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Questions about using BitLocker Drive Encryption

Questions about using BitLocker Drive Encryption with Windows Vista? Serdar Yegulalp discusses some myths and other concerns surrounding it.

This is the second part of Serdar's two-part series on Windows Vista's BitLocker.

BitLocker Drive Encryption, the security feature touted in Windows Vista, is sparking controversy. Some of the furor is predicated on misinformation about what BitLocker really is or how it is to be used, or how it might be possible to perform an end-run around it.

BitLocker has no key escrow system. "Key escrow," a controversial provision in some encryption systems, allows a third party such as a government body to hold a set of universal keys that would allow any data encrypted by the system to be unlocked with one of those keys. When asked if BitLocker would have any such "back door" provisions, Niels Ferguson, one of the Microsoft developers responsible for BitLocker, responded as bluntly as possible: "Over my dead body. … In the unlikely situation we're forced to [add key escrow] by law, we'll either announce it publicly or withdraw the entire feature."

You can't gain access to a BitLocker volume by simply installing a parallel copy of Vista or moving the hard drive to another computer. BitLocker uses multiple key structures to ensure that a system volume cannot be decrypted by using another parallel install of Vista or some other extra operating system (OS) mechanism. Only the OS, encrypted by a given combination of keys, can access the key required to read the boot volume.

BitLocker in competition
Another widely asked question about BitLocker is how it compares to existing encryption products, both commercial and free. WinMagic Inc.'s SecureDoc is one example of a Windows product that supports full-system encryption, including the OS partition, and that also supports other verification mechanisms such as smart cards. SecureDoc is used extensively. More than 500,000 licenses have been sold worldwide, according to the company. Administrators may want to balance the per-license cost of SecureDoc ($150 per seat, with volume discounts) against the cost of upgrading to Vista. If Vista upgrades are planned and they work out to be cheaper overall, BitLocker may be the better deal. People looking to encrypt specific systems now, however, can benefit from SecureDoc.

Another product that is popular is TrueCrypt. I've worked with TrueCrypt a fair amount, and it has one feature that distinguishes it heavily from BitLocker: Full volumes encrypted with it are indistinguishable from random data, and there is no volume signature on an unencrypted volume. By contrast, BitLocker volumes can be easily detected, as they have a distinct signature. To that end, TrueCrypt is more useful for encrypting non-system data, such as auxiliary or external drives.

One possible way to use TrueCrypt (or another file-and-partition product) for creating an encrypted OS partition would be to create a system volume for a virtual PC on an encrypted drive and use that. This is perfectly feasible (in fact, I've done it myself), but it requires the presence of virtual machine software in the first place.

Because BitLocker is a Vista-exclusive product designed to meet a very specific need — full-disk encryption for the Windows OS partition — the odds of it displacing existing general-purpose or full-disk encryption solutions are pretty low. But as Vista becomes the version of Windows over the next several years, BitLocker ought to become more attractive as a standard-issue way to secure laptops and desktops -- either with or without the additional expense of TPM hardware.

Read the first half of this tip, End-to-end encryption for Windows Vista systems: BitLocker.

Serdar Yegulalp
wrote for Windows Magazine from 1994 through 2001, covering a wide range of technology topics. He now plies his expertise in Windows NT, Windows 2000 and Windows XP as publisher of The Windows 2000 Power Users Newsletter and writes technology columns for TechTarget.

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