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How they cracked the terrorists' code

------- Forwarded message follows ------- Date sent: Thu, 17 Jan 2002 16:29:44 +0000 (GMT) From: Cian O'Connor <cian_oconnor@yahoo.co.uk> Subject: How they cracked the terrorists' code To: ukcrypto@chiark.greenend.org.uk Send reply to: ukcrypto@chiark.greenend.org.uk

>From the Independant on the computer found by the Wall
Street Journal in Afghanistan:

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How they cracked the terrorists' code

Getting to the heart of the documents contained in the al-Qa'ida computer ­ bought by chance by the Wall Street Journal's reporter in Kabul ­ meant cracking the encryption of Microsoft's Windows 2000 operating system installed on the machine, which had been used to protect the data.

That is not a trivial task. Microsoft will only say that if you lose the password that controls entry to a Windows 2000 system, your best option is to remember it ­ or simply to wipe the machine and start again. And its Encrypting File System (EFS), which had been used to encode the files, is just as strong.

But the files were too valuable for that. Instead, the team embarked on the task of breaking through the encryption, which jumbles the contents of the files so that even someone reading the individual bytes of data stored on the actual hard disk (rather than trying to access them through the operating system, which had locked them out) would simply find rubbish.

Cracking the encryption meant finding the digital "key" that had previously been used to unlock it. That was not stored in any readable file on the machine, for it was itself encrypted.

The only way to reproduce it was to generate the key from first principles: by trying various combinations of random bits and trying to decrypt the file with them, and seeing if it produced sense ­ or gibberish.

Luckily, the PC had a version of Windows 2000 with an "export-quality" key ­ only 40-bits long, rather than the "US" quality, which being 128-bits long would have been billions of times harder to crack.

Even so, it took the equivalent of a set of supercomputers running for five days, 24 hours a day, to find the key. But find it they did.

The irony that the terrorists used a product made by one of the US's biggest corporations to protect plans it was making against it may not be lost on an administration that recently relaxed rules on the export of "strong" encryption. Tighter controls may follow.

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