Data library encryption and decryption technology, one of FoxPro

Encryption | decryption
Data library encryption and decryption technology, one of FoxPro
Author: ccbzzp

In reality, the security of the data is very important, especially in a very important department like the bank,
So the encryption of the data is particularly important, and in the long term, the pen is always the encryption and decryption of the various numbers.
Write the law, I hope to help you, and we also explore together, learn together, and progress together!

FoxPro provides some low-level file operation functions for the user, using these low-level operational functions, you can actually operate on low-level files, and these low-level functions are mainly: FCLOSE (), Fcreate (), FEOF (), Ferror (), Fflush (), FGETS ( ), FOPEN (), FPUTS (), FREAD (), fseek (), Strtofile (), and so on, the specific usage of these functions is not specifically described here, and these functions are used in the following articles.

1. Data encryption

The following is an example of modifying a user's password to explain:

Program Chang_password Click () content:

IF VARTYPE (M.id_man) <> ' C '. OR. VARTYPE (M.ID_PSD) <> ' C '
=messagebox (' You haven't registered! No more password, ', 0+48+0, ' info tip! ') =6
Return
ELSE
SELECT &father_table.
LOCATE for Alltrim (Id_man) ==alltrim (M.id_man);
. and.

Alltrim (this. Parent.encrypt_data. CLICK (Id_psd,m.id_man)) ==alltrim (M.ID_PSD);
. and.! DELETED ()
IF FOUND ()
IF Alltrim (m.new_password1) ==alltrim (M.NEW_PASSWORD2)
REPLACE &father_table ... ID_PSD with

this. Parent.encrypt_data. CLICK (M.new_password1,m.id_man)
=messagebox (' Password changes are more successful! ', 0+48+0, ' Information tips! ')
ELSE
=messagebox (' Password doesn't change! Two new codes are inconsistent! ', 0+48+0, ' info tip!

')
ENDIF
ELSE
=messagebox (' Password doesn't change! Old password wrong! ', 0+48+0, ' info tip! ')
ENDIF
ENDIF
this. PARENT. Release ()




Program Encrypt_data Click () content:

Lparameters Encrypt_password, ENCRYPT_CHR
Encrypt_chr=alltrim (UPPER (ENCRYPT_CHR))
encrypt_chr1= ' 340821960120581 '
Encrypt_long=len (ENCRYPT_CHR1)
Encrypt_chr2=left (Encrypt_chr+encrypt_chr+encrypt_chr+encrypt_chr,encrypt_long)
This.return_data= '
For I=1 to Encrypt_long step 1
ALTERATION_CHR=CHR (Bitxor (ASC (SUBST (encrypt_chr1,i,1)), ASC (SUBST (encrypt_chr2,i,1)))


THIS.RETURN_DATA=THIS.RETURN_DATA+CHR (Bitxor (ASC (SUBST (encrypt_password,i,1)), ASC (Alterati

ON_CHR)))
ENDfor
Return This.return_data


2. In the data library file to encrypt
If there is a number of data library file C:\USERS. DBF;

Handle1=fopen ("C:\USERS.") DBF ")
IF handle1<0
MESSAGEBOX ("No specified file found ...", 0+64, "info tip!")
Return
ENDIF
I=1
Handle2=fcreate ("C:\USERS.") DBF ")
Do While. T.
=fseek (HANDLE1,I*32)
Retasc=fread (handle1,32)
IF ASC (RETASC) =13
EXIT
ENDIF
I=i+1
Enddo
=fseek (handle1,0)
Retstr=fread (HANDLE,I*32)
=fwrite (HANDLE2,RETSTR)
X=i*32
J=0
Do While. Not. FEOF (HANDLE1)
=fseek (HANDLE1,X+J)
Retasc=fread (handle1,1)
IF ASC (RETASC) >253
CH=CHR (255-ASC (RETASC))
ELSE
CH=CHR (ASC (RETASC) +2)
ENDIF
=fwrite (Handle2,ch)
J=j+1
Enddo
MESSAGEBOX ("Encryption successful ...", 0+64, "info tip!")
=fclose (HANDLE1)
=fclose (HANDLE2)
Return



3. In the data library file to decrypt
If there is a number of data library file C:\USERS. DBF;

Handle1=fopen ("C:\USERS.") DBF ")
IF handle1<0
MESSAGEBOX ("No specified file found ...", 0+64, "info tip!")
Return
ENDIF
Handle2=fcreate ("C:\USERS.") DBF ")
I=1
Do While. T.
=fseek (HANDLE1,I*32)
Retasc=fread (handle1,32)
IF ASC (RETASC) =13
EXIT
ENDIF
I=i+1
Enddo
=fseek (handle1,0)
Retstr=fread (HANDLE,I*32)
=fwrite (HANDLE2,RETSTR)
X=i*32
J=0
Do While. Not. FEOF (HANDLE1)
=fseek (HANDLE1,X+J)
Retasc=fread (handle1,1)
IF ASC (RETASC) <2
CH=CHR (255-ASC (RETASC))
ELSE
CH=CHR (ASC (RETASC)-2)
ENDIF
=fwrite (Handle2,ch)
J=j+1
Enddo
MESSAGEBOX ("Decryption successful ...", 0+64, "info tip!")
=fclose (HANDLE1)
=fclose (HANDLE2)
Return


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