Impossible Differential Cryptanalysis Of Several Block Ciphers

Cryptography is a core technology and an important cornerstone of information security based on mathematical theory.Block cipher,as an indispensable part of cryptography,has been widely used in the field of information security because of its fast conversion rate and easy implementation of software and hardware.The analysis of its security has subsequently become an important research direction.This thesis mainly conducts an impossible differential cryptanalysis and a research on the security of cryptographic algorithms that are still in use and have not been compromised in all rounds,in order to obtain the impossible differential attack results with lower complexity or more rounds and feasibility so that later improvers can learn some useful enlightenment from them.Several cryptographic algorithms with different iterative structure types are specifically studied,including:SPN structure classic block cipher ARIA cipher,SPN structure lightweight block cipher Robin cipher and Feistel structure lightweight block cipher PFP cipher.Through a more detailed impossible differential cryptanalysis,the complete attack steps and complexity calculation process are given for the several block cipher algorithms.Notice that early-abort technique was used in the recovery phase of the attack of the three cipher algorithms.The main research results are listed as follows:(1)Impossible differential cryptanalysis on ARIA cipher.The ARIA cipher was designed by Korean scholars in 2003 and was selected as the Korean encryption standard,which is a classic SPN block cipher.According to the method of Wang Xiangnan et al.,combined with the research of Xie Zuomin et al.,a new 4-round discriminator is given by using the structural characteristics of the ARIA-256 algorithm.Based on this discriminator,7-round of impossible differential analysis are performed.This attack requires about2¹¹¹ chosen plaintexts and2¹⁹⁵ 7-round of encryption.(2)Impossible differential cryptanalysis on Robin cipher.Robin cipher is a SPN structure lightweight block cipher algorithm designed by Grosso et al.in 2014 based on resistance to side channel analysis.In 2020,Shen Xuan et al.gave 4-round of impossible differential discriminators to achieve a total of 6-round of impossible differential attacks.According to the method of Wang Xiangnan et al.,combined with the research results of Shen Xuan et al.,a constraint condition is changed,and a property of this article is manually introduced and proved.According to the property,the linear relationship between the round keys is used to construct a new form of the differentiator,A new 4-round discriminator is given.Based on the differentiator,6-round of impossible differential analysis are performed,which reduces the number of selected plaintexts N,reducing2⁸ of the data complexity but increasing the time complexity.This attack requires about2^111.18chosen plaintexts and2^118.216-round of encryption.(3)Differential cryptanalysis on PFP cipher.The PFP cipher is a Feistel structure lightweight block cipher algorithm proposed by Huang Yuhua et al.in 2017.Based on the research of Shen Xuan et al.,a new 7-round impossible differential discriminator attack9-round PFP algorithm is constructed,which can recover the 28-bit seed key,and the time complexity is lower,while the data complexity is slightly increased.This attack requires about2^454.chosen plaintexts and2^403.9-round of encryption.