KR100458955B1 - Security method for the Wireless LAN - Google Patents

Abstract

The present invention relates to a wireless LAN security method, comprising a server (10), at least one or more access points (20) in wired LAN communication with the server (10), and at least one or more in wireless LAN communication with the access point (20). In the WLAN security system including the wireless terminal 30, the communication between the access point and the server, the access point and the wireless terminal period in the symmetric key method, and the symmetric key used for this symmetric key encryption communication from the server By distributing according to the key encryption method, encrypted communication is possible not only between the access point and the server but also between the access point and the wireless terminal, thereby preventing the access of unauthorized malicious users and generating and distributing the encryption key for each session. Therefore, there is little possibility of key exposure, and random number is used to prevent replay attack.

Description

Security method for the Wireless LAN

The present invention relates to a WLAN security method, and relates to a security technology between an access point and a wireless terminal in a wireless network environment.

The conventional WLAN system does not provide user authentication in communication between an access point and a wireless terminal, which serves as a medium for connecting a wireless terminal to a wired / wireless network, and has a very weak encryption communication. It was a situation.

That is, in the conventional wireless LAN system, since the user does not authenticate the wireless terminal at the access point, a malicious user can easily access the access point, which includes many risks, and the encrypted communication between the access point and the wireless terminal. Also, the encryption key used for encryption is statically assigned, and there is a risk of exposure of the encryption key.Initial vector used for encryption is transmitted in plain text so that the initialization vector can be reused. It had a possible problem.

The Initial Vector is a common cipher when encrypting a message. Some messages can always have the same beginning (e.g. From, which is used for e-mail, http: // at the beginning of the homepage address, etc.). Because there is a high risk of exposure to hacking, it means any value inserted at the beginning of the message to prevent this.

Therefore, the present inventors can prevent user's access by unauthorized user by making user authentication between access point and wireless terminal, and reduce the possibility of key exposure by generating and distributing encryption key for each session. The research on the wireless LAN security method that can solve the shortcomings of the encryption technology in the conventional wireless LAN system that is very vulnerable in terms of security because it can prevent the retransmission attack using the.

The present invention has been invented under the above-described aspect, and provides a wireless LAN security method capable of preventing encrypted access between an access point and a wireless terminal to prevent unauthorized access by a user.

It is still another object of the present invention to provide a WLAN security method with less possibility of key exposure since the encryption key is generated and distributed for each session.

Still another object of the present invention is to provide a WLAN security method that can prevent retransmission attacks using random numbers.

According to an aspect of the present invention for achieving the above object, a wireless LAN security method according to the present invention is a server for the first symmetric key (K _{AP, S1} ) request information used for encrypted communication between the access point and the server Transmitting; Receiving first encryption information (EK1) including a first symmetric key (K _{AP, S1} ) encrypted using the public key (K _{AP, PUB} ) of the access point from the server; Acquiring the first symmetric key (K _{AP, S1} ) by decrypting the first encryption information (EK1) using a secret key (K _{AP, PRI} ) of an access point; Transmitting second symmetric key (K _{AP, S2} ) request information used for encrypted communication between the access point and the wireless terminal period to the server when the wireless terminal accesses the access point; Second encryption information (EK2) including a second symmetric key (K _{AP, S2} ) encrypted using the first symmetric key (K _{AP, S1} ) from the server _, and a public key (K _{MS, PUB} ) of a wireless terminal. Receiving third encryption information (EK3) including the second symmetric key (K _{AP, S2} ) encrypted using the < RTI ID = 0.0 > Wherein the first symmetric key (K _{AP, S1)} the second encrypted information (EK2) by decoding the first the second obtaining the symmetric key (K _{AP, S2),} and the third encrypted information (EK3) using a wireless terminal Transmitting; Secret of the mobile station key (K _{MS, PRI)} for using the third and decoding encoded information (EK3) the second symmetric key (K _{AP, S2)} the obtained wireless terminal and the second symmetric key (K _{AP And S2} ) and an access point side execution module including encrypting and communicating with the server using the first symmetric key (K _{AP, S1} ).

