KR20030037145A - the method and the system for passward based key change - Google Patents

Abstract

PURPOSE: A method and a system for exchanging a key by using a password are provided to reduce the traffic on a network and communication errors by reducing the number of key exchange messages between systems and the amount of calculation of a client. CONSTITUTION: A client(10) is formed with a key exchange module initialization management portion(11) for managing parameters and functions, a key exchange coefficient generation portion(12) for generating coefficients for key exchange protocols, a key exchange calculation portion(13) for generating and processing a key exchange protocol message, an encoding process portion(14) for performing an encoding process, a key exchange registration portion(15) for processing a process for registering the key exchange, and a transmission portion(16) performs a data communication process with a server(30) through a network(20). The server(30) is formed with a key exchange module initialization management portion(31) for managing the parameters and the functions, a key exchange calculation portion(32) for generating a key exchange message, an encoding process portion(33) for protecting the key exchange message, a key exchange registration portion(34) for decoding the encoded data, a storage portion(35) for storing the decoded data, and a transmission portion(36) for performing a data communication process with the client(10) through the network(20).

Description

Password-based key exchange method and the system {the method and the system for passward based key change}

The present invention relates to a password-based key exchange method and a system thereof, and more particularly, to applying an Internet key exchange service technology using a password to provide an optimal security service in the Internet without reducing the security strength between the client and the server. The present invention relates to a password-based key exchange method and system for generating an authenticated shared key while reducing the amount of computation and the number of message exchanges between systems.

In general, the password key exchange method generates a mutually authenticated shared key between a client and a server system by inputting only password information that can be stored by a user into the client system. In the case of this method, a method of allowing information on a password used for mutual authentication in a client and server system to be set differently is widely studied. At this time, the password-related information of the server system is easily generated through the password, but conversely, it is very difficult to infer the password information using the information.

The method of exchanging keys between client and server based on this setting is very important to how to exchange key material efficiently, to reduce the number of message exchanges and maintain security strength.

In particular, it is very important to design the client system so that the calculation amount of the client system is small during the key exchange process since the client system generally has a low computational power. An example of this is a mobile communication system.

The increase in the number of message exchanges leads to network performance degradation due to increased traffic, and can be affected by various obstacles and effects due to communication delays. On the other hand, in terms of the efficiency of the system, security strength and efficiency are in conflict with each other, so that the increase of security leads to the weakening of the efficiency.

Particularly, in the mobile communication system, the computational power of the mobile terminal (client) is small, so the problem of how to reduce the computational amount of the mobile terminal is very important, and the computational amount of the client in an environment in which the security requirements are increased due to the mobility of the system. There is a need for a technical method to reduce the number of exchange messages between and systems.

SUMMARY OF THE INVENTION The present invention has been made by such a technical necessity, and a password-based key exchange method for increasing the efficiency of the entire system by reducing the number of key exchange messages between systems and reducing the amount of computation of clients to reduce network traffic and reduce communication errors. The purpose is to provide the system.

1 is a system block diagram for performing a password-based key exchange method according to the present invention.

FIG. 2 is a flow chart of the procedure for registering key exchange counts at the client shown in FIG. 1; FIG.

3 is a flow chart of a procedure for registering key exchange coefficients in the server shown in FIG.

4 is a detailed flowchart of performing a key exchange protocol at the client shown in FIG.

5 is a detailed flowchart of performing a key exchange protocol in the server shown in FIG.

* Explanation of symbols for the main parts of the drawings *

10: client 11: key exchange module initialization management unit

12: key exchange coefficient generation unit 13: key exchange operation unit

14: encryption processing unit 15: key exchange registration unit

16: transmission unit 20: network

30: server 31: key exchange module initialization management unit

32: key exchange operation unit 33: encryption processing unit

34: key exchange registration unit 35: storage unit

36: transmission unit

According to the present invention for achieving the above object, if the client generates system parameters used for key exchange using password information, and transmits and stores the user's password information and arbitrary key material to the server, the server transmits them from the client. Extract key information from information to generate and store shared key.If there is an authentication request from the client, the server sends its own key information and authentication information to the client to authenticate the server to the client, generate a shared key, and send the client to the server. A key exchange for authentication is performed by generating and sending a message to authenticate the ID.

According to one aspect of the password-based key exchange system according to the present invention, in the system for exchanging password-based key information via the network, the system parameters used for key exchange and the user ID and password information and information necessary for key exchange Is registered by sending it through the network, and when there is a user authentication request from the user, the authentication information input from the user is transmitted through the network, and accordingly, the shared key and the key exchange required for authentication by the authentication information received through the network Receives and stores the message that generates the message and performs the key exchange, and the system parameter information used for the key exchange transmitted from the client through the network, and, when requested by the client, sends the key exchange message for the client's authentication. Generate the client And a server that performs key exchange.

