Correlation Distribution Analysis of a Two-Round Key-Alternating Block Cipher

In this paper we study two-round key-alternating block ciphers with round function f (x)= x^(2t+1)2s, where t, s are positive integers. An algorithm to compute the distribution weight in respect to input and output masks is described. Also, in the case t = 1 the correlation distributions depending on input and output masks are completely determined for arbitrary pairs of masks.