Podcast #128: We chat with Kent C Dodds about why he loves React and discuss what life was like in the dark days before Git. Listen now.

New answers tagged

6

This precise issue recently arose in light of suspicious patterns in the S-box of a Russian cipher Kuznyechik. See: Xavier Bonnetain and Léo Perrin and Shizhu Tian: Anomalies and Vector Space Search: Tools for S-Box Analysis, Asiacrypt 2019 One way the authors chose to quantify how unlikely such a permutation could have occurred by chance is to find the ...


26

There are at most $n \cdot (n - 1)$ permutations of $\mathbb Z/n\mathbb Z$ of the form $x \mapsto ax + b$: if $n$ is prime, there are $n - 1$ choices for $a$ and $n$ choices for $b$ under which this is a permutation. There are $n!$ permutations of $\mathbb Z/n\mathbb Z$ altogether. So the probability that a uniform random permutation has this form is ...


-2

Pseudorandom permutation Confusingly, nothing really gets permuted here in the classic definition of a permutation. It's more of a cryptographic twist on the common notion of permutation. The actual input/output behaviour is like:- And each input is mapped to exactly one output value. The above diagram is simplistic in that the size of the inputs and ...


1

You're close. As Mikero noted in the comments, this scheme is CCA-secure as proven in his book. The proof strategy that seems easiest here is to do game-hops and with the IND$-CPA definition: Start with the real case where $c=F_K(r\mathbin\|m)$ is returned Swap out $F_K(\cdot)$ for a random permutation $\pi$, so $c=\pi(r\mathbin\|m)$ is returned, you "lose"...


3

All three are families of functions. For example, $f_k(x) = k \oplus x$, where $\oplus$ is xor and $k$ and $x$ are 256-bit strings, is a family of functions; for any 256-bit string $k$, there is a function $f_k$ which given another 256-bit string $x$ returns the xor of $k$ and $x$. The input and output spaces need not be the same; we could imagine a family ...


Top 50 recent answers are included