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Cold Boot Attacks

15. Prosinec 2009, 15:30 (1330x zobrazeno)

To execute the attack, the machine is cold booted (power is cycled "off" then "on" without letting the computer shut down cleanly); a light-weight operating system is then immediately booted (e.g. from a USB flash drive), and the contents of pre-boot memory dumped to a file. Alternatively, the memory modules are removed from the original system and quickly placed in another machine under the attacker's control, which is then booted to access the memory. Further analysis can then be performed against the information that was retrieved from memory to find the sensitive keys contained in it.

The attack has been demonstrated to be effective against full disk encryption schemes of various vendors and operating systems, even where a Trusted Platform Module (TPM) secure cryptoprocessor is used. This is because the problem is fundamentally a hardware (insecure memory) and not a software issue. While the focus of current research is on disk encryption, any sensitive data held in memory are vulnerable to the attack.

The time window for an attack can be extended to hours by cooling the memory modules. Furthermore, as the bits disappear in memory over time, they can be reconstructed, as they fade away in a predictable manner. In the case of disk encryption applications that can be configured to allow the operating system to boot without a pre-boot PIN being entered or a hardware key being present (e.g. Bitlocker in a simple configuration that uses a TPM without a two-factor authentication PIN or USB key), the time frame for the attack is not limited at all.