Authentication system and method

An authentication system using a correlator that correlates an input (84) with a reference (88) wherein at least one of the input and reference comprises a phase volume mask having structures that are each less than about six microns in size and can have an aspect ratio (AR) greater than 1:1 so as to produce a phase encoded random pattern having millions of combinations in a mask that is as small as one square millimeter. The random pattern can be convolved with a second pattern, such as a biometric pattern, to produce a phase convolved mask. The correlator (82) preferably is a nonlinear joint transform correlator that can use "chirp" encoding. The correlator optically Fourier transforms (98) images of the reference and input that are thereafter nonlinearly transformed and inverse Fourier transformed by a processor (104) to determine authenticity (106, 110). A spatial light modulator (SLM) can be used as an input or reference.