Unencrypted Data in RAM It is important to note that TrueCrypt is
disk encryption software, which encrypts only disks, not
RAM (memory).
Keep in mind that most programs do not clear the memory area (buffers) in which they store
unencrypted (portions of) files they load from a TrueCrypt volume. This means that after you exit
such a program, unencrypted data it worked with may remain in memory (RAM) until the computer
is turned off (and, according to some researchers, even for some time after the power is turned
off
*
). Also note that if you open a file stored on a TrueCrypt volume, for example, in a text editor
and then force dismount on the TrueCrypt volume, then the file will remain unencrypted in the area
of memory (RAM) used by (allocated to) the text editor. This also applies to forced auto-dismount.
Inherently, unencrypted master keys have to be stored in RAM too. When a non-system TrueCrypt
volume is dismounted, TrueCrypt erases its master keys (stored in RAM). When the computer is
cleanly restarted (or cleanly shut down), all non-system TrueCrypt volumes are automatically
dismounted and, thus, all master keys stored in RAM are erased by the TrueCrypt driver (except
master keys for system partitions/drives — see below). However, when power supply is abruptly
interrupted, when the computer is reset (not cleanly restarted), or when the system crashes,
TrueCrypt naturally stops running and therefore cannot erase any keys or any other sensitive
data. Furthermore, as Microsoft does not provide any appropriate API for handling hibernation and
shutdown, master keys used for system encryption cannot be reliably (and are not) erased from
RAM when a computer hibernates, is shut down or restarted.
†
To summarize, TrueCrypt
cannot and does
not ensure that RAM contains no sensitive data
(e.g. passwords, master keys, or decrypted data). Therefore, after each session in which you
work with a TrueCrypt volume or in which an encrypted operating system is running, you must
shut down (or, if the hibernation file is encrypted, hibernate) the computer and then leave it
powered off for at least several minutes (the longer, the better) before turning it on again. This
is required to clear the RAM (see also the section
Hibernation File ).