Thank you

Seems a good funcion

However it creates low level characters

I need an unlock code to my customers, so it can not
contain strange characters

In the other hand, it can not be to easy to guess

All I need is: I send my customer the serial and he
unlocks the software with a friendly password

The serial is always a 11 digits string, but this string
contains only numbers

99999999999


Moises