Developing Visual Cryptography for Authentication on Smartphones

Visual cryptography scheme (VCS) is a kind of cryptography that can be directly decoded by human visual system when transparent films are stacked. It requires no computation for decryption and can be stored in physical materials such as films. Therefore VCS can be a basis for providing secure and dependable authentication scheme, because it cannot be harmed by electronic and/or computational tricks. In this paper, we develop VCS for authentication on smartphones. Several authentication schemes using VCS are designed. Image quality of VCS is an inevitable issue because of small display areas of mobile devices. Thus, we will deal with VCS for continuous-tone images (gray-scale images and color images) that can enhance the image quality of VCS, so that feasible authentication schemes for smartphones will be achieved by using this continuous-tone VCS. Our authentication scheme can avoid the inconvenience of using password everywhere in modern digital life, and also resists attacks from hackers and the man-in-middle attack. This type of authentication using VCS may have a huge impact on future authentication schemes for mobile devices.