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Clash Royale CLAN TAG #URR8PPP up vote 2 down vote favorite I've just started learning about all of this and I can't really find an answer for that anywhere, namely why is SHA-256 not used for passwords? I found that the reason is that because normal SHA-256 is a fast function, and it's better to use slower ones, but here's the part i don't really get, from what i've read so far, SHA-256 produces a hash that'd take A LOT of years to crack, like A LOT A LOT, so why is it considered bad for passwords when it's basically impossible to crack? passwords cryptography hash sha256 share | improve this question asked 6 hours ago Wiktor Lobejko 11 1 New contributor Wiktor Lobejko is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct. security.stackexchange.com/questions/211/… – pm1391 3 hours ago Possible dupl

Clash Royale CLAN TAG #URR8PPP up vote 5 down vote favorite Background: I was trying to prove something having to do with cyclic group actions on matroids and was able to show that what I want holds if a particular elementary-looking number-theoretic property holds, but upon closer inspection it holds for some primes and not others and now I am wondering if this "elementary" problem is known/studied somewhere or perhaps it is an open problem--I have no idea since I only stumbled into it entirely accidentally. Even learning what area it should be considered, what potential tools there are for studying it, and what else it might be related to (even just keywords to search for!) would be helpful. The problem statement: Let $p$ be an odd prime and consider the permutation of the set $1,ldots,fracp-12$ defined by sending $n$ to $fracn2$ if $n$ is even and sending it to $fracp-n2$ if $n$ is odd. For which primes $p$ does this permutation have a single orbit?