Cold boot attack

In computer security, a cold boot attack (or to a lesser extent, a platform reset attack) is a type of side channel attack in which an attacker with physical access to a computer performs a memory dump of a computer's random-access memory (RAM) by performing a hard reset of the target machine. Typically, cold boot attacks are used for retrieving encryption keys from a running operating system for malicious or criminal investigative reasons. The attack relies on the data remanence property of DRAM and SRAM to retrieve memory contents that remain readable in the seconds to minutes following a power switch-off. An attacker with physical access to a running computer typically executes a cold boot attack by cold-booting the machine and booting a lightweight operating system from a removable disk to dump the contents of pre-boot physical memory to a file. An attacker is then free to analyze the data dumped from memory to find sensitive data, such as the keys, using various forms of key finding attacks. Since cold boot attacks target random-access memory, full disk encryption schemes, even with a trusted platform module installed are ineffective against this kind of attack. This is because the problem is fundamentally a hardware (insecure memory) and not a software issue.…

In computer security, a cold boot attack (or to a lesser extent, a platform reset attack) is a type of side channel attack in which an attacker with physical access to a computer performs a memory dump of a computer's random-access memory (RAM) by performing a hard reset of the target machine. Typically, cold boot attacks are used for retrieving encryption keys from a running operating system for malicious or criminal investigative reasons. The attack relies on the data remanence property of DRAM and SRAM to retrieve memory contents that remain readable in the seconds to minutes following a power switch-off. An attacker with physical access to a running computer typically executes a cold boot attack by cold-booting the machine and booting a lightweight operating system from a removable disk to dump the contents of pre-boot physical memory to a file. An attacker is then free to analyze the data dumped from memory to find sensitive data, such as the keys, using various forms of key finding attacks. Since cold boot attacks target random-access memory, full disk encryption schemes, even with a trusted platform module installed are ineffective against this kind of attack. This is because the problem is fundamentally a hardware (insecure memory) and not a software issue. However, malicious access can be prevented by limiting physical access and using modern techniques to avoid storing sensitive data in random-access memory. ==== Dismounting encrypted disks==== Best practice recommends dismounting any encrypted, non-system disks when not in use, since most disk encryption software are designed to securely erase keys cached in memory after use. This reduces the risk of an attacker being able to salvage encryption keys from memory by executing a cold boot attack. To minimize access to encrypted information on the operating system hard disk, the machine should be completely shut down when not in use to reduce the likelihood of a successful cold boot attack. However, data may remain readable from tens of seconds to several minutes depending upon the physical RAM device in the machine, potentially allowing some data to be retrieved from memory by an attacker. Configuring an operating system to shut down or hibernate when unused, instead of using sleep mode, can help mitigate the risk of a successful cold boot attack. === Full memory encryption === Encrypting random-access memory (RAM) mitigates the possibility of an attacker being able to obtain encryption keys or other material from memory via a cold boot attack. This approach may require changes to the operating system, applications, or hardware. One example of hardware-based memory encryption was implemented in the Microsoft Xbox. Implementations on newer x86-64 hardware are available from AMD and on Intel Willow Cove and newer. Software-based full memory encryption is similar to CPU-based key storage since key material is never exposed to memory, but is more comprehensive since all memory contents are encrypted. In general, only immediate pages are decrypted and read on the fly by the operating system. Implementations of software-based memory encryption solutions include: a commercial product from PrivateCore. and RamCrypt, a kernel-patch for the Linux kernel that encrypts data in memory and stores the encryption key in the CPU registers in a manner similar to TRESOR. Since version 1.24, VeraCrypt supports RAM encryption for keys and passwords. More recently, several papers have been published highlighting the availability of security-enhanced x86 and ARM commodity processors. In that work, an ARM Cortex A8 processor is used as the substrate on which a full memory encryption solution is built. Process segments (for example, stack, code or heap) can be encrypted individually or in composition. This work marks the first full memory encryption implementation on a general-purpose commodity processor. The system provides both confidentiality and integrity protections of code and data which are encrypted everywhere outside the CPU boundary.

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