KR100866608B1 - System and Method for mutual authentication between a remote user and a server using a mobile device, Recording medium thereof - Google Patents

Abstract

A mutual authentication system, a method and a recording medium between a user and a server using a mobile device (for example, a general storage device such as a USB stick) are disclosed.

The present invention provides a system including a server and a mobile device, wherein the server comprises: a register configured to store first and second factors calculated using an ID and a password of the mobile device in the mobile device; If the value calculated using the first and second cipher texts received from the mobile device and the value calculated using the second factor, the first time stamp, and the ID received from the mobile device match, user authentication is performed. Accepting server authentication unit; And if the user authentication is accepted, generate a fourth passphrase of a secret value of the server using the third passphrase and a second time stamp that is a secret time of the fourth passphrase of the server, and generate the fourth passphrase. A server cipher text transmission unit for transmitting a cipher text to the mobile device, wherein the mobile device generates a password verifier using the first factor and the password when a login request is requested, and the first random number and the second random number in the mobile device. Generates a random number, calculates a first cipher text using the first random number and the second factor, and uses the first time stamp and the ID of the password verifier and the message authentication code value generation time of the mobile device. Generate a message authentication code value, and calculate a second passphrase using the message authentication code value and the password verifier and the first random number, Computing a third cipher text by using the second random number and the second factor, the server receives a login message consisting of the ID, the second argument, the first cipher text, the second cipher text, the third cipher text, and the first time stamp. Login request unit to send to; And a mobile device authentication unit for completing mutual authentication when the value calculated using the ID and the second time stamp matches the fourth cipher text.

According to the present invention, efficiency can be improved by using a general storage device or a mobile device that can be easily used by users, and the user's information is transferred to a general storage device or a mobile device by replacing a smart card with a high issuance cost and a low penetration rate. While storing, it can provide the same level of safety as in mutual authentication using smart cards that have tamper-resistant properties.

Description

System and Method for mutual authentication between a remote user and a server using a mobile device, Recording medium

1 is a block diagram of a mutual authentication system between a user and a server using a mobile device according to the present invention.

2 is a flowchart illustrating a mutual authentication method between a user and a server using a mobile device according to the present invention.

3 is a detailed flowchart of a process of storing the first and second factors of FIG. 2 in a mobile device.

4 illustrates an example of the process of FIG. 3.

5 illustrates an example of a process after the login request of FIG. 2.

The present invention relates to inter-personal authentication, and more particularly, to a mutual authentication system, a method and a recording medium between a user and a server using a mobile device (eg, a general storage device such as a USB stick).

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 entities is a technology in the field of information security and is the most basic and core technology in 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.

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 the conventional authentication method using a smart card, an authentication secret key of an arbitrary user is generated in a card issuing center and issued with an ID, a secret information, a password, and an authentication secret key, the information stored on the smart card. User authentication is performed using. At this time, the step of issuing the ID, password and authentication secret key is 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 ID to authenticate the authentication secret key. Calculating and issuing a smart card with an ID of the public information, a password of the secret information, and an authentication secret key. 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.

The conventional authentication method using a smart card is a mutual authentication technology using a smart card and a computer terminal, and has a characteristic of performing authentication by storing only one key on the server side without storing a secret key or password of each user. This solves the difficulty of increasing, decreasing and changing users.

However, the conventional authentication method stores a user's information by using a tamper-resistant storage device called a smart card, but when the device is changed to a device that does not provide safety like other general storage devices or mobile devices. It does not provide a lot of safety because it does not provide safety, and the production cost of the smart card is expensive, and there is a problem in that the use of the smart card reader requires a scart card reader due to its limitations in use.

Therefore, the first technical problem to be achieved by the present invention is to replace the smart card with a high issue cost and low penetration rate in mutual authentication using a smart card having tamper-resistant properties while storing the user's information in a general storage device or a mobile device. It is to provide a mutual authentication system between a user and a server using a mobile device that can provide the same level of safety, increase efficiency, and reduce the restriction of use because a separate reader is not required.

