Evaluation of the maximum performance of block encryption algorithms

We study nonlinear transformations (similar to generalized Feistel networks) based on the shift register of length $n$ with $m$ feedbacks over the set $V_{32}$ of $32$-dimensional binary vectors, $32 \geqslant n > m \geqslant 1$. A new characteristic for evaluating the maximum encryption performance is proposed. These results may be used for justified choice of the parameters for block encryption algorithms.