Key Mixing in Block Ciphers through Addition modulo 2 n .
Debdeep Mukhopadhyay, Dipanwita Roy Chowdhury · 2005
Abstract. The classical technique to perform key mixing in block ciphers is through exclusive-or (exor). In this paper we show that when the n-bit key is mixed in a block cipher of size n bits via addition modulo 2n, the bias of the linear approximations falls exponentially fast. Experimental results have been provided to show that such a scheme cannot be cryptanalyzed using Linear Cryptanalysis. Keywords: Block Ciphers, Key Mixing, Linear Approximations, Piling-Up Lemma