Method for preventing relay attack on vehicle smart key system

A method for preventing a relay attack of a smart key system for a vehicle, the method comprising:

• receiving, by a fob key configured to be carried by a user, a challenge signal applied from a smart key (SMK) unit installed in a vehicle;
• transmitting, by the fob key, a response signal including an encoding code to the SMK unit after the receiving the challenge signal;
• receiving, by the SMK unit, the response signal after the transmitting the response signal;
• detecting a noise signal included in the response signal received by the SMK unit after the receiving the response signal;
• and
• controlling operation of various functional units installed in the vehicle according to a decoding result based on the detecting the noise signal,
• wherein the noise signal is generated on account of a first repeater and a second repeater positioned between the SMK unit and the fob key, wherein the second repeater is positioned closer to the fob key than the first repeater,
• wherein the noise signal is a signal, which is transmitted for the purpose of being transmitted to the fob key from a transmission antenna of the second repeater and directly received in a reception antenna of the second repeater without passing through the fob key, and
• wherein the controlling operation of the various functional units includes blocking an operation of the various functional units installed in the vehicle to prevent a relay attack when the response signal received in the SMK unit includes the noise signal.