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[TrueCrypt is not exactly "Open Source", but the source is available. See the reviews to get more information.]

AxCrypt is a simple file encryption software for Windows. It integrates seamlessly with your workflow to encrypt, decrypt, store, send and work with files.

AES Crypt is an advanced file encryption utility that integrates with the Windows shell or runs from the Linux command prompt to provide a simple, yet powerful, tool for encrypting files using the Advanced Encryption Standard (AES). A Java library is also available for developers using Java to read and write AES formatted files.

LibreCrypt (formerly DoxBox) is an open-source disk encryption for Windows and the successor of FreeOTFE

Cryptonite brings EncFS and TrueCrypt to Android. You can browse, export and open EncFS-encrypted directories and files on your Dropbox and on your phone. On rooted phones that support FUSE (e.g. CyanogenMod) you can also mount EncFS and TrueCrypt volumes. TrueCrypt is only available as a command-line version at this time.

The Gnome Encfs Manager is an easy to use manager and mounter for encfs stashes. It allows you to create encrypted directories, any file that is placed in such a directory will be encrypted.

DiskCryptor is the only truly free solution, provided under GNU General Public License (GPLv3), which offers encryption of all disk partitions, including the system partition. The main criteria for open-source software is the availability of its source code under one of the open source licenses. The only open-source alternative to DiskCryptor that has comparable features is TrueCrypt. However, because of the restrictive license under which TrueCrypt is provided — the TrueCrypt Collective License — TrueCrypt cannot be classified as a truly free software, as it places limits on the use and modification of its source code by developers. There are other alternatives with similar functionality, but they are fully proprietary ones, which makes them unacceptable to use for protection of confidential data. »

Cryptkeeper is a Linux system tray applet that manages EncFS encrypted folders.

If your computer were ever to be stolen, are you certain that your personal information cannot be discovered? Jetico’s BestCrypt software automatically encrypts your files so that nobody can read the data unless they have the right password or keys.

FreeOTFE is a free, open source, "on-the-fly" (OTFE) disk encryption program for PCs running MS Windows and Windows Mobile PDAs (FreeOTFE4PDA).

This is an experimental project of porting encfs to the Windows world.

DCrypt is an encryption and decryption tool that combines in a smart way multiple algorithms. The combination of multiple strong algorithms makes it much more difficult for hackers to get the plain content of the encrypted file without the password.

LUKSUS is a tool that creates an encrypted volume and filesystem on a hardrive or other storage media as well as a filecontainer.It can use the following encryption facilities: LUKS, Truecrypt and GELI.