Disk encryption is no silver bullet, researchers say
SAN JOSE, Calif.--Disk encryption, which people rely on for protecting sensitive data on laptops, can fairly easily be foiled, security researchers said in presenting a paper on a so-called "cold-boot attack" at the Usenix security conference on Wednesday.
In a new type of attack that requires physical access to a target computer, an attacker can cut power to a machine that is in sleep mode, restore the power, and boot a malicious operating system from a USB drive or an iPod that can copy the RAM contents.
But won't the contents of the RAM be lost when the power is turned off? Actually, no, according to the team of mostly Princeton University researchers led by J. Alex Halderman, a doctoral candidate.
The group found that contrary to common knowledge, RAM data fades gradually over a period spanning from a few seconds to a few minutes after the power is cut. This could give an attacker time to read the RAM data, including encryption keys, after rebooting into a different operating system or removing the memory chips and placing them into a different computer.
This image shows how data on a RAM chip fades gradually over time. The far left shot shows an image in memory five seconds after the power was cut, followed on the right by 30 seconds, 60 seconds and 5 minutes.
(Credit: Center for Information Technology at Princeton University)An attacker can extend the data decay time period by cooling the chip off while the machine is running with a spray of "canned air" commonly used for cleaning keyboards of dust. With liquid nitrogen, an attacker could take days to retrieve the data if needed.
Popular disk encryption schemes like Microsoft's Bitlocker in Vista don't protect against this type of attack, and actually make the laptops more susceptible, the researchers said.
"Overall, the significance is that disk encryption is not the silver bullet that we might have thought in its present state," Halderman, said in an interview after the presentation. "Individuals and businesses that rely on disk encryption need to pay much closer attention to the physical security of their devices."
In addition to Halderman, the research team included Princeton professor Ed Felten, as well as Nadia Heninger, William Clarkson, Joseph Calandrino, and Ariel Feldman of Princeton; Jacob Appelbaum; Seth Schoen of the Electronic Frontier Foundation; and William Paul of Wind River Systems.
This video created by the research team explains how the attack is done:
Elinor Mills covers Internet security and privacy. She joined CNET News in 2005 after working as a foreign correspondent for Reuters in Portugal and writing for The Industry Standard, the IDG News Service, and the Associated Press. E-mail Elinor. 
Of course a CNET writer wouldn't know this.
As the contents of the memory fades, bits of data are being lost (actually, just randomized), but the picture of the Mona Lisa is still recognizable, even when 70 or 80% of the bits that represent it are lost. In contrast, if only a single bit of an encryption key is lost, the key would not work.
If you think this method of retrieving encryption keys is cool, you should check out this YouTube video of how to make a pair of hover shoes with 4 magnets and 2 9volt batteries:
http://www.youtube.com/watch?v=40S8G2ZuRpE
If you use a FDE (full-disk-encryption) enabled drive, which does the encryption on a hardware/firmware basis, this hack is (so far) not usable.
Appreciate if someone knowledgeable clears the air.
- by ferretboy88 July 31, 2008 3:25 PM PDT
- Why did you even invent this software? Thanks for making this easy to use software and telling the bad guys about it. Thanks for helping them out. Now start working on a program to prevent this.
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- by Imalittleteapot July 31, 2008 5:25 PM PDT
- This is how computer security works. First rule of security is that no matter what you design, it can be hacked. So businesses can't rebuild stuff just because it might be insecure. Everything is insecure. All that matters is if someone currently knows how to hack it. If you can't prove it can be hacked then a company isn't going to fix anything. So the researchers are just proving it can be hacked. It is better that these tools are in the hands of both researches and the bad guys instead of the just the bad guys. Now the problem can be addressed in the future. Typically you can't defend yourself from an attack when you don't understand how it works. That's why it is critical that researchers figure out these attacks work so they can be explained to us so that protections can be built.
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