Upcoming mobile devices will have flexible displays, allowing us to explore new forms of user authentication. On flexible displays, users interact with the device by deforming the surface of the display through bending. In this thesis, we present a new type of user authentication that uses bend gestures as its input modality.

We ran three user studies to evaluate the usability and security of our new authentication scheme and compared it to PINs on a mobile phone. Our first two studies evaluated the creation and memorability of bend passwords and PINs. The third study looked at the
security problem of shoulder-surfing passwords on mobile devices.

Our results show that bend passwords are a promising authentication mechanism for flexible display devices. We also provide eight design recommendations for implementing bend passwords on flexible display devices, based on our results.