiment of the present invention.

In the following description, an active client attempting a key exchange is defined as a source client and a passive client that is a target of a key exchange as a target client. In addition, the first smart card means a smart card of the source client, and the second smart card means a smart card of the target client.

The server 200 includes a database 201 and a server cipher text relay 202.

The database 201 stores a first verifier and a second verifier.

The server ciphertext relay unit 202 transmits the ciphertext including the second random number to the target client 220.

In this case, the first smart card 211 stores the first verifier applying the ID of the source client 210 and the master key of the server 200 to the hash function, and the second smart card 221 stores the target client 220. The ID and the master of the server 200 may store the second verifier applied to the hash function.

Preferably, the server cipher text relay unit 202 decrypts the cipher text including the second random number using the first verifier stored in the database 201 to obtain the ID of the source client 210 and the ID of the target client 220. Can be calculated. At this time, the server cipher text relay unit 202 may transmit the cipher text encrypted with the second random number as the second verifier to the target client 220 to relay the cipher text.

The source client 210 includes a first smart card 211, a smart card reader 212, and a source cipher text transmission unit 213.

The first smart card 211 is issued by the server 200 and inserted into the smart card reader 212 for authentication and key exchange.

The first smart card 211 selects a random random number of the first random number and the second random number, and generates a cipher text including the second random number and a cipher text including the first random number. In addition, the first smart card 211 decrypts the cipher text including the third random number and the fourth random number selected by the target client 220, and calculates a session key using the second random number and the fourth random number to share the session key. do.

The smart card reader 212 reads the information stored in the first smart card.

The source cipher text transmission unit 213 transmits the cipher text including the second random number to the server 200, and transmits the cipher text including the first random number to the target client 220.

The target client 220 includes a second smart card 221, a smart card reader 222, and a target cipher text transmission unit 223.

The second smart card 221 is issued by the server 200 and inserted into the smart card reader 222 for authentication and key exchange.

The second smart card 221 calculates a second random number by decrypting a cipher text including the second random number. In addition, the second smart card 221 selects a third random number and a fourth random number which are random numbers, and calculates a session key using the second random number and the fourth random number. In addition, the second smart card 221 generates a cipher text including a third random number and a fourth random number.

The smart card reader 222 reads out information stored in the second smart card.

The target cipher text transmission unit 223 transmits the cipher text including the third random number and the fourth random number to the source client 210.

3 is a flowchart illustrating a three-party key exchange method using a smart card according to another embodiment of the present invention.

First, after selecting a random number of the first random number and the second random number in the smart card of the source client, and transmits the cipher text including the second random number to the server, and transmits the cipher text including the first random number to the target client ( 310 courses). At this time, the cipher text including the first random number may include the ID of the source client, and the cipher text including the second random number may include the ID of the source client and the ID of the target client.

Next, the server transmits the cipher text including the second random number to the target client (step 320). In this case, the server selects a client to transmit the cipher text according to the ID of the client existing in the cipher text including the second random number, that is, the ID of the target client.

When the cipher text including the second random number is delivered to the target client, the third random number and the fourth random number, which are random numbers, are selected in the smart card of the target client, and then the second random number is calculated by decrypting the cipher text including the second random number. In operation 330, a session key is calculated using the second and fourth random numbers.

When the session key is calculated, the cipher text including the third random number and the fourth random number is transmitted to the source client (step 340).

Finally, the ciphertext including the third random number and the fourth random number is decrypted by the smart card of the source client, and the session key is shared by calculating the session key using the second random number and the fourth random number (step 350).

4 is a flowchart illustrating a three-party key exchange method using a smart card according to another embodiment of the present invention.

First, after selecting a random number of the first random number and the second random number in the smart card of the source client, and transmits the cipher text including the second random number to the server, and transmits the cipher text including the first random number to the target client ( 410 courses). At this time, the cipher text including the first random number may include the ID of the source client, and the cipher text including the second random number may include the ID of the source client and the ID of the target client.

