deTritemius

Function deTrithemius(ByVal str As String) As String
 
        Dim res As String = ""
        Dim table As String = "ABCDEFGHIJKLMNÑOPQRSTUVWXYZ"
        Dim i As Integer = 0
 
        Dim pos As Integer
 
        For Each c As Char In str
            If c <> " " Then
                pos = InStr(table, UCase(c)) - i
 
                While pos < 0
                    pos += Len(table)
                End While
 
                res = res & Mid(table, pos, 1)
                i += 1
            Else
                res = res & " "
            End If
 
        Next
        Return res
    End Function