Further, according to one aspect of a key exchange method performed in a server exchanging a key for password authentication with a client over a network according to the present invention, a key exchange method of a server exchanging a key for password authentication with a client over a network In the step of receiving, decrypting and decrypting an encrypted registration message transmitted from a client through a network, extracting and storing ID and key exchange coefficient information, and receiving a transmission message for key exchange registration from the client, Retrieving the corresponding key exchange coefficient information, extracting the key material information of the client accordingly, calculating the shared key, the key material and the information for authentication using the random number selected by the client, and transmitting the information to the client; Receive the information sent for key exchange and keep track of its own authentication information. Comparing with the client authentication information received from the client to generate a key exchange success message if the same.

In addition, according to one aspect of the recording medium for performing the key exchange method of the server according to the present invention, in order to perform a key exchange method of the server for exchanging a key for password authentication with the client over a network, A program of instructions that can be executed by a program is tangibly embodied, and in a recording medium that can be read by a digital processing apparatus, an encrypted registration message transmitted from a client through a network is received, decrypted, and interpreted to identify an ID and a key. Extracting and storing the exchange coefficient information, and when receiving the transmission message for the key exchange registration from the client, retrieve the corresponding key exchange coefficient information, extract the key material information of the client accordingly, and select a random number selected by the client. Calculate information for shared key, key material and authentication using If the receiving step and the information transmitted to the key exchange from the client to transmit the client calculates its own authentication information, the same as compared with client authentication information received from the client includes the step of generating a successful key exchange messages.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, the symbols to be used in the following description are defined as follows.

a | b: a divides b

A || B: concatenation of data A and B

PWD: Password

h: one-way abbreviated function, such as SHA1, MD5

p is a cryptographically safe fractional number (increasingly used in general terms, depending on the cryptographic algorithms and computational power of computers)

q: q | A cryptographically safe fractional number that satisfies p-1 (increasingly used in general terms, depending on the cryptographic algorithms and computational power of computers to date)

S: base used for the modular exponentiation calculation of key exchange in the present invention

v: Verifier that is generated through a password and will be used for client authentication by the server (also called verifier in password-based key exchange protocol in English).

In the above symbols, S and v are calculated by the following equations (1) and (2).

S = h (PWD) ^{(p-1) / q} mod p (where 1 <S <p)

v = S ^-PWD mod p

1 is a block diagram illustrating a configuration of a system for performing password based key exchange according to the present invention. Referring to FIG. 1, the password-based key exchange system of the present invention includes a client 10 and a server 30 that performs key exchange by receiving key exchange information from the client 10 through the network 20. .

The client 10 includes a key exchange module initialization management unit 11, a key exchange coefficient generation unit 12, a key exchange operation unit 13, an encryption processing unit 14, a key exchange registration unit 15, and a transmission unit. The server 30 may include a key exchange module initialization management unit 31, a key exchange operation unit 32, an encryption processing unit 33, a key exchange registration unit 34, and a storage unit. The unit 35 and the transmission unit 36 may be configured.

First, the configuration of the client 10 will be described.

The key exchange module initialization management unit 11 manages parameters and functions initially set for key exchange in the client 10. In other words, we have cryptographically safe fractional numbers p, q, and published one-way shorthand functions h as system coefficients and library functions.

The key exchange coefficient generation unit 12 generates coefficients used in the key exchange protocol. That is, S, v, and ID information are generated as key exchange coefficients by using the key exchange module initialization management unit 11 and an external interface capable of receiving an ID and a password from the user.

When the registration process for key exchange is completed, the key exchange operation unit 13 generates and processes a key exchange protocol message. The encryption processing unit 14 performs encryption processing to protect the key exchange registration message to support secret communication of the key exchange registration unit 15.

The key exchange registration unit 15 processes the key exchange registration process. That is, the client 10 and the server 30 support ID, S, and v secretly send and receive registration. The transmission unit 16 performs data transmission and reception with the server.

Now, let's look at the configuration of the server (30).

The key exchange module initialization manager 31 manages parameters and functions initially set for key exchange in the server 30. In other words, we have cryptographically safe fractional numbers p, q, and published one-way shorthand functions h as system coefficients and library functions.

