Correlation distribution analysis of a two-round key-alternating block cipher L

Abstract

In this paper we study two-round key-alternating block ciphers with
round function 

$ f(x) = x^{(2^{t} +1)2s}   $;

where $t$; $s$ are positive integers.

An algorithm to computing the distribution weight in respect to input and output masks is described. Also, in the case 

$t = 1$ the correlation distributions in dependence on input and output masks are completely determined for arbitrary pairs of masks.