25C3 - 1.4.2.3

25th Chaos Communication Congress
Nothing to hide

Speakers
Jacob Appelbaum
Schedule
Day Day 1 (2008-12-27)
Room Saal 1
Start time 21:45
Duration 01:00
Info
ID 2922
Event type lecture
Track Hacking
Language used for presentation en
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Advanced memory forensics: The Cold Boot Attacks

Recovering keys and other secrets after power off

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.