The key exchange operation unit 32 inquires IDs, S, and v stored in the storage unit 35 to generate a key exchange message, and counts p, q and the one-way abbreviated function h released from the key exchange module initialization management unit 31. , f is provided, generates a key exchange protocol message, interprets the key exchange message received from the client 10, and performs arithmetic processing accordingly.

The encryption processing unit 33 processes the encryption or decryption to protect the key exchange message generated for transmission to the client 10, or to decrypt the key exchange registration message encrypted and transmitted from the client 10.

The key exchange registration unit 34 sends the encrypted ID, S, v received through the transmission unit 36 to the encryption processing unit 33 to perform decryption, and the ID, S, v decrypted from the encryption processing unit 33. After receiving and interpreting the ID, S, v is stored in the storage unit 35 performs registration.

The storage unit 35 registers and manages IDs, S, v in the server when the ID, S, v is received by the database management means key exchange registration unit 34 of the server that stores and manages the registered client information.

The transmitting unit 36 transmits and receives data of the client 10 through the network 20, receives an encrypted registration message of the client transmitted from the client 10, and transmits the encrypted registration message to the key exchange registration unit 34. It performs a function of transmitting a message to the client (10).

2 is a flowchart of a key exchange registration process in a client according to the present invention.

Let's look at the key exchange registration process in the client with reference to FIG. First, the key exchange coefficient generation unit 12 receives an ID and a password from the user (S1), receives the coefficients p, q and the function h, f information from the key exchange module initialization management unit 11 according to equation (1). S is obtained (S2), and v is calculated from S by Equation 2 (S3). S and v obtained in this way are concatenated with the ID input from the user. [ID || S || v] is generated (S4) and sent to the key exchange registration unit 15. The key exchange registration unit 15 receives the encryption and decryption support from the encryption processing unit 14, encrypts the ID, S, and v received from the key exchange coefficient generation unit 12 (S4) and sends it to the transmission unit 16. In the transmission unit 16, the encrypted [ID || S || v] information is transmitted to the server 30 (S6). After receiving the registration completion message from the server 30 (S7), the key exchange registration unit 15 discards the v value and completes the registration process (S8).

The calculated S value can also be discarded to enhance the security of the client system, in which case the S value must be recalculated at each key exchange. Otherwise, S may be stored in the key exchange operation unit 13 and continue to be used for key exchange.

3 is a flowchart of a key exchange registration process in a server according to the present invention. Let's look at the registration process of the server with reference to FIG.

The transmission unit 36 of the server receives the encrypted registration message of the client transmitted through the network 20 and delivers it to the key exchange registration unit 34. The key exchange registration unit 34 receives the encrypted ID, S, v received through the transmission unit 36 and decrypts it using the encryption processing unit 33 (S12) and interprets the decrypted ID, S, v ( S13) The interpreted ID, S, v are stored in the storage unit 35 (S14), and a registration completion message is generated. The transmitter 36 transmits the registration completion message to the client 10 via the network 20 (S15). The registration information is then queried when the key exchange process begins.

4 shows a flow diagram for performing a key exchange protocol in a client in accordance with the present invention.

Referring to Figure 4 will be described the operation of the key exchange protocol of the present invention. When the ID and the PWD are input from the user (S101), or a signal for instructing the start of the key exchange protocol is generated, the key exchange coefficient generator 12 generates key exchange coefficients, and the ID, S, Pass PWD. The key exchange operation unit 13 selects an arbitrary number x and r of 0 <x <q and 0 <r <q through the ID and PWD of the user transferred from the key exchange coefficient generation unit 12. E and t are calculated by Equation 4 (S102, S103).

e = S ^xr mod p

t = r + ePWD mod q

When the calculation is completed, the key exchange operation unit 13 connects the generated e and t with the set ID and transmits the registration to the server system through the transmission unit 16. The server 30 receives this transmission message and stores the key exchange as data.

On the other hand, when receiving a message from the server through the transmission unit 16 using the received message Y to calculate its own shared key Kc by the following equation (5) (S106).

Kc = Y ^x = S ^xy mod p

After calculating Kc, the key exchange operation unit 13 calculates h (Kc, e, t) using this value and compares it with the value h (Ks, e, t) obtained from the message sent from the server 30. (S108). If h (Kc, e, t) = h (Ks, e, t), server authentication is successful, and the client calculates h (Kc, Y) and sends it to the server (S109). If h (Kc, e, t) and h (Ks, e, t) are not equal, the authentication is failed and the key exchange process is stopped (S110).

5 is a flowchart illustrating a key exchange protocol performed in a server according to the present invention. Referring to FIG. 5, a process of performing a key exchange protocol in a server will be described.

