1. A method for protecting a character entered at a graphical interface, said method comprising the steps of: generating a set of partial images that are generated from complete images of characters belonging to a character set that form a complete image of a keypad having a button-to-character assignment; displaying the partial images in said set cyclically to form a graphical keypad having the complete image; and obtaining the character of a button selected by a user on said graphical keypad using said button-to-character assignment.