Modeling Thermal Sequence Signal Decreasing for Dual Modal Password Breaking

The thermal camera records trace of users' touch a while after they type in the password. People's password may be stolen through a thermal camera due to this phenomenon. In this paper, we model the procedure of the thermal sequence from the view point of physical process. Based on the Newton's Law of Cooling, we set up a physical model to describe the process of the keys' temperature decreasing. Then the model is used to estimate keystroke time instants by maximizing likelihood function method. We estimate the password after getting keystroke time instants of each key. The possibility that cheaters have to steal people's password is also explored in the experiment. Based on our findings in the experiment, we give several pieces of practical advice for people to protect their password.