Execution Time Prediction for 3D Interactive CAPTCHA by Keystroke Level Model

CAPTCHA is a standard defense system which stands for completely automated public turing test to tell computers and human apart. The basic idea of CAPCHA is providing questions that human users can easily recognize and answer but computer programs cannot. In this study, an interactive 3D CAPTCHA was introduced, and developed for better security. The design and evaluation phases are presented in detail. The proposed model passed the necessary security tests. The keystroke level model (KLM) can be used to evaluate and predict task execution time for a specific system usage scenario. KLM is based on calculation on the sequences of the users' tasks or actions. This study attempts to estimate execution times for 3D animated CAPTCHA by KLM. An interactive CAPTCHA method is developed by Flash Movie Technology which is used commonly in the Web sites. The results show that performing the 3D CAPTCHA requires a serious amount of time. New interaction methods should be considered to improve the users' performance.