Hiding a picture in two pictures

We present a simple and efficient method capable of hiding a picture in two pictures, which we refer to as the picture hiding scheme. The proposed scheme generates two new pictures given two different original pictures and a secret picture. These two different original pictures are arbitrary, and the secret picture presents confidential information. The meanings of three pictures are not related to each other. An image defined as the secret picture can be recognized through the human visual system only when one of these two new pictures superposes on another new picture directly. This superposing process can be accomplished with two slides, therefore, no computation is performed. Anyone who obtains only one of these two new pictures cannot generate any knowledge of the secret picture. This picture hiding scheme can be used to construct a human identification scheme, which is particularly appropriate when delicate computer devices or instruments for identification are expensive. It also can apply to resolve the watermarking problem. (C) 2001 Society of Photo-Optical Instrumentation Engineers.