Squeez'In: Private Authentication on Smartphones based on Squeezing Gestures

In this paper, we proposed \emph{Squeez'In}, a technique on smartphones that enabled private authentication by holding and squeezing the phone with a unique pattern. We first explored the design space of practical squeezing gestures for authentication by analyzing the participants' self-designed gestures and squeezing behavior. Results showed that varying-length gestures with two levels of touch pressure and duration were the most natural and unambiguous. We then implemented \emph{Squeez'In} on an off-the-shelf capacitive sensing smartphone, and employed an SVM-GBDT model for recognizing gestures and user-specific behavioral patterns, achieving 99.3\% accuracy and 0.93 F1-score when tested on 21 users. A following 14-day study validated the memorability and long-term stability of \proj. During usability evaluation, compared with gesture and pin code, \emph{Squeez'In} achieved significantly faster authentication speed and higher user preference in terms of privacy and security.