Abstract: A method and system for reading a security seal having a unique far-field pattern are described. Periodic nano-structure is generated on the surface of a substrate having spacings of hundreds of nanometers, or smaller, and affixed on a product, or generated directly onto the product. A laser beam having a wavelength longer than the periodic spacings directed onto at least a portion of the surface of the substrate at a chosen angle of incidence and a selected azimuthal angle relative to a chosen direction produces a unique far-field pattern that may be imaged by a digital image detector disposed at a chosen distance from the illuminated region, compared with a stored reference, and validated. The nanoscale sub-wavelength patterns can be printed using extreme ultraviolet light and read with readily available visible or ultraviolet light. The security seal contains a pattern that is invisible to the eye and to an optical microscope.