WO2017222183A1

WO2017222183A1 - Method for processing transaction approval and card issuer server

Info

Publication number: WO2017222183A1
Application number: PCT/KR2017/004984
Authority: WO
Inventors: 박상춘; 김창열
Original assignee: 비씨카드(주)
Priority date: 2016-06-20
Filing date: 2017-05-12
Publication date: 2017-12-28
Also published as: KR101896455B1; KR101872278B1; KR101872279B1; KR101766597B1; KR20170142829A; WO2017222178A1; KR20170142830A; KR20170142831A; KR20170142822A; WO2017222177A1; WO2017222170A1; KR101766599B1; WO2017222172A1; KR101857067B1; KR101756594B1; KR101756598B1; KR101766598B1; KR101757125B1; KR20170142821A; WO2017222175A1

Abstract

A method for processing transaction approval in a card issuer server, according to an embodiment of the present invention, comprises the steps of: (a) generating and transmitting, upon completing the authentication of an affiliate terminal, a first payment key to the affiliate terminal; (b) receiving, from the affiliate terminal, a transaction approval request including card information encrypted with any one encryption key selected from among a set of encryption keys generated on the basis of the first payment key; (c) generating the set of encryption keys on the basis of the first payment key, obtaining an encryption key corresponding to a serial number of the selected encryption key in the generated set of encryption keys, and decrypting the encrypted card information with the obtained encryption key; and (d) performing transaction approval using the decrypted card information, and transmitting a result of the transaction approval to the affiliate terminal.

Description

Transaction approval processing method and card issuer server

The present invention relates to a transaction approval processing method and a card issuer server, and more particularly, to a transaction approval processing method and a credit card company server which decrypt card information encrypted with an encryption key corresponding to a serial number of an encryption key among encryption key sets generated based on a payment key, And a card issuer server, which performs transaction approval through encryption between terminals in a direct authorization process.

Card companies provide various card services to increase card usage, and the number of transactions between credit card companies and merchants is gradually increasing due to increased card usage.

When a transaction between a credit card company and a merchant is approved, a transaction approval procedure is performed through VAN, which acts as an intermediary. The credit card company and the merchant pay a predetermined fee to VAN in accordance with the transaction approval.

However, due to the increase in the number of transaction approvals and the amount of money, the amount of commissions that card companies and merchants need to pay to VAN is increasing, and there is a problem in that both credit card companies and merchants are burdened with commissions.

Therefore, there is a growing demand for credit card companies and merchants to deal with VANs without authorization, and it is imperative to secure security when approving transactions through direct approval.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the related art described above, and it is an object of the present invention to provide a method and apparatus for decrypting card information encrypted with an encryption key corresponding to a serial number of an encryption key, And a transaction acceptance processing method and a card issuer server which perform transaction approval through encryption between terminals at the time of direct approval processing.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood from the following description.

According to another aspect of the present invention, there is provided a method for processing transaction approval in a card issuer server, the method comprising the steps of: (a) generating a first payment key upon completion of authentication of the merchant terminal, Transmitting to the terminal; (b) receiving, from the merchant terminal, a transaction approval request including card information encrypted with any one of the encryption keys selected from among the encryption key sets generated based on the first payment key; (c) generating the encryption key set based on the first payment key, obtaining an encryption key corresponding to the serial number of the selected encryption key in the generated encryption key set, and transmitting the encrypted Decrypting the card information; And (d) performing transaction approval using the decrypted card information, and transmitting a transaction approval result to the merchant terminal.

The step (c) may include generating a second payment key with the first payment key and generating the encryption key set based on the generated second payment key.

The encryption key set may be generated on the basis of the second payment key in the card company server and the merchant terminal.

The first payment key may be deleted when the second payment key is generated.

The encryption key set may include a plurality of one-time encryption keys each of which can be used only once.

The encrypted card information may be encrypted from the time when the card is recognized by the merchant terminal to the transmission period to the card issuer server.

The serial number of the encryption key may include special data including key identification information used for encryption, identification information of the merchant terminal, and transaction count.

