Cold Reboot Attacks on Disk Encryption

The 99.9% solution that I'm happy with is: never leave my computer unattended while the hard
drive encryption keys are present in RAM.  That means I never lock the screen and walk away,
and I never suspend to ram and walk away.  I just suspend to disk and power off completely.

The only new thing this research pointed out to me is just how long it takes for unpowered
room-temperature RAM to lose its contents -- I suspected it was within a second but it's a bit
longer than that.  Anyway, this small window can be fixed by modifying the suspend-to-disk
process to also clear the RAM right before poweroff (I'm still in control of the laptop at
this point, so nobody can interrupt it).