| 摘要 |
PROBLEM TO BE SOLVED: To prevent a relay attack more surely.SOLUTION: An on-vehicle machine 10 transmits a challenge signal synchronized with an RF clock of an RF band having a higher frequency than an LF signal at a first transmission timing t1 prescribed based on the RF clock, determines whether or not a time interval t1+t2 from the transmission of the challenge signal to the reception of a response signal transmitted by a portable machine 20 in response to the reception of the challenge signal is within a proper range prescribed based on the RF clock, and permits a predetermined operation on a vehicle in a case in which the time interval t1+t2 is within the proper range. |