According to an additional aspect of the present invention, in the WLAN security method according to the present invention, the server is logically or physically divided into two servers, one of which distributes the first symmetric key (K _{AP, S1} ) and The other server distributes the second symmetric key (K _{AP, S2} ).

According to still another aspect of the present invention, there is provided a WLAN security method comprising: receiving, from an access point, first symmetric key (K _{AP, S1} ) request information used for encrypted communication between the access point and a server; Generating first encryption information (EK1) including a first symmetric key (K _{AP, S1} ) using a public key (K _{AP, PUB} ) of the access point, and transmitting it to the access point; Receiving second symmetric key (K _{AP, S2} ) request information used for encrypted communication between the access point and the wireless terminal period from the access point when the wireless terminal connects to the access point; Generating a second encryption information (EK2) for using the first symmetric key (K _{AP, S1)} and a second symmetric key (K _{AP, S2)} and, using the public key (K _{MS, PUB)} of the mobile station Generating third encryption information (EK3) including the second symmetric key (K _{AP, S2} ) and transmitting them to the access point; And a server-side execution module including encrypting and communicating data transmitted and received between the access point and the server using the first symmetric key (K _{AP, S1} ).

1 is a schematic diagram of a WLAN security system to which a WLAN security method according to the present invention is applied;

2 is a flowchart according to an embodiment of an access point side execution module of a WLAN security method according to the present invention;

3 is a flowchart according to another embodiment of an access point side execution module of a WLAN security method according to the present invention;

4 is a flowchart of an embodiment of a server-side execution module of a WLAN security method according to the present invention;

<Description of the symbols for the main parts of the drawings>

10: server 20: access point

30: wireless terminal

Hereinafter, a WLAN security method according to the present invention will be described in more detail with reference to the accompanying drawings.

1 is a schematic diagram of a WLAN security system to which a WLAN security method according to the present invention is applied.

As shown in the figure, the WLAN security system according to the present invention includes a server 10, at least one access point 20 in wired LAN communication with the server 10, and the access point 20 and a WLAN. At least one wireless terminal 30 in communication with the.

The server 10 provides a first symmetric key for encrypted communication between the server 10 and the access point 20 and a second symmetric key for encrypted communication between the access point 20 and the wireless terminal 30. Encrypt and distribute using public key method.

The server 10 may be logically or physically divided into two servers. One of the two servers distributes the first symmetric key, and the other server distributes the second symmetric key. You can do that.

The access point 20 is a network device that serves as a medium for connecting the wireless terminal 30 to a wired / wireless network. The access point 20 is an encryption device for the encrypted communication between the server 10 and the access point 20 from the server 10. Receiving the first symmetric key, and receives the second symmetric key for encrypted communication between the access point 20 and the wireless terminal 30 from the server 10 when the wireless terminal 30 is connected to the wireless terminal 30 To send.

The wireless terminal 30 is a device for communicating in a wireless network environment such as a notebook computer, PDA, mobile communication terminal.

More specifically, the WLAN security method according to the present invention will be described.

2 is a flowchart according to an embodiment of an access point side execution module of a WLAN security method according to the present invention.

In step S101, the access point transmits first symmetric key (K _{AP, S1} ) request information used for encrypted communication between the access point and the server to the server.

At this time, the request information may be transmitted by encrypting with the public key (K _{S, PUB} ) of the server, in which case, the server that receives it decrypts it with its _private key (K _{S, PRI} ).

In step S102, the access point receives first encryption information EK1 including the first symmetric key K _{AP, S1} encrypted using the public key K _{AP, PUB} of the access point from the server.

In operation S103, the first encryption information EK1 is decrypted using the access point's secret keys K _{AP and PRI} to obtain the first symmetric key K _{AP and S1} .

