MOBILE DEVICE AND AUTHENTICATION SYSTEM

A mobile device for an authentication system that performs authentication to control an authentication target with code verification via near field wireless communication, includes: an acceleration sensor; a communication portion that performs the near field wireless communication with an antenna of the authentication target; a reception stop portion that stops reception operation of the communication portion; a fault detection portion that detects a failure in the acceleration sensor; and an operation change portion that prevents the reception stop portion from stopping the reception operation.