what problem happen if we always use IV Zero in CBC Mode?
Is AES in CBC mode secure if a known and/or fixed IV is used?
How do you solve a recurrence with a summation function inside: $t(n) = 1 + \sum\limits_{j=0}^{n-1} t(j)$ Show that  $$t(n) = 1 + \sum_{ j=0}^{n-1} t(j)$$  is the same as  $$t(n) = 2^n$$  Initial condition $t(0) = 1$ How to rename objects with python? I want to rename the number 1->picture (32) with python not the number 2->picture with the (3745), can someone help me with that ? Entity Query field condition for Webform submissions Why didn't Voldemort murder the Dursleys? Voldemort couldn't kill Harry as long as he called the Dursleys home. Why didn't he just murder the Dursleys? This would prevent Harry from being able to live there. I am travelling form Delhi (DEL) to San Francisco (SFO), I have to make a connection flight in Vienna that would take me to Frankfurt (FRA). My flight to SFO is from FRA, I have one ticket for entire journey and the flights are operated by Lufthansa or its subsidiaries.  Do I need a transit visa? My flight arrives at Vienna international airport and leaves from the same, and for second leg it arrives at Frankfurt international airport.  I asked this question as an addendum to my  but was advised to make a new post.  I hold Indian passport and valid US visa. Is it "re-offend" or "reoffend"? I want to know whether there is a hyphen in the word re-offend, or if it is spelt reoffend. I looked in Oxford English dictionary and the word "reoffend" appears, but then I checked Merriam-Webster and the word is not in there.  So is reoffend a word or is it re-offend?  I'm in Australia where we observe UK English if that matters. I am developing a game with a Minecraft-like terrain made out of blocks. Since basic rendering and chunk loading is done now, I want to implement block selecting.  Therefore I need to find out what block the first person camera is facing. I already heard of unprojecting the whole scene but I decided against that because it sounds hacky and isn't accurate. Maybe I could somehow cast a ray in view direction but I do not know how to check the collision with a block in my voxel data. Of course this calculations must be done on the CPU since I need the results to perform game logic operations.  So how could I find out which block is in front of the camera? If it is preferable, how could I cast a ray and check collisions? What are the blue dots next to App names in iOS and macOS? They disappear once you open the apps and then return to the home screen, but I can't tell what they indicate.  Are they apps that haven't been opened since an app update? Or that it thinks have never been opened (not accurate in my case, but that could be a function of a "restore" confusing the phone). Where did the "wheel" group get its name? The wheel group on *nix computers typically refers to the group with some sort of root-like access. I've heard that on some *nixes it's the group of users with the right to run su, but on Linux that seems to be anyone (although you need the root password, naturally). On Linux distributions I've used it seems to be the group that by default has the right to use sudo; there's an entry in sudoers for them:  %wheel ALL=(ALL) ALL     But that's all tangential; my actual question is: Why is this group called wheel? I've heard miscellaneous explanations for it before, but don't know if any of them are correct. Does anyone know the actual history of the term? Proof by induction that if $n \in \mathbb N$ then it can be written as sum of different Fibonacci numbers Proof that every natural number $n\in \mathbb N$, can be written as the sum of different Fibonacci numbers between $F_2,F_3,\ldots,F_k,\ldots$.  For example: $32 = 21 + 8+3 = F_8+F_6+F_4$  Research effort:  The base step it's simple:  Let $k=1$ it can be britten as $k=1=F_2$  For the inductive step I considered:  Let $k = k  F_2 =F_2+F_2+\cdots+F_2 = \sum_{i=2}^w a_iF_i, a_i =\{0,1\} $  Then if $k$ suffice I want to see if $k+1$ suffices too... But I'm not realy seeing how to use the inductive hypothesis, so I assume It's wrong.  Any thoughts on which can the inductive step be? Can you change the location where windows stores its updates? On my personal home PC I want to change where windows downloads it updates to: C:\ProgramData\Package Cache(in folders with long ID numbers).  When installing Python I found that it needs an update (). The Python installer goes ahead and tries to run the update but can fail with security errors unless run as admin - I don't want to have to run as admin, especially since I am installing to a non-system access area on D:\  So my question is, can I get windows to use a different folder so that I don't need to run with full admin rights?   