TrueCrypt [TrueCrypt is not exactly "Open Source", but the source is available. See the reviews to get more information.] TrueCrypt is a disk encryption software for... Free Open Source Mac OS X Windows Linux Drive Encryption Portable Add a feature 855 Like Discontinued Currently unmaintained. Last version, TrueCrypt 7.1a, is still available for download and development has continued via the forks https://alternativeto.net/software/veracrypt/ and https://alternativeto.net/software/ciphershed/. "The development of TrueCrypt was ended in 5/2014 after Microsoft terminated support of Windows XP. Windows 8/7/Vista and later offer integrated support for encrypted disks and virtual disk images."