Various attacks may disclose sensitive information such as passwords of mobile devices. Residue-based attacks exploit oily or heat residues on the touch screen, computer vision based attacks analyze the hand movement on a keyboard, and sensor based attacks measure a device's motion difference via motion sensors as different keys are tapped. A randomized soft keyboard may defeat these attacks. However, a randomized key layout is counter-intuitive and users may be reluctant to adopt it. In this paper, we introduce a novel and intuitive input system, secure finger mouse, which uses a mobile device's camera sensing the fingertip movement, moves an on-screen cursor and performs clicks by sensing click gestures. We design a randomized mouse acceleration algorithm so that the adversary cannot infer keys clicked on the soft keyboard by observing the finger movement. The secure finger mouse can defeat attacks including residue, computer vision and motion based attacks too. We perform both theoretical analysis and real-world experiments to demonstrate the security and usability of the secure fingertip mouse.
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