Patent Publication Number: US-9892277-B2

Title: Device and method for encoding data column

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a National Stage Patent Application of PCT International Patent Application No. PCT/KR2014/009187 filed on Sep. 30, 2014 under 35 U.S.C. 371, which claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2013-0117242 filed on Oct. 1, 2013, which are all hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an apparatus and method for encoding a data column, and more particularly to an apparatus and method for encoding a data column in a table form. 
     BACKGROUND ART 
     The modern companies usually construct and manage a database storing customer information and personnel information in order to provide services to customers or manage inside operations. The resident registration numbers, addresses, telephone numbers, etc. of the customers and personnel are stored in such the database. According to advancement of hacking skills, leakage of such the important information may become a critical social problem. In order to resolve the above problem, the act on the protection of personal information was legislated, and the government requests companies to prepare measures for preventing the leakage of personal information owned by the companies according to the act. Accordingly, each company manages customer or personnel information in a database by encrypting them. In this case, target data to be encrypted are selected according to the act (i.e. the act on the protection of personal information). 
     Meanwhile, the database stores actual data such as resident registration numbers, addresses, telephone numbers, etc. together with indexes and constraint conditions (e.g. primary key (PK) and foreign key (FK)). In such the situation, a manager of the database selects target tables and target fields in the target tables for the encryption based on the act. Then, encryption on the target tables and the target fields is performed. However, in such the encryption procedure, conventional encryption techniques may make a problem that the encrypted tables collide with other relevant tables or a problem that relations between the encrypted tables and other relevant tables are destructed. Also, even after the encryption, inside information may be searched by using the indexes, or systems may be changed by using the indexes, whereby critical security risks can be caused. 
     A method for encrypting a data column, in which indexes of an encryption target column are deleted, the target column is encrypted, and indexes of the encrypted column are regenerated, was disclosed in Korean patent publication No. 2006-0087103. According to such the method for data column encryption, security can be strengthened when a data column for which indexes or PKs are configured is encrypted. However, since indexes of the target column are deleted before encryption, any error occurring during the encryption procedure may damage the original target column or cause data loss in the original target column. Also, since the encryption is performed with data properties of the table being maintained, data length changes according to applied encryption techniques cannot be coped with properly. 
     Disclosure 
     Technical Problem 
     The technical purpose of the present invention is to provide a method for data column encryption, which can be adapted to an encryption technique used for encryption on a data column, and cope with various error situations occurring in the encryption procedure. 
     Also, another technical purpose of the present invention is to provide a computer-readable recording medium storing a program for executing a method for data column encryption, which can be adapted to an encryption technique used for encryption on a data column, and cope with various error situations occurring in the encryption procedure. 
     Technical Solution 
     The present invention to achieve the above-described purpose provides a data column apparatus comprising a schema inquiry unit inquiring into a schema of an original table, an encoding target table on which encoding is to be performed, in a database in which a plurality of data tables are stored, a backup performing unit generating schema information of a backup table on the basis of the schema of the original table, generating the backup table by using the schema information of the backup table so as to copy data of the original table into the backup table, changing the original table by adding backup columns to the original table, and inactivating constraint conditions included in the changed original table so as to copy original columns included in the changed original table into the backup columns; and an encoding unit encoding data of encoding target columns, columns on which encoding is to be performed in the changed original table, and entering the encode data in respective fields of the original columns of the changed original table. Also, the backup performing unit may delete the backup columns from the changed original table and activate the constraint conditions after the encoding for the data of the encoding target columns is completed. 
     The present invention to achieve the above-described purpose provides a data column encoding method comprising inquiring into a schema of an original table, an encoding target table on which encoding is to be performed, in a database in which a plurality of data tables are stored; generating schema information of a backup table on the basis of the schema of the original table, and generating the backup table by using the schema information of the backup table so as to copy data of the original table into the backup table; changing the original table by adding backup columns to the original table, and inactivating constraint conditions included in the changed original table so as to copy original columns included in the changed original table into the backup columns; encoding data of encoding target columns, columns on which encoding is to be performed in the changed original table, and entering the encoded data in respective fields of the original columns of the changed original table, and deleting the backup columns from the changed original table and activating the constraint conditions after the encoding for the data of the encoding target columns is completed. 
     Advantageous Effects 
     Using the data column encoding apparatus and method according to the present invention, a backup table for an original table is generated, and then a data column is encrypted. Meanwhile, since an index column of the original table is not deleted, reliability of the encryption procedure can be enhanced. Also, since encryption target columns are encrypted after data types of the encryption target columns are changed, the apparatus and method according to the present invention can adaptively cope with various encryption techniques which can be used for encryption of the encryption target columns. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a data column encoding apparatus according to the present invention: and 
         FIG. 2  is a flow chart to illustrate a preferred exemplary embodiment of a data column encryption method according to the present invention. 
     
