Thursday, November 10, 2005

Encryption and furlongs of evidence 

How can rubbish like this go unchallenged?

Firstly we have Charles Clarke arguing that suspects be held for up to 90 days because 28 days is not long enough for the security services to decrypt the information stored on an encrypted hard-drive.

"Their advice has been unequivocal. A 14 or even 28-day period will not allow them the time they need adequately to investigate the most heavily encrypted data. They have made it clear to me that the use of advanced encryption technology by those who pose a threat to law and order or the security of the country is becoming more widespread and is growing rapidly. Encryption is more pervasive, more complex and easier to use than ever before.

That poses a significant challenge to police and investigators on two fronts. First, it means that even sifting the evidence to identify which computers require specialist investigation and decryption usually?the experts' word?takes a number of weeks. Each computer must be examined to assess what data can be easily gleaned and where heavyweight code-breaking is required."

Unless they know something I don't, a couple of years and the most powerful computers on the planet would be required to break 192-bit encryption (which is what I would understand as being a rather basic encryption standard). This is not an argument for 90 days. It could be an argument for 2 years.

Next we have the Prime Minister really losing it by measuring evidence in feet!

"I really have to say to the right horn. and learned Gentleman that I find it quite extraordinary that he seeks to suggest that there is somehow no evidence that the police are putting forward for the case that they are making. They have put forward detailed reasons as to why they believe these powers to be necessary. For example, just this last weekend, we arrested people on a terrorist operation. There were 750 gigabytes of data; that is 66,000 ft-worth of data; that would be printed out and have to be investigated."

This is just utter rubbish? You don't print digital information onto paper to read! How do you print CCTV video or phone tap audio? What font do you use? Even if all the information is text based you use the power of the computer to do the searching for you, you don't print it out and read it. You can't measure evidence in feet, it means nothing! You may as well measure it in Ohms or measure it using the Scoville scale (used to measure the hotness of chillies).
This is obviously part of the 'utterly convincing argument' the police presented to him. He clearly has a problem distinguishing between convincing argument and arbitrary meaningless numbers (as we've seen before - only that time with with grave consequences).

Then later on, a poor Labour PM gets even more tied up in bullshit.

Janet Anderson:
"In their recent evidence to the Joint Committee on Human Rights, the police referred to one case in which, if they had printed out the computer data that they had recovered, it would have made a pile 66,000 ft high. That is the sort of challenge that the police face and they need our help to meet it."

So now, we are not only confused about what 'printing' computer data means, or what purpose it would serve, we are also confused about how we measure the length of this paper.
When Mr Blair used the 66,000ft figure I assumed he was talking about the length of the paper, and I was assuming (for no particular reason) that we were talking about standard A4 paper. I can sort of imagine how much that is, a very long roll of A4 width paper. For the sake of argument let's call one A4 sheet as being 1ft long. That's 66,000 sheets of paper. This is a lot, but not a huge amount.

Janet Anderson seems to have the impression that this 66,000 figure referees to the height of a pile of paper. Assuming this time that we are talking about A4 sheets piled on top of each other, we can try and make a calculation. I would assume the width of 1000 sheets would be about 1ft (not taking account of the compression exerted on the sheets below by the paper above). That makes 66 million sheets of paper. That's one sheet of paper for every British citizen! So when she talks about the police needing 'our' help to meet this challenge, at least there's a simple way to divide up the work.

Whatever the length of the evidence, this locking people up without charge is madness. I agree with the suggestion sent in by a Today programme listener. Allow the police the 90 days, but if at the end of it they can't being a substantial charge, they have to pay the detainee 10 million pounds (or 10,000 ft of money).

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