According to another aspect of the present invention, there is provided a credit card server for processing transaction approval, the method comprising: generating a first payment key when authentication of an affiliate terminal is completed; A key generation unit for generating a set of encryption keys; A key transmission unit for transmitting the generated first payment key to the merchant terminal; An approval request receiver for receiving a transaction approval request from the merchant terminal including card information encrypted with any one of the encryption keys selected from among the encryption key sets generated based on the first payment key; A decryption unit that obtains an encryption key corresponding to a serial number of the selected encryption key among the generated encryption key sets and decrypts the encrypted card information with the obtained encryption key; And a transaction admission unit for performing transaction approval using the decrypted card information and transmitting a transaction approval result to the affiliate terminal.

The key generation unit may generate a second payment key using the first payment key and generate the encryption key set based on the generated second payment key.

The encryption key set may be generated based on the second payment key in the key generation unit and the merchant terminal.

The first payment key may be deleted when the second payment key is generated.

According to an embodiment of the present invention, a payment approval process can be performed without a VAN company through a direct approval process between a merchant terminal and a card issuer server, so that a transaction fee paid to a VAN company can be reduced.

In addition, according to an embodiment of the present invention, end-to-end encryption (E2E) of the merchant terminal and the card issuing server can be performed to secure security in transaction approval through direct approval.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a diagram illustrating a billing key management system according to an embodiment of the present invention.

2 is a block diagram illustrating the configuration of a card issuer server according to an embodiment of the present invention.

3 is a diagram showing an encryption range of card information according to an embodiment of the present invention.

4 is a diagram illustrating a key exchange process for authentication and encryption processing of an affiliate terminal.

5 is a diagram illustrating a process of encrypting and decrypting card information according to an embodiment of the present invention

FIG. 6 is a diagram illustrating a process of performing end-to-end encryption (E2E) for a direct authorization process between an affiliate terminal and a card issuer server according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as " comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

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

Referring to FIG. 1, a payment key management system according to an embodiment of the present invention may include a merchant terminal 100 and a card issuer server 200 that can communicate with each other.

First, the communication network can be configured without regard to its communication mode such as wired and wireless. A local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), and the like.

The merchant terminal 100 may be a POS terminal, which is installed in an affiliate store registered as an affiliated merchant of a merchant operating a card issuer server 200. [

The merchant terminal 100 may send a payment approval request to the card issuer server 200. For example, when the card payment approval request is made, the merchant terminal 100 transmits a payment approval request including the card information to the card issuer server 200, Lt; / RTI >

Specifically, the merchant terminal 100 recognizes the plastic card information through a MS (Magnetic Strip), an IC (Integrated Circuit) chip or the like in the plastic card presented by the customer, or displays the barcode, QR code And transmits the payment approval request including the recognized card information to the card issuer server 200. The card issuer server 200 can receive the payment approval request including the recognized card information.

As described above, when a payment approval request is made at the merchant terminal 100, a payment approval request may be made using a plastic card and a mobile card. However, the payment approval request may be made using various payment means such as an NFC tag or a virtual card Approval requests may be made.

In addition, a payment approval request using a card can be made online through an Internet site provided by a merchant.

Card issuer server 200 can store merchant information, customer information, and the like in a database and manage it.

The merchant information may include information related to an affiliate shop, such as the name of a merchant, a business type, and information related to the affiliated shop terminal 100, such as location information and identification information of the affiliate shop terminal 100 installed in the merchant store May also be included.

The customer information is information registered when the customer issues a card, and may include information related to the customer such as a customer card, an account linked to the customer card, a customer contact, and the like.

The card issuer server 200 can authenticate the franchisee terminal 100 based on the franchisee information. When the authentication of the franchisee terminal 100 is completed, the card issuer server 200 generates a first payment key, Lt; / RTI >

When the credit card terminal 100 generates an encryption key set based on the first payment key received from the credit card company server 200 and encrypts the card information with any one of the encryption keys selected from the generated encryption key sets, May receive a transaction approval request containing the encrypted card information from the merchant terminal 100. [ At this time, the merchant terminal 100 may generate a second payment key with the first payment key and generate an encryption key set based on the generated second payment key.

