How does the Truecrypt version of this idea work? I was under the impression that the double-secret data were written in such a way as to be indistinguishable from random bits that normally appear in the files that contain encrypted volumes, with no metadata (e.g. a partition table) to suggest that those random bits are actually interesting.
I figure there is at least one good reason to include amenable "filler" in a "single-secret" file containing encrypted data: it means the size of the plaintext data cannot be inferred from the size of the file. So there is plausible deniability for having amenable "random" data present on that basis alone.
I'm not saying it's easy to extend this scheme to accommodate all environments and/or user experiences. As you say, you can't just e.g. have another partition sitting around full of nothing but suspicious random data.
I figure there is at least one good reason to include amenable "filler" in a "single-secret" file containing encrypted data: it means the size of the plaintext data cannot be inferred from the size of the file. So there is plausible deniability for having amenable "random" data present on that basis alone.
I'm not saying it's easy to extend this scheme to accommodate all environments and/or user experiences. As you say, you can't just e.g. have another partition sitting around full of nothing but suspicious random data.