Disk encryption compromised
A couple of days ago I posted a small guide to use encrypted disk images in Mac OS X instead of Apple’s FileVault feature. Disk encryption is the solution to store your data in a secure manner… I thought. You won’t believe this but a group of researchers developed an attack against disk encryption software. The problem is that the secret you have to enter to decrypt the data is stored in RAM (obviously). When you turn off your computer the data in RAM will fade. This will take seconds to minutes. The researchers have developed a small tool to capture the RAM contents to disk and hunt down the secret used to encrypt the data…
It doesn’t take a whole lot of exotic or hard-to-get equipment. Just a computer that is left behind for a while and some software. Most disk encryption products can be compromised this way. Really scary stuff. Maybe the encryption software should use the hash of your secret instead of the plain secret. That way you first have to find a word that yields the same hash the program found in memory. Here you can read all about the attack on disk encryption including a nice video that demonstrates the attack. For now, just to be secure, I will kill anybody within five meter distance from my computer… you’ve been warned.
Update: What is safe nowadays? Even GSM encryption can be broken in 30 seconds (at the cost of $100.000).
February 23rd, 2008 at 17:46
Eddie, title should be: RAM compromized, nothing to see here, move along
This is a well known problem with encrypted disks that are mounted in live systems that are still running. Keys are indeed stored in memory, otherwise the file encryption software cannot encrypt/ decrypt on the fly.
If the key is not in RAM, disk encryption is not compromized (unless some stupid yankee DHS officer forces you at gunpoint to surrender you pass phrase that is, before sending you to Gitmo
Anyways, this is the reason e.g. our paranoid friends that built TrueCrypt give you to the option to dismount the disks when it goes into power saving or when the screen locks. On dismount it clears the keys from memory. Ya, they are truly paranoid. Besides wearing my tinfoil hat, I have it switched on just for this reason. To show you that my tinfoil hat wearing friends were already aware of keys stored in RAM:
http://www.truecrypt.org/docs/?s=unencrypted-data-in-ram
Whether this is possible with FileVault, I don’t know (I’m not an Apple fan boy, you know). You should check. Too bad ueber paranoid TrueCrypt can’t handle Linux file systems and uses the crummy FAT16 on Linux…