I do not want a vehicle with the ability to communicate with another vehicle. It will be a Hacker's wet dream coming true. Given the number of hackers available and their propensity to collaborate on complex issues it will only be a matter of months if not weeks before the whole house of cards is compromised. Do you really want to see what hackers can conjure up for a doomsday exploit on automobiles?
This system of encrypted key acknowledgement may be a very good solution to expensive anti-theft systems. Not just that, in the event of a car window smash, the car would only start if the VR system of the car (since we are readily talking about IOT) recognises the voice of the driver of the car. If a car is stolen via other means (like we see in Gone in Sixty Seconds) then the car should have a basic security that wouldn't let any unknown entity inside the car start it even by using chords and cables under the dashboard.
@wcmoore: But automated cars would be zooming out of vision pretty soon, and they would be connected to a cloud using a dashboard interface. So even if your car doesn't support peer-to-peer communication, even then it is at risk of being hacked, since a cloud can go down anytime and systems may be breached.
@junko: secure pairing and then data linking could do well enough with current generation of cars, but OEMs are looking at a long time solution, a solution that won't be much modified for at least half a decade. It is true that BLE's security is getting increasingly weaker with time, and a day won't be far when bypassing BLE data linking would be a piece of cake.