I was reading this question and @Mikaveli's answer regarding a list of things not to bring, including money.
So my question is, what if I bring my laptop across borders and its hard drive has a bitcoin wallet file containing more bitcoin (value-wise) than the maximum amount of currency allowed to bring across the border. Am I legally required to declare it?
What if that wallet file isn't on my laptop, but is stored in the cloud somewhere (setting aside the security risks of that)? Then I get to my destination and download the wallet onto my laptop (presumably deleting it before crossing another border) and maybe do some transactions (such as exchanging bitcoin for the local currency, or paying for things). Does that change the legality? If not, am I legally required to declare all bitcoin I own every time I cross a border?
What if I email the wallet file to a friend (highly trusted friend obviously) in the destination country before leaving? Then nothing except my knowledge of the password has crossed the border with me, though the wallet file did cross the border before me.
Finally, for all three cases (and especially the two where the file crosses the border at a different time than me), what if the wallet file is encrypted with a strong password that only I know? Does that change anything?
EDIT - For the purposes of this questions let's say I'm travelling from the US to France (or another Schengen Zone country)