Is SHA-256 a one way permutation when restricting the domain to {0,1}^256?
Are common cryptographic hashes bijective when hashing a single block of the same size as the output?
Drop Table and recreate Permissions So we followed an best practice by Andreas de Ruiter ()  The Idea behind it is, that you write SQL Views which are easy to maintain and deploy. You use stored procedures to use these views and create tables from it. He suggests dropping or truncating the tables to maintain consistency over the data. I think it's the easiest approach without writing any complex update logic.  On these tables we have the need to set specific user permissions. By dropping the table we would lose them. So for us the question is, how could we drop the table and recreate the existing permissions on the newly created table? There does not exist any integer $m$ such that $3n^2+3n+7=m^3$ I have this really hard problem that I am working on and I just don't seem to get it. The question is: let $n$ be a positive integer; prove that there does not exist any integer $m$ such that $3n^2+3n+7=m^3$.  Please explain in detail otherwise I might not understand. I am also open for any methods that might help. Thank you. Please help. Using jQuery, how do I change the elements html value? (div) Using a ajax request I want to change content of my div.  &lt;div id="d1"&gt;202&lt;/div&gt;   So I want to change the content to a different number.  $('d1').InnerText???   Also, say I wanted to increment the number, how could I do that? Do I have to convert to int? After I saw that post i wanted to solve the first one which is $a\mid b^2,b^2\mid a^3,a^3\mid b^4,b^4\mid a^5\cdots$ Prove that $a=b$  Now i started by proving that $a$ and $b$ have same prime divisors,proving that is trivial,after doing so I checked do those factors have to have the same power.I tried with $$a=p^2,b=p^3$$ I noticed it exactly goes for 3 terms,or that $a^3\mid b^4$ doing $$a=p^{n-1},b=p^n\\p^{n-1}\mid p^{2n}\\p^{2n}\mid p^{3n-3}\\p^{3n-3}\mid p^{4n}\\p^{4n}\mid p^{5n-5}\\\cdots\\p^{n(n-1)}\mid p^{n(n-1)}\\p^{n(n-1)}\mid p^{n(n+1)}\\p^{n(n+1)}\not\mid p^{(n-1)(n+1)}$$ Now yeah I guess that would be a proof,but wouldn't setting $n=n+1$ infinitely many times make every term dividable? I've been looking for the name of a sci-fi romance book about space travel but haven't been successful so far. I came across it a few years ago, read the plot on its back cover but didn't read the book. It is about two spacecraft pilots, a man and a woman, who travelled at light speed (or maybe FTL, I can't remember) in separate ships. Every time they return to Earth, centuries have passed on Earth because of time dilation. They meet each other for a few times on Earth in different eras, but don't know when, if ever, they will meet again. I don't know how it ends.   If anyone knows which book I'm talking about, could you please tell me the name? Thanks a lot! Is it possible to install Steam games to two different locations? I want to build a new PC with a smallish SSD.  I'd like to be able to install some of my games onto the drive (those I care about loading quickly or I play frequently), but have the rest of them on a larger, slower drive.  Anybody know if this is possible?  I'm kind of guessing it's not, but figured I'd ask anyway. Explicit formula for Bernoulli numbers by using only the recurrence relation It is not hard to show, by induction on $m\in\mathbb N$, that there exist a sequence $(B_n)_{n\geq0}$ of rational numbers such that  $$\sum_{k=1}^nk^m=\frac1{m+1}\sum_{k=0}^m\binom{m+1}kB_k\,n^{m+1-k},\ \style{font-family:inherit;}{\text{for all}}\ n\geq1\,.$$  These are the Bernoulli numbers of the second kind, that is, $B_1=+1/2$. A corollary of the proof (by induction) of the fact above is a recurrence formula for such numbers $B_n$, which are known as Bernoulli numbers:  $$\sum_{k=0}^{n-1}\binom nkB_k=0\,.\tag{$\ast$}$$  On the other hand, there are a number of explicit formulae for $B_n$, which are obtained using the equality $\frac x{e^x-1}=\sum_{n=0}^\infty B_n\,\frac{x^n}{n!}$; see  and . For example:  $$B_n=\sum_{k=0}^n\frac1{k+1}\sum_{r=0}^k(-1)^r\binom krr^n\,.\tag{$\ast\ast$}$$  Is there some clever way to manipulate the recurrence $(\ast)$ in order to obtain $(\ast\ast)$? The class will be over in 10 minutes. The class will be over after 10 minutes.  I know the first is correct but why? Is it possible to add multiple materials to a text object? I know that for a mesh you can go into edit mode and select vertices and assign a specific material to them quite easily. I want to know if it is possible to do this with a Text object (which has no vertices). How to get the current time in Python Find the general solution of $y'= a^{x + y}$ where y is the function why __getitem__ cannot be classmethod? How to find a whole word in a String in java Lightsaber blade "weight" in-universe What makes a Feynman diagram real or virtual? Simple question: as the title says, what makes a real Feynman diagram real, and what makes a virtual diagram virtual? Or in other words, how do I tell whether any given diagram is real or virtual? I've never gotten a really satisfying explanation of this. I would imagine it has something to do with virtual particles, but all internal propagators are virtual particles and I know for a fact that having internal lines doesn't make a diagram virtual. How do you secure wood framing to a concrete basement floor? Trace map from finite surjective morphism of normal irreducible varieties Sum of points and rank according to points Why doesn't the Sun appear green to our eyes? Illustrator Vector Graphics Appearing Pixellated