¡ÒÃà¢éÒÃËÑÊ áÅÐ ¶Í´ÃËÑÊ ´éǵÃáÈÒʵÃì XOR (eXclusive OR) - ÀÒ¤ 1

    Dim Dec As Byte
    
    For Dec = 0 To 255
        Debug.Print "Character : " & Chr(Dec) & " : ASCII Code = " & Dec
        If Dec = 255 Then Exit For
    Next

Option Explicit

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' American Standard Code for Information Interchange - ASCII (áÍÊ¡Õé)
' http://www.ascii.ca/cp874.htm
' http://en.wikipedia.org/wiki/ASCII
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Private Sub Form_Load()

    Me.Move (Screen.Width - Width) \ 2, (Screen.Height - Height) \ 2
    
    txtData.Text = "This is a book"
    txtEncrypt.Text = ""
    txtDecrypt.Text = ""
    
End Sub

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' àÃÔèÁµé¹¡ÒÃà¢éÒÃËÑÊ áÅÐ ¶Í´ÃËÑÊ
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Private Sub cmdRun_Click()

    If Trim(txtData.Text) = "" Or Len(Trim$(txtData.Text)) = 0 Then Exit Sub
    ' ãËéà¢éÒÃËÑÊ´éÇ¡Òà eXclusive OR - XOR ¾ÃéÍÁ¡ÑºµÑÇà¢éÒÃËÑÊ
    ' µÑÇà¢éÒÃËÑÊ ËÃ×Í ¡Ø­á¨ ·Õè¼ÁµÑé§äÇé¤×Í 255 à»ç¹àÅ¢¨Ó¹Ç¹àµçÁ¢¹Ò´ 1 亵ì
    ' «Öè§àÁ×èÍà¡Ô´¡ÒáÃзÓÃдѺºÔµ¡Ñº XOR ¤èÒ¹Õé¨Ðà»ÅÕè¹á»Å§à»ç¹
    ' 1 1 1 1 1 1 1 1 (°Ò¹ 2) = 255 (°Ò¹ 10)
    txtEncrypt.Text = Encrypt(txtData.Text, 255)
    ' ÍèÒ¹ÇÔ¸Õ¡ÒÃá»Å§àÅ¢°Ò¹ 10 à»ç¹àÅ¢°Ò¹ 2 »ÃСͺ´éǤÃѺ
    ' http://www.g2gnet.com/News/activenews_view.asp?articleID=129
    
    ' ¶Í´ÃËÑÊ´éÇ¡Òà eXclusive OR - XOR ¾ÃéÍÁ¡ÑºµÑǶʹÃËÑÊ
    txtDecrypt.Text = Decrypt(txtEncrypt.Text, 255)
    
End Sub

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' ¡ÒÃà¢éÒÃËÑÊẺ§èÒÂæÍÒÈÑÂËÅÑ¡¡Òâͧ XOR - ºÔµã´àËÁ×͹¡Ñ¹¨Ðä´é 0 ºÔµã´·ÕèµèÒ§¡Ñ¹¨Ðä´é 1
' ãËé MyData ÃѺ¤èҪش¢éͤÇÒÁà¾×èÍà¢éÒÃËÑÊ
' XORvalue ÃѺ¤èÒµÑÇà¢éÒÃËÑÊ ËÃ×Í ¡Ø­á¨
' áÅФ׹¤èÒ¡ÅѺ¨Ò¡¿Ñ§¤ìªÑè¹ä»´éÇÂ
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Function Encrypt(MyData As String, XORvalue As Integer) As String
    Dim i As Integer
    
    ' ǹÃͺµÒÁ¨Ó¹Ç¹¢Í§¢éÍÁÙÅ·Õèà¢éÒÃËÑÊ
    For i = 1 To Len(MyData)
        Encrypt = Encrypt & Chr(Asc(Mid(MyData, i, 1)) Xor XORvalue)
    Next
End Function

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' ¡ÒöʹÃËÑÊ (Decrypt) ¡çá¤è·ÓÂé͹¡ÅѺ´éÇÂÇÔ¸Õ¡ÒÃà´ÔÁ ¤èÒà´ÔÁ ...
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Function Decrypt(MyData As String, XORvalue As Integer) As String
    Dim i As Integer
    
    ' ǹÃͺµÒÁ¨Ó¹Ç¹¢Í§¢éÍÁÙÅ·Õè¶Í´ÃËÑÊ
    For i = 1 To Len(MyData)
        Decrypt = Decrypt & Chr(Asc(Mid(MyData, i, 1)) Xor XORvalue)
    Next
End Function