I. Introduction
As development of modern techniques, people are having higher and higher risk to leak their private information. There are many occasions where the private information can be stolen. One situation is that attackers steal passwords by peeping a person’s password input action. As shown in some movies, experienced spies can use adhesive tapes to trace the user’s most frequently used keys. After trying several combinations of these keys, the spies have good chance to break into the system. However, in real-world conditions, it can be difficult to find out the correct order of the keys within the limited time. By studying how passwords may be stolen, we can find limitations of modern techniques, thus improving digital security for the users. In this paper, we investigate the keyboard thermal dynamic and present new physical password attack methods based on thermal information obtained from analysis of infrared videos.