“…Authentication can be performed via fixed-text analysis (i.e., with the user typing some predetermined text) [7,13,20,25,28,31,32,36,42,46] or via free-text analysis (i.e., with the user typing freely on the keyboard) [14,41]. Keystroke dynamics techniques have been explored for a broad range of devices, equipped with either hardware [26,29] or software (also called "soft") keyboards [56]-with recent work on mobile devices largely falling into the latter category [23,55,56]. While different classes of keyboards (i.e., hardware vs. software, numeric vs. alphabetic, etc.)…”