Screen-camera communication has attracted considerable attention as a form of visible light communication (VLC) using commercial-off-the-shelf devices. Nonetheless, the security of screen-camera communications in mobile applications has largely been disregarded, despite the fact that information displayed on an open screen is easily intercepted. One-way communication systems also make it difficult to add security features. In this paper, we propose a secure screen-camera communication system in which a visual encryption algorithm is designed to camouflage transmitted images between the screen and camera. When the targeted receiver holds a camera in a designated viewing position (ie, directly in front of the screen at a distance of 50cm), the camouflaged image is revealed due to aliasing effect. From any other position, only the camouflaged image can be seen.