The second technical problem to be achieved by the present invention is to provide a mutual authentication method between a user and a server using a mobile device applied to a mutual authentication system between a user and a server using the mobile device.

A third technical object of the present invention is to provide a computer-readable recording medium recording a program for executing a mutual authentication method between a user and a server using a mobile device on a computer.

In order to achieve the first technical problem, the present invention provides a system comprising a server and a mobile device, wherein the server is the first and second factors calculated using the ID and password of the mobile device to the mobile device; A register to store; If the value calculated using the first and second cipher texts received from the mobile device and the value calculated using the second factor, the first time stamp, and the ID received from the mobile device match, user authentication is performed. Accepting server authentication unit; And if the user authentication is accepted, generate a fourth passphrase of a secret value of the server using the third passphrase and a second time stamp that is a secret time of the fourth passphrase of the server, and generate the fourth passphrase. A server cipher text transmission unit for transmitting a cipher text to the mobile device, wherein the mobile device generates a password verifier using the first factor and the password when a login request is requested, and the first random number and the second random number in the mobile device. Generates a random number, calculates a first cipher text using the first random number and the second factor, and uses the first time stamp and the ID of the password verifier and the message authentication code value generation time of the mobile device. Generate a message authentication code value, and calculate a second passphrase using the message authentication code value and the password verifier and the first random number, Computing a third cipher text by using the second random number and the second factor, the server receives a login message consisting of the ID, the second argument, the first cipher text, the second cipher text, the third cipher text, and the first time stamp. Login request unit to send to; And a mobile device authentication unit configured to complete mutual authentication when the value calculated using the ID and the second time stamp matches the fourth cipher text, and provides a mutual authentication system between the user and the server using the mobile device.

In order to achieve the second technical problem, the present invention comprises the steps of storing the first factor and the second factor calculated by using a random number selected from the mobile device ID and password of the mobile device; Generating a password verifier using the first factor and the password when a login request is made at the mobile device; Generating a first random number and a second random number in the mobile device, calculating a first cipher text using the first random number and the second factor, and generating a first time stamp that is a time for generating the password verifier and a message authentication code value And generating the message authentication code value of the mobile device using the ID, and calculating a second pass phrase using the message authentication code value and the password verifier and the first random number, wherein the second random number and the Calculating a third cipher text using the second argument; Transmitting a login message consisting of the ID, the second factor, the first passphrase, the second passphrase, the third passphrase, and the first time stamp to the server; Accepting user authentication if a value calculated using the first password text and a second password text and a value calculated using the second argument, the first time stamp, and the ID match; If the user authentication is accepted, a fourth cipher text of the server is generated by using the third cipher text and a second time stamp that is a secret time of the fourth cipher text, which is a secret value of the server, and the fourth cipher text is generated by the mobile terminal. Transmitting to the device; And if the value calculated using the ID and the second time stamp matches the fourth cipher text, accepting server authentication at the mobile device to complete mutual authentication. Provide a mutual authentication method.

In order to achieve the third technical problem, the present invention provides a computer-readable recording medium having recorded thereon a program for executing a mutual authentication method between a user and a server using a mobile device on a computer.

The present invention relates to a method for securely mutual authentication between a user and a server using a general storage device or a mobile device. The present invention enables mutual authentication using a general storage device such as USB or a mobile device.

The present invention utilizes the advantage of storing the user information of the authentication system using a smart card in the smart card, not the server, using the conventional storage device or mobile device instead of expensive and low penetration rate smart card to improve its efficiency. It provides a user-server mutual authentication technology that does not require a smart card reader.

In other words, as soon as the DB of the server is exposed, the attacker does not disguise the server as a legitimate client by using the client's password and enables mutual authentication using a general storage device or a mobile device, not a smart card with tamper-resistant properties. In order to improve user convenience and authentication efficiency.

