The present invention is directed to a method and apparatus that involves improved characterization of an object based on its surface roughness and other unique features without having to necessarily define a fixed and predetermined region of interest. In accordance with one aspect, the present invention provides a method for characterizing an object based on a pattern of the object's surface roughness. The method comprises the steps of obtaining a unique image of a feature on the surface of the object, converting the image obtained into certain electrical signals and processing the electrical signals so they are associated with the object and thereby provide a characterization of the object that is used to generate a unique identifying signature for the object.