Next, the server transmits the cipher text including the second random number to the target client (step 420). In this case, the server selects a client to transmit the cipher text according to the ID of the client existing in the cipher text including the second random number, that is, the ID of the target client.

When the cipher text including the second random number is delivered to the target client, the third random number and the fourth random number, which are random numbers, are selected in the smart card of the target client, and then the second random number is calculated by decrypting the cipher text including the second random number. The session key is calculated using the second random number and the fourth random number (step 430).

When the session key is calculated, the cipher text including the third random number and the fourth random number is transmitted to the source client (step 440). At this time, the cipher text including the third random number and the fourth random number includes a cipher text obtained by encrypting the first random number using a session key calculated by the target client.

Next, if a result of decrypting the ciphertext that encrypts the first random number using the session key calculated by the source client does not match the first random number (step 445), the protocol with the target client is terminated.

If the result of decrypting the cipher text that encrypts the first random number matches the first random number, the smart card of the source client decrypts the cipher text including the third random number and the fourth random number, and the session uses the second random number and the fourth random number. Compute the key (step 450).

In operation 460, the ciphertext obtained by decrypting the ciphertext including the third random number and the fourth random number by the source client is encrypted using the session key calculated by the source client to the target client.

Finally, if the result of decrypting the ciphertext encrypted with the third random number with the session key calculated by the target client does not match the third random number (step 465), the session key calculated by the target client is deleted (step 469). At this time, if the result of decrypting the ciphertext with the session key calculated at the target client is identical to the third random number, it is determined that the session key calculated at the source client and the target client is the same, and the source client and the target client may perform secret communication. have.

5 is a flowchart illustrating a three-party key exchange method using a smart card according to another embodiment of the present invention.

First, the source client and the target client register their respective passwords with the server.

Next, the server issues a smart card to the registered clients of the password (step 501). At this time, the source client receives a smart card stored with the first verifier applying the ID of the source client and the master key of the server to the hash function from the server, and the target client receives the ID of the target client and the master key of the server from the server. The applied second verifier receives a stored smart card.

Next, if a password is input to the client to be authenticated, that is, the source client, it is determined whether the verifier calculated using the input password matches the first verifier (step 502).

At this time, if the validator calculated using the input password matches the first validator, the random text first random number and the second random number are selected in the smart card of the source client, and the server encrypts the cipher text including the second random number. In operation 510, the ciphertext including the first random number is transmitted to the target client. At this time, if the verifier calculated using the input password does not match the first verifier, all procedures are terminated.

Next, the server transmits the cipher text including the second random number to the target client (S520).

When the cipher text including the second random number is delivered to the target client, the third random number and the fourth random number, which are random numbers, are selected in the smart card of the target client, and then the second random number is calculated by decrypting the cipher text including the second random number. In operation 530, the session key is calculated using the second and fourth random numbers.

When the session key is calculated, the cipher text including the third random number and the fourth random number is transmitted to the source client (S540).

Finally, the ciphertext including the third random number and the fourth random number is decrypted in the smart card of the source client, and the session key is shared using the second random number and the fourth random number (step 550).

FIG. 6 is a detailed flowchart of a ciphertext relay process 320 in FIG. 3.

First, the server decrypts the cipher text including the second random number using the first verifier to calculate the second random number, the ID of the source client, and the ID of the target client (step 621).

Next, the server generates a cipher text encrypting the second random number as the second verifier (622).

Finally, the ciphertext encrypting the second random number is transmitted to the target client (step 623). Since the second verifier is stored in the smart card of the target client, the target client which has normally issued the smart card from the server may decrypt the cipher text that encrypts the second random number with the second verifier.

7 illustrates the process of FIG. 4 for each round.

는 클라이언트 A의 패스워드이다. 또한, SE=(K,E,D)는 대칭키 암호알고리즘이고, ASE=(PK,PE,PD)는 공개키 암호알고리즘. K(PK)는 키 생성 알고리즘이고, E(PE)는 암호화 알고리즘, D(PD)는 복호화 알고리즘이다. H는 암호학적으로 안전한 일방향 해쉬함수이다. Hereinafter, A and B represent IDs of clients and S represents IDs of servers.

