This is equally parts invigorating and frustrating. Unfortunately, this excitement is often tempered by frustration because access to most research papers costs a ridiculous amount of money. More and more journals are adding free, open-access options, but many of the big hitters ScienceNature continue to charge exorbitant amounts for one-time access to individual articles. Thus the impetus for this article.
News and updates from the Project Zero team at Google Wednesday, January 3, Reading privileged memory with a side-channel Posted by Jann Horn, Project Zero We have discovered that CPU data cache timing can be abused to efficiently leak information out of mis-speculated execution, leading to at worst arbitrary virtual memory read vulnerabilities across local security boundaries in various contexts.
So far, there are three known variants of the issue: Spectre variants 1 and 2 Meltdown variant 3 During the course of our research, we developed the following proofs of concept PoCs: This PoC only tests for the ability to read data inside mis-speculated execution within the same process, without crossing any privilege boundaries.
A PoC for variant 1 that, when running with normal user privileges under a modern Linux kernel with a distro-standard config, can perform arbitrary reads in a 4GiB range  in kernel virtual memory on the Intel Haswell Xeon CPU.
On the Intel Haswell Xeon CPU, kernel virtual memory can be read at a rate of around bytes per second after around 4 seconds of startup time. Before the attack can be performed, some initialization has to be performed that takes roughly between 10 and 30 minutes for a machine with 64GiB of RAM; the needed time should scale roughly linearly with the amount of host RAM.
If 2MB hugepages are available to the guest, the initialization should be much faster, but that hasn't been tested. We believe that this precondition is that the targeted kernel memory is present in the L1D cache. For interesting resources around this topic, look down into the "Literature" section.
A warning regarding explanations about processor internals in this blogpost: This blogpost contains a lot of speculation about hardware internals based on observed behavior, which might not necessarily correspond to what processors are actually doing.
We have some ideas on possible mitigations and provided some of those ideas to the processor vendors; however, we believe that the processor vendors are in a much better position than we are to design and evaluate mitigations, and we expect them to be the source of authoritative guidance.
An instruction retires when its results, e. Instructions can be executed out of order, but must always retire in order. A logical processor core is what the operating system sees as a processor core.
With hyperthreading enabled, the number of logical cores is a multiple of the number of physical cores. In this blogpost, "uncached" data is data that is only present in main memory, not in any of the cache levels of the CPU.
Loading uncached data will typically take over cycles of CPU time. A processor can execute past a branch without knowing whether it will be taken or where its target is, therefore executing instructions before it is known whether they should be executed.
If this speculation turns out to have been incorrect, the CPU can discard the resulting state without architectural effects and continue execution on the correct execution path.
Instructions do not retire before it is known that they are on the correct execution path. The time window during which the CPU speculatively executes the wrong code and has not yet detected that mis-speculation has occurred.Algorithm Overview.
LZSS is a dictionary encoding technique. Unlike Huffman coding, which attempts to reduce the average amount of bits required to represent a symbol, LZSS attempts to replace a string of symbols with a reference to a dictionary location for the same string.
These include various sites of pseudo-code writing tutorials/information and desk checking. Table 2: Useful Links with extra information and various examples to practice Link Difference Level of useful.
N-back is a kind of mental training intended to expand your working memory (WM), and hopefully your intelligence (IQ 1).. The theory originally went that novel 2 cognitive processes tend to overlap and seem to go through one central torosgazete.com it happens, WM predicts and correlates with IQ 3 and may use the same neural networks 4, suggesting that WM might be IQ 5.
Fulfillment by Amazon (FBA) is a service we offer sellers that lets them store their products in Amazon's fulfillment centers, and we directly pack, ship, and provide customer service for these products.
Frequently Asked Question List for TeX. Pseudocode is a kind of structured english for describing algorithms.
It allows the designer to focus on the logic of the algorithm without being distracted by details of language syntax. At the same time, the pseudocode needs to be complete.