TrueCrypt is the free open-source disk encryption software for Windows Vista/XP, Mac OS X, and LinuxMain Features:    * Creates a virtual encrypted disk within a file and mounts it as a real disk.    * Encrypts an entire partition or storage device such as USB flash drive or hard drive.    * Encrypts a partition or drive where Windows is installed (pre-boot authentication).    * Encryption is automatic, real-time (on-the-fly) and transparent.    * Provides two levels of plausible deniability, in case an adversary forces you to reveal the password:      1) Hidden volume (steganography – more information may be found here).      2) No TrueCrypt volume can be identified (volumes cannot be distinguished from random data).    * Encryption algorithms: AES-256, Serpent, and Twofish. Mode of operation: XTS.