for example: D:\myWindowsUpdates Finding the search terms behind 'not provided' We use Google Analytics to track the vistors to our websites, were currently putting together a big audit of our SEO and one of the things we want to see is what search terms are working for us.  About 90% of our organic search traffic comes under 'not provided' which as i understand means a user is signed into a Google account when coming to our site, thus Google doesn't track their search terms.   This makes it really hard to conduct a meaningful study, (i suppose we could get the data of the 10% that we do have search terms for and multiply them it but i dont think thats a particularly good or meaningful approach).  Is there a workaround to see behind the 'not provided' data and see the search terms actually used ?    UPDATE  I read  last night from Hacker news, which states :     [using https will allow you] more complete referrer information in Google Analytics for people   visiting from sites already using HTTPS   and contained a link to this , it seems to say that because Google's users are using https that an https site cannot pass data to an http site, as the http site is not secure, none of the sites i manage have https / sll setup, could some one confirm if Google will pass you more referrer data if your site has https implemented ? If $f: D(0,1)\to \mathbb C$ is holomorphic, then there is a sequence $\{z_n\}$ in $D(0,1)$ such that $|z_n| \to 1$ and $\{f(z_n)\}$ is bounded How is the amplitude of light related to number of photons? If you increase the number of photons leaving a light source you increase the brightness/intensity, so it could be said that intensity is directly proportional to number of photons. However intensity is directly proportional to amplitude squared, so this leads me to wonder that if you increase the amplitude of a light wave, are you just creating more photons rather than affecting each individual photon in some way? Orthographic scale of camera in Blender could somebody explain how orthographic scale is calculated in Blender? I am trying to match an orthographic view that I get from another software with that of Blender, but I am not able. Camera gets in the correct position but the zoom level is wrong.  Thanks, byte Review Count - Fix It or Lose It Asking the position of a person in a sequence How to ask the position(?) of a president (like 10th) of a country, correctly? For all infinite cardinals $\kappa, \ (\kappa \times \kappa, <_{cw}) \cong (\kappa, \in).$ I don't understand the proof to the a/m claim. How we know that $\eta &lt; \kappa$ and $(\alpha,\beta)&lt;_{cw} (0, \eta) $ and hence $h: \mu \to \eta \times \eta$ is injective? Appreciate if anyone could advise.  Here is an excerpt of the proof:  For an infinite ordinal $\kappa,$ the canonical well-ordering of $\kappa \times \kappa,$ denoted by $&lt;_{cw}$ is defined as follows: $(\alpha_1, \beta_1)&lt;_{cw} &lt; (\alpha_2, \beta_2)$ iff either one of the following holds.  $(1): \max\{\alpha_1,\beta_1\} &lt; \max\{\alpha_2,\beta_2\}$  $(2): \max\{\alpha_1,\beta_1\} =\max\{\alpha_2,\beta_2\}$ and $\alpha_1&lt;\alpha_2$   $(3): \max\{\alpha_1,\beta_1\} =\max\{\alpha_2,\beta_2\}$ and $\alpha_1 = \alpha_2$ and $\beta_1 &lt; \beta_2.$  Claim: For all infinite cardinals $\kappa, (\kappa \times \kappa, &lt;_{cw}) \cong (\kappa, \in).$  Proof: (It has been show that it is true for $\kappa = \omega$) Assume there is a counterexample  $\kappa.$ Let $A= \{\lambda \in \kappa + 1| \lambda\geq \omega \ is \ a \ cardinal \ and \ (\lambda \times \lambda, &lt;_{cw}) \not\cong (\lambda, \in)\}.$ Then, $\kappa \in A.$ Let $\mu$ be least element of $A.$ Thus, $\mu &gt; \omega$ and for all $\lambda,$ if $\omega \leq \lambda &lt; \mu$ and $\lambda$ is a cardinal, then $(\lambda \times \lambda, &lt;_{cw}) \cong (\lambda, \in).$  By Comparability theorem, $(\mu, \in)$ is isomorphic to initial segment of $(\mu \times \mu, &lt;_{cw})$ since $|\mu \times \mu| \geq \mu$ and $\mu$ is cardinal. Let $(\alpha, \beta) \in \mu \times \mu$ such that $(\mu, \in)$ is isomorphic to initial segment of $(\mu \times \mu, &lt;_{cw})$ given by $(\alpha, \beta).$ Let $h$ be the isomorphism. Let $\eta= \max\{\alpha, \beta\}+ \omega.$ Then $\eta &lt; \kappa$ and $(\alpha,\beta)&lt;_{cw} (0, \eta).$ HENCE, $h: \mu \to \eta \times \eta$ is injective. What's the best way to take a segment out of a text file? What is the acceptable similarity in a mathematics PhD dissertation when checking by Turnitin? I have checked the originality of my PhD thesis in mathematics using . The similarity was 31%. Is this percentage acceptable by most committees?