The present invention relates to a method for preventing security breaches of a passive remote keyless entry system for authorizing access to a vehicle. The passive remote keyless entry system comprises a base station located at the vehicle and a mobile device, in particular a remote key, wherein the base station comprises a first processor unit and a first transceiver unit, the first transceiver unit comprises a timing device, the mobile device comprises a second processor unit and a second transceiver unit, an air travel time T of a single message sent back and forth from the base station to the mobile device is measured, and access to the vehicle is granted depending on the measured air travel time T.