Image hiding with computer-generated phase codes for optical authentication

An image hiding technique with computer-generated phase codes is presented. Unlike the techniques proposed previously, this method transforms the hidden image into an original host image and makes it be a complex function, whose amplitude closely resembles the original host. Computer simulations show that this hiding technique is fragile, that is, sensitive to manipulations such as amplitude and phase extraction, amplitude and phase replacement, scratching, occluding part of the marked image and filtering. Therefore, this technique is appropriate for applying in authentication because introducing such manipulations to the hidden image may result in false authentication. Thus, forged credentials or identity cards can be verified confidently. Quantization effects of the computer-generated phase distributions to the revealed quality are also discussed. (C) 2004 Elsevier B.V. All rights reserved.