Description: Discretization is used in click-based graphical passwords so that approximately correct entries can
be accepted by the system. We show that the existing discretization scheme of Birget et al. (2006) allows
for false accepts and false rejects because the tolerance region is not guaranteed to be centered on the
original click-point, causing usability and security concerns. Using empirical data from a large user
study, we show that this is a significant issue in practice. We then introduce Centered Discretization, a
simpler discretization method that eliminates false accepts and false rejects. It also allows for smaller
tolerance regions without impacting the usability of the system.
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(good)Centered Discretization with Application to Graphical Passwords.pdf