Public Class Form1

    Private Sub ListBox3_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)

    End Sub

    Private Sub btnenkripsi_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnenkripsi.Click
        Dim a As String = ""
        Dim xkalimat As String = ""
        For i = 1 To Len(plain.Text)
            a = Mid(plain.Text, i, i)
            a = Chr(Asc(a) - 3)
            xkalimat = xkalimat + a
        Next
        chiper.Text = xkalimat
    End Sub

    Private Sub btndeskripsi_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btndeskripsi.Click
        Dim a As String = ""
        Dim xkalimat As String = ""
        For i = 1 To Len(chiper.Text)
            a = Mid(chiper.Text, i, i)
            a = Chr(Asc(a) - 3)
            xkalimat = xkalimat + a
        Next
        plain.Text = xkalimat
    End Sub
End Class