DescriptionIn this thesis, we study authentication on mobile devices by performing simple taps on the touchscreen. First, we have replicated a previously proposed system Pass- Chords - a tap based authentication system. Based on the lessons learned, we present an improved system called Pianotaps, which theoretically provides an orders of mag- nitude larger password space. We conducted a preliminary informal user study of PassChords, Pianotaps and PINs towards understanding the bene ts and drawbacks of these approaches. Our results indicate that Pianotaps provides enhanced security over shoulder sur ng attacks while also being faster to authenticate with.