You may have read that it is impossible to mate a used Smartkey fob (i.e. "Ebay fob") with your Prius and have full Smart Key functionality unless you take it to the dealer or locksmith. If you have access to Techstream software along with an appropriate interface like the $500 Mongoose MFC cable, you can do it yourself by paying an online service to calculate the one-time passcode from the seed that Techstream supplies. Calculation of Passcode for Toyota, Lexus, Scion vehicles - Service The place is in Europe (Lithuania). They charge 20 Euros for each passcode calculated (around $28) They are open USA morning business hours and do it via PayPal/email within a few minutes. Easy peasy if you only need to do it once in a while. If you have to calculate seeds regularly, (i.e. you're a locksmith) they will sell you the software for 800 Euros which works on many makes and models of cars.