Simultaneous Multithreading
Simultaneous multithreading ¡ª put simply, the shar-ing of the execution resources of a superscalar processor betweenmultiple execution threads ¡ª has recently become widespread viaits introduction (under the name ¡°Hyper-Threading¡±) into IntelPentium 4 processors. In this implementation, for reasons of ef-ficiency and economy of processor area, the sharing of processorresources between threads extends beyond the execution units; ofparticular concern is that the threads share access to the memorycaches.We demonstrate that this shared access to memory caches pro-vides not only an easily used high bandwidth covert channel be-tween threads, but also permits a malicious thread (operating, intheory, with limited privileges) to monitor the execution of anotherthread, allowing in many cases for theft of cryptographic keys.Finally, we provide some suggestions to processor designers, op-erating system vendors, and the authors of cryptographic software,of how this attack could be mitigated or eliminated entirely.1. IntroductionAs integrated circuit fabrication technologies have improved, provid-ing not only faster transistors but smaller transistors, processor design-ers have been met with two critical challenges. First, memory latencieshave increased dramatically in relative terms; and second, while it iseasy to spend extra transistors on building additional execution units,many programs have fairly limited instruction-level parallelism, whichlimits the extent to which additional execution resources can be uti-lized. Caches provide a partial solution to the first problem, whileout-of-order execution provides a partial solution to the second.In 1995, simultaneous multithreading was revived1in order to com-bat these two difficulties [12]. Where out-of-order execution allowsinstructions to be reordered (subject to maintaining architectural se-mantics) within a narrow window of perhaps a hundred instructions,Key words and phrases. Side channels, simultaneous multithreading, caching.1Simultaneous multithreading had existed since at least 1974 in theory [10], evenif it had not yet been shown to be practically feasible.
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simultaneous multithreading allows instructions to be reordered acrossthreads; that is, rather than having the operating system perform con-text switches between two threads, it can schedule both threads simul-taneously on the same processor, and instructions will be interleaved,dramatically increasing the utilization of existing execution resources.On the 2.8 GHz Intel Pentium 4 with Hyper-Threading processor,with which the remainder of this paper is concerned2, the two threadsbeing executed on each processor share more than merely the execu-tion units; of particular concern to us, they share access to the memorycaches [8]. Caches have already been demonstrated to be cryptograph-ically dangerous: Many implementations of AES [9] are subject to tim-ing attacks arising from the non-constancy of S-box lookup timings [1].
In the movie Run Lola Run, a lot of editing concepts were use more than once. One of them that I specifically notice was parallel editing. For example when Lola leaves her father’s work empty handed, she begins to run to meet Mani. As time begin to run out you see three different shots on the screen of Mani, Lola and the ticking clock. You can hear the ticking clock as Lola ask Mani to wait for her. Although they’re together on the screen, they are apart by a few seconds. You can see that when Lola gets close to the supermarket and you see a long shot of Mani. Another concept was the graphic match at the end of the first timeline. When the red bag was falling in the air, to Lola red phone falling. Also there were a lot of eye line match. For
In this section we investigate attacks and threats to our primary devices. These attacks and threats are built off of the vulnerabilities the previous section and help to determine which security controls would be most valuable against future attacks.
While it is true that not many programs right now are able to take advantage of more than four threads at any given time, it’s good to have them for those programs that are multi threaded which are increasingly becoming more common.
45. What does the term 'mutual simultaneous shaping' mean? Why is this desirable? How is this different than a laboratory study? Mutual simultaneous shaping is the fact that there are so many variables in every situation that it is hard to assume cause and effect. Everything affects everything, making it confusing to lead the effect to one specific cause. This can be desirable because you can capture the complexity of the situation and the situation/interaction is not limited only a few elements.
In the rapidly developing field of computer science, there is no more controversial issue than encryption. Encryption has become a highly contested issue with the broad use of global networks including the Internet. As more and more sensitive documents are being placed on computer networks, and trusted information is being sent from computer to computer throughout the world, the need for encryption has never been greater. However, the effects of encryption on our lifestyle and the government's role in encryption has been (and will continue to be) debated for years to come.
...h this device that can be disabled because it contain its own key to be encrypted. After great opposing and more complex encryption methods the government lost interest in the chip.
People live in a society that encourages getting as many things done as quickly as possible. Whether they realize it or not, multitasking as become a part of their everyday lives. They perform multiple tasks at the same time in order to save time. They use multiple electronics to take more in all at once. Multitasking can seem to be the more efficient way to handle things because people can spend the same amount of time on several tasks as opposed to just one. However, they do not stop to think of the amount of effort it takes the multitask and the consequences that can come along with it. Several experiments have been performed to determine just how detrimental multitasking can be. Attempting any form of multitasking
In this research paper, we will present you that In previous Decade side channel attacks show us that cryptographic Devices are vulnerable or we can say these devices can leak important information. In previous days cryptanalysis assumed that advance user can only has access to data pair which is to be input or output, has no knowledge of the internal state of Device. But today adversary can access the data by using spe...
My knowledge has grown over the past six years, outwith the areas of learning offered by school courses, and I see this course as an opportunity to gain new skills and broaden my knowledge further. My main interests are varied, including communications and the internet, system analysis and design, software development, processors and low level machine studies. I have recently developed an interest in data encryption, hence my active participation in the RSA RC64 Secret-Key challenge, the latest international de-encryption contest from the RSA laboratories of America.
...licy | Issues with `trusted computing', Proceedings of PODC '03, July 13-16, 2003, Boston, Massachsetts, USA, ACM, 2003, pp. 3{10.
Various protocols have been designed to ensure coherence in hardware and policies made to prevent the existence of shared writable data in more than one cache at the same time.
Virtualization technologies provide isolation of operating systems from hardware. This separation enables hardware resource sharing. With virtualization, a system pretends to be two or more of the same system [23]. Most modern operating systems contain a simplified system of virtualization. Each running process is able to act as if it is the only thing running. The CPUs and memory are virtualized. If a process tries to consume all of the CPU, a modern operating system will pre-empt it and allow others their fair share. Similarly, a running process typically has its own virtual address space that the operating system maps to physical memory to give the process the illusion that it is the only user of RAM.
Wolf, D. (2013), Qualcomm: Cometh the Reaper, [Online], Available on: http://siliconhutong.com/category/hardware-and-silicon/, (Accessed on 2 March 2014).
Computers are very complex and have many different uses. This makes for a very complex system of parts that work together to do what the user wants from the computer. The purpose of this paper is to explain a few main components of the computer. The components covered are going to be system units, Motherboards, Central Processing Units, and Memory. Many people are not familiar with these terms and their meaning. These components are commonly mistaken for one and other.
computer architecture Computer architecture covers the design of system software, such as the operating system (the program that controls the computer), as well as referring to the combination of hardware and basic software that links the machines on a computer network. Computer architecture refers to an entire structure and to the details needed to make it functional. Thus, computer architecture covers computer systems, microprocessors, circuits, and system programs. Typically the term does not refer to application programs, such as spreadsheets or word processing, which are required to perform a task but not to make the system run.