[Infowarrior] - Cold Boot Attacks on Encryption Keys

[Richard Forno]

Cold Boot Attacks on Encryption Keys
J. Alex Halderman, Seth D. Schoen, Nadia Heninger, William Clarkson, William
Paul, Joseph A. Calandrino, Ariel J. Feldman, Jacob Appelbaum, and Edward W.
Felten

Abstract 

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.

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http://citp.princeton.edu/memory/