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  Public Shared Sub EncryptFile(ByVal sSource As String, ByVal sTarget As _
    String, Optional ByVal BufferSize As Long = 4096)
        Dim ErrorHappened As Boolean = False
        Dim OldFileStream As FileStream
        Dim NewFileStream As FileStream
        Dim CrypStream As CryptoStream
    Try
        Dim key As String = "mypw"
        Dim RijndaelManaged As New RijndaelManaged
        RijndaelManaged.Key = SecurityFunctions.GetPasswordHashInBytes(key)
 
         OldFileStream = New FileStream(sSource, FileMode.Open)
         NewFileStream = New FileStream(sTarget, FileMode.Create)
 
        RijndaelManaged.GenerateIV()
        NewFileStream.Write(RijndaelManaged.IV, 0, RijndaelManaged.IV.Length)
 
          CrypStream = New CryptoStream(NewFileStream, _
            RijndaelManaged.CreateEncryptor, CryptoStreamMode.Write)
        Dim Data(BufferSize) As Byte
        Dim Buffer As Long
        Dim BufferCount As Long
        Dim FileLen As Long = OldFileStream.Length
 
        Do
            If BufferCount >= FileLen - BufferSize Then
                ReDim Data(FileLen - BufferCount)
                Buffer = OldFileStream.Read(Data, 0, FileLen - BufferCount)
                CrypStream.Write(Data, 0, Buffer)
                Exit Do
            End If
 
            Buffer = OldFileStream.Read(Data, 0, BufferSize)
            CrypStream.Write(Data, 0, BufferSize)
            BufferCount += Buffer
        Loop
 
 
        CrypStream.Close()
 
    Catch ex As Exception
        MsgBox("Fehler beim Verschlüsseln!" & vbCrLf & ex.Message)
        ErrorHappened = True
    Finally
      NewFileStream.Close()
      OldFileStream.Close()
    End Try
    If ErrorHappened Then
      My.Computer.FileSystem.DeleteFile(sTarget)
    End If
  End Sub

    Public Shared Sub DecryptFile(ByVal sSource As String, ByVal sTarget As _
      String, Optional ByVal BufferSize As Long = 4096)
        Dim ErrorHappened As Boolean = False
        Dim OldFileStream As FileStream
        Dim NewFileStream As FileStream
        Dim CrypStream As CryptoStream
    Try
        OldFileStream = New FileStream(sSource, FileMode.Open)
        NewFileStream = New FileStream(sTarget, FileMode.Create)
        Dim RijndaelManaged As New RijndaelManaged()
 
 
        Dim iv() As Byte
        ReDim iv(RijndaelManaged.IV.Length - 1)
        NewFileStream.Write(RijndaelManaged.IV, 0, RijndaelManaged.IV.Length)
        RijndaelManaged.IV = iv
 
        CrypStream = New CryptoStream(OldFileStream, _
          RijndaelManaged.CreateDecryptor( _
          SecurityFunctions.GetPasswordHashInBytes("mypw"), _
          RijndaelManaged.IV), CryptoStreamMode.Read)
 
        Dim Data(BufferSize) As Byte
        Dim Buffer As Long
        Dim BufferCount As Long
        Dim FileLen As Long = OldFileStream.Length
 
        Do
            If BufferCount >= FileLen - BufferSize Then
                ReDim Data(FileLen - BufferCount)
                Buffer = CrypStream.Read(Data, 0, FileLen - BufferCount)
                NewFileStream.Write(Data, 0, Buffer)
                Exit Do
            End If
 
            Buffer = CrypStream.Read(Data, 0, BufferSize)
            NewFileStream.Write(Data, 0, BufferSize)
 
            BufferCount += Buffer
        Loop
        CrypStream.Close()
    Catch ex As Exception
 
        MsgBox("Entschlüsselung fehlgeschlagen!" & vbCrLf & ex.Message)
        ErrorHappened = True
    Finally
        NewFileStream.Close()
        OldFileStream.Close()
    End Try
    If ErrorHappened Then
      My.Computer.FileSystem.DeleteFile(sTarget)
    End If
  End Sub