recording devices like smartphones, Life-logging
cameras and Google Glass are carried by their users
virtually around the clock. While these devices enable
transformative new applications and services, they
also introduce entirely new threats to users' privacy,
because they can capture a complete record of the
user's location, online and offline activities, and social
encounters, including an audiovisual record. Such
a record of users' personal information is highly
sensitive and is subject to numerous privacy risks.
In this thesis we address two specific contexts in which
this problem arises, which are: 1) risks to users'
personal information introduced by a popular class
of apps called mobile social apps, 2) privacy risks
due to ubiquitous digital capture, where bystanders
may inadvertently (and/or against their wishes) be
captured in photos and video recorded by other nearby
users. Both the solutions aim at putting the user
back in control of what personal information is being
collected and shared, while enabling innovative new
applications.