That is, the server includes a public key (K _{AP, PUB} ) of the access point and a first symmetric key (K _{AP, S1} ) used for encrypted communication between the access point and the server _, and the access point has its own secret key. It includes (K _{AP, PRI} ), the access point decrypts and obtains the first symmetric key (K _{AP, S1} ) encrypted by the public key encryption scheme and transmitted from the server.

When the wireless terminal connects to the access point in step S104, the access point transmits second symmetric key (K _{AP, S2} ) request information used for encrypted communication between the access point and the wireless terminal period to the server.

At this time, the request information may be transmitted by encrypting with the public key (K _{S, PUB} ) of the server, in which case, the server that receives it decrypts it with its _private key (K _{S, PRI} ).

In step S105, the second encryption information (EK2) including the second symmetric key (K _{AP, S2} ) encrypted by the access point using the first symmetric key (K _{AP, S1} ) from the server _, and of the wireless terminal The third encryption information EK3 including the second symmetric key K _{AP and S2} encrypted using the public key K _{MS and PUB} is received.

According to the request information of the second symmetric key (K _{AP, S2} ) in the step S104, the server uses the first symmetric key (K _{AP, S1} ) to include a second encryption key including the second symmetric key (K _{AP, S2} ). The information EK2 is generated, and the third encryption information EK3 including the second symmetric key K _{AP, S2} is generated using the public key K _{MS and PUB} of the wireless terminal.

The second encrypted information EK2 and the third encrypted information EK3 generated in this way are transmitted from the server to the access point through step S105.

Thereafter, the second encryption information EK2 including the second symmetric key K _{AP, S2} is decrypted at an access point, and transmits the second symmetric key K _{AP, S2} to the access point. The third encryption information EK3 including the symmetric key K _{AP and S2} is decrypted by the wireless terminal to transmit the second symmetric key K _{AP and S2} to the wireless terminal.

In step S106, the access point decrypts second encryption information EK2 using the first symmetric key K _{AP, S1} to obtain the second symmetric key K _{AP, S2} , and the third encryption information ( EK3) is transmitted to the wireless terminal.

Since the second encryption information EK2 is encrypted by the server using the first symmetric key K _{AP, S1} , the access point acquires the first symmetric key K _{AP, S1} according to the symmetric key encryption method. The second symmetric key (K _{AP, S2} ) is obtained by decryption _, and the third encryption information EK3 transmitted from the server is transmitted to the wireless terminal.

In step S107, the access point decrypts the third encryption information EK3 using the secret key K _{MS, PRI of} the radio terminal to obtain the second symmetric key K _{AP, S2} . Encrypted communication using two symmetric keys (K _{AP, S2} ), and encrypted communication with the server using the first symmetric key (K _{AP, S1} ).

Since the third encryption information (EK3) transmitted to the wireless terminal in step S106 is encrypted with the public key (K _{MS, PUB} ) of the wireless terminal according to the public key encryption scheme from the server, the wireless terminal that receives it has its own secret key. The second symmetric key (K _{AP, S2} ) is obtained by decoding using (K _{MS, PRI} ).

Accordingly, the access point performs encrypted communication with the wireless terminal using a second symmetric key (K _{AP, S2} ), and communicates with the server using a first symmetric key (K _{AP, S1} ).

In other words, the WLAN security method according to the present invention performs encrypted communication between the access point and the server, in the access point and the wireless terminal period by the symmetric key method, and encrypts the symmetric key used for this symmetric key encryption communication from the server. By distributing according to the scheme, encrypted communication is possible between the access point and the wireless terminal, thereby preventing access by malicious users. By generating and distributing encryption keys for each session, there is little possibility of key exposure.

3 is a flowchart according to another embodiment of an access point side execution module of a WLAN security method according to the present invention.

