Observable Steganographic File Systems
Claudia Diaz

Steganographic file systems are designed to hide the existence of files against an adversary who has the ability to coerce the user into revealing (some of) his access keys. Several techniques have been proposed in the literature to protect against adversaries capable of obtaining a single snapshot of the raw storage, but these techniques cannot reliably resist adversaries who have access to more than one snapshot, or access to the traffic to and from the file storage. In this talk, we consider a more powerful adversary who can continuously record the contents of the raw storage and monitor all accesses to it. We first show that simple randomization techniques are not sufficient to conceal file locations, and propose a method to build a steganographic file system whose storage device is fully observable to the adversary, but which still provides plausible deniability (i.e., the adversary is not able to obtain evidence of the existence of hidden files).