Optical encryption and decryption method and system

Abstract

The invention relates to securing of information utilising optical imaging technologies and more specifically to phase encryption and decryption of images. An image is encrypted into a mask having a plurality of mask resolution elements (X, Y) by encoding the image using e.g. a phase mask with an encoded phase value φ (X, Y) and an encoded amplitude value a (X, Y), and by further encrypting the mask (using e.g. a spatial light modulator) by addition of an encrypting phase value φ(X, Y) to the encoded phase value φ (X, Y) and by multiplication of an encrypting amplitude value a(X, Y) with the encoded phase value a (X, Y). The method of decrypting comprises the steps of decrypting the mask by radiating electromagnetic radiation towards the mask and inserting into the path of the electromagnetic radiation a complex spatial electromagnetic radiation modulator comprising modulator resolution elements, the decrypting phase value φ(X, Y) and the decrypting amplitude value a(X, Y) respectively, of a modulator resolution element (X, Y) being substantially equal to −φ(X, Y) and a(X, Y).