The Confederation of British Industry has said it is concerned about the licensing scheme being proposed, where Trusted Third Parties will handle digital signatures and hold the public keys that can unlock encrypted communications.
Using OnStar, GM car owners who sign up with RelayRides can leave the keys in the car and have renters unlock it by using a code on a smartphone, thereby saving the hassle of exchanging keys in person.
The service typically uses electronic devices and key cards to make it possible for renters to unlock cars, which ideally should be within walking distance (actual car keys should already be inside the vehicles).