Some embodiments of the present invention include a method of differentiating touch screen users based on characterization of features derived from the touch event acoustics and mechanical impact and includes detecting a touch event on a touch sensitive surface, generating a vibro-acoustic waveform signal using at least one sensor detecting such touch event, converting the waveform signal into at least a domain signal, extracting distinguishing features from said domain signal, and classifying said features to associate the features of the domain signal with a particular user.