According to an additional aspect of the present invention, in step S101, the first symmetric key (K _{AP, S1} ) request information further includes a first random number n1 for preventing retransmission, and the first encryption information (EK1). May further include the first random number n1 and may be decoded by the step S103, and the step S103 may determine whether the first random number sent by the access point itself and the first random number transmitted from the server match.

Accordingly, retransmission is prevented by using the first random number and authentication is possible by using the first random number when distributing the first symmetric key (K _{AP, S1} ).

That is, the first symmetric key K _{AP, S1} is valid if the first random number sent by the access point itself and the first random number transmitted from the server match.

Meanwhile, according to another additional aspect of the present invention, in step S104, the second symmetric key (K _{AP, S2} ) request information further includes a second random number n2 for preventing retransmission, and the second encryption information. (EK2) may further include the second random number n2, and may be decrypted by step S106, and step S106 may determine whether the second random number sent by the access point itself and the second random number transmitted from the server match. have.

Therefore, retransmission is prevented using the second random number and at the same time _, authentication is possible using the second random number when distributing the second symmetric key (K _{AP, S1} ).

That is, the second symmetric key K _{AP, S2} is valid if the second random number sent by the access point itself and the second random number transmitted from the server match.

On the other hand, according to another additional aspect of the present invention, if the second random number sent by the access point itself and the second random number transmitted from the server, the step S106 is the second symmetric key (K _{AP, S2} ) The fourth encryption information EK4 including the third random number n3 for preventing retransmission is generated and further transmitted to the wireless terminal, and the access point execution module transmits a secret key (K _MS, The third random number n3 is obtained by decrypting the fourth encryption information EK4 using the second symmetric key K _{AP, S2} obtained by decrypting the third encryption information EK3 using _PRI ). Receiving fifth encryption information EK5 including the third random number n3 encrypted using the second symmetric key K _{AP, S2} generated by the wireless terminal (S106a), using a second symmetric key (K _{AP, S2)} and decrypting the fifth encrypted information (EK5) Wherein the may further comprise the step (S106b) to obtain a third random number (n3), and the access point, they determined that the third random number and the third random number from the wireless terminal sent match.

That is, when the second random number transmitted from the access point and the second random number transmitted from the server in step S106 match _, the third random number for preventing retransmission by the access point using the second symmetric key K _{AP, S2} . The fourth encryption information EK4 including (n3) is generated and transmitted to the wireless terminal.

The wireless terminal receiving the fourth encryption information EK4 decrypts the second symmetric key K _{AP, S2} obtained by decrypting the third encryption information EK3 using its secret key K _{MS, PRI} . The third random number n3 is obtained by decrypting the fourth encrypted information EK4.

In addition, the wireless terminal generates the fifth encryption information EK5 including the third random number n3 using the second symmetric key K _{AP, S2} and transmits it to the access point.

The access point receives the fifth encryption information EK5 in step S106a, and the access point decrypts the fifth encryption information EK5 using the second symmetric key K _{AP, S2} in step S106b. The third random number n3 is obtained, and it is determined whether the third random number sent by the access point itself and the third random number transmitted from the wireless terminal match.

Therefore, the third random number is used to prevent retransmission, and at the same time, the third random number sent by the access point itself and the third random number transmitted from the server are matched to each other to authenticate the terminal.

Therefore, retransmission can be prevented through the first to third random numbers, and authentication is confirmed.

Meanwhile, according to another additional aspect of the present invention, the server is logically or physically divided into two servers, one of which distributes the first symmetric key K _{AP, S1} , and the other server. May distribute the second symmetric key (K _{AP, S2} ).

That is, this means that the server is logically or physically separated into, for example, an authentication server and a key distribution server, and the first symmetric key (K _{AP, S1} ) is formed through the authentication server, and through the key distribution server. It means to distribute the second symmetric key (K _{AP, S2} ).

