Secure verification by multifactor optical validation

Abstract

We propose a novel multifactor encryption-authentication technique that reinforces optical security by allowing the simultaneous AND-verification of more than one primary image. We describe a method to obtain four-factor authentication. The authenticators are: two different primary images containing signatures or biometric information and two different white random sequences that act as key codes. So far, optical security techniques deal with a single primary image (an object, a signature, or a biometric signal), not combined primary images. Our method involves double random-phase encoding, fully phase-based encryption and a combined nonlinear JTC and a classical 4f-correlator for simultaneous recognition and authentication of multiple images. There is no a priori constraint about the type of primary images to encode. Two reference images, double-phase encoded and encrypted in an ID tag (or card) are compared with the actual input images obtained in situ from the person whose authentication is wanted. The two key phase codes are known by the authentication processor. The complex-amplitude encoded image of the ID tag has a dim appearance that does not reveal the content of any primary reference image nor the key codes. The encoded image function fullfils the general requirements of invisible content, extreme difficulty in counterfeiting and real-time automatic verification. The possibility of introducing nonlinearities in the Fourier plane of the optical processor will be exploited to improve the system performance. This optical technique is attractive for high-security purposes that require multifactor reliable authentication.