Research On New Combinational Cryptanalysis Of SIMON-like Block Ciphers

Block cipher is the core cryptographic system for data encryption and authentication in information and network security,and is widely used in the field of information security.The security of a block cipher depends on its ability to resist known cryptanalysis techniques,such as differential cryptanalysis,linear cryptanalysis,integral cryptanalysis etc.In recent years,new cryptanalysis techniques such as rectangle cryptanalysis and rotational-XOR cryptanalysis have emerged to improve attacks on some block ciphers.Therefore,the research of new cryptanalysis is of great significance to the development and security evaluation of block ciphers.SIMON-like block ciphers are block ciphers with round function similar to SIMON,in-cluding SIMON and SIMECK.SIMON-like ciphers have outstanding hardware performance and have attracted many scholars to analyze them since they were proposed.For example,differential cryptanalysis and rotational-XOR cryptanalysis have good results on SIMON-like ciphers.This paper studies the rotational-XOR cryptanalysis,differential cryptanalysis and rect-angle cryptanalysis,and proposes a novel method called rotational-XOR differential rectangle attack to search for better distinguishers.It is a combination of the rotational-XOR cryptanal-ysis and differential cryptanalysis in the rectangle-based way.By choosing some appropriate rotational-XOR and differential characteristics as well as considering differential clustering ef-fect and multiple differentials,some longer rotational-XOR differential rectangle distinguishers that have the probability greater than 2^-2ncan be constructed effectively where n is the block size of a block cipher.We apply our new method to search for distinguishers for some versions of SIMON and SIMECK block ciphers.As a result,we find rotational-XOR differential rectangle distinguishers up to 16,16,and 17 rounds for SIMON32/64,SIMON48/72,and SIMON48/96,respectively.And we also find the 16 and 21 rounds distinguishers for SIMECK32 and SIMECK48.Our distinguishers for SIMON32/64 is longer than the best differential and rotational-XOR distin-guishers.As for SIMON48/96,distinguisher has same length as best differential distinguisher.Our distinguisher for SIMECK32 is longer than the best differential distinguisher（14 rounds）,and has the full weak key space(i.e.,2⁶⁴)whereas the 16-round rotational-XOR distinguisher has a weak key class of size 2³⁶.In addition,our distinguisher for SIMECK48 has a better weak key class(2⁷²weak keys)than the 21-round rotational-XOR distinguisher(2⁶⁰weak keys).This is the first time to consider the combinational cryptanalysis based on rotational-XOR and dif-ferential cryptanalysis using the rectangle structure.