Saturation Atttack On Twofish And Differential Fault Attack On SIMON

Block cipher plays an extremely important role in the symmetric cryptography,block ciphers are needed in the field of information security.Block ciphers can be divided into three main structures: Feistel,SPN and Lai-Massey.This paper mainly studies two algorithms which belong to Feistel structures: Twofish algorithm and SIMON algorithm.We not only improve the saturation attack on Twofish algorithm,but also do the differential fault attack on SIMON algorithm.The main results are as follows:(1)For the Twofish algorithm,we mainly study the saturation properties of ARX systems.Three theorems related to the balance property are presented.Based on these properties the saturation distinguisher of Twofish can be improved.Compared with the best results,we can determine the balancedness of one more bit,so we can reduce half of the complexity of the attacks.(2)This paper gives the result of differential fault attack on SIMON,by using the differential properties of the nonlinear function of SIMON with probability analysis.Both the theoretical and experimental results demonstrate that under the random byte-oriented fault model,when faults are injected in the penultimate round,for SIMON32/64,if more than 24 random faults are used to recover all its 64-bit key,the success probability is more than 72%,if more than 40 random faults are used,the success probability is more than 98%,the remaining key space is about 224;for SIMON48/72,if more than 18 random faults are used to recover all its 72-bit key,the success probability is more than 65%,if more than 30 random faults are used,the success probability is more than 97%,and the remaining key space is about 224.Both the theoretical and experimental results demonstrate that under the random half byte-oriented fault model,when faults are injected in the antepenultimate round,for SIMON32/64,only two random faults can reduce the seed key space from 264 to 232~256,the average is 240.68.