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USB Key Mode: The user must insert a USB device that contains a startup key into the computer to be able to boot the protected OS. Note that this mode requires that the BIOS on the protected machine supports the reading of USB devices in the pre-OS environment. BitLocker does not support smart cards for pre-boot authentication. [31]
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 limiting at all. [2]
Screenshot of the Syskey utility on the Windows 8.1 operating system requesting the user to enter a password.. The SAM Lock Tool, better known as Syskey (the name of its executable file), is a discontinued component of Windows NT that encrypts the Security Account Manager (SAM) database using a 128-bit RC4 encryption key.
Most computers have a reset line that brings the device into the startup state and is active for a short time after powering on. For example, in the x86 architecture, asserting the RESET line halts the CPU; this is done after the system is switched on and before the power supply has asserted "power good" to indicate that it is ready to supply ...
The first memory location the CPU tries to execute is known as the reset vector. In the case of a hard reboot, the northbridge will direct a code fetch request to the BIOS located on the system flash memory. For a warm boot, the BIOS will be located in the proper place in RAM and the northbridge will direct the reset vector call to the RAM. In ...
Using a boot-time driver that can ask for a password from the user; Using a network interchange to recover the key, for instance as part of a PXE boot; Using a TPM to store the decryption key, preventing unauthorized access of the decryption key or subversion of the boot loader; Using a combination of the above
In case of physical access, computers with TPM 1.2 are vulnerable to cold boot attacks as long as the system is on or can be booted without a passphrase from shutdown, sleep or hibernation, which is the default setup for Windows computers with BitLocker full disk encryption. [66]
In Windows NT, the booting process is initiated by NTLDR in versions before Vista and the Windows Boot Manager (BOOTMGR) in Vista and later. [4] The boot loader is responsible for accessing the file system on the boot drive, starting ntoskrnl.exe, and loading boot-time device drivers into memory.