Disk Encryption
Don't Let Theives Get Your Information!
Disk Encryption Software (or volume-level-encryption) is used for portable devices like laptop computers and USB thumb drives. Ideally, if the computer or the drive is lost, the files become inaccessible due to the need for a passphrase to be typed in prior to bootup. For full security, a strong phrase with five or more diceware words (http://en.wikipedia.org/wiki/Diceware) is used for the best chances of defeating brute force attacks.
The difference between disk encryption software and file encryption software is that the entire volume is encrypted, so no part of the disk directory structure is available. This reduces vulnerability, since you may have important information on any part of the drive, so disk encryption is one way to keep everything hidden. Even a partly-accessible drive could contain information that would be bad if it fell into the wrong hands, or could even be used to crack the encryption on the rest of the files.
Some of the ways people try to defeat volume encryption involve cold boot attacks, which involve acquiring DRAM information from computers in a sleep state, which makes it essential for the secure computer user to power down the computer to ensure that the information is no longer in memory. Otherwise, the hardware may reveal the keys that can decrypt the disk.
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Notes and Special Information
Special note: This site is in beta mode and will be larger source for encryption related information (both kinds) in the year 2009.