    
    
     BEST MODE 
     Hereinafter, preferred exemplary embodiments for a data column encoding apparatus and method according to the present invention will be explained in detail by referring to accompanying figures. 
       FIG. 1  is a view illustrating a data column encoding apparatus according to the present invention. 
     Referring to  FIG. 1 , the data column encoding apparatus  100  according to the present invention may comprise a schema inquiry unit  110 , a backup performing unit  120 , an encoding unit  130 , and an index generating unit  140 . 
     The schema inquiry unit  110  may inquire into a schema of an original table, an encoding target table on which encoding is to be performed, in a database in which a plurality of data tables are stored. Such the schema inquiry may include a table script inquiry, an index script inquiry, and a constraint condition inquiry. In this instance, the schema inquiry unit  110  may store a result of the schema inquiry in a storage (not depicted) equipped within the data column encoding apparatus  100 . The schema of the original table may be previously stored in a database  200 , or may be generated by the schema inquiry unit  110  from the original table. In the following tables 1 to 3, examples of schema information, data, and database indexes of the original table are represented. The examples are for a case in which the original table is a division information table for storing division codes and division names of a specific company. Also, in the following tables 4 to 6, examples of schema information, data, and database indexes of the original table are represented. The examples are for a case in which the original table is a personal information table for storing personal information of a specific company. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Num 
               
               
                 Column 
                   
                   
                   
                   
                 De- 
                 Histo- 
                 Iden- 
               
               
                 Name 
                 ID 
                 PK 
                 Null? 
                 Data Type 
                 fault 
                 gram 
                 tifier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Division 
                 2 
                   
                 Y 
                 VARCHAR2 
                 None 
               
               
                 Name 
                   
                   
                   
                 (50 bytes) 
               
               
                 Division 
                 1 
                 1 
                 N 
                 CHAR 
                 None 
               
               
                 Code 
                   
                   
                   
                 (1 byte) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Division Code 
                 Division Name 
               
               
                   
               
             
            
               
                 1 
                 Development team 
               
               
                 2 
                 Support team 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                   
                   
                 Table 
               
               
                 Index 
                 Schema 
                 Table schema 
                 Table Name 
                 Space 
               
               
                   
               
             
            
               
                 DEPT_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT 
                 USERS 
               
               
                 SYS_IL0000095871C00036$$ 
                 EXAMPLE 
                 EXAMPLE 
                 TOAD_PLAN_TABLE 
                 USERS 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Num 
               
               
                 Column 
                   
                   
                   
                   
                 De- 
                 Histo- 
                 Iden- 
               
               
                 Name 
                 ID 
                 PK 
                 Null? 
                 Data Type 
                 fault 
                 gram 
                 tifier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Division 
                 2 
                   
                 Y 
                 CHAR 
                 1 
                 None 
               
               
                 Code 
                   
                   
                   
                 (1 byte) 
               
               
                 Identifier 
                 1 
                 1 
                 N 
                 INTEGER 
                   
                 None 
               
               
                 Telephone 
                 4 
                   
                 Y 
                 VARCHAR2 
                   
                 None 
               
               
                 Number 
                   
                   
                   
                 (13 bytes) 
               
               
                 Resident 
                 3 
                   
                 Y 
                 VARCHAR2 
                   
                 None 
               
               
                 Registration 
                   
                   
                   
                 (14 bytes) 
               
               
                 Number 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 Resident 
                   
               
               
                   
                   
                 Registration 
               
               
                 Identifier 
                 Division Code 
                 Number 
                 Telephone Number 
               
               
                   
               
             
            
               
                 1000 
                 1 
                 820101-1234567 
                 010-1234-5678 
               
               
                 1001 
                 2 
                 830201-2345678 
                 010-2345-6789 
               
               
                 1002 
                 1 
                 840301-1234567 
                 010-3456-7890 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                   
                   
                   
                   
                 Table 
               
               
                 Index 
                 Schema 
                 Table schema 
                 Table Name 
                 Space 
               
               
                   
               
             
            
               
                 DEPT_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT 
                 USERS 
               
               
                 SYS_C0019951 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE 
                 USERS 
               
