[nabaraz]

Do you happen to know how is it different in US? I am curious on what would happen if someone simply refused to provide the decryption key.

[riskable]

In the US we have the 5th Amendment to the Constitution which forbids the government from making you testify against yourself. Details can be found here:

http://en.wikipedia.org/wiki/Key_disclosure_law#United_State...

TL;DR: Case law is mixed on the matter but it sure seems clear to me at least. I don't understand why people can't just say, "I forgot it. Sorry."