Disk encryption easily defeated, research shows

Researchers at Princeton University's Centre for Information Technology Policy have published results of research that shows Vista, Mac OX and Linux disk encryption products can be easily defeated.

With so much attention focused on securing data stored on mobile devices including laptops, the research revealed yesterday that these common disk encryption products could be cracked by 'cold boot' attacks could cause concern among IT organisations.

The research demonstrates how to steal the hard drive encryption key used by Windows Vista's BitLocker, Apple's FileVault or Linux's dm-crypt and how, with that key, hackers could get access to all of the data stored on an encrypted hard drive.

The method takes advantage of the physical properties of the computer's memory chips or dynamic random access memory (DRAM). The researchers have found residual data can linger for minutes in the DRAM as the computer shuts down or is in hibernation mode.

Alex Halderman, a Princeton graduate student who worked on the research paper, wrote in his blog: "Our results show that an attacker can cut power to the computer, then power it back up and boot a malicious operating system (from, say, a thumb drive) that copies the contents of memory."

Once copied, the attacker can search through the captured memory contents, find any cryptographic keys it may store, using them to unlock and decrypt the hard disk contents.

"We show very effective methods for finding and extracting keys from memory, even if the contents of memory have faded somewhat (i.e., even if some bits of memory were flipped during the power-off interval)," he said. "If the attacker is worried that memory will fade too quickly, he can chill the DRAM chips before cutting power."

He added that even those systems that wipe the memory when they boot up could be vulnerable using the cooling method, where chips are frozen to -50 degrees Celsius, giving the researchers time to install the memory in another PC that would boot without wiping out the data.

The research team was led by Princeton University, with researchers from the digital rights, Electronic Frontier Foundation and device software optimisation vendor, Wind River Systems.

Although Microsoft, Apple and some commercial Linux vendors had not responded to requests for comment at the time of writing, Symantec's chief scientist Guy Bunker told IT PRO the findings demonstrate the growing complexity of systems and devices.

"The first thing to observe is that encryption technology from ten years can almost now be broken with a Casio watch. It's a war out there and hackers realise, that with enough motivation to break technologies, the gains are worth the effort," he said.

"But the great thing about software today is that we can issue patches for these things that would, for instance, overwrite the memory on shutdown so the hacker could then look at residual memory to his heart's content."