Abstract: A method of car access includes receiving a localization secret at data processing hardware. The localization secret defines a portion of vehicle authentication information for a vehicle. The method also includes receiving at least one localization frame from a mobile device at the data processing hardware. The at least one localization frame includes identification information for the mobile device. The method further includes determining, by the data processing hardware, whether the at least one localization frame includes a derived localization secret. The derived localization is defined by the localization secret. The method further includes, when the at least one localization frame includes the derived localization secret, supplying, by the data processing hardware, power to a vehicle control module of the vehicle and authentication information to the vehicle control module of the vehicle.