Mobile devices pose different security risks than traditional
computers and require alternative security measures.
For example, the small size and mobile nature
of handheld devices increase the risk of loss or theft. Yet unattended in public places, 89% of people who found the
phones attempted to access the phone owner’s private information.
Use of a password to unlock the device screen
protects against unauthorized user access. Yet password entry
is likely to be an obstacle for blind users, since even
sighted users find password entry on small touch screens to
be a major frustration [14]. Moreover, screen readers introduce
a severe vulnerability by speaking touched keys during
password entry (see Figure 1). Over the past decade, the
security community has explored the use of graphical authentication
techniques as an alternative to alphanumeric
passwords [16, 21, 25, 26]. These techniques do not require
text entry but are inaccessible to blind people