Well, they don't matter wrt. the law. Either the prosecution is convinced you gave up all the keys (you win), or they believe you gave them a key that was just a distraction and they throw you in jail unless you give them the other key (you lose).

How do you prove yourself innocent then? You did give them the keys.

The point is that you look exactly the same as an innocent person.

You are taking the only possible pathway to being proved innocent.

It'd be like if I were to say "It doesn't matter what you do. The police are corrupt anyway, and will take you out back and shoot you no matter what. Guilty or innocent, if you get accused of a crime, you are dead."

And if they are going to lock you up no matter what, then you may as well use multiple plausible deniability keys. As you said, it doesn't matter what you do, the outcome stays the same.

> How do you prove yourself innocent then? You did give them the keys.

Well, prosecution needs to have a legally convincing argument that indicates it is likely you have another encrypted partition you're not giving up keys to.

In fact, the situation is no different from this: say you're a murder suspect and a neighbour saw you carrying several large heavy sacks into your car and you drove away. Say what really happened is that you went and buried some bags of toxic waste in some location, and then went and buried a dead body in another location. When asked by prosecution, you confess to burying toxic waste and tell them where. The rest of the outcome of the trial depends entirely on whether you've successfully convinced them that you just buried the toxic waste.

That's fine, but your argument is effectively that you are screwed no matter what.

If you are truly innocent, the prosecution might claim "oh they have extra keys that they haven't given up", and there is nothing you can do to prove them wrong.

Like jbg said in another comment here, the legal system doesn't work that way, where the prosecution can claim you did stuff and you have to disprove the claim. The burden of proof is on the prosecution.

So you are agreeing with me that this tactic of plausible deniability with multiple encryption keys works then?

Which is it? Does encryption allow you to hide from the law, or can innocent people just be proclaimed that they are hiding something and that they have to give up keys that don't exist?

It is one or the other, because encryption plus multiple keys makes you 'indistinguishable' from an innocent person who truly cannot give you a key that doesn't exist.

You're proposing a false dichotomy.

The tactic might work, but how well it would work would depend on what other evidence was presented that you do have another encrypted area. For example, if they analyse the partition you gave them the key to and show that it hasn't been booted in 18 months; they cross-reference the cached DHCP leases with the times you were known to have been online using that machine and find discrepancies; they might even have secretly imaged your disk a month earlier and show that a large amount of supposedly free space has changed content in the meantime.

(Maybe they even have you recorded telling someone that you have a second encrypted area on the machine.)

If there's no such evidence, then it ought to be pretty hard to convict you.

In most jurisdictions, the prosecution being _convinced_ that you are guilty isn't enough to throw you in jail -- there's still the small issue of proving their case in front of a judge.

Thanks for pointing this out. I was thinking "judge or jury" but wrote "prosecution" in my comment above.

Which is terrifying, as the whole point of plausibly deniable passwords is that attitude will end up with innocent people in jail for data that doesn't exist have.

Until it's tested in court on a gray area case, it's hard to know for sure, but I'm pretty confident that UK courts would apply the "reasonable doubt" criterion to the fact that the defendant indeed posesses an encrypted volume they have not provided the keys to.

I.e. if the defendant can reasonably claim that there are no further encrypted volumes on their device, I don't believe they would be imprisoned under this rule.

This is one of the major issues with laws requiring password disclosure.

First of all, a truly careful criminal can use this method to comply with the law while still hiding what they are really after -- negating the usefulness to some extent.

Secondly, once law enforcement catches on to this, they can then claim that someone that does disclose a password actually gave them a plausible deniability or duress key, and they haven't actually given up the real key, and thus the innocent person could potentially be convicted for not giving up a password that doesn't even exist.