Cold boot attacks expose a gap between what disk encryption promises and what it delivers on a running computer. This post explains the attack mechanically, who it realistically affects, and which mitigations work.

The 2008 Princeton Paper

In 2008, a team of researchers from Princeton, the EFF, and Wind River Systems published "Lest We Remember: Cold Boot Attacks on Encryption Keys." They demonstrated that DRAM (dynamic random-access memory) retains its contents for seconds to minutes after power is removed — sometimes longer when cooled. By cutting power to a running machine, chilling the RAM modules, and booting from a custom USB tool, they dumped full RAM contents including the AES keys BitLocker, FileVault, and dm-crypt had been using to protect encrypted disks.

The fundamental physics has not changed: DRAM cells are capacitors that lose charge over time, but "over time" can mean seconds at room temperature or minutes when chilled with compressed air or liquid nitrogen.

The attack targets RAM, not…