You can't prove a universal negative, so the only way that becomes a prosecutable offense is if the initial assumption is of guilt rather than innocence, no?
> "Drage was convicted of failing to disclose an encryption key in September." [1]
Though it says that he "failed" to disclose a password when asked. Not clear if he was unwilling or unable, and if such a distinction even matters. (It's unclear if the use of the term "refusal" was an actual action, or a journalistic spin. It might come down to needing to be very careful about word choice in such situations; "I would like to speak with my lawyer first" seems like the most appropriate answer).
It's contrasted with Napoleonic code, in which innocence must be proven. It is or was the basis of law in countries conquered under Napoleon, and/or their colonies (e.g.: Mexico).