怎样给文件加密最安全(一种方法)？

这里提供了文件加密的一段小程序,以供大家参考.
<%@ Language = VBScript%>
<%
Response.Expires = 0

p = "abcdefg"
Set TestPWD = New CPassWord
TestPWD.EnPWD p
TestPWD.UnPWD TestPWD.ShowPWD(True)

k = TestPWD.ShowPWD(True)
l = TestPWD.ShowPWD(False)
Set TestPWD = Nothing

With Response
.Write "原文:" & p & "<br>"
.Write "加密后:" & k & "<br>"
.Write "解密后:" & L & "<br>"
End With


Class CPassWord
Private CEnPWD,CUnPWD

Private Function My_Hex(My_Hex_Source)
My_Hex = Hex(My_Hex_Source)
If Len(My_Hex) = 1 Then
My_Hex = "0" & My_Hex
End If
End Function

Private Function My_UnHex(My_UnHex_Source)
If Len(My_UnHex_Source) = 2 Then
Temp_Value = My_HexReplace(Left(My_UnHex_Source,1))
End If
My_UnHex = Temp_Value * 16 + My_HexReplace(Right(My_UnHex_Source,1))
End Function

Private Function My_HexReplace(My_HexReplace_Source)
If Asc(My_HexReplace_Source) > 64 Then
My_HexReplace = Asc(UCase(My_HexReplace_Source)) - 55
Else
My_HexReplace = Asc(My_HexReplace_Source) - 48
End If
End Function

Public Property Get ShowPWD(EnP)
‘’ 输出
If EnP Then
ShowPWD = CEnPWD
Else
ShowPWD = CUnPWD
End If
End Property

Sub EnPWD(EnPWD_Source)
if EnPWD_Source = "" then
CEnPWD = 0
Exit Sub
else
Randomize
Key = Rnd * 256
While Key = 0
Key = Rnd * 256
Wend
For i=1 To Len(EnPWD_Source)
Temp_String = Key Xor Asc(Mid(EnPWD_Source,i,1))
Crc = Crc + Temp_String
CEnPWD = CEnPWD + My_Hex(Temp_String)
Next
CEnPWD = My_Hex(Key) + StrReverse(CEnPWD) + My_Hex(Crc Mod 256)
End if
End Sub

Sub UnPWD(UnPWD_Source)
If Len(UnPWD_Source) < 6 Or Len(UnPWD_Source) Mod 2 = 1 then
CUnPWD = 0
Exit Sub
End If
Old_Key = My_UnHex(Left(UnPWD_Source,2))
Old_Crc = My_UnHex(Right(UnPWD_Source,2))
Old_String = StrReverse(Mid(UnPWD_Source,3,Len(UnPWD_Source)-4))
For i=1 To Len(Old_String) - 1 Step 2
Temp_Value = My_UnHex(Mid(Old_String,i,2))
Crc_Temp = Crc_Temp + Temp_Value
Temp_String = Temp_String + Chr(Temp_Value Xor Old_Key)
Next
If Old_Crc <> (Crc_Temp Mod 256) Then
CUnPWD = 403
Exit Sub
End If
CUnPWD = Temp_String
End Sub
End Class
%>

原文转自：http://www.ltesting.net