Cold Reboot Attacks on Disk Encryption

jcrouthamel writes "Contrary to popular assumption, DRAMs used in most modern computers retain their contents for seconds to minutes after power is lost, even at operating temperatures and even if removed from a motherboard. Although DRAMs become less reliable when they are not refreshed, they are not immediately erased, and their contents persist sufficiently for malicious (or forensic) acquisition of usable full-system memory images. We show that this phenomenon limits the ability of an operating system to protect cryptographic key material from an attacker with physical access. We use cold reboots to mount attacks on popular disk encryption systems — BitLocker, FileVault, dm-crypt, and TrueCrypt — using no special devices or materials. We experimentally characterize the extent and predictability of memory remanence and report that remanence times can be increased dramatically with simple techniques. We offer new algorithms for finding cryptographic keys in memory images and for correcting errors caused by bit decay. Though we discuss several strategies for partially mitigating these risks, we know of no simple remedy that would eliminate them."

Comments

Bad Movie Plot

[mlwmohawk]

This is one of those exploits that sound real and possible but in reality so unlikely that it is basically a bad movie plot.

DRAM decays very fast. Minutes? I don't think so. The longer a DRAM cell stays charged the more current it takes to change its state. If anything they decay faster today than before. But, for arguments sake, lets say, on average a DRAM will be 100% intact for 30 seconds and total decay to random in 1 minute.

Get your screwdrivers handy.

Try 1, reboot computer. Oops@! POST clears memory at startup.
Try 2, power off computer, remove RAM, oops! touched ram static discharge randomized most data on ram.
Try 3, power off computer, with anti-static clothing, remove RAM, put ram in device to read it. Oops!! when the computer powers down, it seems it writes crap to ram as it is losing power.
Try 4, remove ram from powered computer, OOPS! crashing computer that loses RAM goes off into the weeds, as RAM is removed it remains partially powered and some, not all, of the address and data lines remain briefly connected, RAM is scrambled.

Try 5, you manage to remove the RAM successfully without it getting scrambled by the removal. You have a specially constructed device that allows the RAM to be plugged in and starts the refresh cycle. You dump the RAM, wait!!! you need ALL the RAM modules.

Try 6, you manage to remove all the ram modules in the computer, simultaneously and instantaneously, and get them into the fore mentioned device in less than 30 seconds. What are you really going to see that you couldn't get off the hard disk or swap partition, remember the machine has to be on.

Re:Clear the DRAM?

[theaveng]

For this to work, somebody has to be able to steal my laptop, hack the double-password system, and get Windows up-and-running. Only then can they apply this "power off/power up" method of copying my RAM.

I am not concerned; they'd have a difficult time guessing both passwords. And with the program I use (or rather the government uses), the hard drive is hard formatted after 10 incorrect guesses, leaving behind no information.

I feel secure.

However, I can see this as an effective method to steal other keys... like the Blu-ray key out of PowerDVD.

While Communist Linsux causes Lower dick errection

[Anonymous Coward]

So the shitdot sheeple can't get fucking laid as a result of this and their shrinking dicks. The shitdot sheeple should just fucking end it right now by slitting their fucking wrists.