The passport chip uses Basic Access Control (BAC) to control its communications with devices attempting to read it. Essentially this means that the chip will not allow any information to be read from it until certain items of data from the passport have been passed to it (the passport number, the date of birth and the date of expiry). This makes it impossible for a criminal to remotely read a passport in your pocket, and ensures that the person reading the passport has opened the passport book to read these details before activating the app.