Description:

TrueCrypt is a software system for establishing and maintaining an
on-the-fly-encrypted volume (data storage device). On-the-fly
encryption means that data are automatically encrypted or decrypted
right before they are loaded or saved, without any user intervention.
No data stored on an encrypted volume can be read (decrypted) without
using the correct password/keyfile(s) or correct encryption keys.
Entire file system is encrypted (e.g.., file names, folder names,
contents of every file, free space, meta data, etc).
Files can be copied to and from a mounted TrueCrypt volume just like
they are copied to/from any normal disk. Files are automatically being
decrypted on-the-fly (in memory/RAM) while they are being read or
copied from an encrypted TrueCrypt volume. Similarly, files that are
being written or copied to the TrueCrypt volume are automatically being
encrypted on-the-fly (right before they are written to the disk) in
RAM.