Due to the UK's key disclosure laws (http://en.wikipedia.org/wiki/Key_disclosure_law#United_Kingd...) encryption doesn't help. If you don't provide your key to the government they can put you in jail for up to two years.
I'm sorry I sound so naive, but I'm still incredibly flabbergasted by this.
This stuff is not ok. Not at all.
1) These are not the police. Police are trained law enforcement officers. These are customs and immigration employees. They get training, but it's more important that they can get a security clearance.
2) Can you think of a reason for having a file of white noise that you could explain to this person that they would understand and believe?
You really don't have many rights outside immigration/customs. "Probable cause" is "he acted weird." Cars have been destructively disassembled for less.
If they look at a computer based on information provided by a person entering the country, they have to have clearance. Uncleared or precleared people will often hang out over the shoulder of someone with clearance, so it's not really that "secure", but it ensures that queries are handled by cleared personnel.
There are serious problems with it. (I speak as someone who's normally okay with 'big government' and legal restrictions.)
In theory you'd have to be doing something to get their attention. The most well known case is of a man who has a psychotic illness and who was also importing "explosives" and behaving in odd ways. But that's what some people with a mental illness do. It's one of the features of illness, that people are not rational and do not do things that are in their best interest.
The "give us your key or go to jail" are not the worst abuses of RIPA though. This would be rare, and people would have legal representation. The local councils mis-using RIPA to see if people are applying to the wrong schools are worse. These are already so common they've had to be cut back, and there's little opportunity for legal representation and the oversight is much less.
(https://en.wikipedia.org/wiki/Regulation_of_Investigatory_Po...)
Counter-example: You work for Company A and need to deliver documents to Company B. Your comrade X creates the key. You pass through a dangerous part of town where Company C works. Fearing that C might kidnap you, X created the key so that X must be present when they reach Company B through their alternate route.
>"but such behaviour on your part would rightly be taken as proof of ill-intent because it would be an unreasonable thing to do and so could only have been intended to avoid complying with the law."
There is a policeman in your head.