When we use file system encryption, even though attackers won't be able to access the information we've stored, they would be able to find out the fact that we have encrypted data on our drive. So the question is, are there ways to hide even the existence of encryption to an attacker with full access to the storage device and reasonable resources, so that to their eyes, the encrypted data are just unused space.
It would be best if the following can be answered:
- Are there research on this subject? What's the scholarly term?
- Are there theoretical limitations on this? Is such encryption possible?
- Are there any known implementations?
PS: What I'm asking is stronger than deniable filesystems: the existence of encryption of any sort must be plausibly hidden, so that reasonable attackers won't even attempt decryption, not just the existence of specific content.