Hardware-based full disk encryption

Hardware-based full disk encryption (FDE) is available from many hard disk drive (HDD) vendors, including: Seagate Technology, Hitachi, Western Digital, Samsung, Toshiba and also solid-state drive vendors such as Samsung. The symmetric encryption key is maintained independently from the CPU, thus removing computer memory as a potential attack vector.

Hardware-FDE has 2 major components: the hardware encryptor and the data store. There are currently three varieties of hardware-FDE:

  1. Hard Disk Drive (HDD) FDE
  2. Enclosed Hard Disk Drive
  3. Bridge and Chipset (BC) FDE

Contents

Hard disk drive FDE

HDD FDE is made by HDD vendors using the OPAL and Enterprise standards - Trusted Computing Group.[1] Key management takes place within the hard disk controller and encryption keys are 128 or 256 bit Advanced Encryption Standard (AES) keys. Authentication on power up of the drive must still take place within the CPU via either a software pre-boot authentication environment (i.e., with a software-based full disk encryption component - hybrid full disk encryption) or with a BIOS password.

Hitachi, Seagate, Samsung, and Toshiba are the disk drive manufacturers offering TCG OPALSATA drives. Older technologies include the proprietary Seagate DriveTrust, and the older, and less secure, PATA Security command standard shipped by all drive makers including Western Digital. Enterprise SAS versions of the TCG standard are called "TCG Enterprise" drives. All drive makers have suggested the appropriate term for this new class of device and new type of functionality be "self-encrypting drives."

Enclosed hard disk drive FDE

Within a standard hard drive form factor case both the encryptor (BC) and a smaller form factor, commercially available, hard disk drive is enclosed.

For example ViaSat (formally Stonewood Electronics) with their FlagStone and Eclypt[2] drives.

Chipset FDE

The encryptor bridge and chipset (BC) is placed between the computer and the standard hard disk drive, encrypting every sector written to it.

Intel announced the release of the Danbury chipset[3] but has since abandoned this approach.

Advantages

Hardware-based encryption when built into the drive or within the drive enclosure is notably transparent to the user. The drive except for bootup authentication operates just like any drive with no degradation in performance. There is no complication or performance overhead, unlike disk encryption software, since all the encryption is invisible to the operating system and the host computers processor.

The two main use cases are Data At Rest protection, and Cryptographic Disk Erasure.

In Data At Rest protection a laptop is simply closed which powers down the disk. The disk now self-protects all the data on it. Because all the data, even the OS, is now encrypted, with a secure mode of AES, and locked from reading and writing the data is safe. The drive requires an authentication code which can be as strong as 32 bytes (2^256) to unlock.

When a Cryptographic Disk Erasure command is given (with proper authentication credentials), the drive self-generates a new media encryption key and goes into a 'new drive' state. The old data has become irretrievable. Unlike other forms of sanitization, this action takes a few milliseconds at most. So a drive can be safely repurposed very quickly.

Disadvantages

FDE is only safe when the computer is off or hibernated. If the computer is stolen while turned on or only suspended, a restart which boots from a USB stick or CD may reveal the data without need for the password because it may not be prompted to be entered. Some specific hardware configurations may have additional protection mechanisms to limit this exposure.[4][5]

See also

References