| 摘要 |
In this portable terminal device authenticating system: an on-board device transmits a request signal including a plurality of authentication signals having different signal intensities; a portable terminal device receives the request signal, discriminates between the plurality of authentication signals on the basis of the signal intensities of the plurality of authentication signals included in the request signal, measures, for each of the discriminated authentication signals, the reception time of the authentication signal, and transmits, to the on-board device, an answer signal including information indicating the measured reception times; and the on-board device determines whether or not a received signal includes information indicating the reception times of the authentication signals, and determines, when the received signal includes information indicating the reception times, whether or not the received signal is the answer signal from the portable terminal device on the basis of the information indicating the reception times of the authentication signals. |