               
                 SYS_C0019952 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLYOEE 
                 USERS 
               
               
                 SYS_IL0000095871C00036$$ 
                 EXAMPLE 
                 EXAMPLE 
                 TOAD_PLAN 
                 USERS_TABLE 
               
               
                   
               
            
           
         
       
     
     The backup performing unit  120  may generate schema information of a backup table based on the inquired schema information of the original table. Also, the backup performing unit  120  may generate the backup table by using the generated schema information of the backup table, and copy data of the original table to the backup table. When the backup table is generated, database indexes for the backup table are generated. Here, the indexes starting with ‘SYS’ may be generated by the database  200 , and the other indexes may be generated by the backup performing unit  120 . 
     In the tables 7 and 8, indexes, which are generated by the database  200  after the backup of the division information table and after the backup of the division information table and the personnel information table, are represented. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 Index 
                 Schema 
                 Table Schema 
                 Table Name 
                 Table 
               
               
                   
               
             
            
               
                 DEPT_BAK_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT_BAK 
                 USERS 
               
               
                 DEPT_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT 
                 USERS 
               
               
                 SYS_C0019951 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE 
                 USERS 
               
               
                 SYS_C0019952 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE 
                 USERS 
               
               
                 SYS_IL0000095871C00036$$ 
                 EXAMPLE 
                 EXAMPLE 
                 TOAD_PLAN_TABLE 
                 USERS 
               
               
                 DEPT_BAK_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT_BAK 
                 USERS 
               
               
                 DEPT_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT 
                 USERS 
               
               
                 SYS_C0019951 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE 
                 USERS 
               
               
                 SYS_C0019952 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE 
                 USERS 
               
               
                 SYS_C0019955 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE_BAK 
                 USERS 
               
               
                 SYS_C0019956 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE_BAK 
                 USERS 
               
               
                 SYS_IL0000095871C00036$$ 
                 EXAMPLE 
                 EXAMPLE 
                 TOAD_PLAN_TABLE 
                 USERS 
               
               
                   
               
            
           
         
       
     
     After then, the backup performing unit  120  may inactivate constraint conditions including PK, FK, Unique, and indexes of the original table. The indexes staring with ‘SYS_C’, which are assigned by the database  200 , may be automatically deleted by the database  200 . In the table  9 , the index table stored in the database  200  after deletion of the indexes staring with ‘SYS_C’ is represented. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 9 
               
               
                   
               
               
                 Index 
                 Schema 
                 Table Schema 
                 Table Name 
                 Table 
               
               
                   
               
             
            
               
                 DEPT_BAK_PK 
                 EXAMPLE 
                 EXAMPLE 
                 DEPT_BAK 
                 USERS 
               
               
                 SYS_C0019955 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE_BAK 
                 USERS 
               
               
                 SYS_C0019956 
                 EXAMPLE 
                 EXAMPLE 
                 EMPLOYEE_BAK 
                 USERS 
               
               
                 SYS_IL0000095871C0036$$ 
                 EXAMPLE 
                 EXAMPLE 
                 TOAD_PLAN_TABLE 
                 USERS 
               
               
                   
               
            
           
         
       
     
     Then, the backup performing unit  120  may change the original table by adding backup columns to the original table, and copy values of a column whose type is to be changed among the original columns of the changed original table to the corresponding backup column. The following tables 10 and 11 respectively represent schema information of the division information table and personnel information after addition of the backup columns. Also, the following tables 12 and 13 respectively represent the division information table and the personnel information table after addition of the backup columns. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Num 
               
               
                 Column 
                   
                   
                   
                   
                 De- 
                 Histo- 
                 Iden- 
               
               
                 Name 
                 ID 
                 PK 
                 Null? 
                 Data Type 
                 fault 
                 gram 
                 tifier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Division 
                 2 
                   
                 Y 
                 VARCHAR2 
                 None 
               
               
                 Name 
                   
                   
                   
                 (50 bytes) 
               
               
                 Division 
                 1 
                 1 
                 N 
                 CHAR 
                 None 
               
               
                 Code 
                   
                   
                   
                 (1 byte) 
               
               
                 Division 
                 3 
                   
                 Y 
                 CHAR 
                 None 
               
               
                 Code_BAK 
                   
                   
                   
                 (1 byte) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 11 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Num 
               
               
                 Column 
                   
                   
                   
                   
                 De- 
                 Histo- 
                 Iden- 
               
               
                 Name 
                 ID 
                 PK 
                 Null? 
                 Data Type 
                 fault 
                 gram 
                 tifier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Division Code 
                 2 
                   