Since a server is generally logically or physically configured in a network, the first symmetric key K _{AP, S1} for encrypted communication between the server and the access point, and the second symmetric key for encrypted communication between the access point and the wireless terminal. It is preferable to distribute the keys K _{AP, S2} , respectively.

4 is a flowchart illustrating an embodiment of a server-side execution module of a WLAN security method according to the present invention.

In step S201 the server receives from the access point the first symmetric key (K _{AP, S1} ) request information used for encrypted communication between the access point and the server.

At this time, the request information is preferably transmitted by the access point encrypted with the public key (K _{S, PUB} ) of the server, the server receiving it decrypts it with its _private key (K _{S, PRI} ).

In step S202, the server generates the first encryption information EK1 including the first symmetric key K _{AP, S1} using the public key K _{AP, PUB of} the access point, and transmits it to the access point. .

That is, according to the first symmetric key (K _{AP, S1} ) request information used for the encrypted communication between the access point and the server from the access point, the server uses the public symmetric key encryption method (K _{AP, S1} ). Encrypted with the access point's public key (K _{AP, PUB} ) and transmitted to the access point

When the wireless terminal connects to the access point in step S203, the server receives from the access point second symmetric key (K _{AP, S2} ) request information used for encrypted communication in the wireless terminal period.

At this time, the request information is preferably transmitted by the access point encrypted with the public key (K _{S, PUB} ) of the server, the server receiving it decrypts it with its _private key (K _{S, PRI} ).

First symmetric key server is the step S204 (K _{AP, S1)} for using the second symmetric key (K _{AP, S2)} a second generate encrypted information (EK2), and the public key of the wireless terminal (K _MS containing _PUB ) generates third encryption information EK3 including the second symmetric key K _{AP, S2} , and transmits them to the access point.

Second encryption information (EK2) including the second symmetric key (K _{AP, S2} ) transmitted to the access point is decrypted at the access point to transfer the second symmetric key (K _{AP, S2} ) to the access point, The third encryption information EK3 including the second symmetric key K _{AP, S2} is transmitted back to the wireless terminal from the access point and decrypted to transfer the second symmetric key K _{AP, S2} to the wireless terminal. .

Step S205 encrypts and transmits data transmitted and received between the access point and the server using the first symmetric key K _{AP, S1} .

Accordingly, the access point performs encrypted communication with the wireless terminal using a second symmetric key (K _{AP, S2} ), and communicates with the server using a first symmetric key (K _{AP, S1} ).

In other words, the WLAN security method according to the present invention performs encrypted communication between the access point and the server, in the access point and the wireless terminal period by the symmetric key method, and encrypts the symmetric key used for this symmetric key encryption communication from the server. By distributing according to the scheme, encrypted communication is possible between the access point and the wireless terminal, thereby preventing access by malicious users. By generating and distributing encryption keys for each session, there is little possibility of key exposure.

By doing so, the object of the WLAN security method according to the present invention as described above is achieved.

As described above, the wireless LAN security method according to the present invention enables encryption communication between the access point and the server as well as the access point and the wireless terminal, thereby preventing the access of an unauthorized malicious user, and a session. By generating and distributing encryption keys for each, there is little possibility of key exposure, and there is a useful effect of preventing retransmission attacks using random numbers.

Although the present invention has been described with reference to the accompanying drawings, it will be apparent to those skilled in the art that various modifications may be made therein without departing from the scope of the invention, which is covered by the following claims.

