Public Class Form1
    Public Function encrypt(ByVal s As String, ByVal v As Long) As String
        Dim total As String
        Dim tmp As String
        For i = 1 To Len(s)
            tmp = Mid(s, i, 1)
            tmp = Asc(tmp) + v
            tmp = Chr(tmp)
            total = total & tmp
        Next i
        encrypt = total
    End Function
    Public Function decrypt(ByVal s As String, ByVal v As Long) As String
        Dim total As String
        Dim tmp As String
        For i = 1 To Len(s)
            tmp = Mid(s, i, 1)
            tmp = Asc(tmp) - v
            tmp = Chr(tmp)
            total = total & tmp
        Next i
        decrypt = total
    End Function
    Private Sub Button1_click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        text1.Text = encrypt(text1.Text, 3)
    End Sub
    Private Sub Button2_click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        text1.Text = decrypt(text1.Text, 3)
    End Sub
End Class
