In recent crypto there has been a trend to design ciphers using only the  - i.e. additions (modulo $2^{32}$ or $2^{64}$), rotations (by a fixed constant) and XORs, examples include , .   One of the nicer, claimed properties of such ciphers is that they are supposedly easier to implement in a side-channel resistant fashion.  Assuming one would want to implement Threefish (on a multitude of architectures such as ARM, x86 and x64), which precautions does one need to take to avoid side-channel attacks for such implementations? And are there any precautions which would be applicable to ARX designs specifically? If, which precautions against side-channel attacks can/should be taken?  What I don't count here: attacks that would work by exploiting unproperly erased/freed memory. I'm looking for the standard cryptographical side channels: cache-timing, "normal" timing and maybe (differential) power (/EM) analysis.  What I would consider "pre-cautions": any code solely intended to defeat side channel attacks while not being documented in the original specification (which usually gives only a mathematical approach).
Is there any cryptographic algorithm immune to side channel attacks based on scan chain? In VLSI point of view.
Hide or disable form options? Possible Duplicate:          On a create/edit form, where the options available to the end user will depend on their previous input, in order to give the user some guides on how to fill the data, we shall:   Disable the controls and enable them only when the pre-requisites are meet. Hide them instead Do nothing Other options   Example: when asking who is the legal representative of someone, the form will contain a combobox with the following options: the own person, their parents or someone else. Only in the case the user chooses someone else, he was to fill a textbox telling who.  Which option will provide the best user experience? Error/warning when using NSolve for simple equation Divisibility by 7 What is the fastest known way for testing divisibility by 7? Of course I can write the decimal expansion of a number and calculate it modulo 7, but that doesn't give a nice pattern to memorize because 3 is a primitive root. I'm looking for alternative ways that can help you decide when a number is divisible by 7 by hand.  I'm sorry if this is a duplicate question, but I didn't find anything similar on the site. Kinematic Viscosity How would you define ? What does it physically represent? Around the Internet I've found it defined as just a ratio, and that's it.  I saw in an answer that I can think of it as "diffusivity of momentum". What does this mean? For a physics major, what are the best books/references on Greens functions for self-studying?  My mathematical background is on the level of Mathematical Methods in the physical sciences by Mary Boas. Problem using atan in pgfplots Prove convergence of the sequence $(z_1+z_2+\cdots + z_n)/n$ of Cesaro means proving the inequality $\triangle\leq \frac{1}{4}\sqrt{(a+b+c)\cdot abc}$ Update 2014-04-17 04:47 UTC: Stable, with some odds and ends to clean up      The main MSO/MSE sites are stable, but there are plenty of corners left to sweep. For details, see:    Not all of them mind you, just Meta Stack Overflow into Meta Stack Exchange.  I'll have you know, factually, that we really did believe this would take place in six-to-eight weeks when it was , but we've finally got a tentative date established.  If things go according to plan, we'll begin the operation shortly after 8:30 PM EDT on the 16th, completing everything within a few hour window. Ideally, all service disrupting endeavors will be completed within the first hour, which include:   The availability of Meta Stack Overflow The availability of Stack Overflow (more on this shortly) The availability of Chat on Meta Stack Overflow   As you know, we'll be bolting on a standard issue per-site meta on Stack Overflow, while breaking the link between what will have become Meta Stack Exchange and Stack Overflow. There's some irritable innards in that particular region, so we'll be asking folks to expect the unexpected during the maintenance window. Affected sites will be in and out of read-only mode, or quite possibly just down for maintenance while we're doing the actual break.  I'll be posting a system message on both Meta Stack Overflow as well as Stack Overflow itself 24 hours before we begin the actual work.   Did I say tentative in a six-to-eight-something time frame again? Why yes, I did - we're currently running some tests on the dev tier to simulate the split as closely as possible, so that we can better anticipate quirks that we need to address prior to actually doing it.  Once the sites have actually been stood up functionally on the production tier, we're going to get to work on finishing touches. This will include things like site settings (which determine bits of text you see in the question prompts, rep thresholds, etc) and all sorts of other fine tuning.  