Design of double-cross-based smartphone unlock mechanism

Due to the advanced features, smartphones have become an essential and widely adopted electronic device around the world, which can provide various benefits, such as online shopping, e-commerce payment, making friends via social media, email checking and more. Such devices make people's work and life more convenient and flexible, but how to secure the locally stored phone data is a big problem. With more sensitive or private data stored on these portable devices, there is a significant demand to safeguard smartphones from unauthorized access. Currently, one of the most straightforward and intuitive approaches is to implement an unlock mechanism that asks users to input a correct unlock pattern for authentication, e.g., Android unlock patterns. However, such unlock mechanism can be easily compromised when the unlock pattern is leaked. In this work, we advocate that combining behavioral features with unlock mechanisms is a promising solution, and propose a double-cross-based unlock scheme, called Double-X, which requires users to unlock the device by inputting two cross shapes on the selected dots. For authentication, users have to re-input the selected dots and draw the cross shapes. In the evaluation, we conduct two user studies with 100 participants in total to explore and validate the scheme performance, as compared with two similar unlock schemes. The experimental results indicate that under our scheme, users can reach good success rates with better feedback.