Biblio
We introduce MobiCeal, the first practical Plausibly Deniable Encryption (PDE) system for mobile devices that can defend against strong coercive multi-snapshot adversaries, who may examine the storage medium of a user's mobile device at different points of time and force the user to decrypt data. MobiCeal relies on "dummy write" to obfuscate the differences between multiple snapshots of storage medium due to existence of hidden data. By incorporating PDE in block layer, MobiCeal supports a broad deployment of any block-based file systems on mobile devices. More importantly, MobiCeal is secure against side channel attacks which pose a serious threat to existing PDE schemes. A proof of concept implementation of MobiCeal is provided on an LG Nexus 4 Android phone using Android 4.2.2. It is shown that the performance of MobiCeal is significantly better than prior PDE systems against multi-snapshot adversaries.
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.