Given f:{0,1}n→{0,1}n, define f′:{0,1}2n→{0,1}2n as follows: for x,r∈{0,1}n define f′(x∘r):=f(x)∘r (where ∘ denotes concatenation). Prove that if f(⋅) is one way permutation then so is f′(⋅).
i don't understand f′(x∘r):=f(x)∘r how to decompose it in order to prove it
I tried proving it by...