[ISN] Security boffins attempt to freeze out cold boot crypto attack

http://www.theregister.co.uk/2009/01/19/cold_boot_countermeasures/

By John Leyden
The Register
19th January 2009

Security researchers have developed prototype countermeasures to defend 
against the recently developed cold boot crypto attack.

Cold boot is a technique for snatching cryptographic keys from memory, 
creating a means to circumvent disk encryption. A targeted machine 
that's been left hibernating would be turned off and quickly rebooted 
using an external hard drive, loaded with customised software, in order 
to extract encryption keys stored in memory.

The technique works because DRAM circuits used in modern PCs retain data 
for a short time after they are powered down, contrary to popular 
opinion. Cold boot attacks are of potential interest to both hackers and 
computer forensics experts.

Crypto boffins are on the way to defending against the attack. By saving 
cryptographic keys in CPU cache, instead of potentially vulnerable DRAM, 
the attack can potentially be frustrated.

"By switching the cache into a special mode one can force that data 
remains in the cache and is not written to the backing RAM locations," 
write the security researchers behind the Frozen Cache blog. "Thus, the 
encryption key can't be extracted from RAM. This technique is actually 
not new: LinuxBIOS/CoreBoot calls this Cache-as-RAM. They use it to 
allow "RAM access", even before the memory controller is initialized."

[...]


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