[hiisukun]

A quick test for "willingly" as you put it, is not due to force, fraud, or fear.

I would think that a ransom situation would likely qualify as some type of duress. Deciding whether the criminal act is "theft" (ie. stolen) or "fraud" or something else is probably missing the point.

And certainly, some aspect in the exchange (pay money for this encryption key) did not involve permission: the encryption of the files!

But, how to restore things after a wrong has occurred? I agree with your point that there is a risk of committing a greater wrong against an innocent party. Hence the special protections of currency as a unique type of property in the article. Does bitcoin fit this model? An interesting discussion!