According to an embodiment of the present invention, the encryption key set may include a plurality of one-time encryption keys each of which can be used only once, and the serial number of the encryption key may include a key ID number used for encryption, ID and the number of transactions, and the encrypted card information may be encrypted until a period of time from the time when the card is recognized by the merchant terminal 100 to the card issuer server 200.

The card issuer server 200 can generate an encryption key set based on the first payment key and obtain an encryption key corresponding to the serial number of the selected encryption key among the generated encryption key sets, Information can be decoded.

According to an embodiment of the present invention, the serial number of the encryption key is managed by the merchant terminal 100, and the card issuer server 200 receives a transaction approval request including the serial number of the encryption key from the merchant terminal 100 And the card issuer server 200 itself can manage the serial number of the encryption key. That is, the serial number of the encryption key can be managed by either the merchant terminal 100 or the card issuer server 200.

Upon generation of the encryption key set, the card issuer server 200 may generate a second payment key with the first payment key and generate an encryption key set based on the generated second payment key, and the encryption key set is transmitted to the card issuer server 200 ) And the merchant terminal (100) based on the second payment key.

When the card issuer server 200 or the merchant terminal 100 generates the second payment key with the first payment key, the first payment key may be deleted.

The card issuer server 200 can perform the transaction approval using the decrypted card information and can transmit the transaction approval result to the affiliate shop terminal 100. [

2 is a block diagram showing the configuration of a card issuer server 200 according to an embodiment of the present invention.

2, the card issuer server 200 may include a key generation unit 210, a key transmission unit 220, an approval request reception unit 230, a decryption unit 240, and a transaction approval unit 250 .

First, the card issuer server 200 authenticates the merchant terminal 100, and when the authentication of the merchant terminal 100 is completed, the key generating unit 210 can generate the first payment key. Details related to the authentication of the merchant terminal 100 will be described later with reference to FIG.

The key generation unit 210 may generate an encryption key set based on the first payment key. When generating the encryption key set, the key generation unit 210 generates a second payment key with the first payment key and generates a second payment key based on the generated second payment key An encryption key set can be generated.

According to an embodiment of the present invention, the encryption key set may include a plurality of one-time encryption keys each of which can be used only once, and the key generation unit 210 and the merchant terminal 100 The first payment key may be generated in the same manner or may be generated based on the second payment key generated by the first payment key. If the second payment key is generated by the first payment key, the first payment key may be deleted.

The key transmitting unit 220 may transmit the first payment key generated by the key generating unit 210 to the merchant terminal 100.

The approval request receiving unit 230 may receive a transaction approval request from the merchant terminal 100. [ At this time, the transaction approval request may include card information encrypted with any one of the encryption keys selected from the encryption key sets, and may further include the serial number of the encryption key. Details related to the encrypted card information will be described later with reference to FIG.

According to an exemplary embodiment of the present invention, the serial number of the encryption key may include special data including a key ID number used for encryption, an ID of the merchant terminal 100, and the number of transactions, And may be managed by any one of the card issuer server 200.

The decryption unit 240 may obtain an encryption key corresponding to the serial number of the encryption key selected from the encryption key sets generated by the key generation unit 210, The encrypted card information included in the approval request can be decrypted.

The transaction acceptance unit 250 can perform transaction approval using the card information decrypted by the decryption unit 240 and can transmit a transaction approval result to the affiliate terminal 100. [

As shown in FIG. 3, the merchant system may be a card reader, an affiliate shop terminal 100, a POS server, or the like as shown in FIG. 3, although the merchant terminal 100 itself can perform transaction approval by performing communication with the card company server 200 And the merchant terminal 100 may communicate with the card issuer server 200 through the POS server to perform transaction approval.

The card reader can be implemented as a separate device, and can be implemented with both an MS card reader and an IC card reader.

When the card is recognized by the card reader, the merchant terminal 100 connected to the card reader can recognize the card recognized by the card reader and acquire the card information.