In the present invention, even if the contents stored in the general storage device or the mobile are received by the attacker, it is impossible to impersonate the client without the user's password information, and likewise, it is impossible to impersonate the user without the server's secret information. In addition, this technology provides the advantages of the authentication system using a smart card, which provides security based on the tamper-resistant nature of the smart card.

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 various other forms, and the scope of the present invention is not limited to the embodiments described below.

1 is a block diagram of a mutual authentication system between a user and a server using a mobile device according to the present invention.

The mobile device 100 includes a registration request unit 101, a storage unit 102, a login request unit 103, and a mobile device authentication unit 104. Mobile devices include general storage devices such as USB sticks.

The registration request unit 101 selects an ID and a password and transmits them to the server 190. The registration requester 101 transmits the ID and password of the mobile device 100 to the server 190 through the secure channel.

The storage unit 102 stores the first factor and the second factor received from the server 190.

If there is a login request, the login request unit 103 generates a password verifier using the first factor and the password. And generating a first random number and a second random number in the mobile device, calculating a first passphrase using the first random number and the second factor, and generating a password verification message and a message authentication code value. The message authentication code value of the mobile device is generated using the time stamp and the ID, and a second password text is calculated using the message authentication code value and the password verifier and the first random number, and the second random number and The third cipher text is calculated using the second argument. The login request unit 103 transmits a login message composed of the ID, the second factor, the first passphrase, the second passphrase, the third passphrase, and the first time stamp to the server 190.

If the value calculated using the ID and the second time stamp matches the fourth cipher text, the mobile device authentication unit 104 completes mutual authentication.

The server 190 includes a register 191, a server authentication unit 192, and a server cipher text transmission unit 193.

The registration unit 191 calculates the first factor and the second factor by using the ID and password of the mobile device 100. The register 191 stores the calculated first and second factors in the mobile device 100. Preferably, the registration unit 191 may calculate the first factor and the second factor using an ID, a password, and any random number selected by the server 190 received from the mobile device 100. At this time, the registration unit 191 transmits the first factor and the second factor to the mobile device 100 through the secure channel, and deletes the first factor and the second factor from the server 190.

가 성립하면, 사용자 인증을 수락하도록 구성될 수 있다. 이때, 제1암호문이

, 제2암호문이

이고, 제1타임 스탬프가 T, 제2인자가

, 아이디가

, 해쉬함수가 H, 서버의 비밀키가

이며, p가 서버에서 선택된 값이다.The server authenticator 192 may use a value calculated using the first cipher text and the second cipher text received from the mobile device 100 and the second factor, the first time stamp, and the ID received from the mobile device 100. If the calculated values match, accept user authentication. Preferably, the server authentication unit 192 is

Can be configured to accept user authentication. At this time, the first passphrase

, The second cipher

The first time stamp is T and the second factor is

, Id

H, the hash function H, the server's secret key

P is the value selected on the server.

When the user authentication is accepted, the server cipher text transmission unit 193 generates the fourth cipher text, which is the secret value of the server, by using the third cipher text and the second time stamp that is the fourth cipher text generation time, which is the secret value of the server. do. The server cipher text transmission unit 193 transmits the generated fourth cipher text to the mobile device 100.

이고, 제2타임 스탬프가

이며, 해쉬함수가 h인 경우에, 제4암호문

을 연산하도록 구성될 수 있다. 이때, 모바일 기기 인증부(104)는

를 연산하고,

가 제4암호문과 일치하는지 판단하도록 구성될 수 있다. 이때,

가 제1인자 및 제2인자의 연산시에 서버에서 선택된 임의의 난수이고, b는 모바일 기기에서 선택된 제2난수이다.Preferably, the server cipher text transmission unit 193 is a third cipher text

The second time stamp

If the hash function is h, the fourth ciphertext

Can be configured to compute. At this time, the mobile device authentication unit 104

Is computed,

May be configured to determine whether is identical to the fourth cipher text. At this time,

Is any random number selected at the server in the calculation of the first and second factors, and b is the second random number selected at the mobile device.

