Cold Boot Attacks on Encryption Keys
25
February
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. This phenomenon limits the ability of an operating system to protect cryptographic key material from an attacker with physical access. Cold reboots can be used to mount attacks on popular disk encryption systems — BitLocker, FileVault, dm-crypt, and TrueCrypt — using no special devices or materials. We experimentally characterise the extent and predictability of memory remanence and report that remanence times can be increased dramatically with simple techniques. New algorithms are available for finding cryptographic keys in memory images and for correcting errors caused by bit decay.
Full research paper [PDF]
1. ac adapter | March 4th, 2008 at 1:20 pm
What about simply wiping the key (i.e., unmounting the encrypted volume) when the machine is about to get screen-locked/put to sleep/hibernate? The user will have to re-enter the passphrase, to be sure.
2. kiv | March 4th, 2008 at 2:48 pm
Hi ac adapter!
Sounds like a good idea initially, I will look in to this further.
Thanks for your comment!