A mobile device including a touch panel and a processing unit is provided. The touch panel includes one transmitting electrode and one receiving electrode. The transmitting electrode performs signal transmission using a touch-link technology, and the receiving electrode performs signal reception using the touch-link technology. The processing unit receives a message from a terminal device via the receiving electrode, and transmits an identification number to the terminal device via the transmitting electrode according to the message, so as to use the identification number for a verification on the terminal device.