On Wed, Oct 27, 2010 at 10:04:19AM -0400, Sean Swehla wrote: > The way I understand it, writing random data to a disk helps to get > around certain physical properties of magnetic media which could > allow someone identify data which had already been overwritten. The > big deal about using random data instead of all 0s or all 1s is that > having a consistent "layer" of data written makes the old data even > easier to identify.
ehhhhhh kinda sorta. The sanctioned wipe pattern is something like all 0, all 1, alternating, repeat again, and so on, for 7 wipes. A single 0/1 pass isn't going to do much. In this case it's more for hiding the start/end of the encrypted data areas. It has, as far as I know, never been proven that anyone can recover previous data after a single pass - and there's a $1m challenge still standing for anyone who can recover data after a single wipe, though I don't have a url handy at the moment. > Granted, it takes a good deal more than software to read data in > this way so you're certainly not talking about a casual thief. Also, > if it's only one partition being encrypted I would think that the > unencrypted partition would provide a much simpler start toward > cracking the encrypted partition. > Because I have to: http://xkcd.com/538/ That comic is exactly what I've been saying for a while - somewhere it's in a presentation... at some point it becomes cheaper to put you in a van and hook you to a car battery. Full-disk crypto is good for: - Getting your laptop randomly stolen - Protecting company code - Protecting personal info - Cases where you'd rather go to jail for contempt of court than for whatever you're not giving the password to It's not much good at keeping you out of jail. And I wouldn't fly internationally with an encrypted drive - I usually pull the hard drives out and use a throwaway unencrypted USB stick, with a temporary set of SSH keys. -m
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