RE: Right to Silence
It doesnt exist in the case of passwords and encryption keys. To take the arguement further however you can put forward an arguement that you dont know the key/password by virtue of the account not belonging to you. By this method you can circumvent the requirement since you would have to have it put to you in court that the accuont was yours, lie about it, be charged with perjury and convicted of it ( not likely if the contents of the account cannot be verified with out the key ). At this point if you are found guilty then it becomes fact that you do own the account and you are then required to give the keys/password. Before this however you can only be forced into giving up the key:password if you admit to owning the account. Its like a law making it illegal to not give the name of your unicorn, I must first prove the fact that the unicorn exists and then have a court give the verdict that the unicorn is in fact yours.
Its a very annoying defence, but if its the case that the encryption in use is strong enough or that the account can be destroyed in the mean time then it is a defence that could easily be employed. Of course the destruction of evidence is wrong but in todays world that evidence could easily be in another country .. hence the urgency in recovering the key.