Cryptographic Properties and Application of a Generalized Unbalanced Feistel Network Structure

Abstract. In this paper, we study GF-NLFSR, a Generalized Unbalanced Feistel Network (GUFN) which can be considered as an extension of the outer function FO of the KASUMI block cipher. We show that the differential and linear probabilities of any n + 1 rounds of an n-cell GF-NLFSR are both bounded by p2 , where the corresponding probability of the round function is p. Besides analyzing security against differential and linear cryptanalysis, we provide a frequency distribution for upper bounds on the true differential and linear hull probabilities. From the frequency distribution, we deduce that the proportion of input-output differences/mask values with probability bounded by pn is close to 1 whereas only a negligible proportion has probability bounded by p2 . We also recall an n2 -round integral attack distinguisher and (n2 + n − 2)-round impossible impossible differential distinguisher on the n-cell GF-NLFSR by Li et al. and Wu et al. As an application, we design a new 30-roun...

• Type: Conference
• Year: 2009
• Where: ACISP
• Authors: Jiali Choy, Guanhan Chew, Khoongming Khoo, Huihui Yap
• Keywords: ACISP 2009, Block Cipher, Impossible Differential Distinguisher, Integral Attack Distinguisher, Security Privacy