  Mobile devices have become an indispensable component of modern life. Their
high storage capacity gives these devices the capability to store vast amounts
of sensitive personal data, which makes them a high-value target: these devices
are routinely stolen by criminals for data theft, and are increasingly viewed
by law enforcement agencies as a valuable source of forensic data. Over the
past several years, providers have deployed a number of advanced cryptographic
features intended to protect data on mobile devices, even in the strong setting
where an attacker has physical access to a device. Many of these techniques
draw from the research literature, but have been adapted to this entirely new
problem setting.
  This involves a number of novel challenges, which are incompletely addressed
in the literature. In this work, we outline those challenges, and systematize
the known approaches to securing user data against extraction attacks. Our work
proposes a methodology that researchers can use to analyze cryptographic data
confidentiality for mobile devices. We evaluate the existing literature for
securing devices against data extraction adversaries with powerful capabilities
including access to devices and to the cloud services they rely on. We then
analyze existing mobile device confidentiality measures to identify research
areas that have not received proper attention from the community and represent
opportunities for future research.