                 Y 
                 CHAR 
                 1 
                 None 
               
               
                   
                   
                   
                   
                 (1 byte) 
               
               
                 Division 
                 6 
                   
                 Y 
                 CHAR 
                   
                 None 
               
               
                 Code_BAK 
                   
                   
                   
                 (1 byte) 
               
               
                 Identifier 
                 1 
                 1 
                 N 
                 INTEGER 
                   
                 None 
               
               
                 Identifier_BAK 
                 5 
                   
                   
                 INTEGER 
                   
                 None 
               
               
                 Telephone 
                 4 
                   
                 Y 
                 VARCHAR2 
                   
                 None 
               
               
                 Number 
                   
                   
                   
                 (13 bytes) 
               
               
                 Telephone 
                 7 
                   
                 Y 
                 VARCHAR2 
                   
                 None 
               
               
                 Number_BAK 
                   
                   
                   
                 (13 bytes) 
               
               
                 Resident 
                 3 
                   
                 Y 
                 VARCHAR2 
                   
                 None 
               
               
                 Registration 
                   
                   
                   
                 (14 bytes) 
               
               
                 Number 
               
               
                 Resident 
                 8 
                   
                 Y 
                 VARCHAR2 
                   
                 None 
               
               
                 Registration 
                   
                   
                   
                 (14 bytes) 
               
               
                 Number_BAK 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 12 
               
               
                   
               
               
                 Division Code 
                 Division Name 
                 Division Code_BAK 
               
               
                   
               
             
            
               
                 1 
                 Development team 
                 1 
               
               
                 2 
                 Support team 
                 2 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 13 
               
               
                   
               
               
                   
                   
                 Resident 
                   
                   
                   
                 Resident 
                   
               
               
                   
                 Division 
                 Registration 
                 Telephone 
                   
                 Division 
                 Registration 
                 Telephone 
               
               
                 Identifier 
                 Code 
                 Number 
                 Number 
                 Identifier_BAK 
                 Code_BAK 
                 Number_BAK 
                 Number_BAK 
               
               
                   
               
             
            
               
                 1000 
                 1 
                 820101-1234567 
                 010-1234-5678 
                 1000 
                 1 
                 820101-1234567 
                 010-1234-5678 
               
               
                 1001 
                 2 
                 830201-2345678 
                 010-2345-6789 
                 1001 
                 2 
                 830201-2345678 
                 010-2345-6789 
               
               
                 1002 
                 1 
                 840301-1234567 
                 010-3456-7890 
                 1002 
                 1 
                 840301-1234567 
                 010-3456-7890 
               
               
                   
               
            
           
         
       
     
