A bit about Bitlocker
Encryption, Windows and you
Encryption is the staple weapon of the security business. As old as war itself, it scrambles data to conceal it from those not meant to see it.
It sounds simple but nothing is simple about encryption, as the mathematical geniuses at Bletchley Park knew. That said, a modern, well-managed encryption system can protect desktop data to a degree that was unimaginable 70 years ago. But it takes a little forethought and planning.
Lock, stock and barrel
Making encryption work on a Windows 7 desktop is, on the face of it, simply a matter of enabling the BitLocker  feature. With Vista, you need to create the boot partition manually, a process that Windows 7 does for you. Under both, 128-bit or 256-bit Advanced Encryption Standard provides the protection.
BitLocker, like all encryption, uses a key to unlock the data. If the desktop includes the Trusted Platform Module  (TPM) chip, it uses the chip to store the key. After BitLocker has been enabled, the drive can't be read without the presence of the key stored in the chip.
In other words, if removed from the computer, the disk's contents are protected. Without a TPM, the same functionality can be had by using a USB drive to store the key instead. It needs to be inserted for each start-up or resume from hibernation.
That's fine for single desktops but what happens if you manage dozens or hundreds of desktops on the move? And what about USB memory sticks, those highly portable islands of data? Can they be protected too?
Where are my keys?
The answer is that you can protect both laptops and USB keys using BitLocker, but you may need to be prepared for a little more work if any of those mobile machines is not TPM-compliant. That's because the loss of the recovery key means the drive can't be accessed.
You need to be ready if you don't want the helpdesk deluged with angry calls
It is certain that users will lose USB-stored keys so you need to be ready if you don't want the helpdesk deluged with angry calls.
Recovery might also be needed if the machine is cascaded to another user, the BIOS is updated, a new motherboard is installed or the drive is re-deployed elsewhere.
The safest option to enable recovery is to ensure that the relevant information is stored in Active Directory (AD), a process that can be enforced with a Group Policy . That way, recovery can be made using the BitLocker recovery console, which is integrated into the early boot process.
BitLocker can protect USB drives too. Again, you need to to configure Removable Data Drive policies in Group Policy and store the recovery information in AD.
Note that the "Allow Access To BitLocker-Protected Removable Data Drives From Earlier Versions Of Windows" policy does exactly what it says on the tin. After that, encrypting the drive is a matter of enabling BitLocker, entering a password, saving and printing the recovery data, then waiting for Windows to encrypt the drive.
Lack of distinction
It is not possible, however, for group policies to distinguish automatically between simple USB drives and storage that is part of another device, such as a digital camera or smartphone.
While this may be desirable from the enterprise point of view, as it can deter people from connecting potentially risky storage devices to the corporate network, users may find this restrictive if they are using these devices for work.
Note too that you can't deny write access to unencrypted removable drives if your organisation uses recovery or start-up keys, as those keys must be stored on unencrypted media. This situation could arise when using non-TPM-compliant hardware, for example.
It is possible, even fairly simple, to enable encryption for mobile devices. Managing keys is largely a matter of educating users, with recovery information backup provided by AD.
Given the likelihood of small portable devices going missing for all sorts of reasons, there is little justification for not using the tools built into the operating system. ®