The server performs a process of receiving and interpreting a message transmitted from the client 10 through the network 20 (S201). Reception of the message transmitted from the client 10 is made in the transmission unit 36. The content of the received message includes encrypted ID, S, v information. The transmission unit 36 transmits this encrypted information to the key exchange registration unit 34. The key exchange registration unit 34 stores its ID, S, and v information in the storage unit 35. The key exchange operation unit 32 determines whether the transmitted message is the first message for key exchange (S202). If it is the first message for the key exchange, the storage unit 35 inquires the database for v and S corresponding to the ID received from the client 10 (S203). If the storage unit 35 finds the corresponding v and S (S204), the client has previously received and stored the [ID || e || t] is read together to calculate S ^x mod p by the following equation (6) (S205).

S ^x = S ^t v ^e e mod p

When Sx mod p is calculated, an arbitrary number y having 0 <y <q is selected and the shared key Ks is calculated by Equation 7 (S206).

Ks = (S ^x ) ^y = S ^xy mod p

After calculating the shared key Ks, its own key material Y is generated using Equation 8 using y (S207).

Y = S ^y mod p

When Y and Ks are calculated, the key exchange operation unit 32 calculates h (Ks, e, t) using the one-way abbreviation function h (S208), and concatenates this value with Y to transmit the client through the transmission unit 36. It transmits to 10 (S209).

Meanwhile, as a result of receiving the key exchange message from the client 10 and determining whether the key exchange message is the first message (S201), in the case of the last message, h (Ks, Y) is similarly calculated using its own Ks (S210). This value is compared with h (Kc, Y) (S211). If the value is the same, the key exchange operation unit 32 may authenticate the client, so that the key exchange process between the client and the server may be completed successfully, thereby generating a key exchange success message (S212). Generates a key exchange failure message (S213).

According to the present invention, the number of message exchanges is reduced by performing key exchange between the client and the server system more efficiently than the conventional method, thereby reducing the effects of communication errors and network delays. It can be effectively applied to such a system.

Claims (9)

