Security principles say that if someone else has physical access to a machine, then there is no security/privacy. I'm wondering about some examples of this in the case where I want to have a hosted Virtual Private Server (VPS) with full disk encryption. This is the kind of encryption that you are offered the option of setting up when installing Ubuntu, where every partition of yours (root, home, swap, etc) is in one big LUKS-encrypted volume.  Let's assume you don't set up automated entry of the LUKS password on this VPS (instead entering it manually through SSH upon each reboot, using a creative solution like ), so that someone else trying to reboot your system would have to know the password.  What are the security or privacy risks with such a solution? Could the VPS hosting companies employees or some middle man somehow get access to your data? Sure they can take a snapshot of your entire server at any time, but in order to boot it up they'd need the password, so how could they access what's inside the image?  Could they somehow snoop the SSH keys or encryption password?  Because they have root on the physical machine that hosts the VPS instances, how possible is it for them to get root on my VPS?  Can they log key strokes sent to the VPS over SSH? If SSH secures only the communication until it gets decrypted at the server, then could they see what you are actually sending to the server?  I'm assuming the damage would be possible when your server is running, not when it is turned off, is that correct? So when the server is running (after you've already entered the LUKS password), what could they do? If they take a snapshot of your system then, what can they do with it?  Just trying to understand what security/privacy I'm getting vs what I'm not by doing full disk encryption on a server that somebody else has physical access to (i.e. VPS).
I am curious if it is possible to have a VPS that has data on it that is not readable by the hosting provider, but is still usable on the VPS.  Obviously there are some things that you could do to prevent them from reading anything...   You could change all the passwords, including root. But then, they could still use some alternate boot to reset the password, or they could just mount the disk another way. So, you could encrypt the disk or at least some of the contents on the disk. But then it seems that if you decrypted the content, they could still "peer in" to see what you were doing at the console, because after all, the virtualization platform should allow this. And even if you could stop that, it seems they could just read the RAM of the VPS directly.   Of course, the VPS can store data on it and as long as the key is not on the VPS and the data is never decrypted there, then the host cannot get the data.  But it seems to me that if any point the data on the VPS is decrypted...for use on the VPS...then the hosting provider can get the data.  So, my two questions are:   Is this correct? Is it true that there is no way to 100% secure data on a VPS from a host from seeing it, while keeping it accessable by the VPS? If it is possible to make it 100% secure, then how? If it is not possible, then what is the closest you can get to hiding data from the web host?
What exactly is a hat?  I have seen a lot of people arguing the significance of hats and the limited edition hats. I know the hats are sort of linked to the Winterbash stuff, but what exactly is a hat, what does it do, how do I get one?  Is there a full list of hats? Finding the dual basis for the space of polynomials of degree $\leq$ 2 Let $V$ be the space of polynomials of degree at most $2$, with basis $\{1,x,x^2 \}$.Find the dual basis to $\{1,x,x^2\}$.   I know that the dual basis of $\{f_1,f_2,f_3\}$ is the basis $\{f_1^*,f_2^*,f_3^*\}$ where $f_i^*(a_1f_1,\ldots,a_3f_3)$ but I'm not sure how to actually compute the dual basis. Isomorphism of a product $C_n \times C_m$ of cyclic groups with the cyclic group $C_{mn}$ Using QGIS 3 graphical modeler I created a model with a variety of input parameters (> 10). When starting the model, a nice user interface is generated. But the arrangement of the GUI elements is totally confused and apparently unpredictable during creating the model. It does neither seem to depend on the arrangement of input parameters in the graphical modeler nor on the chronological order in which the input parameters are added to the model.   Is there a way that let's me arrange the GUI elements in the order I desire? Getting a vector into a function that expects a vector $\mathbb{R}$ \ $\mathbb{Q}$ and $\mathbb{R}^2\setminus\mathbb{Q}^2$ disconnected? How can I disable cloud-init? I have a fully-configured instance and an image from that for an autoscaling group. When autoscaling new instances from this image, it calls cloud-init. cloud-init changes the hostname and breaks fstab.  I want to prevent cloud-init from starting on instance launch. I was wondering about generic installations of all applications in linux. And what that means? Well, when I was using windows I knew that if I want to install an application I am double-clicking the .exe file and then next,next,next.  In linux, I have understood that maybe there is a common (not generic) way to install any application. Installing from source maybe? Well is there any step by step method that can be used to install  application like in windows or not?  I am asking because I do not want to keep asking the google, how to? So, I have managed to install recently from source freecad from  and I think that it would be a very nice start as common method, right?  But the thing then is where to find the right source and when an application has a very unique method of installation! Apache: Scammers point dozens of domain names at my dedicated IP. How to prevent this? For the sake of discussion, pretend that I have an Apache webserver which serves a website at www.example.org. This domain name resolves to the public IP address at 192.168.1.100 (pretend this is a public IP).  The discussion at  demonstrates that anyone can point their domain at my IP. Apache won't prevent this by default, but an administrator can deal with these one at a time through use of a blacklist.  