There was a pretty good talk at 29C3 about side-channel analysis and how it can break secret keys of wireless devices and smartcards. [1]

With knowledge of cryptanalysis and lots of free time I think it's conceivable that someone could have cracked the system. I wonder if car companies test their crypto very rigorously?

1. https://www.youtube.com/watch?v=Y1o2ST03O8I