Information Hiding Using a Coded Aperture as a Key

This paper proposes a visual information hiding technique using coded apertures as a key. In general, a watermark embedded as high-frequency components is difficult to extract if it is captured outside of the focal rength and defocus blur occurs. Installation of a coded aperture (CA) into the camera is a simple solution to mitigate the difficulty and several attempts are conducted to make better design for stable extraction. To the contrary, our motivation is to design a specific CA as well as information hiding scheme, where secret information can be decoded only if an image with hidden information is captured with the key aperture whose characteristic is matched with the information hiding scheme. The proposed technique designs the key aperture patterns and information hiding scheme through evolutionary multi-objective optimization so as to minimize the decryption error of a hidden image when using the key aperture while minimizing the accuracy when using other apertures. Experimental results have shown that the proposed information hiding technique was more secure than a password-based system which uses case-insensitive eight alphanumeric characters.