One of the attacks would allow resourceful thieves to wirelessly unlock practically every vehicle the Volkswagen group has sold for the last two decades, including makes like Audi and Škoda. The second attack affects millions more vehicles, including Alfa Romeo, Citroen, Fiat, Ford, Mitsubishi, Nissan, Opel, and Peugeot.
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...they were able to extract a single cryptographic key value shared among millions of Volkswagen vehicles. By then using their radio hardware to intercept another value that’s unique to the target vehicle and included in the signal sent every time a driver presses the key fob’s buttons, they can combine the two supposedly secret numbers to clone the key fob and access to the car. “You only need to eavesdrop once,” says Birmingham researcher David Oswald. “From that point on you can make a clone of the original remote control that locks and unlocks a vehicle as many times as you want.” more
original paper