Data Loss Prevention and Storage Utilization Improvement of the Hidden Volume on Mobile Devices Sensitive data protection is vital for mobile users. An effective way is to store sensitive data in the hidden volume of mobile devices with Plausibly Deniable Encryption (PDE) systems. Typically, PDE creates a hidden volume inside the outer volume. However, existing PDE systems could lose data, due to overriding the hidden volume, and significantly waste physical storage, because of the fixedly reserved area for the hidden volume. In this paper, we present MobiGyges to solve the above problems. MobiGyges leverages the Thin Pool to coordinate the storage allocation for both the outer volume and the hidden volume which avoids data override and prevents data loss. Moreover, it improves the storage efficiency by virtualizing the total physical storage into small storage blocks and utilizing the blocks for the outer volume and the hidden volume, which eliminates the reserved area. We implement MobiGyges prototype on Google Nexus 6P with LineageOS 13 operating system. Experimental results show that MobiGyges avoids data loss and improves storage utilization up to 31% compared with existing works.

TrustFS: An SGXEnabled Stackable File System Framework Data confidentiality in cloud services is commonly ensured by encrypting information before uploading it. However, this approach limits the use of contentaware functionalities, such as deduplication and compression. Although this issue has been addressed individually for some of these functionalities, no unified framework for building secure storage systems exists that can leverage such operations over encrypted data. We present TrustFS, a programmable and modular stackable file system framework for implementing secure contentaware storage functionalities over hardwareassisted trusted execution environments. This framework extends the original SafeFS architecture to provide the isolated execution guarantees of Intel SGX. We demonstrate its usability by implementing an SGXenabled stackable file system prototype while a preliminary evaluation shows that it incurs reasonable performance overhead when compared to conventional storage systems. Finally, we highlight open research challenges that must be further pursued in order for TrustFS to be fully adequate for building productionready secure storage solutions.