2 is a flowchart illustrating a mutual authentication method between a user and a server using a mobile device according to the present invention.

First, the first and second factors calculated using the ID and password of the mobile device and any random number selected from the server are stored in the mobile device (step 210).

Next, the mobile device determines whether there is a login request (step 220). If there is no login request in this process, you can wait for the login request or terminate the whole process.

At this time, if there is a login request, a password verifier is generated using the first factor and the password, a first random number and a second random number are generated in the mobile device, and the first random number and the second argument are used. Computing a first passphrase, generating a message authentication code value of the mobile device using the first time stamp and the ID which is the time for generating the message authentication code value of the password verifier and the mobile device, and the message authentication code value And a second cipher text using the password verifier and the first random number, and a third cipher text using the second random number and the second factor (step 230). In addition, a login message including the ID, the second argument, the first passphrase, the second passphrase, the third passphrase, and the first time stamp of the mobile device is transmitted to the server (step 230).

Next, if the value calculated using the first passphrase and the second passphrase coincides with the value calculated using the second argument, the first time stamp, and the ID, the user authentication is accepted (step 240). This process (step 240) may include a step of rejecting user authentication if a value obtained by subtracting the time of receiving the login message from the first time stamp is greater than or equal to a threshold value.

If the user authentication is accepted, a fourth password, which is a secret value of the server, is generated by using the third password and a second time stamp, which is a secret time of the fourth password, which is the secret value of the server. In step 250, the mobile device transmits to the mobile device. At this time, if the user authentication is not accepted, all processes are terminated.

Next, it is determined whether the calculated value matches the fourth cipher text using the ID and the second time stamp (step 260). This process (step 260) may include determining that mutual authentication has failed if the value obtained by subtracting the second time stamp from the time of receiving the fourth cipher text is greater than or equal to a threshold value.

At this time, if the value calculated above matches the fourth cipher text, mutual authentication is completed (step 271). If not, it is determined that mutual authentication has failed (step 272).

3 is a detailed flowchart of a process (step 210) of storing the first and second factors of FIG. 2 in a mobile device.

First, the ID and password of the mobile device are transmitted to the server through the secure channel (step 311).

Next, the first factor and the second factor are calculated using the ID, password, and any random number selected in the server (step 312).

Next, the first and second factors are transmitted to the mobile device through the secure channel (step 313).

Finally, the first and second factors are stored in the storage space of the mobile device and the first and second factors are deleted from the server (step 314).

4 illustrates an example of the process of FIG. 3.

는 자신의 아이디

와 패스워드

를 선택하여 서버

에게 안전하게 전송한다.The process shown in FIG. 4 corresponds to a registration step. First, user

Has his id

And password

Select Server

Send securely to

∈ G 를 랜덤하게 선택하여

를 계산한다. 여기서,

mod p 이고

mod p 이다.Next, the server

∈ select G randomly

Calculate here,

mod p

mod p.

를 안전하게 전송한다. Next, the server is on your mobile device

Send it safely.

의 일반 저장장치는 그 값을 저장한다. Finally, when the user's mobile device receives a message from the server,

The general storage of is to store the value.

FIG. 5 illustrates an example of processes (steps 230-272) after the login request of FIG. 2.

The process of Figure 5 is largely divided into a login process and an authentication process.

The login process is as follows.

의 일반 저장장치는 다음의 연산을 수행한다.

The general storage of performs the following operations.

