Originally Posted by pinky_and_me
The factory has to program the car code in the key so that the car would trust the key and add it to it's list of accepted keys (which is the auto programming part people talk about).
If what you suggest actually worked then I could break a window, put a blank key and drive off.
Off topic, but no, you would need 1 keyfob original (already programmed to the car) present. So you need the car, 1 original keyfob and 1 new keyfob to program. Look, we can argue all day here, but the fact is all car makers have autoprogramming of some sort built into their cars.