In the system for exchanging password-based key information through the network, The system parameters used for the key exchange, user ID and password information, and information necessary for key exchange are transmitted and registered through the network, and when a user authentication request is received from the user, authentication information input from the user through the network is registered. A client for performing key exchange by generating a key exchange message for sharing key and authentication based on the authentication information received through the network accordingly; A server that receives and stores system parameter information used for key exchange transmitted from a client through a network, and generates a key exchange message for authentication of the client when the client requests an authentication, and performs a key exchange with the client. Password-based key exchange system comprising a. The method of claim 1, wherein the client, A key exchange coefficient generation unit for generating system parameters used for key exchange using user ID and password information; A key exchange registration unit for generating key exchange registration information for pre-registering user ID and password information and information necessary for key exchange by the system parameters generated in the key exchange coefficient generation unit; A password-based key exchange system including a key exchange operation unit for authenticating a server by using the authentication information received from the server, generating a shared key, and generating and exchanging a key exchange message necessary for authentication at the server. . The method of claim 1, wherein the server, A key exchange registration unit that receives system parameter information used for a key exchange generated by using a user ID and password information from a client through a network and registers the information for key exchange; Extract the key material of the client from the system parameter information to extract the shared key, generate its own authentication information to be sent to the client, and generate and calculate a key exchange message for authentication of the client by the key exchange message sent from the client. Password-based key exchange system including a key exchange operation to perform the. In a key exchange method of a client exchanging a key for password authentication with a server over a network, Receiving an ID and a password from a user and generating key exchange coefficients S and v by Equations 1 and 2; Concatenate the S, v and the ID to be used in the key exchange operation [ID || S || v], encrypting the data, and transmitting it to the server to request key registration; Selecting the random numbers x and r having 0 <x <q and 0 <r <q through receiving an ID and a password from a user, and calculating e and t by Equations 3 and 4; The messages e and t calculated by the random number x, r and the password PWD and the key exchange coefficient S are concatenated together with their IDs to [ID || e || generating t] and transmitting it to a server through a network for key exchange registration; Receiving the shared key Ks and key material Y and the abbreviated value h (Ks, e, t) information for the key exchange from the server to calculate the shared keys Kc and h (Kc, e, t) by Equation 5, Password-based key performing the step of completing key exchange by calculating the abbreviated function value h (Kc, Y) and transmitting it to the server if it is equal to the message h (Ks, e, t) received from the server. Exchange method. [Equation 1] S = h (PWD) ^{(p-1) / q} mod p (where 1 <S <p) [Equation 2] v = S ^-PWD mod p [Equation 3] e = S ^xr mod p [Equation 4] t = r + ePWD mod q [Equation 5] Kc = Y ^x = S ^xy mod p (Where p is the cryptographically safe prime number, q: q | the cryptographically safe prime number that satisfies p-1, S is the base used for the modular exponentiation of key exchange, v: Verifiers generated via password and used for client authentication by the server) The method according to claim 4, wherein the key exchange coefficient S value is q | A password-based key exchange method, wherein p is 1 and q is also generated using a one-way abbreviation function that selects p, which is also a safe prime number, so that the rank of S on the prime p becomes q. In the server key exchange method for exchanging keys for password authentication with the client over a network, Receiving, decrypting and interpreting an encrypted registration message transmitted from a client through a network, extracting and storing ID and key exchange coefficient information; When receiving the transmission message for registering the key exchange from the client, the corresponding key exchange coefficient information is retrieved, and accordingly, the key material information of the client is extracted, and the shared key, key material, and authentication are performed using the random number selected by the client. Calculating and transmitting the information to the client; And receiving the information transmitted for the key exchange from the client, calculating its own authentication information, and comparing the client authentication information received from the client to generate a key exchange success message. The method of claim 6, wherein the transmitting to the client comprises: Retrieving corresponding key exchange coefficient information S and v when receiving a transmission message for registering a key exchange from a client; If the corresponding S and v are found, the previously stored [ID || e || reading t] together and performing an operation according to Equation 6 to calculate S ^x mod p, Selecting an arbitrary number y having 0 <y <q using S ^x mod p and calculating the shared key Ks by Equation 7, After calculating the shared key Ks, using the y to generate the own key material Y by the equation (8), When Y and Ks are calculated, calculating a h (Ks, e, t) using a one-way abbreviation function h, and concatenating these values with Y to transmit them to the client. [Equation 6] S ^x = S ^t v ^e e mod p [Equation 7] Ks = (S ^x ) ^y = S ^xy mod p [Equation 8] Y = S ^y mod p (Where p is a cryptographically safe fractional number, q: q | Verifier generated via password and used by the server for client authentication, e = S ^xr mod p, t = r + e Number) In order to perform a key exchange method of a client exchanging a key for password authentication with a server over a network, a program of instructions that can be executed by the digital processing apparatus is tangibly implemented, and can be read by the digital processing apparatus. In the recording medium, Receiving an ID and a password from a user and generating key exchange coefficients S and v by Equations 1 and 2; Concatenate the S, v and the ID to be used in the key exchange operation [ID || S || v] requesting the key registration by generating, encrypting and transmitting to the server; Selecting the random numbers x and r having 0 <x <q and 0 <r <q through receiving an ID and a password from a user, and calculating e and t by Equations 3 and 4; The messages e and t calculated by the random number x, r and the password PWD and the key exchange coefficient S are concatenated together with their IDs to [ID || e || generating t] and transmitting it to a server through a network for key exchange registration; Receiving the shared key Ks and key material Y and the abbreviated value h (Ks, e, t) information for the key exchange from the server to calculate the shared keys Kc and h (Kc, e, t) by Equation 5, And determining if the message h (Ks, e, t) received from the server is the same and calculating the abbreviated function value h (Kc, Y) to the server to complete the key exchange. [Equation 1] S = h (PWD) ^{(p-1) / q} mod p (where 1 <S <p) [Equation 2] v = S ^-PWD mod p [Equation 3] e = S ^xr mod p [Equation 4] t = r + ePWD mod q [Equation 5] Kc = Y ^x = S ^xy mod p (Where p is the cryptographically safe prime number, q: q | the cryptographically safe prime number that satisfies p-1, S is the base used for the modular exponentiation of key exchange, v: Verifiers generated via password and used for client authentication by the server) In order to perform a key exchange method of a server exchanging keys for password authentication with a client through a network, a program of instructions that can be executed by the digital processing apparatus is tangibly implemented, and can be read by the digital processing apparatus. In the recording medium, Receiving, decrypting and interpreting an encrypted registration message transmitted from a client through a network, extracting and storing ID and key exchange coefficient information; When receiving the transmission message for registering the key exchange from the client, the corresponding key exchange coefficient information is retrieved, and accordingly, the key material information of the client is extracted, and the shared key, key material, and authentication are performed using the random number selected by the client. Calculating and transmitting the information to the client; And receiving the information transmitted for the key exchange from the client, calculating its own authentication information, and comparing the client authentication information received from the client to generate a key exchange success message.