∈ G 를 선택한다. 다음,

mod p 와

mod p를 계산한다. 다음,

mod p,

mod p, 그리고

mod p 를 계산한다. 이때,

는 로긴 장치의 현재 타임 스탬프(timestamp) 정보로, 즉 패스워드 검증키

를 기반으로 생성한 메시지 인증 코드값

을 생성할 때의 시간 정보를 의미한다. 마지막으로, 인증을 위해서 서버에게 로그인 메시지

를 보낸다. First, random value

∈ Select G. next,

with mod p

Calculate mod p next,

mod p,

mod p, and

Calculate mod p At this time,

Is the current timestamp information for the login device, i.e. the password verification key.

Message authentication code value generated based on

Means time information when generating the. Finally, a login message to the server for authentication

Send it.

The certification process is as follows.

의 정당성을 확인한 후 정당하다면 인증과정을 수행한다. 다음, 서버는 상기 로그인 메시지를 수신한 타임 스탬프 값

을 이용하여 서버는

≥

라면 인증과정 수행을 거절한다. 다음,

인지 확인하여 등호가 성립하면, 서버는 사용자 인증을 수락하고 등호가 성립하지 않으면 사용자 인증을 거절한다. 다음, 서버는 상기 제 4 암호문을 생성할 때의 타임 스탬프 값

에 따라

를 계산하여 사용자 저장장치에 인증 메시지

를 보낸다. 다음, 메시지를 받은 사용자 저장장치는 로긴 장치의 상기 인증 메시지를 수신할 때의 타임 스탬프 값인

값을 이용하여

인지 확인하여 맞는다면 상호인증에 실패한다. 마지막으로, 사용자 저장장치는

를 계산하여

인지 확인하여 등호가 성립한다면 사용자와 서버간의 상호인증에 성공한다. 등호가 성립하지 않는다면 인증에 성공하지 못한다. first,

After verifying the validity of the validity, if necessary, the certification process is performed. Next, the server receives a timestamp value upon receiving the login message.

Using the server

≥

If not, it refuses to perform the authentication process. next,

If the equal sign is established by checking whether the equal sign is established, the server accepts user authentication and rejects user authentication if the equal sign is not established. Next, the server generates a timestamp value when generating the fourth cipher text.

Depending on the

The authentication message to the user storage device

Send it. Next, the user storage device receiving the message is a time stamp value when receiving the authentication message of the login device.

Using the value

If it is correct, mutual authentication fails. Finally, user storage is

By calculating

If the equal sign is established, the mutual authentication between the user and the server is successful. If the equal sign does not hold, authentication is not successful.

Preferably, a program for executing a mutual authentication method between a user and a server using a mobile device of the present invention on a computer may be recorded and provided 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, efficiency can be improved by using a general storage device or a mobile device that can be easily used by users, and the user's information is generally stored by replacing a smart card with a high issuance cost and a low penetration rate. It can provide the same level of safety as that of mutual authentication using smart cards with tamper-resistant properties while being stored in devices or mobile devices.

Claims (12)

Storing the first and second factors calculated using the ID and password of the mobile device and any random number selected by the server on the mobile device; Generating a password verifier using the first factor and the password when a login request is made at the mobile device; Generating a first random number and a second random number in the mobile device, calculating a first cipher text using the first random number and the second factor, and generating a first time stamp that is a time for generating the password verifier and a message authentication code value And generating the message authentication code value of the mobile device using the ID, and calculating a second pass phrase using the message authentication code value and the password verifier and the first random number, wherein the second random number and the Calculating a third cipher text using the second argument; Transmitting a login message consisting of the ID, the second factor, the first passphrase, the second passphrase, the third passphrase, and the first time stamp to the server; Accepting user authentication if a value calculated using the first password text and a second password text and a value calculated using the second argument, the first time stamp, and the ID match; If the user authentication is accepted, a fourth cipher text of the server is generated by using the third cipher text and a second time stamp that is a secret time of the fourth cipher text, which is a secret value of the server, and the fourth cipher text is generated by the mobile terminal. Transmitting to the device; And If the value calculated using the ID and the second time stamp matches the fourth cipher text, accepting server authentication by the mobile device, and completing mutual authentication; Authentication method. The method of claim 1, Saving to the mobile device Transmitting the ID and password of the mobile device to a server through a secure channel; Calculating a first factor and a second factor using the ID, password, and any random number selected by the server, and transmitting the first and second factors to the mobile device through a secure channel; And Storing the first factor and the second factor in a storage space of the mobile device, and deleting the first factor and the second factor from the server. Authentication method. The method of claim 1, Accepting the user authentication And if the value obtained by subtracting the time for receiving the login message from the first time stamp is greater than or equal to a threshold value, rejecting user authentication. The method of claim 1, Completing the mutual authentication is And determining that mutual authentication has failed if the value obtained by subtracting the second time stamp from the time of receiving the fourth cipher text is equal to or greater than a threshold value. The method of claim 1, Accepting the user authentication The first passphrase

