Re: And all completely irrelevant to us right-pondians...
".....Would they still (legally) be able to lock me up, as I have given them the password as far as I know?" Yes, because the court order under RIPA is not to supply a key but to decrypt the data. If you try to deliberately circumvent the law by letting your foreign friend hold an additional key then you are still in breach of the court order, and possibly also liable for further charges should the police be able to show in court (e.g., by the emails between you and your foreign friend) that you did so with the deliberate intent of hiding evidence and frustrating a police investigation.
Biting the hand that feeds IT
