www.truecrypt.org
Open-source free on-the-fly disk encryption for Windows, Mac OS and GNU/Linux. It can encrypt partitions or create virtual encrypted disks within files. Implemented ciphers: AES-256, Blowfish (448-bit key), 3DES, Serpent, Twofish. Provides plausible deniability.
URLs from www.truecrypt.org:
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http://www.truecrypt.org/
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http://www.truecrypt.org/screenshots.php
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http://www.truecrypt.org/downloads.php
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http://www.truecrypt.org
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http://www.truecrypt.org/docs/
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http://www.truecrypt.org/docs/?s=aes
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http://www.truecrypt.org/docs/?s=command-line-usage
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http://www.truecrypt.org/docs/?s=tutorial
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http://www.truecrypt.org/docs/?s=version-history
URL:
http://www.truecrypt.org/downloads