     Then, the backup performing unit  120  may delete data of columns whose types are changed from the changed original table. The reason is that data of columns whose types are changed should be deleted in order to change types of the columns. Since the division information table represented in the table 12 does not have columns whose types are changed, the division information table in the table 12 does not have columns whose data are deleted. However, in a case of the personnel information table represented in the table 13, since a type of the ‘identifier’ column is changed from INTEGER to CHAR, data of the ‘identifier’ column are deleted. Also, the backup performing unit  120  may change types of encryption target columns (e.g. ‘identifier’, ‘division code’, ‘resident registration number’, ‘telephone number’) among columns of the changed original table to types corresponding to an encryption technique to be performed on the encryption target columns. For example, if the encryption technique is a technique for encrypting encryption target data as data with a type of 24 bytes VARCHAR2 having 24 bytes length, the backup performing unit  120  may change data type of the encryption target columns to 24 bytes VARCHAR2, and record information on such the change in the schema table. 
     The encoding unit  130  may encode data of encoding target columns, columns on which encoding is to be performed in the changed original table, and entering the encoded data in each field of the original columns of the changed original table. In this instance, the encoding unit  130  may encode a default value when the default value is configured in the encoding target column. The encoding unit  130  may use any one or combination of various known encoding techniques in order to encode the encoding target columns. Since such the encoding techniques are well known to skilled persons pertaining to a technology domain according to the present invention, detail explanations on the encoding techniques are omitted. After the encoding unit  130  completes the encoding on the data in the encoding target columns, the backup performing unit  120  may delete the backup columns (i.e. ‘Identifier_BAK’, ‘Division code_BAK’, ‘Telephone Number_BAK’, and ‘Resident Registration Number_BAK’) from the changed original table, and activate the constraint conditions. 
     After completion of the encoding of the data of the encoding target columns, the index generating unit  140  may regenerate indexes in the index table. Since the indexes starting with ‘SYS_C’ have been automatically deleted by the database  200  at the inactivation of the constraint conditions, it is needed to regenerate the deleted indexes after completion of the encoding. In the above-explained exemplary embodiment, indexes corresponding to the ‘identifier’ and ‘resident registration number’ start with ‘SYS_C’, and thus the index generating unit  140  may regenerate indexes corresponding to the ‘identifier’ and ‘resident registration number’. Also, for a function based index such as ‘Division Code’ and a domain index such as ‘PK’, indexes should be regenerated after the encoding of the data of the encoding target columns. On the other hand, since indexes based on names assigned by users are automatically regenerated by the database  200  when the constraint conditions are activated, the index generating unit  140  does not have to generate the indexes. 
     As stated above, after the encoding of the data in the changed original table is completed, the backup performing unit  120  may delete the backup table. If an error occurs during the procedure of encoding the changed original table, the original table is restored based on the backup table, and then the encoding procedure is performed again. Here, the encoding procedure on the changed original table may mean a whole procedure from the inactivation of the constraint conditions of the original table to the activation of the constraint conditions of the changed original table. If an error occurs in the encoding procedure, the original table is restored, and the encoding procedure is performed again. 
       FIG. 2  is a flow chart to illustrate a preferred exemplary embodiment of a data column encryption method according to the present invention. 
     Referring to  FIG. 2 , the schema inquiry unit  110  may inquire into a schema of an original table which is a data table on which encoding is to be performed in a database in which a plurality of data tables are stored (S 200 ). Then, the backup performing unit  120  may generate schema information of a backup table on the basis of the schema of the original table (S 210 ). Also, the backup performing unit  120  may generate the backup table by using the generated schema information of the backup table so as to copy data of the original table into the backup table (S 220 ). 
     Then, the backup performing unit  120  may inactivate constraint conditions including PK, FK, Unique, and indexes of the original table (S 230 ). In this instance, indexes starting with ‘SYS_C’, which are assigned by the database  200 , may be deleted automatically by the database  200 . 
     Then, the backup performing unit  120  may change the original table by adding backup columns to the original table (S 240 ). Then, the backup performing unit  120  may copy values of columns whose types are to be changed, among columns of the original table corresponding to the added backup columns, to the backup columns (S 250 ). Then, the backup performing unit  120  may delete data of the columns whose types to be changed from the changed original table, and change types of encoding target columns on which encoding is to be performed to types corresponding to an encoding technique to be applied (S 260 ). Then, the encoding unit  130  may encodes data of the encoding target column, a column in which encoding is to be performed in the changed original table, and entering the data in each field of the original columns of the changed original table (S 270 ). After the encoding unit  130  completes the encoding of the data of the encoding target column, the backup performing unit  120  may delete the backup columns from the changed original table, and activate the constraint conditions (S 280 ). 
     If the encoding procedure is completed without any error (S 290 ), the backup performing unit  120  may delete the backup table (S 300 ), and the index generating unit  140  may regenerate indexes of the index table (S 320 ) after completion of the encoding of the data in the encoding target column. On the contrary, if an error occurs in the encoding procedure (S 290 ), the backup performing unit  120  may restore the original table based on the backup table (S 310 ), and the steps from S 230  are performed again. Here, the encoding procedure in the step S 290  may mean a whole procedure from the deactivation of the constraint conditions of the original table in the step S 230  to the activation of the constraint conditions of the changed original table in the step S 280 . Thus, if an error occurs in the procedure from the step S 230  to the step S 280 , the step S 310  may be performed. Also, the step S 320  may be performed before the step S 300 . 
     The apparatuses and methods according to the present disclosure may be implemented as a program code recorded in a computer-readable recording medium. The computer-readable recording medium may include all types of storage devices on which computer-readable data can be stored. For example, the computer-readable recording medium may be read-only memory (ROM), random access memory (RAM), compact disc ROM (CD-ROM), magnetic tape, a floppy disc, an optical data storage device, etc. Also, a carrier wave (i.e., transmission through internet) may be included as the computer-readable recording medium. Also, the computer-readable recording medium may be distributed over computer systems connected through wire or wireless communication networks, and the computer-readable program code can be stored and executed in the distributive manner. 
     Although the preferred exemplary embodiments are illustrated and explained in the present specification, the present invention is not restricted to the above-described specific preferred exemplary embodiments, and it should be understood that various changes, substitutions and alterations may be made herein without departing from the scope of the invention.