Sometimes instead of encrypting a file or a set of files, you want to encrypt an entire filesystem, partition, or disk.

One of the chief advantages of this approach is that, once you have entered your encryption key, the encryption becomes transparent to both you and your applications. When you power off your computer, your data is securely encrypted. It is the best of both worlds.

Disk Encryption Software and Documentation

Numerous solutions exist to enable you to do this, under Windows, Unix, or MacOS.

Under Unix of of the best options is loop-AES, which utilizes the AES algorithm to encrypt a loop file system.

Another option for Unix is Cryptoloop.

TCFS (Transparent Cryptographic File System) utilizes NFS (Network File System) to provide Triple-DES or RC5 encyption. TCFS currently only supports Linux. For more information on TCFS, read the TCFS FAQ.

Allan Latham's PPDD (Practical Privacy Disc Driver) is a Linux device driver which creates a device which looks like a disk partition. PPDD utilizes Bruce Schneier's Blowfish algorithm.

Julian Assange's Rubberhose is a unique Linux tool which combines encryption and steganography. Rubberose supports DES, 3DES, IDEA, RC5, RC6, Blowfish, Twofish and CAST.

Linux users should read David Braun's Linux Disk Encryption HOWTO.

Gentoo Linux users will benefit from reading A Structured Approach to Hard Disk Encryption.

CompuSec is a free solution for Windows which implements a Fast AES algorithm.

Cypherix Cryptainer LE is a free solution for Windows which implements the Blowfish algorithm, but is limited to creating 10MB partitions.

BestCrypt is a commercial option which supports both Linux and Windows and is capable of utilizing the AES, GOST, Blowfish, or Twofish algorithms.

Another commercial option is PGPdisk, which supports both Windows and MacOS.

DriveCrypt is a commercial options with utilizes the AES algorithm and supports both Windows and Pocket PC's.

Additional commercial packages for Windows include Paragon Encrypted Disk, CryptoExpert, and Ultimaco SafeGuard.