Substrate/document authentication using randomly dispersed dielectric components

Abstract

A document verification scheme embeds in or deposits on a substrate/document a random distribution of dielectric particles that effectively create a unique electronically detectable signature. The dielectric constant of the particles is sufficiently larger than that of the substrate/document, so as to exhibit molecular level electric dipole moments, which cause a detectable modification of an external electric field passing through the substrate. Electronic signature verification is effected by comparing the digitized output of an electric field modification sensor with a digital code that has been stored previously in the data base. As long as the substrate containing the dielectric particle signature has not been altered, its randomly distributed capacitance characteristic will remain unchanged, and the two digital signatures seen by the comparator will effectively match one another, verifying authentication of the substrate. However, alteration of the substrate and thereby the particle distribution will modify the capacitance characteristic associated with the randomly distributed particles and cause the comparator to be presented with two diverse digital signatures—indicating tampering.