Current software interfaces for entering text on touch screen devices mimic existing mechanisms such as keyboard typing or handwriting. These techniques are poor for entering private text such as passwords since they allow observers to decipher what has been typed simply by looking over the typist's shoulder, an activity known as shoulder surfing. In this paper, we outline a general approach for designing security-sensitive onscreen virtual keyboards that allow users to enter private text without revealing it to observers. We present one instantiation, the Spy-Resistant Keyboard, and discuss design decisions leading to the development of this keyboard. We also describe the results of a user study exploring the usability and security of our interface. Results indicate that although users took longer to enter their passwords, using the Spy-Resistant Keyboard rather than a standard soft keyboard resulted in a significant increase in their ability to protect their passwords from a watchful observer.
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