A method for authenticating a connection between a user device and a vehicle includes sending, by the vehicle, a first wireless signal through a connection channel, receiving, by the vehicle, a second wireless signal through the connection channel, and acquiring, by the vehicle, a second signal strength sequence from second N continuous signal strength characteristics (PFVeh) of the second wireless signal, receiving, by the user device from the vehicle, the first wireless signal, acquiring a first signal strength sequence from first N continuous signal strength characteristics (PFUDev) of the first wireless signal, and communicating, by the user device, the first signal strength sequence to the vehicle.