An inhomogeneous, optically active medium with optically active components, such as, an ink with reflective flakes or a gemstone dust, is included on or embedded in one or more portions of a workpiece. When the portions are illuminated with visible and/or ultraviolet light, the components, which are also anisotropic, provide readily detectable information that can be extracted for a string which is included on or associated with an indicium that is used to authenticate the workpiece. To verify the workpiece, the one or more portions that contain the optically active medium are again illuminated, and the string is then newly generated from various images of the appearances of the components. The newly generated string or, as appropriate, an indicium that is based on the string is then compared with a string or an indicium that is imprinted on or associated with the workpiece. If the previously and newly generated strings or indicium correspond, the workpiece is determined to be authentic. Otherwise, the workpiece is deemed to be a counterfeit.