Mod cars are mostly computerized and equipped with passive keyless entry and start (PKES) system.PKES is based on Radio Frequency Identification (RFID) technology for authentication of the authorized drivers.RFID technology has replaced the conventional ways of identification and authorization in order to facilitate users while introducing new security challenges.In this article,we focused on verifying the presence of authorized key in the physical proximity of car by employing multiple antennas.Application of multiple antennas to the currently developed cryptographic algorithms opens a new approach for researchers to improve security of RFID based systems.We propose an advanced security system for PKES using multiple antennas wherein an authorized key passes through multiple vicinities to allow driver to access and start the car.Furthermore,we modified a light-weight cryptographic protocol named as HB (Hopper and Blum) protocol to integrate it with the proposed design based on multiple antennas.Simulation results show improvement in security functionality while keeping in view the efficiency constraints.