Re: Impossible
There are deniable encryption systems that come close, but they have strong usage constraints that make them not super practical for day to day use. Generally they let you selectively decrypt portions of the data without revealing how many portions are still encrypted. This only helps you if the cops aren't sure what you have, of course -- if they have other evidence you have a specific piece of info, they can just keep you in jail on contempt charges until you cough up the passphrase for it.
Biting the hand that feeds IT
