Paper 2025/403

Periodic Table of Cryptanalysis: Geometric Approach with Different Bases

Abstract

In the past three decades, we have witnessed the creation of various cryptanalytic attacks. However, relatively little research has been done on their potential underlying connections. The geometric approach, developed by Beyne in 2021, shows that a cipher can be viewed as a linear operation when we treat its input and output as points in an induced \textit{free vector space}. By performing a change of basis for the input and output spaces, one can obtain various transition matrices. Linear, differential, and (ultrametic) integral attacks have been well reinterpreted by Beyne's theory in a unified way. Thus far, the geometric approach always uses the same basis for the input and output spaces. We observe here that this restriction is unnecessary and allowing different bases makes the geometric approach more flexible and able to interpret/predict more attack types. Given some set of bases for the input and output spaces, a family of basis-based attacks is defined by combining them, and all attacks in this family can be studied in a unified automatic search method. We revisit three kinds of bases from previous geometric approach papers and extend them to four extra ones by introducing new rules when generating new bases. With the final seven bases, we can obtain $$ different basis-based attacks in the $$-th order spaces, where the \textit{order} is defined as the number of messages used in one sample during the attack. We then provide four examples of applications of this new framework. First, we show that by choosing a better pair of bases, Beyne and Verbauwhede's ultrametric integral cryptanalysis can be interpreted as a single element of a transition matrix rather than as a linear combination of elements. This unifies the ultrametric integral cryptanalysis with the previous linear and quasi-differential attacks. Second, we revisit the multiple-of-$$ property with our refined geometric approach and exhibit new multiple-of-$$ distinguishers that can reach more rounds of the \skinny-64 cipher than the state-of-the-art. Third, we study the multiple-of-$$ property for the first-order case, which is similar to the subspace trail but it is the divisibility property that is considered. This leads to a new distinguisher for 11-round-reduced \skinny-64. Finally, we give a closed formula for differential-linear approximations without any assumptions, even confirming that the two differential-linear approximations of \simeck-32 and \simeck-48 found by Hadipour \textit{et al.} are deterministic independently of concrete key values. We emphasize that all these applications were not possible before.