In the UK, if you can meet the evidential burden to raise the issue that your hard disk is in fact full of random data, then it must be proved beyond reasonable doubt that that is not the case. In other words, unless you aren't even permitted to use that as a defence, the prosecution does actually have to prove that you have a key. Now that we have some experience of successful RIPA prosecutions, the smart advice appears to be 1) don't claim to have created a key that you refuse on principle to turn over, or 2) to have created a key that you've since forgotten: you will be asked how long it is – if short, it won't be reasonable to have forgotten it, if long, unreasonable not to have recorded it elsewhere. Basically don't admit to use of encryption unless you're capable of producing a key.

> you will be asked how long it is – if short, it won't be reasonable to have forgotten it, if long, unreasonable not to have recorded it elsewhere.

Bullocks. Just yesterday they replaced the keypad on a door I've used a hundred times before and I completely blanked on the combination. It was the same 4-digit number it was before but the keypad was different and that was all it took. On the other hand, the passwords for the computers are 14 random characters, and nobody ever wrote them down because a) they were explicitly forbidden to and b) everyone used them so often they didn't need to. Except that half the time anyone would go on vacation for more than a week they would forget and have to beg the backup admins to restore their home directory because the local data was encrypted but the backups weren't.

The idea that it isn't "reasonable" for people to do these things is belied by the fact that they regularly do. And having the police break into your house and turn your life upside down by carting off with half your stuff is exactly the sort of shock that will interfere with your ability to remember.

They aren't calling it unreasonable because it's unreasonable, they're calling it unreasonable because they'd rather put innocent people in prison than let guilty people go. The prosecutor is willing to lie about what is reasonable and the judge is willing to believe the lie. But at that point it doesn't matter what you actually do because facts and logic are no longer in play. They're just making things up. If they don't get you for not providing your encryption key then they'll just make up something else for you to be guilty of.

> The 5th amendment protects US citizens from being forced to reveal their encryption keys.

IANAL, but it does not. It protects against self incrimination. They can make you incriminate someone else just fine, and if you try to object on 5th amendment grounds they can grant you immunity to whatever they might find there.

> The 5th amendment protects US citizens from being forced to reveal their encryption keys.

This is far far from decided or well settled. I can think of countless instances where it is likely false.

I wonder, though, if your key were a confession to a crime you did actually commit (perhaps you stole a pack of gum) and you cannot be compelled to testify against yourself, how would that turn out?

This has gone both ways so far in cases in the United States[1]. One of the fundamental questions is whether or not you giving up the key is testimonial or not. There is a litany of things which have been held to not be testimonial, and thus not implicated by the 5th amendment, including giving up your saliva, blood, fingerprints, standing in a line up, etc.

The really interesting legal question to me is as neuroscience advances, it is likely in the near future that scientists may be able recover one's key (or other relevant information regarding crime) through studying one's brain by imaging or the use of other sensors. Under current case law there is a really really good argument this would not be testimonial (i.e. it is similar to taking your fingerprints or blood), yet provides the same information they could obtain by compelling your testimony.

Does the 5th Amendment prohibit the government from scanning your brain to obtain information about a crime? I think there is a significant number of judges who would find under current law it does not.

[1] http://en.wikipedia.org/wiki/Key_disclosure_law#United_State...

They will grant you immunity from the shoplifting charge, or make that confession inadmissible

"The 5th amendment protects US citizens from being forced to reveal their encryption keys."

Tell that to Ladar Levison. ;)