Re: Defeating Draconian laws
It is easy to show to an acceptable level you do not have the password, by having the person who has the password, saying what they did, and why, by phone and email. Preferrably, with a newspaper on copy. You can pre-plan they wipe the key if you do not arrive problem free.
Note, if the data is on a micro SD, you are less likely have an issue, as they are just so small.
If you are CAGE and planning to take US solders to court for war crimes, or are the partner of a journalist talking to Snowden, you will already be on the list for a home visit.
If you were not before, having good security practices at the airport is likely to put you on the home visit list and possibly on the no fly list. Piss off the man at your own risk.