In this paper we propose and evaluate new graphical password
schemes that exploit features of graphical input displays to achieve
better security than text-based passwords. Graphical input devices
enable the user to decouple the position of inputs from the
temporal order in which those inputs occur, and we show that this
decoupling can be used to generate password schemes with substantially
larger (memorable) password spaces. In order to evaluate the security
of one of our schemes, we devise a novel way to capture a subset of the
``memorable'' passwords that, we believe, is itself a contribution.
In this work we are primarily motivated by devices such as personal
digital assistants (PDAs) that offer graphical input capabilities via
a stylus, and we describe our prototype implementation of one of our
password schemes on such a PDA, namely the Palm Pilot
.