Over at Wired, Andy Greenberg reports that security researchers have discovered how to use software defined radio (SDR) to remotely unlock hundreds of millions of cars. The findings are to be presented at a security conference later this week and detail two different vulnerabilities.

The first affects almost every car Volkswagen has sold since 1995, with only the latest Golf-based models in the clear. Led by Flavio Garcia at the University of Birmingham in the UK, the group of hackers reverse-engineered an undisclosed Volkswagen component to extract a cryptographic key value that is common to many of the company's vehicles.

Alone, the value won't do anything, but when combined with the unique value encoded on an individual vehicle's remote key fob—obtained with a little electronic eavesdropping, say—you have a functional clone that will lock or unlock that car.

VW has apparently acknowledged the vulnerability, and Greenberg notes that the company uses a number of different shared values, stored on different components.

The second affects many more makes, "including Alfa Romeo, Citroën, Fiat, Ford, Mitsubishi, Nissan, Opel, and Peugeot," according to Greenberg.

It exploits a much older cryptographic scheme used in key fobs called HiTag2. Again it requires some eavesdropping to capture a series of codes sent out by a remote key fob. Once a few codes had been gathered, they were able to crack the encryption scheme in under a minute.

Similar techniques have been linked to a number of car thefts, including most recently in Houston. It seems the power of 1990s-era automotive-grade encryption is helpless in the face of $40 Arduinos and SDR.