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Tue, Aug 15, 2006
. . . and I'll say it again: Before a politician can pass laws on a subject, s/he should be required to demonstrate above-average understanding of that subject.
The BBC reports that laws are being suggested that would make it illegal for a person to refuse to decrypt encrypted data.
Were there any actual knowledge in the heads of the people trying to get these laws passed, they would understand why it's a ludicrous proposal. A five-minute scan of TrueCrypt's website would be all it takes.
Here's the breakdown:
Computers store information on filesystems, which usually reside on disks or flash memory. They don't just write the file to the filesystem and rely on scanning the entire disk to find each file every time they want it: This would be like making notes in a book at a random place on a random page. It would take forever.
Instead, when a file is created, the computer makes a note in a "Table of contents" at the front of the "book". Then when you ask for a file, it looks in the table, finds out what "page" the file is on, goes to that "page", and retrieves the file.
When you delete a file normally, you might think that the computer applies an "eraser" to your "pencilled-in note", but it doesn't: All it does is erase the note in the "table of contents": The file is left untouched.
This is why people who format their PC hard-drive and then ebay it find their bank accounts suddenly empty: The hard-drive buyer has simply set software to scan through every "page" and construct a new "table of contents", effectively undeleting your entire hard drive and rendering all your information accessible.
In order to prevent this happening, secure deletion methods exist, such as "shred" - this over-writes the file, or the entire hard drive, with random data, completely removing the sensitive information and rendering it impossible to retrieve via software tools.
If you ever buy a second-hand hard-drive, it's well worth shredding it: If the previous owner installed any illegal material on it, you might be accussed of installing it yourself if it is discovered.
So, you buy a hard drive and you shred it: It now has completely random data on it. You then format it, safe in the knowledge that there is nothing on your drive that you didn't put there yourself.
So far, so good?
Next, you install TrueCrypt on your PC, and create an encrypted filesystem on your hard drive. Accessed via TrueCrypt, this looks like just another disk drive. You then shove all your sensitive files on it. Once done, you tell TrueCrypt to unmount the filesystem.
You now have masses of encrypted data on your hard disk. But encrypted data has no visible logic or order to it: The whole point of encryption is to scramble the data so nobody else can get at it.
Encrypted data, in short, is identical in appearance to completely random data. Should the police suddenly bash in your door and seize your hard drive, they will find a huge long string of ones and zeros written on it.
Is it a shredded drive, owned by a paranoid but perfectly legitimate user? Or is it an encrypted filesystem, owned by somebody with something to hide?
It's impossible to tell. Utterly impossible.
But it doesn't stop there: You can create an encrypted filesystem within another encrypted filesystem. So somebody can put a gun to your head and tell you that unless you decrypt the data, they're going to pull the trigger.
So you decrypt *that* filesystem, which has your sensitive-but-legal data on it. But nothing illegal is found. Just a load of as-yet-unused space.
Does *that* space contain illegal material? Impossible to tell - see above.
So I could create a file on my hard drive called "Encrypted.Filesystem", and mount it as an encrypted filesystem with the password "foo". And then on that encrypted filesystem, I could create another encrypted filesystem, with the password "bar"
I could then put lots of illegal material on the twice-encrypted "bar" filesystem, and put a load of perfectly legal material on the once-encrypted "foo" filesystem. And then email the "Encrypted.Filesystem" file to anybody I liked.
And regardless of what the law said about handing over encryption keys, nobody could ever prove that there was anything but legal information and empty space on that file. They could force me to decrypt "foo", but "bar" would remain completely safe and utterly undetectable.
Hence these legislation changes are worthless, beyond the fact that they clearly show that the government employs a lot of time-wasting idiots that the taxpayer would be better off without.
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