The increase of personal data on mobile devices has been followed by legislation that forces service providers to process and maintain users' data under strict data protection policies. In this paper, we propose a new primitive for mobile applications called auditable mobile function (AMF) to help service providers enforcing such policies by enabling them to process sensitive data within users' devices and collecting proofs of function execution integrity. We present SafeChecker, a computation verification system that provides mobile application support for AMFs, and evaluate the practicality of different usage scenario AMFs on TrustZone-enabled hardware.

In certain restrictive usage scenarios, personal mobile devices are required to operate in some constrained manner. Security concerns tend to be the most typical motivation, for example, as in "Bring Your Own Device" use cases. However, because most device configurations are strictly controlled by their respective users, today it is practically infeasible to satisfy such requirements. In this paper, we present TrUbi, a system that allows for dynamic and temporary restriction of Android devices by disabling or locking specific functions for limited amounts of time, e.g. network blocked. TrUbi enforces global security policies by implementing an OS primitive named trust lease. Our TrUbi prototype can efficiently enforce security policies in unmodified real-world apps and paves the way for new apps that are currently unsupported by existing mobile platforms.

Self-destructing messaging applications have garnered immense popularity due to the arrival of Snapchat. However, Snapchat's history has shown that building such services on modern mobile platforms is very challenging. In fact, either caused by programming errors or due to the limitations of existing mobile operating systems, in Snapchat and other similar applications it is possible to recover supposedly deleted messages against the senders' expectations, therefore leaving millions of users potentially vulnerable to privacy breaches. This paper presents ShareIff, a middleware for Android that provides an API for secure sharing and display of self-destructing messages. Using this middleware, Snapchat or any similar application, is able to encrypt the message on the sender's endpoint and send it to the recipient such that the message can be decrypted and securely displayed only on the recipient's device for the amount of time specified by the sender. ShareIff provides this property by relying on specialized cryptographic protocols and operating system mechanisms. ShareIff offers application developers a simple programming abstraction and adds marginal overheads to system and app.