Holographic method for encrypting and decrypting information using a

Abstract

A method using a fingerprint image as a cipher for optical encrypting and decrypting information which is presented in the form of an analogous signal. The method includes recording a Fourier hologram, the complex amplitude of the spatial grating of the hologram being a Fourier transform of the information image divided by a Fourier transform of the fingerprint image. To prepare the hologram, a full-complex spatial light modulator (SLM) may be used. The parameters of the Fourier transforms are chosen such that the optical spatial frequencies of the information image and the cipher lie in the same physical range. In another embodiment, the intensity distribution of the Fourier spectrum of the fingerprint image is captured. The cipher image is obtained by illuminating a phase-only SLM which is addressed with a function derived from this intensity distribution. The hologram may be amplitude or phase; thin, thick or volume; transparent or reflective; prepared optically or computer-generated. The hologram is attached to a substrate, such as a personal card. To decrypt the information, an individual places the same fingerprint has been used as the cipher onto an input device, and the hologram is illuminated by an optical beam modulated with characteristics of the fingerprint image.