The merchant terminal 100 can encrypt the card information from the time of recognizing the card, and can transmit the encrypted card information to the card issuer server 200 through the POS server. At this time, encrypted card information may be transmitted between the POS server and the card issuer server 200 through a dedicated line.

When a failure occurs in the direct line connected between the POS server and the card issuer server 200, the card issuer server 200 can perform detour approval through the VAN company server. If a failure occurs in the card issuer server 200, Agents can be authorized through the VAN server.

When the card issuer server 200 receives the encrypted card information from the POS server via the direct line, it can decrypt the encrypted card information.

That is, the card information may be in an encrypted state from the time when the card is recognized by the merchant terminal 100 to the period that is transmitted to the card issuer server 200.

4 is a diagram illustrating a key exchange process for authentication and encryption processing of the merchant terminal 100. As shown in FIG.

First, various key management methods may be applied as a transaction encryption processing method for the direct approval processing between the merchant terminal 100 and the card issuer server 200. [

The key management method is a key management method that derives a unique key for each transaction approval, and may be a key management technique, not the encryption standard itself.

Key management methods include KSN (Key Serial Number), BDK (Base Derivation Key), IPEK (Initial Pin Encryption Key), Future Key, and One-Time Key.

The KSN is a unique value derived from information acquired by the merchant terminal 100 through the card reader, and may be a serial number of the encryption key.

The BDK is managed by only the card issuer server 200 as the top level key of the key management method and can be used to derive IPEK.

The IPEK is a key distributed to devices such as the merchant terminal 100, and is derived from the BDK and used to derive the Future Key, and can be deleted from the device after the Future Key is derived.

A Future Key is a set of keys to be used in the future, and can be used to generate one-time keys derived from IPEK.

The One-Time Key is a key used for encryption between the card issuer server 200 and the device, and is deleted once it is used, and a different key may be used for each transaction.

Referring to FIG. 4, 1) in the private key generation step, the card issuer server 200 can generate a private key using an RSA algorithm.

2) In the public key generation step, the card issuer server 200 can generate the public key from the private key, and can transmit the generated public key to the merchant terminal 100.

3) In the step of installing the public key terminal, the merchant terminal 100 may store the public key received from the card issuer server 200. [

4) In the terminal authentication request step, the merchant terminal 100 may transmit the terminal authentication request to the card issuer server 200. [

5) In the random value generation step, the card issuer server 200 can generate a random value.

6) In the random value hash step, the card issuer server 200 can hash the random value through SHA 256 or the like.

7) In the private key signing step, the card issuer server 200 can sign the random value in step 5) and the hash in step 6) with a private key.

8) In the terminal authentication response step, the card issuer server 200 can transmit a terminal authentication response including a random value, a hash, a private key signature, and the like to the affiliate terminal 100.

9) In the signature verification step, the merchant terminal 100 can verify the signature with the public key, and compare the random value and the hash value with the signature value decrypted with the public key.

9) After the signature verification step, authentication of the merchant terminal 100 is completed, and the merchant terminal 100 can be authenticated as a legitimate terminal.

10) In the arbitrary value generation step, the merchant terminal 100 may generate an arbitrary value to encrypt the IPEK.

11) In the arbitrary value hash step, the merchant terminal 100 can hash any value through SHA256 or the like.

12) In the encryption step with the public key, the merchant terminal 100 may encrypt the random value in step 10) and the hash of step 11) with the public key.

13) In the key download request step, the merchant terminal 100 may transmit the key download request including the KSN, the random value, and the public key encryption value of the hash to the card issuing server 200.

14) In the private key decryption step, the card issuer server 200 can decrypt the encrypted random value and the hash with the private key.

15) In the hash value verification step, the card issuer server 200 generates a hash by using SHA256 or the like for an arbitrary value, compares the generated hash value with the hash value transmitted from the merchant terminal 100, and verifies the hash value can do.

16) In the IPEK generation step, the card issuer server 200 can generate IPEK using the KSN.

17) In the encryption step, the card issuer server 200 can generate an encryption key and a MAC key from a random value through CMAC or the like, encrypt KSN and IPEK, and generate a MAC value of IPEK.

