Design a new visual cryptography for human-verifiable authentication in accessing a database

Visual cryptographic scheme (VCS) has an attractive property of decoding that can be performed directly by the human visual system without any computation. This novel stacking-to-see property of VCS can be secure and cheap used for visual authentication in accessing a data base. In this paper, we design a new participant-specific VCS (PSVCS) to extend the authentication scenario from a single-client authentication in VCS-based authentication schemes to a group of clients with specific threshold property. The proposed (t,k,n\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$t, k, n$$\end{document})-PSVCS, where t≤k≤n\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$t\, \le \,k \,\le\, n$$\end{document}, needs t\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$t$$\end{document} specific participants and other (k-t\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$k-t$$\end{document}) participants to decode the secret image. When compared with previous VCS-based authentication schemes, our PSVCS-based authentication can provide different privileges to clients and is more suitable for real environment.