A simple gesture control system that permits accurate, simple, and secure input of personal identification numbers (PIN) by visually impaired or blind persons at a payment terminal or automatic teller machine is provided. By the user interface, invisible keys can be selected by simple wiping gestures. Here, any necessity for visual or spoken feedback or localization of operating elements is rendered unnecessary. As a result, blind or visually impaired users can input a secret number by touch operation automatically and without outside help. In this way, account is also taken of the statutory requirements in different countries.