However, it's becoming more common for scammers to register dozens of domains (or more) for use in a scam. I'm concerned about the following possible attack:   A scammer registers hundreds of domain names, and points them at my dedicated IP address. The scammer directs search engines at their scam domains, thus using my content to increase their standing in the search engines. Later, the scammer moves their domain names to point to their own servers which host a scam/porn, or a competing business, etc. thereby reaping the benefits of their standing in the search engines. Some of these domains might be used to in  as well. Profit!!   I believe I have seen scammers using this trick in the past, involving dozens of domains. We didn't realize the scam implications at the time, and assumed these were misconfigured domains.  Is there a term for this nefarious SEO trick? SEO masquerading? DNS Diversion?  How could I prevent this using Apache? I'm considering a "whitelist" fix based on using a default VirtualHosts, ServerNames &amp; ServerAliases so that Apache only responds to requests where these white-listed ServerNames appear in the "Host: " header. Everything else would be rejected (or redirected to a particular page). However, I am unsure if this is the best approach.  For example, I've configured the domain  to point at the IP for Serverfault.com. You can see the results here:  . "How are" or "How is" the wife and kid? How are the wife and kid?   How is the wife and kid?      Which is more correct? Return dynamically allocated memory from C++ to C My 1.12 solution can be found . When trying to update command blocks to 1.13, I have the following:  scoreboard objectives add invert dummy   (run at start) then:  scoreboard players set FakePlayer invert 1   (impulse unconditional repeat) chained into:  execute at @e[tag=summoned] run scoreboard players reset FakePlayer invert   (chain unconditional repeat) chained into:  execute if score FakePlayer invert = 1 invert run say "All summoned animals are dead!"   This should reset FakePlayers score continuously until all entities with tag "summoned" are dead, then it should run the final condition. This does not happen, and I can't see why. How to delete duplicate LiDAR points? How can I delete duplicate LiDAR points? I incorrectly read the same las twice and saved as a one file resulting in duplicate XY points.  How should I delete these duplicate points? Wrong favicon displayed on Google's mobile SERP For some time now, Google has been displaying a website's favicon next to its title on the mobile SERP according to    But, for one website that I am managing, it is showing a completely different favicon. You can see it if you open the  on a mobile device, I am talking about the orange one:  I am referring to the top result.  As you can see on the , the favicon has been added correctly using the proper meta tag:   &lt;link  rel="icon" type="image/x-icon" href="https://www.hoofgroove.ch/pub/media/favicon/default/favicon.ico" /&gt;   This is according to .  Also, all the browsers are displaying the correct favicon, which is not the orange one but the black&amp;red one.  This meta tag has been used for weeks and also the  has always been the correct one as far as I can tell.  But for some reason, Google is showing the wrong favicon on its mobile SERP.  Any ideas why? So I was playing around on Area 51 hoping for further news on the private beta for ebooks, and noticed that my avatar (a hand) was missing. Also the Area 51 has the old toolbar. So I looked at the flair page. The network flair has my hand, the Area 51 flair has a quilt. OK, so time to upload a new image, and WordPress -- WordPress -- I don't want to login to WordPress. Any idea what's up with that?  The following questions did not help, and have different causes and symptoms: I am making a test where I am asked to add the missing words.     [...] chair is [...] useful piece of furniture.    I would have said that a is the missing word in both the cases, but the test says the words I should have added are the and a respectively.     [...] last time I saw [...] bear, I was travelling in [...] Europe.   I would have added: nothing, a, nothing. The correct answer is: the, a, nothing.  Why is the the correct article to use in both the sentences? Why rationalize the denominator? In grade school we learn to rationalize denominators of fractions when possible. We are taught that $\frac{\sqrt{2}}{2}$ is simpler than $\frac{1}{\sqrt{2}}$.  says that "there is a bias against roots in the denominator of a fraction". But such fractions are well-defined and I'm failing to see anything wrong with $\frac{1}{\sqrt{2}}$ - in fact, IMO it is simpler than $\frac{\sqrt{2}}{2}$ because 1 is simpler than 2 (or similarly, because the former can trivially be rewritten without a fraction).  So why does this bias against roots in the denominator exist and what is its justification? The only reason I can think of is that the bias is a relic of a time before the reals were understood well enough for mathematicians to be comfortable dividing by irrationals, but I have been unable to find a source to corroborate or contradict this guess. I keep going around in circles with this problem:  Given the functions $f:X\to Y$ and $g:Y\to Z$, if $g\circ f:X\to Z$ is bijective, then prove $f$ must be one-to-one and $g$ must be onto. I was able to prove this without difficulty. However the second part of the problem has me stumped:  a) Find functions $f,g$ where $g\circ f$ is bijective but $f$ fails to be onto.  b) Find functions $f,g$ where $g\circ f$ is bijective but $g$ fails to be one-to-one.  My attempt for (a): Let $f:\mathbb{R}\to \mathbb{R}^+$ be defined by $f(x)=e^x$ and $g:\mathbb{R}^+\to \mathbb{R}$ be defined by $g(x)=\ln(x)$. Then $g\circ f(x)=g(f(x))=g(e^x)=\ln(e^x)=x$ which is bijective, $g$ is onto and $f$ fails to be onto... or so I thought. Upon closer inspection $f$ $\underline{is}$ onto for the given codomain $\mathbb{R}^+$.  And now I'm stuck in a rut. Anyone out there have any hints? The $n$ complex $n$th roots of a complex number $z$ Find the maximum value of the expression ${\frac {x}{1+x^2}} + {\frac {y}{1+y^2}}+{\frac {z}{1+z^2}}$. Find the maximum value of the expression :   $${\frac {x}{1+x^2}} + {\frac {y}{1+y^2}}+{\frac {z}{1+z^2}}$$   where $x,y,z$ are real numbers satisfying the condition that $x+y+z=1$.   Taking $x=y=z=\frac {1}{3}$, I get the expression as $\frac {3x}{1+x^2}$, which is equal to $\frac {1}{1+{\frac{1}{9}}}$ or $\frac {9}{10}$.  How can I actually solve the problem without making unnecessary assumptions ?