Double random phase encoding method using a key code generated by affine transformation

We present a 4f optical security scheme by using a key code mask generated by an affine transformation operation. The key encrypting code produced through a pseudo-random pattern generated from a source image depends on the affine transformation parameters and the iteration number that control its random properties. This procedure offers the advantage over the conventional double random phase mask encryption technique that we do not need to send the encrypting mask itself to the authorizer user, but the set of elements that leads to the construction of the key code mask.