I want to prove if the composite are equal to each other

[behzad_b]

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 using a composition of tow bijection, as a permutation is a sect of bijection function.

I am stuck on the proof, I don't know how to do the proof

 

[Fredrik]

What is the definition of {0,1}n?

 

[micromass]

Do you mean $\{0,1\}^n$?

What is a "one way" permutation?