It wouldn't stop anything. You have a car that has everything it needs to start and go just sitting there. Whether you have a physical key, password, retina sca

It wouldn't stop anything. You have a car that has everything it needs to start and go just sitting there. Whether you have a physical key, password, retina scanner, you name it the issue is that the thief has physical access. For physical security they can just short some wires to make the car think it has the key, and for digital systems they gain access to the cleartext internal message bus of the car and tell it to start. The latter is the one that has more promise on making it actually secure because you can make the software required to drive the car and the car physically can't move without it but that comes with a lot of usability and performance trade-offs.