Is the password for client A. Also, SE = (K, E, D) is a symmetric key cryptographic algorithm, and ASE = (PK, PE, PD) is a public key cryptographic algorithm. K (PK) is a key generation algorithm, E (PE) is an encryption algorithm, and D (PD) is a decryption algorithm. H is a cryptographically secure one-way hash function.

에 대응된다. 또한, 제1난수, 제2난수, 제3난수 및 제4난수는 각각

에 대응된다.In addition, the first and second verifiers described above

Corresponds to. In addition, the first random number, the second random number, the third random number and the fourth random number are respectively

Corresponds to.

Before performing the process illustrated in FIG. 7, the following registration step may be performed.

그리고

를 연산 후, 스마트카드에

와 키 생성에 필요한 알고리즘들 (SE,ASE,H) 을 저장하여 이것을 A에게 발급한다. 여기서 xs는 서버의 마스터 키 값이다. That is, when the client A is issued a smart card from the server S, it registers its own password. The server

And

To the smart card

And algorithms (SE, ASE, H) necessary for key generation are stored and issued to A. Where xs is the server's master key value.

Before performing the process illustrated in FIG. 7, the following authentication step may be performed.

라 하자. 이때, 스마트카드 리더기를 스마트카드가 탑재된 모바일 기기로 생각할 수 있다.When the client A wants to exchange a session key with the client B, A inserts his smart card into the card reader and inputs the password registered at the time of issuing the smart card. Entered password

Let's do it. In this case, the smart card reader may be regarded as a mobile device equipped with a smart card.

그리고

를 연산한다. 그리고

인지 확인한다. 만약 두 값이 일치하지 않으면 동작을 멈춘다. 만약 이 단계를 통과하면 키 교환을 수행한다.The smart card checks whether the password information entered by the client matches.

And

Calculate And

Check if it is. If the two values do not match, the operation stops. If this step passes, the key exchange is performed.

를 선택한다. 그리고 일회용 공개키/비밀키 쌍 (y,x)를 선택한다. A는 S에게

를 그리고 B에게

값들을 전송한다.In round 1, client A's smart card is random

Select. And select the disposable public / private key pair (y, x). A is S

And to B

Send the values.

를 연산 후에 A에게서 받은 암호문

을 복호화 한다. 그 복호한 결과에

가 포함되어 있는지 확인한다. 그리고

를 연산한 후,

를 B에게 전송한다. In round two, S

Ciphertext received from A after

Decrypt On the decrypted result

Make sure it is included. And

After computing

To B.

를 선택 후,

를 복호화하여

값을 얻는다. 그리고 세션키 값

을 연산한 후,

를 A에게 전송한다.On the other hand, B's smart card is a random number

After selecting

By decrypting

Get the value. And the session key value

After computing

Is sent to A.

인지를 확인한다. 만약 두 값이 같지 않으면 프로토콜을 종료한다. 만약 두 값이 일치하면 A는 B와 동일한 세션 키를 공유했다는 것을 확인할 수 있다. 라운드 3에서, A의 스마트카드는

를 복호하여

를 얻는다. 그리고 세션 키

를 연산한다. A는

를 B에게 전송한다. B는

가 일치하는지 확인한다. 만약 두 값이 일치하면 B는 A와 동일한 세션 키를 공유했다는 것을 확인할 수 있다. 만약 두 값이 일치하지 않으면, B의 스마트카드는 세션 키 sk를 사용하지 않고 삭제한다.In round three, A's smart card

Check if it is. If the two values are not the same, the protocol is terminated. If the two values match, we can see that A shared the same session key as B. In round three, A's smart card

To decrypt

Get And session key

Calculate A is

To B. B is

To see if it matches. If the two values match, we can see that B shared the same session key as A. If the two do not match, the smart card in B is deleted without using the session key sk.

