[Zope] How to generate an Object ID automatically

dear zopists, im a zope newbie and i have one of those little problems ppl like me can spend hours on ... i just built my first ZClass and now im trying to automatically assign a generated ID to an instance of this class in the -add method. i want to generate the id because there is no unique fieldvalue available and i dont want to have the users get stuck on this point. another problem i encountered is that when i try to add an instance in a folder i get an authentication box where no valid login is accepted i would really much apreciate if someone could help. Francisco (chico) Webber