Claims (6)

Transmitting _, by the access point, a server to the server, first symmetric key (K _{AP, S1} ) request information used for encrypted communication between the access point and the server (S101); Receiving, by the _{access point,} first encryption information (EK1) including a first symmetric key (K _{AP, S1} ) encrypted using a public key (K _{AP, PUB} ) of the access point from a server (S102); Acquiring, by the _{access point,} the first symmetric key (K _{AP, S1} ) by decrypting the first encryption information (EK1) using a secret key (K _{AP, PRI} ) of the access point (S103); Transmitting (S104) second symmetric key (K _{AP, S2} ) request information used for encrypted communication between the access point and the wireless terminal period to the server when the wireless terminal connects to the access point (S104); Second encryption information EK2 including the second symmetric key K _{AP, S2} encrypted by the access point using the first symmetric key K _{AP, S1} from the server _, and the public key of the wireless terminal. Receiving third encryption information (EK3) including the second symmetric key (K _{AP, S2} ) encrypted using K _{MS, PUB} (S105); The access point decrypts the second encryption information EK2 using the first symmetric key K _{AP, S1} to obtain the second symmetric key K _{AP, S2} , and the third encryption information EK3. Transmitting to the wireless terminal (S106); The second symmetry with the wireless terminal that the access point obtained the second symmetric key (K _{AP, S2} ) by decrypting the third encryption information (EK3) by using a secret key (K _{MS, PRI} ) of the wireless terminal. Encrypting and communicating with a key (K _{AP, S2} ) and communicating with the server using the first symmetric key (K _{AP, S1} ) (S107); WLAN security method comprising an access point side execution module comprising. The method of claim 1, The first symmetric key K _{AP, S1} request information further includes a first random number n1 for preventing retransmission, and the first encryption information EK1 further includes the first random number n1. Decryption by step S103, wherein step S103 further comprises determining whether the first random number sent by the access point itself and the first random number transmitted from the server match. The method according to claim 1 or 2, The second symmetric key K _{AP, S2} request information further includes a second random number n2 for preventing retransmission, and the second encryption information EK2 further includes the second random number n2. Decryption by step S106, the step S106 further comprises determining whether the second random number transmitted from the access point itself and the second random number transmitted from the server. The method of claim 3, wherein When the second random number sent by the access point and the second random number transmitted from the server coincide with each other, the third terminal for preventing retransmission encrypted by the access point using the second symmetric key (K _{AP, S2} ) in step S106. Generating fourth encryption information EK4 including the random number n3 and transmitting the fourth encryption information EK4 to the wireless terminal; The wireless terminal decrypts the fourth encryption information EK4 by using a secret key (K _{MS, PRI} ) of the wireless terminal to obtain the third random number n3, and obtains a second symmetric key (K _{AP, S2} ). Generating fifth encrypted information EK5 including the third random number n3 by using The access point side execution module: Receiving, by the access point, the fifth encrypted information EK5 including the third random number n3 from the wireless terminal (S106a); An access point decrypts the fifth encryption information EK5 using a second symmetric key K _{AP, S2} to obtain the third random number n3, and the third random number sent from the access point itself and the wireless terminal. Determining whether the transmitted third random number matches (S106b); WLAN security method further comprising. The method according to claim 1 or 2 or 4, The server is logically or physically divided into two servers, one of which distributes the first symmetric key K _{AP, S1} , and the other of the servers distributes the second symmetric key K _{AP, S2} . WLAN security method characterized in that. Receiving (S201), the server from the access point, first symmetric key (K _{AP, S1} ) request information used for encrypted communication between the access point and the server; Generating, by the server, first encryption information EK1 including the first symmetric key K _{AP, S1} using the public key K _{AP, PUB of} the access point, and transmitting the first encryption information EK1 to the access point (S202). )Wow; Receiving, by the server, second symmetric key (K _{AP, S2} ) request information used for encrypted communication in the wireless terminal period with the access point when the wireless terminal connects to the access point (S203); The public key of the second generate encrypted information (EK2), and a wireless terminal in which the server comprises a second symmetric key (K _{AP, S2)} using the first symmetric key _{(K AP, S1) (K} MS, PUB Generating third encryption information (EK3) including the second symmetric key (K _{AP, S2} ) and transmitting them to the access point (S204); Encrypting (S205) the server with the access point using the first symmetric key (K _{AP, S1} ); Wireless LAN security method comprising a server-side execution module comprising.