와 새로 바꾸고자하는 패스워드

를 입력한다. 스마트카드는 입력된

를 이용하여

를 연산한 후,

를 연산한다. 그리고

인지를 확인한다. 만약 두 값이 일치하지 않으면, 패스워드 변경요청을 거절한다. On the other hand, if the client A wants to change the password used to access the smart card, A inserts the smart card into the smart card reader and then transfers the old password.

And password you want to change

Enter. Smart card is input

Using

After computing

Calculate And

Check if it is. If the two values do not match, the password change request is rejected.

와

를 연산 후에 스마트카드 내에 저장된

값을

값으로 교체한다.If the two values match,

Wow

Stored in the smart card after

Value

Replace with a value.

In the present invention, in order to check whether the user has the authority to use the smart card, the user is to input the password information. For users who have passed this step, the key exchange step can be performed.

In the authentication and key exchange phase, each client can exchange a common session key using its own smart card. In the smart card, client-specific secret values are stored, and each client uses this value to share the session key. At this time, since there is no secret value in common between the two clients, a server that knows all the secret values of each client serves as an intermediary to assist key exchange in the middle.

Accordingly, the present invention enables client-client authentication and key exchange.

에 대한 정보를 얻을 수 없다.On the other hand, since the server knows the master key value, it is assumed that the server is a trust authority. Although a trusted third party (server) acts as an intermediary for the authentication and key exchange between the two clients, viewing the data exchanged between the two clients makes it impossible to know the information about the session key. This makes it possible to lower the trust dependency on the server. In the present invention, the server knows the random number rA selected by the client A, but does not know the secret key xA corresponding to the disposable public key yA of A, so that the random number rB selected from the ciphertext PEy (rB) Not known. Consequently the session key

Can't get information about

Accordingly, the present invention prevents the server from knowing session key information exchanged between clients.

In addition, the present invention can limit the number of times of data exchange to three or less.

Table 1 is a comparison table of the present invention and the prior art published in the paper.

In Table 1, the present invention requires three data exchanges in order for two clients to exchange authentication and session keys, and client A and B can also check whether each other computed the same session key.

In the prior arts, a technology that provides the same safety as the present invention is Jaung's Scheme2, but this technique requires 5 data exchanges. If the number of data exchanges can be reduced as in the present invention, faster authentication and key exchange can be performed.

The present invention is a technology that allows two clients to indirectly authenticate and exchange keys by using a server, which is a smart card issuing entity, as an intermediary for enabling authentication and key exchange between clients and clients.

In the present invention, the intervention of the server is required, but in order to lower the trust dependency of the server, the server does not know the session key shared by the two clients when viewing the data exchanged between the clients. In the process of performing authentication and key exchange, the number of exchanges of data is reduced to three so that two entities can perform key exchange efficiently.

Preferably, the program for executing the tripartite key exchange method using the smart card of the present invention may be provided by recording a program for executing in a computer on a computer-readable recording medium.

The invention can be implemented via software. When implemented in software, the constituent means of the present invention are code segments that perform the necessary work. The program or code segments may be stored on a processor readable medium or transmitted by a computer data signal coupled with a carrier on a transmission medium or network.

The computer-readable recording medium includes all kinds of recording devices in which data is stored which can be read by a computer system. Examples of computer-readable recording devices include ROM, RAM, CD-ROM, DVD ± ROM, DVD-RAM, magnetic tape, floppy disks, hard disks, optical data storage devices, and the like.

The computer readable recording medium can also be distributed over network coupled computer devices so that the computer readable code is stored and executed in a distributed fashion.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary and will be understood by those of ordinary skill in the art that various modifications and variations can be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the present invention, it is possible to improve the security by enabling the authentication and key exchange between the client and the client, by not allowing the server to know the session key information exchanged between the clients, The number of exchanges of data can be limited to 3 or less, high-speed authentication is possible while using a smart card, and it is also possible to check whether or not the same session key is computed between clients for key exchange.

