SMARTCOPE: Smartphone Change Of Possession Evaluation for continuous authentication

The goal of continuous smartphone authentication is to detect when the adversary has gained possession of the user's device post-login. This is achieved by triggering re-authentication at fixed, frequent intervals. However, these intervals do not take into account external information that might indicate that the impostor has gained physical access to the user's device. Continuous smartphone authentication typically relies on behavioral cues, such as hand movement and touchscreen swipes, that can be collected without interrupting the user's activity. Because these behavioral signals are characterized by relatively high error rates compared to physiological biometrics, their use at fixed intervals leads to unnecessary interruptions to the user's activity in case of a false reject, and to not recognizing the impostor in case of a false accept. To address these issues, in this paper we introduce a novel framework called SMARTCOPE: Smartphone Change Of Possession Evaluation. In this work, SMARTCOPE leverages smartphone movement signals collected during user activity to determine when the smartphone is no longer in the hands of its owner. When this occurs, SMARTCOPE triggers re-authentication. By using these signals, we are able to reduce the total number of re-authentication points while simultaneously lowering re-authentication error rates. Our analysis shows that our technique can reduce equal error rates by over 40%, from 7.8% to 4.6% using movement and keystroke features. Further, we show that SMARTCOPE can be used to transform a static (login-time) authentication system, such as face recognition, to a continuous re-authentication system, with a significant increase in security and limited impact on usability.