, The second cipher

Where the first time stamp is T and the second factor is

, The id is

, Hash function H, the secret key of the server

If p is a value selected in the server,

If is established, mutual authentication between the user and the server using a mobile device, characterized in that for accepting the user authentication. The method of claim 1, Transmitting the fourth cipher text to the mobile device The third ciphertext

Wherein the second time stamp is

H, the hash function h,

If is, the fourth passphrase

Computing the mutual authentication method between the user and the server using a mobile device, characterized in that it comprises a step. The method of claim 1, Completing the mutual authentication is The second time stamp is

, The id is

H is the hash function, and the server's private key

Is,

And p are values selected in the calculation of the first and second factors, and the second random number is b,

Calculating a; And remind

And determining whether the fourth password is identical to the fourth cipher text. A computer-readable recording medium having recorded thereon a program for executing the method of claim 1 on a computer. In a system comprising a server and a mobile device, The server is A register configured to store the first and second factors calculated using the ID and password of the mobile device in the mobile device; If the value calculated using the first and second cipher texts received from the mobile device and the value calculated using the second factor, the first time stamp, and the ID received from the mobile device match, user authentication is performed. Accepting server authentication unit; And If the user authentication is accepted, a fourth password, which is the secret value of the server, is generated by using the third password and a second time stamp, which is a secret time of the fourth password, which is the secret value of the server. Includes a server cipher text transmission unit for transmitting to the mobile device, The mobile device If there is a login request, a password verifier is generated using the first factor and the password, a first random number and a second random number are generated in the mobile device, and a first random number is generated using the first random number and the second argument. Computes a cipher text, and generates a message authentication code value of the mobile device using the first time stamp and the ID of the password verifier and the message authentication code value generation time, and the message verification code value and the password verifier Computing a second cipher text using the first random number, and calculating a third cipher text using the second random number and the second factor, the ID, the second factor, the first cipher text, the second cipher text, the first cipher text. A login request unit for transmitting a login message consisting of a three-password and a first time stamp to the server; And And a mobile device authentication unit for completing mutual authentication when a value calculated using the ID and the second time stamp matches the fourth cipher text. The method of claim 9, The register Calculate a first factor and a second factor using an ID, a password received from the mobile device, and any random number selected from the server, and transmit the first and second factors to the mobile device through a secure channel. And deleting the first and second factors, The mobile device A registration request unit for transmitting the ID and password of the mobile device to a server through a secure channel; And And a storage unit for storing the first factor and the second factor. The method of claim 9, The server authentication unit The first passphrase

, The second cipher

Where the first time stamp is T and the second factor is

, The id is

, Hash function H, the secret key of the server

If p is a value selected in the server,

Is established, the mutual authentication system between the user and the server using the mobile device, characterized in that for accepting the user authentication. The method of claim 11, The server cipher text transmission unit The third ciphertext

Wherein the second time stamp is

And if the hash function is h, the fourth ciphertext

Is computed, The mobile device authentication unit

Is an arbitrary random number selected at the time of operation of the first and second factors, and the second random number is b,

And calculate

And a user authentication system and a server using the mobile device.

Images