Public Class Form1
    Dim ver As String = "" & _
      "ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÜabcdefghijklmnopqrstuvwxyzäöü1234567890ß!§" & _
      "%&#,.;:()=?/*-+[]{}<>\_'`´³²^°µ|" & """"
    Dim länge As Integer = 1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
 
        Dim t(0) As Integer
        Dim s(0) As Integer
        Dim x(0) As Integer
        Dim schlüssel As String = ""
        Dim txt As String = ""
        Dim xx As String = ""
 
 
        If TextBox1.Text = Nothing Then
            MsgBox("Schlüssel fehlt!", MsgBoxStyle.Exclamation, "Fehler")
        Else
 
            If ver Like Mid(TextBox1.Text, Len(TextBox1.Text), 1) Then
                MsgBox("Ungültige Zeichen!", MsgBoxStyle.Exclamation, "Fehler")
            Else
                txtzuschlüssel()
            End If
 
        End If
    End Sub
 
    Function schlüsselzuZahl(ByVal s)
        Dim schlüssel As String = TextBox1.Text
 
        Dim a As Integer = 1
        Dim b As Integer = 0
        Do Until b = Len(schlüssel)
            b = b + 1
 
            While Mid(schlüssel, b, 1) <> Mid(ver, a, 1)
                a = a + 1
            End While
            s(b) = a - 1
            a = 1
        Loop
        Return s
    End Function
    Function txttzuzahl(ByVal t)
        Dim txt As String = TextBox2.Text
 
        Dim a As Integer = 1
        Dim b As Integer = 0
        Do Until b = Len(txt)
            b = b + 1
 
            While Mid(txt, b, 1) <> Mid(ver, a, 1)
                a = a + 1
            End While
            t(b) = a - 1
            a = 1
        Loop
        Return t
    End Function
    Sub txtzuschlüssel()
        Dim s(Len(TextBox1.Text)) As Integer
        schlüsselzuZahl(s)
        Dim t(Len(TextBox2.Text)) As Integer
        txttzuzahl(t)
        Dim txt As String = TextBox2.Text
		Dim x(Len(txt)) As Integer
		Dim schlüssel As String = TextBox1.Text
		Dim a As Integer = 1
		Dim c As Integer = 1
		While a <> Len(txt) + 1
 
			If c = Len(schlüssel) + 1 Then
				c = 1
			End If
			x(a) = s(c) + t(a)
			If x(a) > 104 Then
				x(a) = x(a) - 104
			End If
			a = a + 1
			c = c + 1
		End While
        a = 1
		Dim xx As String = "ü"
		Dim b As Integer
		While a <> CInt(Len(txt) + 1)
			b = x(a)
			xx = xx + Mid(ver, b, 1)
			a = a + 1
		End While
		TextBox3.Text = Mid(xx, 2, Len(xx) - 1)
	End Sub
 
 
    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles TextBox1.TextChanged
        prüf()
        Button1_Click(Nothing, Nothing)
    End Sub
 
    Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles TextBox2.TextChanged
        prüf()
        Button1_Click(Nothing, Nothing)
    End Sub
    Sub prüf()
        If Not ver Like Mid(TextBox1.Text, länge, 1) Then
            MsgBox("EE")
        End If
    End Sub
End Class