Once we're done:   Stack Overflow will have a blank, empty child meta site just like every other site The new Meta Stack Exchange will be up and running All rooms on Chat Meta Stack Overflow will be moved to Chat Meta Stack Exchange  I'll send over about 150 - 200 questions from MSE to MSO, most of which will be tag or SO-specific feature related posts that got buried by the network stuff without resolution.   If the tentative date moves, I'll update this post with the new date. However, we do not anticipate this happening any later than Saturday, April 19 - in the case that we see down time we can't mitigate and need to do it on a weekend.  The ground work is basically done, we're finishing up sanity now with a great deal of confidence, and we're pretty certain that we'll hit between those dates, if not directly on the tentative 16th.  Questions? Kvetch? Anonymous confessions? Answer below, and I'll address each in comments. How can one motivate the relativistic momentum? Motivating the non-relativistic momentum $$\mathbf{p} = m\mathbf{v}$$ is quite easy: it is meant to represent the quantity of motion of the particle, and since the mass is one measure of quantity of matter it should be proportional to mass (how much thing is moving) and should be proportional to velocity (how fast and to where it is moving). Now, in Special Relativity the momentum changes. The new quantity of motion becomes $$\mathbf{p} = \dfrac{m\mathbf{v}}{\sqrt{1-\dfrac{v^2}{c^2}}}$$ Or, using $\gamma$ the Lorentz factor $$\mathbf{p} = \gamma(v) m\mathbf{v}$$ where I write $\gamma(v)$ to indicate that the velocity is that of the particle relative to the frame in which the movement is being observed. The need for this new momentum is because the old one fails to be conserved and because using the old one in Newton's second law leads to a law which is not invariant under Lorentz transformations. So the need for a new momentum is perfectly well motivated. What I would like to know is how can one motivate that the correct choice for $\mathbf{p}$ is the $\gamma(v)m\mathbf{v}$. There are some arguments using the mass: considering a colision, requiring momentum to be conserved, transform the velocity and then find how mass should transform. Although this work, it doesn't seem natural, and it is derived in one particular example. On my book there's even something that Einstein wote saying that he didn't think it was a good idea to try transforming the mass from $m$ to $M = \gamma(v)m$, that it was better to simply keep $\gamma$ on the new momentum without trying to combine it with the mass. So I would like to know: without resorting to arguments based on transformation of the mass, how can one motivate the new form of momentum that works for special relativity? How to make a complaint about grades? My professor announced the grades. He told us in each part what grades we had. My oral presentation for the project was way better than other students. But he just gave me 89 for oral and gave others 88.  I think it is not fair at all, because most of the students were not clear or the did not consider timing. He also told me that "your presentation was very good".  Also, I performed very well on the final exam but he also did not give me the 100. I think it is not fair.  How can I make a complaint? What should I write? I was asked to prove the following:  If $\{ E_1,E_2,\ldots,E_n\}$ is a fully independent set of events, prove that:  $$ P\left(\bigcup_{i = 1}^n E_i \right) = 1 - \prod_{i = 1}^n \left[ 1 - P(E_i) \right]  $$  (Hint: use complements)  I got the following:  Let $\alpha = E_1\cup E_2 \cup \cdots \cup E_n = \{E^C_1 \cap E^C_2 \cap \cdots\cap E_n^C\}^C$. Then, $\alpha^C = \{ E^C_1 \cap E^C_2 \cap \cdots \cap E^C\} $.  Assuming that the set of complements of each ${E_i}$ is also fully independent, we have:  \begin{align} &amp; P(\alpha^C) = \prod_{i = 1}^n P(E_i^C)  = \prod_{i = 1}^n \left[ 1 - P(E_i) \right] \\ &amp; P(\alpha) = 1 - P(\alpha^C) = 1 - \prod_{i = 1}^n \left[ 1 - P(E_i) \right] \\ &amp; P(\bigcup_{i = 1}^n E_i) = 1 - \prod_{i = 1}^n \left[ 1 - P(E_i) \right] \end{align}  However, even though I know (by Googling it) that my assumption is true, I'm unable to prove it so I could validly use it as a lemma. Is there another way to prove this equality? windows command prompt change directory is now changing directory I am planning to travel to India (COK airport, Kerala) from United States. I want to take my laptop as well as my tablet (iPad). Am I allowed to take both in my backpack with my documents related my work. I think I am allowed to take only one computer as per the rule. Will the customs consider my iPad as a computer?  What all I can take?   One of my friends took 2 laptops (1 work and 1 personal) and had trouble at the airport.  Also I am planning to take some wristwatches (7 of them, each avg price is 45 $). I read in a website that I can take stuff up to max 35000 INR. Is that true? In that case, how will I manage my stuff? Is it possible to install Office 365 (2013) on Ubuntu 15.04 Vivid Vervet? I would like to install Office 2015/365 on Ubuntu 15.04. I tried to install Office using Wine, but that did not work. Please note that I do not want virtualisation unless it has a -like behaviour, where application windows are treated like regular Ubuntu application windows by the system. I am looping over the features of a shapefile containing multiple polygons. If  certain criteria are met, I want to save the current feature in a new shapefile.  