Risk
9/24/2009
11:30 AM
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Full Disk Encryption Evolves

The Opal standard paves the way for hardware-based encryption.

Earlier this month, the Naval Hospital in Pensacola, Fla., began notifying thousands of individuals that personally identifiable information about them had been lost when a laptop disappeared. In August, the National Guard announced that a laptop containing personal information on 131,000 members had been stolen. We could go on--rarely does a month go by without an organization revealing the loss or theft of a laptop brimming with sensitive data.

Full disk encryption, or FDE, is the preferred mechanism to address this threat because, as the name implies, the technology lets IT encrypt the entire hard drive so that sensitive data is protected, no matter where it resides. But unfortunately, FDE adoption comes at a price: complex and costly deployments, additional licensing fees, and one more application for IT to support.

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Now, adoption of a new standard for hardware-based FDE, called Opal, aims to alleviate some of that pain.

The Need For FDE

No organization can plead ignorance of encryption options. Microsoft Windows, Mac OS X, and Linux all have built-in support for file-system-level encryption.

But while encrypting a file system, or providing an encrypted folder on an employee's laptop, is better than nothing, it still leaves too much to chance. Did the employee put all sensitive data into that target folder? Was anything left in caches or temporary directories? And perhaps most critical, without FDE, if a device is stolen or lost, how do you definitively know that all of the sensitive information it contained was encrypted?

Short answer: You don't.

Vendors including Check Point Software (via its PointSec acquisition), Guardian Edge, McAfee (via its Safeboot acquisition), and PGP offer software-based FDE suites that can help you avoid all these problems. With software-based FDE products, the data on the drive can only be accessed when the operating system is booted and the encryption keys unlocked. But the technology isn't perfect--software-based FDE also has drawbacks. First, a number of software FDE products don't support Linux or Mac OS X. Second, depending on the age and processing power of the laptop, the encryption process can slow down a machine.

Finally, encryption keys are stored in the computer's memory, which makes them vulnerable to a class of so-called "cold boot" attacks, in which encryption keys are recovered in RAM.

Enter Opal

In January 2009, the Trusted Computing Group released the final specification of the Opal Security Subsystem Class, a standard for applying hardware-based encryption.

Moving hard-drive encryption into hardware has a number of advantages. For starters, it works with any OS. It also moves the computational overhead of the encryption process to dedicated processors, alleviating any computing load on the system's CPU.

In addition, the encryption/decryption keys are stored in the hard-drive controller and never sit in the system's memory, making "cold boot" attacks ineffective.

Hardware-based FDE also simplifies the key escrow dilemma--that is, the need to manage encryption keys. Simply put, the keys used by the hard drive can be unlocked only by a passphrase entered during the pre-boot sequence. The passphrase is sent to the hard drive controller before the OS boots, so the keys never leave the hard drive's hardware. Also, multiple passphrases can be configured to unlock those keys.

Note that software-based FDE products do allow you to choose the encryption algorithm and variable key strengths, while most Opal drives are limited to AES-128. We see this as being an issue only for organizations that require specific algorithms or larger key sizes.

HOW SOFTWARE AND HARDWARE APPROACHES COMPARE
  Pros Cons
Software
> Widely deployed > May not support all systems
> Flexible encryption options > Costly
> Strong management options > Potential performance impact
  > Susceptible to cold boot attack
Hardware
(Opal)
> OS agnostic > Requires new laptop
> Great performance > Most only supports 128-bit AES
> Inexpensive > Limited management options
> Immune to cold boot attack  

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