What you'd want is an encryption system that had two passwords: one that was accepted and caused the de-encryption of a volume of data that looked real, plausib

What you'd want is an encryption system that had two passwords: one that was accepted and caused the de-encryption of a volume of data that looked real, plausible, and had recent atime/mtime timestamps but wasn't actually your secret data. You would also have a second password, the existence of which you wouldn't reveal, that would also be accepted but result in the de-encryption of your true volume with your secret data. I think truecrypt has something like this but I wouldn't trust truecrypt to my data. Not in this day and age.