Cold-Boot Attack
Definition
An attack on full-disk encryption that exploits the fact that DRAM contents fade gradually after power-off. With the chips cooled to roughly -50 degrees Celsius using inverted compressed air, key material remains recoverable for seconds to minutes, long enough to reboot into a minimal OS that dumps RAM and extracts the encryption key.
- Target
- Full-disk encryption keys held in DRAM
- Mechanism
- DRAM data remanence after power loss
- Cooling method
- Chips cooled to roughly -50 C with inverted compressed air
- Recoverable window
- Seconds to minutes
Common questions
What is the actual procedure once the RAM chips are cooled?+
The machine is rebooted, or the chips are physically transferred, into a minimal purpose-built operating system that dumps the still-fading RAM contents to external storage, and the dump is then scanned with key-recovery tools that search for the structural signature of an AES or similar encryption key schedule.
How do modern systems defend against cold-boot attacks?+
Mitigations include memory encryption features tied to the CPU, wiping key material from RAM on suspend or lock, and BIOS or firmware options that overwrite memory on boot before the operating system loads, all of which shrink or eliminate the window an attacker has to extract the key.
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