Cryptanalysis Of Block Cipher NUX

Nowadays,people have been into information age.As a result,the security of information storage and transmission has become the very concerned issue,and the existence of cryptography provides a guarantee for the security of information.There's a very important part of cryptography,block cipher.Up to now,there are many important block ciphers designed,such as data encryption standard DES algorithm,advanced encryption standard AES algorithm and so on.However,people need to pay more attention to the security requirements of applications like IoT,RFID and WSN with the increasing popularity of intelligent devices.Since these devices have great limitations on the resources and environment which the original block ciphers can not satisfy,cryptographers have designed lightweight block ciphers for constraint environment,such as block cipher PRESENT,block cipher LED,etc.Block cipher NUX is a new lightweight block cipher proposed by Bansod et al.NUX cipher is based on generalized Feistel network and it has 31 rounds.It takes 64 bit plaintext and support 128/80 bits key length.Bansod et al gave the security analysis of NUX in the design document.They estimated the probability of differential trails for 25-round NUX to be 2-90,so they inferred complexity of the differential attack is 290 Besides,they estimated the total bias of linear trails for 25-round NUX to 2-66,and inferred that the required number of known plain text is 2132.In biclique attack on 31-round NUX,it comes out 224 data complexity and time complexity is 2127.10 31-round encryption.In this thesis,we find that there's no effect between the difference or linear mask of the left two branches and the right two branches in NUX during the transfer process.With this property we fix the difference or linear mask value of the two branches on the left or right to be 0 in order to reduce the number of active S-boxes in the searching algorithm,with which we obtain the diflferential and linear trails of 1-31 round NUX.For 25 round NUX,the best probability of differential trails is 2-71 and the maximum bias of linear trails is 2-41,which are better than those given by Bansod et al.For all 31 rounds,the differential probability can reach 2-88 and the total bias can reach 2-50.We use a 22-round differential trail with probability 2-58 attached with 7 rounds to complete the differential attack on 29 rounds of NUX.The time com-plexity is 2121.73 29-round encryption,data complexity is 261,storage complexity is 296 bytes;The linear attack on 25 rounds of NUX is accomplished by using a 19-round linear trail with bias 2-30 with 3 rounds before and 3 rounds after.The attack has a time complexity of 2126 25-round encryption,data complexity of 263.7 and storage complexity of 270 bytes.In addition,we find a distinguisher of 31-round NUX with probability 1 and exploit it to take distinguishing attack on 31-round NUX.The data complexity of this attack is 8,and time complexity is 8 full round encryption without storage complexity.