As part of my exchange with the University of Montreal, I implemented a visual cryptographic system (supervised by Pierre Poulin). The project is an identification system using transparent cards that must be placed on the screen to reveal a secret drawing. It includes two applications: a key generator (transparent cards to print) and the login application itself. The sources are available in the documentation and explanations and references are found in the project paper (PS and PDF).
The main idea of the project is based on the results shown by Douglas Stinson on his page dedicated to the visual cryptography: http://cacr.uwaterloo.ca/~dstinson/visual.html
For more information on this project, as well as the original paper in PDF, please see (in French):