TrueCrypt is a free open source which allows you to encrypt your disk. This is really useful for securing your USB thumbdrive as you wouldn’t want your documents and datas exposed to third party when it got stolen or lost. Main features are:
- Creates a virtual encrypted disk within a file and mounts it as a real disk.
- Encrypts an entire hard disk partition or a device, such as USB flash drive.
- 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, Blowfish (448-bit key), CAST5, Serpent, Triple DES, and Two fish.
- Mode of operation: LRW (CBC supported as legacy).
- Based on Encryption for the Masses (E4M) 2.02a, conceived in 1997.
If you need a tutorial on how it works, juand.ca has a pretty good tutorial on it.