Dim länge As Integer
        Dim openFileDialog1 As New OpenFileDialog()
        openFileDialog1.Filter = "Alle Dateien (*.*)|*.*"
        Dim bytes() As Byte
        If openFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
            TextBox3.Text = "Baue Darstellung..." & System.IO.Path.GetFileName( _
              openFileDialog1.FileName)
            Using fs As New FileStream(openFileDialog1.FileName, FileMode.Open, _
            FileAccess.Read)
                Using reader As New BinaryReader(fs)
                    länge = fs.Length
                    bytes = reader.ReadBytes(CInt(fs.Length))
                End Using
            End Using
        End If
        ProgressBar1.Visible = True
        ProgressBar1.Maximum = länge
        ProgressBar1.Value = 0
        Dim sb As New StringBuilder(3 * bytes.Length)
        For Each b In bytes
            sb.Append(String.Format("{0:X2}", b))
            ProgressBar1.Value = ProgressBar1.Value + 1
        Next
        TextBox1.Text = sb.ToString()
        MsgBox("Einlesevorgang erfolgreich beendet", MsgBoxStyle.Information)
        ProgressBar1.Value = 1
        ProgressBar1.Visible = False

        Dim rd As New RijndaelManaged
        Dim rijndaelIvLength As Integer = 16
        Dim md5 As New MD5CryptoServiceProvider
        Dim key() As Byte
        On Error GoTo Handler
        If CheckBox1.Checked = True Then
            key = md5.ComputeHash(Encoding.UTF8.GetBytes(lafsfgb46agse5)
        ElseIf CheckBox1.Checked = False Then
            If TextBox3.Text = "" Then GoTo Handler
            key = md5.ComputeHash(Encoding.UTF8.GetBytes(TextBox3.Text))
        End If
        md5.Clear()
        Dim encdata() As Byte = Convert.FromBase64String(TextBox2.Text)
        Dim ms As New MemoryStream(encdata)
        Dim iv(15) As Byte
        ms.Read(iv, 0, rijndaelIvLength)
        rd.IV = iv
        rd.Key = key
        Dim cs As New CryptoStream(ms, rd.CreateDecryptor, _
          CryptoStreamMode.Read)
        Dim data(ms.Length - rijndaelIvLength) As Byte
        Dim i As Integer = cs.Read(data, 0, data.Length)
        TextBox1.Text = System.Text.Encoding.UTF8.GetString(data, 0, i)
        cs.Close()
        rd.Clear()