Design And Analysis Of Two Types Of Block Cipher Algorithms With SPN Structures

With the resource-constrained IoT devices becoming more and more widely used,the design and cryptanalysis of lightweight block cipher algorithms are becoming research hotspots in cryptography.Specially,this paper mainly focuses on the lightweight cipher algorithms with SPN structure,which have the advantage of fast diffusion speed.The main work is as follows:(1)Inspired by PRESENT,a family of bit-based block cipher algorithms named ASD is proposed.The block size of ASD is 64 bits,and it supports key sizes of 80 and 128 bits,namely ASD-64-80 and ASD-64-128 respectively.The optimal S-box is used in the confusion layer while a simple linear bitwise operation with high diffusion performance is employed in the diffusion layer.Furthermore,automatic analysis methods are applied to conduct differential and linear analysis.Experimental results show that ASD has sufficient security to resist the above attacks.(2)We study the security of a class of nibble-based lightweight block cipher algorithms.More precisely:firstly,based on the structural characteristics of FUTURE and the properties of a type of truncated differential,a 4-round meet-in-the-middle distinguisher for the algorithm is constructed by using differential enumeration techniques;and then based on the distinguisher,after extending 1-round forward and 2-round backward respectively,the 7-round algorithm is attacked.Results show that during the preprocess phase,the time complexity is 244.7 times 7-round algorithm encryption,and the memory complexity is 249.9 bits.During the online attack phase,the data complexity is 216 chosen plaintexts,and the time complexity 236.4 times 7-round algorithm encryptions.Secondly,with the similar idea,a 4-round meet-in-the-middle distinguisher for KLEIN-64 is constructed,and then after extending 2-round forward and backward respectively,the 8-round algorithm is attacked.Results show that during the preprocess phase,the time complexity is 244.5 times 8-round algorithm encryptions,and the memory complexity is 249.9 bits.During the online attack phase,the data complexity is 232 chosen plaintexts,and the time complexity is 297.6 times 8-round algorithm encryption.In conclusion,both of the algorithms have sufficient security to resist meet-in-the-middle attacks.