[hiq]

Indeed there is, it is called plausible deniability [1]. With Truecrypt, you can nest a hidden volume within another volume, so you can decrypt the latter and it will only show innocuous files, while another password (using other parts of the volume) would provide other (incriminating) files.

I wonder what is in a judge's mind when the encrypted evidence turns out to be kitten pictures and the defendant claims that he does not have any other password to provide.

[1]: https://en.wikipedia.org/wiki/Plausible_deniability#Use_in_c...

edit: clarification

[w0000t]

That is not what OP is talking about. You cannot get different information out of the same chunk of encrypted data. That would basically make infinite compression.

What the methods you mentioned are doing, is hiding information in places which are marked as: random data no information here. But in reality there is information there. You then need to have dummy information somewhere else.

[grumio]

This would be trivial to do with one-time-pads. A bit bulky, but simple. But in a way, you'd still be right. The "dummy information" is (encoded into) the second key.