Effect of User Posture and Device Size on the Performance of Touch-Based Authentication Systems

Touch dynamics is a behavioral biometric that authenticates users by analyzing the characteristics of the touch gestures they execute on devices such as tablets and smartphones. The current research in this field has focused on identifying the best algorithms and the most effective attributes to improve authentication performance. However, a robust touch dynamics based authentication system for mobile devices must also be resilient against environmental variables such as user posture, movement, device size, device manufacturer, etc. In this work, we focus on two critical environmental variables that affect touch based authentication systems. We demonstrate that the user's posture and device size have a significant impact on the performance of touch based authentication systems. Our results indicate that authentication performance is proportional to the device size. Furthermore, we conclude that using a device's 3-D orientation is necessary to attain better authentication performance. Our findings indicate that the features used in state-of-the-art touch-based authentication systems are insufficient to provide constant, reliable performance when either the device size or user posture change. The effect of environmental variables on touch dynamics has not been explored. The results presented in this work are the first of its kind and important in the development of robust touch-based authentication systems. This study has immediate, applicable benefits to develop better authentication approaches touch dynamics.