18) In the key delivery step, the card issuer server 200 can transmit the key including the encryption value and the MAC value to the merchant terminal 100.

19) In the IPEK decoding step, the merchant terminal 100 can decode IPEK, and 20) In the MAC verification step, the merchant terminal 100 can verify the MAC value.

21) In the Future Key generation step, the merchant terminal 100 can generate a Future Key using the IPEK and delete the IPEK after generating the Future Key.

According to an embodiment of the present invention, steps 5), 6), 7), 15), and 16) may be handled through the HSM command, and steps 14) and 17) Lt; / RTI >

First, the merchant terminal 100 can generate a One Time Encrypt Key in the Future Key inserted into the card reader as soon as the card reader recognizes the card. After encrypting the card information using the generated One Time Encrypt Key, And may transmit the encrypted card information and the KSN to the card issuer server 200 together with the transaction approval request.

Card issuer server 200 can generate IPEK using KSN in BDK and generate Future Key using KSN in IPEK.

The card issuer server 200 can separate the encrypted One Time Encrypt Key and the encrypted card information through Future Key matching based on KSN, and can acquire the card information by decrypting the encrypted card information.

Thereafter, the card issuer server 200 can perform transaction approval using the acquired card information.

6 is a diagram illustrating a process of performing end-to-end encryption (E2E) for a direct authorization process between the merchant terminal 100 and the card issuer server 200 according to an embodiment of the present invention.

The merchant terminal 100, which is a payment terminal capable of directly accepting payment, may be installed in the merchant terminal 100. The merchant terminal 100 may transmit a payment key request to the credit card company server 200 in the payment key requesting step. Here, the payment key request may be a request for a first payment key, which is an initial payment key for encrypting sensitive information when a transaction is approved.

The merchant terminal 100 may send the terminal authentication request to the card issuer server 200 while transmitting the payment key request.

(2) In the terminal authentication step, the card issuer server 200 can perform authentication for the merchant terminal 100 based on merchant information or the like.

(3) In the first payment key generation step, when the authentication of the merchant terminal 100 is completed, the card company server 200 transmits an initial payment key for the end-to-end encryption E2E of the card issuer server 200 and the merchant terminal 100 The first payment key can be generated.

(4) In the first payment key transmission step, the credit card company server 200 can transmit the generated first payment key to the merchant terminal 100.

(5) In the second payment key generation step, the merchant terminal 100 can generate the second payment key with the first payment key received from the card issuer server 200. [ At this time, the merchant terminal 100 can delete the first payment key while generating the second payment key.

(6) In the encryption key set generation step, the merchant terminal 100 may generate an encryption key set based on the generated second payment key.

According to an embodiment of the present invention, the encryption key set may be generated by combining a first payment key and a symmetric key with a plurality of key sets generated by default of a second payment key, Lt; RTI ID = 0.0 > encryption key.

The encryption key set may be generated in the same way in the merchant terminal 100 and the card issuer server 200 if the merchant terminal 100 and the card issuer server 200 have the same second payment key.

(7) In the card information encryption step, the merchant terminal 100 can select any one of the encryption key sets and encrypt the card information with the selected encryption key.

(8) In the approval requesting step, the merchant terminal 100 may transmit a transaction approval request including the encrypted card information and the serial number of the encryption key selected at the time of encryption, payment amount information, merchant store identification information, etc. to the card issuer server 200 have.

According to one embodiment of the present invention, the serial number of the encryption key may include the key identification information used in encrypting the card information in the encryption key set, the identification information of the merchant terminal 100, and the professional data including the transaction count have.

According to an embodiment of the present invention, when the serial number of the encryption key is managed by the card issuer server 200, the merchant terminal 100 transmits a transaction approval request not including the serial number of the encryption key to the card issuer server 200, Lt; / RTI >

(9) In the second payment key generation step, the card issuer server 200 can distinguish the merchant terminal 100 through the serial number of the encryption key, distinguish the first payment key corresponding to the merchant terminal 100, And generate a second payment key with the first payment key.

