Biblio

Applications in mobile marketplaces may leak private user information without notification. Existing mobile platforms provide little information on how applications use private user data, making it difficult for experts to validate appli- cations and for users to grant applications access to their private data. We propose a user-aware-privacy-control approach, which reveals how private information is used inside applications. We compute static information flows and classify them as safe/un- safe based on a tamper analysis that tracks whether private data is obscured before escaping through output channels. This flow information enables platforms to provide default settings that expose private data for only safe flows, thereby preserving privacy and minimizing decisions required from users. We build our approach into TouchDe- velop, an application-creation environment that allows users to write scripts on mobile devices and install scripts published by other users. We evaluate our approach by studying 546 scripts published by 194 users, and the results show that our approach effectively reduces the need to make access-granting choices to only 10.1 % (54) of all scripts. We also conduct a user survey that involves 50 TouchDevelop users to assess the effectiveness and usability of our approach. The results show that 90 % of the users consider our approach useful in protecting their privacy, and 54 % prefer our approach over other privacy-control approaches.

Data confidentiality can be effectively preserved through encryption. In certain situations, this is inadequate, as users may be coerced into disclosing their decryption keys. Steganographic techniques and deniable encryption algorithms have been devised to hide the very existence of encrypted data. We examine the feasibility and efficacy of deniable encryption for mobile devices. To address obstacles that can compromise plausibly deniable encryption (PDE) in a mobile environment, we design a system called Mobiflage. Mobiflage enables PDE on mobile devices by hiding encrypted volumes within random data in a devices free storage space. We leverage lessons learned from deniable encryption in the desktop environment, and design new countermeasures for threats specific to mobile systems. We provide two implementations for the Android OS, to assess the feasibility and performance of Mobiflage on different hardware profiles. MF-SD is designed for use on devices with FAT32 removable SD cards. Our MF-MTP variant supports devices that instead share a single internal partition for both apps and user accessible data. MF-MTP leverages certain Ext4 file system mechanisms and uses an adjusted data-block allocator. These new techniques for soring hidden volumes in Ext4 file systems can also be applied to other file systems to enable deniable encryption for desktop OSes and other mobile platforms.

To keep malware out of mobile application markets, existing techniques analyze the security aspects of application behaviors and summarize patterns of these security aspects to determine what applications do. However, user expectations (reflected via user perception in combination with user judgment) are often not incorporated into such analysis to determine whether application behaviors are within user expectations. This poster presents our recent work on bridging the semantic gap between user perceptions of the application behaviors and the actual application behaviors.