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Cold Reboot Attacks on Disk Encryption
Cold Reboot Attacks on Disk Encryption
Posted Mar 3, 2008 6:40 UTC (Mon) by njs (subscriber, #40338)In reply to: Cold Reboot Attacks on Disk Encryption by kevinbsmith
Parent article: Cold Reboot Attacks on Disk Encryption
Searching all of memory for a given bitstring is indeed very quick -- a few seconds. But, err, if you already know what the bitstring for the key is, why are you searching for it? What you'd really be searching for would be the data structure that's holding the key -- the OS has some way to figure out which random-looking bitstring in those gigabytes of memory is really the key, so you can too, by finding the right data structures and chasing the right pointers. AFAICT that means that the techniques you're suggesting won't work -- if the key is split into multiple pieces, then don't look for the pieces, look for the data structure that lists off where all of the pieces are so they can be found again by the OS.
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Cold Reboot Attacks on Disk Encryption
Posted Mar 8, 2008 13:55 UTC (Sat) by kevinbsmith (subscriber, #4778) [Link]
You missed the point. If you know that a key exists somewhere in RAM, it is fast and simple to read a key's worth of data starting at every byte in the system, and attempt a decode of every one until you find one that works. Brute force with one giga of attempts. No knowledge of OS, language, data structures, or app code is required, aside from knowing the encryption algorithm and key size (which is usually easy to find). Dead simple. And quite effective. Splitting the key, or having an encrypted key with its key elsewhere in RAM would foil that attack. At that point, the cracker would have to know something about the specific app and craft a custom attack, which makes the attack quite a lot more difficult/expensive. It's like locking your car so the stereo thief breaks into the unlocked car instead. It won't block a highly motivated/funded attacker, but will keep out some script kiddies. If the cost of splitting the key is near zero, it might be a good benefit/cost tradeoff.