A method of, and a system and a label for, authenticating an object in situ create an authentication pattern signature for the object to be authenticated, associate a random distribution of multiple, three-dimensional elements with the object, aim a portable, handheld, image capture device at the object to capture return light from the elements as a single image, verify from the single image that the elements are three-dimensional, process the single image to generate an image pattern of the elements, compare the image pattern with the authentication pattern signature, and indicate that the object is authentic when the image pattern matches the authentication pattern signature.