TrueCrypt is described by its author as
Free open-source disk encryption software for Windows Vista/XP, Mac OS X, and Linux
TrueCrypt is a feature rich, powerful and reliable software to secure any number of files, folders or even entire drives. It achieves this by creating a ‘virtual encrypted disk’. It is possible to hide most any thing in one ‘file’ that is only accessible with TrueCrypt and via password and/or keyfiles. It is also possible to encrypt an entire partition or a USB key or flash drive. TrueCrypt supports three main methods of encryption, AES-256, Serpent, and Twofish, and depending on the data being encrypted one may not even need the most powerful but nevertheless it is also possible to generate strong password using TrueCrypt.
Starting up the program and hiding, securing or encrypting requires a few steps. The user starts by pressing the ‘Create Volume’ button which leads to the launch of the ‘TrueCrypt Volume Creation Wizard’. Once there one chooses to either encrypt by creating a virtual disk within a file, a non-system partition such as a USB key or a system partition which basically allows for the encryption of the operating system as a whole. In one of the more typical uses, the ‘disk within a file’, the next step is to choose between a ‘normal’ encrypted disk or a hidden volume which basically hides the encrypted data inside another area so as to make it possible to deny any data is encrypted at all, what is called plausible deniability. Then the user chooses a location for the so-called file, the type of encryption, the size of the container or file, a password (and keyfiles if preferred) and finally between FAT or NTFS for the format of the volume.
When the program is launched the user will see something like the image below where the encrypted file becomes accessible as a drive.
For increased security check ‘never save history’ and keep ‘cache passwords and keyfiles in memory’ unchecked (see image above).
Many command line options that can ease the use of and for example automate mounting of encrypted drives plus many other explanations including a very easy to follow tutorial are all available at www.truecrypt.org/docs. TrueCrypt is currently at version 6.1a and supported by a good community and a detailed site.