Memory protection | EPFL Graph Search

Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it. This prevents a bug or malware within a process from affecting other processes, or the operating system itself. Protection may encompass all accesses to a specified area of memory, write accesses, or attempts to execute the contents of the area. An attempt to access unauthorized memory results in a hardware fault, e.g., a segmentation fault, storage violation exception, generally causing abnormal termination of the offending process. Memory protection for computer security includes additional techniques such as address space layout randomization and executable space protection. Methods Segmentation Memory segmentation Segmentation refers to dividing a computer's memory into segments. A re

Designing a Virtual Runtime for FPGA Accelerators in the Cloud

Mikhail Asiatici, Nithin George, Paolo Ienne

FPGAs can provide high performance and energy efficiency to many applications; therefore, they are attractive computing platforms in a cloud environment. However, FPGA application development requires extensive hardware design knowledge which significantly limits the potential user base. Moreover, in a cloud setting, allocating a whole FPGA to a user is often wasteful and not cost effective due to low device utilization. To make FPGA application development easier, firstly, we propose a methodology that provides clean abstractions with high-level APIs and a simple execution model that supports both software and hardware execution. Secondly, to improve device utilization and share the FPGA among multiple users, we developed a lightweight runtime system that provides hardware-assisted memory virtualization and memory protection, enabling multiple applications to simultaneously execute on the device.

Ieee2016

Efficient Cache Attacks on AES, and Countermeasures

Dag Arne Osvik

We describe several software side-channel attacks based on inter-process leakage through the state of the CPU's memory cache. This leakage reveals memory access patterns, which can be used for cryptanalysis of cryptographic primitives that employ data-dependent table lookups. The attacks allow an unprivileged process to attack other processes running in parallel on the same processor, despite partitioning methods such as memory protection, sandboxing, and virtualization. Some of our methods require only the ability to trigger services that perform encryption or MAC using the unknown key, such as encrypted disk partitions or secure network links. Moreover, we demonstrate an extremely strong type of attack, which requires knowledge of neither the specific plaintexts nor ciphertexts and works by merely monitoring the effect of the cryptographic process on the cache. We discuss in detail several attacks on AES and experimentally demonstrate their applicability to real systems, such as OpenSSL and Linux's dm-crypt encrypted partitions (in the latter case, the full key was recovered after just 800 writes to the partition, taking 65 milliseconds). Finally, we discuss a variety of countermeasures which can be used to mitigate such attacks.

Springer Verlag2010

Faster Software Cryptography

Dag Arne Osvik

This thesis presents work on the efficiency and security of cryptographic software. First it describes several efforts to construct very efficient implementations of cryptographic primitives. These include the Advanced Encryption Standard (AES) as well as several popular hash functions, spanning from the old MD5 to several candidates for the upcoming SHA-3 standard. Computer architectures considered range from low-end 8-bit microcontrollers to modern high-end graphics cards, and several key techniques for optimizing such implementations are presented. Results include compact implementations of SHA-1 and SHA-256 with reduced memory footprint and more than triple and double speed, respectively, compared with other fast implementations on the same architecture. Next it presents novel cryptanalytic attacks that can be performed on processor architectures with cache memories, like those used in modern personal computers. These belong to the category of side-channel attacks, exploiting unintended information leakage from an implementation to retrieve secret keys without having to find weaknesses in the cipher itself. The attacks even allow an unprivileged process to attack other processes running in parallel on the same processor, despite partitioning methods such as memory protection, sandboxing and virtualization. Practical results include full AES key recovery in 65ms using only write access to an encrypted partition. Finally the thesis investigates a technique for reducing the number of boolean operations required to express the AES round function, resulting in a significant improvement over previous efforts. This can be useful both for very compact AES implementations in hardware and for bitslice implementations of AES, in which software simulates many copies of the same compact hardware. Such software eliminates the table lookups exploited in cache attacks, and hence this kind of implementaton can be completely immune to them.

EPFL2012

Faster Software Cryptography

Dag Arne Osvik

EPFL2012