The 128bit Block Cipher HyRAL (Hybrid Randomization Algorithm): Common Key Block Cipher

This paper proposes a improvement of a common key block cipher, HyRAL[1], which has 128bits block length and supports key length of 128, 192, and256bits. It has a 4way generalized Feistel Structure of 24 rounds for 128bits key length, and 32 rounds for 192, 256, bits key length. The rounds are consists of G1,F2,F1,G2 functions which have 4-round Feistel structure to make the cryptanalysis hard. We have evaluated its upper bounds of Maximum Differential (Linear) Characteristic Probability[2], and the cipher guarantee enough strength against Differential (Linear) attack. The round functions are composed of 8-bit s-box based on the inverse function on GF (2^8) a MDS matrix. round key XOR addition and byte oriented permutation.