Claims (10)

In the key exchange method of the system comprising a server, a source client and a target client issued a smart card from the server, After selecting the random number of the first random number and the second random number in the smart card of the source client, and transmits the cipher text including the second random number to the server, and transmits the cipher text including the first random number to the target client Transmitting; Transmitting a cipher text including the second random number from the server to the target client; After selecting the third random number and the fourth random number which are random numbers in the smart card of the target client, the second random number is calculated by decrypting the cipher text including the second random number, and using the second random number and the fourth random number. Calculating a session key and transmitting a cipher text including the third random number and the fourth random number to the source client; And A smart card comprising decrypting a cipher text including the third random number and the fourth random number in the smart card of the source client, and calculating a session key using the second random number and the fourth random number to share the session key. Three-way key exchange method using The method of claim 1, The ciphertext including the second random number is An ID of the source client and an ID of the target client, The ciphertext including the first random number is Three-way key exchange method using a smart card, characterized in that it comprises the ID of the source client. The method of claim 2, The step of transmitting a cipher text including the first random number to the target client The source client receives a smart card storing a first validator that applies the ID of the source client and the master key of the server to the hash function from the server, and the target client receives the ID of the target client and the server from the server. And a second verifier applying the master key to the hash function to receive the stored smart card. The method of claim 3, wherein The step of transmitting a cipher text including the second random number to the target client Calculating an ID of the source client and an ID of the target client by decrypting a cipher text including the second random number using the first verifier in the server; And And transmitting, at the server, the cipher text that encrypts the second random number to the target client using the second verifier. The method of claim 1, The ciphertext including the third random number and the fourth random number is A ciphertext that encrypts the first random number using a session key calculated at the target client, Computing the session key using the second random number and the fourth random number to share the session key And a step of terminating a protocol with the target client if a result of decrypting the ciphertext that encrypts the first random number using the session key calculated by the source client does not match the first random number. Three-way key exchange method. The method of claim 1, Transmitting, by the source client, an encryption text obtained by decrypting an encryption text including the third random number and a fourth random number to the target client by encrypting the third random number calculated by the session key calculated by the source client; And If the decryption result of encrypting the third random number with the session key calculated at the target client does not match the third random number, deleting the session key calculated at the target client; Three-way key exchange method using a smart card. A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 6. A system comprising a target client, a source client to authenticate with the target client, and a server that issues a first smart card and a second smart card to the source client and the target client, respectively. The source client Select a random random first random number and a second random random number, generate a ciphertext including the second random number and a ciphertext including the first random number, and include a third random number and a fourth random number selected by the target client A first smart card that decrypts a cipher text, calculates a session key using the second random number and the fourth random number, and shares the session key; And A source cipher text transmission unit configured to transmit a cipher text including the second random number to the server, and transmit a cipher text including the first random number to the target client; The target client A second random number is calculated by decrypting a cipher text including the second random number, a third random number and a fourth random number which are random numbers are selected, and a session key is calculated using the second random number and the fourth random number, A second smart card for generating a cipher text including the third random number and the fourth random number; And A target cipher text transmission unit for transmitting a cipher text including the third random number and the fourth random number to the source client, The server is A three-way key exchange system using a smart card including a server cipher text relay that transmits a cipher text including the second random number to the target client. The method of claim 8, The first smart card is A first verifier that applies an ID of the source client and a master key of the server to a hash function, The second smart card is A second verifier that applies an ID of the target client and a master key of the server to a hash function, The server is A database storing the first verifier and the second verifier, The server cipher text relay unit The ID of the source client and the ID of the target client are calculated by decrypting a cipher text including the second random number using the first verifier, and the cipher text that encrypts the second random number using the second verifier is the target client. Three-way key exchange system using a smart card, characterized in that for transmitting to. The method of claim 8, The source client and target client And a smart card reader for reading information stored in the first smart card and the second smart card.

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