I am doing this using GDAL 1.10.0 with Python 2.7.3  The code runs, creates the files I want, calculates the area correctly. In the shapefile that is created, the attribute table contains the propoer fields ('name' and FID). Two things are wrong:   No polygons are visible (in ArcMap). This seems to me particularly weird, because the polygons seem to me proper, in the sense that they are closed (and the area is calculated properly).  The coordinate system seems off (in Arc Catalog there appears in the bottom -20,9667 0,0000 (are these degrees??)), despite the fact that I am creating a projection file (they are in German national grid 3)   Any hints as to what the problems could be? I tried to put the relevant excerpt of the code below:  from osgeo import gdal, gdalnumeric, ogr, osr, gdalconst  ### prepare shapefile into which to save driver = ogr.GetDriverByName('ESRI Shapefile') path_matched = r'.../.../path' datasource = driver.CreateDataSource(path_matched) lyr_matched = 'matched_%s' % cur_id  # from above # Remove output shapefile if it already exists name_shpfile = lyr_matched + '.shp' if os.path.exists(os.path.join(path_matched, name_shpfile)):     driver.DeleteDataSource(os.path.join(path_matched, name_shpfile)) layer = datasource.CreateLayer(lyr_matched, geom_type=ogr.wkbPolygon) #layer.ResetReading() field_name = ogr.FieldDefn("name", ogr.OFTString) layer.CreateField(field_name)  ### prepare file in which I want to write the areas of matched polygons path_area = path_matched file_area = 'matched_area_%s.txt' % (cur_id) fobj_area = open(os.path.join(path_area, file_area), 'w')  ### original shape file containing all polygons shp = ogr.Open(shp_all)  # os fobj from above lyr = shp.GetLayer()  # loop over polygons in original shameful for FID in featList:     feat = lyr.GetFeature(FID)      # this is from the shapefile      cur_name = feat.GetField(1)      # ... work on conditions ...      if condition = true:         myPoly = ogr.Geometry(type=ogr.wkbPolygon)         cur_poly = feat.GetGeometryRef()         myPoly.AddGeometry(cur_poly)         cur_spat_ref = cur_poly.GetSpatialReference()          cur_area =  cur_poly.GetArea()         cur_area_string = "%s \t %f \n" % (gw_name_EZG, cur_area)         fobj_area.write(cur_area_string)          featur_dfn = layer.GetLayerDefn()         feature_abc = ogr.Feature(featur_dfn)         feature_abc.SetGeometry(myPoly)         feature_abc.SetField("name", cur_name)         feature_abc.SetFID(FID)         layer.CreateFeature(feature_abc)         myPoly.Destroy()         feature.Destroy()   # generate projection file prj_filename = lyr_matched + '.prj' file = open(os.path.join(path_matched, prj_filename), 'w') targetSR = cur_spat_ref targetSR.MorphToESRI() file.write(targetSR.ExportToWkt()) file.close()   datasource.Destroy() This week I saw the definition of a measurable set for an outer measure.     Let $\mu^*$ be an outer measure on a set $X$. We call $A \subseteq X$ measurable if $$\mu^*(E) = \mu^*(A\cap E) + \mu^*(A^c\cap E)$$ for every $E \subseteq X$.   This is not the first time I've seen this definition. Unlike most other things in mathematics, over time I have gained absolutely no intuition as to why this is the definition.   The only explanation I've ever seen is that a set is measurable if it 'breaks up' other sets in the way you'd want. I don't really see why this is the motivation though. One reason I am not comfortable with it is that you require a measurable set to break up sets which, according to this definition, are non-measurable; why would you require that? Of course, you can't say what a non-measurable set is without first defining what it means to be measurable so I suppose no matter what your condition is, it will have to apply to all subsets of $X$.     Is there an intuitive way to think about the definition of measurable sets? Is there a good reason why we should use this definition, aside from "it works"? How add 14 days on end date I have End Date column and I want to add 14 Days on it auto when created, can I do it by workflow? Can I do it via jQuery. If yes how? if no how I can do it? Can markdown icons be available on the iPad? As you can see by the screenshot below, neither buttons nor even the live-preview is available on the iPad.    StackExchange is great on mobile devices, maybe it can be full available in mobile safari as well.  The same thing happens with the tags autocomplete, there is no options for it! we need to check previous questions to know what tags are available to use. Difference between $\mathbb C$ and $\mathbb R^2$ What are the basic differences between $\mathbb C$ and $\mathbb R^2$?  The points in these two sets are written as ordered pairs, I mean the structure looks similar to me. So what is the reason to denote these two sets differently?