(10) In the encryption key set generation step, the card issuer server 200 may generate an encryption key set based on the generated second payment key.

(11) In the card information decryption step, the card issuer server 200 can acquire the encryption key used for encryption among the encryption key set using the serial number of the encryption key, and obtains the encrypted The card information can be decoded.

(12) At the transaction approval stage, the card issuer server 200 can perform transaction approval using the decrypted card information.

In the transaction approval result transmission step, the card issuer server 200 can transmit the transaction approval result to the affiliate shop terminal 100.

(14) In the approval completion stage, the merchant terminal 100 can confirm that the approval requested through the received transaction approval result is completed, and can output the sales table, the receipt, and the like to the customer.

As described above, according to the embodiment of the present invention, since the payment approval process can be performed without the VAN company through the direct approval process between the franchisee terminal 100 and the card issuer server 200, the transaction fee paid to the VAN company Can be saved.

Also, according to an embodiment of the present invention, end-to-end encryption (E2E) of the merchant terminal 100 and the card issuer server 200 can be performed to secure security in transaction approval through direct approval.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: Merchant terminal

200: card company server

210:

220:

230: authorization request receiver

240:

250: Transaction Approval Department

Claims

In the card issuer server, in the method of processing transaction approval,

(a) generating a first payment key when the authentication of the merchant terminal is completed, and transmitting the generated first payment key to the merchant terminal;

(b) receiving, from the merchant terminal, a transaction approval request including card information encrypted with any one of the encryption keys selected from among the encryption key sets generated based on the first payment key;

(c) generating the encryption key set based on the first payment key, obtaining an encryption key corresponding to the serial number of the selected encryption key in the generated encryption key set, and transmitting the encrypted Decrypting the card information; And

(d) performing transaction approval using the decrypted card information, and transmitting a transaction approval result to the merchant terminal.
The method according to claim 1,

The step (c)

Generating a second payment key with the first payment key, and generating the encryption key set based on the generated second payment key.
3. The method of claim 2,

Wherein the encryption key set is generated on the basis of the second payment key in the card company server and the merchant terminal.
3. The method of claim 2,

Wherein the first payment key is deleted when the second payment key is generated.
The method according to claim 1,

Wherein the encryption key set includes a plurality of one-time encryption keys each of which can be used only once.
The method according to claim 1,

Wherein the encrypted card information is encrypted from a time point at which the card is recognized by the merchant terminal to an interval transmitted to the card issuer server.
The method according to claim 1,

Wherein the serial number of the encryption key includes special data including key identification information used for encryption, identification information of the merchant terminal, and transaction count.
A card issuer server for processing transaction approval,

A key generation unit for generating a first payment key when the authentication for the merchant terminal is completed and generating an encryption key set based on the first payment key;

A key transmission unit for transmitting the generated first payment key to the merchant terminal;

An approval request receiver for receiving a transaction approval request from the merchant terminal including card information encrypted with any one of the encryption keys selected from among the encryption key sets generated based on the first payment key;

A decryption unit that obtains an encryption key corresponding to a serial number of the selected encryption key among the generated encryption key sets and decrypts the encrypted card information with the obtained encryption key; And

And a transaction approval unit that performs transaction approval using the decrypted card information and transmits a transaction approval result to the merchant terminal.
9. The method of claim 8,

The key generation unit may generate,

Generates a second payment key with the first payment key, and generates the encryption key set based on the generated second payment key.
10. The method of claim 9,

Wherein the encryption key set is generated on the basis of the second payment key in the key generation unit and the merchant terminal.
10. The method of claim 9,

Wherein the first payment key is deleted when the second payment key is generated.
9. The method of claim 8,

Wherein the encryption key set includes a plurality of one-time encryption keys each of which can be used only once.
9. The method of claim 8,

Wherein the encrypted card information is encrypted from a time point when the card is recognized by the merchant terminal to an interval that is transmitted to the card issuer server.
9. The method of claim 8,

Wherein the serial number of the encryption key includes special data including key identification information used for encryption, identification information of the merchant terminal, and transaction count.