  Screen lock is a critical security feature for smartphones to prevent
unauthorized access. Although various screen unlocking technologies, including
fingerprint and facial recognition, have been widely adopted, they still have
some limitations. For example, fingerprints can be stolen by special material
stickers and facial recognition systems can be cheated by 3D-printed head
models. In this paper, we propose EmgAuth, a novel electromyography(EMG)-based
smartphone unlocking system based on the Siamese network. EmgAuth enables users
to unlock their smartphones by leveraging the EMG data of the smartphone users
collected from Myo armbands. When training the Siamese network, we design a
special data augmentation technique to make the system resilient to the
rotation of the armband, which makes EmgAuth free of calibration. We conduct
extensive experiments including 53 participants and the evaluation results
verify that EmgAuth can effectively authenticate users with an average true
acceptance rate of 91.81% while keeping the average false acceptance rate of
7.43%. In addition, we also demonstrate that EmgAuth can work well for
smartphones with different screen sizes and for different scenarios when users
are placing smartphones at different locations and with different orientations.
EmgAuth shows great promise to serve as a good supplement for existing screen
unlocking systems to improve the safety of smartphones.
