Let $1$ be the all-one vector and $\odot$ denote the component-wise multiplication of two vectors in $\mathbb F_2^n$. We study the vector space $Γ_n$ over $\mathbb F_2$ generated by the functions $γ_{2k}:\mathbb F_2^n \to \mathbb F_2^n, k\geq 0$, where $$ γ_{2k} = S^{2k}\odot(1+S^{2k-1})\odot(1+S^{2k-3})\odot\ldots\odot(1+S) $$ and $S:\mathbb F_2^n\to\mathbb F_2^n$ is the cyclic left shift function. The functions in $Γ_n$ are shift-invariant and the well known $χ$ function used in several cryptographic primitives is contained in $Γ_n$. For even $n$, we show that the permutations from $Γ_n$ with respect to composition form an Abelian group, which is isomorphic to the unit group of the residue ring $\mathbb F_2[X]/(X^n +X^{n/2})$. This isomorphism yields an efficient theoretic and algorithmic method for constructing and studying a rich family of shift-invariant permutations on $\mathbb F_2^n$ which are natural generalizations of $χ$. To demonstrate it, we apply the obtained results to investigate the function $γ_0 +γ_2+γ_4$ on $\mathbb F_2^n$.