Toward Robust Hidden Volumes Using Write-Only Oblivious RAM

Abstract

With sensitive data being increasingly stored on mobile devices and laptops, hard disk encryption is more important than ever. In particular, being able to plausibly deny that a hard disk contains certain information is a very useful and interesting research goal. However, it has been known for some time that existing ``hidden volume'' solutions, like TrueCrypt, fail in the face of an adversary who is able to observe the contents of a disk on multiple, separate occasions. In this work, we explore more robust constructions for hidden volumes and present HiVE, which is resistant to more powerful adversaries with multiple-snapshot capabilities. In pursuit of this, we propose the first security definitions for hidden volumes, and prove HiVE secure under these definitions. At the core of HiVE, we design a new write-only Oblivious RAM. We show that, when only hiding writes, it is possible to achieve ORAM with optimal O(1) communication complexity and only poly-logarithmic user memory. This is a significant improvement over existing work and an independently interesting result. We go on to show that our write-only ORAM is specially equipped to provide hidden volume functionality with low overhead and significantly increased security. Finally, we implement HiVE as a Linux kernel block device to show both its practicality and usefulness on existing platforms.