TrueCrypt can create a virtual encrypted disk within a file and mount it as a real disk, or an entire hard disk partition or a device, such as USB memory stick, floppy disk, etc.
This software provides two levels of security: a hidden volume (more information may be found here), and a volume cannot be identified (no part of the volume can be distinguished from random data).
It utilizes the following encryption algorithms: AES (256-bit key), Blowfish (448-bit key), CAST5 (128-bit key), Serpent (256-bit key), Triple DES, and Twofish (256-bit key), and also supports cascading (e.g., AES-Serpent-Twofish).
It is based on Encryption for the Masses (E4M) 2.02a, conceived in 1997.
What's New in version 5.1a:
- When the system partition/drive is decrypted under Windows, the original partition table will not be restored. Note: This issue affected users who repartitioned an encrypted system drive and then decrypted it under Windows. (Windows Vista/XP/2008/2003)
- Other minor bug fixes. (Windows, Mac OS X, and Linux)
- Faster booting when the system partition/drive is encrypted (typically by 10%). (Windows Vista/XP/2008/2003)
- Other minor improvements. (Windows, Mac OS X, and Linux)
2.52 M (file size)
Price: Free 
