Design, implementation, and assessment of a usable multi-biometric continuous authentication system

Authentication mechanisms typically verify the user identity only at login, or with tedious explicit authentication requests that improve security at the expense of usability. However, especially for critical systems, workstations have to be tightly and continuously secured in order to prevent unauthorised interventions. Recent researches envisage multi-biometric systems for continuous authentication, where biometric traits are acquired transparently to the user and authentication is provided without requiring explicit actions. In this work we propose a multi-biometric authentication system that continuously and transparently verifies the user identity through face, fingerprint and keystroke recognition. This paper presents the design, prototype implementation and assessment of our system. We evaluate the system usability and its trade-off with security in an experiment involving 60 users. Our findings show that security enhancements are provided and users: 1) perform the actions without additional effort; 2) largely accept the authentication system, which only requires minimal training.